Retroperitoneal Fasciitis: Spectrum of CT Findings in the Abdomen and Pelvis.

Retroperitoneal fasciitis is a rare but potentially lethal complication of infection. Early diagnosis is crucial and is usually made when there is a high degree of clinical suspicion combined with characteristic imaging findings leading to early surgical intervention. Computed tomography (CT) can play a central role in demonstrating early findings, assessing the extent of disease to help determine the best surgical approach, identifying the primary source of infection, and evaluating the treatment response. The possible presence of retroperitoneal fasciitis should be considered in patients presenting with symptoms of sepsis, including pain that is disproportionate with the clinical abnormality. When retroperitoneal fasciitis is suspected, emergency CT can facilitate early diagnosis and evaluation of the extent of disease. Common findings at CT include fascial thickening and enhancement, muscular edema, fat stranding, fluid collections, and abscess formation. Gas tracking along fascial planes in the retroperitoneum is the hallmark of retroperitoneal fasciitis but is not seen in all cases. Another important clue to the diagnosis is asymmetric involvement of the retroperitoneal fascial planes and deep tissues. Fasciitis in the retroperitoneum may originate from infected retroperitoneal organs or from infection that spreads along indirect and/or direct pathways from a primary source elsewhere in the body. Findings of indirect tracking and transgression of fascial planes may indicate more severe infection associated with the necrotizing form of retroperitoneal fasciitis. Despite aggressive antibiotic treatment, early and repeated surgical débridement may be required to remove nonviable tissue in patients with the necrotizing form of retroperitoneal fasciitis. Awareness of the anatomy of the retroperitoneum, potential routes of spread of infection, and the spectrum of CT findings in retroperitoneal fasciitis is needed to achieve prompt diagnosis and guide treatment. ©RSNA, 2015.