The neurologic systemic factors can be divided into central and peripheral processes. Spinal cord lesions, multiple sclerosis, and Parkinson disease affect the autonomic nervous system. Trauma to the sacral nerves often leads to severe constipation from decreased left-sided colonic motility, decreased rectal tone and sensation, and increased distention. These findings are also seen in patients with meningomyelocele, damage to the lumbosacral spine, and pelvic ﬂoor trauma (21,22). Higher spinal cord lesions result in delayed sigmoid transit and decreased rectal compliance. In these upper motor neuron lesions, colonic reﬂexes are intact, and defecation can be initiated by digital stimulation of the anal canal (23,24). Individuals with multiple sclerosis can have no gastrocolic reﬂex, decreased colonic motility, decreased rectal compliance, and even rectosphincteric dyssynergia (25,26). Constipation worsens with the duration of illness and may be compounded by the side effects of medical therapy. Similar findings of rectosphincteric dyssynergia and medication side effects are present with Parkinson disease.
Among the peripheral neurogenic disorders, dysfunction occurs at the level of the ENS. The ultimate example of this is congenital aganglionosis (Hirschsprung disease). The absence of intramural ganglion cells in the submucosal and myenteric plexuses of the rectum causes loss of the rectosphincteric inhibitory reﬂex. Patients with this illness usually present with functional obstruction and proximal colonic dilation. In most patients, the condition is diagnosed within 6 months of age, although milder cases can be seen later in life.
Other systemic factors to consider are collagen vascular and muscle disorders. Importantly, some of the most commonly used prescription and over-the-counter medications, including aluminum antacids, beta-blockers, calcium channel blockers, anticholinergics, antidepressants, and opiates, cause defecatory dysfunction (Table 28.2). Lifestyle issues, such as inadequate fiber intake and insufficient ﬂuid intake, can exert similar effects independently or in conjunction with other disorders.
Structural abnormalities refer to the obstructive disorders, such as pelvic organ prolapse, perineal descent, intussusception, rectal prolapse, and tumors. Functional disorders are those that do not have an identifiable anatomic or systemic etiology. Most functional disorders are motility disorders, such as slow-transit constipation or colonic inertia, irritable bowel syndrome (constipation predominant), and functional constipation. The Rome III criteria created strict definitions for these idiopathic conditions that are believed to result from the complex interaction of psychosocial factors and altered gut physiology via the gut-braingut axis (27). Patients also may have functional limitations, such as decreased mobility and
Table 28.1 Causes of Defecatory Dysfunction and Fecal Incontinence
Multiple sclerosis, Parkinson disease, stroke, tumor, dementia
Hirschsprung disease, spina bifida, autonomic neuropathy, pudendal neuropathy
Bacterial, viral, parasitic diarrhea
Systemic sclerosis, amyloidosis, myotonic dystrophy, dermatomyositis
Prescription, over the counter
Intussusception, rectal prolapse
Injury (trauma, radiation proctitis)
Table 28.2 Drugs Associated with Constipation cognition. It is important to understand that this classification system is somewhat arbitrary, and several of these conditions are interrelated.