Abdominal radiograph interpretation

Introduction

• 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.

Bowel

• 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

Bones

• 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