Most common cause of small intestine obstruction
**Core Concept**
Adynamic ileus, mechanical obstruction, and other pathologies can lead to small intestine obstruction. The small intestine is a long, thin, and narrow tube with a large surface area, making it susceptible to obstruction due to various causes.
**Why the Correct Answer is Right**
The most common cause of small intestine obstruction is adhesions. Adhesions are bands of fibrous tissue that form between loops of intestine or between the intestine and adjacent organs, often as a result of previous surgery (e.g., appendicitis, cholecystectomy, or abdominal trauma). These adhesions can lead to mechanical obstruction by constricting the lumen of the intestine, preventing the normal passage of intestinal contents. The exact mechanism involves the formation of a fibrotic band that contracts, thereby reducing the diameter of the intestine and causing obstruction.
**Why Each Wrong Option is Incorrect**
**Option A:** Volvulus is a type of mechanical obstruction, but it is less common than adhesions. It typically occurs in the sigmoid colon or the cecum, rather than the small intestine.
**Option B:** Intussusception is a condition where a portion of the intestine telescopes into another portion, causing obstruction. However, it is more common in children and is less frequent in adults compared to adhesions.
**Option C:** Hernias can cause small intestine obstruction, but they are less common than adhesions. Hernias occur when a portion of the intestine bulges through a weakened area in the abdominal wall.
**Clinical Pearl / High-Yield Fact**
The "Ochsner classification" is a useful mnemonic to remember the causes of small intestine obstruction, which are: adhesions (most common), hernias, volvulus, intussusception, and other miscellaneous causes (such as tumors, foreign bodies, or internal hernias).
**Correct Answer:** A. Adhesions.