PROGNOSTIC FACTORS FOR LONG-TERM RENAL FUNCTION IN BOYS WITH THE PRUNE-BELLY SYNDROME

Kidney function and transplants in prune belly syndrome: a scoping review

BACKGROUND

Children with prune belly syndrome (PBS) are at higher risk of developing kidney dysfunction and requiring kidney replacement therapy (KRT). While studies have described surgical and survival outcomes in these populations, there has yet to be a focused synthesis of evidence regarding kidney outcomes in this population. Here, the focus of this scoping review was to highlight knowledge gaps and report standards on kidney outcomes in PBS of all ages.

METHODS

Following scoping review methodology, EMBASE, MEDLINE, and Scopus were searched for peer-reviewed literature that describe kidney outcomes in PBS. All studies with a broad set of kidney outcomes (such as kidney function measures, chronic kidney disease (CKD), KRT and associated outcomes) were included. Findings were summarized and qualitatively synthesized.

RESULTS

Of the 436 unique records identified, 25 were included for synthesis. A total of 17 studies (441 patients) reported on kidney insufficiency outcomes, with an estimated prevalence of CKD ranging from 8 to 66%. A total of 15 studies (314 patients) described KRT, primary kidney transplant, and outcomes. Of these, the age for KRT ranged from 4 to 21 years, and graft survival ranged from 22 to 87% by last follow-up (range 1.3-27 years).

CONCLUSIONS

There is significant variability in studies reporting kidney outcomes in PBS which limits meaningful synthesis. There is a need for future studies with comprehensive reporting of confounders and drivers for kidney insufficiency in PBS.

Congenital anomalies of the kidney and urinary tract: defining risk factors of disease progression and determinants of outcomes

Congenital anomalies of the kidney and urinary tract (CAKUT) result from disruptions in normal kidney and urinary tract development during fetal life and collectively represent the most common cause of kidney failure in children worldwide. The antenatal determinants of CAKUT are diverse and include mutations in genes responsible for normal nephrogenesis, alterations in maternal and fetal environments, and obstruction within the normal developing urinary tract. The resultant clinical phenotypes are complex and depend on the timing of the insult, the penetrance of underlying gene mutations, and the severity and timing of obstruction related to the sequence of normal kidney development. Consequently, there is a broad spectrum of outcomes for children born with CAKUT. In this review, we explore the most common forms of CAKUT and those most likely to develop long-term complications of their associated kidney malformations. We discuss the relevant outcomes for the different forms of CAKUT and what is known about clinical characteristics across the CAKUT spectrum that are risk factors of long-term kidney injury and disease progression.

Modern management of and update on prune belly syndrome

Prune belly syndrome (PBS) is characterized by the triad of abdominal flaccidity, a variable degree of urinary tract involvement and cryptorchidism. Most cases of PBS are sporadic and have a normal karyotype, with 95% patients being male. In the last decade, mutations in known genes that regulate embryonic genitourinary myogenesis have been identified and with increasing knowledge of these critical genes involved in bladder maldevelopment, advances can be made in genetic counseling. A multidisciplinary approach is necessary and individualization of care is recommended according to phenotypic severity. Some patients require abdominal and urinary tract reconstruction while others require as little as bilateral orchiopexies. Major treatment objectives are: preservation of renal function and upper urinary tract; polyuria management; adequate bladder emptying; improvement of corporal image and quality of life; preservation of fertility and adequate sexual function. Long-term surveillance of the urinary tract is essential up to adulthood, because functional dynamics can change over time.

Vesicoamniotic Shunting Improves Outcomes in a Subset of Prune Belly Syndrome Patients at a Single Tertiary Center

Objective: Review outcomes of Prune Belly Syndrome (PBS) with the hypothesis that contemporary management improves mortality. Methods: A retrospective chart review of inpatient and outpatient PBS patients referred between 2000 and 2018 was conducted to assess outcomes at our institution. Data collected included age at diagnosis, concomitant medical conditions, imaging, operative management, length of follow-up, and renal function. Results: Forty-five PBS patients presented during these 18 years. Prenatal diagnoses were made in 17 (39%); 65% of these patients underwent prenatal intervention. The remaining patients were diagnosed in the infant period (20, 44%) or after 1 year of age (8, 18%). Twelve patients died from cardiopulmonary complications in the neonatal period; the neonatal mortality rate was 27%. The mean follow-up among patients surviving the neonatal period was 84 months. Forty-two patients had at least one renal ultrasound (RUS); of the 30 patients with NICU RUSs, 26 (89%) had hydronephrosis and/or ureterectasis. Of the 39 patients who underwent voiding cystourethrogram (VCUG), 28 (62%) demonstrated VUR. Fifty-nine percent had respiratory distress. Nine patients (20%) were oxygen-dependent by completion of follow up. Thirty-eight patients (84%) had other congenital malformations including genitourinary (GU) 67%, gastrointestinal (GI) 52%, and cardiac 48%. Sixteen patients (36%) had chronic kidney disease (CKD) of at least stage 3; three patients (7%) had received renal transplants. Eighty-four percent of patients had at least one surgery (mean 3.4, range 0-6). The most common was orchiopexy (71%). The next most common surgeries were vesicostomy (39%), ureteral reimplants (32%), abdominoplasty (29%), nephrectomy (25%), and appendicovesicostomy (21%). After stratifying patients according to Woodard classification, a trend for 12% improvement in mortality after VAS was noted in the Woodard Classification 1 cohort. Conclusions: PBS patients frequently have multiple congenital anomalies. Pulmonary complications are prevalent in the neonate while CKD (36%) is prevalent during late childhood. The risk of CKD increased significantly with the presence of other congenital anomalies in our cohort. Mortality in childhood is most common in infancy and may be as low as 27%. Contemporary management of PBS, including prenatal interventions, reduced the neonatal mortality rate in a subset of our cohort.

Outcomes of renal replacement therapy in boys with prune belly syndrome: findings from the ESPN/ERA-EDTA Registry

BACKGROUND

As outcome data for prune belly syndrome (PBS) complicated by end-stage renal disease are scarce, we analyzed characteristics and outcomes of children with PBS using the European Society for Pediatric Nephrology/European Renal Association-European Dialysis and Transplant Association (ESPN/ERA-EDTA) Registry data.

METHODS

Data were available for 88 male PBS patients aged <20 years who started renal replacement therapy (RRT) between 1990 and 2013 in 35 European countries. Patient characteristics, survival, and transplantation outcomes were compared with those of male patients requiring RRT due to congenital obstructive uropathy (COU) and renal hypoplasia or dysplasia (RHD).

RESULTS

Median age at onset of RRT in PBS was lower [7.0; interquartile range (IQR) 0.9-12.2 years] than in COU (9.6; IQR: 3.0-14.1 years) and RHD (9.4; IQR: 2.7-14.2 years). Unadjusted 10-year patient survival was 85% for PBS, 94% for COU, and 91% for RHD. After adjustment for country, period, and age, PBS mortality was similar to that of RHD but higher compared with COU [hazard ratio (HR) 1.96, 95% confidence interval (CI) 1.03-3.74]. Seventy-four PBS patients (84%) received a first kidney transplant after a median time on dialysis of 8.4 (IQR 0.0-21.1) months. Outcomes with respect to time on dialysis before transplantation, chance of receiving a first transplant within 2 years after commencing RRT, and death-censored, adjusted risk of graft loss were similar for all groups.

CONCLUSIONS

This study in the largest cohort of male patients with PBS receiving RRT to date demonstrates that outcomes are comparable with other congenital anomalies of the kidney and urinary tract, except for a slightly higher mortality risk compared with patients with COU.

27 years of experience with the comprehensive surgical treatment of prune belly syndrome

INTRODUCTION

Prune belly syndrome (PBS) presents with three main features: abdominal wall flaccidity, urological abnormalities and cryptorchidism. As a result, urologists must consider the eventual repair of the abdominal wall flaccidity and urinary tract abnormalities, and the mandatory correction of cryptorchidism, as well as decide whether to perform the procedures in a single comprehensive approach or in multiple steps.

OBJECTIVES

To report experiences with comprehensive surgical management of prune belly syndrome.

MATERIAL AND METHODS

From 1987 to 2014, 46 children with PBS were submitted for comprehensive surgical treatment. According to individual needs, treatment aimed to correct the abdominal flaccidity, reconstruct the urinary tract, and perform bilateral orchiopexy and circumcision, which were performed in one procedure. Urinary tract reconstruction was indicated whenever pyelo-ureteral dilatation with evidence of significant stasis and/or vesicoureteral reflux was associated with recurrent urinary tract infections (UTI). Treatment for this cohort included: 44 abdominoplasties, 40 upper urinary tract reconstructions, 44 cystoplasties associated with three appendico-vesicostomies, 46 bilateral orchiopexies and 36 circumcisions. The median age at surgery was 16 months and children were followed for a median of 143 months.

RESULTS

Abdominal appearance and tonus were improved in 90% of the children after the primary surgery and 100% after reoperation. Upper urinary tract reconstruction was performed in most children and long-term follow-up showed functional stabilization of the urinary tract in about 90% of the children, with progression to renal failure in 10%. Lower urinary tract reconstruction was performed in most children (95.6%); on late follow-up, continence was observed in 81% of them, while incontinence was present in 19% and usually associated with polyuria. Adequate bladder emptying was possible in most boys (82.6%), while the remaining required clean intermittent catheterization. Pre-operative UTI was present in 89.1% and urinary sepsis in 15.2%. Postoperatively, the incidence of laboratorial UTI was significantly reduced to 39.1%, while urinary sepsis was absent. Bilateral orchiopexy was performed in all children, with 85% of the testes becoming normal in size and well located in the scrotum.

CONCLUSIONS

Comprehensive surgical treatment is feasible and has good long-term results. A considerable incidence of reoperations due to complications or progression of the disease was observed. The long-term results for reno-ureteral anatomy and function, bladder function, infection, testicular size and location, as well as abdominal aspect and tonus, show that comprehensive surgery is an adequate method for managing children with PBS.

Urine Stasis Predisposes to Urinary Tract Infection by an Opportunistic Uropathogen in the Megabladder (Mgb) Mouse

PURPOSE

Urinary stasis is a risk factor for recurrent urinary tract infection (UTI). Homozygous mutant Megabladder (Mgb-/-) mice exhibit incomplete bladder emptying as a consequence of congenital detrusor aplasia. We hypothesize that this predisposes Mgb-/- mice to spontaneous and experimental UTI.

METHODS

Mgb-/-, Mgb+/-, and wild-type female mice underwent serial ultrasound and urine cultures at 4, 6, and 8 weeks to detect spontaneous UTI. Urine bacterial isolates were analyzed by Gram stain and speciated. Bladder stones were analyzed by x-ray diffractometry. Bladders and kidneys were subject to histologic analysis. The pathogenicity of coagulase-negative Staphylococcus (CONS) isolated from Mgb-/- urine was tested by transurethral administration to culture-negative Mgb-/- or wild-type animals. The contribution of urinary stasis to CONS susceptibility was evaluated by cutaneous vesicostomy in Mgb-/- mice.

RESULTS

Mgb-/- mice develop spontaneous bacteriuria (42%) and struvite bladder stones (31%) by 8 weeks, findings absent in Mgb+/- and wild-type controls. CONS was cultured as a solitary isolate from Mgb-/- bladder stones. Bladders and kidneys from mice with struvite stones exhibit mucosal injury, inflammation, and fibrosis. These pathologic features of cystitis and pyelonephritis are replicated by transurethral inoculation of CONS in culture-negative Mgb-/- females, whereas wild-type animals are less susceptible to CONS colonization and organ injury. Cutaneous vesicostomy prior to CONS inoculation significantly reduces the quantity of CONS recovered from Mgb-/- urine, bladders, and kidneys.

CONCLUSIONS

CONS is an opportunistic uropathogen in the setting of urinary stasis, leading to enhanced UTI incidence and severity in Mgb-/- mice.

Lower urinary tract development and disease

Congenital anomalies of the lower urinary tract (CALUT) are a family of birth defects of the ureter, the bladder, and the urethra. CALUT includes ureteral anomaliesc such as congenital abnormalities of the ureteropelvic junction (UPJ) and ureterovesical junction (UVJ), and birth defects of the bladder and the urethra such as bladder-exstrophy-epispadias complex (BEEC), prune belly syndrome (PBS), and posterior urethral valves (PUVs). CALUT is one of the most common birth defects and is often associated with antenatal hydronephrosis, vesicoureteral reflux (VUR), urinary tract obstruction, urinary tract infections (UTI), chronic kidney disease, and renal failure in children. Here, we discuss the current genetic and molecular knowledge about lower urinary tract development and genetic basis of CALUT in both human and mouse models. We provide an overview of the developmental processes leading to the formation of the ureter, the bladder, and the urethra, and different genes and signaling pathways controlling these developmental processes. Human genetic disorders that affect the ureter, the bladder and the urethra and associated gene mutations are also presented. As we are entering the postgenomic era of personalized medicine, information in this article may provide useful interpretation for the genetic and genomic test results collected from patients with lower urinary tract birth defects. With evidence-based interpretations, clinicians may provide more effective personalized therapies to patients and genetic counseling for their families.

Prune belly syndrome

The majority of paediatric surgeons will encounter a patient with prune belly syndrome (PBS) only a few times in their clinical practice. There have been many opposing views in the literature regarding the pathogenesis and management of this complex condition. A detailed review was conducted using PubMed to identify key publications involving PBS. This article discusses the evolution of our understanding of the pathogenesis and diagnosis of PBS, including its typical characteristics. We describe the management options available for bilateral intra-abdominal testes, the deficient abdominal wall, the dilated urinary system and examine the evidence base used to support the current approaches employed.

Urological disorders in chronic kidney disease in children cohort: clinical characteristics and estimation of glomerular filtration rate

PURPOSE

Urological disorders are the most common cause of pediatric chronic kidney disease. We determined the characteristics of children with urological disorders and assessed the agreement between the newly developed bedside glomerular filtration rate estimating formula with measured glomerular filtration rate in 586 patients in the Chronic Kidney Disease in Children study.

MATERIALS AND METHODS

The Chronic Kidney Disease in Children study is a prospective, observational cohort of children recruited from 48 sites in the United States and Canada. Eligibility requirements include age 1 to 16 years and estimated glomerular filtration rate by original Schwartz formula 30 to 90 ml/min/1.73 m(2). Baseline demographics, clinical variables and glomerular filtration rate were assessed. Bland-Altman analysis was conducted to assess agreement between estimated and measured glomerular filtration rates.

RESULTS

Of the 586 participants with at least 1 glomerular filtration rate measurement 348 (59%) had an underlying urological diagnosis (obstructive uropathy in 118, aplastic/hypoplastic/dysplastic kidneys in 104, reflux in 87 and other condition in 39). Among these patients median age was 9 years, duration of chronic kidney disease was 7 years and age at first visit with a urologist was less than 1 year. Of the patients 67% were male, 67% were white and 21% had a low birth weight. Median height was in the 24th percentile. Median glomerular filtration rate as measured by iohexol plasma disappearance was 44.8 ml/min/1.73 m(2). Median glomerular filtration rate as estimated by the Chronic Kidney Disease in Children bedside equation was 44.3 ml/min/1.73 m(2) (bias = -0.5, 95% CI -1.7 to 0.7, p = 0.44).

CONCLUSIONS

Underlying urological causes of chronic kidney disease were present in 59% of study participants. These children were diagnosed early in life, and many had low birth weight and growth delay. There is good agreement between the newly developed Chronic Kidney Disease in Children estimating equations and measured glomerular filtration rate in this population.

CKD and bladder problems in children

Approximately 35% of children with CKD who require renal replacement therapy have a significant urological abnormality, including posterior urethral valves, a neuropathic bladder, prune belly syndrome, Hinman syndrome, or severe vesicoureteral reflux. In such children, abnormal bladder function can have a significant deleterious effect on the renal function. In children with bladder outlet obstruction, bladder compliance and capacity often are abnormal, and a sustained intravesical pressure of >40 cm H(2)O impedes drainage from the upper urinary tract. Consequently, in these conditions, regular evaluation with renal sonography, urodynamics, urine culture, and serum chemistry needs to be performed. Pediatric urological care needs to be coordinated with pediatric nephrologists. Many boys with posterior urethral valves have severe polyuria, resulting in chronic bladder overdistension, which is termed as valve bladder. In addition to behavioral modification during the day, such patients may benefit from overnight continuous bladder drainage, which has been shown to reduce hydronephrosis and stabilize or improve renal function in most cases. In children with a neuropathic bladder, detrusor-sphincter-dyssynergia is the most likely cause for upper tract deterioration due to secondary vesicoureteral reflux, hydronephrosis, and recurrent urinary tract infection (UTI). Pharmacologic bladder management and frequent intermittent catheterization are necessary. In some cases, augmentation cystoplasty is recommended; however, this procedure has many long-term risks, including UTI, metabolic acidosis, bladder calculi, spontaneous perforation, and malignancy. Nearly half of children with prune belly syndrome require renal replacement therapy. Hinman syndrome is a rare condition with severe detrusor-sphincter discoordination that results in urinary incontinence, encopresis, poor bladder emptying, and UTI, often resulting in renal impairment. Children undergoing evaluation for renal transplantation need a thorough evaluation of the lower urinary tract, mostly including a voiding cystourethrogram and urodynamic studies.

Initial management of complex pediatric disorders: prunebelly syndrome, posterior urethral valves

Prunebelly syndrome and posterior urethral valves are conditions of detrusor dysfunction associated with antenatal urethral obstruction. The resultant severe hydroureteronephrosis and renal dysplasia initiate a sequence potentially leading to renal failure. This article reviews clinical features and explores neonatal evaluation and treatment for both conditions. A comprehensive approach to initial management aimed at optimal renal preservation and bladder rehabilitation is proposed.

Antenatal hydronephrosis: evaluation and outcome

We present a comprehensive and current review of the etiology, evaluation, treatment, and outcome of antenatal hydronephrosis. When a diagnosis of antenatal hydronephrosis is made, many questions regarding pregnancy, prenatal care, intervention, and what may be expected after birth are raised. Debate and controversy exist on the diagnosis and subsequent evaluation and management of the child with antenatal hydronephrosis. A review of the literature and our own experience with antenatal hydronephrosis are presented in order to guide the physician who is caring for mother and child.