Congenital absence of the portal vein (CAPV) is a rare disorder that may lead to the development of hepatic neoplasms, hepatic encephalopathy, pulmonary hypertension (PH), and hepatopulmonary syndrome (HPS). The portal vein develops by selective involution of the vitelline venous system, and associated abnormalities may result in CAPV. Some patients with CAPV are diagnosed at the time of neonatal screening for hypergalactosemia.1 The etiology of PH/HPS is an imbalance of vasoconstrictors and vasodilators, either produced or metabolized by the liver, that affect the pulmonary arterioles and capillaries by a portosystemic shunt.2 A patient whose portal vein is patent and perfuses the liver as well as a shunt vessel (type 2) can be treated by shunt ligation (or graded shunt embolization) without portal hypertension being induced. However, if the liver is not perfused with portal blood and the entire splanchnic blood supply flows through a shunt vessel into a systemic vein (type 1), then either surgical or radiological intervention of the portal vein might be contraindicated. Liver transplantation (LT) is indicated as a curative operation for CAPV in patients with uncontrollable hepatic encephalopathy and PH/HPS. Situs inversus (SI) is also a rare congenital anomaly with a frequency of 0.002% to 0.1%.3 SI occurs in association with polysplenia syndrome and midgut malrotation, a preduodenal portal vein, an aberrant hepatic arterial supply, and absence of the inferior vena cava (IVC). Consideration, therefore, has to be given to additional vascular reconstruction at LT for CAPV with SI.
A 16-month-old Asian girl weighing 9.5 kg who presented with hyperammonemia (serum NH3, 150 μmol/L) was admitted to the hospital. The patient was diagnosed to have hypergalactosemia by neonatal metabolic screening. At the time of assessment, a laboratory evaluation showed the following: serum bilirubin, 0.34 mg/dL; aspartate aminotransferase, 72 IU/L; gamma glutamyl transferase, 21 IU/L; albumin, 2.8 g/dL; total protein, 4.8 g/dL; total biliary acid, 126.6 μmol/L; and prothrombin time international normalized ratio, 1.21. Further imaging studies revealed CAPV with SI, polysplenia, and absence of the retrohepatic IVC (Fig. 1). The results of a chest and cardiac examination were unremarkable. Because of recurrent hyperammonemia and progressive hyperintensity in the globus pallidus on magnetic resonance imaging, despite medical treatment and protein restriction, the patient underwent living donor LT.
The donor was her 27-year-old mother, who had the identical blood type. The liver graft, a reduced left lateral sector weighing 154 g and thus representing 1.62% of the graft-to-recipient weight ratio, was procured. The recipient laparotomy showed CAPV, SI, polysplenia, midgut malrotation, and absence of the retrohepatic IVC. The hepatic veins drained directly into the right atrium (Fig. 2A). The right renal vein was patent and drained through the retroperitoneal channels into the azygous system. The recipient hepatectomy was uncomplicated. A histological examination of the 200 g of explanted symmetric native liver, which was 61.6% of the estimated standard liver volume, showed atrophic portal veins visible in the portal tracts (Fig. 2B). The conduit of the superior mesenteric vein and splenic vein drained into the right renal vein without entering the hepatic hilum (Fig. 3A). After the hepatic vein reconstruction to the right atrium, the shunt vessel was divided at its junction with the right renal vein. The stump of the shunt vessels, measuring 3.0 cm in length, was turned upward behind the pancreas and anastomosed directly to the graft portal vein in an end-to-end fashion (Fig. 3B). During the clamping of the portal vein, the portal vein pressure increased from 12 to 32 mm Hg. Mesenteric venous congestion developed, but it was tolerable over the 21 minutes of warm ischemic time. Biliary reconstruction was carried out with a Roux-en-Y choledochojejunostomy. The operation lasted 8 hours 36 minutes, and the blood loss was 520 mL. The postoperative course was uneventful, and the patient was discharged on postoperative day 39. During the 9-month follow-up, the patient did well with normal liver function and normal magnetic resonance imaging findings without hyperammonemia.
The type 1 anomaly seen in the present case is often associated with aberrant malformations, such as biliary atresia, liver tumors, cardiac anomalies, and polysplenia. The present case had 3 additional conditions not reported so far: SI, polysplenia, and absence of the retrohepatic IVC, which are otherwise technically demanding if LT is indicated. The indications for LT in patients with CAPV have not yet been established. Ten cases of CAPV treated with LT have been reported.1, 4–13 The indications for LT were liver cirrhosis secondary to biliary atresia in 5, an unresectable liver tumor in 3, hyperammonemia in 3, PH in 2, HPS in 1, and hematochezia in 1, and they were resistant to conventional medical treatment. PH was not seen in the present patient; the pathophysiology of PH in CAPV is demonstrated as thromboembolic pulmonary arterial hypertension, and this state can be cured if the shunt vessel can be closed. Recently, preemptive LT for a CAPV patient was performed because LT is the only therapeutic option to prevent regression of progressive PH.14 In HPS, there is an imbalance between vasodilator and vasoconstrictor substances that have activity in the pulmonary circulation. Pulmonary vasodilation may occur if portocaval shunting impairs the metabolism of vasoactive substances by the liver. Emre et al.13 reported that HPS could be treated by the routing of the portal flow into the liver with auxiliary LT because it confirms that a major cause of HPS is impaired hepatic clearance of vasoactive substances.
Early LT should therefore be indicated in symptomatic CAPV patients, even in those without impaired liver function, before advanced PH/HPS and/or irreversible brain damage due to hyperammonemia.