Vicarious Contrast Medium Excretion Mimicking Acute Hemorrhage: Don't Call the Interventional Radiologist!

Vicarious contrast medium excretion (VCME) is an uncommon phenomenon in which iodinated contrast is eliminated through non-renal pathways, predominantly via the hepatobiliary system. Although benign, it may closely mimic active gastrointestinal hemorrhage on follow-up computed tomography (CT), potentially leading to unnecessary invasive procedures. We report the case of a 28-year-old woman with acute leukemia complicated by methotrexate-induced acute pancreatitis and massive retroperitoneal hemorrhage. Contrast-enhanced CT demonstrated findings suspicious for active arterial bleeding originating from the gastroduodenal artery territory. Subsequent digital subtraction angiography revealed no definite bleeding source, and empirical coil embolization of the gastroduodenal artery was successfully performed. Following administration of a large cumulative contrast volume and transient renal impairment requiring hemodialysis, repeat CT demonstrated hyperattenuating material within the gallbladder and multiple small-bowel loops, initially raising concern for recurrent gastrointestinal bleeding. Careful review of the unenhanced images confirmed that the hyperdense intraluminal material preceded the second contrast administration and remained unchanged on post-contrast images, establishing the diagnosis of simultaneous hepatobiliary and intestinal VCME. This case highlights an important diagnostic pitfall following repeated contrast-enhanced imaging and endovascular intervention. Recognition of the characteristic imaging features of VCME, particularly the presence of hyperattenuating bowel contents on unenhanced CT and the absence of interval enhancement, is essential for differentiating this benign entity from true recurrent hemorrhage and for avoiding unnecessary angiography, embolization, or surgery.