Bowel Obstruction

Causes of Mechanical Obstruction:

1. Intra-luminal:

Bowel obstruction 1
  • Neoplasm (either benign or malignant)
  • Gallstone ileum
  • Fecal impaction
  • Foreign body
  • Bezoar (hairball; trichobezoar, or some fruit fibers)
  • Parasitic infestation
  • Blood clot
  • Inspissated contrast material (if not taking plenty of fluid with barium; Barolith)


2. Extra-luminal: extrinsic compression by:

  • Intra-abdominal tumors known to attain large size: ovarian masses, mesenteric cysts, lymphoma ‘GEST’, cystic lesion of the pancreas, retroperitoneal ca
  • Tumor cell deposits in the mesentery, which kinks the bowel and causes obstruction
  • Hernias:
    • Internal:
      • Congenital: foramen of Winslow (see figure below): behind the hepato-duodenal ligament (which contains: CBD, portal vein, hepatic A)
      • Surgically-created: like in bowel resection leading to a defect in mesentery causing potential space for hernia, Petersen’s space caused by bariatric surgeries)
    • External:
      • Naturally occurring: umbilical, para-umbilical, femoral, inguinal, obturator
      • Incisional: post laparotomy, or adhesions (MCC is post Op, or post inflammatory e.g. PID)
Bowel obstruction 3
Foramen of Winslow


3. Intramural:

  • Bowel volvulus:
    • In order for volvulus to occur -> there has to be a free segment + fixation in 2 areas; most susceptible part is sigmoid colon
    • An emergency? b/c as the bowel twists, the mesentery twists and w/ it the blood supply -> causing ischemia, gangrene, perforation
  • Intussusception:
    • More common in pediatrics -> treated w/ contrast enemies by which the pressure opens the obstruction
    • But in adults, usually there’s a lead-point of anatomical pathology which is usually tumor -> reducing it is no enough, so you need to scope/operate
  • Inflammatory:
    • Acute exacerbation of crohn’s due to inflammation and edema -> here, resist the temptation of operation, why? b/c you’re putting anastomosis in an inflamed area -> high risk of leak (130%). So treat with nasogastric suctioning, TPN, maximize anti-crohn’s treatment -> most of them will open up in few days
    • But chronically, if not taken care of -> you will heal w/ fibrosis. So treatment here is surgical
  • Ischemia: “what doesn’t kill you makes you stronger”
    • If not transmural -> you will recover by fibrosis and adhesions, and thus; causing obstruction


Cardinal Features:

  • Abdominal pain, distension, vomiting, and constipation
  • If proximal obstruction: crampy abdominal pain followed by early vomiting, but normal bowel movement and minimal distension
  • If distal obstruction (recto-sigmoid): crampy abdominal pain followed by early constipation and massive distension, vomiting is absent/late
  • The ability to pass bowel motion is by no means a guarantee against obstruction, why?
    • The bowel content beyond the level of obstruction
    • W/ few days of stool stasis -> the body tries to liquefy it to clear the way -> diarrhea
  • Bowel sounds are usually increased (high pitched) in bowel obstruction
  • But, if persistent obstruction -> causes perforation; so after a certain period where the bowel can’t overcome the obstruction -> it will stop contracting -> decreased bowel sounds
    • Question;2 pts w/ bowel obstruction, one w/ increased bowel sounds, the other w/ absent/decreased bowel sounds. Which one you’ll be more worried about? The one w/ the silent bowel (b/c it might be peritonitis)
  • Dehydration, electrolyte imbalance (which need to be corrected before surgery!)


Approach to a Case of Bowel Obstruction:

  1. Is it obstruction or not?
  2. What’s the likely level of obstruction? 
  3. What’s the likely cause? 
  4. Partial or complete?
    • Still passing stool = partial obstruction
    • No bowel movement for > 24 hrs; obstipation = complete obstruction
  5. Simple or complicated?
    • Compromised blood flow (ischemia, gangrene, perforation)
  6. Any systemic manifestations caused by that obstruction?
    • Dehydration, electrolyte disturbances, hemodynamic instability, renal impairment (pre-renal azotemia)


CASE: A 24 yo lady, underwent appendectomy at the age of 14, now presenting w/ partial distal adhesive small bowel obstruction, no peritoneal signs (=simple obstruction), mild-moderate dehydration and electrolyte disturbances. What is the appropriate treatment?

Conservative therapy: Fluid/electrolyte replacements, nasogastric decompression -> w/in 2-3 days, majority of the patients open up


CASE: A 65 yo male, presenting w/ intermittent PR bleeding over 4 mo, wt loss, obstipation for 24 hrs, massive abdominal distension, vomited once. What to do?

This is a complete bowel obstruction at the level of recto-sigmoid or left colon (b/c of PR bleeding. If presents w/ anemia -> right bowel): most likely malignant tumor, and it won’t improve w/ conservative treatment



Download the PDF version: here


  • Dr Alabeidi’s lecture
  • Monte Reid

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