Why must a drainage procedure such as pyloroplasty or gastrojejunostomy always accompany a truncal vagotomy but not a highly selective vagotomy?

• A Truncal vagotomy abolishes gastrin release, causing gastric atony that requires bypass
• B Truncal vagotomy causes pyloric spasm through cholinergic hypersensitivity, while highly selective vagotomy abolishes it
• C Truncal vagotomy denervates the pylorus and antral pump, impairing gastric emptying, whereas highly selective vagotomy preserves the nerves of Latarjet to the antrum and pylorus ✓
• D Drainage is needed after truncal vagotomy only to allow access for future endoscopy

Explanation

Truncal vagotomy divides both vagal trunks at the diaphragmatic hiatus, denervating the entire abdominal foregut including the antrum and pylorus. Loss of vagal motor input to the antral pump and pylorus delays gastric emptying, so a drainage procedure is mandatory. Highly selective (proximal gastric) vagotomy divides only the parietal cell branches and preserves the nerves of Latarjet supplying the antrum and pylorus, so gastric emptying remains intact and no drainage is required. This preservation of antral innervation is precisely what distinguishes the two operations.

Reference: Sabiston Textbook of Surgery, 21st ed.

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