Learning Radiology xray montage

Large Bowel Obstruction


General Considerations

  • In this case, we are talking about mechanical obstruction of the colon
  • Causes include
    • Carcinoma (60%)
    • Diverticulitis (20%)
    • Volvulus
    • Strictures, such as from Crohn disease
    • Fecal impaction
    • Hernia
    • Imperforate anus or meconium ileus in pediatric population
  • Increases in prevalence with age

Clinical Findings

  • Abdominal distension
  • Nausea and vomiting
  • Crampy abdominal pain
  • Constipation, diarrhea, change in bowel habits

Imaging Findings

  • Air in dilated colon, usually to the point of obstruction
  • Dilated cecum
  • Small bowel is not dilated unless ileo-cecal valve becomes incompetent and air flows backwards from colon to small bowel
  • CT is imaging study of choice

Differential Diagnosis

  • Generalized ileus – air in dilated large and small bowel down to and including rectosigmoid
  • Ogilvie Syndrome (pseudo-obstruction) – absent or reduced bowel sounds, usually associated with other co-morbidities


large bowel obstruction 


Large Bowel Obstruction. The ascending, transverse and proximal descending colon (black arrows) are all dilated. There is an abrupt cut-ff of the air column in the distal descending colon (red arrow). This was the site of a colonic carcinoma, which was removed..