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)

CCC Differential Diagnosis Series
NEURO	Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision
RESP	Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement
CVS	Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction
GIT	Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage
GUT	Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency,
MSK	Arthritis, Shoulder pain, Wasting of the small muscles of the hand
DERM	Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans
ENDO	Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss
HAEM	Splenomegaly
PAEDS	Floppy infant
MISC	Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest
IMAGING	CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR, ABDO: Gas on abdominal X-ray, Kidney mass, BRAIN: Intracranial calcification, Intracranial structures with contrast, Ventriculomegaly, OTHER: Pseudofracture on X-Ray,
LABS	LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia,  HIGH: Bilirubin and Jaundice, Hyperammonaemia, Hypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia,  ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis, Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes

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