Gas On Abdominal X-ray DDx
Overview
Location of gas on the abdominal x-ray may suggest the the underlying cause
- Intraluminal gas — bowel gas pattern
- Free intraperitoneal air — pneumoperitoneum
- Other gas collections — biliary, intramural, etc.
Bowel gas patterns may point to an underlying cause — bowel gas patterns include:
- Normal
- Nonspecific
- Adynamic ileus
- Mild — localized ileus or “sentinel loop”
- Severe — “colonic pseudo-obstruction”
- Small bowel obstruction; central, valvulae conniventes, pliable (“bent finger”)
- Large bowel obstruction – peripheral, haustra, contains feces
Causes
Pneumoperitoneum
Causes
- Perforated peptic ulcer (usually duodenal)
- Gastric ulcer perforation (benign or malignant)
- Intestinal perforation (e.g. large bowel obstruction causing cecal perforation, inflammatory bowel disease)
- Cecal or sigmoid volvulus
- Perforated appendicitis or diverticulitis (infrequent)
- Colonoscopy and biopsy
- Residual postoperative gas
- Post-laparoscopy
- Post-dialysis
- Penetrating trauma
- Breakdown of surgical anastomosis
- Ruptured pneumatosis cystoides intestinalis (e.g. ischemic gut, necrotizing enterocolitis)
- Gas-forming intra-abdominal infection
- Extension from the chest (e.g. pneumomediastinum, bronchopleural fistula)
- Air via uterine tubes (e.g. post-sexual activity, spa bath, water ski-ing)
Mimics of pneumoperitoneum
- Hepatodiaphragmantic interposition of the colon
- Idiopathic (Chilaiditi syndrome)
- Secondary to colonic distention (obstruction or ileus)
- Rib margin that parallels diaphragm
- Perihepatic fat
Right upper quadrant gas
- Gallstone ileus (biliary-enteric fistula) [Rigler triad; Bouveret syndrome]
- Sphincterotomy or surgical anastomosis
- Emphysematous cholecystitis
- Hepatic portal venous gas (bowel infarction)
- Hepatic or subdiaphragmatic abscess
- Pneumoperitoneum (overlying liver)
- Hydrogen peroxide ingestion (or other gas forming substance)
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Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at The Alfred ICU, where he is Deputy Director (Education). He is a Clinical Adjunct Associate Professor at Monash University, the Lead for the Clinician Educator Incubator programme, and a CICM First Part Examiner.
He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives. He was one of the founders of the FOAM movement (Free Open-Access Medical education) has been recognised for his contributions to education with awards from ANZICS, ANZAHPE, and ACEM.
His one great achievement is being the father of three amazing children.
On Bluesky, he is @precordialthump.bsky.social and on the site that Elon has screwed up, he is @precordialthump.
| INTENSIVE | RAGE | Resuscitology | SMACC