Delayed enhancement of ascites after i.v. contrast material administration at CT: time course and clinical correlation.

OBJECTIVE

The objective of our study was to determine the prevalence and clinical predictors of delayed contrast enhancement of ascites.

METHODS

In this retrospective study, 132 consecutive patients with ascites who underwent repeated abdominopelvic CT examinations performed within 7 days of each other were identified. These patients included 112 patients who received and 20 who did not receive i.v. contrast material at the initial CT examination. For each examination, we recorded the CT attenuation of the ascites. For the follow-up scan, the presence of delayed enhancement of ascites was defined as an increase in CT attenuation > 10 HU over baseline. The Fisher's exact test, unpaired Student's t test, and logistic regression were used to determine predictors of delayed enhancement of ascites.

RESULTS

A threshold increase in the attenuation of ascites by > 10 HU or more between the initial and follow-up CT examinations occurred only when i.v. contrast material was given with the initial examination. The increased attenuation was due to delayed contrast enhancement of ascites and occurred in 15 of the 112 patients (13%). Of the 16 patients scanned less than 1 day apart, 10 (63%) showed delayed enhancement of ascites. Delayed enhancement was not observed 3 or more days after i.v. contrast material administration. For each 1 mg/dL increase in serum creatinine level, the likelihood of delayed enhancement of ascites increased (odds ratio, 2.02; 95% CI, 1.11-3.69). Multivariate logistic regression showed that a short time interval between examinations (p < 0.001), increased serum creatinine level (p < 0.001), and presence of loculated ascites (p = < 0.01) were independent predictors of the magnitude of delayed enhancement of ascites.

CONCLUSIONS

Delayed contrast enhancement of ascites occurs commonly after recent prior i.v. contrast material administration and should not be mistaken for hemoperitoneum or proteinaceous fluid such as pus.