Ascites matters

The excess accumulation of intra-peritoneal fluid, referred to as ascites, is an important clue that points to a significant underlying illness. This may be due to a pathological event within the peritoneal cavity or secondary to an underlying systemic condition. Ascites is broadly classified into transudate and exudate, based on protein content, with a potential wide range of differential diagnoses. Traditionally, computed tomography has been regarded as the imaging modality of choice to demonstrate ascites and diagnose the underlying cause. However, ultrasound can reliably detect small volumes of fluid and is a useful first-line imaging modality for clinical triage. For instance, in the emergency setting, the detection of a trace of ascites may be the earliest indicator of an acute abdomen needing surgery. Ultrasound can quantify the volume of ascites and aid in the decision process for fluid drainage. Ultrasound is superior to computed tomography in the qualitative assessment of fluid. Broadly, simple fluid is anechoic, whereas complex fluid may appear particulate, layered or contain septations. On computed tomography, both have a uniform hypo-dense appearance and are often indistinguishable. Given ultrasound, in comparison to computed tomography, is safe, relatively inexpensive and readily available, it is a valuable tool in the assessment of ascites. Once ascites is detected on ultrasound, it is imperative for the operator to have a systematic approach to attempt to provide an underlying diagnosis. Through a series of cases, this article aims to increase awareness and reaffirm the role of ultrasound in the assessment of ascites.