Appearance and distinguishing features of retroperitoneal calcifications at computed tomography.

Objectives: To describe the appearance of retroperitoneal calcifications seen at computed tomography (CT) and to investigate which CT features distinguish benign from malignant retroperitoneal calcifications.

Methods: We identified 25 patients with retroperitoneal calcifications by retrospective review of 39,931 abdominopelvic CT scans. Etiology of retroperitoneal calcifications was determined by examination of medical and histopathological records. By consensus, 2 abdominal radiologists recorded calcification number (solitary or multiple), location (suprarenal or infrarenal), morphology (globular or nonglobular), and the presence of soft-tissue components. The association between CT findings and etiology was assessed using the Fisher exact test.

Results: Retroperitoneal calcifications were malignant in 15 patients and benign in 10. Solitary calcifications were seen more commonly in patients with benign disease (6 of 10 vs. 1 of 15, P < 0.01). Suprarenal calcifications were seen only in patients with malignancy (13 of 15 patients, P < 0.01). Nonglobular calcifications were seen only in patients with benign disease (6 of 10, P < 0.01). Soft-tissue components were seen more commonly in patients with malignancy (14 of 15 vs. 4 of 10; P < 0.01).

Conclusions: Retroperitoneal calcifications are rarely seen at CT and may be benign or malignant in etiology. Solitary or nonglobular retroperitoneal calcifications are likely to be benign while calcifications that are multiple, globular, suprarenal, or associated with noncalcified soft-tissue components are likely to be malignant.