A 71-year-old woman was referred for a second opinion before hospice with progressive abdominal pain, fullness, diarrhea, and weight loss. A workup revealed ascites and esophageal varices. Imaging showed seven liver lesions that were suspicious for hepatocellular carcinoma (HCC) on a computed tomography scan (Fig. 1A), and follow-up magnetic resonance imaging revealed arterial enhancement followed by washout. A tissue sample was compatible with well-differentiated HCC (CD34 and glutamine synthetase positivity, reticulin loss, and isolated vessels); the background liver revealed hepatoportal sclerosis without cirrhosis (Fig. 1B). A further review of the abdominal scan revealed a dilated inferior mesenteric vein (IMV) due to an arteriovenous malformation (AVM), which was confirmed by angiography (Fig. 1C). There was no evidence of trauma or prior surgery. There was no endoscopic evidence of ischemia or a superficial AVM in the terminal ileum or ascending colon, and biopsies were normal. She underwent transhepatic mesenteric venous coil embolization, which reduced the IMV flow and the main portal venous pressure from 46 to 26 mm Hg. Shortly after the procedure, there was significant improvement in her diarrhea and abdominal pain. Four months later, the ascites had fully resolved, and she had gained weight. Furthermore, abdominal imaging demonstrated complete resolution of the hepatic lesions (Fig. 1D).
This is the first known case in which an intra-abdominal AVM produced (1) chronic intestinal ischemia and diarrhea from arteriovenous shunting of blood; (2) noncirrhotic, presinusoidal portal hypertension with varices and ascites; and (3) multiple hepatic nodules suspicious for HCC (all of which completely resolved after venous embolization).
Splanchnic AVMs commonly involve the hepatic or splenic artery, but IMV involvement is rare.1 Mesenteric AVMs alter vascular flow, reduce the distal arterial pressure, and increase the proximal venous pressure.2 This bypasses the capillary bed and induces a form of mesenteric steal syndrome, which results in abdominal pain, weight loss, diarrhea, and nonocclusive ischemic colitis. Several reports describe inferior mesenteric arteriovenous fistulas resulting in clinically significant arteriovenous shunting.3–5 The symptoms correlate with the amount of blood shunted and the length of time for which the malformation has been present.
Hyperdynamic flow from AVMs can also result in presinusoidal portal hypertension. Ascites, varices, and splenomegaly are well-described complications of mesenteric AVMs,1, 6 and arterialization of the portal venous system can significantly increase hepatic blood inflow. Progressive hypertrophy of fibrous liver tissue ensues with thickening of the venous walls and sinusoidal dilation.7 These changes result in hepatoportal sclerosis (seen on liver biopsy) and portal hypertensive physiology.
The patient's hepatic lesions were concerning for HCC because of the findings on imaging and biopsy. However, the complete regression of these lesions after embolization suggests that they were regenerative nodules or areas of focal nodular hyperplasia. Wanless et al.8 described parenchymal cell hypertrophy (focal nodular hyperplasia) as resulting from increased portal flow to selected hepatic regions. There are reports of both nodular hyperplasia and HCC development due to altered vascular flow; however, none of these were caused by an AVM directly leading to shunting of blood into the portal system.9, 10
Therefore, this unusual vascular malformation at the IMV fulfilled Occam's razor and resulted in three distinct clinical findings: arteriovenous shunting with intestinal ischemia, presinusoidal portal hypertension, and hepatic neoplastic nodules. Fortunately, these were fully resolved after therapeutic occlusion of the vascular abnormality.