Lecture Notes: Bowel Obstruction

Introduction to Bowel Obstruction

• Bowel obstruction is a lower gastrointestinal disorder.
• It is classified into two types:
  • Mechanical Bowel Obstruction
  • Non-Mechanical (Functional) Bowel Obstruction

Gastrointestinal Tract Function

• Food propulsion through the GI tract involves peristalsis and segmentation.
  • Peristalsis: Involves contraction of longitudinal, circular, and diagonal muscles to move food as a wave through the tract.
  • Segmentation: Involves longitudinal and circular muscles in the small intestine to move food back and forth, aiding in nutrient absorption.

Intestinal Obstruction Overview

• Involves a partial or complete blockage that prevents contents from passing through the intestine.
• Most common in the small intestine but can occur in the large intestine.

Classification of Bowel Obstruction

Mechanical Obstruction

• Physical blockage in the GI tract.
• Causes include:
  • Adhesions: Bands of scar tissue.
  • Hernias: Intestine trapped through the inguinal canal.
  • Intussusception: Telescoping of the bowel.
  • Neoplasms: Tumors.
  • Volvulus: Twisting of the bowel.

Non-Mechanical (Functional) Obstruction

• No physical blockage; characterized by a loss of peristalsis.
• Paralytic Ileus: Most common type, where the gut loses peristalsis.
• Causes include:
  • Inflammation (e.g., pancreatitis, peritonitis)
  • Post-surgery effects
  • Electrolyte imbalances (e.g., hypokalemia)
  • Medication effects (e.g., opioids)

Pathophysiology of Intestinal Obstruction

• Obstruction leads to gas and fluid accumulation proximal to the blockage.
• Mechanical Obstruction Pathophysiology:
  • Increased pressure in the lumen causing intestinal distension.
  • Strong contractions attempt to move the blockage.
  • Potential outcomes: ischemia, necrosis, perforation, peritonitis.

Clinical Manifestations

Mechanical Obstruction

• Early Signs:
  • Colicky abdominal pain
  • Hyperactive bowel sounds proximal to the obstruction
• Later Signs:
  • Abdominal distention
  • Vomiting
  • Absent bowel sounds in case of severe progression

Non-Mechanical (Functional) Obstruction

• Constant, steady abdominal pain
• Decreased or absent bowel sounds

Treatment

• Primary Treatment: Nasogastric tube (NG tube) insertion for bowel decompression.
• Surgery: Considered if NG tube does not resolve the obstruction.
• Fluid Replacement: Important during NG tube insertion.

Summary of Key Differences

• Mechanical vs. Non-Mechanical:
  • Cause: Physical vs. loss of peristalsis
  • Pain Type: Colicky vs. steady
  • Bowel Sounds: Hyperactive in early mechanical vs. decreased/absent in non-mechanical

Practice Questions

1. Mechanical Obstruction Causes:

   • Adhesions, volvulus, hernia

2. Sign of Mechanical Obstruction:

   • Colicky abdominal pain

These notes summarize the lecture on bowel obstruction, focusing on the classification, pathophysiology, clinical manifestations, and treatments of mechanical and non-mechanical bowel obstructions.