Classification of acute pancreatitis based on retroperitoneal extension: application of the concept of interfascial planes

This study aimed to provide a classification system for acute pancreatitis by applying the principle that the disease spreads along the retroperitoneal interfascial planes.

Medical records and computed tomography (CT) images of 58 patients with acute pancreatitis treated between 2000 and 2005 were reviewed. The retroperitoneum was subdivided into 10 components according to the concept of interfascial planes. Severity of acute pancreatitis was graded according to retroperitoneal extension into these components. Clinical courses and outcomes were compared with the grades. The prognostic value of our classification system was compared with that of Balthazar's CT severity index (CTSI).

Retroperitoneal extension of acute fluid collection was classified into five grades: Grade I, fluid confined to the anterior pararenal space or retromesenteric plane (8 patients); Grade II, fluid spreading into the lateroconal or retrorenal plane (16 patients); Grade III, fluid spreading into the combined interfascial plane (8 patients); Grade IV, fluid spreading into the subfascial plane beyond the interfascial planes (15 patients); and Grade V, fluid intruding into the posterior pararenal space (11 patients). Morbidity and mortality were 92.3% and 38.5% in the 26 patients with Grade IV or V disease, and 21.9% and 0% in the 32 patients with Grade I, II, or III disease. Morbidity and mortality were 86.7% and 33.3% in patients with disease classified "severe" according to the CTSI, and 37.5% and 9.4% in patients with disease classified "mild" or "moderate".

Classification of acute pancreatitis based on CT-determined retroperitoneal extension is a useful indicator of the disease severity and prognosis without the need for contrast-medium enhanced CT.