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Epidemiology of gastroparesis
Introduction – the challenge
Gastroparesis is commonly defined on the basis of the combination of symptoms and delayed gastric emptying, in the absence of mechanical obstruction. Therein lies a major challenge to attempts to provide accurate data on the incidence or prevalence of this disorder which must include (i) a definition of what symptoms are to be regarded as relevant, (ii) an accurate measurement of gastric emptying rate and (iii) appropriate testing to exclude gastric outlet or small bowel obstruction.
Symptoms indicative of gastroparesis
Traditionally, nausea and vomiting have been regarded as the “classical” symptoms of gastroparesis; more recent literature reveals a more inclusive approach with the NIH consensus group incorporating nine symptoms: nausea, retching, vomiting, stomach fullness, inability to finish a meal, excessive fullness, loss of appetite, bloating and abdominal distension in their Gastroparesis Cardinal Symptom Index (GCSI) . It can be readily appreciated that these symptoms overlap with functional gastrointestinal disorders such as functional dyspepsia and irritable bowel syndrome . The more recent adoption of abdominal pain as a symptom of gastroparesis further complicates the use of symptoms as a clinical indicator of gastroparesis. Up to 89% of individuals with gastroparesis are reported to complain of upper abdominal pain and in the NIH cohort this pain was moderate to severe in 66% and did not correlate with gastric emptying rate . Not surprisingly many consume opiates which further confuses attempts to interpret gastric emptying studies; forty-one per cent of 583 patients in one report from the Gastroparesis Clinical Research Consortium (GpCRC) Registry were taking opioids . Additional symptoms may be relevant in specific clinical contexts – hypoglycemia in diabetes due to delayed emptying of nutrients and on-off phenomena in Parkinson’s disease due to unpredictable delivery of dopaminergic medications. Taking all of these factors together renders a diagnosis of gastroparesis on the basis of symptoms alone nigh impossible. Indeed, symptoms have proven very poor predictors of gastric emptying rate and symptom patterns and severity were very similar when subjects with nausea and vomiting with and without gastric emptying delay were compared .
Tests of gastric emptying
There is no shortage of test modalities which have been proposed as valuable in the assessment of gastric emptying rate: plain radiographs, breath tests, radionuclide scintigraphy, ultrasonography, magnetic resonance imaging, pharmacological approaches and SPECT imaging . Because of cost and availability some are clearly unsuitable for large scale epidemiological studies and only one, radionuclide scintigraphy, has been validated in a large multicenter study . Its utility in the general population is also limited by the involvement of radiation exposure. Though this technique is by far the most widely used worldwide in clinical practice its comparability between centers is limited by differences in study meal, protocol and interpretation.
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