Nodular regenerative hyperplasia of the liver: clinical and radiologic observations.

This report describes 21 cases of nodular regenerative hyperplasia (NRH) and its clinical and radiologic features. NRH of the liver is an established pathologic entity that should not be confused with focal nodular hyperplasia, hepatocellular adenoma, or the regenerative nodules associated with cirrhosis. Correct diagnosis will prevent an unnecessary hepatic lobectomy should NRH be mistaken for hepatocellular adenoma. Unlike focal nodular hyperplasia, NRH may bleed, may be associated with portal hypertension in one-half of cases, and is often associated with a systemic disease such as a myelo- or lymphoproliferative disorder. Correct diagnosis is important because the prognosis in patients with NRH and portal hypertension is better than that in patients with portal hypertension due to cirrhosis. Radiologically, multiple nodules, large masses, or an apparently normal liver (containing nodules less than 0.5 cm in diameter) were visible. The nodules may take up technetium sulfur colloid and have variable echogenicity on sonography. They are often hypodense on CT without significant enhancement. The nodules may fill from the periphery on angiography, are vascular, and sometimes contain small hypovascular areas due to hemorrhage. A large nodule may rupture and cause hemoperitoneum. These findings may resemble some features of focal nodular hyperplasia, hepatocellular adenoma, or metastases. NRH is probably underdiagnosed owing to a lack of recognition of the entity and limited sampling of liver tissue by needle biopsy. Scintigraphy, sonography, and CT of the liver should be performed in cases of idiopathic portal hypertension to detect NRH. In cases with compatible findings, multiple needle biopsies or a laparoscopically guided needle biopsy or wedge liver biopsy should be recommended for definitive diagnosis.