Leveling the learning curve for laparoscopic bariatric surgery.

BACKGROUND: The learning curve for laparoscopic bariatric surgery is associated with increased morbidity and mortality. METHODS: The study included the first 100 patients undergoing laparoscopic Roux-en-Y gastric bypass (LGB) by a designated surgical team. Surgeon A operated as primary surgeon, with surgeon B assisting (Stage 1). Surgeon B learned LGB in stages: exposure and jejunojejunostomy (stage 2), gastric pouch (stage 3), gastrojejunostomy (stage 4), and sequence all steps (stage 5). RESULTS: Surgeon A achieved confidence with LGB after 20 cases and surgeon B after 25 cases (stage 2), 18 cases (stage 3), 21 cases (stage 4), and 16 cases (stage 5). Complications (8%) included small bowel obstruction (three); pulmonary embolus (two), and leak, stomal stenosis, and gastrogastric fistula (one each). There was a decreasing trend for operative duration, length of stay, and complications across the five stages (p < 0.05). CONCLUSIONS: By transferring skills in stages, a laparoscopic bariatric program can be established with minimal morbidity and mortality.

Duodenal fat intensifies the perception of heartburn.

BACKGROUND: Patients with gastro-oesophageal reflux disease (GORD) frequently report that meals high in fat worsen heartburn. Nevertheless, studies to determine whether high fat meals promote gastro-oesophageal reflux have produced conflicting and equivocal conclusions. PATIENTS AND METHODS: To determine, alternatively, whether fat in the small intestinal lumen intensifies the perception of heartburn, we studied 11 patients with typical heartburn from GORD. After being placed on omeprazole to suppress endogenous acid, these fasting subjects underwent oesophageal perfusions with graded doses of HCl at pH values of 1.0, 1.5, 2.0, and 2.5. Oesophageal perfusions were conducted while the duodenum was perfused with saline (control) and again with fat at 8 g/h. RESULTS: Time to onset, intensity, and severity of heartburn varied with dose of oesophageal acid (p<0.01). Time to onset was significantly (p<0.01) shorter, and intensity and severity of heartburn significantly (p<0.05) greater, during duodenal perfusion with fat. CONCLUSION: We conclude that duodenal fat intensifies the perception of heartburn.

Postcibal gastric emptying of pancreatin pellets: effects of dose and meal oil.

To treat pancreatic exocrine insufficiency, physicians often prescribe enterically coated pellets of pancreatin to be taken with meals. The pellets are only partially effective in correcting the digestion and absorption of fat. We sought to determine in normal subjects whether emptying of pellets from the postcibal stomach was dose-related and whether the gastric emptying of lipophilic Creon-20 or Pancrease was altered by the presence or the absence of oil in a meal. Gastric emptying of pellets surface-labeled with 113mIn or 99mTc was followed with a gamma camera for 300 min after isocaloric meals. From our observations, we concluded that gastric emptying of 0.28-1.12 g of 1-mm or 2-mm pellets was dose-related (P < 0.01) and emptying of neither Creon-20 nor Pancrease was much affected by oil in the meal.

Dilutions of low- vs. high-fat diets on intakes and gastric volumes in rats.

Rats adapt to changes in dietary energy to maintain nearly constant energy intakes. This regulation indicates that animals sense and respond to nutrient content. We sought to determine whether this response was affected by the fat content of the diet. Our second goal was to determine how energy dilution affected intragastric volumes. Rats were randomized to high (18% w/w) and low fat (4.5% w/w) as the energy density of the diet was altered from 2.0 to 3.5 kcal/g. Average energy intake during 7-h feeds rose steeply (P<.01) when density was increased from 2.0 to 3.0 kcal/g, but modestly as density increased from 3.0 to 3.5 kcal/g. In other rats on 18% vs. 32% fat diets, energy intakes increased significantly (P<.01) as density of the diet was raised from 3.5 to 4.5 kcal/g. During diets at 2.0 and 2.5 kcal/g, animals on 18% fat ate fewer kilocalories than those on 4.5% fat; but over 3.0-4.5 kcal/g, energy intake was similar regardless of fat concentration (4.5-32%). Gastric contents after 7-h feeds increased with grams of food ingested similarly for high- and low-fat diets. We concluded that in rats: (a) compensation to energy dilution or concentration was inexact but (b) was about equal for high- vs. low-fat diets; thus, high fat was as well sensed as high carbohydrate; (c) compensations for energy densities were made despite varied gastric volumes; thus, rats learned to override the stimulus of gastric stretch and to sense energy via extra gastric mechanisms.

Gastric emptying of indigestible versus digestible oils and solid fats in normal humans.

Recent scintigraphic studies indicate that lipolytic products in the small intestine do not inhibit gastric emptying of fat as potently as previously suggested by studies that compared a liquid indigestible oil with a solid digestible fat. The older studies left open the confounding possibility that solid fats emptied differently than liquid oil. We studied eight normal subjects who ingested four meals in which fat was (1) liquid, digestible Crisco oil, (2) liquid, indigestible sucrose polyester oil, (3) digestible, solid Crisco, and (4) indigestible, solid olestra. Fats were labeled with iodine-123, and their gastric emptying was followed with a gamma camera. Indigestible fats (whether liquid or solid) emptied consistently faster than digestible fats (P < 0.005), although differences were small. Solid fats emptied about as rapidly as oils in the first hour; but more slowly thereafter (P < 0.01). A comparison of present scintigraphic with older studies suggested that solid fats were not well tracked by duodenal, marker-perfusion techniques, which misled previous investigators.

Accuracy of ultrasonic pachymetry and videokeratography in detecting keratoconus.

PURPOSE: To compare the accuracy of ultrasonic pachymetry measurements and videokeratography-derived indices in distinguishing keratoconus patients from those with normal eyes. SETTING: A subspecialty cornea practice (Los Angeles, California, USA) and the Keratoconus Genetics Research Project. METHODS: Corneal thickness was measured by ultrasonic pachymetry at the center and inferior margins of the pupil of 142 normal and 99 keratoconus patients The corneal surface topography of patients was studied with the Topographic Modeling System (TMS-1). The videokeratographs obtained were analyzed with a computer program that automatically calculates two indices derived from data points in the central and paracentral cornea: central K and I-S values. Linear discriminant analysis was used to determine the correct classification percentages using pachymetry measurements and indices derived from videokeratography as the independent variables. RESULTS: The range of corneal thickness in normal and keratoconic eyes overlapped considerably. In the discriminant analysis, videokeratography indices provided a 97.5% correct classification rate and pachymetry data, an 86.0% rate (P < .01, McNemar's test). CONCLUSION: Keratoconus is more accurately distinguished from the normal population by videokeratography-derived indices than by ultrasonic pachymetry measurements. This may be due to the large variation in corneal thickness in the normal population or the inability of ultrasonic pachymetry to accurately detect the location of corneal thinning in keratoconus by measuring standard points on the cornea. Pachymetry should not be relied on to exclude or diagnose keratoconus because the false-negative and false-positive rates are unacceptably higher than those obtained by videokeratography.

Gastric emptying of oil from solid and liquid meals. Effect of human pancreatic insufficiency.

Digestion of fat in pancreatic insufficiency (PI) is strongly affected by how rapidly fat enters the duodenum. We postulated that: (1) oil empties faster in PI than in normals and (2) in both, it empties in a load-dependent fashion. We used a gamma camera to test these ideas by comparing gastric emptying of iodine-123 iodinated oil in normal and pancreatic-insufficient subjects after 15 g of free oil were ingested in a small spaghetti meal and 60 g of oil were ingested in a large spaghetti meal and in a milk emulsion. Indium-113m marked gastric emptying of water in the milk. In both groups after all meals, oil emptied fastest initially, slowing later; and oil emptied three to four times faster when 60 g vs 15 g were ingested. There were no significant differences between the groups of subjects with respect to gastric emptying of the spaghetti meals, but the pancreatic-insufficient subjects emptied both oil and water faster from the milk emulsion than did the normal subjects. The slower emptying of oil in the normal subjects was associated with significantly more layering of oil to the top of the intragastric milk emulsion.

Videokeratography database of normal human corneas.

AIM: To form a database of videokeratography patterns and quantitative indices describing normal human corneas using the absolute scale. METHODS: Both eyes of 195 normal subjects were examined with a TMS-1 videokeratoscope. Videokeratographs were divided into 10 categories based on a classification scheme devised from the absolute scale and analysed with 10 quantitative indices devised to describe phenotypic features of keratoconus videokeratographs. Correlations were sought between videokeratograph patterns and quantitative indices. Additionally, data were analysed for differences in age, sex, and ethnicity. RESULTS: For symmetric videokeratography patterns, analysis in the absolute scale was similar to a previous study done in the normalised scale. In the asymmetric categories, analyses differed markedly. Using the absolute scale and our classification scheme more variation in normal videokeratography patterns could be appreciated. There was good correlation between quantitative indices and videokeratography patterns. Neither videokeratography patterns nor indices differed significantly between sex, ethnic groups, or age using two way analysis of variance. CONCLUSIONS: Pattern analysis of videokeratographs in the absolute scale using, a standard classification scheme, may be more useful in trying to determine whether a cornea is normal or represents subtle early disease than analysis in the normalised scale. Quantitative indices could remove the subjectivity from the decision making process thus facilitating universal reproducibility of videokeratography data interpretation.

Bile salt inhibits acid-promoting feeding tube occlusion.

Occlusion of feeding tubes is a common and costly complication of enteral feeding. Although the composition of feeding formulas, the size, design, and material of the feeding tube, and the rate of delivery have been considered as factors that determine the rate of tube occlusion, little information is available on the effect of the luminal content of the gut on tube occlusion. Enteral feeding tubes are placed either in the stomach or postpylorically, in the small intestine. The chemical composition of these regions including acidity and bile salt concentration may vary. Since acidity has been shown to promote tube occlusion and bile salts have detergent-like properties, these chemical differences in the luminal environment may be important to tube occlusion. To test the idea that bile salt inhibits acid-promoted occlusion of feeding tubes, in an in vitro study, we compared the time-to-complete occlusion of four groups of formula-filled feeding tubes (six tubes in each group) immersed in an acidic solution (pH 3.0) containing 0 (control), 10, 20, or 40 mM of taurocholate. We found that although 33% of the feeding tubes were occluded within 12 hours in the absence of exposure to bile salt, none were occluded when 20 or 40 mM of taurocholate was added to the acidic solution. After 24 hours, 40 mM of taurocholate inhibited acid-promoted occlusion of 67% of the feeding tubes. Thus 0 to 40 mM of taurocholate still inhibited acid-promoted tube occlusion in a dose-dependent fashion (p < .05). Acidity and the concentration of bile salt may work together, but in opposite directions, as luminal factors that determine the rate of occlusion of feeding tubes.

Upper gastrointestinal hemorrhage clinical--guideline determining the optimal hospital length of stay.

PURPOSE: Physicians lack objective outcome data to define the medically appropriate length of stay (LOS) for patients hospitalized with acute upper gastrointestinal hemorrhage (UGIH), resulting in wide variations in resource utilization and quality of care. A clinical practice guideline with the ability to assign relative risk for adverse events is proposed. METHODS: A comprehensive scoring system was derived from the literature by using four variables; hemodynamics, time from bleeding, comorbidity, and esophagoduodenoscopy findings. The discriminatory ability, potential safety, and impact on resource utilization of the clinical practice guideline was measured in a retrospective, observational study. RESULTS: Seventy percent of UGIH patients (349 of 500) achieved low-risk status according to the guideline, and, were therefore potentially suitable for early discharge from the hospital. If low-risk patients were discharged based upon the guideline, mean (+/- SD) hospital LOS would have been decreased from 4.8 +/- 2.4 days to 2.7 +/- 1.4 days; mean reduction was 2.1 bed-days per patient (95% CI 1.8 to 2.3, P <0.001). LOS would have increased in 4% of cases. Adopting the guideline's recommendation of early discharge would have resulted in a 0.6% (95% CI 0.07 to 2.1) complication rate, with no worsening of quality of care, as judged by implicit review. CONCLUSIONS: The proposed clinical practice guideline may safely reduce hospital LOS for selected low-risk patients with acute UGIH. Moreover, it also may reduce premature discharge of high-risk patients prone to life-threatening events.

Frequency of gastric pacesetter potential depends on volume and site of distension.

Little is known about the response of the frequency of gastric pacesetter potential (PP) to luminal distension. When volume distension occurs as a result of a meal, gastric emptying may play an important role, since the site of distension shifts as the meal is displaced from the stomach to the small bowel. In this study, using does equipped with duodenal fistulas and serosal electrodes on the antrum, we compared the frequency of gastric PP during the course of gastric emptying while isolating the volume distension to either the stomach or the small bowel. We found that 1) the frequency of gastric PP decreased linearly with greater initial meal volume when volume distension was isolated to either the stomach -P<0.05, analysis of variance (ANOVA)- or small bowel (P<0.01, ANOVA), and 2) the frequency of gastric PP decreased linearly with increased volume remaining in the stomach or increased volume entering the small intestine. We conclude that the frequency of gastric PP depends on the volume and site of distension.

Bile salt-dependent inhibition of gallbladder emptying.

Little is known about the inhibitory controls of gallbladder emptying. Since cholestyramine, a binding agent that reduces luminal concentration of bile salt, has been reported to accelerate gallbladder emptying, suggesting that bile salt is inhibitory, we hypothesized that fat-stimulated gallbladder emptying is inhibited by a bile salt-dependent mechanism. To test this idea, we compared gallbladder emptying in 10 dogs equipped with duodenal and jejunal fistulas that allowed for complete diversion of the native bile while varying concentrations of bile salt were perfused into the small intestine. In six dogs, 30 mM oleate and 5, 10, or 20 mM sodium taurocholate was perfused into the whole intestine. Since bile salt availability alters fat absorption, in a separate experiment in seven dogs we also compared gallbladder emptying while 30 mM oleate and 5 mM taurocholate were perfused between fistula and 0, 5, 10, or 20 mM taurocholate were perfused beyond jejunal fistula to separate fat from varying concentrations of bile salt. We found that intestinal taurocholate inhibited fat-stimulated gallbladder emptying in a dose-dependent fashion (P < 0.01; analysis of variance, significant linear dose effect) and that the inhibitory effect of bile salt persisted when 5-20 mM taurocholate was perfused beyond the jejunal fistula (0 vs. average of 5-20 mM taurocholate, P < 0.05, paired t-test). We conclude that fat-stimulated gallbladder emptying is inhibited by a bile salt-dependent inhibitory mechanism.

Isogravitational heterogeneity of perfusion after unilateral lung transplantation.

1. Single-photon emission computerized tomography in both an intact canine model and man has demonstrated an aspect of pulmonary perfusion to be independent of gravitational forces. 2. Using technetium 99m-labelled macroaggregated albumin single-photon emission computerized tomographic imaging, we investigated normal human subjects (n = 5), stable unilateral lung transplant recipients (n = 6) and transplant recipients with chronic allograft dysfunction related to obliterative bronchiolitis (n = 5). 3. In coronal isogravitational sections, a 1 x 1 x N pixel strip (medial to lateral) was constructed through the 'core' pixel of maximal radioactive counts. The counts were measured for the 'core' pixel and at two mid-points (medial and lateral) between the core pixel and the lung edges. Coefficients of variation were computed for each isogravitational strip and compared between groups. Fractional whole-lung perfusion was determined for left versus right lungs of normal subjects and allograft versus native lungs of transplant recipients. 4. Using these indices, 'isogravitational heterogeneity' (i.e. increased 'core' versus peripheral perfusion) was observed in allografts and native diseased lungs after unilateral transplantation. Despite significantly increased fractional whole-lung perfusion directed to the allografts (84.8% +/- 3.0% and 75.8% + 12.1% for stable unilateral lung transplant recipients and patients with obliterative bronchiolitis respectively) compared with normal lungs (50.2% +/- 1.2% and 49.8% +/- 1.2% for left and right respectively), 'isogravitational flow heterogeneity' (i.e. increased 'core' versus peripheral perfusion) was preserved after transplantation. 5. These findings suggest that 'isogravitational heterogeneity' was maintained despite increased unilateral pulmonary perfusion and the presumed increase in pulmonary capillary recruitment and/or distension.

Bronchiolitis obliterans in single-lung transplant recipients.

The presentation and clinical course of bronchiolitis obliterans (BO) in single-lung transplant (SLT) recipients has thus far not been well described. We retrospectively analyzed the serial spirometry of 15 SLT patients with BO. All the patients fulfilled the criteria for BO syndrome, and 11 of the 15 had histologically documented BO. Based on serial FEV1 analysis, we identified three patterns of presentation and progression of BO. The first pattern (n = 6) was characterized by a rapid onset and a relentless progressive course; the second pattern (n = 5) was characterized by a similar rapid onset and initial rapid decline, but was followed by stabilization in lung function; the third pattern (n = 4) was characterized by an insidious onset and course. In all patients, a permanent reduction in the mean forced expiratory flow during the middle half of the forced vital capacity appeared to be an early sensitive index for the development of BO. An appreciation of these different modes of presentation and progression of BO is potentially important in the assessment of prognosis and management of the SLT recipient.

The relationship between oxygen consumption and work rate in patients with airflow obstruction.

The oxygen cost of augmented ventilation is increased in patients with chronic obstructive pulmonary disease, either at rest or during exercise. Thus, if excessive demands are placed on the respiratory muscles during exercise in these patients, we postulate that the total oxygen consumption (VO2) may increase relative to the work rate compared to control subjects. The aim of this study was to examine the relationship between VO2 and work rate during exercise in patients with airflow obstruction. A retrospective analysis of data collected over 7 years was conducted. Patients with airflow obstruction (n = 131) were compared and contrasted with those in whom pulmonary function studies (spirometry, lung volumes) were normal (n = 199). Severity of airflow obstruction (ie, mild moderate, severe) was determined, using the 95 percent confidence limits for the ratio of FEV1 to FVC. Incremental exercise studies were performed on a cycle ergometer. Resting VO2 was not significantly different across the groups with airflow obstruction measured either directly or normalized for body weight. The VO2max was significantly reduced in the patients with severe airflow obstruction, compared with the normal group, as well as the patients with mild and moderate airflow obstruction. No differences were noted in the slope of VO2 plotted against work rate in the patients with airflow obstruction (regardless of the severity of the obstruction) and individuals in whom results of pulmonary function tests were normal. In addition, when gender was taken into account, there was essentially no difference in the slopes for either male or female subjects across all groups. Stepwise, linear regression failed to demonstrate any variable or variables that were strongly related to slope. We postulate that the maintenance of a normal slope of VO2 on work rate in patients with airflow obstruction, in whom the oxygen cost and work of breathing is likely increased, may mask a significant reduction in nonrespiratory VO2 (for example, to exercising skeletal muscles).

Control of canine gastric emptying of fat by lipolytic products.

Dietary fat is ingested in three forms: 1) in solid food, 2) as aqueous emulsions, and 3) as unemulsified, liquid oil. On the basis of a scant previous literature, we postulated that liquid fat (emulsions or oils) would empty from the stomach at speeds that varied with the amounts ingested but that this dynamic would be modulated by feedback inhibition from lipolytic products. To test these ideas, we used a gamma camera to track gastric emptying of 123I-labeled fat in dogs with chronic pancreatic fistulas by which lipase was excluded from or replenished in the duodenum in varied amounts after dogs were fed 15-, 30-, and 60-g loads of liquid fat given with solid foods or as emulsions. We also tracked concurrent gastric emptying of 113mIn, which marked the solid food phase or the water phase of emulsions. In some studies, we used a potent and specific inhibitor (orlistat) of pancreatic and gastric lipases to assess how lipolytic products modulated emptying of liquid fat. In the absence of pancreatic enzymes, both oils and emulsions emptied initially at high speeds that varied with fat loads, but emptying slowed 20 min after ingestion of emulsions and 60 min after ingestion of unemulsified oil. Studies with orlistat indicated that these changes in rates resulted from liberation of gastric lipolytic products. Emptying of oil emulsions was not altered by duodenal replenishment with pancreatic enzymes, but emptying of unemulsified oil was inhibited in a dose-related fashion, such that maximal inhibition was achieved when pancreatic enzymes were replenished at > or = 40% of normal amounts. Studies with orlistat confirmed that this dose-dependent slowing was due specifically to lipase. Emptying of solid food was much more sensitive to replenishment with enzymes, so that a 10% replenishment maximally inhibited solid emptying.

Stimulation of duodenal motility by hyperosmolar mannitol depends on local osmoreceptor control.

Duodenal motility is stimulated by hyperosmolar solution. Since intestinal distension also stimulates intestinal motility, this increase in the motility response may be due to either stimulation of duodenal local osmoreceptor control or intestinal distension resulting from osmotic equilibration. To test which mechanism is primarily responsible for this osmotically sensitive effect, we compared the number of duodenal spike bursts in five dogs equipped with duodenal fistulas that allowed for the preservation or removal of intestinal distension. The response to 300 vs. 1,200 mosM mannitol was compared under three experimental perfusion methods: 1) distension was preserved both proximal and distal to the fistula (DD); 2) distension proximal to the fistula was removed (rD); and 3) distension both proximal and distal to the fistula was removed (rr). The test solutions had access to either the whole gut (DD and rD) or only the first 10 cm of the duodenum (rr). We found that 1) there were more spike bursts after the hyperosmolar solution (dose effect, P < 0.05, analysis of variance); 2) there was no significant difference between the three experimental methods; and 3) the stimulating effect of hyperosmolar solution depended on the first 10 cm of the duodenum. Thus, since hyperosmolar solution increased duodenal motility regardless of whether intestinal distension was preserved or removed, the stimulating effect of hyperosmolar solution on duodenal motility was primarily the result of a local osmoreceptor control mechanism located in the first 10 cm of the duodenum.

Disproportionate ileal digestion on canine food consumption. A possible model for satiety in pancreatic insufficiency.

In animals, ileal sensors of nutrients signal satiety more potently than similar sensors in jejunum. We postulated that inadequate food intake and weight loss in human pancreatic insufficiency might arise by the displacement of digestion to ileum, where excessive release of digestive products would enhance satiety. To test this idea, we studied dogs prepared with pancreatic fistulas, which allowed reversible switching of pancreatic juice from entry at duodenum to entry at mid-small intestine. Dogs were studied in a crossover design over successive eight-day periods. Food consumption and body weight were measured while the dogs had continuous access to food. Diversion of pancreatic juice to mid-intestine significantly (P < 0.01) depressed food intake by an average of 28%. Diversion also significantly (P < 0.01) reduced body weight. The findings support the idea that insufficient food intake in human pancreatic insufficiency may result from stimulation of ileal satiety mechanisms.

Prediction of maximal exercise capacity in obstructive and restrictive pulmonary disease.

We evaluated the predictive value of resting pulmonary function tests (PFTs) in the determination of maximal exercise capacity in patients with obstructive and restrictive ventilatory disease. We performed resting PFTs and an incremental exercise study on a bicycle ergometer in 146 patients with chronic obstructive pulmonary disease (COPD) and 68 patients with restrictive disease. The patients with obstructive disease were further subdivided into mild, moderate, and severe based on the severity of their airway obstruction (mean +/- SD:FEV1, 2.78 +/- 0.77, 2.12 +/- 0.74, and 1.06 +/- 0.47, respectively). Correlation coefficients for PFTs vs VO2max and VEmax in restricted patients was generally low (DL = 0.67 and 0.34, IC = 0.58 and 0.35, FVC = 0.57 and 0.35, TLC = 0.35 and 0.18). In patients with COPD, the maximum voluntary ventilation (MVV) was the single best predictor of VO2 in all groups with correlation coefficients of 0.75, 0.69, and 0.89 in the mild, moderate, and severe subgroups, respectively. Similarly, the MVV was the best predictor of VEmax in all groups with correlation coefficients of 0.59, 0.64, and 0.89 in the three subgroups. The correlation with FEV1 was slightly less for both VO2max (0.69, 0.65, and 0.87) and VEmax (0.52, 0.64, 0.64) in the mild, moderate, and severe subgroups, respectively. Our findings show that PFTs are unreliable in predicting VEmax and VO2max in restricted patients. In patients with obstruction, the MVV is the single best predictor of VO2max and VEmax in all three categories, but was not significantly improved by stepwise multiple regression with additional PFT variables. Higher correlations were obtained in the severe group in whom the correlation with VO2max and VEmax was 0.89. However, the 95 percent confidence interval of the estimate for VO2 and VE was relatively large (+/- 0.16 L/min and +/- 6.6 L/min, respectively). We conclude that although several PFTs correlate significantly with maximum exercise, the large variance precludes their use to accurately predict maximum performance in individual patients with COPD.

Nutrient feedback inhibition of gastric emptying plays a larger role than osmotically dependent duodenal resistance.

The slowing of gastric emptying by hyperosmolar solutions has been postulated to result from the triggering of duodenal osmoreceptor feedback on the stomach. We tested the idea that the inhibition of gastric emptying by a hyperosmolar solution depended on the duodenal resistance and the triggering of nutrient-specific feedback by tracking gastric emptying of 300 and 1,200 mosmol/kgH2O test solutions in 12 dogs in which duodenal resistance was either removed (by temporarily diverting chyme from uncorked duodenal fistula) or preserved (by keeping duodenal fistula corked). Mannitol was used to test osmolality alone, and glucose was used to examine the combined effects of osmolality and nutrient-specific inhibitory feedback. We found that: 1) the slowing effect of hyperosmolality was more marked with the duodenal resistance preserved (P < 0.05; analysis of variance), 2) the slowing effect of glucose was greater than that of mannitol for all conditions (P = 0.01; analysis of variance), and 3) the inhibitory effect of mannitol was localized to the duodenum. We conclude that inhibition of gastric emptying by hyperosmolar mannitol depended primarily on duodenal resistance, while the inhibitory effect of hyperosmolar glucose depended on nutrient-specific feedback on the stomach more than duodenal resistance.