This Month in Pediatric Urology

Article Outline

• Effects of Bladder Over Distension on Voiding Function
• Ureteroscopic Management of Intrarenal Calculi
• The Role of Reflux in Acute Cortical Scintigraphic Lesion and Scar Formation
• Genomic Variants of ATF3 in Patients With Hypospadias
• Copyright

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Effects of Bladder Over Distension on Voiding Function 

Many factors can affect the noninvasive evaluation of bladder function in children including the state of bladder fullness, voiding posture, anxiety, artifacts and lack of privacy. To assess the effect of bladder over distension on pediatric voiding function, Yang and Chang (page 2177) from Taipai, Taiwan evaluated the impact of bladder filling on uroflowmetry curves and ultrasound assessed post-void residual volume (PVR) based on 355 observations in 188 healthy kindergarten children (mean age 4.5 ± 1.0 years). Two observations were requested of each child and additional tests were obtained if the voided volume was less than 50% of the estimated bladder capacity (EBC). Uroflowmetry curve patterns were classified as bell, plateau, staccato or interrupted, and were categorized as bell shaped or nonbell shaped for statistical analysis. Ultrasound assessment of PVR was obtained within 5 minutes after each voiding and was estimated by the equation of height × width × depth × 0.52ml. PVR 20 ml or greater was considered increased.

Based on ROC curves, the authors recommended that over distension of the bladder be defined as EBC 115% or greater. Using this definition, bladder over distension was noted in 35.2% of 355 micturitions, including 61 (32.4%) children who voided once with over distension and 31 (16.5%) who voided more than once with bladder over distension. In those children who demonstrated bell and nonbell shaped voiding patterns the mean bladder capacity (voided volume + PVR) associated with nonbell shaped voiding curves was statistically higher than that of bell shaped curves (133 ± 46% EBC vs 84 ± 385 EBC, p <0.01). Overall, there were statistically more increased PVR values and more nonbell-shaped uroflowmetry curves associated with bladder over distension regardless of whether only the first 188 or all 355 voids were considered. Simultaneous nonbell shaped uroflowmetry curves and increased PVR were observed in only 1.7% to 2.4% of voids without bladder over distension. Peak flow rates correlated positively with increasing voided volumes except in cases of extreme bladder over distension when the peak flow rate decreased. The authors conclude that optimal bladder capacity at the time of noninvasive urodynamic evaluation is important and that only children with persistent nonbell shaped voiding patterns or repeatedly increased PVR at bladder capacity less than 115% EBC require more sophisticated invasive urodynamic studies.

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Ureteroscopic Management of Intrarenal Calculi 

Ureteroscopy has become the treatment of choice for children with ureteral calculi with recent reported success rates ranging from 84% to 100% after a single ureteroscopic procedure. Tanaka et al (page 2150) from Nashville, Tennessee report their 5-year experience with ureteroscopic treatment of intrarenal calculi in 52 kidneys in 50 children (mean age 7.9 years, range 1.2 to 13.6). Based on preoperative imaging with noncontrast computerized tomography, stones were located in the renal pelvis/ureteropelvic junction in 27 (54%) cases, lower pole calices in 13 (25%), nonlower pole calices in 9 (17%) and unspecified renal location in 2 (4%). Mean stone size was 8 mm (range 1 to 16). Stones were removed using a 7.5Fr flexible ureteroscope. Ureteral stents were placed before ureteroscopy in 29 (56%) cases, including 17 in which they were placed solely to passively dilate the ureter preoperatively. At the time of ureteroscopy 18 (35%) ureters were actively dilated and ureteral access sheaths were used in 25 (48%) ureters. The holmium:YAG laser was used to fragment stones in 28 (54%) kidneys. In all other cases stones were removed by basketing alone.

Postoperative stone-free status was documented by renal ultrasound in 18 of 24 patients, by noncontrast computerized tomography in 6 of 14 patients and by abdominal plain film in 1 of 4. The initial stone-free rate from a single ureteroscopic procedure was 50% (25 of 50 cases). Four additional patients with residual stone fragments became stone-free with expectant management, increasing the stone-free rate after single ureteroscopy to 58%. Additional stone procedures were performed in 18 patients, including staged uretreroscopy in 14, and shock wave lithotripsy and/or percutaneous nephrolithotomy in 4. With additional stone procedures the stone-free rate was 92% (46 of 50 cases). No major complications were documented. Multivariate analysis of preoperative stone size, patient age, gender, preoperative stent placement and lower pole location demonstrated that the only significant predictor of initial stone-free rate was preoperative stone size. The authors conclude that ureteroscopy is a safe method of treatment of intrarenal calculi in the pediatric population. Their stone-free rate is comparable to ureteroscopic treatment of adult intrarenal calculi and shock wave lithotripsy treatment of pediatric intrarenal calculi.

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The Role of Reflux in Acute Cortical Scintigraphic Lesion and Scar Formation 

^99mTechnetium dimercapto-succinic acid (DMSA) scintigraphy is the most widely used imaging modality for detection and location of acute pyelonephritic lesions and renal cortical scarring. As such it has proved useful in studying the relationship between acute pyelonephritis, vesicoureteral reflux (VUR) and renal scarring. In a prospective study of 389 patients with a first documented febrile urinary tract infection (UTI) Oh et al (page 2167) from Seoul, Korea compared the rate of acute photon defects and ultimate scar formation between children with and without VUR. All children had temperatures of 38C or higher, positive urine culture and pyuria. An acute DMSA scan was performed within the first week (median 3 days) of diagnosis of a febrile UTI and a followup scan was performed 5 to 7 months (median 6 months) after the acute infection. Acute photon defects were characterized by at least 1 area of decreased focal or diffuse cortical uptake of DMSA with preservation of the renal outline. Defects associated with loss of the cortical outline or loss of renal volume were diagnosed as renal scars. Voiding cystourethrography was performed 3 to 6 weeks (median 4 weeks) after the acute infection in all patients.

Of 389 children enrolled in this study 93 (24%) had VUR and 296 (76%) did not. A total of 164 patients (42.1%) had acute photon defects affecting 194 renal units. Of the 93 patients with VUR 69 (74.2%) had acute DMSA scan defects compared with 95 of the 296 (32.1%) patients without VUR (p=0.0001). A renal scar ultimately developed in 59 of 164 patients (35.9%) with acute photon defects. The rate of renal scarring was significantly higher in patients with (64%) than without (16%) VUR (p=0.0001). The incidence of acute photon defects reflected a positive linear association with reflux grade (p=0.002) but no association was found between reflux grade and scar formation (p=0.262). The authors conclude that, although VUR is not a prerequisite for acute photon defects and subsequent renal scarring in children with febrile UTIs, VUR does significantly increase the risk of both. Higher reflux grades are associated with an increased risk of acute photon defects. However, once the acute pyelonephritic defect occurs, the risk of subsequent renal scarring is the same regardless of reflux grade.

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Genomic Variants of ATF3 in Patients With Hypospadias 

Hypospadias is one of the most common surgical malformations treated by the pediatric urologist. Despite the significant advances in surgical correction of this anomaly during the last 2 decades, the molecular events causing this malformation are only just beginning to be elucidated. Up-regulation of activating transcription factor ATF3 and the role of estrogen in the development have previously been demonstrated. In a continuation of their studies of this candidate gene for hypospadias Kalfa et al (page 2183) from San Francisco, California screened for mutations of the ATF3 gene in patients with hypospadias and characterized the expression profile of ATF3 in the urethral plate of 71 fetuses including 41 with hypospadias (glanular in 3, subcoronal in 3, distal shaft in 5, midshaft in 4, proximal shaft in 8, penoscrotal in 14 and perineal in 3). Control specimens were obtained from foreskins of 30 boys who underwent circumcision for phimosis unresponsive to local corticoid treatment or because of parental preference.

In 10% of patients with hypospadias mutational screening by direct sequencing of coding exons and splice sites of ATF3 revealed 3 genomic variants (C53070T, C53632A, Ins53943A) in or close to exon 6, an important exon that includes splice sites for an alternative transcript that has been implicated in the regulation of the function of ATF3. In contrast, none of these geonomic variants was found in control specimens. Furthermore, immunohistochemistry of tissue obtained from a normal and a hypospadiac fetus demonstrated that ATF3 was not expressed in the proximal and distal urethral plate of the normal fetus. In contrast, a high quantity of ATF3 protein was exhibited in the urethral plate at the level of the ectopic urethral opening in the fetus with hypospadias but not in the normal proximal urethra. The authors conclude that this preliminary experience provides further supportive data for a role of ATF3 in the development of hypospadias and that functional studies of the genomic variants identified in this study are needed for confirmation of the direct implication of ATF3 in the occurrence of hypospadias.