This chapter focuses on the clinical evaluation and management of passive fecal incontinence (FI), illustrated through a case involving a 70-year-old female presenting with postdefecation soiling. Diagnostic assessment revealed reduced resting anal pressure and thinning of the internal anal sphincter, consistent with internal anal sphincter dysfunction. Despite preserved voluntary squeeze pressure, the patient exhibited symptoms characteristic of passive FI. Conservative treatment with calcium polycarbophil, a bulking agent, effectively reduced leakage by improving stool consistency. Internal anal sphincter dysfunction is a common etiology of passive FI, particularly in older adults, and may result from aging, obstetric trauma, or fibrosis. This chapter discusses the pathophysiology, diagnostic approach—including anorectal manometry and endoanal ultrasonography—and therapeutic strategies for FI. Emphasis is placed on the importance of stool consistency in symptom control and the role of pharmacologic agents as first-line therapy. The chapter also highlights the need for differential diagnosis, particularly in distinguishing overflow incontinence due to chronic constipation. While conservative management is often sufficient, surgical options may be considered in refractory cases. Overall, this chapter underscores the value of individualized, symptom-based treatment in improving patient outcomes and quality of life.