The anal sphincter is a muscular structure composed of two distinct parts. The internal anal sphincter is a ring of smooth muscle that operates involuntarily, maintaining constant resting pressure for continence. The external anal sphincter is made of skeletal muscle, which is under voluntary control, allowing a person to consciously defer or initiate a bowel movement. Relaxation is sought when excessive tension, known as hypertonicity or spasm, causes conditions like chronic anal fissures, severe constipation, or pelvic pain. A tight sphincter reduces blood flow to the anal lining, preventing the healing of tears and creating a cycle of pain and muscle contraction.
Modifying Diet and Hydration
Dietary adjustments are the first step in reducing the strain that triggers anal sphincter spasm. The goal is to ensure stool is soft and easy to pass, preventing the need for excessive pushing during a bowel movement. This requires consistently consuming adequate amounts of both soluble and insoluble fiber.
Soluble fiber dissolves in water, creating a gel-like substance that softens the stool. Insoluble fiber attracts water, adding bulk and promoting faster movement through the intestinal tract. These fibers must be paired with sufficient fluid intake, typically water, as fiber can otherwise absorb moisture from the colon and worsen constipation. Natural stool softeners, such as prunes, are recommended because they contain both fiber and sorbitol. Sorbitol is a sugar alcohol that works as an osmotic agent, drawing water into the intestines to create a mild laxative effect that aids in softening the stool.
Conscious Physical Relaxation Techniques
Physical techniques and training can help retrain the body to consciously relax the pelvic floor and anal sphincter muscles. Changing defecation posture is a simple yet effective modification to reduce strain. When sitting on a standard toilet, the puborectalis muscle maintains a kink in the anorectal canal, which helps maintain continence.
Elevating the feet with a footstool raises the knees above the hips, mimicking a natural squatting position. This posture straightens the anorectal angle, allowing the puborectalis muscle to relax more completely and enabling easier passage of stool. Deep diaphragmatic breathing is another powerful tool that directly influences the pelvic floor muscles. During a deep inhale, the diaphragm descends, increasing abdominal pressure and causing the pelvic floor, including the anal sphincter muscles, to naturally lengthen and relax.
This coordinated movement is the basis for “reverse Kegels,” which are conscious exercises focused on relaxation rather than contraction. To perform a reverse Kegel, one intentionally practices letting the pelvic floor muscles drop or lengthen, similar to the initial feeling of starting to urinate or pass gas. This down-training is the opposite of a traditional Kegel and improves the ability to release tension, a skill often lost in individuals with chronic spasm.
For those struggling to gain awareness of these muscles, biofeedback therapy offers non-invasive training. This involves using a probe with sensors to provide real-time visual or auditory feedback on a screen. The feedback shows the patient when their muscles are contracting or relaxing, improving their ability to consciously control the sphincter.
Prescription Treatments and Medical Procedures
When conservative and behavioral methods fail, medical interventions prescribed by a healthcare provider may be necessary. Topical muscle relaxants are a common initial treatment, working chemically to ease the spasm of the internal anal sphincter. These medications include nitroglycerin ointment, a nitrate that releases nitric oxide, which directly relaxes smooth muscle tissue. This mechanism reduces resting anal pressure and improves blood circulation, aiding in the healing of conditions like fissures.
Other topical options are calcium channel blocker creams, such as diltiazem or nifedipine, which also promote muscle relaxation. These are sometimes preferred due to a lower incidence of side effects, particularly headaches, compared to nitroglycerin. If topical agents are unsuccessful, the next step may involve Botulinum Toxin injections. This procedure involves injecting the toxin directly into the internal anal sphincter muscle, where it temporarily blocks nerve signals, causing localized relaxation for several months. This temporary relaxation is often enough to break the cycle of pain and spasm, allowing chronic tears to heal.
For severe, chronic cases that do not respond to non-surgical treatments, a surgical procedure called lateral internal sphincterotomy (LIS) may be considered. This operation involves a surgeon making a small, controlled cut into a portion of the internal anal sphincter muscle. The goal of LIS is to permanently reduce the high resting pressure within the sphincter, which is highly effective in promoting healing. While it has a high success rate, the procedure is irreversible and carries a small risk of affecting long-term continence.