Teaching Case

A 36-year-old woman was admitted to our emergency medicine department due to persistent symptoms of fever, abdominal pain, elevated C reactive protein and leucocytosis. One week earlier, she was treated for possible pyelonephritis and empirical antibiotic therapy was initiated.

Abdominal contrast-enhanced computed tomography (CT) scan (figure 1) showed hepatomegaly with an inhomogeneous mottled pattern due to heterogeneous perfusion of the liver parenchyma, commonly referred as a "mosaic" enhancement pattern. Additionally, there was a striated nephrogram as typically observed in pyelonephritis (figure 2). The suprahepatic veins and inferior vena cava (IVC) were permeable (figure 3).

The hospitalization of our patient was uneventful and she was discharged after a short stay at the hospital. In her last follow-up, one month after the proper antibiotic therapy, she was well and the imaging abnormalities disappeared in the liver once the extrahepatic condition had resolved (figure 4).

The stasis of blood within hepatic sinusoids and/or the altered hemodynamics subsequent to hepatic venous outflow obstruction produces a “mosaic” enhancement pattern of the hepatic parenchyma.  In the absence of hepatic venous outflow obstruction, extrahepatic inflammatory and infectious conditions such as pyelonephritis, cholecystitis, pneumonia, pancreatitis, intestinal bowel disease, pelvic inflammatory disease, and the use of oral contraceptives can also lead to hepatic sinusoidal dilatation. [1] [2]

This patient could be considered to have Budd-Chiari Syndrome but no venous thrombosis was present, thus the “mosaic” pattern could be likely due to the progress and infiltration of the inflammatory process.

This case shows that acute extrahepatic diseases associated with a marked systemic inflammatory syndrome can cause a hepatic mosaic enhancement pattern on contrast-enhanced CT. These imaging features resolve following treatment of the inflammatory response. A possible explanation is that reversible CT findings were a consequence of the liver infiltration with interleukin-6 and vascular endothelial growth factor due to systemic inflammatory syndrome. [3] The liver biopsy should only be considered if liver abnormalities persist.

Hepatic sinusoidal dilatation is commonly associated with hepatic venous outflow obstruction and presents with a typical ‘‘mosaic’’ liver enhancement pattern on contrast-enhanced CT and MR imaging. Although there are other conditions that also produce alterations in hepatic perfusion, the correlation of the imaging findings with the clinical history and an un­derstanding of the physiopathology should enable a correct diagnosis.