Pneumoperitoneum: Rigler sign

Case contribution: Dr Radhiana Hassan


  • A 53 years with rectosigmoid adenocarcinoma
  • ┬áHad sigmoid colectomy and left ureterotomy with stenting done
  • Patient complaint of left sided abdominal pain on day 8 post operation
Chest radiograph PA erect view

Chest radiograph findings:

  • Presence of free intraperitoneal seen
  • Bilateral subdiaphragmatic free air (red arrows)
  • Rigler sign (yellow arrow) with visualization of gastric wall
  • Central venous line in-situ
  • No pneumothorax

Radiological diagnosis: Pneumoperitoneum( subdiaphragmatic free air and Rigler sign)


  • Free intraperitoneal gas can be seen following surgical procedures.
  • It occurs in up to 60% of laparotomies and 25% of laparoscopic procedures.
  • The volume of gas on serial radiographs should decrease.
  • If volume is increasing, bowel perforation or anastomotic leak should be suspected.
  • Signs of pneumoperitoneum on plain radiograph include subdiaphragmatic free air and rigler sign as seen in this case.
  • Rigler sign is also known as double-wall sign of pneumoperitoneum seen when gas is outlining both sides of bowel wall. It is usually seen when there is large amounts of pneumoperitoneum (>1000mL)
  • Other radiographic signs include cupola sign

Progress of patient:

  • Subsequent imaging confirmed anastomotic leak in this case

CT scan findings:

  • A suspicious small discontinuity at rectal wall is noted (red arrows).
  • Presence of loose surgical material at this region is also observed.
  • Fluid is seen tracking from gap into the larger left paracolic gutter collection.

Lower GI contrast study done:

  • Diluted Gastrografin (1:1) is infused via rectum through a Foley’s catheter 18F size, already anchored within the anal canal.
  • Free cephalic flow of contrast is observed through rectum till the descending colon.
  • Contrast extravasation from the anterior part of the rectum is observed approximately 12 cm from the anal verge, (red arrows) at the region of the anastomosis.
Author: radhianahassan