Computed Tomography in the Diagnosis of Ascites: The Role of Fluid Attenuation Values

Intraperitoneal fluid accumulations are a common matter in current clinical practice, being encountered by most medical and surgical fields.

To assess ascites fluid with attenuation values in the form of Hounsfield units (HU) in order to determine a non-invasive differentiation criterion for the diagnosis of intraperitoneal collections.

Sixty patients with known intra-peritoneal collections who underwent computed tomography (CT) for reasons such as tumor staging, post-surgical follow-up or other indications, were retrospectively included in this study. All subjects had a final pathological analysis of the fluid collections. Two radiologists measured the attenuation values for each collection. The averaged values were used for comparing benign and malignancy-related ascites (MRA), bland and hemorrhagic ascites and infected and noninfected fluid collections by consuming the Mann-Whitney U test. Also, the receiver operating characteristic analysis was performed for the statistically significant results (P<0.05), and the area under the curve (AUC) was calculated.

Attenuation values could differentiate between benign and MRA (P=0.04; AUC=0.656; sensitivity, 65.52%; specificity, 71.43%) but failed to distinguish between bland ascites and ascites with hemorrhagic component (P=0.85), and between infected and noninfected fluid collections (P=0.47).

Although the results are statistically significant, the substrate of differentiation between benign and MRA ascites cannot be clearly stated. As being the first study to investigate this issue, it opens the way for other researches in the field to determine the dynamics of imaging quantitative measurements according to the fluid's pathological features.