Laxatives are the answer for many children experiencing bed-wetting, according to a report from Wake Forest University in Winston-Salem, North Carolina. Investigators report that occult megarectum is a commonly overlooked cause of nocturnal enuresis, and that it can be detected simply by an abdominal X-ray and treated with laxatives.
Lead author Steve Hodges, MD, assistant professor of urology, and coauthor Evelyn Anthony, MD, from the Department of Radiology at the university, found that 30 children and adolescents aged 5 to 15 years seeking treatment for bed-wetting had large amounts of stool in their rectums, even though they reported having normal bowel habits. The report, published online December 14 in Urology, showed that 3 months of laxative therapy cured 25 patients (83%) of their bed-wetting.
The authors note that stool retention reduces bladder capacity (and possibly leads to bladder overactivity) and explains why many therapies aimed at the bladder, such as fluid restriction or alarms, may be ineffective.
A landmark study performed more than 25 years ago showed that constipation, defined as abnormal rectal distension, was a commonly unrecognized cause of enuresis. However, those findings did little to change practice. This definition of constipation differs from that of the International Children's Continence Society (ICCS) guidelines, which rely on bowel habits and stool consistency. The researchers hypothesized that undiagnosed megarectum underlies many cases of nocturnal enuresis, and that laxative treatment may be effective.
They performed a retrospective review of 30 consecutive patients (19 boys and 11 girls) seen in their clinic who presented with a chief complaint of nighttime enuresis. They used a novel method to determine the rectal/pelvic outlet ratio and the Leech criteria for assessing fecal loading, using a plain abdominal radiograph, and compared these findings with the reported constipation history according to the ICCS guidelines. According to the guidelines, a diagnosis of constipation is made based on parents' and children's reports of a bowel movement less frequently than every other day, and on whether the stool consistency is hard.
The rectal/pelvic outlet ratio is the ratio of the maximum diameter of the rectum when distended by stool, divided by the diameter of the pelvic outlet between the obturator stripes at the level of the femoral heads.
All the patients showed rectal distension, based on a rectal/pelvic ratio greater than 1, and 80% met the Leech criteria for constipation. Only 3 of the children or families (10%) described bowel habits consistent with constipation. There was a statistically significant difference between the radiographic findings for fecal loading by the Leech criteria and self-reported constipation (P < .001), with the radiographic findings revealing otherwise unknown constipation. For example, for 27 cases in which the self-reports were negative, radiographs showed constipation in 21.
Initial therapy was a bowel clean-out with polyethylene glycol 3350 laxative (PEG), followed by a daily maintenance dose "titrated to keep the stools the consistency of a milk shake," the authors write. If follow-up imaging at 1 and 3 months showed persistent megarectum, daily phosphate enemas or stimulant laxatives were added to the PEG regimen.
The researchers reported that all of the 4 adolescents and 80% of the younger children in the study were cured of their enuresis by these methods. Persistent enuresis at 3 months with no rectal stool on X-ray was considered a treatment failure.
Because some of the cases may have improved over time on their own, a more rigorous test of the efficacy of laxative therapy would require a randomized trial assigning some constipated children to the therapy and others to an inactive therapy, Dr. Hodges noted in a press release from Wake Forest University. He also advised that any medical therapy for bed-wetting be done under the supervision of a physician.
Proper treatment in many cases may require the recognition of occult megarectum, and physicians would do well to focus on rectal distension, and not just functional constipation. In addition to X-ray, Dr. Hodges suggested, in the press release, that rectal distension could also be determined using rectal ultrasonography, with the advantage of avoiding ionizing radiation. He emphasized the importance of a correct diagnosis to avoid unnecessary surgery and the adverse effects of medication (such as desmopressin), and he urged physicians to first obtain an X-ray or ultrasound.
Urology. Published online December 14, 2011
My view - A fascinating study, that tells us quite a few interesting things about a common, yet under-diagnosed condition. For starters, it states that laxatives may work even without any clinical evidence of constipation (only 10 % parents suggested a history of constipation). Also it suggested a simple test, plain abdomen X ray, could help diagnose children that may benefit from this therapy. I can foresee a problem in making the diagnosis of megarectum though, since the regular radiologist may not be trained in doing so, and we pediatrician's may not be able to make the diagnosis confidently. Finally a very large number of children benefited from this intervention, all 4 adolescents, and 80 % of kids, which is as high or even higher than children using the bed wetting alarm/ DDAVP (desmopressin).
Once large scale trials are conducted, we may want to give a trial of laxatives for most children with bed wetting. On a side note, I found the "consistency of stool of a milk shake" quite informative, and would suggest this to the parents, though this may put some of them off milk shakes for good :)
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