Reviews for Primary Care - Fall 2007 - (Page 14) Chronic Constipation and Functional Bowel Disorders continued • Recurrent abdominal pain or discomfort at least 3 days/month in the last 3 months associated with 2 or more of the following: The Pathophysiology of Constipation Whereas the symptoms of chronic constipation may be very similar among different patients, there are several patterns that have been delineated that can help to differentiate subtypes of this condition. Most patients fulfilling the criteria for functional constipation have normal colonic transit.11 Others have colonic inertia, or slow-transit constipation (STC), and still others may have dyssynergic defecation. Although the Rome III criteria for functional constipation appear to exclude IBS, it is common to encounter symptoms consistent with both disorders among patients at different points in time. Additionally, overlap among the different etiologies of functional constipation can occur. Validation of this integrated model was the focus of a clinical study conducted by Mertz and colleagues.12 This study suggested 3 distinct pathophysiologies for patients with constipation symptoms: STC, IBS, and dyssynergic defecation. The authors concluded that the visceral hypersensitivity Improvement with defecation Onset associated with a change in the frequency of stool Onset associated with a change in the form of stool *Criteria fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis. Figure 2. Rome III diagnostic criteria* for IBS. Adapted from Longstreth GF et al.6 There are also supportive IBS symptoms defined by Rome III that are not part of the core diagnostic criteria. They include6: • Abnormal stool frequency ° 3 or fewer bowel movements per week ° More than 3 bowel movements per day • Abnormal stool form ° Lumpy/hard stool ° Loose/watery stool • Defecation straining • Urgency or also feeling of incomplete bowel movement, passing mucus, and bloating Differentiating IBS Subtypes The primary modifications contained in the Rome III criteria for IBS include a shorter duration requirement for symptom onset (6 months) and a focus on patient-reported predominant stool form,6 aided by use of the Bristol Stool Form Scale (Figure 3).7 This is in contrast to the previous reliance on stool frequency as the primary differentiating factor for subtyping IBS.8 Rome III suggests that Bristol stool types 1 and 2 be considered constipation and types 6 and 7 diarrhea. There are 4 possible IBS subtypes that are primarily defined by stool form6: • IBS-C • IBS with diarrhea • IBS with mixed stool forms (ie, individuals who have both diarrhea and constipation for at least 25% of bowel movements at a given point in time) • IBS unsubtyped A complete physical exam will help identify signs of systemic and local diseases that might be contributory to constipation. A digital rectal exam will allow for the assessment of the structure and function of the anorectum and pelvic floor muscles and can also help identify other relevant abnormalities.9,10 Figure 3. Bristol Stool Form Scale. Adapted from Lewis SJ and Heaton KW.7 Slow gut transit Type 1 Type 2 Type 3 Type 4 Separate hard lumps Sausage-like but lumpy Sausage-like but with cracks in the surface Smooth and soft Type 5 Soft blobs with clear-cut edges Fluffy pieces with ragged edges, a mushy stool Watery, no solid pieces Type 6 Rapid gut transit Type 7 14 VOL. 1 NO. 1 2007 REVIEWS FOR PRIMARY CARE
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