Intestinal Obstruction I: Introduction

Mechanical obstruction results from a physical blockage preventing intestinal contents from passing through the lumen. Functional obstruction, or paralytic ileus, involves a temporary loss of intestinal motility without structural blockage. While the lumen remains open in functional obstruction, impaired peristalsis causes gas and fluid accumulation, leading to bowel distension and discomfort.

Adhesions are fibrous bands that form between normally separate anatomical surfaces, often after abdominal surgery or inflammation. These bands can tether loops of bowel to each other, to the peritoneum, or to adjacent organs, causing kinking or compression that predisposes the intestine to obstruction.

Intussusception occurs when one segment of the intestine slides into an adjacent segment, causing luminal narrowing and obstruction. Volvulus involves a loop of the small or large intestine twisting around itself, cutting off the flow of digestive contents and potentially compromising blood supply to the affected segment.

A hernia is the protrusion of an organ or tissue, usually intestine or omentum, through a weakness in the abdominal wall. When herniated tissue becomes trapped, it risks obstruction and ischemia if blood supply is compromised, potentially causing serious complications requiring prompt intervention.

Paralytic ileus commonly develops after abdominal or pelvic surgery due to manipulation of the intestines and effects of anesthesia. It may also result from medications such as opioids that reduce gastrointestinal motility, or from bowel ischemia, electrolyte disturbances, and systemic infections that impair intestinal neuromuscular function.

Intestinal obstruction disrupts the normal flow of intestinal contents through the lumen, impairing digestion and nutrient absorption. This interruption also affects fluid balance and may lead to serious complications if not treated promptly, as gas and fluid accumulate proximal to the blockage.

Neoplasms, especially malignant tumors, can narrow the intestinal lumen or compress it externally, leading to obstruction. This mechanical blockage is particularly common in the large intestine and represents a significant cause of mechanical obstruction in certain patient populations requiring clinical intervention.