Portal vein disorders
Nearly all portal vein disorders obstruct portal, vein blood flow and cause portal hypertension.
Obstruction can be extra hepatic eg portal vein thrombosis congenital atresia of the portal vein) or intrahepatic (e.g microvascular portal vein obstruction in schistosomiasis).
Portal vein Thrombosis
Portal vein thrombosis produces portal hypertension and consequent GI bleeding.
Diagnosis is based on ultrasound.
Treatment involves control of GI bleeding (usually with endoscopy or IV octerotide), sometimes surgical shunts or beta-blockers, and for acute thrombosis, possibly thrombosis
Etiology
Portal vein thrombosis in neonates commonly results from umbilical stump infection that spreads via umbilical vein to the portal vein.
In older children the culprit is acute appendicitis, in which infection sometimes enters the portal system, causing vascular infection (pylephlebitis), which can trigger thrombosis.
Congenital anomalies of the portal vein causing portal vein thrombosis usually accompany congenital defects elsewhere.
In adults common causes are surgery (e.g. splenectomy), hypercoagulable states (e.g myeloproliferative disorder, protein C or S deficiency), cancer (e.g. hepatocellular or pancreatic carcinoma), cirrhosis and pregnancy.
The cause is unknown in about 50% of the cases
Symptoms,Signs and Diagnosis
Symptoms rarely develop acutely unless mesenteric venous thrombosis occurs simultaneously,which causes significant abdominal pain.
Most symptoms and signs develop chronically secondary to portal hypertension and include splenomegaly (especially in children) and GI bleeding.
Ascites is rarely due to portal hypertension alone and, if present indicates hepatocellular dysfunction from a separate disorder.
Portal vein thrombosis is suspected in patients with manifestations of portal hypertension without cirrhosis and in patients with even mild abnormalities in liver function or enzymes who have risk factors such as neonatal umbilical infection, childhood appendicitis or hypercoagulable state.
Doppler ultrasound is usually diagnostic, revealing diminished or absent portal vein flow and sometimes the thrombus.
Difficult cases may require MRI or CT with contrast.
Angiography may be required to guide shunt surgery
Treatment
In acute cases, anticoagulation sometimes prevents clot propagation but doesn’t dissolve existing clots.
In neonates and children,treatment is directed at the cause ( e.g. omphalitis,appendicitis).
Otherwise treatment is directed at portal hypertension and variceal bleeding.
Endoscopic banding is usually used to control variceal bleeding.
Octreotide IV, a synthetic analog of somatostatin,may also help.
These therapies have decreased the use of surgical shunts (e.g. mesocaval, splenorenal), which have problems with occlusion and operative mortality (5 -50%).
Beta-Blockade (often combined with nitrates) is predicted to be as effective for preventing bleeding as in portal hypertension from cirrhosis but has not been tested.
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