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Pediatrics: Vesicoureteral Reflux: Difference between revisions

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== Embryology of the Ureterovesical Junction ==
== Embryology of the Ureterovesical Junction ==


* If the ureteric bud reaches the urogenital sinus too late (because of budding late), insufficient rotation occurs, resulting in an ectopic ureter
* '''Primary vesicoureteral reflux is due to early budding that results in a lateral and high insertion in the bladder'''
* '''A ureteral bud that is laterally (cranially) positioned from a normal takeoff at the trigone offers an embryologic explanation for primary reflux,''' whereas those inferiorly (caudally) positioned are often obstructed.
**'''A ureteral bud that is laterally (cranially) positioned from a normal takeoff at the trigone offers an embryologic explanation for primary reflux,''' whereas those inferiorly (caudally) positioned are often obstructed.
*'''Ectopic ureter is due to late budding''' (the ureteric bud reaches the urogenital sinus too late) that results in insufficient rotation and ectopic ureter


== Functional Anatomy of the Antireflux Mechanism ==
== Functional Anatomy of the Antireflux Mechanism ==
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* '''<span style="color:#ff0000">VUR due to fundamental deficiency of the longitudinal muscle of the intravesical ureter resulting in an inadequate valvular mechanism while the remaining factors (bladder and ureter) remain normal or relatively noncontributory'''
* '''<span style="color:#ff0000">VUR due to fundamental deficiency of the longitudinal muscle of the intravesical ureter resulting in an inadequate valvular mechanism while the remaining factors (bladder and ureter) remain normal or relatively noncontributory'''
** VUR may be a normal variant in the population but becomes clinically relevant only in some because of a predisposition to UTI. This is supported by the observation that VUR without infection is of questionable clinical significance
** VUR may be a normal variant in the population but becomes clinically relevant only in some because of a predisposition to UTI. This is supported by the observation that VUR without infection is of questionable clinical significance
* '''Genetics'''
* '''Risk Factors'''
** '''66% rate of reflux in the offspring'''
**'''Genetics'''
*** Tendency for an autosomal dominant pattern of inheritance; probably many genes are involved
*** Tendency for an '''autosomal dominant pattern of inheritance'''; probably many genes are involved
** '''Prevalence of VUR in siblings to be ≈32%'''
***'''Prevalence of VUR in'''
*** Because the renal consequences of VUR are at issue, rather than reflux itself, siblings may be better served by non-invasively (ultrasound) screening for cortical abnormalities first, and screening for VUR if history of compounding factors such as UTI or bowel and bladder dysfunction are manifested.
****'''Offspring: ≈65%'''
**** By taking into account the imaging of the kidneys first, as well as the patient’s age and history of UTI, a rational top-down approach to sibling reflux screening emerges.
**** '''Siblings: ≈30%'''
**** It cannot be assumed that all cortical abnormalities in siblings with VUR are acquired. The lack of prospective studies should temper the notion of mass screening of siblings
***** Screening in siblings
**** In any sibling, however, in whom reflux is diagnosed, the indications for treatment remain the same as for general reflux in the pediatric population.
******Because the renal consequences of VUR are at issue, rather than reflux itself, siblings may be better served by non-invasively (ultrasound) screening for cortical abnormalities first, and screening for VUR if history of compounding factors such as UTI or bowel and bladder dysfunction are manifested.
******* By taking into account the imaging of the kidneys first, as well as the patient’s age and history of UTI, a rational top-down approach to sibling reflux screening emerges.
******* It cannot be assumed that all cortical abnormalities in siblings with VUR are acquired. The lack of prospective studies should temper the notion of mass screening of siblings
******* In any sibling, however, in whom reflux is diagnosed, the indications for treatment remain the same as for general reflux in the pediatric population.


=== Secondary Reflux ===
=== Secondary Reflux ===
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#* Reflux is present in 48-70% of patients with PUV patients
#* Reflux is present in 48-70% of patients with PUV patients
# '''<span style="color:#ff0000">Neurogenic bladder'''
# '''<span style="color:#ff0000">Neurogenic bladder'''
#* '''Spina bifida, in particular, is at risk for VUR'''
#* '''<span style="color:#ff0000">Spina bifida, in particular, is at risk for VUR'''
#** '''Special attention for the potential for occult spinal dysraphism is warranted during evaluation of any child with UTI'''
#** '''Special attention for the potential for occult spinal dysraphism is warranted during evaluation of any child with UTI'''
#* '''Urodynamic risk factors for VUR:'''
#* '''Urodynamic risk factors for VUR:'''
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== Diagnosis and Evaluation ==
== Diagnosis and Evaluation ==


* '''UTI'''
=== Labs ===
** '''Confirmation of UTI''' is paramount in the appropriate management of the patient with VUR
 
* '''<span style="color:#ff0000">UTI'''
** '''<span style="color:#ff0000">Confirmation of UTI is paramount in the appropriate management of the patient with VUR'''
*** The method of urine collection and the presence of pyuria are of utmost importance in the diagnosis of UTI to avoid false-positive culture results
*** The method of urine collection and the presence of pyuria are of utmost importance in the diagnosis of UTI to avoid false-positive culture results
*** '''US of the kidneys and bladder can be considered a reasonable minimum evaluation in the infant or child after a UTI'''
*** '''<span style="color:#ff0000">US of the kidneys and bladder can be considered a reasonable minimum evaluation in the infant or child after a UTI'''
**** '''Older children who present with asymptomatic bacteriuria or UTIs that manifest solely with lower tract symptoms can be screened initially with US alone,''' reserving cystography for those with abnormal upper tracts or recalcitrant infections.
**** '''Older children who present with asymptomatic bacteriuria or UTIs that manifest solely with lower tract symptoms can be screened initially with US alone,''' reserving cystography for those with abnormal upper tracts or recalcitrant infections.
***** The presence of structural renal anomalies or significant asymmetry would support proceeding with a cystogram.
***** The presence of structural renal anomalies or significant asymmetry would support proceeding with a cystogram.
* '''Assessment of the Lower Urinary Tract'''
 
** '''Cystogram'''
=== Imaging ===
*** '''VCUG and radionuclide cystogram (RNC) are the two common forms of direct cystography and constitute the present-day gold standard approaches to detect VUR'''
 
**** '''Both VCUG and RNC require catheterization'''
==== Lower Urinary Tract ====
**** '''RNC'''
* '''<span style="color:#ff0000">Modality'''
***** '''Advantages (2):'''
**'''<span style="color:#ff0000">Voiding cystourethrogram (VCUG) and radionuclide cystogram (RNC)'''
*****# '''Reduced radiation requirements'''
***Two most common forms of direct cystography
*****#* RNC has historically been described as a technique that requires a significantly lower dose of radiation than a regular VCUG, but the advances with modern digital techniques have significantly narrowed the difference between these two imaging modalities.
***'''<span style="color:#ff0000">Present-day gold standard approaches to detect VUR'''
*****# '''Greater sensitivity for grade 2 to 5 VUR'''
***'''Both VCUG and RNC require catheterization'''
***** '''Disadvantage:'''
***'''Radionuclide Cystogram (RNC)'''
****** '''Provides much less anatomic detail than does a VCUG'''
**** '''Advantages (2):'''
**** More recently, to eliminate the need for ionizing radiation, some studies have demonstrated a growing interest in US detection of VUR using either color Doppler imaging
****# '''Reduced radiation requirements'''
*** Direct imaging of VUR is affected by several parameters which include''':'''
****#* RNC has historically been described as a technique that requires a significantly lower dose of radiation than a regular VCUG, but the advances with modern digital techniques have significantly narrowed the difference between these two imaging modalities.
***# Bladder contraction during voiding
****# '''Greater sensitivity for grade 2 to 5 VUR'''
***# Fluid volume instilled into the bladder
**** '''Disadvantage:'''
***# Presence of infection and therefore inflammation of the UVJ mucosa.
***** '''Provides much less anatomic detail than does a VCUG'''
**** '''Even during voiding, reflux may not be demonstrated on a single filling-voiding cycle'''. Several studies have demonstrated a roughly 12-20% '''greater detection rate for VUR if a cyclic study is performed'''
*** '''Voiding Cystourethrogram (VCUG)'''
*** '''Passive reflux (VUR during filling of the bladder) is generally considered a poor prognostic sign for reflux resolution and suggests the presence of a fixed decompensation of the UVJ.'''
****'''Technique'''
**** Filling assumes far lower intravesical pressure than that of voiding
*****Bladder contrast is instilled by gravity after urethral catheterization. Bladder capacity is recorded when contrast influx ceases. Static images record bladder contour, presence of diverticula or ureteroceles, grade of reflux, configuration and blunting of calyces, and intrarenal reflux. Passive or active reflux is demonstrated dynamically during fluoroscopy while filling and voiding, respectively. In addition, bladder neck anatomy, funneling or dilation, and urethral patency are parameters derived from the VCUG.
**** '''Passive reflux is common finding in patients with acquired or neurogenic voiding dysfunction'''
***** '''Delayed or postvoid films are crucial in documenting clearance of contrast from the upper tracts because retained contrast, particularly with dilated pelvicalyceal systems, could signify the presence of a concomitant UPJ obstruction (UPJO)'''
*** '''Cystogram during active infection'''
**Ultrasound
**** '''The general consensus has been to delay the voiding study for at least a week or longer to allow for adequate recovery from the acute infection episode.'''
***More recently, to eliminate the need for ionizing radiation, some studies have demonstrated a growing interest in US detection of VUR using either color Doppler imaging
***** Evoking reflux during an active cystitis, by definition, will transmit bacteria to the upper urinary tract and renal pelvis and risks iatrogenic pyelonephritis.
* '''Findings'''
**** '''Only if it is imperative to make the diagnosis of reflux in children with a history of recurrent pyelonephritis and repeatedly negative voiding studies in the intercurrent periods should cystography during UTI be considered.'''
**Parameters that effect direct imaging of VUR (3)''':'''
***** Some UVJs maintain only borderline antireflux mechanisms, which are competent in a sterile milieu but become incompetent from edema and inflammation associated with mucosal inflammation during cystitis. Such patients may have VCUG studies negative for reflux in the absence of infection but suffer from repeated pyelonephritic episodes. Cystograms in such patients may demonstrate reflux if obtained during clinically active infection, whereas cystogram obtained in the presence of positive urine cultures alone may not.
**# Bladder contraction during voiding
*** '''VCUG Technique'''
**# Fluid volume instilled into the bladder
**** Bladder contrast is instilled by gravity after urethral catheterization. Bladder capacity is recorded when contrast influx ceases. Static images record bladder contour, presence of diverticula or ureteroceles, grade of reflux, configuration and blunting of calyces, and intrarenal reflux. Passive or active reflux is demonstrated dynamically during fluoroscopy while filling and voiding, respectively. In addition, bladder neck anatomy, funneling or dilation, and urethral patency are parameters derived from the VCUG.
**# Presence of infection and therefore inflammation of the UVJ mucosa.
**** '''Delayed or postvoid films are crucial in documenting clearance of contrast from the upper tracts because retained contrast, particularly with dilated pelvicalyceal systems, could signify the presence of a concomitant UPJ obstruction (UPJO)'''
*** '''Even during voiding, reflux may not be demonstrated on a single filling-voiding cycle'''. Several studies have demonstrated a roughly 12-20% '''greater detection rate for VUR if a cyclic study is performed'''
** '''Diagnostic Controversies: Challenging the Assessment of VUR'''
** '''Passive reflux (VUR during filling of the bladder) is generally considered a poor prognostic sign for reflux resolution and suggests the presence of a fixed decompensation of the UVJ.'''
*** '''Uroflowmetry'''
*** Filling assumes far lower intravesical pressure than that of voiding
**** A valuable tool in the workup of a patient with vesicoureteral reflux
*** '''Passive reflux is common finding in patients with acquired or neurogenic voiding dysfunction'''
**** A minimal survey of bladder emptying characteristics can be obtained
* '''Cystogram during active infection'''
***** Lack of smoothness of the flow-velocity curve suggest incomplete relaxation of the bladder outlet during voiding.
** '''The general consensus has been to delay the voiding study for at least a week or longer to allow for adequate recovery from the acute infection episode.'''
****** This implies the existence or development of relatively higher pressures during voiding, which could delay the natural history of VUR resolution or even perpetuate VUR.
*** Evoking reflux during an active cystitis, by definition, will transmit bacteria to the upper urinary tract and renal pelvis and risks iatrogenic pyelonephritis.
***** Increased postvoid residual volume may be a risk factor for UTI.
** '''Only if it is imperative to make the diagnosis of reflux in children with a history of recurrent pyelonephritis and repeatedly negative voiding studies in the intercurrent periods should cystography during UTI be considered.'''
****** In the setting of passive VUR, carrying infected postvoid residual urine also can lead to ascending infection and pyelonephritis.
*** Some UVJs maintain only borderline antireflux mechanisms, which are competent in a sterile milieu but become incompetent from edema and inflammation associated with mucosal inflammation during cystitis. Such patients may have VCUG studies negative for reflux in the absence of infection but suffer from repeated pyelonephritic episodes. Cystograms in such patients may demonstrate reflux if obtained during clinically active infection, whereas cystogram obtained in the presence of positive urine cultures alone may not.
*** '''Top-Down Approach'''
* '''Diagnostic Controversies: Challenging the Assessment of VUR'''
**** '''Only a dimercaptosuccinic acid (DMSA) renal scan is obtained after a febrile UTI, with cystography reserved only for patients with abnormal scintigraphy findings.'''
** '''Uroflowmetry'''
***** '''Children with a normal DMSA scan undergo no further evaluation unless they develop recurrent UTI, in which case a VCUG should be obtained'''.
*** A valuable tool in the workup of a patient with vesicoureteral reflux
***** Photopenic areas may result from postinfection renal scarring and some renal dysplasia.
*** A minimal survey of bladder emptying characteristics can be obtained
***** Vesicoureteral reflux, particularly reflux of higher grades, may result in renal dysplasia, which often appears scintigraphically identical to postinfection pyelonephritic scars.
**** Lack of smoothness of the flow-velocity curve suggest incomplete relaxation of the bladder outlet during voiding.
***** During an episode of active pyelonephritis, the renal scan may show an area of photopenia that later, if it persists, represents renal scarring secondary to the infection.
***** This implies the existence or development of relatively higher pressures during voiding, which could delay the natural history of VUR resolution or even perpetuate VUR.
***** Neither renal scan nor ultrasonography can differentiate accurately between renal dysplasia and renal scarring
**** Increased postvoid residual volume may be a risk factor for UTI.
**** '''A critical assumption with this approach is that VUR in the absence of scintigraphic renal abnormality is unlikely to cause future renal damage'''
***** In the setting of passive VUR, carrying infected postvoid residual urine also can lead to ascending infection and pyelonephritis.
**** '''The top-down approach performs poorly at detecting high-grade VUR''' with a sensitivity and specificity of only 79% and 53%, respectively
** '''Top-Down Approach'''
** '''American Academy of Pediatrics Guidelines for Febrile UTI Diagnosis and Management in Young Children'''
*** '''Only a dimercaptosuccinic acid (DMSA) renal scan is obtained after a febrile UTI, with cystography reserved only for patients with abnormal scintigraphy findings.'''
*** '''VCUG should be obtained after second febrile UTI'''
**** '''Children with a normal DMSA scan undergo no further evaluation unless they develop recurrent UTI, in which case a VCUG should be obtained'''.
**** Previous recommendation was after the first febrile UTI
**** Photopenic areas may result from postinfection renal scarring and some renal dysplasia.
**** '''VCUG should be obtained after first febrile UTI if''':
**** Vesicoureteral reflux, particularly reflux of higher grades, may result in renal dysplasia, which often appears scintigraphically identical to postinfection pyelonephritic scars.
****# US shows hydronephrosis, possible renal scarring or dysmorphism
**** During an episode of active pyelonephritis, the renal scan may show an area of photopenia that later, if it persists, represents renal scarring secondary to the infection.
****# Other findings that suggest high-grade VUR
**** Neither renal scan nor ultrasonography can differentiate accurately between renal dysplasia and renal scarring
****# Obstructive uropathy are present
*** '''A critical assumption with this approach is that VUR in the absence of scintigraphic renal abnormality is unlikely to cause future renal damage'''
****# Any complex or clinically atypical scenario
*** '''The top-down approach performs poorly at detecting high-grade VUR''' with a sensitivity and specificity of only 79% and 53%, respectively
** '''Cystoscopy'''
* '''American Academy of Pediatrics Guidelines for Febrile UTI Diagnosis and Management in Young Children'''
*** '''Routine cystoscopy is contraindicated in reflux management'''
** '''VCUG should be obtained after second febrile UTI'''
**** The assessment of appearance and configuration of the ureteric orifices and intramural tunnel length provide little correlation with either the diagnosis or grade of reflux
*** Previous recommendation was after the first febrile UTI
**** '''The cystoscopic position of the refluxing ureteric orifice is permanent lateral displacement'''
*** '''VCUG should be obtained after first febrile UTI if''':
* '''Assessment of the Upper Urinary Tract'''
***# US shows hydronephrosis, possible renal scarring or dysmorphism
** '''Rationale for Serial Assessment of Upper Tracts'''
***# Other findings that suggest high-grade VUR
*** '''Pyelonephritis propagated by VUR causes:'''
***# Obstructive uropathy are present
***# '''Renal scarring'''
***# Any complex or clinically atypical scenario
***# '''Impedes attainment of full renal growth potential'''
 
***# '''Increases risk for renovascular hypertension'''
==== Upper Urinary Tract ====
*** '''Most parenchymal abnormalities are detected after the first episode of pyelonephritis'''
* '''Rationale for Serial Assessment of Upper Tracts'''
*** A fundamental goal in serial upper tract imaging with VUR is to ascertain whether abnormalities are due to ongoing or resolved reflux and differentiate them from intrinsic developmental disturbances, medical renal disease, or antegrade flow resistance.
** '''Pyelonephritis propagated by VUR causes:'''
*** Intensity of upper tract studies should be proportional to the propensity for renal damage
**# '''Renal scarring'''
*** The challenge in imaging is to differentiate congenital reflux–associated renal dysmorphism from scarring acquired after infection
**# '''Impedes attainment of full renal growth potential'''
**** VUR, particularly of higher grades, may result in renal maldevelopment that often appears scintigraphically or sonographically identical to postinfection pyelonephritic scars
**# '''Increases risk for renovascular hypertension'''
** '''Renal US'''
** '''Most parenchymal abnormalities are detected after the first episode of pyelonephritis'''
*** The mainstay of renal imaging in VUR management
** A fundamental goal in serial upper tract imaging with VUR is to ascertain whether abnormalities are due to ongoing or resolved reflux and differentiate them from intrinsic developmental disturbances, medical renal disease, or antegrade flow resistance.
*** '''The appearance of the kidneys on ultrasound does not correlate with the absence or presence of reflux, or with its grade'''
** Intensity of upper tract studies should be proportional to the propensity for renal damage
*** '''Renal resistive index measurements are significantly increased in higher grades of reflux'''
** The challenge in imaging is to differentiate congenital reflux–associated renal dysmorphism from scarring acquired after infection
** '''Renal Scintigraphy'''
*** VUR, particularly of higher grades, may result in renal maldevelopment that often appears scintigraphically or sonographically identical to postinfection pyelonephritic scars
*** '''The gold standard for imaging functioning renal parenchyma is scintigraphy using 99mTc-labeled DMSA.'''
* '''Renal US'''
**** The radiotracer is taken up only by functioning proximal tubular tissue mass, where it binds for several hours.
** The mainstay of renal imaging in VUR management
***** Because pyelonephritis impairs tubular uptake of radiotracer, these areas will fail to radioemit photons and appear as unexposed or underexposed regions in the resultant renal cortical images
** '''The appearance of the kidneys on ultrasound does not correlate with the absence or presence of reflux, or with its grade'''
***** DMSA scanning provides 98% sensitivity and 92% specificity for scar detection
** '''Renal resistive index measurements are significantly increased in higher grades of reflux'''
**** The uptake of DMSA provides a good proportional representation of glomerular filtration
* '''Renal Scintigraphy'''
**** No consensus exists on the precise use of DMSA scanning in reflux management.
** '''The gold standard for imaging functioning renal parenchyma is scintigraphy using 99mTc-labeled DMSA.'''
** DMSA and ultrasonography are often used complementarily, particularly when knowledge of relative renal function is desired since all DMSA defects are not necessarily scars.
*** The radiotracer is taken up only by functioning proximal tubular tissue mass, where it binds for several hours.
**** Because pyelonephritis impairs tubular uptake of radiotracer, these areas will fail to radioemit photons and appear as unexposed or underexposed regions in the resultant renal cortical images
**** DMSA scanning provides 98% sensitivity and 92% specificity for scar detection
*** The uptake of DMSA provides a good proportional representation of glomerular filtration
*** No consensus exists on the precise use of DMSA scanning in reflux management.
* DMSA and ultrasonography are often used complementarily, particularly when knowledge of relative renal function is desired since all DMSA defects are not necessarily scars.
 
=== Other ===
 
==== Cystoscopy ====
* '''Routine cystoscopy is contraindicated in reflux management'''
** The assessment of appearance and configuration of the ureteric orifices and intramural tunnel length provide little correlation with either the diagnosis or grade of reflux
** '''The cystoscopic position of the refluxing ureteric orifice is permanent lateral displacement'''


== Complications of Acquired Scarring ==
== Complications of Acquired Scarring ==
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== Natural History ==
== Natural History ==


* '''At birth, the probability of spontaneous resolution of primary VUR is inversely proportional to the initial grade'''
* '''<span style="color:#ff0000">At birth, the probability of spontaneous resolution of primary VUR is inversely proportional to the initial grade'''
** '''Most cases of low-grade reflux (grade 1 and 2) will resolve'''
** '''<span style="color:#ff0000">Most cases of low-grade reflux (grade 1 and 2) will resolve'''
** '''Grade 3 reflux will resolve in ≈50% of cases'''
** '''<span style="color:#ff0000">Grade 3 reflux will resolve in ≈50% of cases'''
** '''Very few cases of higher-grade reflux (grades 4 and 5, and bilateral grade 3) will resolve spontaneously'''
** '''<span style="color:#ff0000">Very few cases of higher-grade reflux (grades 4 and 5, and bilateral grade 3) will resolve spontaneously'''
*** Attempting to discriminate true differences in resolution rates for grades 3 and higher reflux may not be particularly clinically relevant.
*** Attempting to discriminate true differences in resolution rates for grades 3 and higher reflux may not be particularly clinically relevant.
* '''At a later age, spontaneous resolution will depend on:'''
* '''At a later age, spontaneous resolution will depend on:'''
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