Background: The aim of the present study was to estimate, after vagotomy, the location and extension of residual vagal innervation of the gastric corpus mucosa by using the endoscopic Congo red test (ECRT) and its relation to recurrent ulcer (RU), as well as the results of quantitative gastric acid tests: basal acid output (BAO), maximal acid output (MAO), and nocturnal acid output (NAO).

Methods: A total of 271 consecutive vagotomized duodenal ulcer (DU) patients were studied 5 to 12 years (mean 8 years) after the operation. In all cases gastroscopy and ECRT were performed simultaneously. ECRT was considered positive if a red to black-blue (pH <3.0) color change of the gastric corpus mucosa occurred within the first 3 minutes, and the cases were classified as having small extension (SE), ie, one or more areas with a diameter of 1 to 30 mm, or large extension (LE), ie, 20% or more of the gastric corpus showing residual vagal innervation. No red to black-blue changes (pH >3.0) were attributed to negative ECRT. BAO, MAO, and NAO were determined preoperatively and postoperatively in 108 cases out of 271 and correspond with ECRT results.

Results: Recurrent ulcer occurred in 18 out of 135 ECRT-positive and in 1 out of 136 ECRT-negative cases. RU occurred 5 times more frequently in LE than SE cases (P <0.05). The postoperative mean values of BAO, MAO, and NAO were significantly higher in ECRT-positive than in ECRT-negative cases (P <0.001), and higher in LE than in SE cases (P <0.01; for NAO, P >0.05).

Conclusion: ECRT is a practical and reliable method in the evaluation of postvagotomy DU patients: Negative ECRT practically includes recurrent ulcer risk; positive ECRT of large extension is related to fivefold higher recurrent ulcer risk compared with ECRT of small extension; and ECRT reflects BAO, MAO, and NAO results and can be used instead of them as a less time-consuming procedure, which is more convenient for the patient.