Intestinal Motility Disorders Workup

A complete workup should be performed to exclude an organic cause for the patient’s symptoms (eg, myxedema, dynamic bowel obstruction, or malignancy, which are eminently treatable conditions). Only after the complete workup has been carried out can the patient be deemed to have a functional problem.

Workup may include laboratory studies, diagnostic imaging, manometry, electromyography (EMG), endoscopy, and diagnostic laparoscopy or laparotomy.^[11]

Routine laboratory examinations are not very useful for diagnosing primitive intestinal motility disorders, except pseudo-obstructive attacks. However, laboratory studies may be helpful for diagnosing motility disorders of the gut due to intestinal cancers or irritable bowel disease.

The complete blood count (CBC) is usually altered in patients with intestinal cancers (in whom it may show anemia) and in patients with irritable bowel disease (in whom leukocytosis is the more frequent result). In such patients, the protein electrophoresis pattern may show alterations of both albumin and globulins (especially alpha-1 and gamma globulins).

Electrolyte imbalance is common in patients with intestinal pseudo-obstruction. Serum levels of triiodothyronine, thyroxine, and glucose are also altered in these patients. Vitamin B-12 levels are reduced in persons with malabsorption. Transaminase levels can be altered in patients with liver metastases. A stool sample should be sent for analysis if the diagnosis of steatorrhea from small bowel bacterial overgrowth is suggested.

Tumor markers may be studied in patients who may have cancer of the digestive system. The most useful tumor markers for these patients are carbohydrate antigen 19-9, cancer antigen 125, and carcinoembryonic antigen (CEA). CEA is nonspecific but is useful in follow-up evaluations. Alpha-fetoprotein evaluation may help detect liver involvement by metastases from intestinal cancers.

Urinalysis is not useful in establishing a diagnosis of an intestinal motility disorder.

Plain radiographic films of the abdomen may show bowel blockage (without any actual mechanical bowel obstruction) in patients with intestinal pseudo-obstruction, but findings are usually negative in patients with irritable bowel syndrome (IBS) or constipation (see the image below).

A barium meal is a helpful study in the diagnosis of intestinal motility disorders, but it should never be administered to patients with symptoms of pseudo-obstruction, because it may cause irreversible blockage of intestinal transit. It may show a delay in transit time in persons with constipation, or the results may be normal in patients with IBS.

Computed tomography (CT) and nuclear magnetic resonance examinations are expensive and should be reserved for patients with possible intestinal malignancy.

Although defecography offers some information about the kinetics of rectal emptying, scintigraphic study of the small bowel or colonic transit time is currently preferred. Radionuclide gastric emptying tests are also performed when needed. Scintigraphic study of intestinal transit time, accomplished by oral administration of radiolabeled foods, allows study of gastric emptying and intestinal progression of the meal. It is not helpful in the diagnosis of patients with possible intestinal cancer.^[12]

Rectal manometry, a procedure for measuring the intestinal pressure exerted by the muscles of the pelvic floor, may provide some important information in patients with intestinal motility disorders, especially in those with fecal incontinence. Esophageal or gastroduodenal manometry or cystometrography may be performed as indicated.

EMG of the pelvic floor yields information about nervous conduction and muscle function, though it is not very accurate. Such information makes it possible to distinguish between functional and organic disorders of defecation.

Endoscopy usually provides information about morphologic and functional patterns of the digestive tract. Perform endoscopic studies of the upper and lower digestive tracts in any patient with an intestinal motility disorder because, in most of these patients, dysmotility has been described in the whole digestive tract.

A rectal mucosal or full-thickness biopsy may be useful in helping to diagnose amyloidosis or pathologic abnormalities of the muscularis propria or the nerve plexus (myopathies and neuropathies). Echoendoscopy may provide additional information about the muscular layer of the gastrointestinal (GI) tract.

Diagnostic laparoscopy or laparotomy, with full-thickness biopsy or resection, and immunohistochemistry can be performed to assess for c-kit –positive cells. A full-thickness biopsy sample of the small intestine can be obtained via laparoscopy, with or without a feeding jejunostomy tube. Full-thickness biopsy specimens should be examined for muscle disease, inflammatory infiltrates of the myenteric plexus, neuronal intranuclear and intracytoplasmic inclusions, neuronal destruction, and absent or deficient c-kit immunoreactivity.

If laparotomy is performed, specimens should be taken from 2 sites, with tissue obtained from dilated and nondilated segments of intestine and processed for conventional light microscopy and immunohistochemistry.

Because of their functional origin, no specific histologic pattern has been associated with primary intestinal motility disorders. Some sort of molecular damage in muscle fibers of the digestive tracct is thought to occur, or intrinsic innervation (enteric nervous system) may cause motor incoordination as a result of alterations of migrating myoelectric complexes.

Testing of c-kit immunoreactivity is used to assess the volume of the interstitial cells of Cajal. Literature suggests that a decrease in the volume of these cells is associated with slow transit of the bowel.^{[13, 14, 15, 16]}