Peritoneal inclusion cysts: clinical characteristics and imaging features

ObjectivesTo investigate the frequency of patient characteristics, causative factors and imaging features associated with pathology-proven peritoneal inclusion cysts (PICs).MethodsFrom a retrospective search of all available hospital records—dating back 19 years—we identified 228 patients with pathology-proven PICs. Descriptive statistics were calculated for patients’ demographic and clinical characteristics. Imaging features of pathology-proven PICs were recorded on a total of 77 computed tomography (CT), magnetic resonance imaging (MRI) and/or ultrasound (US) studies from patients who underwent imaging before surgery.ResultsPICs occurred over a wide age range (18–89 years); 82.5 % of patients were women and 17.5 % were men. A history of prior insult to the peritoneum was identified in 70.6 % of patients. Imaging appearances of PICs ranged from loculated, simple fluid collections to complex, multi-septated lesions. In the absence of haemorrhage or debris, PICs were never found to have thick walls. The presence of nodularity, papillary excrescences or other solid components also excluded a diagnosis of PIC, as did the presence of more than a physiological amount of ascites, provided the ascites had no alternate explanation.ConclusionsPICs are more common than suggested by previously published reports. Knowledge of patient characteristics and typical PIC imaging appearances may prevent unnecessary or unnecessarily aggressive therapy.Key Points• Peritoneal inclusion cysts (PIC) occur in women and men at all ages• PICs may be incidental findings, both at imaging and during surgery• Especially in symptomatic patients, PICs may be mistaken for cystic neoplasms• Knowledge of demographics and typical imaging features may prevent unnecessarily aggressive therapy• Thick walls, solid component and ascites are inconsistent features of a PIC