■ Pathophysiology FI may occur when any of the aforementioned mechanisms are disrupted, and is often multifactorial. In the following section, the different etiologies of FI are categorized by risk factors and explained physiologically.
AgingThe elderly are disproportionately affected by FI, as they have more comorbid conditions that cause FI. Structural changes that occur in aging, including anal muscle atrophy and pudendal nerve damage due to decades of straining and childbirth, however, also directly decrease anal muscle bulk and tone. 8 Moreover, anal pressure decreases after age 70, and is lower in elderly women than men. 9
Obstetric injuryMost community-dwelling primary care patients who suffer from FI are postpartum females and have an FI prevalence rate eight times that of males. 10 In this subpopulation, www.tnpj.com The Nurse Practitioner • January 2010 15 F 2.5 CRNP 30. Richter HE, Burgio KL, Brubaker L, et al. Factors associated with incontinence frequency in a surgical cohort of stress incontinent women. Am J Obstet Gynecol. 2005;193(6):2088-2093. 31. Drossman DA, Sandler RS, Broom CM, McKee DC. Urgency and fecal soiling in people with bowel dysfunction.