Evaluation of Diabetic Gastrointestinal Dysmotility

Gastrointestinal symptoms are commonly reported in people with diabetes mellitus. Endocrinologist Adrian Vella, M.D., at Mayo Clinic in Minnesota, says, "Approximately 75 percent of patients referred to a diabetes clinic have at least one gastrointestinal symptom. Such symptoms, however, should not be ascribed to diabetes without appropriate evaluation."

The most common gastrointestinal symptoms related to diabetes metillus are:

• Heartburn
• Nausea
• Vomiting
• Abdominal pain
• Diarrhea
• Constipation
• Fecal incontinence

Gastrointestinal tract

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The most common gastrointestinal complications of diabetes mellitus are:

• Esophageal dysmotility
• Gastroparesis
• Decreased accommodation/rapid gastric emptying
• Bacterial overgrowth
• Diabetic diarrhea
• Colonic dysmotility
• Anorectal dysfunction

Gastrointestinal symptoms may also be due to the increased prevalence of certain gastrointestinal diseases in patients with diabetes. Diseases of the gastrointestinal tract associated with diabetes mellitus are:

• Celiac disease
• Microscopic colitis
• Fatty liver
• Hepatitis C

Etiologic Factors of Gastrointestinal Symptoms in Diabetes Mellitus

Gianrico Farrugia, M.D., of the Division of Gastroenterology and Hepatology at Mayo Clinic in Minnesota, says that the etiologic characteristics of gastrointestinal symptoms in patients with diabetes are multifactorial. Similar to damage caused by peripheral neuropathy, there is evidence that damage to the extrinsic innervation of the gastrointestinal tract occurs in diabetes.

Many patients, however, have gastrointestinal symptoms without extrinsic neuropathy. There is increasing evidence of damage to the enteric nervous system in diabetic gastroenteropathy. Neuronal nitric oxide expression in enteric neurons is markedly decreased early in the course of diabetic gastroenteropathy. Although neuronal apoptosis is increased, most of the decrease in neuronal nitric oxide is not accompanied by neuronal loss; neuronal nitric oxide expression can be restored by decreasing oxidative stress and by using insulin.

"The interstitial cells of Cajal (ICC), together with enteric nerves and smooth muscle cells, are required for normal gastrointestinal motility. The ICC pace smooth-muscle function, amplify neuronal signals, act as mechanosensors, and set the smooth muscle membrane potential. Both human studies and animal models show loss of ICC in gastroparesis and diabetes-associated constipation. Reversal of this deficit in animals normalizes gastric emptying, suggesting that the loss of ICC is central to the development of motor abnormalities," says Dr. Farrugia.

Evaluation and Diagnosis

Dr. Vella explains that in all evaluations of gastrointestinal symptoms that may be attributable to diabetes, a thorough history and physical examination should be the starting point. Nausea, vomiting, early satiety, and abdominal pain are the commonest symptoms in patients with gastroparesis.

Evaluation should include an assessment of medications that may be contributing to symptoms, a complete blood cell count, the serum thyrotropin concentration, and a metabolic panel. A test for blood amylase concentration and a pregnancy test may be relevant.

Mechanical causes need to be excluded with endoscopy of the upper gastrointestinal tract or an upper-gastrointestinal series; if results are normal, then a gastric-emptying study should be obtained. Gastroduodenal manometry may also be necessary.

If the history and the findings on the physical examination suggest general autonomic dysfunction (e.g., abnormal pupil responses, abnormal sweating, urinary retention or impotence), strong consideration should be given to autonomic nervous system evaluation, including cardiovascular responses to posture, thermoregulatory, and nerve conduction testing.

For symptomatic diarrhea, drug-related causes need to be excluded. Causes of diarrhea in diabetes mellitus include:

• Medications (e.g., metformin, acarbose, miglitol)
• Artificial sweeteners
• Rapid intestinal transit
• Bacterial overgrowth
• Celiac disease
• Pancreatic insufficiency
• Microscopic colitis
• Sphincter dysfunction
• Diarrhea not associated with diabetes

Dr. Farrugia notes that the bacterial overgrowth associated with small-bowel dysmotility, microscopic colitis, and celiac disease is more common in patients with diabetes than in other patient groups, and the initial presentation may be diarrhea. Therefore, blood tissue transglutaminase concentration, small-bowel biopsy (if tissue transglutaminase level is abnormal), small-bowel aspirate for bacterial culture (or equivalent testing), and random colonic biopsies may be required. Sphincter tone should be assessed by anorectal manometry.

"If the presenting symptom is constipation, a medication and exercise history should be obtained, as well as serum calcium and thyrotropin concentrations. Patients who are due for colon cancer screening should be evaluated with colonoscopy. Colonic transit tests and anorectal manometry with balloon expulsion help differentiate between normal transit constipation (most common), slow transit constipation and pelvic floor dysfunction," says Dr. Farrugia.