A 78-year-old man with a history of left renal cell carcinoma currently treated with pembrolizumab presented with a urinary tract infection and altered mental status. Physical exam revealed no hepatomegaly. Laboratory work-up revealed elevated ammonia [113 µmol/L], ALT [132 U/L], and GGT [106 U/L], with normal ALT and AST.
Abdominal CT with contrast in portal venous phase 2 months prior to current presentation incidentally revealed a 2.9 cm hyper-enhancing right hepatic lobe lesion that appears to connect to the portal (Fig. 1a & Fig. 1b) and hepatic veins (Fig. 1c). Axial CT image in arterial phase shows minor enhancement of the lesion (Fig. 1d)
Upon admission, real-time sonographic images were obtained due to elevated liver function tests. This revealed a 2.5 x 2.95 cm x 4.5 cm fusiform anechoic-appearing structure within the right hepatic lobe adjacent to vascular structures with positive color fill-in on duplex doppler (Fig. 2a). The color doppler also demonstrates evidence of bidirectional flow, known as the Yin-yang sign, which is characteristic of a pseudoaneurysm or fistula . This lesion appears to connect to the right and left portal veins (Fig. 2b) and middle hepatic vein (Fig. 2c)
Liver appears within normal limits in echotexture.
The liver receives approximately 2/3 of its blood supply from the portal vein. After blood is filtered by the liver, it accumulates in the central veins and eventually drains into the hepatic veins and then the inferior vena cava. A portosystemic shunt is a connection between the portal vein and systemic circulation that bypasses the liver . These shunts are often detected on abdominal CT or ultrasound.
The iatrogenic shunt, known as a transjugular intrahepatic portosystemic shunt [TIPS], is the result of a surgical procedure that connects the portal vein to a portion of the hepatic vein to decrease portal pressure in patients with portal hypertension . Congenital shunts are a rare condition due to abnormal development during embryogenesis. Symptoms commonly present during childhood . Spontaneous portosystemic shunts are seen mostly in patients with liver cirrhosis. These shunts were originally thought to be protective against gastric and esophageal varices as well as ascites by decompressing the portal system. However, recent studies have found them to be ineffective at decreasing portal pressure .
When blood is redirected from the liver, it leads to ineffective detoxification of the blood. This can lead to a buildup of metabolites, such as ammonia, in the blood resulting in hepatic encephalopathy . Treatment for spontaneous portosystemic shunts can include medical or surgical management. Medical management of hepatic encephalopathy using lactulose or rifaximin to reduce serum ammonia levels may be sufficient . However, in severe cases, surgical management to obliterate the shunt may be used . This patient was effectively managed with lactulose. Surgery is not being considered currently due to patient age and effective medical management.
Before biopsy of a lesion, it is necessary to perform doppler study to identify vascular involvement. This can drastically change a differential diagnosis. In this case, the vascularity of the lesion directed the differential away from a diagnosis such solid hepatic neoplasm.
This is case is unique because this patient displays no signs of liver cirrhosis or portal hypertension, but still appears to have a portosystemic shunt. There is no prior imaging to determine how long this shunt has been present to rule out congenital shunt. It is likely that the shunt is the result of a portal or hepatic vein aneurysm that connected to the portal and hepatic drainage systems.
Written informed consent for publication has been obtained from empowered 1st degree relative.
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