Inferior mesenteric AVF is a rare splanchnic AVF. Only 11 cases have been reported in the literature[3
]. Our patient had no history of abdominal trauma or abdominal surgery other than liver transplantation. An abdominal CT scan performed before liver transplantation demonstrated a small inferior mesenteric AVF, suggesting that the fistula is congenital in origin and increases in size after transplantation, resulting in the patient’s presentation.
The common clinical symptoms and signs of inferior mesenteric AVF include abdominal pain, mass, or bruit, or a combination of these symptoms[2,3
]. More serious manifestations of mesenteric AVF are associated with portal hypertension, which is present in about 50% of patients with splanchnic AVF[1
]. Okada et al[3
] reported that 7 of 11 patients with inferior mesenteric AVF had either signs or symptoms of portal hypertension (mainly ascites, esophageal varices, or splenomegaly) or elevated portal venous pressure. Portal hypertension in an inferior mesenteric AVF is called “forward” or “hyperkinetic” portal hypertension and may result from both increased blood flow into the portal system and from compensatory increase in hepatic vascular resistance[2,3,12
]. Inferior mesenteric AVF may also be a factor predisposing to non-occlusive ischemic colitis[2
]. An AVF is usually associated with decreased arterial blood flow to the tissue beyond it and increased venous pressure distal to it[2,12
Portal venous stenosis in patients who have undergone orthotopic liver transplantation may be caused by disparity in the diameters of recipient and donor portal veins (particularly in pediatric transplanta-tions). Cryopreserved grafts, excessively long vessel stumps or thrombotic occlusion of the veno-venous bypass, or portosystemic shunt surgery can be used prior to transplantation[10,11,13
]. The majority of those patients who are found to have portal vein stenosis are otherwise asymptomatic and detected on routine screening ultrasound[10
]. Contrast-enhanced CT scan and magnetic resonance imaging can clearly show portal vein stenosis. When patients are symptomatic, they also present with typical signs of portal hypertension, including ascites, esophageal varices, and splenomegaly with or without thrombocytopenia.
The present patient reported no usual symptoms of ischemic colitis, such as hematochezia, melena, or abdominal pain before liver transplantation. However, he suffered from esophageal variceal hemorrhages and ascites, which were thought to be caused by advanced hepatic cirrhosis and portal hypertension. Two years after transplantation, he presented with abdominal pain and hematochezia. Colonoscopy and histopathologic evaluation of biopsy specimens revealed ischemic colitis in the sigmoid and descending colon, and radiologic evaluation showed an inferior mesenteric AVF and portal vein stenosis, suggesting that the portal vein stenosis induced portal hypertension is associated with hepatofugal flow. High arterial flow due to inferior mesenteric AVF and venous stasis in the fistula due to hepatofugal flow, may have contribute to the pseudoaneurysmal dilatation of the inferior mesenteric vein in our patient, leading to augmentation of the preexisting inferior mesenteric AVF and induced the development of ischemic colitis due to steal phenomenon.
Percutaneous transhepatic balloon angioplasty or placement of metal stent has been widely accepted as a safe and effective procedure for portal vein stenosis following liver transplantation[13
]. Our patient underwent percutaneous transhepatic deployment of a metal stent with balloon angioplasty. The stent patency was good, the stenosis was disappeared after treatment.
The choice of therapy for inferior mesenteric AVF is surgical correction with or without associated bowel resection[3
]. Some studies reported that percutaneous endovascular embolization of the feeding artery may be useful in selected cases, particularly in critically ill patients[2,4,7
]. In our case, the combination of clinical state, CT and endoscopic images and the presence of the large AVF all prompted a surgical repair.
Inferior mesenteric AVF is rare, but may be associated with portal hypertension and non-occlusive ischemic colitis. To our knowledge, this is the first report of inferior mesenteric AVF-induced ischemic colitis complicated by portal vein stenosis developed after liver transplantation.