Congenital absence of the portal vein (CAPV) is a rare anomaly in which portal venous blood bypasses the liver through a congenital portosystemic shunt.[1,2,3,4,5,6,7,8,9,10,11] The drainage sites of portal venous blood include the inferior vena cava (IVC), the left renal vein and less commonly the internal iliac vein, azygosvein and right atrium.[1,2,3,4,5,6,7,8,9,10,11] Although the portosystemic shunt may be accompanied by hyperammonemia, hyperbilirubinemia and hypergalactosemia; hyperinsulinemia and hyperandrogenism have rarely been reported in patients with CAPV.[1,12] To the best of our knowledge, only three cases of congenital extrahepatic portosystemic shunts with hyperinsulinemia and hyperandrogenism have been reported.[5,12] We report a case of CAPV associated with large inferior mesenteric-caval shunt in a 20 year old female with hyperinsulinemia and hyperandrogenism.

Case report

A 20 year old female presented to our hospital with history of rectal bleeding since 5 years of age. She required multiple blood transfusions because of chronic rectal bleeding and severe anemia. She underwent hemorrhoidectomy thrice in past without any significant relief in the symptoms. No significant family history was present. The patient had primary amenorrhoea and signs of secondary virilization including clitoromegaly. On examination, breast development was normal (Tanner stage 4). There were excessive hairs over the face and back. Neurological examination was normal and there were no manifestation of hepatic encephalopathy.

Liver function tests revealed normal levels of transaminase, alkaline phosphate and bilirubin. Serological markers for hepatitis B and C were negative and serum ammonia levels were normal (48 µg/dl). Serum FSH, LH and estradiol were within normal range. Oral glucose tolerance test revealed hyperglycemia and hyperinsulinemia indicating insulin insensitivity. Serum testosterone levels were 1.49 ng/ml (normal range: 0.05-0.73 ng/ml), and dehydroepiandosterone (DHEA) level was 6.5 ng/ml.

Ultrasound revealed absence of the portal vein. The right lobe of the liver was hypoplastic and there was no focal lesion. However, ultrasound failed to demonstrate the anatomy of extra hepatic portosystemic shunt. Ultrasound pelvis revealed normal sized uterus and enlarged ovaries. CECT of the abdomen revealed normal hepatic veins and absence of intrahepatic portal vein (Figure 1). A markedly dilated inferior mesenteric vein was seen draining into the internal iliac veins (Figure 2, 3). Celiac axis and superior mesenteric artery were normal. Spleen was normal in size and there were no portosystemic collaterals. Echocardiography was normal.

A diagnosis of the congenital absence of the portal vein associated with large inferior mesenteric-caval shunt causing hyperinsulinemia and hyperandrogenism was made. The patient was started on the cyclic oestrogen and her menstrual cycles started.

Discussion

Congenital absence of the portal vein (CAPV), a subtype of congenital portosystemic shunt is a rare anomaly with only few cases reported in the literature.[1,2,3,4,5,6,7,8,9,10,11] Abernethy malformation in which there is congenital diversion of the blood away from the liver was first reported in 1793. Morgan and Superina[13] classified congenital extra hepatic portosystemic shunts in two types: type 1 (side to end anastomosis) or congenital absence of the portal vein occurs predominately in females and is associated with multiple malformations; and Type II (side to side anastomosis) in which portal vein supply is partially preserved and have no sex predisposition and associated malformations.

In CAPV the intestinal and splenic venous drainage bypasses the liver and drains directly into the systemic veins.[13] CAPV is further classified into two types based on the anatomy of the portal vein. In type A, the superior mesenteric vein and splenic vein do not join and drain separately into systemic veins. In type B, the superior mesenteric vein and the splenic vein join before draining into systemic vein. Drainage sites include inferior vena cava (IVC), the left renal vein and less commonly the internal iliac vein, azygos vein and right atrium. The present case corresponds to type B.

CAPV with large inferior mesenteric–iliac vein shunt is uncommon since shorter tracts (splenorenal, superior mesenteric-caval) are utilized in preference to this long venous channel. CAPV results from aberration in venous development in early embryonic life. Embryologically, portal vein develops from selective involution of right and left vitelline veins and their medial anastomosis during second month of gestation. Excessive involution results in absence of the portal vein. Development of inferior vena cava in close proximity of the portal vein and during same time period likely explains the basis of congenital extra hepatic portosystemic shunts.[3,6] The age of diagnosis of CAPV ranges from 1 day to 64 years. However, they predominantly occur in females and children.[1,2,3,4,5,6,7,8,9,10,11] Extrahepatic portosystemic shunt occurs without secondary signs of portal hypertension, such as venous collateral, ascites, and splenomegaly. Liver function tests and ammonia levels are either normal or mildly elevated. Clinical presentation is variable and reported presentations include hypergalactosemia, hyperammonemia, hyperbilirubinemia, liver mass, mental retardation, amenorrhea and hemorrhoidal bledding.1-12 Our case presented with complaints of hemorrhoidal bleeding and amenorrhea.

Hyperinsulinemia in congenital portosystemic shunt is secondary to increased production and reduced clearance of the insulin. Production increases because of impaired glucose utilization by liver secondary to reduced supply of insulin and glucose from portal vein. Portal blood bypasses the liver, thus reducing the clearance of insulin. Satoh et al[12] postulated that hyperinsulinemia in congenital portosystemic shunt leads to hyperandrogenism akin to insulin resistance states like polycystic ovary syndrome and insulin resistance diabetes mellitus.

Congenital absence of the portal vein is usually associated with other congenital abnormalities[1,10,14] including cardiovascular (dextrocardia, ventricular or atrial septal defects, patent foramen ovale and ductus arteriosus); skeletal (hemivertebrae, oculoauriculovertebral dysplasia); and biliary (biliary atresia). None of these congenital malformations was present in the present case. Liver neoplasm (focal nodular hyperplasia, adenoma, hepatoblastoma, HCC) are also frequently associated with CAPV.[14] No hepatic lesion was identified in our patient.

The right lobe of liver was hypoplastic in the present case. Similarly hypoplastic right lobe and small liver volumes was reported by Goo et al.[8] The authors postulated that hypoplasia might have resulted from insufficient supply of hepatotrophic substance to the liver. Liver transplantation is the only effective treatment for CAPV.

References