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A proportion of children in the
first grade occasionally wet the bed and 4% wet two or more times a week
[1]. The prevalence estimates of enuresis are highly variable. According
to a study of 10960 children, the respective prevalence of enuresis in
early school ages (7 and 10 years) were 9% and 7% in boys and 6% and 3%
in girls, respectively [2]. Enuresis is categorized as monosymptomatic
(MNE) and non-monosymptomatic (NMNE), respectively and also primary and
secondary forms [3]. Reduced nocturnal bladder capacity has been
suggested in the pathogenesis [4-6].
Methods
Sixty children with enuresis were evaluated over a
two-year period (2007-2008) to define urodynamic abnormalities in
enuretics and to assess correlation between clinical and
ultrasonographic (US) findings with results of urodynamic study (UDS).
Patients were enrolled irrespective of their response to standard
treatments. Children with mental or neurologic disorders were excluded.
Enuresis, its subtypes, and lower urinary tract terminology were defined
as per ICCS criteria [3]. The study was approved by the local ethics
committee.
Forty eight patients fulfilled criteria for full
evaluation (abnormal uroflowmetry; abnormal ultrasound findings: bladder
wall thickening, bladder volume changes or increased post void residual
volume; daytime incontinence; and children
³10 years).
Following informed consent, bladder ultrasound was
used to estimate volume, wall thickness and post void residue
³15 cc. Values were
considered abnormal as compared to the normal range for age [7,8].
Uroflowmetry, cystometrography and electromyography were performed [8].
Intravesical and abdominal pressures were recorded and detrusor
pressure was derived. Electromyography was done using skin electrodes.
The volume at which patient felt the first desire to
void was defined as bladder capacity [9]. Bladder wall thickness
³3 mm in filled
bladder and post void residue of more than 15 mL was defined abnormal;
capacity <65% of the calculated value was defined as small and >150% as
large [3]. Increase in detrusor pressure
³15 cm water as
bladder was filled to a normal functional capacity was defined as low
compliance bladder [3,9]. Detrusor over activity was defined as
involuntary detrusor contractions during the filling phase, involving a
detrusor pressure increase of >15 cm water above baseline [3]. Detrusor
under-activity was defined as a contraction of decreased strength
resulting in prolonged bladder emptying and/or failure to achieve
complete bladder emptying [3]. Overactive bladder was defined as
involuntary detrusor contractions, small bladder capacity and urethral
instability [3, 10]. Patients were divided into two groups and 5
subgroups: normal UDS (group 1) and abnormal UDS (groups 2-5) (Table
I). Clinical details and bladder US between 2 groups were compared
by Chi square test, Fisher exact test and t tests P
£0.05 was
regarded as statistically significant.
Table I Urodynamic Study Findings in 37 Children
| Classification |
Patients (%) |
|
Uroflometry results (No.) |
Bladder capacity |
Bladder compliance |
| Group 1 |
10 (27) |
- |
normal Uroflometry (8) |
Normal |
Normal |
|
|
- |
outflow tract resistant pattern (2) |
|
|
| Group 2 |
15 (40.6) |
- |
Normal Uroflometry (6); |
Low |
Low |
|
|
- |
staccato voiding pattern(3); |
|
|
|
|
- |
DSD pattern (1); |
|
|
|
|
- |
outflow tract resistant pattern (4); |
|
|
|
|
- |
unreportable (1) |
|
|
| Group 3 |
2 (5.4) |
- |
Normal Uroflometry (2) |
Normal |
Low |
| Group 4 |
8 (21.6) |
- |
Normal Uroflometry (6); |
|
|
|
|
- |
outflow tract resistant pattern (1) |
Low |
Normal |
|
|
- |
unreportable (1) |
|
|
| Group 5 |
2 (5.4) |
- |
Normal (1) |
High |
High |
|
|
- |
staccato voiding pattern (1) |
|
|
Results
Of 60 (33 boys) with mean age 8.8 ± 2.3 years (range
5-14 yr) met the inclusion criteria. The mean number of episodes was 5.4
± 2 per week. Enuresis was primary in 50 (83.3%) and secondary in 9
patients; 28 (8 females) had monosymptomatic, while 32 (19 females) had
non monosymptomatic enuresis. A positive family history of enuresis was
seen in 42 (70%). Ultrasound findings were bladder wall thickening (30;
50%), IBW (27; 45%) and post void residence in (9; 15%) patients. BV
changes were reported in 3 (5%) with abnormal UDS. 15 of 27 (55%) with
bladder dysfunction had normal uroflowmetry while it was normal in 8 of
10 (80%) with normal bladder function (P >0.05). Table
II compares details in children with normal and abnormal UDS.
Table II Comparing Clinical Details and Imaging Findings in Children with Normal and Abnormal UDS
|
Variable |
Normal |
Abnormal |
P |
|
(%)
(n=10) |
(%)
(n=27) |
value |
| Age<10 |
8(80) |
18(66.7) |
0.69 |
| Male sex |
5(50) |
16(59.3) |
0.72 |
| Positive
family history |
8(80) |
18 (72) |
1.00 |
| Presence of
bowel symptoms
|
1 (10) |
4(14.8) |
1.00 |
| Daytime
incontinence |
1 (10) |
7 (25.9) |
0.40 |
| Primary
enuresis |
8(80) |
23 (88.5) |
0.60 |
| Abnormal
bladder US |
8 (80) |
26 (96.3) |
0.60 |
|
Monosymptomatic |
7(70) |
10(37) |
0.14 |
| Severe
enuresis |
4(44.4) |
17(70.8) |
0.24 |
Discussion
Dysfunctional voiding is an urodynamic entity
characterized by intermittent or fluctuating uroflow rate due to
involuntary intermittent contractions of the striated muscle of the
external urethral sphincter or pelvic floor during voiding in
neurologically normal individuals [3]. Although NMNE is called as
detrusor dependent enuresis and patients with symptoms suggestive of
bladder dysfunction categorized as NMNE, accurate assessment of bladder
function often necessitates invasive UDS. The most useful
classifications for bladder dysfunction are ICCS and ICSI [3, 10].
The urodynamic classifications are based on
functional state of detrusor during the filling and voiding phases of
cystometry which may be overactive, underactive, and normal or areflexic.
Overactive bladder (OAB) is a common disorder characterized by urgency,
frequency, nocturia with or without urinary incontinence [10,11].
The published literature is not clear about the group
of enuretics who need UDS. We evaluated all enuretics (with MNE or NMNE)
in the first step of the study, but just those who had criteria for
final step of study underwent UDS. Association of enuresis and bladder
dysfunction has been reported [12,4] and small voided volume has been
the most important urodynamic observation [4,13]. Our study revealed
detrusor over- activity in 17 (63%), and small capacity bladder in 23
(80%). Although NMNE is called as detrusor dependent enuresis, we found
abnormal UDS in 17 of 20 (85%) with NMNE and 7 of 17 (41.2%) with MNE (P>0.05).
Similar to Yeung, et al. [4], OAB with
detrusor over-activity was the most common finding. In contrast to our
results, their results cannot apply to all enuretics. Some enuretics
with normal daytime UDS had abnormal findings at night in that study
[4], which suggests that daytime UDS may miss some cases of
dysfunctional voiding. Blatt, et al. [14] found that bladder wall
thickness cannot reliably predict detrusor over-activity, thus it does
not provide an alternative to UDS. Children with enuresis do have UDS
abnormalities, and OAB and detrusor over-activity are the most common
findings. We didn’t find any parameter which can predict enuretics who
need complete urodynamic investigations. Low sample size of our study is
the main limitation and larger studies are recommended.
Acknowledgements: Authors would like to
appreciate Dr Ramin Sadeghi (for editing the paper), Dr Alamdarn and, Dr
Hebrani, (radiologists), Dr Esmaily and Mr. Akhlaghi (Statistics), and
Miss Vafa and Miss Olomy for their help.
Contributors: MN and MH: Study design,
protocol preparation, results interpretation. MN manuscript writing and
editing. MN and MH analysis of data and other laboratory work.
Funding: Mashhad University of Medical Sciences;
Competing interests: None stated.
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What This Study Adds?
• Abnormal urodynamic study is not uncommon
in nocturnal enuresis but clinical parameters and bladder US
findings can not predict which patients are more likely to have
abnormal urodynamic study.
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