Are the temporal Inconsistencies of proximal stomach counts Indicative of Intragastric food redistribution?

Objectives: It is generally accepted that the changing intragastric locus of labeled food during scintigraphic gastric emptying studies is adequately addressed by use of the geometric mean of anterior and posterior region-of-interest (ROI) counts. Fundic accommodation has been identified as possibly playing a role in explaining symptoms in upper GI dysmotility disorders, whereby impaired relaxation could result in rapid filling, and thus premature distention, of the distal stomach. However, current standard 4-hr gastric emptying scintigraphy does not address fundic function and there is currently no standard methodology for quantifying fundic emptying. The aim of this study was to characterize the proximal gastric distribution of a meal, as well as fundic function parameters in normal subjects.

Methods: 24 healthy volunteers, mean age 44.8 (range 23-67), 60%F were screened for GI symptoms using the PAGI-Sym Questionnaire and did not meet exclusionary criteria regarding medical/surgical diagnosis or medications. One subject had abnormally slow gastric emptying and was excluded, leaving 23 asymptomatic subjects with normal gastric empting studies. Upright scintigraphic gastric emptying anterior/posterior image sets were acquired every 15 min for the first 2 hrs and at 3- and 4-hrs, beginning immediately following ingestion of a standardized Tc99m-labeled eggbeater meal. Total stomach (TS) gastric emptying was evaluated using standard GE Xeleris software. Decay-corrected geometric mean TS curves were normalized to their maximum value. Proximal (P) emptying was evaluated using software developed locally in the GE Aladdin language. Computer generated P ROIs were applied only to anterior images as this analysis addresses residual food only in the proximal stomach. Since the decay-corrected P time-activity curve did not always decrease monotonically, P emptying was characterized separately for all subjects (Group I), excluding those studies in which early curve points rose above the initial value (Group II), and excluding additional studies in which the curve did not decrease monotonically during P gastric washout (Group III). Group I P emptying curves were normalized to their maximum value; Groups II and III curves were normalized to their initial value.

Results: For all (Group I) subjects, percent of total stomach emptied averaged 25.1±14.1 (SD), 61.7±18.6, 86.3±11.3 and 96.7±4.0 at 1, 2, 3 and 4 hours, respectively. Time to half-emptying averaged 102.7±26.1 min. In Group II, 10 (43%) of the Group I subjects were excluded due to a subsequent early increase in proximal activity beyond the time-zero value. In Group III, an additional 6 (26%) of the Group I subjects were excluded due to failure of the proximal activity to monotonically decrease during washout. Mean values of percent of labeled food remaining in the P ROI at various times depended on how the curves were normalized and whether or not studies with intermittently increasing values were included. For example, at 60 min, mean P percent activity was reduced to 57.7±5.1% (SEM), 43.4±12.0%, and 38.0±14.4% in Groups I, II and III, respectively (ANOVA, p=0.05). There were no significant differences (p=0.83) among the percentages of TS content initially in the proximal stomach (at time-zero), averaging 53.8±3.4% (SEM), 50.8±4.0% and 54.4±6.4% in Groups I, II and III, respectively.

Conclusion: 1) In the absence of marked esophageal reflux, failure of the total stomach emptying curve to decrease monotonically with time is usually attributed to only-approximate correction for attenuation. 2) The analysis of proximal gastric emptying curves is not straightforward. As demonstrated, quantitative results depend on how normalization and apparent intermittent activity increases are handled. 3) Such inconsistencies may arise, at least in part, from intragastric redistribution of food from the body to the proximal region, even in asymptomatic subjects. Research Support: None