The term diabetic gastropathy refers to a number of neuromuscular dysfunctions of the stomach in patients with diabetes mellitus, including contractile and electrical abnormalities. These abnormalities may consist of gastric dysrhythmias, gastroparesis, antral hypomotility and dilation, antroduodenal coordination, and gastric tone dysfunction.
Pathophysiology and Mechanism of Diabetic Gastropathy
The mechanism of diabetic gastropathies is unknown. However, like other long-term complications associated with diabetes mellitus (nephropathy, retinopathy, and peripheral neuropathy), there are several proposed mechanisms that may be responsible, such as autonomic neuropathies, postprandial release of hormones, and glucose toxicity.
Vagal nerve impairment has been detected in patients with diabetes, and most likely plays a role in the development of diabetic gastropathy. Sympathetic vagal innervations inhibit vagal excitation. Vagal inhibition results in relaxation in the fundus, inhibition followed by contraction of the body, and relaxation of the pyloric sphincter and of the duodenum. Damage to inhibitory nerves may be the cause of increased gastric emptying of liquids, as well as the occasional pylorospasm. Loss of vagal tone and increased sympathetic nervous system activity have also been attributed to gastric dysrhythmias in some diabetic patients.
Postprandial hormone release of glucagon and pancreatic polypeptides, as well as the release of neurotransmitters, may be altered in diabetic patients. These responses can become complex issues, due to the variety of gastric responses stimulated by different foods.
Glucose toxicity may be a cause of end-organ neuromuscular dysfunctions. Hyperglycemia affects both intracellular metabolic pathways and membrane function in neural cells. After studying the effects of hyperglycemia in normal and diabetes patients, it was found that antral contractions in the postprandial state were significantly decreased during induced hyperglycemia.
The most severe neuromuscular abnormality associated with diabetic gastropathy is gastroparesis. Gastroparesis is often diagnosed when delayed emptying of food from the stomach has been documented. Gastroparesis is believed to result from gastric hypomotility or antroduodenal incoordination; however, autonomic nervous system dysfunction is not an absolute predictor of gastroparesis.
Epidemiology
Upper gastrointestinal symptoms such as nausea, vomiting, bloating, and abdominal discomfort are common occurrences in both type 1 and type 2 diabetes mellitus patients. It is estimated that these symptoms occur in approximately 50% of patients with type 1 diabetes and in 30% of patients with type 2 diabetes. One survey of diabetic patients revealed that 76% experienced chronic or recurrent gastrointestinal symptoms. Early satiety, fullness, and bloating are also common symptoms. As many as 50% of patients with type 1 diabetes have delayed gastric emptying.
Clinical Presentation and Diagnosis
Signs and Symptoms
Nausea and vomiting are among the most severe symptoms in patients who are diagnosed with diabetic gastropathy. Other symptoms include bloating, postprandial fullness and abdominal discomfort. Symptoms are often increased after the ingestion of solid foods. Slight dietary changes can often provide relief to patients who have meal-related symptoms. Some patients with delayed gastric emptying may be asymptomatic. The only clue that gastric neuromuscular dysfunction may be present is poor glucose control. Patients may experience episodes of hypoglycemia as a result of delayed gastric emptying. It should be noted, however, that all diabetes patients who experience upper gastrointestinal symptoms may not necessarily have gastroparesis. Therefore, other causes not related to diabetes (e.g., adverse drug reactions, pregnancy, central nervous system disorders) should be ruled out.
Diagnosis
Evaluations of diabetes patients presenting with any of the above symptoms should include a complete physical examination and medical history. Insulin and medication doses should be adjusted as needed to obtain optimal blood glucose control. Because certain medications can delay gastric emptying (TABLE 1), a medication history should be performed in order to rule out adverse drug reactions. Laboratory tests and evaluations of other organs that may cause gastrointestinal symptoms should also be performed before diagnosing a patient with gastroparesis. If these tests are found to be normal and blood glucose levels remain uncontrolled, then tests used to evaluate neuromuscular dysfunction should be considered (TABLE 2). Various tests are used to evaluate gastric emptying rate (TABLE 3), and there are advantages and disadvantages to each.
| Table 1: Medications That Can Delay Gastric Emptying | |
| Anticholinergic Agents | Nicotine |
| Antidepressants | Octreotide |
| Beta-adrenergic agonists | Opiates |
| Calcium-channel blockers | Tranquilizers |
| Ganglion blocking agents | Vincristine |
| Levodopa | |
The most common technique is gastric scintigraphy. This noninvasive procedure involves the consumption of a radioisotope-labeled meal (usually scrambled eggs). The test is performed in the morning after an evening fast. Any pharmacotherapeutic agents that can accelerate or delay gastric emptying must be discontinued 48-72 hours before the procedure. Because hyperglycemia can cause a delay in gastric emptying, patients using insulin are advised to take only one half of their morning dose. Counts of the radioisotope are taken at intervals to evaluate the rate of gastric emptying. Both solid phase and liquid phase gastric emptying studies should be performed because some diabetic patients have an abnormally rapid rate of liquid phase emptying. Gastric emptying is reported as a percentage of the meal emptied, or the time to empty 50% of the meal. The normal range of solid phase gastric emptying is variable, and results can sometimes be affected by age, obesity, or even menstrual cycles.
| Table 2: Stepwise Diagnosis of Diabetic Gastropathy | |
| Step 1 | Detailed history and physical examination |
| Step 2 | Exclude mechanical obstruction of stomach or small bowel with upper endoscopy, barium radiogram, or CT scan |
| Step 3 | Exclude metabolic factors: poor glucose control, uremia Exclude adverse effects of drugs, central nervous system disorders, pregnancy |
| Step 4 | Perform scintigraphic studies of solid-phase and liquid-phase gastric emptying |
Electrogastrography is a noninvasive test that measures fasting and postprandial gastric myoelectrical activity by placing electrodes on the skin in the epigastrium. Care must be taken to keep the patient still, since some artifacts in the electrogastrography signal are created by movement.
| Table 3: Methods for Evaluating Gastric Myoelectrical and Contractile Events | |||
| Test | Measures | Advantages | Disadvantages |
| Gastric scintigraphy | Rate of stomach emptying |
Noninvasive; solid and liquid-phase studies; assesses global stomach neuromuscular activity |
Wide normal range; radiation exposure; takes 2-4 hours |
| Electrogastrography | Gastric myoelectrical |
Noninvasive; easily repeated |
Movement artifact; activity difficult to interpret |
| Ultrasonography | Rate of emptying; antral diameter |
Noninvasive | Requires expertise in imaging and interpretation; more accurate for liquid than solid emptying |
| Magnetic resonance imaging |
Rate of emptying | Noninvasive | Time-consuming; expensive |
| Breath tests C | Indirect measure of emptying |
Noninvasive | Requires normal intestinal absorption, liver metabolism, lung function |
| Antroduodenal manometry |
Assesses lumen-occluding contractions |
Distinguishes fasting and postprandial contraction patterns |
Invasive; radiation exposure; time-consuming, >4 hours; stressful for patient; recordings difficult to interpret |
Breath tests are new techniques used to measure gastric emptying using C-labeled foods that estimate the rate of emptying of food from the C values in the expired breath. Ultrasonography is a noninvasive technique that measures the gastric emptying of liquids. Due to the complexity of the interpretation of the results, expertise is generally required for this test. Magnetic resonance imaging can also measure gastric emptying; however, this technique is often expensive and time-consuming. Antroduodenal tests are invasive and can be stressful to patients, and are often difficult to interpret.