The insulin test after vagotomy and antral resection or drainage. Stability and reversal of test response in repeated tests.

Repeated insulin tests were carried out on 118 patients after vagotomy and antral resection or vagotomy and drainage. The main indication for operation was gastro-duodenal ulcer. The test was performed in both the early (average 13.7 days after the operation) and late (average 3.3 years) postoperative phase. After vagotomy and antral resection, the proportion of Hollander-positive responses decreased from 21.1% in the early phase to 11.1% in the late phase, but after vagotomy and drainage, it increased from 32.1% to 57.1% (p greater than 0.05 in both). Changes of the test response from negative to positive and vice versa were seen after both types of operations. After vagotomy and antral resection, in tests with a change of the response from positive to negative (14.4%) there was a significant decrease in insulin-stimulated acid secretion. After vagotomy and drainage, there were more changes from negative to positive (28.6%), but no significant differences were seen in acid secretion values. Some tests showed a change from early positive to late positive (Ross & Kay). The significance and possible explanations for the changes are discussed in the light of acid secretion values.