The Utility of Adding a Liquid-Nutrient Meal to Aid Interpretation of Small-Bowel Transit Scintigraphy

Small-bowel transit scintigraphy (SBTS) evaluates the accumulation of a radiolabeled meal in the terminal ileal reservoir (TIR) 6 h after ingestion. The location of the TIR may be difficult to determine because anatomic information is limited; for equivocal studies, the patient is asked to return the next day to help determine the TIR location by potential transit into the colon. The purpose of this study was to evaluate whether administration of an additional liquid-nutrient meal (LNM) at 6 h can promote movement of the radiolabeled meal to aid in the interpretation of SBTS and eliminate the need for the patient to return. Methods: This retrospective study reviewed 117 SBTS studies from February 2017 to September 2019. Patients were fed a standardized mixed radiolabeled solid-liquid meal for gastric emptying with SBTS according to Society of Nuclear Medicine and Molecular Imaging practice guidelines. An additional LNM was given at 6 h, and post-LNM images were obtained at least 20 min after the LNM. Two board-certified nuclear medicine physicians independently evaluated all images as equivocal or diagnostic at 6 h. Results: Of the 117 patients (71.8% female; median age, 42.0 y) undergoing SBTS, 37 were equivocal cases at 6 h before the LNM (31.6%; 95% CI, 23.3%-40.9%), compared with 12 equivocal cases after the LNM (10.3%; 95% CI, 5.4%-17.2%). Of the equivocal cases, 25 (69.4%; 95% CI, 51.9%-83.7%) had a definitive result after the LNM, whereas 11 (30.6%; 95% CI, 16.4%-48.1%) remained equivocal and 1 showed rapid transit. Among the 23 patients with gastroparesis, only 13 (57%) responded to the LNM, and none of the 3 patients with irritable bowel syndrome responded. Conclusion: The number of equivocal SBTS cases decreased after administration of an LNM at 6 h, converting to a definitive result. This suggests that with use of an LNM, most patients can complete SBTS in 1 d without the need for repeat imaging at 24 h. Administering an LNM appears to be less effective for patients with gastric disorders. However, the clinical significance remains to be explored, and it is unclear whether such patients have both a gastric and a small-bowel disorder, hence reducing any motility-promoting effect of the LNM.