Hemoperitoneum

Hemoperitoneum (plural: haemoperitoneums) is the presence of blood within the peritoneal cavity.

Pathology

Etiology

• penetrating or non-penetrating abdominal trauma (often with associated organ injury) ¹
• ruptured ectopic pregnancy
• ovarian cyst rupture
• aneurysm or pseudoaneurysm rupture
• neoplasm rupture
• acute hemorrhagic pancreatitis
• iatrogenic
• spontaneous bleeding, especially patients with coagulopathy or on anticoagulant therapy (uncommon) ¹

Radiographic features

Ultrasound

• non-specific appearance of intraperitoneal free fluid ⁴
  • may be hypo-, iso- or hyperechoic ³
• may demonstrate fluid-fluid levels with mixed internal echogenicity ³

CT

The density of fluid in the abdomen suggests its composition (i.e. ascites/bowel contents/bile vs hemorrhage) ¹:

• recent hemorrhage (acute bleed) measures 30-45 HU
• clotted blood measures 45-70 HU
• old blood products/seroma or blood in patients with anemia may measure <30 HU

A collection of blood products can be homogeneous or heterogeneous (often low density with internal linear/nodular hyperdensities) ⁵; fluid-fluid levels are often present. 

MRI

• acute (<48 hours) hemoperitoneum has non-specific signal characteristics ⁵
• subacute (>3 weeks) may demonstrate concentric ring sign ⁵
• fluid-fluid levels (hematocrit effect) with high T1 / low T2 signal noted dependently ⁵

Differential diagnosis

• low-density hemoperitoneum may be indistinguishable from ascites or other causes of peritoneal free fluid ² 
• there may be a delayed increase in ascites attenuation after administration of IV contrast (up to 3 days)
  • there may be an increase of up to 25 HU ⁶
• urine in the peritoneal cavity with density approaching that of water due to bladder injury