Definition

Gastroparesis (GP) is a syndrome characterized by symptoms such as nausea, vomiting, epigastric discomfort, early satiety, bloating, abdominal pain, and/or flatulence. It is marked by a clinically significant delay in gastric emptying without any mechanical obstruction. Diagnosing GP requires an objective measurement of gastric emptying, traditionally done through a 4-hour scintigraphy with a standardized test meal. Alternatively, gastric emptying can be assessed using a breath test with the stable isotope 13-carbon spirulina (13C). Prevalence estimates for GP in the general population range from 13.8 to 267.7 cases per 100,000 adults, depending on the definition used. Among diabetic patients, the 10-year cumulative incidence is estimated at 5.2% in type 1 diabetes and 1% in type 2 diabetes. Most cases of GP (57.4%) have a diabetic etiology, particularly linked to peripheral neuropathy. Additional risk factors for GP include connective tissue disorders, certain surgical procedures (notably those involving accidental vagus nerve injury, such as in hiatal hernia repair, fundoplication, or lung transplantation), ischemia, ulcer disease, and various inflammatory or neurological disorders. GP can severely impact quality of life and even increase mortality risk. Treatment should be individualized based on the severity and predominant symptoms. For example, patients with mild idiopathic GP primarily presenting with occasional nausea may only need dietary adjustments, whereas patients with chronic diabetic GP, experiencing daily nausea, vomiting, and severe abdominal pain, may require a comprehensive, multimodal medical approach. Various prokinetic agents are available to manage gastroparesis symptoms.

Effects on Nutritional Status

Chronic symptoms like nausea, vomiting, epigastric discomfort, and early satiety can significantly reduce energy and protein intake, placing patients at high risk of malnutrition. The resulting negative energy balance often leads to pathological weight loss and increased fluid needs. Nutritional interventions focus on modifying food composition, consistency, and portion size to accommodate delayed gastric emptying. When solid food intake does not meet energy and protein requirements, further interventions—such as liquid meals, oral nutritional supplements, enteral nutrition, and ultimately parenteral nutrition—should be considered in a stepwise manner. Given the complexity of managing nutritional status in GP and the potential for food aversions, early involvement of a dietitian is essential to ensure a balanced nutrient intake.

It is worth noting that many patients with gastroparesis (GP) voluntarily restrict their food intake to minimize symptoms, which can lead to malnutrition, vitamin and nutrient deficiencies (e.g., vitamins D, E, K, folic acid, calcium, iron, and protein), and even the development of restrictive eating behaviors. Therefore, nutritional therapy and supplementation should be individualized, considering the underlying cause of GP, such as postoperative phases or chronic illness.

Aims of Nutritional Therapy

• Enhance gastric emptying and nutrient utilization to alleviate postprandial discomfort 
• Increase energy and protein intake 
• Maintain or improve nutritional status and bodily function 
• Prevent malnutrition and nutrient deficiencies 

To detect malnutrition early, patients should undergo a Nutritional Risk Screening at least twice a year.

Oral Nutrition

Whenever possible, energy and protein needs should be met through oral nutrition.

In GP patients, large food volumes delay gastric emptying, with both energy density and food mass (especially fiber) contributing to this effect. Early satiety is common, so the primary nutritional strategy involves eating smaller, more frequent meals throughout the day. Patients may need five to six small meals or snacks daily to meet their nutritional needs. If less than 75% of requirements are met with oral intake, including supplementation, snacks, or sip feeds, supplementary enteral nutrition should be introduced within five days. Complementary parenteral nutrition is indicated if less than 75% of needs are met through oral and/or enteral nutrition.

Practical Advice (If Indicated)

Small, Frequent Meals: Eating 4-6 small meals daily reduces meal volume, which can help manage early satiety and minimize the feeling of fullness. 

• Limit Dietary Fiber: Fiber-rich foods digest slowly and can exacerbate symptoms in GP patients by increasing early satiety. Additionally, bacterial overgrowth in the small intestine (SIBO) and the use of proton pump inhibitors may worsen symptoms in patients with GP. 
• Avoid Irritating Foods: Spicy, fatty, fibrous, and acidic foods may aggravate symptoms. Instead, consume mild, salty, sweet, starchy, and bland foods. 
• Finely Chopped or Pureed Food: Cutting food into small pieces or pureeing it helps facilitate faster gastric emptying. Patients should also chew food thoroughly. 
• Use Liquid or High-Calorie Nutritional Supplements: If solid food is poorly tolerated, liquid meals or high-calorie oral nutritional supplements can be helpful, as they are often easier to digest. High-energy protein drinks and multivitamin/mineral supplements can also support nutritional intake. 
• Limit Alcohol and Nicotine: Both alcohol and nicotine slow gastric emptying, so consumption should be minimized. 
• Stay Hydrated: Adequate fluid intake is essential to prevent dehydration. 
• Stay Upright After Meals: Sitting, standing, or walking after meals promotes faster gastric emptying compared to lying down. 
• Involve a Dietitian Early: Early Involvement of a dietitian is recommended to ensure a balanced nutrient intake. 

Practical Advice

• GP-Suitable Foods or Whey-Based Products are generally preferable for patients with GP. For your information:  Milk protein is composed of 80% casein and 20% whey. The casein micelles are negatively charged and repel each other, keeping the protein dissolved in milk. Due to their micelle structure and high proline content, caseins are relatively heat-stable and do not easily denature. Upon contact with gastric acid, caseins coagulate to form a solid mass, whereas whey proteins remain liquid. Whey proteins are more heat-sensitive, denaturing at around 74°C, but they don’t coagulate due to their ability to form complexes with caseins. 
• A low-FODMAP diet may be beneficial for GP patients with dysmotility disorders. FODMAPs (fermentable oligo-, di-, mono-saccharides, and polyols) are easily fermented by intestinal microbiota and have a strong osmotic effect, which can worsen GP symptoms. 
• Constipation can exacerbate GP symptoms, so maintaining regular bowel movements is important. 

Special Considerations

• Patients with GP due to previous gastric surgery are at an even higher risk of nutrient deficiencies due to anatomical changes and altered nutrient absorption. For instance, patients with a subtotal gastrectomy may be at risk for deficiencies in iron, vitamin B12, vitamin D, and vitamin E. Gastric bypass surgery, which intentionally induces malabsorption, can lead to a broader range of nutrient deficiencies (refer to chapter on bariatric surgery for further details).

Monitoring

• Glycemic Control in Diabetic GP: For patients with diabetic GP, optimal glycemic control is recommended to reduce the risk of exacerbations. 
• Avoid Medications That Delay Gastric Emptying: Medications known to slow gastric emptying should be avoided, including aluminum-containing antacids, anticholinergics, atropine, beta agonists, calcitonin, calcium antagonists, dexfenfluramine, diphenhydramine, ethanol, glucagon, interleukin-1, L-dopa, lithium, octreotide, ondansetron, narcotics, nicotine, potassium salts, progesterone, sucralfate, tricyclic antidepressants, and SSRIs. 

Diagnostics

GP is often over- or misdiagnosed. Conducting a validated gastric emptying study and interpreting results within the patient’s clinical context is essential for accurate diagnosis.

• Scintigraphy: The gold standard for GP diagnosis, involving the measurement of gastric emptying of a solid meal over at least 3 hours. 
• Breath Test with 13C-spirulina: A reliable alternative for assessing gastric emptying. 
• Wireless Motility Capsule: An alternative test to scintigraphy for GP. 
• Radiopaque Marker Test: Not recommended for diagnosing GP. 

Treatment

Dietary adjustments should be the first line of treatment for GP. If symptoms persist, pharmacological options to promote gastric emptying and alleviate nausea may be considered.

Drug therapy

• General Considerations: For idiopathic and diabetic GP, drug therapy to enhance gastric emptying and relieve symptoms should be considered, with a careful assessment of benefits and risks. 
• Prokinetics and Antiemetics: For patients with refractory symptoms, the following may be used: Metoclopramide and Domperidone: Both offer prokinetic and antiemetic effects. Ondansetron: Used primarily for antiemetic support. Erythromycin (off-label): Acts as a prokinetic by increasing antral motility and reducing gastric fundus relaxation; however, it may exacerbate symptoms like bloating and nausea. Prucalopride: Effective as a prokinetic in both the stomach and colon. Note: Antiemetics can help with symptom control but do not improve gastric emptying. Prokinetic drugs may not effectively relieve pain, a common symptom in up to 90% of GP patients. No long-term studies are available.
• Mirtazapine: Shown effective in some case reports at 15 mg for GP (off-label). It acts as a noradrenergic and specific serotonergic antidepressant, antagonizing presynaptic α2-, postsynaptic 5-HT2- and 5-HT3- receptors, and histamine H1-receptors. 
• Central Neuromodulators: Recommended only on a trial basis. 
• Other Agents: Insufficient data to recommend ghrelin agonists and haloperidol for GP management. 

Further Treatment Options

• Gastric Electrical Stimulation: Can be considered for controlling GP symptoms in select patients. 
• Pyloromyotomy: Recommended as a trial for patients who do not respond adequately to drug therapy, to help alleviate symptoms. 
• Acupuncture: Either alone or in combination with prokinetic drugs, acupuncture may be beneficial for symptom control. 
• Herbal Therapies: Rikkunshito and STW5 (Iberogast) may be used on a probationary basis, though they are generally recommended for functional dyspepsia rather than specific GP symptom relief. 
• EndoFLIP Examination: The Endoluminal Functional Lumen Imaging Probe (EndoFLIP) is valuable for assessing pyloric function and predicting potential outcomes after peroral pyloromyotomy. 
• Intrapyloric Botulinum Toxin Injection: Suggested only on a trial basis, as evidence for its effectiveness remains limited. 
• Holistic Approach: Treatment should not focus solely on accelerating gastric emptying. Given that many patients may also have gut-brain axis dysfunction, a comprehensive approach is crucial. Behavioral therapies, such as cognitive behavioral therapy (CBT) and hypnotherapy, should be considered as complementary methods to address the broader symptom complex within the context of this chronic condition.