Correlation between sacral ratio and primary enuresis

Implication for health policy/practice/research/medical education: To investigate a possible relation between Primary Enuresis (PE) and Sacral Ratio (SR) in 5-9 aged children, a study was conducted on 118 children within these ages. This study showed that, there was no significant difference between children with PE and those without PE in terms of SR. Multicenter and larger sample size is recommended for definite decision of this finding.


ABSTRACT
Background: Enuresis is defined as the repeated voiding of urine into clothes or bed at least twice a week for at least 3 consecutive months in a child who is at least 5 yr of age and has a high prevalence in school aged children.In primary enuresis (PE) children have never gained control over urination or has been dry for<6months.While in secondary enuresis children have developed incontinence after a period of at least 6 months of urinary control.Objectives: The aim of this study was to investigate a possible relation between PE and sacral ratio (SR) in 5-9 aged children.Patients and Methods: 118 children with aged 5-9 year were enrolled in this casecontrol study.All them were divided into two aliquots groups of 59 patients.The case study (children with PE) and the control (children without PE) groups were matched in age and sex.SR based on antero-posterior plain radiograms of pelvis was calculated.Results were then analyzed using Chi square and student t-test as appropriate.
Results: There were no significant differences between the two groups regarding age and gender.Mean SR in case and control group was 0.89 and 0.90, respectively.Moreover, there was no significant difference between the two groups (p=0.82).Only 1 child (1.6%) in case group showed abnormal SR while this was 7 children (11.9%) in the control group.Conclusions: This study showed that, there was no significant difference between children with PE and those without PE in terms of SR.However, multicenter and larger sample size is recommended for definite decision of this finding.

Background
nuresis is defined as the repeated voiding of urine into clothes or bed at least twice a week for at least 3 consecutive months in a child who is at least 5 yr of age and has a high prevalence in school aged children (5-15%) (1,2).In Primary enuresis (PE) children have never gained control over urination (about 75% of cases), while in secondary enuresis (SE) children have developed incontinence after a period of at least 6 months of urinary control (25% of cases) (3).
Enuresis is mostly common in male gender (9% among 7 year-old and 7% among 10 year-old boys) (4).Normally, about 90-95% of children by the age of 5 year-old can gain control over urination, which is why the diagnosis is usually made upon this age (5).However, children and parents' anxiety over enuresis can cause additional psychilogical problems (6).These children refuse to urinate and this will cause overflow incontinence (7,8).Previous researches have suggested that there is a strong genetic background to enuresis specially in PE (9) although there is a positive family history in half of the SE cases as well (10).It has been stated that, if mother or father has a positive history of enuresis, chances of enuretic child would be 44% and 43%, respectively.This chance will be raised if both parents have a positive history (77%) (9).In about less than 5% of children with PE and only 1% of children with SE, the enuresis is accompanied with a congenital organ disorder.Nearly in all of PE cases, this disorder is a delay in sphincter control mechanism (10).
Sacrum anomalies, like hypoplasia (which is underdevelopment of sacrum) or aplasia (which is congenital lack of sacrum), are accompanied with urinary disorders (11,12).Today, the association between sacral agenesis and the neuropathic bladder, voiding dysfunction with or without secondary reflux is well known (13)(14)(15).The ana-tomical proximity of sacrum and distal ureters might fabricate co-occurrence of developmental abnormalities in both organs.Although plain radiograms are used to investigate bony sacral abnormalities, assessing them can be difficult.In 1995, Pena introduced a novel method to evaluate bony indexes of sacrum as a predictive value of anorectal malformations and voiding dysfunction (5).He called it sacral ratio (SR) which is used by several other investigators thereafter (15,(17)(18)(19).

Objectives
Due to insufficiency of research, this study aimed to evaluate the relation between sacral ratio and primary enuresis.

Patients and Methods
In this study during March 2006-March 2007, we evaluated 5-9 year-old children who were presented in Pediatrics and Urology Clinics of Amirkabir and Valiasr Hospitals, Arak, Iran.The age of 9 year-old was selected as the maximum due to changes made to sacral ratio after the puberty.Control group was consisted of 5-9 year-old children with other complaints such as trauma, stomach pain(stomachache), backache or pelvic pain and no voiding dysfunction, while the case group was consisted of age matched children with enuresis.
To diagnose enuresis and rule any secondary cause out, full urinalysis and urine culture tests, bilateral kidney, bladder and ureters sonography and plain radiography of pelvis were provided.At this work, children with no abnormality in urinalysis (Red blood cells or white blood cells, bacteruria or glucosuria indicative of probable secondary cause), sonography (renal calculi, hydronephrosis or vesico ureteral reflux) and sacral bone (e.g.spina bifida) were enrolled.Patients with any of the above or clinical symptoms like E dysuria, frequency, urgency and hesitancy, were excluded from the case group.Finally, 59 cases were selected for each group.
To calculate the Sacral Ratio anteroposterior (AP) pelvic radiograms were used.Three lines were drawn as instructed below for each radiograph: X: A horizontal line connecting uppermost parts of iliac of sides.
Y: A horizontal line connecting lowermost parts of sacroiliac joints of both sides.
Z: A horizontal line passing the lowermost part of sacrum.
All of these lines should have been parallel to each other, otherwise we excluded the patient from the study (19,20).
SR was defined as proportion of YZ to XY (SR=YZ/XY).Pena was described as a normal limits for SR as ≥ 0.74 in AP and ≥ 0.77 in lateral view (5).
All radiographic images were obtained and assessed by the same radiologist.None of the cases had bowel preparation.Therefore, to get quality radiograms for detecting the tip of sacrum, a direct digital radiography system was used in most of the patients.Due to ethical issues, no supplementary lateral or oblique views were ordered and a few patients with doubtful radiograms were excluded from the study and were replaced with similar matching cases.Since obtaining lateral views meant additional X-ray exposure, the study was restricted to assess SR ratio in AP views.
The results were analyzed by SPSS software, version 15.00, using students t-test, and the Chisquare test as appropriate, depending on whether the data were continuous or not.p<0.05 considered to indicate statistical significance.
This study is approved by Ethical committee of Arak University of Medical Sciences and a written consent was obtained from all of parents whose children were involved in the study and they were free to leave the study.In all stages we were loyal to Helsinki declaration principles.
The mean SR in case and control group was 0.89 and 0.90, respectively.There was no significant difference in terms of mean SR in case and control groups (p=0.82).

Discussion
In this study we compared the SRs of 59 children with PE and 59 children without enuresis.Mean SR of both groups seems to have no apparent relation and the two groups were alike.Although there was no relation in the case group in terms of sex and normal or abnormal SR.Girls were more likely to have normal SR than boys in the control group.
This was against the results of Kajbafzadeh and Rasuli, who compared SRs of children (aged less than 15) with and without urinary or fecal complaints (21).In their case group (193 patients), SR was abnormal in 13.2% and 13.3% of the patients with urinary and fecal complaints, respectively, while it was 0.5% in control group.Therefore, SR was addressed as a valuable index for prediction of urinary or fecal complaints.
Warne et al. evaluated 50 pelvic radiographs (30 children with anorectal abnormality and 20 healthy children) (22).Although they concluded that SR is a good measure for sacral development but the range of SRs they used was too wide to demonstrate the difference of normal and abnormal SRs in a fashionable way.Khalegh Nejad (23) and Ahmadi (24).suggested that SR is a good predictor of fecal continence after colorectal surgery and it is a valuable index for sacral development.
The heterogeneity between our result and others can be due to sample size limitations.In addition, Amirkabir and Valiasr Hospitals are referral centers so the results may not be extendable to a wider population.

Conclusions
This study showed no apparent correlation between primary enuresis and Sacral Ratio.However, finding a correlation would be an easy and cost effective way to clinically diagnose and treat enuresis.A multicenter study with larger sample size, to investigate a correlation between primary enuresis and Sacral Ratio is suggested.