The pelvic floor is a complex, hammock-shaped group of muscles and connective tissues located at the base of the pelvis. These muscles provide support for the bladder, rectum, and in women, the uterus. Constipation is defined by infrequent bowel movements or the difficult passage of stool, often characterized by excessive straining or a feeling of incomplete evacuation. The pelvic floor is a frequent, yet often overlooked, cause of chronic constipation, particularly when the issue relates to the final act of elimination.
The Pelvic Floor’s Essential Role in Bowel Movements
Normal defecation relies on a precise, coordinated sequence of muscular actions involving the abdomen and the pelvis. The process begins when the rectum fills with stool, signaling the brain that it is time to empty the bowels. To maintain continence at rest, a specialized muscle called the puborectalis forms a sling around the rectum, creating a sharp bend known as the anorectal angle. This acute angle acts as a mechanical barrier, preventing the involuntary leakage of stool.
When a person attempts to have a bowel movement, this muscular coordination must reverse itself. The abdominal muscles and diaphragm contract to increase pressure within the abdomen, which helps push the stool downward. Simultaneously, the pelvic floor muscles, including the puborectalis, must lengthen and relax completely. This relaxation is what allows the anorectal angle to straighten, effectively opening the pathway for the stool to pass without obstruction.
How Pelvic Floor Dysfunction Leads to Constipation
Constipation caused by pelvic floor dysfunction (PFD) is often categorized as outlet obstruction or functional constipation, also known as dyssynergic defecation. This condition occurs when the pelvic floor muscles fail to relax or, in a paradoxical action, contract or tighten when they should be relaxing during the attempt to defecate. This failure of coordination prevents the anorectal angle from straightening out, essentially keeping the “gate” closed.
The muscles act in opposition to the abdominal pushing, creating a functional blockage near the anal opening. This paradoxical contraction, or anismus, means the harder a person strains, the tighter the muscles become, exacerbating the difficulty of passing stool. This mechanical impedance traps the stool in the rectum, leading to chronic constipation. While a weak pelvic floor can cause issues like incontinence, this hypertonic, non-relaxing muscular pattern is the more common cause of PFD-related constipation.
Recognizing Symptoms and Confirming Diagnosis
The symptoms associated with PFD-related constipation are specific to the mechanical obstruction at the outlet. Patients frequently report excessive straining during bowel movements, which often feels unproductive. A persistent feeling of incomplete evacuation is also common, suggesting that the stool was not fully passed due to the muscular blockage.
Some individuals may need to use manual maneuvers, such as pressing on the perineum or around the anus, to assist in the passage of stool. When initial treatments like increased fiber and laxatives fail, specialized diagnostic tests confirm the mechanical problem. Anorectal manometry measures the pressures and coordination of the muscles during simulated defecation. Defecography uses imaging to visually track the movement of the rectum and pelvic floor muscles, confirming the failure of the anorectal angle to straighten.
Targeted Treatment for Functional Constipation
The most effective approach for functional constipation resulting from PFD is specialized physical therapy, specifically biofeedback training. Biofeedback is a non-surgical method that uses sensors, often inserted into the rectum, to measure pelvic floor muscle activity. The patient watches a monitor that displays their muscle activity in real-time, allowing them to understand when they are contracting or relaxing.
Under the guidance of a trained therapist, the patient learns to consciously relax the puborectalis and external anal sphincter muscles during simulated defecation attempts. This training helps re-establish the correct neuromuscular coordination and reverse the dysfunctional straining pattern. While lifestyle adjustments, such as optimizing fiber and hydration, are recommended, biofeedback addresses the underlying muscular incoordination, making it the primary treatment pathway.