Overview
Definition:
Post-Void Residual (PVR) volume refers to the amount of urine remaining in the bladder after a voiding attempt
Bladder ultrasound is a non-invasive imaging technique used to measure this volume, particularly relevant in evaluating toilet-training difficulties and lower urinary tract dysfunction in children.
Epidemiology:
Toilet training issues, including daytime wetting (diurnal enuresis) and PVR, affect a significant proportion of children, with prevalence varying by age and definition
Chronic PVR can be associated with recurrent urinary tract infections (UTIs) and kidney damage
Studies show PVR is elevated in a subset of children with functional voiding disorders.
Clinical Significance:
Accurate measurement of PVR via ultrasound is crucial for diagnosing and managing voiding dysfunction
Persistent high PVR can lead to urinary stasis, increasing UTI risk, and may indicate underlying neurological or anatomical abnormalities
It guides appropriate therapeutic interventions for toilet-training challenges.
Clinical Presentation
Symptoms:
Difficulty initiating voiding
Straining to void
Infrequent urination
Urgency
Daytime wetting (diurnal enuresis)
Nocturnal enuresis
Recurrent urinary tract infections
Abdominal discomfort or pain
Constipation often co-exists.
Signs:
Palpable distended bladder in severe cases
Poor stream of urine
Overflow incontinence
Abdominal tenderness
Digital rectal examination may reveal fecal impaction.
Diagnostic Criteria:
While no strict diagnostic criteria exist solely for PVR measurement in toilet-training issues, elevated PVR is often defined as >10% of bladder capacity for age, or absolute values exceeding age-appropriate norms (e.g., >20 ml in young children, >50 ml in older children), especially when symptomatic
Chronic PVR is a key finding in dysfunctional voiding.
Diagnostic Approach
History Taking:
Detailed history of voiding habits, including frequency, urgency, stream, straining, daytime/nighttime wetting episodes
History of UTIs
Bowel habits, particularly constipation
Family history of voiding dysfunction or enuresis
Fluid intake and output
Previous treatments and their efficacy
Red flags include fever, flank pain, dysuria, hematuria, or failure to thrive.
Physical Examination:
General physical examination
Abdominal examination for distension, masses, or tenderness
Genitourinary examination to rule out structural anomalies
Digital rectal examination to assess for fecal impaction or rectal tone
Assess for signs of neurological deficits.
Investigations:
Bladder ultrasound for PVR: Non-invasive, readily available
Measures urine volume post-void
Post-Void Residual (PVR) calculation: (Bladder volume post-void) x 100 / (Bladder volume pre-void + Bladder volume post-void) is not standard
typically, the absolute volume post-void is the primary metric
Urine dipstick and microscopy: To detect infection or hematuria
Urine culture and sensitivity: If infection is suspected
Renal and bladder ultrasound: To assess bladder wall thickness, hydronephrosis, and renal parenchyma
Uroflowmetry and post-void residual ultrasound: If urodynamics are considered
Plain abdominal X-ray: To assess for fecal impaction.
Differential Diagnosis:
Functional voiding disorders (dysfunctional voiding, detrusor overactivity)
Urinary tract infection (UTI)
Congenital anatomical abnormalities (e.g., posterior urethral valves, ureteroceles)
Neurological conditions (e.g., spina bifida, spinal cord anomalies)
Constipation with encopresis
Diabetes insipidus (less common cause of polyuria leading to perceived voiding issues)
Bladder outlet obstruction.
Management
Initial Management:
Accurate PVR measurement to confirm the presence and degree of retention
Address constipation if present, as it is a major contributor to voiding dysfunction
Educate parents and child on proper toileting hygiene and posture
Scheduled voiding with timed voiding intervals.
Medical Management:
Pharmacological management is often adjunctive
Alpha-blockers (e.g., Alfuzosin, Tamsulosin) may be considered in older children with dysfunctional voiding and high PVR to relax bladder neck and urethral smooth muscle
Anticholinergics (e.g., Oxybutynin, Tolterodine) may be used for detrusor overactivity if present, but caution is advised as they can worsen retention
Prompt treatment of UTIs with appropriate antibiotics based on culture and sensitivity is essential.
Surgical Management:
Surgical intervention is rarely required for PVR due to toilet-training issues unless there is a clear anatomical obstruction
Procedures like bladder neck reconstruction or urethral dilatations are reserved for specific structural abnormalities and persistent, severe voiding dysfunction unresponsive to conservative management.
Supportive Care:
Regular follow-up with the pediatrician or pediatric urologist/gastroenterologist
Reinforce positive toileting behaviors
Encourage adequate fluid intake distributed throughout the day
Monitor for UTIs and adjust management as needed
Bowel regimen for managing constipation.
Complications
Early Complications:
Recurrent urinary tract infections (UTIs)
Urinary retention leading to acute discomfort or overflow incontinence
Worsening of constipation.
Late Complications:
Vesicoureteral reflux (VUR) secondary to high bladder pressures
Bladder dysfunction leading to irreversible bladder changes (e.g., trabeculation, detrusor hypertrophy)
Renal damage (e.g., chronic pyelonephritis, hydronephrosis, renal scarring) if untreated
Social and emotional impact on the child due to persistent wetting and perceived failure.
Prevention Strategies:
Early identification and aggressive management of constipation
Prompt diagnosis and treatment of UTIs
Regular monitoring of PVR in children with persistent voiding dysfunction
Patient and family education on bladder and bowel health
Biofeedback and behavioral therapy can be beneficial.
Prognosis
Factors Affecting Prognosis:
Underlying etiology (functional vs
anatomical vs
neurological)
Severity of PVR and associated symptoms
Presence and severity of UTIs and renal involvement
Compliance with treatment
Co-existing constipation
Age of presentation.
Outcomes:
With timely and appropriate management, most children with functional voiding disorders and elevated PVR can achieve significant improvement or resolution of symptoms, leading to successful toilet training and a reduced risk of long-term complications
Outcomes are generally good for functional causes, but may be more guarded for significant neurological or anatomical deficits.
Follow Up:
Follow-up frequency depends on the severity of the condition and response to treatment
Initially, close follow-up with serial PVR measurements and urine tests may be required
Long-term follow-up is recommended for children with significant bladder or renal abnormalities to monitor for complications
Gradual weaning off medication and therapy as symptoms resolve.
Key Points
Exam Focus:
Bladder ultrasound for PVR is a critical investigation in pediatric voiding dysfunction
Remember that constipation is a common co-factor and must be managed
Differentiate functional causes from organic causes
Understand the significance of elevated PVR in recurrent UTIs.
Clinical Pearls:
Always assess bowel habits alongside voiding issues in children
A simple bladder ultrasound is often all that is needed to guide initial management
Reassure parents that toilet-training issues are common and often manageable
Consider antegrade filling studies if recurrent UTIs persist despite optimal management.
Common Mistakes:
Over-reliance on medication without addressing constipation
Failing to measure PVR when suspected, leading to delayed diagnosis
Misinterpreting PVR values without considering bladder capacity or age
Aggressively treating with anticholinergics without assessing for retention, potentially worsening PVR.