Transvaginal sonographic appearance of peritoneal pseudocysts

To describe the sonographic features of peritoneal pseudocysts (PPCs) in order to determine the particular aspects that distinguish them from true ovarian cysts.

Thirty-one women with PPCs were investigated using transvaginal sonography immediately before surgery. The diameters of the cysts were measured, and the shape, margins, content, location, presence of septa and echogenic portions were analyzed.

The PPCs were monolateral in 20 (65%) and bilateral in 11 (35%) women. A well-defined cystic structure was found in only six (19%) women, while in the other 25 (81%) women the PPCs showed blurred, undefined margins and a bizarre morphology, giving them a star-like tubular or lumpy shape. The ipsilateral ovary was identified in 26 (84%) cases either external to the cyst or entrapped within it like a 'spider in a web'. Septa were present in 25 (81%) cases and were often mobile, resembling a 'flapping sail' when touched by the endovaginal probe.

Despite having a gross morphology resembling that of a true ovarian cyst, PPCs present some characteristic sonographic findings that allow a correct differential diagnosis in the vast majority of cases.