Imaging description

Delayed contrast-enhanced CT in patients with ascites frequently shows increased density of the ascitic fluid when compared to the initial post-contrast images (Figure 69.1), likely due to permeation of intravenous contrast into the peritoneal cavity. Enhancing ascites could be misinterpreted as indicating gastrointestinal perforation with leakage of positive oral contrast into the peritoneal cavity, leakage of excreted contrast from the urinary tract into the peritoneal cavity, or active bleeding with extravasation of intravenous contrast from the vascular system [1,2].

Importance

Enhancing ascites may result in a misdiagnosis of gastrointestinal perforation, potentially resulting in unnecessary surgery.

Typical clinical scenario

Enhancing ascites is likely to be most problematic when patients with ascites develop abdominal pain. In a study of 50 patients with ascites and delayed contrast-enhanced CT, 27 (54%) showed an interval increase in density of ascites (mean increase of 25 Hounsfield Units) on delayed images (obtained after a mean interval of 33 minutes). Enhancement of ascitic fluid was unrelated to history of malignancy, renal function, or serum albumin level. The authors speculated that passage of intravenous contrast into the peritoneal cavity might reflect altered membrane permeability. This seems plausible because the peritoneum is a dynamic organ and substances may equilibrate between the vascular compartment and the peritoneal space (this is the basis for peritoneal dialysis).