Reviews for Primary Care - Fall 2007 - (Page 18) Chronic Constipation and Functional Bowel Disorders continued patients with chronic constipation.32 Prudent clinical judgment also should be used. If, for example, there are alarm features such as hematochezia, weight loss, or age greater than 50 years (greater than 45 years for African Americans) present without recent colorectal cancer screening, then colonoscopy would be a very reasonable diagnostic test to perform.31-33 A review of the yield of other commonly used diagnostic modalities is presented below. Colon Transit Study to Identify Patients With Chronic Constipation The colon transit study provides information similar to that obtained with scintigraphy. Colon transit studies are noninvasive, inexpensive, and relatively easy to perform and interpret. A recent review of 6 studies that evaluated whether performing a colon transit study influenced a patient’s diagnostic outcome of STC yielded mixed results.34 Three of the studies concluded a definitive “yes”; 1 a definitive “no”; and the other 2 did not provide an answer. Collectively, one may infer that a colon transit study is a potentially helpful diagnostic test for selected patients with chronic constipation. Balloon Expulsion Test to Identify Defecatory Disorders A balloon expulsion test consists of the placement of a balloon containing 50-60 cc of water into the rectum and asking the patient to expel the balloon within a certain period of time.9,11,32 The evidence supporting the use of balloon expulsion testing to identify pelvic floor dysfunction is good. The advantages of this test are that it is a simple and inexpensive office-based screening assessment that can identify patients with possible defecation disorders. Patients who cannot repeatedly expel the balloon with ease (within 30 seconds) do not necessarily have a defecation disorder, but it suggests that further testing is warranted. Minguez and colleagues—in search of a simple method to exclude the possibility of pelvic floor dyssynergia (PFD) in constipated patients in order to avoid unnecessary, invasive, and expensive physiological studies— utilized the balloon expulsion test in 24 patients with PFD and 106 patients with functional constipation.35 The balloon expulsion test was abnormal in 21 of 24 patients with PFD and 12 of 106 without PFD and predicted the presence of an abnormal defecatory problem in almost 90% of individuals. However, the positive predictive value for diagnosing PFD was only 64%. Thus, although the balloon expulsion test has some limitations, it is a simple test that appears to identify individuals who need to be referred for anal manometry testing. Anorectal Manometry to Identify Defecatory Disorders Expulsion or defecation is a coordinated effort of enhanced propulsion through creation of abdominal pressure gradients and the relaxation of the striated muscles of the pelvic floor. When individuals cannot relax those muscles or actually contract those muscles inappropriately, they have PFD. Anorectal manometry is the single best test to identify dyssynergic defecation. One of the most challenging aspects of evaluating patients for PFD is locating a center or practitioner that offers these services. Defecography, functional magnetic resonance imaging, and anorectal manometry are not widely practiced and require dedicated techniques and equipment. Moreover, identification of therapists who can provide subsequent pelvic floor retraining if clinically indicated also can be a challenge. Summary of Diagnostic Testing Evidence to support the use of blood tests, radiography, or endoscopy to exclude organic disease responsible for constipation symptoms in patients without alarm features is lacking.32 Colon transit, anorectal manometry, and balloon expulsion tests can reveal physiological abnormalities in some patients with constipation, but no single test adequately defines the pathophysiology underlying the symptoms. In place of diagnostic testing, there is another important tool that often is forgotten by the clinician: a simple 2-week prospectively kept diary of bowel function. The diary helps identify realistic bowel function and reduces reliance on patient perception/ memory of bowel functions. At least 50% of patients who report that they have infrequent defecation will not have that when prospective records are obtained.36 Figure 6 provides a summary of the evaluation and classification of idiopathic chronic constipation.24 Update on the Management of Chronic Constipation and IBS-C Recent Changes in Treatment Availability Some significant changes have occurred recently with regard to current treatments for constipation and IBS-C. In March 2007, Schering-Plough announced that polyethylene glycol (PEG) 3350, an osmotic laxative indicated for the treatment of occasional constipation, is available as an overthe-counter medication.37 On March 30, 2007, Novartis voluntarily agreed to suspend the US marketing and sales of tegaserod because a safety review of clinical trial data found that patients randomized to tegaserod had a higher chance of myocardial infarction, stroke, and unstable angina (heart/chest pain) compared with those randomized to 18 VOL. 1 NO. 1 2007 REVIEWS FOR PRIMARY CARE
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