Modified sham feeding and Congo red test in determining completeness of vagotomy

Gastric acid response to modified sham feeding was evaluated in 14 patients with duodenal ulcer prior to vagotomy and in 18 patients after vagotomy. Nine patients in the latter group had recurrent ulcer, suggesting inadequate vagotomy. Based on values in the 32 tests (14 pre and 18 postoperative), cut-off levels of six secretory indices were selected to provide a specificity of 1.00 for the presence of ulcer. When applied separately to the 18 postoperative patients and to the 13 patients who underwent the endoscopic congo red test, observed volume of 75 ml/h and peak volume of 90 ml/h following sham feeding gave specificity, sensitivity and efficiency of 1.00 each in determining inadequate vagotomy. The endoscopic congo red test done in 13 post-vagotomy cases showed a sensitivity of 1.00, and high specificity (0.89) and efficiency (0.92). Measurement of crude gastric juice response to modified sham feeding is a convenient bedside test to confirm inadequate vagotomy. The endoscopic congo red test is also useful, especially as a screening test, and has the added advantage that it can be used intra-operatively.