Gastroparesis overdiagnosed in functional dyspepsia
Functional dyspepsia, defined as chronic or recurrent epigastric pain or discomfort, is a common syndrome in clinical practice. It is frequently associated with delayed gastric emptying, which is known to occur in about one-third of cases. Less widely recognized is that approximately 1 in 4 patients with idiopathic or diabetes-related dyspepsia has rapid gastric emptying. Because neither problem can be distinguished from normal motility based solely on symptoms, patients have traditionally been assessed with scintigraphy — a noninvasive radionuclide test with broad clinical applications.
For years, scintigraphy lacked standardization, however, with differences in the type of meal, duration of the test and normative data, which limited its clinical utility and made interpreting studies across institutions difficult. In 2008, the Society of Nuclear Medicine and the American Neurogastroenterology and Motility Society developed and published in The American Journal of Gastroenterology consensus guidelines for a standardized protocol for gastric emptying scintigraphy. Among other things, the guidelines state that acquiring images for four hours after a meal allows for better detection of abnormal function.
But according to Adil E. Bharucha, MBBS, M.D., a gastroenterologist at Mayo Clinic's campus in Rochester, Minnesota, that recommendation is often ignored.
"Many labs obtain images for an hour or two and estimate gastric emptying based on those values, assuming the stomach will continue functioning at the same rate — a practice that often leads to misdiagnosis," he says. "Our experience is that a majority of patients referred to Mayo Clinic who have been diagnosed with gastroparesis elsewhere actually have normal gastric emptying."
Gastric emptying breath test
In April 2015, the Food and Drug Administration approved a 13C Spirulina platensis gastric emptying breath test (GEBT). Unlike scintigraphy, the non-nuclear GEBT, which measures the ratio of carbon 13 to carbon 12 in multiple breath samples over a four-hour period, can be performed in any clinical setting. The validation studies for the test, performed at Mayo Clinic and reported in 2008 in Clinical Gastroenterology and Hepatology, found that the GEBT was 93 percent sensitive in identifying accelerated gastric emptying and 89 percent sensitive in identifying gastroparesis.
One major limitation of the test is that it measures gastric emptying only, not small intestinal or colonic transit. At Mayo Clinic, all three parameters are evaluated simultaneously using a unique version of scintigraphy that provides a screening assessment of gastrointestinal motor function within 24 to 48 hours. This is important because a substantial proportion of patients with motility disorders have both upper and lower gastrointestinal (GI) symptoms.
Enteric nutrient sensitivity
Given the relationship between lower GI disturbances, such as delayed colonic transit, and upper GI symptoms, Dr. Bharucha and colleagues recently evaluated enteric nutrient sensitivity in patients with functional dyspepsia. In that study, published in Gastroenterology in 2014, close to 50 percent of patients with functional dyspepsia were sensitive to enteral nutrient infusion, suggesting that their symptoms originated in the small intestine rather than the stomach.
Increased sensitivity to enteral dextrose and lipid infusions was associated with greater plasma enteral hormone concentrations, more-severe daily symptoms and worse quality of life. Dr. Bharucha points out that these observations are consistent with the hypothesis that enteral hormones mediate increased intestinal sensitivity to nutrients in functional dyspepsia and serve as a reminder that dyspepsia symptoms can originate in the small intestine.
How this translates into clinical practice is a work in progress, but he emphasizes that many patients diagnosed with slow or rapid gastric emptying elsewhere are found to have normal function at Mayo Clinic.
"The first thing we offer is reassurance; for most patients, learning they don't have gastroparesis comes as a relief. Then we provide multidisciplinary approaches, including selective dietary modification and behavioral and pharmaceutical therapies," he says.
For more information
Abell TL, et al. Consensus recommendations for gastric emptying scintigraphy: A joint report of the American Neurogastroenterology and Motility Society and the Society of Nuclear Medicine. The American Journal of Gastroenterology. 2008;103:753.
Szarka LA, et al. A stable isotope breath test with a standard meal for abnormal gastric emptying of solids in the clinic and in research. Clinical Gastroenterology and Hepatology. 2008;6:635.
Bharucha AE, e al. Tu1808 duodenal nutrient sensitivity during enteral lipid and carbohydrate infusion in functional dyspepsia (FD): A role for enteral hormones. Gastroenterology. 2014;146:S-849.