Neurogenic bowel is a condition characterized by the loss of normal bowel function due to a problem with the nervous system. It occurs when nerve damage interferes with the communication pathways that control the colon and rectum. The issue stems not from a defect in the bowel itself, but from the impaired nerve signals that orchestrate its function, hindering the body’s ability to effectively store and eliminate solid waste.
Underlying Neurological Causes
Various neurological events and conditions can damage the nerves responsible for bowel control. Traumatic injuries to the central nervous system are a frequent cause. A spinal cord injury can interrupt signals traveling between the brain and the lower digestive tract, while a traumatic brain injury may damage control centers within the brain. The location of the injury often determines the specific nature of the bowel dysfunction.
Progressive neurological diseases also contribute to neurogenic bowel. Conditions like multiple sclerosis (MS), Parkinson’s disease, and stroke involve the gradual deterioration of nerve tissue, which affects the coordination required for normal defecation. Congenital conditions, such as spina bifida, where the spinal cord does not form properly from birth, can also result in lifelong neurogenic bowel dysfunction.
Symptoms and Classifications
Individuals with neurogenic bowel experience a range of disruptive symptoms. The specific symptoms depend on which part of the nervous system is affected, allowing the condition to be categorized into two primary types based on the location of the nerve lesion. Common symptoms include:
- Constipation
- Bowel incontinence
- Abdominal cramping
- A loss of the sensation that the rectum is full
The first classification is reflexic bowel, also known as an upper motor neuron (UMN) bowel. This type results from damage to the brain or the spinal cord above the sacral level. In this state, the reflex that triggers a bowel movement when the rectum becomes full remains intact. However, the individual loses voluntary control over the external anal sphincter, which stays tight and cannot be relaxed at will. This leads to constipation and the unpredictable, involuntary emptying of the bowel once the rectum is sufficiently stretched.
The second classification is flaccid bowel, or a lower motor neuron (LMN) bowel. This is caused by injury to the lower spinal cord, specifically the sacral segments that control the defecation reflex. This damage eliminates the reflex arc, causing the colon to lose its muscle tone and propulsive movement. The anal sphincter becomes lax and remains open, leading to persistent constipation combined with frequent leakage of stool.
The Diagnostic Process
Confirming a diagnosis of neurogenic bowel involves a thorough evaluation to understand the nerve damage and its impact on bowel function. The process begins with a detailed patient history, where a clinician will ask about symptoms and any underlying neurological conditions. This is followed by a physical examination, which includes a digital rectal exam to assess the tone of the anal sphincter muscle.
To gain a more precise understanding, specific diagnostic tests are often employed. Anorectal manometry is a common procedure that measures the pressures of the anal sphincter muscles, sensation in the rectum, and the neural reflexes needed for normal bowel movements. A balloon expulsion test may be used to evaluate the ability to push out a water-filled balloon from the rectum.
In some cases, imaging studies are used to visualize the structure and function of the anorectal region. Defecography, a type of X-ray or MRI, allows a physician to observe the rectum and anal canal as the patient attempts a bowel movement. These tests help differentiate between reflexic and flaccid bowel types and rule out other potential causes.
Management and Treatment Strategies
Management of neurogenic bowel focuses on establishing a predictable and effective bowel routine to prevent incontinence and constipation. A structured bowel program is tailored to the individual’s specific type of dysfunction and lifestyle. This program involves scheduling regular times for bowel evacuation, often once or twice daily, to train the body to empty at a consistent time.
Diet and fluid intake are adjusted to ensure stool is of a consistency that is easy to pass, which means increasing fiber intake and ensuring adequate hydration. Medications are also a common component of the management plan. Stool softeners, laxatives, or suppositories may be used to help trigger a bowel movement at the scheduled time. For a reflexic bowel, a technique called digital stimulation might be used to activate the defecation reflex manually.
For individuals who do not achieve adequate results with these conservative methods, more advanced interventions may be considered. One surgical option is a colostomy, a procedure that creates an opening, called a stoma, from the large intestine to the surface of the abdomen. Waste is then collected in a bag attached to the stoma, bypassing the dysfunctional rectum and anus.