Gut Interactions with Brain and Environment in Children; First International Symposium on Pediatric Neurogastroenterology Capri, Italy, September 18-20, 1997
Primary care physicians, pediatric neurologists and gastroenterologists are frequently confronted with children with neurologic diseases suffering from defecation disorders. The two largest groups of children with neuromuscular handicaps presenting with a defecation related complaint are children with cerebral palsy and children with spinal dysraphism. Different pathogenic mechanisms play a role in the different groups of children. Children with cerebral palsy and severe developmental delay are often fed dilute formulas or protein hydrolysate formulas by gastrostomy tubes and the absence of dietary fiber may be constipating. A poor defecatory effort is often produced when there is hypotonia and abnormal skeletal muscle coordination. Children with severe brain damage are often confined to bed, and immobility seems to contribute to a slower colonic transit. Opiates and drugs with anticholinergic properties (phenothiazines, tricyclic antidepressant and drugs used to ameliorate urinary incontinence) may be used in neurologically devastated children, with additional impairment of small bowel and colonic motility. Chronic use of laxatives, especially those containing free anthraquinones, can damage colonic submucosal nerves resulting in a cathartic colon. There may be sensory or motor abnormalities due to affected enteric neurons, just as there are abnormalities in the central nervous system. Children with brain damage suffering from constipation have shown a delayed transit in the left colon (1).
Spina bifida occurs in about 1 in 1000 live birth, making it the most common birth defect after trisomy. In this condition, characterized by failure of vertebral arches closure, commonly there is paralysis and lack of sensation below the level of the lesion. The most common type of open spina bifida, the myelomeningocele, is almost universally associated with bowel and bladder dysfunction. The distal colon receives cholinergic input from the sacral pelvic nerves (S2-S4 roots). Hence, it is affected even by low lumbar and sacral lesions. In children with spinal cord injury, the rectoanal inhibitory reflex is usually preserved but the urge for defecation may be lost. The external anal sphincter is often paralytic and the patient is not able to achieve continence when the internal sphincter relaxes. Colonic transit time has been found to be uniformly increased in patients with spinal cord lesions (2). Spinal cord injuries may also cause a loss of the gastrocolonic response, the physiologic increase in colonic motility which follows the ingestion of a meal, providing another mechanism for the onset of constipation. All these pathogenic factors cause children with myelomeningocele to have both constipation and fecal incontinence (3, 4). Although the medical consequences of a defecation disorder are less serious than those deriving from urinary dysfunction or difficulty in ambulation, the psychological toll of such distasteful disability may be devastating to the patients and their family. Fecal incontinence may be the main problem keeping a child with spina bifida from attending ordinary schools (5). In a series of adult patients with myelomeningocele, fecal incontinence was identified as a factor significantly associated with inability to work or to marry (6).
Treatment of constipation in children with cerebral palsy may include dietary modifications aimed at increasing the daily intake of fluids and fibers, behavioral modification techniques, routine administration of stool softeners and oral laxatives, digital stimulation, enemas, rectal irrigations and biofeedback, and surgery. Children with spina bifida and fecal incontinence may also benefit from behavior modification, because many are chronically constipated and have fecal impaction with overflow soiling. The goal of the behavior modification program is to teach the child to self-initiate a bowel movement. It consists in attempting to defecate after the largest meal of the day, offering the child a tangible reward when the attempt is successful, and giving an enema when there is no defecation for two consecutive days (7). In order to achieve an easier evacuation it is useful to teach the child how to grunt and contract the abdominal muscles. Blowing up a balloon is fun for children and will help younger children to produce a more effective Valsalva maneuver. When the child sits on the toilet, it is also important to make sure that the feet reach the floor in order to facilitate the straining.
Initial studies suggested that biofeedback training was helpful to patients who had preservation of some sensorimotor functions in the perianal region and who were old enough and sufficiently motivated to cooperate with the technique (3). Subsequent controlled studies failed to demonstrate a better outcome in children receiving biofeedback treatment in addition to behavior modification (7, 8). The children most likely to benefit from biofeedback were those with lower spinal lesions who maintained some voluntary control of the external anal sphincter. Children with lesions at L-2 or above and those with impaired ability to sense rectal distension were unlikely to achieve control (7). Electric stimulation of the sacral and pudendal nerves using an implantable neuroprosthetic device has also been used in some patients with promising results (9).
In children with spina bifida, the goal of being soiling free may be achieved with an aggressive use of large volume enemas. The enema continence catheter has become part of the bowel management program in most centers dealing with children with anorectal dysfunctions. The enema is used to empty the rectum in a retrograde fashion every 24-48 hours. It consists of a catheter with an inflatable balloon at the end which prevents instant leakage of the enema solution from the incontinent anus and an exterior baffle that locks the balloon in place within the rectum, preventing its displacement. When the total volume of the enema has been administered the catheter is removed and the colonic liquid contents are immediately evacuated (10). Unfortunately, the unaided administration of such enemas is difficult, especially in patients with paralysis of the limbs. In many cases, assistance is needed, reducing the child's independence. Another disadvantage of enemas is that only the left side of the colon is cleansed. To obviate such problems and to achieve longer intervals without fecal soiling, new surgical techniques have been devised to administer antegrade colonic enemas (ACE). The complete cleaning of the entire colon represents the most reliable method to avoid unpredictable “accidents” in an incontinent patient. In 1990, Malone and coworkers devised an appendicostomy for the administration of antegrade enemas in children with fecal incontinence (11). The ACE technique was subsequently extended to include the management of children with intractable constipation. It involves creating a continent appendicocecostomy, through which the cecum can be intermittently catheterized. It was subsequently suggested by Squire et al. that it was not necessary to reverse the appendix. They recommended instead an orthotopic appendicocecostomy, imbricating the cecum around the appendiceal base, and incorporating a skin flap into the tip to form an adequate stoma and assure fecal continence (12). The catheterizable stoma is placed in the right iliac fossa or the level of the umbilicus. A tubularized enteric conduit from ileum or cecum has been created in patients without an appendix. However, there have been reports of stoma stenosis and prolapse, often requiring further surgical intervention. More recently, it has been suggested that a percutaneously inserted cecostomy may provide some of the same benefits offered by the appendicocecostomy without the need for surgery and sparing the appendix, which may be needed for urinary tract reconstruction in children with spina bifida (13). The percutaneous cecostomy is inserted under local anesthesia by the radiologist or the gastroenterologist, in a fashion very much similar to the placement of a percutaneous gastrostomy. If the patient is dissatisfied with the outcome or there is no more need for the tube, it can be removed easily, without need for other closure procedures.
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