What is Gastroparesis
Gastroparesis is a chronic gastrointestinal syndrome defined by symptomatic delayed gastric emptying of solid food, with or without delayed liquid emptying, occurring in the absence of mechanical gastric-outlet obstruction. 1
Core Definition and Pathophysiology
Gastroparesis results from failure of antral contractions and/or pyloric relaxation that impedes gastric emptying. 1 The underlying mechanisms involve:
- Neuromuscular dysfunction affecting the gastric motor function, including injury to interstitial cells of Cajal and components of the enteric nervous system 2
- Pyloric dysfunction characterized by prolonged intermittent contractions and marked increases in baseline tone, particularly in diabetic patients 1
- Impaired gastric accommodation and antroduodenal dyscoordination contributing to symptom generation 1
- Innate immune dysregulation causing injury through paracrine and oxidative stress mediators 2
Clinical Presentation
The cardinal symptoms include:
- Nausea and vomiting (typically the predominant and most persistent symptoms) 1, 3
- Early satiety (inability to finish a normal-sized meal) 1, 3
- Postprandial fullness (uncomfortable fullness persisting after eating) 1, 3
- Bloating (subjective sensation of abdominal distension) 1, 3
- Upper abdominal pain (epigastric discomfort or pain) 1, 3
- Weight loss and malnutrition in severe cases 3
Important caveat: These symptoms overlap significantly with functional dyspepsia, making accurate diagnosis challenging. 1 Additionally, symptoms correlate poorly with the degree of gastric emptying delay. 3
Etiology
The most common causes include:
- Diabetic gastroparesis accounts for approximately 25% of cases 1
- Idiopathic gastroparesis represents nearly 50% of cases, many likely representing postinfectious processes 4
- Post-surgical causes typically due to partial or complete vagotomy (intended or unintended during esophagectomy, Billroth II gastrectomy, fundoplication, or hernia repair) 1
- Medication-induced particularly from opioids and GLP-1 agonists 1
- Other causes include vascular disorders, connective tissue disorders (especially scleroderma), and post-transplantation 1
Diagnostic Approach
Gastric emptying scintigraphy performed for 4 hours after ingestion of a radiolabeled solid meal is the gold standard diagnostic test. 5 Key diagnostic requirements:
- Upper endoscopy must be performed first to exclude mechanical gastric obstruction 5
- 4-hour testing is superior to shorter durations, as 30% of patients with normal 2-hour scans show delayed emptying at 4 hours 5
- **Normal gastric retention at 4 hours is <10%**; gastroparesis is confirmed when retention is >10% 5
- Breath testing using 13C-octanoate is a validated non-radioactive alternative when scintigraphy is unavailable 5, 2
Critical testing considerations:
- Medications influencing gastric emptying should be withdrawn 48-72 hours prior 5
- Blood glucose should be controlled during testing, as hyperglycemia itself slows gastric emptying 5
- The radioisotope must be cooked into the solid portion of a standardized low-fat egg white meal 5
Medically Refractory Gastroparesis
Medically refractory gastroparesis is defined as persistent symptoms in the context of objectively confirmed gastric emptying delay, despite dietary adjustment and metoclopramide (minimum 10 mg three times daily before meals and at bedtime for at least 4 weeks). 1
Contributing Factors Beyond Delayed Emptying
Multiple factors amplify symptom intensity independent of gastric emptying delay:
- Exaggerated visceral perception and altered central processing 3
- Learned behaviors including food aversion and disordered eating 1
- Psychological distress contributing to clinical presentation 1
- Vagal nerve injury affecting neural signal transduction 1
Prevalence and Impact
Approximately 5 million U.S. adults suffer with gastroparesis-like symptoms, with an estimated prevalence of 37.8 per 100,000 for women and 9.6 per 100,000 for men. 1 The condition causes significant morbidity and healthcare utilization. 2