We undertook a comparative survey of gastric emptying (GE) kinetics after two variants of bypass surgery for upper bowel obstruction. In 10 dogs with experimental upper bowel obstruction, five were randomized to obtain gastrojejunal anastomosis (GA), and the other five received Roux-en-Y duodenojejunal anastomosis (DA). Duplicate scintigraphic measurements of GE of a solid meal were accomplished in every animal before surgery and during the early (2-3 weeks), medium (3 months), and late (6 months) post-operative period. The GE curves were fitted with a power-exponential function to derive the GE half time T½, and the curve shape parameter S. Early after surgery T½ slightly decreased by -18±21 min in the DA group and lengthened by 91±37 min in the GA group (p = 0.042). In both groups an increase in the S parameter was found then. In either group T½ gradually declined towards the basal value during the medium and late post-operative period. On the other hand, net differences relative to the basal situation in the S values appeared to be positive in the GA group (0.32±0.11 at 3 months; 0.64±0.19 at six months), and negative in the DA group (-0.30±0.09 at 3 months; -0.01±0.20 at six months). Hence a statistically significant contrast was found between those differences: p = 0.0022 at 3 months, and p = 0.045 at six months after the surgery. Roux-en-Y duodenojejunal anastomosis appears to be superior to the classical gastrojejunal anastomosis while restoring patency of the gastrointestinal passage in the case of upper bowel obstruction.