Although recent clinical studies suggest an association between Stamm gastrostomy and gastroesophageal reflux (GER), no significant experimental data is available. This study evaluates alterations in lower esophageal sphincter (LES) pressure after Stamm gastrostomy in cats. Eight male cats (average weight 3 to 4 kg) were induced under general anesthesia using 20/mg/kg ketamine intramuscularly (IM). Esophageal manometrics were determined for each animal using a continuous perfusion catheter and recording system. Three measurements were taken for each animal. Stamm gastrostomy was then placed in the anterior wall of the stomach two thirds of the way down from the fundus. This was tacked to the anterior abdominal wall 3.0 cm lateral to the midline at the appropriate longitudinal level. Esophageal manometry was repeated after abdominal closure. The animals were awakened and returned to their cages for ad libidum feedings. The animals were reanesthetized with ketamine and manometrics repeated at 7 and 14 days. Each animal served as its own control. Five animals underwent barium esophagram 14 days postoperatively to evaluate for GER. Preoperative mean LES pressure measured 11.4 +/- 3.5 torr. This decreased to 7.8 +/- 2.8 torr immediately after Stamm gastrostomy (P less than .025). When evaluated at 1 and 2 weeks after gastrostomy, further decrease in LES pressures to 6.6 +/- 1.6 torr and 4.8 +/- 1.6 was observed (P less than .02 v preoperative). Three of five cats undergoing barium swallow demonstrated significant reflux radiographically. Stamm gastrostomy caused significant reduction of the LES pressure in all cats studied. This resulted in clinical GER as documented by barium swallow in three of five cats.(ABSTRACT TRUNCATED AT 250 WORDS)