2. The hemiazygous vein ascends on the left side of the vertebral column and drains blood from the left renal vein to the azygous vein.
B. The inferior vena cava (IVC) is formed by the union of the right and left common iliac veins at vertebral level L5, drains all the blood from below the diaphragm (even portal blood from the gastrointestinal tract after it percolates through the liver) to the right atrium. The IVC may be damaged during surgical repair of a herniated intervertebral disk. The IVC above the kidneys (suprarenal) should never be ligated because the mortality rate is 100%. The IVC below the kidneys (infrarenal) may be ligated, although the mortality rate is 50%. The right gonadal vein drains directly into the IVC; the left gonadal vein drains into the left renal vein. This anatomy is important to remember: in a woman, right-sided hydronephrosis may indicate thrombosis of the right ovarian vein, which would constrict the ureter because the right ovarian vein crosses the ureter to drain into the IVC; in a man, left-sided testicular varicocele may indicate occlusion of the left testicular vein or left renal vein by a malignant tumor of the kidney. If the IVC is blocked by either a malignant retroperitoneal tumor or a large blood clot (thrombus), two routes of collateral venous return are followed: (1) azygous vein superior vena cava right atrium; and (2) lumbar veins external and internal vertebral venous plexuses cranial dural sinuses internal jugular vein right atrium.
Esophageal varices Caput medusa
Left gastric vein < ► esophageal vein Paraumbilical vein < > superficial and inferior epigastric veins Superior rectal vein < - middle and inferior rectal veins
Figure 8-3. The hepatic portal system. Note the three main sites (A, B, and C) of portal— IVC (caval) anastomosis. In portal hypertension, in which blood flow through the liver is severely reduced (X), these anastomoses provide collateral circulation (arrows) through the IVC back to the heart. AZ= azygous vein; EV = esophageal vein; IEV= inferior epigastric vein; IMV = inferior mesenteric vein; IRV = inferior rectal vein; IVC= inferior vena cava; LGV= left gastric vein; PUV= paraumbilical vein; PV = portal vein; SEV= superior epigastric vein; SMV= superior mesenteric vein; SRV= superior rectal vein; SV= splenic vein. (Adapted with permission from Moore KL: Clinically Oriented Anatomy, 3rd ed. Baltimore, Williams & Wilkins, 1992, p 210.)
Inferior Vena Caval Anastomosis
III. HEPATIC PORTAL SYSTEM (Figure 8-3). The term "portal" refers to a vein interposed between two capillary beds (i.e., capillary bed-vein-capillary bed). The hepatic portal system consists of the following vascular structures: capillaries of the gastrointestinal tract -> portal vein ► hepatic sinusoids. The portal vein is formed posterior to the neck of the pancreas by the union of the splenic vein and superior mesenteric vein. The inferior mesenteric vein usually ends by joining the splenic vein. The blood within the portal vein carries high levels of nutrients from the gastrointestinal tract as well as products of red blood cell destruction from the spleen. Portal—IVC (caval) anastomosis becomes clinically relevant when portal hypertension occurs. Portal hypertension causes blood within the portal vein to reverse its flow and enter the IVC to return to the heart. The three main sites of portal—IVC anastomosis are the esophagus, umbilicus, and rectum. Clinical signs of portal hypertension include: vomiting copious amounts of blood, a history of alcoholism, liver cirrhosis, schistosomiasis, enlarged abdomen as a result of ascites fluid, and splenomegaly.
Was this article helpful?
Do You Suffer From High Blood Pressure? Do You Feel Like This Silent Killer Might Be Stalking You? Have you been diagnosed or pre-hypertension and hypertension? Then JOIN THE CROWD Nearly 1 in 3 adults in the United States suffer from High Blood Pressure and only 1 in 3 adults are actually aware that they have it.