Somatostatin inhibits gastroenteropancreatic exocrine secretion and is often used after pancreaticoduodenectomy to reduce pancreatic secretion to minimize tissue damage and pancreatic stump complications. Because our earlier clinical work saw a major increase in delayed gastric emptying (DGE) with somatostatin prophylaxis after pylorus-preserving pancreaticoduodenectomy (PPPD), this small-group study was designed to confirm or disprove that observation. From August 1997 to December 2000, a total of 23 post-PPPD patients were randomized to receive somatostatin prophylaxis [somatostain (+)] (n = 11) or not [somatostatin] (-) (n = 12). The incidence of DGE, scintographic solid-phase emptying results on day 14 postoperatively, and sequential fasting plasma motilin levels were compared, as motilin levels are related to both gastric motility and somatostatin levels. The somatostatin(+) group exhibited greatly increased patient complaints of DGE: 9 of 11 (82%) versus 3 of 12 (25%) in the somatostatin(-) group. Radiologic scintography showed somatostatin prophylaxis prolonged the half-time (T(1/2)) of solid-phase emptying: 144.5 +/- 51.4 minutes for somatostatin(+) versus 89.0 +/- 59.9 minutes for somatostatin(-) (p < 0.001). Comparing pre-PPPD and post-PPPD plasma motilin levels prior to somatostatin infusion, motilin decreased 80% in reaction to the surgery. For somatostatin(-) patients, motilin levels oscillated, or "rang," postoperatively, reaching a higher level on day 3, declined to a new record minimum on day 7, and by day 21 were 50% of the original and the slope of the recovery curve was increasing well. In somatostatin(+) patients the same ringing pattern was observed but decreased with motilin levels 30% to 70% lower than in the somatostatin(-) patients. By day 21 somatostatin(+) motilin levels were recovering but still only 20% original levels, and the slope of the recovery curve was not optimistic. On postoperative day 14 the plasma motilin levels (below approximately 6 bg/ml) correlated strongly with DGE for both groups. Despite the small sample size, the results indicated that (1) somatostatin prophylaxis significantly decreases fasting plasma motilin; (2) somatostatin prophylaxis produces lingering suppression of plasma motilin; (3) PPPD surgery itself significantly reduces fasting motilin levels with recovery to 50% normal at day 21; (4) the mechanism of somatostatin-induced DGE seems related to reduced fasting plasma motilin levels.