Gastric emptying in Parkinson's disease - A mini-review.

Patients with Parkinson's disease (PD) experience a range of non-motor symptoms, including constipation and other gastrointestinal problems. These symptoms are sometimes present in the prodromal disease phase. An improved understanding of the underlying pathophysiology is needed considering that PD has been hypothesized to originate in the gut. Delayed gastric emptying time (GET) is often listed as a prevalent gastrointestinal symptom in PD, but the true prevalence is controversial. The aim of this short review was to investigate if GET in PD is dependent on the applied measuring methodology. A systemic search of Pubmed identified 15 relevant studies, including six using gold standard method gastric scintigraphy and nine using 13C-octanoate breath tests. Overall, gastric scintigraphy studies showed a non-significant GET delay (standardized mean difference (SMD) 0.42) in PD patients. After exclusion of one outlier study, GET was significantly increased (SMD 0.59). In contrast, highly significant GET delay (SMD 1.70) was seen in breath test studies. A limitation of the meta-analyses was reuse of the same control group in some studies. In summary, the marked GET delay observed in breath test studies is not confirmed by gold standard gastric scintigraphy studies. This discrepancy can perhaps be explained by breath test being an indirect GET measure, depending not only on mechanic stomach emptying but also intestinal absorption and liver metabolism. Thus, multi-modality studies under standardized conditions are needed to elucidate the prevalence and severity of gastric dysmotility in PD, along with contributions from other factors including intestinal absorption and permeability.