Applying the ALARA concept to the evaluation of vesicoureteric reflux

Radiation exposure to infants undergoing voiding cystourethrography: The importance of the digital imaging technology

PURPOSE

To determine the radiation burden to infants undergoing voiding cystourethrography (VCUG) in a single institution and investigate the effect of shifting from analogue to digital imaging that allowed the use of a radiography-free examination protocol.

METHODS

Anthropometric and exposure data were prospectively collected for 35 consecutive infants undergoing VCUG on a digital system with a standardized examination protocol not including radiographs. Thermoluminescent dosimeters were used to determine entrance-skin dose. Monte Carlo simulations and patient-specific anthropomorphic phantoms were employed to determine organ/tissue doses and effective dose (ED). The associated theoretical risk of radiation-induced cancer was determined and compared to the nominal risk of cancer induction. The radiation burden from VCUG on a modern digital system with a contemporary examination protocol was compared to corresponding data reported previously for an analogue system in the same institution.

RESULTS

The median ED from VCUG was found 47 μSv. The associated total life attributable risk of radiation-induced cancer was found 10x10^-6 and 13x10^-6 for boys and girls, respectively. VCUG was found to increase the nominal risk of cancer by a factor of 1.000025 in boys and 1.000034 in girls. Shifting from analogue to digital imaging system resulted in 89% reduction of the radiation burden from VCUG.

CONCLUSION

The theoretical radiation risks for infants undergoing VCUG using a modern digital imaging system and a radiography-free protocol were found to be minor. The transition from analogue to digital equipment resulted in considerable reduction of the radiation burden from VCUG.

Antibiotics for performing voiding cystourethrogram: a randomised control trial

OBJECTIVE

To assess whether antibiotic reduces voiding cystourethrogram (VCUG)-associated urinary tract infection (UTI).

DESIGN

Open-labelled randomised controlled trial.

SETTING

Tertiary paediatric nephrology centre.

PATIENTS

120 children (age 2 months-5 years) undergoing VCUG.

INTERVENTIONS

Children were randomised into group A (antibiotic, n=72) or group B (no antibiotic, n=48) in 3:2 ratio. Group A received oral antibiotic (cephalexin if <6 months or co-trimoxazole if >6 months old) a day prior to VCUG and continued for 1 day post VCUG.

MAIN OUTCOME MEASURES

The main outcome measure is incidence of VCUG-associated UTI. Urine was checked on day 3 after VCUG and UTI was defined as significant growth of a single organism in a symptomatic child.

RESULTS

The median age was 8 months (IQR 13 months) with 68% male. Indication for undertaking VCUG was history of UTI (first UTI in infancy=43, recurrent UTI=49) and congenital anomaly of kidney and urinary tract without any UTI (n=28). Post-VCUG UTI was significantly higher among group B in comparison to group A (17% (n=8) vs 1.4% (n=1); p=0.01, OR=14.2 (95% CI 1.7 to 117)). Multivariate binary logistic regression analysis found an abnormal pre-VCUG ultrasound scan to be a significant independent risk factor for post-VCUG UTI (p=0.02, OR=9.51, 95% CI 1.43 to 63.4). The number needed to treat with antibiotic to prevent one post-VCUG UTI was 6.5, which reduced to 4 if only the group with abnormal pre-VCUG ultrasound scan was included.

CONCLUSIONS

Antibiotic significantly reduces post-VCUG-acquired UTI especially in those with abnormal ultrasound scans.

TRIAL REGISTRATION NUMBER

Clinical Trial Registry of India: CTRI/2017/03/00824.

Controversies Regarding Management of Vesico-ureteric Reflux

The primary goal in the management of a child with urinary tract infection (UTI) is to prevent recurrence of UTI and acquired renal damage. Approximately 15% of children develop renal scarring after a first episode of febrile UTI. Vesico-ureteric reflux (VUR) is diagnosed in 30-40% of children imaged after first febrile UTI. The 'top-down' approach involving ultrasound and dimercaptosuccinic acid scan (DMSA) first after an appropriate interval following UTI, can help in avoiding voiding cystourethrogram (VCUG), an invasive test with higher radiation exposure. The majority view remains that VCUG should be done after the second attack of UTI in girls and first attack of UTI in boys. Although the evidence in favour of antibiotic prophylaxis remains doubtful in preventing renal scars associated with VUR, it remains the first line treatment for high-grade reflux (grade 3-5) with an aim to prevent UTI and allow spontaneous resolution of VUR. Early identification and appropriate treatment of associated bowel bladder dysfunction is an essential part of successful medical management of VUR. Endoscopic treatment of VUR, using a bulking agent, is useful in grade 3 VUR. The main controversy regarding intervention (endoscopic/open surgical intervention) involves absence of strong evidence for these interventions in reducing renal scarring on randomized controlled trials. However, several recent trials have found the surgical interventions to be effective in reducing recurrent pyelonephritis and repeated hospital admissions.

Contemporary Practice Patterns of Voiding Cystourethrography Use at a Large Tertiary Care Center in a Single Payer Health Care System

PURPOSE

Voiding cystourethrogram involves radiation exposure and is invasive. Several guidelines, including the 2011 AAP (American Academy of Pediatrics) guidelines, no longer recommend routine voiding cystourethrogram after the initial urinary tract infection in children. The recent trend in voiding cystourethrogram use remains largely unknown. We examined practice patterns of voiding cystourethrogram use and explored the impact of these guidelines in a single payer system in the past 8 years.

MATERIALS AND METHODS

We identified all voiding cystourethrograms performed at a large pediatric referral center between January 2008 and December 2015. Patients 2 to 24 months old who underwent an initial voiding cystourethrogram for the diagnosis of a urinary tract infection in the first 6 months of 2009 and 2014 were identified. Medical records were retrospectively reviewed.

RESULTS

During the study period 8,422 voiding cystourethrograms were performed and the annual number declined over time. In the pre-AAP and post-AAP cohorts 233 and 95 initial voiding cystourethrograms were performed, respectively. While there was no statistically significant difference in the vesicoureteral reflux detection rate between 2009 and 2014 (37.3% vs 43.0%, p = 0.45), there was a threefold increase in high grade vesicoureteral reflux in 2014 (2.6% vs 8.4%, p = 0.03).

CONCLUSIONS

A clear trend toward fewer voiding cystourethrograms was noted at our institution. This decrease started before 2011 and cannot be attributed to the AAP guidelines alone. While most detected vesicoureteral reflux remains low grade, there was a greater detection rate of high grade vesicoureteral reflux in 2014 compared to 2009. This may reflect a favorable impact of a more selective approach to obtaining voiding cystourethrograms.

The value of direct radionuclide cystography in the detection of vesicoureteral reflux in children with normal voiding cystourethrography

BACKGROUND

Vesicoureteral reflux (VUR) is one of the most important risk factors for urinary tract infection (UTI). Diagnosis and treatment of VUR is important to prevent irreversible complications, such as renal scarring and chronic renal failure. This study was conducted to assess the value of direct radionuclide cystography (DRNC) in the detection of VUR in children with UTI and a normal voiding cystourethrography (VCUG).

METHODS

DRNC was performed in 35 children with a normal VCUG after an episode of febrile UTI who had hydronephrosis or hydroureter, abnormal acute dimercaptosuccinic acid (DMSA) scan results and/or febrile UTI recurrence. This study was conducted in the nephrology department of Mofid Children's Hospital, Tehran (Iran).

RESULTS

The results were statistically analyzed. Among the 70 ureters studied, 33 (49.1 %) were observed to have VUR. Of these, 17 (51.5 %) had mild, 14 (42.4 %) moderate, and 2 (6.1 %) severe reflux. A significant relationship was observed between DRNC results and DMSA renal scan findings (P < 0.05).

CONCLUSIONS

Based on our results, we suggest that DRNC may reveal VUR despite a normal VCUG in children with hydronephrosis, abnormal acute DMSA, and/or recurrent febrile UTI.

Patient entrance surface dose measurements using XR-QA2 Gafchromic films during micturating cystourethrography procedures

The aim of this study was to test the feasibility of using Gafchromic XR-QA2 films in the measurements of patient entrance surface dose (ESD) during the micturating cystourethrogram (MCUG) examination in paediatric patients. Radiochromic films were used to map the entrance dose and to identify the location of peak surface dose (PSD). Direct in vivo measurements of entrance dose were conducted by placing a radiochromic film between the patient and the examination table. The measured ESD values for the commonly performed MCUG fluoroscopic examinations at the authors' institution was in the range of 1.2-7.8 mGy and the PSD in the range of 1.2-8.5 mGy per MCUG procedure for patients with age ranging from 1 to 12 y old. Gafchromic films (XR-QA2) were found to be an efficient and practical dosimetry method that can be easily used to measure clinical patient entrance doses during fluoroscopically guided procedures and potentially in other diagnostic investigations.

Comparison between patient dose arising from photofluorographic and standard fluoroscopic voiding cystourethro graphy in children with urinary tract infection [corrected]

BACKGROUND

Imaging of the urinary system is considered to be responsible for significant radiation in children.

OBJECTIVES

This study was conducted to measure and compare the radiation dose in spot films with photofluorography voiding cystourethrography (VCUG) in children.

PATIENTS AND METHODS

111 [222 Kidney Urinary Unit (KUU)] pediatric patients, aged 1 month to 5 years, with symptomatic urinary tract infection were enrolled in the study. Peak tube voltage (kVp), exposure setting (mAs), focus film distance (FFD), film size and DAP (after the exam) were recorded for all patients. To evaluate the validity of the photographs, we calculated sensitivity, specificity, predictive values and agreement between the two methods using the kappa statistic. If the kappa was greater than 0.75, between 0.4-0.75 or less than 0.4, then the agreement was excellent, good or poor, respectively. P values less than 0.05 were statistically significant.

RESULTS

Vesicoureteral reflux (VUR) was detected in 74 KUU (33.3%) in standard films and in 71 (32%) in photographic images. The photographs had no false positives and 3 false negatives. Therefore, the new method had a sensitivity of 96%, a specificity of 100%, a negative predictive value of 98% and a positive predictive value of 100%. The two-method agreement in the VUR diagnosis for grades 1, 4, 5 and the overall grading were excellent (kappa > 0.83); however, for grades 2 and 3, agreement was 80%, which was good (kappa = 0.64).

CONCLUSIONS

Our study suggests that the high validity and excellent agreement of the photofluorography method in the diagnosis and grading of VUR, which is comparable to spot films and represents a 50%-90% reduction in radiation, makes it the preferred method.

Revised guidelines on management of antenatal hydronephrosis

Widespread antenatal screening has resulted in increased detection of anomalies of the kidneys and urinary tract. The present guidelines update the recommendations published in 2000. Antenatal hydronephrosis (ANH) is transient and resolves by the third trimester in almost one-half cases. The presence of oligohydramnios and additional renal or extrarenal anomalies suggests significant pathology. All patients with ANH should undergo postnatal ultrasonography; the intensity of subsequent evaluation depends on anteroposterior diameter (APD) of the renal pelvis and/or Society for Fetal Urology (SFU) grading. Patients with postnatal APD exceeding 10 mm and/or SFU grade 3-4 should be screened for upper or lower urinary tract obstruction and vesicoureteric reflux (VUR). Infants with VUR should receive antibiotic prophylaxis through the first year of life, and their parents counseled regarding the risk of urinary tract infections. The management of patients with pelviureteric junction or vesicoureteric junction obstruction depends on clinical features and results of sequential ultrasonography and radionuclide renography. Surgery is considered in patients with increasing renal pelvic APD and/or an obstructed renogram with differential renal function <35-40% or its subsequent decline. Further studies are necessary to clarify the role of prenatal intervention, frequency of follow-up investigations and indications for surgery in these patients.

Interactive magnetic resonance imaging for paediatric vesicoureteric reflux (VUR)

OBJECTIVES

The current gold standard for diagnosing vesicoureteric reflux in unsedated infants is the X-ray-based Micturating CystoUrethroGram (MCUG). The aim of this study was to assess the diagnostic performance of interactive MRI for voiding cysto-urethrography (iMRVC).

METHODS

25 infants underwent conventional MCUG followed by iMRVC. In iMRVC, patients were examined using a real-time MR technique, which allows interactive control of image contrast and imaging plane location, before, during and after micturition. Images were assessed for presence and grade of VUR. Parental feedback on both procedures was evaluated.

RESULTS

iMRVC gave a sensitivity of 100%, specificity of 90.5% (95% CI: 81.6-99.4%), PPV of 66.7% and NPV of 100% in this population. There was 88% concordance (44/50 renal units) according to the presence of VUR between the two methods, with iMRVC up-grading VUR in 6 units (12%). There was very good agreement regarding VUR grade: Kappa=0.66±0.11 (95% CI 0.43-0.88). 60% of parents preferred the MRI, but did not score the two tests differently.

CONCLUSION

Interactive MRI allows dynamic imaging of the whole urinary tract without ionising radiation exposure. iMRVC gives comparable results to the MCUG, and is acceptable to parents.

Interactive magnetic resonance voiding cystourethrography (iMRVC) for vesicoureteric reflux (VUR) in unsedated infants: a feasibility study

OBJECTIVES

The current reference standard for diagnosing vesicoureteric reflux is the X-ray-based Micturating CystoUrethroGram (MCUG). The aim of this study was to evaluate the feasibility of performing interactive Magnetic Resonance voiding cysto-urethrography (iMRVC) in un-sedated infants.

METHODS

Twelve infants underwent conventional single-cycle MCUG followed by iMRVC. In iMRVC, patients were examined using an in-house developed fluoroscopic pulse sequence, which allows on-the-fly control of image contrast and geometry. A single acquisition was performed during bladder filling, during and after micturition, with interactive control over imaging parameters. Images were assessed for diagnostic quality and presence of VUR.

RESULTS

Every case of reflux identified with MCUG was identified on iMRVC (100% sensitivity). Over 24 renal units, there was 88% concordance (21/24) according to the presence of reflux between the two methods. There were three "false positives" detected by MRI, giving a specificity of 83.3%, PPV of 66.7% and NPV of 100%.

CONCLUSION

iMRVC is a feasible method for evaluating the renal tract in infants without the need for radiation or sedation. A formal evaluation is required to establish its diagnostic potential.

Outcome of antibiotic prophylaxis discontinuation in patients with persistent vesicoureteral reflux initially presenting with febrile urinary tract infection: time to event analysis

PURPOSE

The use of antibiotic prophylaxis for preventing urinary tract infections has recently been called into question. Some studies support discontinuation of antibiotic prophylaxis in selected groups of children with vesicoureteral reflux. We report on the outcome of this practice in a cohort of patients assembled based on initial presentation with a febrile urinary tract infection.

MATERIALS AND METHODS

We retrospectively reviewed records of patients with persistent vesicoureteral reflux without symptoms suggestive of dysfunctional elimination who discontinued antibiotic prophylaxis after being toilet trained. Exclusion criteria consisted of secondary reflux and previous surgery for vesicoureteral reflux. End points included development of febrile urinary tract infections, renal abnormalities on followup ultrasound and need for further interventions. Infection-free survival was analyzed using the Kaplan-Meier method and compared using the log rank and Cox's tests.

RESULTS

We evaluated 84 girls and 26 boys with a mean age of 5.4 years. Febrile urinary tract infections developed in 10 girls and 1 boy at an average of 17.2 months after discontinuation of antibiotic prophylaxis. In a time to event analysis group comparison showed no significant differences when patients were stratified by gender (p = 0.22), age at antibiotic prophylaxis discontinuation (p = 0.14) or disease laterality (p = 0.23). However, a significant difference was found in number of patients with high grade vesicoureteral reflux (III to V, p = 0.05) and development of symptoms suggestive of bladder/bowel dysfunction (p <0.01).

CONCLUSIONS

Our data support antibiotic prophylaxis discontinuation in the majority of patients with persistent vesicoureteral reflux who initially present with a febrile urinary tract infection, once their elimination habits have been optimized. Those with high grade reflux appear to be at increased risk for recurrent urinary tract infections. Development of dysfunctional elimination symptoms appears to be a risk factor amenable to treatment.

Voiding cystography practices and preferences of North American pediatric urologists

PURPOSE

Little consensus exists regarding the choice of a specific modality of voiding cystography in the evaluation and management of vesicoureteral reflux. We hypothesized that choices of pediatric urologists are based on technical factors of the studies themselves, as well as institutional factors unique to their hospital(s). Therefore, we surveyed pediatric urologists to determine their current practices and preferences of modalities of voiding cystography.

MATERIALS AND METHODS

We mailed an anonymous survey of 40 questions to all fellows of the American Academy of Pediatrics Section on Urology.

RESULTS

Surveys were returned from 186 of 301 fellows (62%). Of the respondents 57% were in academic, 30% in private and 13% in mixed practices. Given a choice of fluoroscopic voiding cystourethrography, radionuclide cystography and voiding ultrasonography, fluoroscopic voiding cystourethrography was preferred by 98% and 96% of respondents for initial evaluation of urinary tract infection in males and females, respectively, 96% for assessment of prenatal hydronephrosis, 54% for followup of vesicoureteral reflux, 59% for screening siblings, and 63% and 66%, respectively, after open and endoscopic correction of vesicoureteral reflux. Voiding ultrasonography was preferred by less than 10% of respondents in all groups, and radionuclide cystography was preferred by the remainder. Voiding images of the urethra, child-friendliness of staff, sensitivity and accuracy were factors most important in choosing a test. Of the respondents 83% reported full-time access to pediatric radiologists at their primary hospital, although a minority had full-time access to pediatric radiologists at additional institutions. Sedation was used in some or most cases by 29%, rarely by 56% and never by 15% of respondents.

CONCLUSIONS

Pediatric urologists prefer fluoroscopic voiding cystography in all situations to evaluate vesicoureteral reflux but the proportion varies by indication. Diagnostic and patient issues are of greater concern than radiation dose. Variability in access to pediatric radiologists and ability to obtain the desired study may also alter ordering practices.

Diagnostic approach to reflux in 2007

There is ongoing controversy regarding the association between vesicoureteric reflux (VUR), recurrent urinary tract infections (UTI), and renal damage. Despite this, routine work up for VUR is still recommended after febrile UTI in most children. The present article reviews the indications and imaging modalities available for VUR diagnosis. Alternative newer techniques like MR cystography and voiding urosonography are discussed. The increasing evidence of the role of DMSA scans in managing children with VUR is highlighted.

Radiation safety and future innovative diagnostic modalities

One must demand an accurate, safe, radiation-free, and noninvasive method for reflux examination as the ideal possibility for reflux screening. Of course the available different imaging modalities are far from this ideal situation, but minimal radiation exposure is indeed a permanent objective. Additionally since all of these studies might be quite stressful to the child and the family, a specially designed and equipped environment is obligatory for the comfort of all involved. An absolute ideal modality in the diagnosis of VUR would be the definition of a certain marker in serum or urine that could identify children with VUR without the need for any interventional screening modality. Therefore more and more efforts have to be made in the future to investigate different markers for this purpose. Since reflux is one of the most frequent congenital conditions pediatric urologist have to deal with potential risks that might lead to renal insufficiency, noninvasive and radiation-free modalities should become the methods of choice, hopefully in the near future.

Therapy Insight: what nephrologists need to know about primary vesicoureteral reflux

Vesicoureteral reflux (VUR) is the abnormal, retrograde flow of urine from the bladder to the upper urinary tract. This disease affects about 1% of otherwise normal children, 30-50% of those who present with urinary tract infections, and approximately 10% with prenatally diagnosed hydronephrosis. Over the past 50 years, tremendous progress has been made in the diagnosis, treatment and management of VUR. The realization that VUR is probably a component of generalized dysfunction of the lower urinary tract (i.e. dysfunctional elimination syndrome) has further enhanced understanding of the disease. This Review covers basic pathogenesis, diagnosis, management, clinical presentation, and current controversies surrounding VUR.

The current evidence based medical management of vesicoureteral reflux: The Sickkids protocol

Vesicoureteral reflux is a common clinical entity and is one of the keystones of the establishment of pediatric urology as a urological subspeciality. There has been continued evolution in the management of vesicoureteral reflux as new insights are gained on its role in renal damage. The optimal treatment algorithm remains controversial. This review aims to highlight the current literature on VUR and its association with urinary tract infections and renal damage. The protocol of management of a child with VUR followed at The Hospital for Sick Children, Toronto is described.