Our notes are now found under OSCE Learning! Click here

Abdominal radiograph interpretation


  • Patient: name, DOB, hospital number, age, sex
  • Previous films for comparison

Radiograph detail

  • Date
  • Type (supine, upright, lateral decubitus)
  • Adequacy 
    • Area (diaphragm to pelvis)
    • Rotation
    • Penetration

Upper limits of normal bowel diameters

3-6-9 rule

3cm = small bowel

6cm = large bowel

9cm = caecum and sigmoid

Interpretation (BOB)

Briefly mention obvious abnormalities first.


  • Small bowel
    • Identify by: central position; plicae circulares/valvulae conniventes (mucosal folds that cross the whole width of the bowel)
    • Should be <3cm in diameter (enlarged in small bowel obstruction)
  • Large bowel 
    • Identify by: peripheral position; faecal contents; haustra (pouches that protrude into the lumen)
    • Should be <6cm in diameter (enlarged in large bowel obstruction)
  • Faeces (mottled appearance)
  • Gas (normal in fundus and large bowel only): extra-luminal gas indicates perforation; check for gas in rectum if bowel obstruction suspected (presence makes complete obstruction less likely)
  • Fluid levels seen in perforation/infection

Other organs 

  • Soft tissue shadows (may be seen)
    • Liver
    • Spleen
    • Kidneys
    • Gallbladder
    • Psoas shadow (lost in retroperitoneal inflammation or ascites)
  • Calcification of pancreas (chronic pancreatitis), abdominal aorta (atherosclerosis) or renal stones/gallstones


  • Spine and pelvis: Paget’s disease (cotton wool lytic/sclerotic pattern); metastasis (lytic/sclerotic lesions); osteoarthritis (loss of joint space, osteophytes, subchondral sclerosis/cysts); vertebral fractures

To complete

  • ‘To complete my analysis, I would examine previous films and ascertain the clinical history.’
  • ‘If there is any suspicion of perforation, I would request an erect chest x-ray to look for air under the diaphragm.’
  • Summarise and suggest differentials

Common pathology  

  • Small bowel obstruction: small bowel distension >3cm, no gas in large bowel, fluid levels if erect
  • Large bowel obstruction: large bowel distension >6cm
  • Toxic megacolon: colonic dilatation without obstruction, associated with colitis 
  • Volvulus: twisting of bowel on its mesentery, causing coffee-bean appearance if sigmoid volvulus or ‘fetal’ appearance if caecal
  • Chronic pancreatitis: pancreatic calcification
  • Urinary stones 
  • Pneumoperitoneum (due to viscus perforation or recent surgery): Rigler’s double wall sign – both sides of bowel wall visible due to air outside the bowel