**Core Concept**
Vagotomy is a surgical procedure that involves cutting or disrupting the vagus nerve, which is responsible for transmitting parasympathetic signals to various abdominal organs, including the stomach, pancreas, and gallbladder. The vagus nerve plays a crucial role in regulating digestive functions, such as gastric secretion and motility.

**Why the Correct Answer is Right**
The most common complication of vagotomy is gastric stasis, which occurs due to the loss of parasympathetic innervation to the stomach. This leads to decreased gastric motility and secretion, resulting in nausea, vomiting, and abdominal distension. The vagus nerve stimulates the release of gastrin, which in turn stimulates the parietal cells to secrete gastric acid and pepsin. Without vagal stimulation, gastrin release is reduced, leading to decreased gastric acid secretion and potentially causing complications such as gastric stasis.

**Why Each Wrong Option is Incorrect**
**Option A:** Gastric cancer is not a direct complication of vagotomy, although it may be a risk factor for patients undergoing surgery for peptic ulcer disease.
**Option B:** Diarrhea is not typically associated with vagotomy, as the vagus nerve primarily regulates gastric secretions and motility, rather than intestinal function.
**Option C:** Weight gain is not a common complication of vagotomy, as the procedure typically results in decreased gastric acid secretion and potential malabsorption of nutrients.

**Clinical Pearl / High-Yield Fact**
Gastric stasis is a well-known complication of vagotomy, and its management often requires the use of prokinetic agents, such as metoclopramide, to stimulate gastric motility.

**Correct Answer: B. Diarrhea is not typically associated with vagotomy, as the vagus nerve primarily regulates gastric secretions and motility, rather than intestinal function.**