Bowel Obstruction

Bowel Obstruction

Cardinal features of intestinal obstruction: vomiting, colicky pain, constipation and distension
Several categories have been used to classify differences in the various presentations of intestinal obstruction. Ask yourself:
  • Cardinal features of bowel obstruction present?
  • Degree of obstruction to flow (partial or complete)
  • Site of obstruction (small bowel or large bowel)
  • Mechanical obstruction or ileus?
  • Absence or presence of intestinal ischemia (simple or strangulated).

Cardinal features of bowel obstruction?

  • Colicky abdominal pain
  • Distension
  • Absolute constipation/obstipation
  • Nausea and Vomiting
Bowel Obstruction copy

Pathophysiology disruption of the normal flow of intestinal contents leading to proximal dilatation and distal decompression may take 12-24 h to decompress, therefore passage of feces and atus may occur a er the onset of obstruction bowel ischemia may occur if blood supply is strangulated or if bowel wall in ammation leads to venous congestion bowel wall edema and disruption of normal bowel absorptive function can lead to increased intraluminal uid and transudative fluid loss into peritoneal cavity, electrolyte disturbances

Video: Bowel Obstruction Overview

Is it a partial or complete bowel obstruction?

  • Partial Obstruction - still can pass gas +/- diarrhoea
  • Complete Obstruction - can not pass gas or poo

Is it obstruction of the small or large bowel?

Small Bowel Large bowel Ileus 
Main Aetiology (in order) Adhesions, Hernia, Cancer Cancer, Diverticulitis, Volvulus Post operative, medication, chronic disease
Nausea,vomiting Early, may be bilious Late may be faeculent Present
Abdominal Pain and Distension Colicky and slight distention + Colicky and distended ++ Minimal or absent
Constipation + + +
Bowel Sounds Normal, initially increased and may decrease late Normal, initially increased and may decrease late Decreased or absent
Abdominal X-ray
  • Air fluid levels "ladder pattern"
  • Proximal distention + no colonic gas
  • Central abdominal intestinal obstruction
  • Thumb printing
  • Air fluid levels "Picture frame" appearance.
  • Proximal distention + distal decompression.
  • No small bowel air if competent ileocecal valve
  • Air throughout small bowel and colon
Remember Ileus is temporary paralysis of the myenteric plexus. Contents of the small intestine are acutely unable to transit because of impermanent neural or muscular inadequacy.

Mechanical obstruction or ileus?

Mechanical Obstruction 

  • Volvulus
  • Intersussception
  • Colon Cancer
  • Hernia
  • Adhesions
  • Diverticulitis

Pseudo-obstruction (non-mechanical obstruction)

Remember Pseudo-obstruction refers to intestinal dysmotility syndromes that have signs, symptoms, and the radiologic appearance of obstruction in the absence of a mechanical cause
  • Ileus Temporary paralysis of the myenteric plexus. Contents of the small intestine are acutely unable to transit because of impermanent neural or muscular inadequacy. Sudden and severe pain, nausea, vomiting, abdominal distention, and inability to tolerate a diet or to pass stools typically accompany ileus, but ultimately the condition resolves completely.
  • Toxic Megacolon - defined by a diameter of the rectosigmoid region or descending colon on abdominal plain film of greater than 6.5 cm; an ascending colon diameter of greater than 8 cm; or a cecal diameter greater than 12 cm. Megacolon can be caused by aganglionosis (Hirschsprung’s disease), can be idiopathic (complicating chronic constipation of any cause), or may be a manifestation of a generalized GI dysmotility (intestinoparesis).
  • Ogilvie's Syndrome - "acute colonic pseudo-obstruction" It is characterized by acute massive colon dilatation that involves primarily the right side of the colon and is unexplained by mechanical cause. It is most often diagnosed in hospitalized, debilitated, medical or surgical patients with a wide array of medical condition
  • Hirschsprung’s disease - (Paediatrics) The most common cause of congenital megarectum and megacolon.
  • Chronic Pseudo obstruction - Many causes. Can be divided into Primary (Amyloidosis, myopathies/neuropathies) and Secondary (endocrine disorders, medications and infections)

Absence or presence of intestinal ischemia (simple or strangulated)

  • Simple: one obstructing point and no vascular compromise
  • Strangulated: Blood supply is compromised and the patient is more ill than you would expect. Features suggesting strangulation are:
    • Change in character of pain from colicky to continuous
    • Tachycardia
    • Pyrexia
    • Peritonism
    • Bowel sounds absent or reduced
    • Leucocytosis
    • Raised C-reactive protein (CRP)



  Small bowel Large bowel
Location Central Peripheral
Content Fluid and air Faecal matter
Wall Patern Encircling valvulae conniventes visible depending on degree of air filling/distention. Haustral folds interspaced with Plicae semilunaris
Size 3cm diameter 6cm diameter (caecum 9cm)
3, 6, 9 Rule
Small intestine 3cm
Large intestine 6cm
Caecum 9cm
Remember Any increase in these numbers signify dilatation most likely due to an obstruction


  • Preoperative
    • Nil by mouth
    • IV fluids
    • IV analgesia (pain)
    • IV antibiotics
  • Nasogastric tube
    • Gastric aspiration by means of nasogastric suction (decompression)
  • Surgical
    • Bowel resection