A 64-year-old woman presented with acute severe lower abdominal pain (VAS 10) and rectal bleeding (once). She was afebrile with normal vital signs but had diffuse abdominal tenderness with peritoneal irritation signs. Hb was 12.3 g/L (normocytic), WBC 16.3×10⁹/L (left shift), albumin 3.4 g/L. CT demonstrated extensive retroperitoneal free air (figure 1). Laparotomy revealed large faecal stones in the rectosigmoid colon with adjacent perforation of the posterior wall and peritonitis. No diverticula were identified. Sigmoidectomy with end colostomy (Hartmann’s procedure) was done followed by anorectal stump dilatation and removal of large faecal stones. The surgical specimen showed a 3.5 cm tear in a normal mucosa. Recovery on intravenous ampicillin and metronidazole was uneventful. She had been suffering from chronic arachnoiditis …