136 managed conservatively [54, 57] Rarely, surgical intervention is indicated for recurrent pyelone phritis, in cases where LUT dysfunction has been ruled out or controlled The presence of persistent[.]
J D Chamberlin et al 136 managed conservatively [54, 57] Rarely, surgical intervention is indicated for recurrent pyelonephritis, in cases where LUT dysfunction has been ruled out or controlled The presence of persistent unilateral reflux into a dysplastic nonfunctioning kidney in males with PUV, referred to as posterior urethral valve, unilateral vesicoureteral reflux and renal dysplasia (VURD) syndrome, has been associated with a better kidney functional prognosis than what is experienced by standard PUV patients in the short term [55, 58, 59] The dysplastic kidney is thought to provide a protective effect as the renal pelvis and ureter absorb the high pressures generated by the bladder during voiding Despite this protective effect, up to 50% of patients with VURD may develop some kidney scarring, voiding dysfunction, UTI, diurnal incontinence, and long-term hydroureteronephrosis [58] Therefore, every boy with PUV, regardless of the presence of favorable prognostic features, should have close multidisciplinary team follow-up to identify and appropriately treat potential risk factors to the remaining kidney function When necessary, kidney transplantation is successful in patients with PUV with proper evaluation of the bladder for storage and emptying [60] Vesicostomy or bladder augmentation may be needed in some PUV patients prior to kidney transplant Patients with PUV are at a higher UTI risk after kidney transplantation [61] a Vesicoureteral Reflux in the Pediatric Dialysis Patient Reflux nephropathy is kidney damage or abnormal kidney development related to VUR. The kidney damage may be congenital or acquired from repeated insults Congenital sources of reflux nephropathy represent renal dysplasia that coexists with reflux rather than being directly caused by it (Fig. 10.5) Subsequently, postnatal kidney function may be worsened by pyelonephritis, which is facilitated by the reflux of infected urine into the abnormal kidney unit [62– 65] Differentiation between primary and secondary reflux has important therapeutic implications Primary VUR is reflux, which occurs in the absence of secondary functional or anatomical causes, such as PUV, ureteroceles, or neurogenic bladder Secondary reflux is associated with transmission of high bladder pressures to the upper tracts, which can further compromise the kidney parenchyma This section will cover primary VUR, while secondary VUR is discussed under the specific primary conditions Primary VUR accounts for 7–25% of pediatric CKD cases [6, 66, 67] Over half of children with VUR and CKD may require renal replacement therapy by the age of 20 years, suggesting that they have a relatively poor kidney prognosis and deserve particular attention [68] Neither medical nor surgical management can alter the function of b Fig 10.5 Findings suggestive of renal dysplasia: (a) bilateral high-grade reflux detected in infant without a history of urinary tract infections; (b) DMSA scan demonstrates poor function of the left kidney moiety and photopenic defects 10 Urological Issues in Pediatric Dialysis a dysplastic kidney, and treatment should therefore concentrate on preventing further UTI and kidney damage by early diagnosis and treatment of a febrile UTI (pyelonephritis) and correction of bladder and bowel dysfunction Medical treatment may involve increased fluid intake, constipation management, biofeedback, bladder training, and prophylactic antibiotics Increased fluid intake allows for more urine production This, in turn, increases the volume and frequency of voiding, effectively flushing the LUT and mechanically clearing out bacteria Prophylactic antibiotics have long been held as the cornerstone of conservative management of VUR [69] Recent large series have begun to question this conventional wisdom [70–73] Selective use of antibiotics based on UTI risk factors is a reasonable approach Bladder training is helpful for children with an element of dysfunctional voiding The process involves the education and retraining of the voiding process to achieve volitional, regular, and complete bladder emptying Emphasis is placed on the awareness of the pelvic musculature and coordination of the detrusor muscle contraction with sphincter relaxation This training can be enhanced by biofeedback technology that registers and rewards the correct identification and control of pelvic musculature The effective elimination of urine is very closely tied to the effective elimination of feces, i.e., bladder and bowel dysfunction Active management of constipation has been shown to improve voiding dysfunction, incontinence, enuresis, urgency, and UTI frequency [74–76] The surgical approach to the child with VUR and recurrent pyelonephritis who fails to respond to medical management is usually a graded escalation in intervention, which includes circumcision in males, endoscopic sub-ureteric injection of a bulking agent such as dextranomer/hyaluronic acid, and ureteral reimplantation Although surgical reimplantation is more invasive than endoscopic therapy, it carries a higher overall success rate in terms of reflux correction and a lower future reflux recurrence rate This is an important distinction when considering the child with borderline kidney function and a predisposi- 137 tion to recurrent, scarring UTIs These patients may benefit from a more aggressive approach, consisting of early prophylactic circumcision and surgical reimplantation of the ureter As for the reflux patient with CKD who requires dialysis, the indications for medical management or surgical intervention are essentially no different from those patients with normal kidney function One must be aware that once transplanted, these children will be immunosuppressed and have an additional kidney unit Following kidney transplantation, UTIs may occur in children with VUR; approximately 60% of these patients experience at least one episode [77, 78] The risk is highest in the first-year posttransplantation and then decreases over time [79] VUR is associated with acute pyelonephritis in patients with kidney transplants, but this does not necessarily translate to kidney graft loss [79–83] Thus, due to the increased morbidity in the setting of immunosuppression, proper evaluation should address pretransplant vesicoureteral reflux, especially in patients with a history of multiple episodes of pyelonephritis In cases with high-grade reflux and an associated poorly functioning kidney, performing a nephroureterectomy rather than reimplantation should be considered Following kidney transplantation, VUR into the allograft is common and varies according to the ureteral implantation procedure used [79, 80, 84, 85] As such, routine screening for VUR of the transplant kidney is not recommended However, a VCUG is warranted to exclude reflux into the native or transplanted kidneys in the setting of recurrent UTI posttransplant Treatment for posttransplant reflux-associated UTI is initially conservative Patients who fail to improve are candidates for surgical intervention This may involve efforts to stop the reflux or remove a poorly functioning, refluxing native kidney unit Recently, the sub-ureteric injection of dextranomer/hyaluronic acid has gained wide acceptance as a minimally invasive method of correcting VUR. However, when compared to open reimplantation of the ureters, the success rate of ureteric injection is lower in both native and transplant kidneys Reported reflux resolution rates in the transplant kidney following ure- 138 teric injection are only 29–44% [86, 87] Similarly, surgical reimplantation has reported transient obstruction and a persistent increase in serum creatinine in 60% of reimplanted children [85] Given the above issues, combined with the efficacy of conservative management and the concept that adult donor kidneys are less susceptible to the effects of refluxed bacteriuria, surgical intervention is rarely indicated in this patient population J D Chamberlin et al rogenic voiding dysfunction difficult As a result, popular classifications tend to focus on the dysfunction rather than on the underlying cause [89] Wein developed a clinical classification for patients with urinary incontinence, dividing the etiology into two broad categories: a failure of storage and a failure of emptying [90] Adequate storage requires high bladder compliance, reasonable capacity, and the absence of detrusor overactivity combined with adequate sphincteric function Efficient emptying requires a coordinated interaction of detrusor contraction and a Neurogenic Voiding Dysfunction lowering of the outlet resistance Four broad, simplified scenarios exist: (1) a bladder with adeUnder normal bladder circumstances, the detru- quate storage and an outlet with low resistance, sor muscle and the sphincter complex function in (2) a bladder with adequate storage and an outlet a coordinated fashion, which optimizes both with increased resistance, (3) a bladder with urine storage and emptying During the filling inadequate storage and an outlet with low resisphase, the detrusor muscle is relaxed and is com- tance, and (4) a bladder with inadequate storage pliant, as it fills in volume without an increase in and an outlet with increased resistance (Fig. 10.6) bladder pressure As capacity is reached, the With this understanding, it is not uncommon for intravesical pressure gradually rises A full blad- the neurogenic bladder to be either incontinent, der is detected by stretch receptors and perceived continent, or dyssynergic (i.e., lack of coordinain the central nervous system During appropriate tion between detrusor muscle and bladder outlet, voiding, the sphincteric mechanism relaxes in resulting in outlet occlusion in response to detruanticipation of a coordinated detrusor contrac- sor contraction leading to dangerously elevated tion, expelling urine from the bladder If voiding intravesical pressures) needs to be delayed, afferent nerves stimulate Regardless of detrusor compliance, poor tone sympathetic and pudendal outflow activity, initi- in the sphincter mechanism typically results in ating the guarding reflex, which inhibits detrusor urinary incontinence However, as long as the contraction and stimulates the rhabdosphincter to incontinence is associated with low leak point increase outflow resistance [88] Disrupted inner- pressures, there is little risk of damage to the vation can lead to an alteration of this normal, upper tracts In contrast, the “hostile bladder” is coordinated interaction found in situations of a hyperreflexic, poorly Neurogenic bladder dysfunction is an all- compliant, and small capacity bladder that is encompassing term that describes vesicourethral combined with high outlet resistance This resisunits with abnormal neural anatomy or function tance is caused by sphincter hypertonia and Neurological lesions vary considerably in their detrusor-sphincter dyssynergia In these situainfluence on the key bladder functions of storage tions, high filling and voiding pressures are transand emptying Upper motor neuron lesions tend mitted to the kidney, leading to kidney dysfunction to produce a hyperreflexic bladder with sphincter and, if not corrected (especially if associated with dyssynergia Lower motor neuron lesions tend to UTI), permanent kidney damage [91] produce an areflexic bladder with variable Following the diagnosis of neurogenic voidsphincter function Unfortunately, there are many ing dysfunction, initial management is directed at neurological lesions that have various effects on maintaining acceptable bladder storage presthe detrusor muscle, the striated urethral sphinc- sures, ensuring efficient emptying, and preventter, and the smooth muscle of the bladder neck ing UTIs [92] Early medical management and This high variability makes classification of neu- close monitoring are the cornerstones of a suc- 10 Urological Issues in Pediatric Dialysis a 139 b Compliant bladder Poor sphincter tone c d Compliant bladder Increased sphincter tone Fig 10.6 The four broad scenarios based on bladder and sphincter functionality: (a) good bladder compliance with poor sphincter tone, (b) poor bladder compliance with Small volume, poorly compliant bladder Upper tracts protected by low outlet resistance Small volume, poorly compliant bladder Upper tracts threatened by high outlet resistance poor sphincter tone, (c) good bladder compliance with increased sphincter tone, (d) poor bladder compliance with increased sphincter tone Table 10.2 Basic concepts of management for neurogenic voiding dysfunction based on Wein’s classification [90] Facilitate storage Facilitate emptying Bladder Decrease tone Bladder muscle relaxants Increase capacity Bladder augment Increase bladder pressure Trigger zones Bladder training Outlet Increase resistance α-Agonists Mechanical compression Bypass CIC Diversion Decrease resistance α-Blockade Sphincterotomy Bladder neck disruption Urethral dilation CIC Diversion 140 J D Chamberlin et al cessful outcome for these children Patients vary tinent diversion, a safe and reliable method of in their need for specific medical interventions decompressing the upper tracts in young children but should be managed according to their unique with neurogenic bladders [103] urodynamic dysfunction The basic concepts of When continence is the goal of treatment, this management are outlined in Table 10.2 The bladder emptying aided by CIC through the uremajority of children with “hostile bladders” are thra is favored In some children, this is not feamanaged with a combination of CIC to ensure sible, as catheterization may be anatomically regular and complete emptying [93–95]; difficult or impossible (as seen in children with anticholinergics to attenuate neurogenic detrusor urethral strictures), poorly tolerated (in patients overactivity, increase capacity, and decrease tone with a sensate urethra), or difficult to perform [96, 97]; α-blockers to decrease the sphincter (related to body habitus and poor manual dextermuscle tone [98, 99]; and prophylactic antibiotics ity) [9] These patients may benefit from a surgito prevent recurrent UTI cally constructed continent catheterizable Surveillance is a crucial component of the channel, usually fashioned with the appendix management of the neurologically impaired (Mitrofanoff channel) or reconfigured small child In myelodysplasia, the neurological conse- bowel (Monti channel) [104] These conduits quences are often dynamic, with changes taking should be as short and straight as possible, to place throughout childhood but particularly at avoid catherization issues, and enter the bladder puberty when linear growth is accelerated The from an easily accessible, cosmetically approprientire urinary system should be screened regu- ate site Accessibility is the principal goal and is larly for evidence of deterioration Ultrasound of ideally determined preoperatively by the surgeon, the kidneys, ureter, and bladder is useful in patient, and a stoma nurse Cosmesis is a seconddetecting kidney growth failure, scarring, loss of ary concern to function, often best achieved with cortico-medullary differentiation, hydronephro- the stoma placed at the umbilicus (Fig. 10.7) sis, bladder wall thickening, and significant Surgical interventions that augment the bladresidual bladder volumes In the patients who are der are aimed to improve compliance, increase able to void, urinary flow rates may demonstrate capacity, and decrease uninhibited detrusor conabnormal flow curves and, combined with elec- tractions Bladder augmentation with enterocystromyography, may demonstrate detrusor-toplasty is the most commonly used technique, sphincter dyssynergia Urodynamic studies are useful in monitoring bladder dynamics during the filling and emptying phases Spinal MRI is indicated for the initial workup of many of these patients and may be indicated during the surveillance period when changing clinical features suggest the development of a potentially correctable cause, such as a tethered spinal cord If the medical management is ineffective or not tolerated, treatment will need to be escalated Surgical strategies are mainly aimed at addressing three different issues: decreasing bladder outlet resistance, providing alternative access for catheterization, and enhancing bladder capacity and compliance For patients in whom continence is not necessary, strategies aimed at reducing outlet resistance include urethral dilation Fig 10.7 Patient with an appendicovesicostomy [100, 101] and sphincterotomy (in older male (Mitrofanoff channel), performing self-catheterization patients) [102] Vesicostomy produces an incon- through stoma located at the umbilicus 10 Urological Issues in Pediatric Dialysis and it involves the use of a portion of the intestine that has been detubularized, reconfigured into a patch, and then sutured into the defect of a widely incised bladder The gastrointestinal patch can be ileum or colon, but the most commonly used is the ileum, due to its preferred absorptive and secretory profile [105, 106] Following enterocystoplasty, metabolic abnormalities may develop over time, due to the exposure of intestinal epithelium, with its absorptive and secretory characteristics, to urine This is more clinically relevant in children with marginal kidney function To avoid the metabolic impact of the intestinal augments, the bladder may be augmented using tissue naturally lined by urothelium, such as the ureter While most urothelium-lined augmentations create only modest urodynamic improvement, the best improvement is seen with the use of a dilated tortuous ureter of a poorly functioning kidney unit [107, 108] While now uncommonly performed due to inferior results, an auto-augmentation of the bladder was proposed to excise the hypertrophied detrusor muscle, thus creating a diverticulum of bladder mucosa through the detrusor muscle, thereby increasing compliance and capacity A summary of the advantages and disadvantages of common bladder augmentation procedures is provided in Table 10.3 ladder Augmentation and End- B Stage Kidney Disease A severely dysfunctional bladder that has caused or facilitated failure of the native kidneys will put a transplanted kidney at risk If this hostile environment is left untreated, a transplanted kidney will fail Prior to effective reconstruction of the lower urinary tract to create a safe reservoir for urine storage, severe bladder dysfunction was a contraindication to kidney transplantation This has allowed for a successful kidney transplantation in children with stage CKD and severe LUT dysfunction The safety and timing of bladder augmentation in the child with ESKD in the context of kidney transplantation has been controversial 141 Table 10.3 A summary of the advantages and disadvantages of common augmentation procedures Auto-augmentation Lined by urothelium No metabolic sequelae No bowel harvesting Extraperitoneal approach Not reliable at increasing bladder volume Ureterocystoplasty Native ureter Lined by urothelium No metabolic sequelae No bowel harvesting Mucosa backed by muscle Not always available Not always sufficient Additional exposure required (laparoscopic/ open) Colocystoplasty Sigmoid/ileocolic Large diameter Reliable blood supply Mobile segments Ileocecal valve can be used to prevent urinary reflux Can be tunneled Not always available Can impact gut function Bowel surgery required Absorption of urinary waste Lifelong alkalinization required if kidney function impaired Mucus production +++ Bladder stone and UTI risks +++ Higher perforation rate Tumor risk Ileocystoplasty Preterminal ileum Reliable blood supply and length Most compliant bowel segment Hyperchloremic metabolic acidosis Mucus production ++ Bladder stone and UTI risk ++ Vitamin B12 deficiency Tumor risk [109–117] The cumulative graft survival rates for children who underwent major LUT reconstruction seem favorable, despite the lack of standardized follow-up between cohorts [111, 113, 114, 118] The safety of transplantation in patients with bladder augmentation has been established; however, the timing of the reconstruction in relation to the timing of the kidney transplant is debated If bladder augmentation occurs before transplantation, adequate capacity ... treatment, this management are outlined in Table 10.2 The bladder emptying aided by CIC through the uremajority of children with “hostile bladders” are thra is favored In some children, this is... the cornerstone of conservative management of VUR [69] Recent large series have begun to question this conventional wisdom [70–73] Selective use of antibiotics based on UTI risk factors is a reasonable... pelvic musculature and coordination of the detrusor muscle contraction with sphincter relaxation This training can be enhanced by biofeedback technology that registers and rewards the correct identification