Fundic accommodation assessed by SPECT scanning: comparison with the gastric barostat

Background: Recently, single photon emission computed tomography (SPECT) scanning was described as a non-invasive technique to assess fundic accommodation. However, in contrast with the barostat, no intragastric distending force is applied during SPECT scanning. We hypothesised that in the absence of a barostat balloon, SPECT scanning largely detects the volume effect of the ingested meal and is a rather insensitive tool to detect fundic relaxation.

Methods: After an overnight fast, healthy volunteers underwent a barostat study and SPECT scanning on two separate days to assess: (1) meal induced fundic accommodation (Nutridrink, 200 ml, 300 kcal); and (2) gastric relaxation to 1 mg intravenous glucagon.

Results: Fasting fundic volumes (145 (8) v 280 (32) ml; p=0.001) and average postprandial volume (329 (10) v 571 (53) ml; p=0.001) were significantly lower measured with SPECT compared with the barostat study. Meal induced fundic relaxation (183 (10) v 289 (46) ml; p=0.050) and the postprandial/fasting volume ratio (2.32 (0.10) v 2.27 (0.29); p=0.892) did not differ significantly between SPECT scanning and the barostat. However, no correlation could be determined between accommodation volumes measured by both techniques. In contrast with meal induced relaxation, the glucagon induced increase in fundic volume (19 (5) v 406 (56) ml; p=0.007) and post/pre glucagon ratio (1.16 (0.03) v 3.02 (0.54); p=0.046) were significantly lower when measured by SPECT scanning compared with the barostat.

Conclusion: SPECT scanning detects changes in postprandial volume but is less suitable than the gastric barostat in detecting changes in gastric tone. Our study therefore questions its role as a tool to detect impaired accommodation and warrants further validation of this technique.