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Anatomy_Gray_900	Anatomy_Gray	to visualize either the bile duct (cholangiogram) or pancreatic duct (pancreatogram) (Fig. 4.119). If a stone is present, it can be removed with a stone basket or an extraction balloon. Usually, a sphincterotomy is performed before stone removal to ease its passage through the distal bile duct.	Anatomy_Gray. to visualize either the bile duct (cholangiogram) or pancreatic duct (pancreatogram) (Fig. 4.119). If a stone is present, it can be removed with a stone basket or an extraction balloon. Usually, a sphincterotomy is performed before stone removal to ease its passage through the distal bile duct.
Anatomy_Gray_901	Anatomy_Gray	In cases of biliary tree obstruction caused by benign or malignant strictures, a stent can be placed into the common bile duct or into one of the main hepatic ducts to allow opening of the narrowed segment. The patency of the newly inserted stent is confirmed by instillation of more contrast medium to demonstrate free flow of contrast through the stent. In the clinic Jaundice is a yellow discoloration of the skin caused by excess bile pigment (bilirubin) within the plasma. The yellow color is best appreciated by looking at the normally white sclerae of the eyes, which turn yellow. The extent of the elevation of the bile pigments and the duration for which they have been elevated account for the severity of jaundice. Simplified explanation to understanding the types of jaundice and their anatomical causes	Anatomy_Gray. In cases of biliary tree obstruction caused by benign or malignant strictures, a stent can be placed into the common bile duct or into one of the main hepatic ducts to allow opening of the narrowed segment. The patency of the newly inserted stent is confirmed by instillation of more contrast medium to demonstrate free flow of contrast through the stent. In the clinic Jaundice is a yellow discoloration of the skin caused by excess bile pigment (bilirubin) within the plasma. The yellow color is best appreciated by looking at the normally white sclerae of the eyes, which turn yellow. The extent of the elevation of the bile pigments and the duration for which they have been elevated account for the severity of jaundice. Simplified explanation to understanding the types of jaundice and their anatomical causes
Anatomy_Gray_902	Anatomy_Gray	Simplified explanation to understanding the types of jaundice and their anatomical causes When red blood cells are destroyed by the reticuloendothelial system, the iron from the hemoglobin molecule is recycled, whereas the porphyrin ring (globin) compounds are broken down to form fat-soluble bilirubin. On reaching the liver via the bloodstream, the fat-soluble bilirubin is converted to a water-soluble form of bilirubin. This water-soluble bilirubin is secreted into the biliary tree and then in turn into the bowel, where it forms the dark color of the stool. This type of jaundice is usually produced by conditions where there is an excessive breakdown of red blood cells (e.g., in incompatible blood transfusion and hemolytic anemia).	Anatomy_Gray. Simplified explanation to understanding the types of jaundice and their anatomical causes When red blood cells are destroyed by the reticuloendothelial system, the iron from the hemoglobin molecule is recycled, whereas the porphyrin ring (globin) compounds are broken down to form fat-soluble bilirubin. On reaching the liver via the bloodstream, the fat-soluble bilirubin is converted to a water-soluble form of bilirubin. This water-soluble bilirubin is secreted into the biliary tree and then in turn into the bowel, where it forms the dark color of the stool. This type of jaundice is usually produced by conditions where there is an excessive breakdown of red blood cells (e.g., in incompatible blood transfusion and hemolytic anemia).
Anatomy_Gray_903	Anatomy_Gray	This type of jaundice is usually produced by conditions where there is an excessive breakdown of red blood cells (e.g., in incompatible blood transfusion and hemolytic anemia). The complex biochemical reactions for converting fat-soluble into water-soluble bilirubin may be affected by inflammatory change within the liver (e.g., from hepatitis or chronic liver disease, such as liver cirrhosis) and poisons (e.g., paracetamol overdose). Any obstruction of the biliary tree can produce jaundice, but the two most common causes are gallstones within the bile duct and an obstructing tumor at the head of the pancreas. In the clinic From a clinical point of view, there are two main categories of spleen disorders: rupture and enlargement.	Anatomy_Gray. This type of jaundice is usually produced by conditions where there is an excessive breakdown of red blood cells (e.g., in incompatible blood transfusion and hemolytic anemia). The complex biochemical reactions for converting fat-soluble into water-soluble bilirubin may be affected by inflammatory change within the liver (e.g., from hepatitis or chronic liver disease, such as liver cirrhosis) and poisons (e.g., paracetamol overdose). Any obstruction of the biliary tree can produce jaundice, but the two most common causes are gallstones within the bile duct and an obstructing tumor at the head of the pancreas. In the clinic From a clinical point of view, there are two main categories of spleen disorders: rupture and enlargement.
Anatomy_Gray_904	Anatomy_Gray	In the clinic From a clinical point of view, there are two main categories of spleen disorders: rupture and enlargement. This tends to occur when there is localized trauma to the left upper quadrant. It may be associated with left lower rib fractures. Because the spleen has such an extremely thin capsule, it is susceptible to injury even when there is no damage to surrounding structures, and because the spleen is highly vascular, when ruptured, it bleeds profusely into the peritoneal cavity. Splenic rupture should always be suspected with blunt abdominal injury. Current treatments preserve as much of the spleen as possible, but some patients require splenectomy.	Anatomy_Gray. In the clinic From a clinical point of view, there are two main categories of spleen disorders: rupture and enlargement. This tends to occur when there is localized trauma to the left upper quadrant. It may be associated with left lower rib fractures. Because the spleen has such an extremely thin capsule, it is susceptible to injury even when there is no damage to surrounding structures, and because the spleen is highly vascular, when ruptured, it bleeds profusely into the peritoneal cavity. Splenic rupture should always be suspected with blunt abdominal injury. Current treatments preserve as much of the spleen as possible, but some patients require splenectomy.
Anatomy_Gray_905	Anatomy_Gray	The spleen is an organ of the reticuloendothelial system involved in hematopoiesis and immunological surveillance. Diseases that affect the reticuloendothelial system (e.g., leukemia or lymphoma) may produce generalized lymphadenopathy and enlargement of the spleen (splenomegaly) (Fig. 4.120). The spleen often enlarges when performing its normal physiological functions, such as when clearing microorganisms and particulates from the circulation, producing increased antibodies in the course of sepsis, or removing deficient or destroyed erythrocytes (e.g., in thalassemia and spherocytosis). Splenomegaly may also be a result of increased venous pressure caused by congestive heart failure, splenic vein thrombosis, or portal hypertension. An enlarged spleen is prone to rupture. In the clinic Vascular supply to the gastrointestinal system	Anatomy_Gray. The spleen is an organ of the reticuloendothelial system involved in hematopoiesis and immunological surveillance. Diseases that affect the reticuloendothelial system (e.g., leukemia or lymphoma) may produce generalized lymphadenopathy and enlargement of the spleen (splenomegaly) (Fig. 4.120). The spleen often enlarges when performing its normal physiological functions, such as when clearing microorganisms and particulates from the circulation, producing increased antibodies in the course of sepsis, or removing deficient or destroyed erythrocytes (e.g., in thalassemia and spherocytosis). Splenomegaly may also be a result of increased venous pressure caused by congestive heart failure, splenic vein thrombosis, or portal hypertension. An enlarged spleen is prone to rupture. In the clinic Vascular supply to the gastrointestinal system
Anatomy_Gray_906	Anatomy_Gray	In the clinic Vascular supply to the gastrointestinal system The abdominal parts of the gastrointestinal system are supplied mainly by the celiac trunk and the superior mesenteric and inferior mesenteric arteries (Fig. 4.129): The celiac trunk supplies the lower esophagus, stomach, superior part of the duodenum, and proximal half of the descending part of the duodenum. The superior mesenteric artery supplies the rest of the duodenum, the jejunum, the ileum, the ascending colon, and the proximal two-thirds of the transverse colon. The inferior mesenteric artery supplies the rest of the transverse colon, the descending colon, the sigmoid colon, and most of the rectum.	Anatomy_Gray. In the clinic Vascular supply to the gastrointestinal system The abdominal parts of the gastrointestinal system are supplied mainly by the celiac trunk and the superior mesenteric and inferior mesenteric arteries (Fig. 4.129): The celiac trunk supplies the lower esophagus, stomach, superior part of the duodenum, and proximal half of the descending part of the duodenum. The superior mesenteric artery supplies the rest of the duodenum, the jejunum, the ileum, the ascending colon, and the proximal two-thirds of the transverse colon. The inferior mesenteric artery supplies the rest of the transverse colon, the descending colon, the sigmoid colon, and most of the rectum.
Anatomy_Gray_907	Anatomy_Gray	The inferior mesenteric artery supplies the rest of the transverse colon, the descending colon, the sigmoid colon, and most of the rectum. Along the descending part of the duodenum there is a potential watershed area between the celiac trunk blood supply and the superior mesenteric arterial blood supply. It is unusual for this area to become ischemic, whereas the watershed area between the superior mesenteric artery and the inferior mesenteric artery, at the splenic flexure, is extremely vulnerable to ischemia. In certain disease states, the region of the splenic flexure of the colon can become ischemic. When this occurs, the mucosa sloughs off, rendering the patient susceptible to infection and perforation of the large bowel, which then requires urgent surgical attention.	Anatomy_Gray. The inferior mesenteric artery supplies the rest of the transverse colon, the descending colon, the sigmoid colon, and most of the rectum. Along the descending part of the duodenum there is a potential watershed area between the celiac trunk blood supply and the superior mesenteric arterial blood supply. It is unusual for this area to become ischemic, whereas the watershed area between the superior mesenteric artery and the inferior mesenteric artery, at the splenic flexure, is extremely vulnerable to ischemia. In certain disease states, the region of the splenic flexure of the colon can become ischemic. When this occurs, the mucosa sloughs off, rendering the patient susceptible to infection and perforation of the large bowel, which then requires urgent surgical attention.
Anatomy_Gray_908	Anatomy_Gray	Arteriosclerosis may occur throughout the abdominal aorta and at the openings of the celiac trunk and the superior mesenteric and inferior mesenteric arteries. Not infrequently, the inferior mesenteric artery becomes occluded. Interestingly, many of these patients do not suffer any complications, because anastomoses between the right, middle, and left colic arteries gradually enlarge, forming a continuous marginal artery. The distal large bowel therefore becomes supplied by this enlarged marginal artery (marginal artery of Drummond), which replaces the blood supply of the inferior mesenteric artery (Fig. 4.130).	Anatomy_Gray. Arteriosclerosis may occur throughout the abdominal aorta and at the openings of the celiac trunk and the superior mesenteric and inferior mesenteric arteries. Not infrequently, the inferior mesenteric artery becomes occluded. Interestingly, many of these patients do not suffer any complications, because anastomoses between the right, middle, and left colic arteries gradually enlarge, forming a continuous marginal artery. The distal large bowel therefore becomes supplied by this enlarged marginal artery (marginal artery of Drummond), which replaces the blood supply of the inferior mesenteric artery (Fig. 4.130).
Anatomy_Gray_909	Anatomy_Gray	If the openings of the celiac trunk and superior mesenteric artery become narrowed, the blood supply to the gut is diminished. After a heavy meal, the oxygen demand of the bowel therefore outstrips the limited supply of blood through the stenosed vessels, resulting in severe pain and discomfort (mesenteric angina). Patients with this condition tend not to eat because of the pain and rapidly lose weight. The diagnosis is determined by aortic angiography, and the stenoses of the celiac trunk and superior mesenteric artery are best appreciated in the lateral view. In the clinic Cirrhosis is a complex disorder of the liver, the diagnosis of which is confirmed histologically. When a diagnosis is suspected, a liver biopsy is necessary. Cirrhosis is characterized by widespread hepatic fibrosis interspersed with areas of nodular regeneration and abnormal reconstruction of preexisting lobular architecture. The presence of cirrhosis implies previous or continuing liver cell damage.	Anatomy_Gray. If the openings of the celiac trunk and superior mesenteric artery become narrowed, the blood supply to the gut is diminished. After a heavy meal, the oxygen demand of the bowel therefore outstrips the limited supply of blood through the stenosed vessels, resulting in severe pain and discomfort (mesenteric angina). Patients with this condition tend not to eat because of the pain and rapidly lose weight. The diagnosis is determined by aortic angiography, and the stenoses of the celiac trunk and superior mesenteric artery are best appreciated in the lateral view. In the clinic Cirrhosis is a complex disorder of the liver, the diagnosis of which is confirmed histologically. When a diagnosis is suspected, a liver biopsy is necessary. Cirrhosis is characterized by widespread hepatic fibrosis interspersed with areas of nodular regeneration and abnormal reconstruction of preexisting lobular architecture. The presence of cirrhosis implies previous or continuing liver cell damage.
Anatomy_Gray_910	Anatomy_Gray	The etiology of cirrhosis is complex and includes toxins (alcohol), viral inflammation, biliary obstruction, vascular outlet obstruction, nutritional (malnutrition) causes, and inherited anatomical and metabolic disorders. As the cirrhosis progresses, the intrahepatic vasculature is distorted, which in turn leads to increased pressure in the portal vein and its draining tributaries (portal hypertension). Portal hypertension produces increased pressure in the splenic venules, leading to splenic enlargement. At the sites of portosystemic anastomosis (see below), large dilated veins (varices) develop. These veins are susceptible to bleeding and may produce marked blood loss, which in some instances can be fatal.	Anatomy_Gray. The etiology of cirrhosis is complex and includes toxins (alcohol), viral inflammation, biliary obstruction, vascular outlet obstruction, nutritional (malnutrition) causes, and inherited anatomical and metabolic disorders. As the cirrhosis progresses, the intrahepatic vasculature is distorted, which in turn leads to increased pressure in the portal vein and its draining tributaries (portal hypertension). Portal hypertension produces increased pressure in the splenic venules, leading to splenic enlargement. At the sites of portosystemic anastomosis (see below), large dilated veins (varices) develop. These veins are susceptible to bleeding and may produce marked blood loss, which in some instances can be fatal.
Anatomy_Gray_911	Anatomy_Gray	The liver is responsible for the production of numerous proteins, including those of the clotting cascade. Any disorder of the liver (including infection and cirrhosis) may decrease the production of these proteins and so prevent adequate blood clotting. Patients with severe cirrhosis of the liver have a significant risk of serious bleeding, even from small cuts; in addition, when varices rupture, there is a danger of rapid exsanguination. As the liver progressively fails, the patient develops salt and water retention, which produces skin and subcutaneous edema. Fluid (ascites) is also retained in the peritoneal cavity, which can hold many liters. The poorly functioning liver cells (hepatocytes) are unable to break down blood and blood products, leading to an increase in the serum bilirubin level, which manifests as jaundice.	Anatomy_Gray. The liver is responsible for the production of numerous proteins, including those of the clotting cascade. Any disorder of the liver (including infection and cirrhosis) may decrease the production of these proteins and so prevent adequate blood clotting. Patients with severe cirrhosis of the liver have a significant risk of serious bleeding, even from small cuts; in addition, when varices rupture, there is a danger of rapid exsanguination. As the liver progressively fails, the patient develops salt and water retention, which produces skin and subcutaneous edema. Fluid (ascites) is also retained in the peritoneal cavity, which can hold many liters. The poorly functioning liver cells (hepatocytes) are unable to break down blood and blood products, leading to an increase in the serum bilirubin level, which manifests as jaundice.
Anatomy_Gray_912	Anatomy_Gray	The poorly functioning liver cells (hepatocytes) are unable to break down blood and blood products, leading to an increase in the serum bilirubin level, which manifests as jaundice. With the failure of normal liver metabolism, toxic metabolic by-products do not convert to nontoxic metabolites. This buildup of noxious compounds is made worse by the numerous portosystemic shunts, which allow the toxic metabolites to bypass the liver. Patients may develop severe neurological features, called hepatic encephalopathy, that can manifest as acute confusion, epileptic fits, or psychotic state. Hepatic encephalopathy is one of the urgent criteria for liver transplantation; if the condition is not reversed, it leads to irreversible neurological damage and death.	Anatomy_Gray. The poorly functioning liver cells (hepatocytes) are unable to break down blood and blood products, leading to an increase in the serum bilirubin level, which manifests as jaundice. With the failure of normal liver metabolism, toxic metabolic by-products do not convert to nontoxic metabolites. This buildup of noxious compounds is made worse by the numerous portosystemic shunts, which allow the toxic metabolites to bypass the liver. Patients may develop severe neurological features, called hepatic encephalopathy, that can manifest as acute confusion, epileptic fits, or psychotic state. Hepatic encephalopathy is one of the urgent criteria for liver transplantation; if the condition is not reversed, it leads to irreversible neurological damage and death.
Anatomy_Gray_913	Anatomy_Gray	The hepatic portal system drains blood from the visceral organs of the abdomen to the liver. In normal individuals, 100% of the portal venous blood flow can be recovered from the hepatic veins, whereas in patients with elevated portal vein pressure (e.g., from cirrhosis), there is significantly less blood flow to the liver. The rest of the blood enters collateral channels, which drain into the systemic circulation at specific points (Fig. 4.133). The largest of these collaterals occur at: the gastroesophageal junction around the cardia of the stomach—where the left gastric vein and its tributaries form a portosystemic anastomosis with tributaries to the azygos system of veins of the caval system; the anus—the superior rectal vein of the portal system anastomoses with the middle and inferior rectal veins of the systemic venous system; and the anterior abdominal wall around the umbilicus—the para-umbilical veins anastomose with veins on the anterior abdominal wall.	Anatomy_Gray. The hepatic portal system drains blood from the visceral organs of the abdomen to the liver. In normal individuals, 100% of the portal venous blood flow can be recovered from the hepatic veins, whereas in patients with elevated portal vein pressure (e.g., from cirrhosis), there is significantly less blood flow to the liver. The rest of the blood enters collateral channels, which drain into the systemic circulation at specific points (Fig. 4.133). The largest of these collaterals occur at: the gastroesophageal junction around the cardia of the stomach—where the left gastric vein and its tributaries form a portosystemic anastomosis with tributaries to the azygos system of veins of the caval system; the anus—the superior rectal vein of the portal system anastomoses with the middle and inferior rectal veins of the systemic venous system; and the anterior abdominal wall around the umbilicus—the para-umbilical veins anastomose with veins on the anterior abdominal wall.
Anatomy_Gray_914	Anatomy_Gray	When the pressure in the portal vein is elevated, venous enlargement (varices) tend to occur at and around the sites of portosystemic anastomoses and these enlarged veins are called: varices at the anorectal junction, esophageal varices at the gastroesophageal junction, and caput medusae at the umbilicus. Esophageal varices are susceptible to trauma and, once damaged, may bleed profusely, requiring urgent surgical intervention. In the clinic	Anatomy_Gray. When the pressure in the portal vein is elevated, venous enlargement (varices) tend to occur at and around the sites of portosystemic anastomoses and these enlarged veins are called: varices at the anorectal junction, esophageal varices at the gastroesophageal junction, and caput medusae at the umbilicus. Esophageal varices are susceptible to trauma and, once damaged, may bleed profusely, requiring urgent surgical intervention. In the clinic
Anatomy_Gray_915	Anatomy_Gray	Esophageal varices are susceptible to trauma and, once damaged, may bleed profusely, requiring urgent surgical intervention. In the clinic Surgery for obesity is also known as weight loss surgery and bariatric surgery. This type of surgery has become increasingly popular over the last few years for patients who are unable to achieve significant weight loss through appropriate diet modification and exercise programs. It is often regarded as a last resort. Importantly, we have to recognize the increasing medical impact that overweight patients pose. With obesity the patient is more likely to develop diabetes and cardiovascular problems and may suffer from increased general health disorders. All of these have a significant impact on health care budgeting and are regarded as serious conditions for the “health of a nation.”	Anatomy_Gray. Esophageal varices are susceptible to trauma and, once damaged, may bleed profusely, requiring urgent surgical intervention. In the clinic Surgery for obesity is also known as weight loss surgery and bariatric surgery. This type of surgery has become increasingly popular over the last few years for patients who are unable to achieve significant weight loss through appropriate diet modification and exercise programs. It is often regarded as a last resort. Importantly, we have to recognize the increasing medical impact that overweight patients pose. With obesity the patient is more likely to develop diabetes and cardiovascular problems and may suffer from increased general health disorders. All of these have a significant impact on health care budgeting and are regarded as serious conditions for the “health of a nation.”
Anatomy_Gray_916	Anatomy_Gray	There are a number of surgical options to treat obesity. Surgery for patients who are morbidly obese can be categorized into two main groups: malabsorptive procedures and restrictive procedures. There are a variety of bypass procedures that produce a malabsorption state, preventing further weight gain and also producing weight loss. There are complications, which may include anemia, osteoporosis, and diarrhea (e.g., jejunoileal bypass). Restrictive procedures involve placing a band or stapling in or around the stomach to decrease the size of the organ. This reduction produces an earlier feeling of satiety and prevents the patient from overeating. Probably the most popular procedure currently in the United States is gastric bypass surgery. This procedure involves stapling the proximal stomach and joining a loop of small bowel to the small gastric remnant. The procedure is usually performed by fashioning a Roux-en-Y loop with alimentary and pancreaticobiliary limbs.	Anatomy_Gray. There are a number of surgical options to treat obesity. Surgery for patients who are morbidly obese can be categorized into two main groups: malabsorptive procedures and restrictive procedures. There are a variety of bypass procedures that produce a malabsorption state, preventing further weight gain and also producing weight loss. There are complications, which may include anemia, osteoporosis, and diarrhea (e.g., jejunoileal bypass). Restrictive procedures involve placing a band or stapling in or around the stomach to decrease the size of the organ. This reduction produces an earlier feeling of satiety and prevents the patient from overeating. Probably the most popular procedure currently in the United States is gastric bypass surgery. This procedure involves stapling the proximal stomach and joining a loop of small bowel to the small gastric remnant. The procedure is usually performed by fashioning a Roux-en-Y loop with alimentary and pancreaticobiliary limbs.
Anatomy_Gray_917	Anatomy_Gray	The other type of the procedure, sleeve gastrectomy, is increasing in popularity because it can be used in patients deemed to be at high risk for gastric bypass surgery. It involves reduction of the gastric lumen by removing a large portion of the stomach along the greater curvature. Any overweight patient undergoing surgery faces significant risk and increased morbidity, with mortality rates from 1% to 5%. In the clinic	Anatomy_Gray. The other type of the procedure, sleeve gastrectomy, is increasing in popularity because it can be used in patients deemed to be at high risk for gastric bypass surgery. It involves reduction of the gastric lumen by removing a large portion of the stomach along the greater curvature. Any overweight patient undergoing surgery faces significant risk and increased morbidity, with mortality rates from 1% to 5%. In the clinic
Anatomy_Gray_918	Anatomy_Gray	Any overweight patient undergoing surgery faces significant risk and increased morbidity, with mortality rates from 1% to 5%. In the clinic At first glance, it is difficult to appreciate why the psoas muscle sheath is of greater importance than any other muscle sheath. The psoas muscle and its sheath arise not only from the lumbar vertebrae but also from the intervertebral discs between each vertebra. This disc origin is of critical importance. In certain types of infection, the intervertebral disc is preferentially affected (e.g., tuberculosis and salmonella discitis). As the infection of the disc develops, the infection spreads anteriorly and anterolaterally. In the anterolateral position, the infection passes into the psoas muscle sheath, and spreads within the muscle and sheath, and may appear below the inguinal ligament as a mass. In the clinic To understand why a hernia occurs through the diaphragm, it is necessary to consider the embryology of the diaphragm.	Anatomy_Gray. Any overweight patient undergoing surgery faces significant risk and increased morbidity, with mortality rates from 1% to 5%. In the clinic At first glance, it is difficult to appreciate why the psoas muscle sheath is of greater importance than any other muscle sheath. The psoas muscle and its sheath arise not only from the lumbar vertebrae but also from the intervertebral discs between each vertebra. This disc origin is of critical importance. In certain types of infection, the intervertebral disc is preferentially affected (e.g., tuberculosis and salmonella discitis). As the infection of the disc develops, the infection spreads anteriorly and anterolaterally. In the anterolateral position, the infection passes into the psoas muscle sheath, and spreads within the muscle and sheath, and may appear below the inguinal ligament as a mass. In the clinic To understand why a hernia occurs through the diaphragm, it is necessary to consider the embryology of the diaphragm.
Anatomy_Gray_919	Anatomy_Gray	In the clinic To understand why a hernia occurs through the diaphragm, it is necessary to consider the embryology of the diaphragm. The diaphragm is formed from four structures— the septum transversum, the posterior esophageal mesentery, the pleuroperitoneal membrane, and the peripheral rim—which eventually fuse together, separating the abdominal cavity from the thoracic cavity. The septum transversum forms the central tendon, which develops from a mesodermal origin superior to the embryo’s head and then moves to its more adult position during folding of the cephalic portion of the embryo. Fusion of the various components of the diaphragm may fail, and hernias may occur through the failed points of fusion (Fig. 4.146). The commonest sites are: between the xiphoid process and the costal margins on the right (Morgagni’s hernia), and through an opening on the left when the pleuroperitoneal membrane fails to close the pericardioperitoneal canal (Bochdalek’s hernia).	Anatomy_Gray. In the clinic To understand why a hernia occurs through the diaphragm, it is necessary to consider the embryology of the diaphragm. The diaphragm is formed from four structures— the septum transversum, the posterior esophageal mesentery, the pleuroperitoneal membrane, and the peripheral rim—which eventually fuse together, separating the abdominal cavity from the thoracic cavity. The septum transversum forms the central tendon, which develops from a mesodermal origin superior to the embryo’s head and then moves to its more adult position during folding of the cephalic portion of the embryo. Fusion of the various components of the diaphragm may fail, and hernias may occur through the failed points of fusion (Fig. 4.146). The commonest sites are: between the xiphoid process and the costal margins on the right (Morgagni’s hernia), and through an opening on the left when the pleuroperitoneal membrane fails to close the pericardioperitoneal canal (Bochdalek’s hernia).
Anatomy_Gray_920	Anatomy_Gray	Hernias may also occur through the central tendon and through a congenitally large esophageal hiatus. Morgagni’s and Bochdalek’s hernias tend to appear at or around the time of birth or in early infancy. They allow abdominal bowel to enter the thoracic cavity, which may compress the lungs and reduce respiratory function. Most of these hernias require surgical closure of the diaphragmatic defect. However, large hernias can lead to pulmonary hypoplasia and the long-term outcome depends more on the degree of the hypoplasia rather than on the surgical repair itself. Occasionally, small defects within the diaphragm fail to permit bowel through, but do allow free movement of fluid. Patients with ascites may develop pleural effusions, while patients with pleural effusions may develop ascites when these defects are present. In the clinic	Anatomy_Gray. Hernias may also occur through the central tendon and through a congenitally large esophageal hiatus. Morgagni’s and Bochdalek’s hernias tend to appear at or around the time of birth or in early infancy. They allow abdominal bowel to enter the thoracic cavity, which may compress the lungs and reduce respiratory function. Most of these hernias require surgical closure of the diaphragmatic defect. However, large hernias can lead to pulmonary hypoplasia and the long-term outcome depends more on the degree of the hypoplasia rather than on the surgical repair itself. Occasionally, small defects within the diaphragm fail to permit bowel through, but do allow free movement of fluid. Patients with ascites may develop pleural effusions, while patients with pleural effusions may develop ascites when these defects are present. In the clinic
Anatomy_Gray_921	Anatomy_Gray	In the clinic At the level of the esophageal hiatus, the diaphragm may be lax, allowing the fundus of the stomach to herniate into the posterior mediastinum (Figs. 4.147 and 4.148). This typically causes symptoms of acid reflux. Ulceration may occur and may produce bleeding and anemia. The diagnosis is usually made by barium studies or endoscopy. Hiatal hernia is often asymptomatic and is frequently found incidentally on CT imaging performed for unrelated complaints. Treatment in the first instance is by medical management, although surgery may be necessary. In the clinic	Anatomy_Gray. In the clinic At the level of the esophageal hiatus, the diaphragm may be lax, allowing the fundus of the stomach to herniate into the posterior mediastinum (Figs. 4.147 and 4.148). This typically causes symptoms of acid reflux. Ulceration may occur and may produce bleeding and anemia. The diagnosis is usually made by barium studies or endoscopy. Hiatal hernia is often asymptomatic and is frequently found incidentally on CT imaging performed for unrelated complaints. Treatment in the first instance is by medical management, although surgery may be necessary. In the clinic
Anatomy_Gray_922	Anatomy_Gray	In the clinic Urinary tract stones (calculi) occur more frequently in men than in women, are most common in people aged between 20 and 60 years, and are usually associated with sedentary lifestyles. The stones are polycrystalline aggregates of calcium, phosphate, oxalate, urate, and other soluble salts within an organic matrix. The urine becomes saturated with these salts, and small variations in the pH cause the salts to precipitate. Typically the patient has pain that radiates from the infrascapular region (loin) into the groin, and even into the scrotum or labia majora. Blood in the urine (hematuria) may also be noticed. Infection must be excluded because certain species of bacteria are commonly associated with urinary tract stones. The complications of urinary tract stones include infection, urinary obstruction, and renal failure. Stones may also develop within the bladder and produce marked irritation, causing pain and discomfort.	Anatomy_Gray. In the clinic Urinary tract stones (calculi) occur more frequently in men than in women, are most common in people aged between 20 and 60 years, and are usually associated with sedentary lifestyles. The stones are polycrystalline aggregates of calcium, phosphate, oxalate, urate, and other soluble salts within an organic matrix. The urine becomes saturated with these salts, and small variations in the pH cause the salts to precipitate. Typically the patient has pain that radiates from the infrascapular region (loin) into the groin, and even into the scrotum or labia majora. Blood in the urine (hematuria) may also be noticed. Infection must be excluded because certain species of bacteria are commonly associated with urinary tract stones. The complications of urinary tract stones include infection, urinary obstruction, and renal failure. Stones may also develop within the bladder and produce marked irritation, causing pain and discomfort.
Anatomy_Gray_923	Anatomy_Gray	The diagnosis of urinary tract stones is based upon history and examination. Stones are often visible on abdominal radiographs. Special investigations include: ultrasound scanning, which may demonstrate the dilated renal pelvis and calices when the urinary system is obstructed. This is the preferred way of imaging in pregnant women or when clinical suspicion is low. low-dose CT of the urinary tract (CT KUB), which allows the detection of even smaller stones, shows the exact level of obstruction and, based on the size, density, and location of the stone, can help the urologist plan a procedure to remove the stone if necessary (extracorporeal shock wave lithotripsy versus ureteroscopy, percutaneous nephrolithotomy, or, extremely rare these days, open surgery) (Fig. 4.156). an intravenous urogram, which will demonstrate the obstruction, pinpoint the exact level of the stone is currently less often used because access to low-dose CT KUB has increased. In the clinic	Anatomy_Gray. The diagnosis of urinary tract stones is based upon history and examination. Stones are often visible on abdominal radiographs. Special investigations include: ultrasound scanning, which may demonstrate the dilated renal pelvis and calices when the urinary system is obstructed. This is the preferred way of imaging in pregnant women or when clinical suspicion is low. low-dose CT of the urinary tract (CT KUB), which allows the detection of even smaller stones, shows the exact level of obstruction and, based on the size, density, and location of the stone, can help the urologist plan a procedure to remove the stone if necessary (extracorporeal shock wave lithotripsy versus ureteroscopy, percutaneous nephrolithotomy, or, extremely rare these days, open surgery) (Fig. 4.156). an intravenous urogram, which will demonstrate the obstruction, pinpoint the exact level of the stone is currently less often used because access to low-dose CT KUB has increased. In the clinic
Anatomy_Gray_924	Anatomy_Gray	an intravenous urogram, which will demonstrate the obstruction, pinpoint the exact level of the stone is currently less often used because access to low-dose CT KUB has increased. In the clinic Most tumors that arise in the kidney are renal cell carcinomas. These tumors develop from the proximal tubular epithelium. Approximately 5% of tumors within the kidney are transitional cell tumors, which arise from the urothelium of the renal pelvis. Most patients typically have blood in the urine (hematuria), pain in the infrascapular region (loin), and a mass.	Anatomy_Gray. an intravenous urogram, which will demonstrate the obstruction, pinpoint the exact level of the stone is currently less often used because access to low-dose CT KUB has increased. In the clinic Most tumors that arise in the kidney are renal cell carcinomas. These tumors develop from the proximal tubular epithelium. Approximately 5% of tumors within the kidney are transitional cell tumors, which arise from the urothelium of the renal pelvis. Most patients typically have blood in the urine (hematuria), pain in the infrascapular region (loin), and a mass.
Anatomy_Gray_925	Anatomy_Gray	Renal cell tumors (Figs. 4.157 and 4.158) are unusual because not only do they grow outward from the kidney, invading the fat and fascia, but they also spread into the renal vein. This venous extension is rare for any other type of tumor, so, when seen, renal cell carcinoma should be suspected. In addition, the tumor may spread along the renal vein and into the inferior vena cava, and in rare cases can grow into the right atrium across the tricuspid valve and into the pulmonary artery. Treatment for most renal cancers is surgical removal, even when metastatic spread is present, because some patients show regression of metastases.	Anatomy_Gray. Renal cell tumors (Figs. 4.157 and 4.158) are unusual because not only do they grow outward from the kidney, invading the fat and fascia, but they also spread into the renal vein. This venous extension is rare for any other type of tumor, so, when seen, renal cell carcinoma should be suspected. In addition, the tumor may spread along the renal vein and into the inferior vena cava, and in rare cases can grow into the right atrium across the tricuspid valve and into the pulmonary artery. Treatment for most renal cancers is surgical removal, even when metastatic spread is present, because some patients show regression of metastases.
Anatomy_Gray_926	Anatomy_Gray	Treatment for most renal cancers is surgical removal, even when metastatic spread is present, because some patients show regression of metastases. Transitional cell carcinoma arises from the urothelium. The urothelium is present from the calices to the urethra and behaves as a “single unit.” Therefore, when patients develop transitional carcinomas within the bladder, similar tumors may also be present within upper parts of the urinary tract. In patients with bladder cancer, the whole of the urinary tract must always be investigated to exclude the possibility of other tumors (Fig. 4.159). This is currently achieved by performing a dual-phase CT urogram that allows visualization of the renal parenchyma and the collecting system at the same time. In the clinic	Anatomy_Gray. Treatment for most renal cancers is surgical removal, even when metastatic spread is present, because some patients show regression of metastases. Transitional cell carcinoma arises from the urothelium. The urothelium is present from the calices to the urethra and behaves as a “single unit.” Therefore, when patients develop transitional carcinomas within the bladder, similar tumors may also be present within upper parts of the urinary tract. In patients with bladder cancer, the whole of the urinary tract must always be investigated to exclude the possibility of other tumors (Fig. 4.159). This is currently achieved by performing a dual-phase CT urogram that allows visualization of the renal parenchyma and the collecting system at the same time. In the clinic
Anatomy_Gray_927	Anatomy_Gray	In the clinic A nephrostomy is a procedure where a tube is placed through the lateral or posterior abdominal wall into the renal cortex to lie within the renal pelvis. The function of this tube is to allow drainage of urine from the renal pelvis through the tube externally (Fig. 4.160). The kidneys are situated on the posterior abdominal wall, and in thin healthy subjects may be only up to 2 to 3 cm from the skin. Access to the kidney is relatively straightforward, because the kidney can be easily visualized under ultrasound guidance. Using local anesthetic, a needle can be placed, under ultrasound direction, through the skin into the renal cortex and into the renal pelvis. A series of wires and tubes can be passed through the needle to position the drainage catheter.	Anatomy_Gray. In the clinic A nephrostomy is a procedure where a tube is placed through the lateral or posterior abdominal wall into the renal cortex to lie within the renal pelvis. The function of this tube is to allow drainage of urine from the renal pelvis through the tube externally (Fig. 4.160). The kidneys are situated on the posterior abdominal wall, and in thin healthy subjects may be only up to 2 to 3 cm from the skin. Access to the kidney is relatively straightforward, because the kidney can be easily visualized under ultrasound guidance. Using local anesthetic, a needle can be placed, under ultrasound direction, through the skin into the renal cortex and into the renal pelvis. A series of wires and tubes can be passed through the needle to position the drainage catheter.
Anatomy_Gray_928	Anatomy_Gray	The indications for such a procedure are many. In patients with distal ureteric obstruction the back pressure of urine within the ureters and the kidney significantly impairs the function of the kidney. This will produce renal failure and ultimately death. Furthermore, a dilated obstructed system is also susceptible to infection. In many cases, there is not only obstruction producing renal failure but also infected urine within the system. In the clinic Renal transplantation is now a common procedure undertaken in patients with end-stage renal failure. Transplant kidneys are obtained from either living or deceased donors. The living donors are carefully assessed, because harvesting a kidney from a normal healthy individual, even with modern-day medicine, carries a small risk. Deceased kidney donors are brain dead or have suffered cardiac death. The donor kidney is harvested with a small cuff of aortic and venous tissue. The ureter is also harvested.	Anatomy_Gray. The indications for such a procedure are many. In patients with distal ureteric obstruction the back pressure of urine within the ureters and the kidney significantly impairs the function of the kidney. This will produce renal failure and ultimately death. Furthermore, a dilated obstructed system is also susceptible to infection. In many cases, there is not only obstruction producing renal failure but also infected urine within the system. In the clinic Renal transplantation is now a common procedure undertaken in patients with end-stage renal failure. Transplant kidneys are obtained from either living or deceased donors. The living donors are carefully assessed, because harvesting a kidney from a normal healthy individual, even with modern-day medicine, carries a small risk. Deceased kidney donors are brain dead or have suffered cardiac death. The donor kidney is harvested with a small cuff of aortic and venous tissue. The ureter is also harvested.
Anatomy_Gray_929	Anatomy_Gray	An ideal place to situate the transplant kidney is in the left or the right iliac fossa (Fig. 4.161). A curvilinear incision is made paralleling the iliac crest and pubic symphysis. The external oblique muscle, internal oblique muscle, transversus abdominis muscle, and transversalis fascia are divided. The surgeon identifies the parietal peritoneum but does not enter the peritoneal cavity. The parietal peritoneum is medially retracted to reveal the external iliac artery, external iliac vein, and bladder. In some instances the internal iliac artery of the recipient is mobilized and anastomosed directly as an end-to-end procedure onto the renal artery of the donor kidney. Similarly the internal iliac vein is anastomosed to the donor vein. In the presence of a small aortic cuff of tissue the donor artery is anastomosed to the recipient external iliac artery and similarly for the venous anastomosis. The ureter is easily tunneled obliquely through the bladder wall with a straightforward	Anatomy_Gray. An ideal place to situate the transplant kidney is in the left or the right iliac fossa (Fig. 4.161). A curvilinear incision is made paralleling the iliac crest and pubic symphysis. The external oblique muscle, internal oblique muscle, transversus abdominis muscle, and transversalis fascia are divided. The surgeon identifies the parietal peritoneum but does not enter the peritoneal cavity. The parietal peritoneum is medially retracted to reveal the external iliac artery, external iliac vein, and bladder. In some instances the internal iliac artery of the recipient is mobilized and anastomosed directly as an end-to-end procedure onto the renal artery of the donor kidney. Similarly the internal iliac vein is anastomosed to the donor vein. In the presence of a small aortic cuff of tissue the donor artery is anastomosed to the recipient external iliac artery and similarly for the venous anastomosis. The ureter is easily tunneled obliquely through the bladder wall with a straightforward
Anatomy_Gray_930	Anatomy_Gray	donor artery is anastomosed to the recipient external iliac artery and similarly for the venous anastomosis. The ureter is easily tunneled obliquely through the bladder wall with a straightforward anastomosis.	Anatomy_Gray. donor artery is anastomosed to the recipient external iliac artery and similarly for the venous anastomosis. The ureter is easily tunneled obliquely through the bladder wall with a straightforward anastomosis.
Anatomy_Gray_931	Anatomy_Gray	The left and right iliac fossae are ideal locations for the transplant kidney because a new space can be created without compromise to other structures. The great advantage of this procedure is the proximity to the anterior abdominal wall, which permits easy ultrasound visualization of the kidney and Doppler vascular assessment. Furthermore, in this position biopsies are easily obtained. The extraperitoneal approach enables patients to make a swift recovery. In the clinic Investigation of the urinary tract After an appropriate history and examination of the patient, including a digital rectal examination to assess the prostate in men, special investigations are required.	Anatomy_Gray. The left and right iliac fossae are ideal locations for the transplant kidney because a new space can be created without compromise to other structures. The great advantage of this procedure is the proximity to the anterior abdominal wall, which permits easy ultrasound visualization of the kidney and Doppler vascular assessment. Furthermore, in this position biopsies are easily obtained. The extraperitoneal approach enables patients to make a swift recovery. In the clinic Investigation of the urinary tract After an appropriate history and examination of the patient, including a digital rectal examination to assess the prostate in men, special investigations are required.
Anatomy_Gray_932	Anatomy_Gray	After an appropriate history and examination of the patient, including a digital rectal examination to assess the prostate in men, special investigations are required. Cystoscopy is a technique that allows visualization of the urinary bladder and urethra using an optical system attached to a flexible or rigid tube (cystoscope). Images are displayed on a monitor, as done in other endoscopic studies. Biopsies, bladder stone removal, removal of foreign bodies from the bladder, and bleeding cauterization can be performed during cystoscopy. Cystoscopy is helpful in establishing the causes of macroscopic and microscopic hematuria, assessing bladder and urethral diverticula and fistulas, as well as serving as a tool to investigate patients with voiding problems.	Anatomy_Gray. After an appropriate history and examination of the patient, including a digital rectal examination to assess the prostate in men, special investigations are required. Cystoscopy is a technique that allows visualization of the urinary bladder and urethra using an optical system attached to a flexible or rigid tube (cystoscope). Images are displayed on a monitor, as done in other endoscopic studies. Biopsies, bladder stone removal, removal of foreign bodies from the bladder, and bleeding cauterization can be performed during cystoscopy. Cystoscopy is helpful in establishing the causes of macroscopic and microscopic hematuria, assessing bladder and urethral diverticula and fistulas, as well as serving as a tool to investigate patients with voiding problems.
Anatomy_Gray_933	Anatomy_Gray	An IVU is one of the most important and commonly carried out radiological investigations (Fig. 4.162). The patient is injected with iodinated contrast medium. Most contrast media contain three iodine atoms spaced around a benzene ring. The relatively high atomic number of iodine compared to the atomic number of carbon, hydrogen, and oxygen attenuates the radiation beam. After intravenous injection, contrast media are excreted predominantly by glomerular filtration, although some are secreted by the renal tubules. This allows visualization of the collecting system as well as the ureters and bladder. Ultrasound can be used to assess kidney size and the size of the calices, which may be dilated when obstructed. Although the ureters are poorly visualized using ultrasound, the bladder can be easily seen when full. Ultrasound measurements of bladder volume can be obtained before and after micturition.	Anatomy_Gray. An IVU is one of the most important and commonly carried out radiological investigations (Fig. 4.162). The patient is injected with iodinated contrast medium. Most contrast media contain three iodine atoms spaced around a benzene ring. The relatively high atomic number of iodine compared to the atomic number of carbon, hydrogen, and oxygen attenuates the radiation beam. After intravenous injection, contrast media are excreted predominantly by glomerular filtration, although some are secreted by the renal tubules. This allows visualization of the collecting system as well as the ureters and bladder. Ultrasound can be used to assess kidney size and the size of the calices, which may be dilated when obstructed. Although the ureters are poorly visualized using ultrasound, the bladder can be easily seen when full. Ultrasound measurements of bladder volume can be obtained before and after micturition.
Anatomy_Gray_934	Anatomy_Gray	Nuclear medicine is an extremely useful tool for investigating the urinary tract because radioisotope compounds can be used to estimate renal cell mass and function and assess the parenchyma for renal scarring. These tests are often very useful in children when renal scarring and reflux disease is suspected. In the clinic An abdominal aortic aneurysm is a dilation of the aorta and generally tends to occur in the infrarenal region (the region at or below the renal arteries). As the aorta expands, the risk of rupture increases, and it is now generally accepted that when an aneurysm reaches 5.5 cm or greater an operation will significantly benefit the patient. With the aging population, the number of abdominal aortic aneurysms is increasing. Moreover, with the increasing use of imaging techniques, a number of abdominal aortic aneurysms are identified in asymptomatic patients.	Anatomy_Gray. Nuclear medicine is an extremely useful tool for investigating the urinary tract because radioisotope compounds can be used to estimate renal cell mass and function and assess the parenchyma for renal scarring. These tests are often very useful in children when renal scarring and reflux disease is suspected. In the clinic An abdominal aortic aneurysm is a dilation of the aorta and generally tends to occur in the infrarenal region (the region at or below the renal arteries). As the aorta expands, the risk of rupture increases, and it is now generally accepted that when an aneurysm reaches 5.5 cm or greater an operation will significantly benefit the patient. With the aging population, the number of abdominal aortic aneurysms is increasing. Moreover, with the increasing use of imaging techniques, a number of abdominal aortic aneurysms are identified in asymptomatic patients.
Anatomy_Gray_935	Anatomy_Gray	For many years the standard treatment for repair was an open operative technique, which involved a large incision from the xiphoid process of the sternum to the symphysis pubis and dissection of the aneurysm. The aneurysm was excised and a tubular woven graft was sewn into place. Recovery may take a number of days, even weeks, and most patients would be placed in the intensive care unit after the operation. Further developments and techniques have led to a new type of procedure being performed to treat abdominal aortic aneurysms—the endovascular graft (Fig. 4.165).	Anatomy_Gray. For many years the standard treatment for repair was an open operative technique, which involved a large incision from the xiphoid process of the sternum to the symphysis pubis and dissection of the aneurysm. The aneurysm was excised and a tubular woven graft was sewn into place. Recovery may take a number of days, even weeks, and most patients would be placed in the intensive care unit after the operation. Further developments and techniques have led to a new type of procedure being performed to treat abdominal aortic aneurysms—the endovascular graft (Fig. 4.165).
Anatomy_Gray_936	Anatomy_Gray	Further developments and techniques have led to a new type of procedure being performed to treat abdominal aortic aneurysms—the endovascular graft (Fig. 4.165). The technique involves surgically dissecting the femoral artery below the inguinal ligament. A small incision is made in the femoral artery and the preloaded compressed graft with metal support struts is passed on a large catheter into the abdominal aorta through the femoral artery. Using X-ray for guidance the graft is opened, lining the inside of the aorta. Limb attachments are made to the graft that extend into the common iliac vessels. This bifurcated tube device effectively excludes the abdominal aortic aneurysm. This type of device is not suitable for all patients. Patients who receive this device do not need to go to the intensive care unit. Many patients leave the hospital within 24 to 48 hours. Importantly, this device can be used for patients who were deemed unfit for open surgical repair. In the clinic	Anatomy_Gray. Further developments and techniques have led to a new type of procedure being performed to treat abdominal aortic aneurysms—the endovascular graft (Fig. 4.165). The technique involves surgically dissecting the femoral artery below the inguinal ligament. A small incision is made in the femoral artery and the preloaded compressed graft with metal support struts is passed on a large catheter into the abdominal aorta through the femoral artery. Using X-ray for guidance the graft is opened, lining the inside of the aorta. Limb attachments are made to the graft that extend into the common iliac vessels. This bifurcated tube device effectively excludes the abdominal aortic aneurysm. This type of device is not suitable for all patients. Patients who receive this device do not need to go to the intensive care unit. Many patients leave the hospital within 24 to 48 hours. Importantly, this device can be used for patients who were deemed unfit for open surgical repair. In the clinic
Anatomy_Gray_937	Anatomy_Gray	In the clinic Deep vein thrombosis is a potentially fatal condition where a clot (thrombus) is formed in the deep venous system of the legs and the veins of the pelvis. Virchow described the reasons for thrombus formation as decreased blood flow, abnormality of the constituents of blood, and abnormalities of the vessel wall. Common predisposing factors include hospitalization and surgery, the oral contraceptive pill, smoking, and air travel. Other factors include clotting abnormalities (e.g., protein S and protein C deficiency). The diagnosis of deep vein thrombosis may be difficult to establish, with symptoms including leg swelling and pain and discomfort in the calf. It may also be an incidental finding. In practice, patients with suspected deep vein thrombosis undergo a D-dimer blood test, which measures levels of a fibrin degradation product. If this is positive there is a high association with deep vein thrombosis.	Anatomy_Gray. In the clinic Deep vein thrombosis is a potentially fatal condition where a clot (thrombus) is formed in the deep venous system of the legs and the veins of the pelvis. Virchow described the reasons for thrombus formation as decreased blood flow, abnormality of the constituents of blood, and abnormalities of the vessel wall. Common predisposing factors include hospitalization and surgery, the oral contraceptive pill, smoking, and air travel. Other factors include clotting abnormalities (e.g., protein S and protein C deficiency). The diagnosis of deep vein thrombosis may be difficult to establish, with symptoms including leg swelling and pain and discomfort in the calf. It may also be an incidental finding. In practice, patients with suspected deep vein thrombosis undergo a D-dimer blood test, which measures levels of a fibrin degradation product. If this is positive there is a high association with deep vein thrombosis.
Anatomy_Gray_938	Anatomy_Gray	The consequences of deep vein thrombosis are twofold. Occasionally the clot may dislodge and pass into the venous system through the right side of the heart and into the main pulmonary arteries. If the clots are of significant size they obstruct blood flow to the lung and may produce instantaneous death. Secondary complications include destruction of the normal valvular system in the legs, which may lead to venous incompetency and chronic leg swelling with ulceration. The treatment for deep vein thrombosis is prevention. In order to prevent deep vein thrombosis, patients are optimized by removing all potential risk factors. Subcutaneous heparin may be injected and the patient wears compression stockings to prevent venous stasis while in the hospital.	Anatomy_Gray. The consequences of deep vein thrombosis are twofold. Occasionally the clot may dislodge and pass into the venous system through the right side of the heart and into the main pulmonary arteries. If the clots are of significant size they obstruct blood flow to the lung and may produce instantaneous death. Secondary complications include destruction of the normal valvular system in the legs, which may lead to venous incompetency and chronic leg swelling with ulceration. The treatment for deep vein thrombosis is prevention. In order to prevent deep vein thrombosis, patients are optimized by removing all potential risk factors. Subcutaneous heparin may be injected and the patient wears compression stockings to prevent venous stasis while in the hospital.
Anatomy_Gray_939	Anatomy_Gray	In certain situations it is not possible to optimize the patient with prophylactic treatment, and it may be necessary to insert a filter into the inferior vena cava that traps any large clots. It may be removed after the risk period has ended. In the clinic From a clinical perspective, retroperitoneal lymph nodes are arranged in two groups. The pre-aortic lymph node group drains lymph from the embryological midline structures, such as the liver, bowel, and pancreas. The para-aortic lymph node group (the lateral aortic or lumbar nodes), on either side of the aorta, drain lymph from bilateral structures, such as the kidneys and adrenal glands. Organs embryologically derived from the posterior abdominal wall also drain lymph to these nodes. These organs include the ovaries and the testes (importantly, the testes do not drain lymph to the inguinal regions).	Anatomy_Gray. In certain situations it is not possible to optimize the patient with prophylactic treatment, and it may be necessary to insert a filter into the inferior vena cava that traps any large clots. It may be removed after the risk period has ended. In the clinic From a clinical perspective, retroperitoneal lymph nodes are arranged in two groups. The pre-aortic lymph node group drains lymph from the embryological midline structures, such as the liver, bowel, and pancreas. The para-aortic lymph node group (the lateral aortic or lumbar nodes), on either side of the aorta, drain lymph from bilateral structures, such as the kidneys and adrenal glands. Organs embryologically derived from the posterior abdominal wall also drain lymph to these nodes. These organs include the ovaries and the testes (importantly, the testes do not drain lymph to the inguinal regions).