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Khoury Abbreviations Introduction CIC CKD ESKD FSGS LUT PBS PD PUV UTI VCUG VUR The prevalence of end-stage kidney disease (ESKD) in the pediatric population is approximately 50 cases per million, while cases per million receive renal replacement therapy [1] While the etiology of ESKD remains consistent across time, the prevalence of ESKD has been increasing across all pediatric age groups, particularly among older children [2, 3] In contrast to adults, where glomerulopathy and vasculopathy are the major causes of kidney disease, at least 40% of the chronic kidney disease (CKD) in children is due to congenital urological abnormalities [4–8] As a result, the urologist is an essential member in any team managing pediatric CKD. Similarly, all providers of children with CKD benefit from understanding these urological management principles This chapter will review the common urological conditions that cause kidney failure in children, the diagnosis and pathophysiology of these conditions, and an overview of the urologic management As dialysis represents the treatment phase during CKD between the development of ESKD and kidney transplantation, this chapter will discuss issues present prior to the initiation of dialysis and following kidney transplantation Also, unique implications for pediatric dialysis and kidney transplantation will be addressed, including urology specific pretransplant evaluation and indications for nephrectomy in the CKD patient Clean intermittent catheterization Chronic kidney disease End-stage kidney disease Focal segmental glomerulosclerosis Lower urinary tract Prune belly syndrome Peritoneal dialysis Posterior urethral valves Urinary tract infection Voiding cystourethrogram Vesicoureteral reflux J D Chamberlin Department of Urology, Loma Linda University, Loma Linda, CA, USA Department of Urology, Loma Linda University Children’s Hospital, Loma Linda, CA, USA A Alexander Department of Paediatric Surgery, The Children’s Hospital at Westmead, Sydney, NSW, Australia A J Lorenzo Department of Surgery, Hospital for Sick Children, Toronto, ON, Canada A E Khoury (*) Department of Urology, University of California, Irvine, Orange, CA, USA Department of Urology, Children’s Hospital of Orange County, Orange, CA, USA e-mail: aekhoury@hs.uci.edu © Springer Nature Switzerland AG 2021 B A Warady et al (eds.), Pediatric Dialysis, https://doi.org/10.1007/978-3-030-66861-7_10 131 J D Chamberlin et al 132 rological Causes of Chronic Kidney U Disease The causes of CKD in children may be categorized into congenital and acquired conditions and are listed by anatomical location in Table 10.1 [6, 9–18] Select significant causes are italicized and are the focus of the chapter Posterior Urethral Valves Posterior urethral valves (PUV) are abnormal membranous folds unique to the male prostatic urethra While there are other rare causes of congenital Table 10.1 Urological causes of chronic kidney disease in children, italicized are discussed in this chapter Congenital Acquired a Causes Renal dysplasia Ureteropelvic junction obstruction Ureterovesical junction obstruction Ureteroceles Vesicoureteral reflux Neurogenic bladder Posterior urethral valves Prune belly syndrome Obstructing urolithiasis Obstructing neoplasms Neurogenic bladder Urethral strictures lower urinary tract (LUT) obstruction, such as urethral atresia and obstructive ureteroceles, PUV are undoubtedly the most common They are encountered in of 5000–25,000 live births [19–22] Advances in antenatal diagnosis, improved perinatal medicine, and early PUV management have led to a decrease in the neonatal mortality rate associated with PUV. In spite of these advances and antenatal intervention, there has been little improvement in the proportion of these patients ultimately developing CKD [23] Twenty to sixty percent of boys with PUV will manifest with evidence of CKD in childhood, and 11–51% will eventually progress to ESKD during long- term follow-up [24–27] Increasingly, the diagnosis is suggested in the antenatal period with ultrasound findings of oligohydramnios, bilateral hydroureteronephrosis, a thickened bladder wall, and a dilated posterior urethra (Fig. 10.1) Children without a prenatal diagnosis will present at different ages in the postnatal period with a variety of conditions, including respiratory insufficiency, kidney failure, urosepsis, failure to thrive, poor urinary stream, and urinary incontinence The variation of PUV presentations represents a spectrum of disease, in which less severe forms of obstruction are often detected later in life and may be associated with a smaller impact on overall kidney function b Fig 10.1 Sonographic features suggestive of PUV detected during antenatal evaluation: (a) thick-walled bladder with prominent posterior urethra, the “key-hole” sign; (b) high-grade hydronephrosis 10 Urological Issues in Pediatric Dialysis To prevent or attenuate kidney damage that occurs in utero, prenatal interventions have sought to bypass the urethral obstruction with open diversion, percutaneous diversion, or more recently cystoscopy of the fetal urinary system [28–30] The decision to attempt antenatal intervention should be guided by selective criteria, aided by the analysis of amniotic fluid levels, imaging of renal dysplasia, and fetal urinary markers (sodium, chloride, osmolality, and B2- microglobulin) [31] Vesicoamniotic shunting achieves the required supra-urethral diversion while being minimally invasive, obviating the need for a maternal hysterotomy and fetal vesicostomy Interventions to preserve kidney function would need to be performed early, probably before 22–23 weeks of gestation, although this is not well established [32] Antenatal interventions are associated with a fetal mortality rate that ranges from 33% to 43% Not all the reported deaths are directly related to the intervention, as many deaths recorded may be secondary to ensuing pulmonary hypoplasia These procedures are also associated with significant morbidity in the form of urinary ascites, visceral herniation, shunt malfunction, and shunt migration [33–36] Regardless of the timing of the postnatal presentation, an ultrasound of the kidneys, ureter, and bladder should be the first imaging study obtained The ultrasound will often demonstrate a thick-wall bladder with a prominent posterior urethra, the “key-hole” sign, and high-grade hydroureteronephrosis A voiding cystourethrogram (VCUG) is indicated to confirm the diagnosis of PUV. Typical features on VCUG include a dilated posterior urethra with a clear sharp transition to a normal (or attenuated due to reduced flow) distal channel, an associated valve cusp, a thickened open bladder neck, and a trabeculated bladder Vesicoureteral reflux (VUR) is also often present (Fig. 10.2) While not always predictive of a favorable prognosis, the presence of a urinary “pop-off” has been reported to be protective in some children, by protecting at least one functioning kidney Such “pop-off” mechanisms include unilateral high-grade VUR into an ipsilateral dysplastic/nonfunctioning kidney, a bladder diverticulum, a perinephric urinoma, urinary ascites, and a patent urachus [37–42] 133 Fig 10.2 Features of PUV on VCUG: dilated posterior urethra (white arrow) with a change in caliber compared with the anterior urethra at the site of the valves (blue arrow) Associated bilateral vesicoureteral reflux (asterisk) At birth, many boys with PUV will have preexisting renal dysplasia and will eventually develop CKD regardless of treatment An important goal of PUV management is to delay the onset of kidney failure, by optimizing function of the kidneys, ureters, bladder, and urethra Management is initially directed at systemic stabilization and decompression of the urinary tract Initial urological instrumentation usually involves urethral catheterization in the early neonatal period, prior to the confirmation of the diagnosis The simple intervention of urethral catheterization temporarily bypasses the urinary obstruction, allows accurate monitoring of urine output, and helps avoid emergent surgical intervention, while associated abnormalities are identified and their management optimized A VCUG can then be obtained by instilling contrast through the catheter with subsequent catheter removal to J D Chamberlin et al 134 image the urethra Subsequent definitive urethroscopic valve ablation can be performed in most boys, except for the smallest of infants Premature or small infants, whose urethras will not accommodate a cystoscope, are candidates for alternative forms of decompression Similarly, in the occasional scenario, where valve ablation does not achieve decompression of the upper tracts, surgical diversion above the bladder outlet warrants consideration This may be in part due to a functional ureterovesical junction obstruction as the ureter passes through a markedly thickened detrusor muscle In such situations, segments of the urinary tract can be temporarily brought to the skin, in the form of a vesicostomy, ureterostomy, or pyelostomy (Fig. 10.3) Bacterial colonization of the prepuce of uncircumcised boys predisposes them to urinary tract infection (UTI), particularly in the first year of life Circumcision should be considered at the time of the valve ablation or vesicostomy to significantly decrease the risk of UTI [43] This intervention is often heavily influenced by cultural and religious expectations Following valve ablation, the obstructive process is usually relieved; however, the functional improvements are less predictable Urodynamic findings in these boys remain highly variable and prone to change over time, as kidney function, growth, and the acquisition of continence further challenge the stability of the bladder [44, 45] a b The primary goal of the urological management in PUV is the preservation of upper tract function, which is achieved by ensuring an infection- free urinary tract with a bladder that stores urine at low pressure and empties efficiently The secondary goals include urinary continence and a safe lower tract for those that require kidney transplantation Poorly controlled lower urinary tract (LUT) dysfunction can adversely affect existing kidney function Residual bladder dysfunction in PUV is an independent risk factor for CKD [12, 25] In 1980, Mitchell coined the term “valve bladder syndrome,” identifying deleterious features of lower tract dysfunction that could reliably predict kidney deterioration This term describes the development or persistence of hydroureteronephrosis in the presence of a poorly compliant, thick-walled bladder, incontinence, and polyuria [46] Koff further clarified the role of the bladder in the deterioration of the upper tracts, suggesting that polyuria, insensitivity to overdistension, and high post void residual volumes were the three key factors contributing to kidney deterioration in valve patients [47] An overwhelmed bladder with borderline function may lead to upper tract damage Polyuria, caused by nephrogenic diabetes insipidus, has the potential to overload the bladder of the most diligent voider Insensitivity to overdisc Fig 10.3 Appearance on physical examination of different forms of cutaneous urinary diversion: (a) vesicostomy, (b) distal ureterostomy, and (c) bilateral pyelostomies (patient prone) 10 Urological Issues in Pediatric Dialysis 135 tension contributes to the potential for bladder overload and injury High post void residual volumes decrease the functional capacity of the bladder and are not necessarily the result of myogenic failure [48] Pseudo-residual volumes can be seen in children with PUV and VUR when urine refluxes into dilated ureters during filling and voiding, only to empty back into the bladder immediately after voiding An additional cause of pseudo-residual volumes is a hypertrophied detrusor muscle that creates a functional ureterovesical junction obstruction during bladder filling, which is relieved after voiding, allowing the retained urine to drain from the dilated ureters (Fig. 10.4) [49] With this understanding, hydroureteronephrosis is no longer considered unavoidable in PUV patients Management has become proactive, focused on achieving complete urinary tract emptying (double voiding, timed voiding, and clean Fig 10.4 Issues to consider in the monitoring of patients with PUV. Adequately addressing these problems helps prevent or slow kidney deterioration and provides a conceptual framework upon which to consider interventions and tailor treatment intermittent catheterization [CIC]), optimizing detrusor function (with judicious use of anticholinergics), and the selective use of alpha-blockers to assist voiding [50] On occasion, routine daytime interventions are unsuccessful at preventing hydronephrosis in PUV, due to the polyuria and decreased functional capacity To overcome this, nocturnal CIC or overnight indwelling catheterization has been shown to reduce diuresis, decrease the incidence of UTI, improve urinary continence, and decrease upper tract dilation [47, 51, 52] VUR in PUV children is found in 50–70% of patients and is usually secondary to the obstructed bladder outlet [53, 54] Because of its association with worse renal dysplasia, high-grade reflux can predict higher morbidity and mortality [55, 56] Adequate treatment of the valvular obstruction will lead to spontaneous resolution of VUR in most cases (62%), and therefore VUR should be VUR DIABETES INSIPIDUS URETHRAL OBSTRUCTION POLYURIA HIGH RESIDUAL VOLUMES DECREASED FUNCTIONAL RESIDUAL CAPACITY R E N A L INSENSITIVITY TO DISTENSION RENAL DYSPLASIA MYOGENIC FAILURE INFECTION D A M A G E ... bladder outlet warrants consideration This may be in part due to a functional ureterovesical junction obstruction as the ureter passes through a markedly thickened detrusor muscle In such situations,... reliably predict kidney deterioration This term describes the development or persistence of hydroureteronephrosis in the presence of a poorly compliant, thick-walled bladder, incontinence, and... Table 10.1 Urological causes of chronic kidney disease in children, italicized are discussed in this chapter Congenital Acquired a Causes Renal dysplasia Ureteropelvic junction obstruction Ureterovesical