OAB is a manifestation of urgency, regardless of urge incontinence, due to involuntary bladder contraction during the storage period. It is also known as hypersensitive bladder syndrome, urgency syndrome, overactive bladder syndrome, persistent infant bladder, and hypertonicity of the detrusor [9
]. At the 2002 International Incontinence Conference, OAB was defined as urinary urgency regardless of urge incontinence, and it is associated with daytime and nighttime frequency in most cases. Nonetheless, it is not required to prove detrusor overactivity by urodynamic study [8
In a prospective multi-center study performed in 16 Korean medical school hospitals in 2006, the risk factors for OAB were examined. Enuresis, constipation, fecal incontinence, UTI history, and delayed toilet training were considered risk factors associated with OAB [10
]. In our study of OAB, frequency and urgency occurred in 80 and 92.5% of patients, respectively, and it was the most common voiding symptom. Of the OAB risk factors, 45.0% of patients satisfied the Rome III diagnostic criteria, 30.0% corresponded to the Bristol stool scale type 1 or 2, and 57.5% scored higher than 8 points on the Leech score.
It is well known that OAB is closely associated with constipation. Furthermore, the results of studies on voiding symptoms improved only by treating constipation support this [2
]. It has been shown that constipation induces bladder dysfunction by the following mechanism: when the rectum is filled with stools, stretch receptors are stimulated and transmitted to the brain, which induces temporary involuntary contraction of the external anal sphincter and the puborectalis muscles. If defecation is not feasible, the muscles contract voluntarily. As the process becomes repeated, the feces accumulate within the rectum, and this shortens the bladder contraction period and ultimately bladder activity is abolished [16
]. Another hypothesis suggests that when the rectum is distended, it compresses the adjacent bladder and decreases the functional bladder capacity [9
]. Another hypothesis suggests that if stretch receptors are stimulated because of fecal accumulation, diverse patterns of bladder contraction occur and induce bladder instability [2
]. Our study showed no difference in functional bladder capacity in patients with OAB with and without constipation.
Loening-Baucke et al. [1
] reported that in 234 children with chronic constipation, the rate of association between incontinence and UTI was as follows: 29% for daytime incontinence, 34% for nighttime incontinence, and 11% for a history of UTI. With successful treatment of constipation, improvement was seen in 89% of patients with daytime incontinence, 63% of patients with nighttime incontinence, and 100% of patients with recurrent UTI without anatomical abnormalities.
However, the diagnosis of constipation in children differs from that in adults. Diagnosis in children is dependent on the description of guardians, and it remains a challenge clinically. The Rome II diagnostic criteria, which focus on symptoms, have been used from 1999, and the revised Rome III diagnostic criteria were suggested in 2006 [17
Other commonly used methods such as the Bristol stool form scale [18
] and the Leech method assess the level of stools within the intestine by plain radiography [6
]. Additional methods include anorectal manometry, defecography, electromyography, and rectal biopsy.
In our study, children who satisfied more than one of three diagnostic methods (Rome III diagnostic criteria, Bristol stool form scale, and Leech method) were diagnosed as having constipation. Of the 40 OAB patients, 25 had associated constipation (62.5%). Among the 25 OAB patients with constipation, 8 patients satisfied all three diagnostic criteria, and in 6 of the 8 patients (75%), OAB symptoms improved by treatment with osmotic laxatives. In children who satisfied only one diagnostic criterion, therapeutic effects were seen in 76.9%, 76.9%, and 69.6%, respectively.
Our findings suggest that constipation should always be considered in the diagnosis of OAB. Also, together with the subjective Rome III diagnostic criteria, the Bristol stool form scale and the Leech method are noninvasive, economical, simple, and objective methods for the diagnosis of constipation and can be generally applied.