Prospective comparison of congo red and sham feeding testing to determine vagal innervation of the stomach.

The purpose of this study was to validate Congo red (CR) testing as a means of determining the status of vagal innervation of the stomach after gastric surgery by comparing it with the sham feeding test (SF). Twenty-six patients with previous gastric operations were studied prospectively. The operations were vagotomy/antrectomy (n = 14), vagotomy/antrectomy/Roux-en-Y anastomosis (n = 4), proximal gastric vagotomy (n = 3), vagotomy/pyloroplasty (n = 2), and antireflux (n = 3). In each case, the CR test was performed prior to the SF test so that the endoscopist was unbiased. The CR test solution was sprayed on the gastric mucosa through a wash catheter and immediately aspirated. A two-dimensional map of the endoscopist's conception of the red and black mucosa was drawn, and areas were calculated using a computerized scanner. The SF test was performed as described previously, with sham/peak ratios (sham feeding stimulated acid output [SAO]/peak acid output [PAO]) greater than 0.1 indicating a positive test, or incomplete vagotomy. The CR test was negative in 11 patients and positive in 15 patients. SF was negative in 16 patients (SAO/PAO of less than 0.1) and positive in 10 patients. The results correlated in 18 of 26 (69%) patients (p = not significant). Positive sham feeding tests and negative Congo red tests were more reliable, whereas negative sham feeding tests and positive Congo red tests were less reliable. Except patients with Roux-en-Y anastomosis, patients with negative or weakly positive CR tests did not have recurrent ulcers or other symptoms attributable to acid hypersecretion. The CR test was easier to perform and preferred by the patients. We conclude that both tests provide valuable clinical information and that both tests should be available in the evaluation of postgastrectomy patients.