Magnetic resonance cholangiopancreatography and a “starry sky” liver

Abstract

Magnetic resonance cholangiopancreatography showed multiple small hyperintensive round nodules creating a “starry sky” appearance in a patient with multiple biliary microhamartomas of liver.

Case Report

A 60‐year‐old woman was referred to our hospital because of abnormal hepatic ultrasonography (US). On abdominal examination, no hepatomegaly or splenomegaly was observed. Blood tests revealed normal liver function tests, normal results for alpha fetoprotein and carcinoembryonic antigen, and negative tests for hepatitis B and C. On US, multiple small hyperechoic nodules were seen in the entire liver. Computed tomography (CT) with contrast enhancement revealed multiple small hypodense spots without enhancement throughout the entire liver (Fig. 1). In contrast, magnetic resonance cholangiopancreatography (MRCP) showed multiple small hyperintensive round nodules all over the liver, demonstrating a “starry sky” (Fig. 2). These findings are compatible with multiple biliary microhamartomas of the liver. These images were unchanged during the 3‐year follow‐up in this patient.

Figure 1.

Contrast‐enhanced computed tomography (CT) of liver.

Figure 2.

A “starry sky” appearance on magnetic resonance cholangiopancreatography (MRCP).

Biliary microhamartoma, also known as Von Meyenburg complex, is a benign lesion consisting of a collection of bile ducts set in a fibrous stroma that may be hyalinized. ¹ Hamartomas were found in 0.69% of 876 autopsy cases in a larger study. ² However, diffuse multiple biliary microhamratomas are obviously rare and found by coincidence. Biliary microhamartomas usually cause no symptoms or liver function test abnormalities, but they are occasionally associated with cholangiocarcinoma or cholangitis.

US demonstrated typical findings, such as a markedly heterogeneous hyperechoic pattern with small cystic lesions. CT demonstrated multiple low attenuation focal defects scattered throughout both lobes that showed no enhancement by contrast medium. However, US and CT findings sometimes have difficulty distinguishing microhamartomas from other diseases, such as liver metastases, diffuse hepatocellular carcinoma, microabscesses, schistosomiasis, and granulomatous diseases. In such cases, magnetic resonance imaging (MRI) and MRCP are very useful in diagnosing multiple biliary microhamartomas showing countless delineated hyperintense cystic nodules (not communicating with the biliary system) that create a “starry sky” appearance. ³ , ⁴ These findings will make diagnosis easy and liver biopsy unnecessary. Clinicians should be aware of this clinicopathologic entity and MRCP findings to differentiate biliary microhamartomas from other liver diseases.