Irritable bowel syndrome (IBS) has been estimated to have a prevalence of 10% to 20% and is more common in women and younger individuals. It accounts for 25% to 50% of all referrals to gastrointestinal clinics. Irritable bowel syndrome has distinct diagnostic criteria, including the exclusion of structural or metabolic abnormalities. These patients often have other gastrointestinal, genitourinary, and psychological illness, including gastroesophageal reﬂux disease, fibromyalgia, headache, backache, chronic pelvic pain, sexual dysfunction, lower urinary tract dysfunction, depression, and anxiety. Stressful life events seem to correlate with the onset and exacerbation of symptoms. A detailed history frequently reveals past physical or sexual abuse (46). Currently, specific criteria allow for classification of IBS into diarrhea-, constipation-, and pain-predominant categories (Table 28.4). The constipation variant is most commonly associated with defecatory dysfunction, whereas the diarrhea variant causes fecal incontinence. The pain or spastic variant causes predominantly abdominal discomfort but can also be associated with both defecatory dysfunction and fecal incontinence. After excluding
Table 28.4 Irritable Bowel Syndrome
Recurrent abdominal pain or discomfortb at least 3 days per month in the last 3 months associated with two or more of the following: 1.
Improved with defecation 2.
Onset associated with a change in frequency of stool 3.
Onset associated with a change in form (appearance) of stool a Criterion fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis. b“Discomfort” means an uncomfortable sensation not described as pain. In pathophysiology research and clinical trials, a pain/discomfort frequency of at least 2 days a week during the screening evaluation is recommended for subject eligibility. From Drossman DA, Corazziari E, Talley NJ, et al., eds. Rome III: the functional gastrointestinal disorders. 3nd ed. McLean, VA: Degnon Associates, 2006:885–897, Appendix A, with permission.
organic disease, the criteria listed in Table 28.4 have a sensitivity of 65%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 76% (47).
Functional constipation is a term created by the Rome II criteria as a unifying definition of constipation (Table 28.5). The rationale for the criteria listed in Table 28.5 stems from the variability in patient definitions of constipation (46).
Functional Defecation Disorders Functional defecation disorders are divided into dyssynergic defecation and inadequate defecatory propulsion (colonic inertia). (For the purposes of this chapter, dyssynergic defecation has been included in the structural category of outlet obstruction; however, it is important to recognize that Rome III considers it a functional disorder.) Both of the functional defecation disorders require the presence of functional constipation. Table 28.6 lists the criteria for diagnosing these conditions.
Colonic Inertia/Slow-Transit Constipation Severe constipation, defined as fewer than three stools per week and refractory to therapy, is relatively rare; however, these patients frequently suffer from motility disorders such as global motility disorder and colonic inertia. Women are more likely to be affected than men. Colonic inertia or slow-transit constipation
Table 28.5 Functional Constipation 1. Must include two or more of the following: a.
Straining during at least 25% of defecations b.
Lumpy or hard stools in at least 25% of defecations c.
Sensation of incomplete evacuation for at least 25% of defecations d.
Sensation of anorectal obstruction/blockage for at least 25% of defecations e.