Table of Contents
Definition of Intestinal Motility Disorders
Patients with intestinal motility disorders might develop abnormal intestinal peristaltic movement, intestinal paralysis, spasms and contractions. Depending on whether the cause is intrinsic to the intestinal neuronal layers or a consequence of a systemic condition, intestinal motility disorders can be primary or secondary.
Patients with intestinal motility disorders complain of abdominal pain, distension, constipation, diarrhea and/or vomiting. They might have a fever because of an infectious etiology or because of dehydration.
Epidemiology of Intestinal Motility Disorders
Intestinal motility disorders are sometimes difficult to diagnose, but it is currently estimated that 30 million Americans complain of some sort of an intestinal motility disorder. Additionally, intestinal motility disorders constitute up to 45% of all GI conditions, making them a serious burden to the healthcare system. Fortunately, motility and morbidity associated with intestinal motility disorders is low.
Functional intestinal motility disorders such as irritable bowel syndrome are more common in the younger population, ranging between 20 and 40 years old. Other forms of intestinal motility disorders are not age specific. Intestinal motility disorders are three times more common in females.
Etiology of Intestinal Motility Disorders
Several etiologies have been identified for intestinal motility disorders, but the majority of the cases remain cryptogenic. Irritable bowel syndrome can be one of the common causes of functional intestinal motility disorders. Patients can have symptoms related to both the small intestine and the colon.
Patients with prolonged history of fecal incontinence and constipation are at risk of developing intestinal motility disorders. This could be related to diet choices, prolonged stretching of the colon or dependence on laxatives.
Additionally, several causes have been identified for constipation, which include poor diet choices of low fiber foods, pregnancy, psychological issues, hypothyroidism, and anal fissures and hemorrhoids. If the cause of constipation can be eliminated, patients might stop their dependency on laxatives and their intestinal motility disorder related symptoms are expected to improve.
Certain genetic polymorphisms in mitochondrial DNA put the carrier at risk of developing constipation and other forms of intestinal motility disorders. Infections can cause abdominal distention, vomiting and diarrhea. Lactose intolerance or glutenopathy can also cause abdominal pain, malabsorption and weight loss.
Clinical Presentation of Intestinal Motility Disorders
Patients with intestinal motility disorders complain of constipation or diarrhea, vomiting, abdominal pain, distention, abdominal colicky pain, frequent defecation, fecal incontinence, fever and signs of dehydration. Additionally, physical examination can reveal signs of other secondary causes of abnormal intestinal motility. These could be signs and symptoms of hyperthyroidism—including tremors, fever, high blood pressure and a goiter—and hypothyroidism—including cold intolerance, weight gain and hoarseness of voice. Patients with hyperthyroidism are more likely to complain of diarrhea, while those with hypothyroidism might have constipation.
History taking and physical examination should differentiate between organic causes of abnormal intestinal motility and functional causes such as irritable bowel syndrome.
Diagnostic Work-up for Intestinal Motility Disorders
Patients with obstructive bowel disease due to cancer or benign strictures might have anemia on their complete blood count. Electrolyte imbalance should be excluded as disorders of potassium and sodium homeostasis can be associated with intestinal motility disorders, namely constipation. Patients with steatorrhea might have pancreatic exocrine dysfunction and should have their stool examined for fat content, in addition to excluding bacterial overgrowth. Tumor markers should be checked, such as CA-125 and carcinoembryonic antigen, when cancer is a possibility.
Abdominal X-rays are indicated to exclude bowel obstruction. Air-fluid levels can be seen on organic causes of intestinal obstruction, but abdominal X-rays are usually normal in irritable bowel syndrome.
Barium meal is also needed to evaluate a patient with an intestinal motility disorder. Delays in transit time are common in patients with organic causes of constipation, while normal transit times are common in irritable bowel syndrome.
Endoscopy is also beneficial in patients with constipation or diarrhea, especially when they have occult blood on stool examination. Colonoscopy helps confirm organic causes of constipation such as strictures, tumors and intestinal paralysis. Biopsy can be taken from suspected lesions to exclude malignancy.
Medications Used in Intestinal Motility Disorders
Cholinergic agonists are indicated in cases of constipation without an apparent obstructive lesion. Neostigmine inhibits enzymatic destruction of acetylcholine, while bethanechol stimulates muscarinic receptors directly.
Patients with severe constipation or with constipation-dominant irritable bowel syndrome might benefit from promotility or prokinetic drugs. Tegaseroid can be used in the treatment of constipation-dominant irritable bowel syndrome with good results. Tegaseroid is a serotonin receptor agonist that works on serotonin receptor 4 but not the 5-HT3 receptors.
Metoclopramide can help patients with vomiting as it improves the synchrony between the stomach and duodenum.
Patients who are receiving opioids, for instance, for pain relief in terminal cancer are at risk of developing constipation as a consequence. Methylnaltrexone, a peripheral-acting opioid antagonist, can alleviate opioid-related constipation in this group of patients.
Patients with mainly diarrheal symptoms should be evaluated for a possible infectious etiology before attempting to start antidiarrheal therapy. Loperamide inhibits intestinal motility and is used in patients with intractable diarrhea. Patients might also benefit from a diphenoxylate and atropine combination, which acts through a narcotic analgesic and anticholinergic mechanism.
Finally, it is always important to remember that one of the most common causes of acute diarrhea are infections. Ova and cyst examination of the stool, stool white blood cells and leukocytosis should be excluded as they are all signs of possible infection. When an organism is identified, antibiotics should be prescribed specifically for the causative organism.
In few cases, the antibiotic erythromycin might be used as a prokinetic agent rather than for its antimicrobial effects. Erythromycin improves stomach motility in patients with gastroparesis, i.e., diabetics. Erythromycin works as a prokinetic agent because it can mimic the action of motilin, which is responsible for peristalsis movements in the intestine and stomach. IV and oral administration of erythromycin improves stomach emptying times for liquids and solids in patients with gastroparesis.