Dirty Mass sign of abdominal imaging: A case of silent pneumoperitoneum

Abstract

Pneumoperitoneum is a common complication after penetrating abdominal trauma, gastric ulcer, or colitis in which free air is present in the peritoneal or retroperitoneal space. Sole pneumoretroperitoneum, which refers to gas in the retroperitoneal space, is a rare entity, and when significant, results in a characteristic radiographic sign known as "Dirty Mass." Common causes include penetrating trauma or perforation of the retroperitoneal portions of the gastrointestinal tract (duodenum, ascending colon, descending colon, and rectum). Our case describes a 59-year-old female admitted for sudden onset RLQ abdominal pain with Dirty Mass sign on abdominal KUB. Early recognition of these key radiographic findings accelerates management and reduces the risk of developing complications.

Keywords: Colonic perforation; Dirty Mass; Dirty Mass sign; Pneumoretroperitoneum; Retroperitoneum.

Fig. 1

Supine AP view of the abdomen and pelvis with atypical collection of air in the right upper quadrant compatible with “Dirty Mass sign,” outlining the superior pole of the right kidney, findings suggestive of isolated retroperitoneal air.

Fig. 2

(A) Coronal CT image shows atypical collection of air in the right upper quadrant and (B) axial CT image reveals perforation at the posterior medial wall of the proximal ascending colon.