Gastroparesis, a syndrome in which patients experience delayed gastric emptying, is characterized by symptoms such as nausea, vomiting, bloating, abdominal pain, and early satiety. Despite the significant morbidity of the condition, research and characterization of the clinical features of gastroparesis are limited, hindered by challenges such as single centers and small study populations. The Gastroparesis Registry (GpR) was an observational study created by the Gastroparesis Clinical Research Consortium (GpCRC) to enroll a sufficiently large number of patients to elucidate the clinical features of the condition and investigate their association with various patient characteristics. Following conclusion of the GpR study, the Gastroparesis Registry 2 (GpR 2) was initiated as follow-up to expand the registry for continued investigation of the epidemiology, etiology, and clinical course of gastroparesis.

Individuals with symptoms of gastroparesis of at least 12 weeks duration and delayed gastric emptying on scintigraphy were enrolled. Individuals with symptoms of gastroparesis but with normal gastric emptying were also enrolled as a reference group. Participants must have had an upper endoscopy within 2 years prior to registration to rule out other disorders. During screening, data were collected on medical history, physical examination, 4-hour gastric emptying scintigraphy results, and symptoms of gastroparesis and psychological functioning using participant-completed questionnaires. Additionally, diagnostic tests of wireless motility capsule to assess whole gut transit, autonomic function testing, and electrogastrography were done to investigate the pathophysiology of the condition. Participants were followed via site visits every 24 weeks and information was collected on symptoms, quality of life, treatments being used, and change in medical condition. Plasma and serum specimens from each participant were collected and stored.

The primary objective of the study was to expand the registry of patients with gastroparesis for the study of epidemiology, etiology, and outcomes associated with the condition.

The secondary objective of the study was to provide a reliable source of recruitment of well-characterized patients with gastroparesis for therapeutic clinical trials and ancillary studies.

Since the GpR 2 study was a registry study designed to expand a registry of patients for the study of the epidemiology, etiology, and degree of morbidity associated with gastroparesis, no outcome measures were assigned.

Inclusion criteria:

• At least 18 years of age
• Symptoms of gastroparesis of at least 12 weeks duration (does not have to be contiguous) with varying degrees of nausea, vomiting, abdominal pain, early satiety, and post-prandial fullness
• An etiology of either diabetic, idiopathic, or post-Nissen fundoplication gastroparesis
• Completion of a 4-hour scintigraphic gastric emptying study (for classification of definite gastroparesis or gastroparesis-like with normal gastric emptying)
• No abnormality causing obstruction on upper endoscopy, done within 2 years

Exclusion criteria:

• Inability to comply with or complete the gastric emptying scintigraphy test (including allergy to eggs)
• Presence of other conditions that could explain the patient's symptoms such as:
  • Pyloric or intestinal obstruction as determined by endoscopy, upper GI series or abdominal CT scan
  • Active inflammatory bowel disease
  • Known eosinophilic gastroenteritis
  • Primary neurological conditions that could cause nausea and/or vomiting such as increased intracranial pressure, space occupying, or inflammatory/infectious lesions
  • Acute liver failure
  • Advanced liver disease (Child's B or C; a Child-Pugh-Turcotte (CPT) score of ≥ 7)
  • Acute renal failure
  • Chronic renal failure (serum creatinine > 3 mg/dL) and/or on hemodialysis or peritoneal dialysis
• Total or subtotal (near complete) gastric resection, esophagogastrostomy, gastrojejunostomy, or gastric bypass (Note: Patients with prior fundoplication were eligible for enrollment)
• Any other plausible structural or metabolic cause
• Any other condition, which in the opinion of the investigator would interfere with study requirements
• Inability to obtain informed consent

Abdominal pain is common in patients with gastroparesis (Gp), both idiopathic and diabetic. Severe/very severe upper abdominal pain occurred in 34% of Gp patients and associated with other Gp symptoms, somatization, and opiate medication use. Autonomic dysfunction was common in patients with Gp and chronic unexplained nausea and vomiting (CUNV). Parasympathetic dysfunction was associated with delayed gastric emptying and more severe upper gastrointestinal symptoms. Conversely, sympathetic hypofunction was associated with milder symptoms. Early satiety (ES) and postprandial fullness (PPF) severity were significantly associated with other Gp symptoms including nausea/vomiting subscore and bloating subscore, as well as measures of Gp severity, quality of life, gastric emptying, and water load testing. Wireless motility capsules (WMC) defined gastric emptying delays similar but not identical to scintigraphy that were more severe in diabetics and related to reduced gastric contractility. Extragastric transit delays occurred in > 40% with suspected Gp. Gastroparesis symptoms showed little association with WMC profiles, although lower symptoms related to small bowel or colon abnormalities. In 138 patients with idiopathic gastroparesis, 10% were underweight whereas 29% were obese. Over 48 weeks, 30% of patients increased their body weight ≥ 5%. Diet, activity, and symptoms were important factors associated with body weight in patients with idiopathic gastroparesis. Severe/very severe constipation and delayed colon transit occurred in a third of patients with Gp symptoms. The severity of constipation was associated with severity of Gp symptoms, presence of IBS, small bowel and colon transit delay, but not delay in gastric emptying.