While the Donguibogam emphasized balance and qi, modern medicine explains anal sphincter function through detailed neurological and anatomical mechanisms. The anus relies on two primary muscles: the internal anal sphincter, which operates involuntarily, and the external anal sphincter, which is controlled voluntarily. These two muscles collaborate closely to regulate defecation.
The internal anal sphincter maintains approximately 70 to 85 percent of resting contractility under normal conditions, preventing passive leakage. Governed by the autonomic nervous system, it functions continuously without conscious thought. In contrast, the external anal sphincter is engaged voluntarily when one actively holds stool, and it is innervated by the somatic nervous system. Together with the pelvic floor muscles, these sphincters respond to an intricate neural network, in which the pudendal nerve and sacral plexus play pivotal roles.
Fecal incontinence stems from diverse causes. The first is nerve injury. The pudendal nerve or surrounding perianal nerves are frequently vulnerable during childbirth. Nervous system diseases such as diabetes, spinal cord injury, and stroke can also impair nerve pathways and diminish sphincter responsiveness. Much like an appliance losing power when an electrical wire is severed, damaged nerves fail to transmit brain signals to the sphincter.
The second cause is direct structural damage to the sphincter. The muscle tissue may be injured or weakened by episiotomy or perineal laceration during delivery, sequelae from hemorrhoid surgery, or anal trauma. Aging is another major contributor: muscle mass and contractility naturally decline over time, and deteriorating collagen fiber elasticity within the sphincter apparatus further diminishes continence. This aligns with the Donguibogam's association between declining kidney qi and the aging process.
Third, chronic diarrhea or constipation can induce or exacerbate fecal incontinence. Chronic diarrhea exerts continuous strain on the sphincter, leading to muscle fatigue, whereas excessive straining from chronic constipation can stretch and injure the sphincter and adjacent nerves. In conditions such as irritable bowel syndrome, where bowel motility is unstable, altered stool viscosity and rapid transit can overwhelm sphincter competence.
Modern clinical practice identifies these underlying factors using anorectal manometry, endoanal ultrasound, and nerve conduction study evaluations to assess sphincter architecture and neurological integrity. Based on these findings, interventions such as pelvic floor muscle exercise, biofeedback therapy, medical management, or surgical procedures—such as sphincteroplasty or artificial sphincter implantation—are applied. Traditional medicine's focus on internal balance and modern medicine's targeted diagnostics both aim toward the shared objective of restoring continence and improving quality of life.
