Hemoperitoneum may occur in various emergent conditions. In the trauma setting, evidence of intraperitoneal blood depicted at computed tomography (CT) should lead the radiologist to conduct a careful search of images for the injured visceral organ (the liver or spleen). Specific CT signs, such as a sentinel clot or extravasation of intravascular contrast material, may indicate the source of bleeding and help direct management. In addition, the configuration of accumulated blood may help identify the injured organ; for example, triangular fluid collections are observed in the mesentery most often in the setting of bowel or mesenteric injury. Less commonly, hemoperitoneum may have a nontraumatic origin. Iatrogenic hemoperitoneum may occur as a complication of surgery or other interventional procedures in the abdominal cavity or as a result of anticoagulation therapy. Hemoperitoneum also may be seen in the setting of blood dyscrasias such as hemophilia and polycythemia vera. Tumor-associated hemorrhage, which most often occurs in hepatocellular carcinoma, hepatic adenoma, or vascular metastatic disease, also may produce hemoperitoneum. Other potential causes of nontraumatic hemoperitoneum are gynecologic conditions such as hemorrhage or rupture of an ovarian cyst and rupture of the gestational sac in ectopic pregnancy, and hepatic hematoma in syndromic hemolysis with elevated liver enzymes and low platelet count (HELLP syndrome). Vascular lesions (visceral artery aneurysms and pseudoaneurysms) that occur in systemic vascular diseases such as Ehlers-Danlos syndrome or in pancreatitis are another less common source of hemoperitoneum. ©RSNA, 2007.