Mechanical Bowel Obstruction and Ileus: Pathogenesis and clinical findings
Anti-motility Diabetic Sepsis drugs gastroparesis
Nerves coordinating bowel peristalsis are disrupted
Ileus: functional bowel ‘blockage’, no peristalsis
Post- operation
Hernia (no past surgery)
Post-abdominal surgery
Authors: Yan Yu, Wayne Rosen* Reviewers: Nicole Burma, Jason Baserman, Jennifer Au, Maitreyi Raman* * MD at time of publication
Adhesions Note:
• Complete obstruction typically
presents with acute abdominal
pain and related symptoms • Incomplete obstructions can present with either acute or
Congenital abnormality GI neoplasms
If partial obstruction: ↓ frequency of bowel movements
Since gas/air sounds hollow to percussion Abdomen tympanic to percussion
Mechanical obstruction: physical blockage of bowel lumen
Inflammatory bowel disease (IBD)
Gas (from swallowed air, bacterial fermentation, & CO2 made via HCO3- neutralization) & ingested gastro- intestinal (GI) contents accumulate before obstruction
Accumulated GI contents contain salts and other osmotically active solutes that osmotically draw water into the GI tract
Continued ↑ bowel distention & ↑ luminal pressure over time
↑ pressure squeezes shut intestinal blood vesselsà↓ bowel perfusion
chronic abdominal pain
If complete obstruction: Obstipation (no flatus) & absent bowel movements
Irritation of autonomic nerves in visceral peritoneum
Lower effective arterial blood volumeàdehydration
Continued peristalsis proximal to obstruction continues to push GI contents against the obstruction
If obstruction is proximal (closer to mouth), higher luminal pressure may force regurgitation of GI contents
Bloating, cramping, anorexia Diffuse visceral abdominal pain
Flat/low jugular venous pressure (JVP), resting tachycardia, orthostatic hypotension
Severe abdominal pain (may come in waves), peritonitis, guarding, rigidity
Hyperactive bowel sounds (proximal to obstruction) or absent bowel sounds (ileus)
Nausea/vomiting
Bowel ischemia and infarction, tissue necrosis, possible perforation +/- bacterial invasion (see relevant slides)
Legend:
Pathophysiology
Mechanism
Sign/Symptom/Lab Finding
Complications
Re-Published December 15, 2021 on thecalgaryguide.com