Neurogenic and Dysfunctional Disorders
Impaired coordination between bladder wall contraction and external sphincter relaxation often occurs in the setting of spinal dysraphism (e.g., myelomeningocele). To confirm or exclude a spinal etiology, a spinal ultrasound or MRI is ordered as a first step. If there are no anatomical spinal cord defects, the term "non-neurogenic neurogenic bladder" is used. Such dysfunctional disorders are best diagnosed using modified voiding cystourethrography (VCUG) or videourodynamics.
The primary goal of treatment is to ensure urinary continence and protect the upper urinary tract. If the bladder empties poorly, vesicoureteral reflux (VUR) develops, complicated by infections. Management includes intermittent catheterization, pharmacotherapy, and, in severe cases, surgical bladder augmentation. For non-neurogenic forms, bladder training with biofeedback (biofeedback) therapy is effective. Ultrasound and dynamic renal scintigraphy with 99mTc-MAG3 are used for monitoring.
Posterior Urethral Valves
Posterior urethral valves (PUV) are congenital abnormal mucosal folds between the urethral wall and the verumontanum. They are a frequent cause of bladder outlet obstruction in male infants.
The clinical presentation depends on the degree of obstruction:
- Severe obstruction manifests in the neonatal period. Urosepsis, renal failure, and pulmonary hypoplasia (due to oligohydramnios) are characteristic. Antenatal ultrasound may reveal urinary ascites, an enlarged bladder, and renal dilation.
- Less severe forms present in childhood with recurrent urinary tract infections.
Treatment consists of early cystoscopic valve ablation. Temporary drainage (nephrostomy) may be required to preserve renal function. It is important to remember that even with optimal surgical treatment, concomitant renal dysplasia may necessitate kidney transplantation in the future.
Diagnostic Imaging of Urethral Pathologies
An optimal view of the bladder neck and posterior urethra is provided by VCUG or retrograde urethrography in an oblique lateral projection.
- Ultrasound. Detects upper tract dilation, bladder wall thickening, renal dysplasia, and urinomas. Urinomas occur as a protective mechanism (pop off) due to caliceal rupture caused by high pressure. Important: the examination is performed only when the child is adequately hydrated, otherwise the degree of dilation will be underestimated.
- VCUG. Demonstrates bladder wall trabeculation, diverticula, and reflux. A specific radiological sign of posterior urethral valves is a sharp caliber transition of the urethra during micturition.
Strictures and Rare Anomalies of the Anterior Urethra
Urethral strictures can be congenital or acquired. In boys, congenital strictures are localized in the bulbous urethra in 75% of cases, whereas in girls, they occur at the meatus. Acquired forms usually develop after perineal trauma (affecting the bulbous urethra) or from pelvic fractures and catheter trauma (affecting the membranous urethra). Treatment typically involves internal urethrotomy.
Rare anomalies include:
- Anterior urethral valves. Occur 10 times less frequently than posterior valves. On VCUG during micturition, they present as a typical ballooning (ballooning) dilation of the urethra with penile curvature.
- Syringocele. A cystic dilation of the bulbourethral (Cowper's) gland that can cause complete urethral obstruction in newborns or hematuria in older children.
- Urethral duplication. Manifests as a double urinary stream; often, one of the urethras ends in hypospadias.
Uterine, Vaginal, and Renal Anomalies
The urinary and reproductive systems develop from common embryological precursors. Disruption of Müllerian duct formation leads to lateral or vertical fusion anomalies (e.g., Mayer-Rokitansky-Küster-Hauser syndrome). In the neonatal period, such malformations may present as a pelvic mass, whereas in puberty, they cause primary amenorrhea and hematometrocolpos due to menstrual outflow obstruction.
Important rule: all girls with genital anomalies must undergo a thorough ultrasound of the kidneys and adrenal glands. In 50% of cases, these pathologies are accompanied by renal agenesis, dysplasia, or ectopia, and in 12% by vertebral segmentation anomalies.
Briefly: answers to topical questions
What are the absolute and relative contraindications to voiding cystourethrography (VCUG)?
The sources explicitly state only one contraindication to VCUG: acute sepsis. A classification of contraindications into absolute and relative is not provided. VCUG is used to detect dysfunctional voiding, vesicoureteral reflux, bladder wall trabeculation, and diverticula, and to evaluate the urethra; in posterior urethral valves, it may reveal a sharp caliber transition of the posterior urethra during micturition.
What anatomical types of posterior urethral valves are distinguished according to Young's classification?
Three types of posterior urethral valves are distinguished, although Young's classification is not mentioned in the text. The following variants are described:
- Type I — a slit-like opening located between two folds distal to the verumontanum (verumontanum).
- Type III — a valve with an eccentric pinpoint opening. During micturition, this valve balloons forward, producing the characteristic "wind in the sail" (wind in the sail) sign on voiding cystourethrography. This type is associated with renal dysplasia.
Description of the second type is absent in the sources.
Which pharmacological drug classes are used for the medical management of neurogenic bladder?
The following pharmacological drug classes are used for the medical management of neurogenic bladder:
- Anticholinergics (M-anticholinergics) — oxybutynin, tolterodine, trospium, solifenacin.
- Selective $\beta$-3 adrenergic agonists — mirabegron.
- Antidepressants with anticholinergic activity — imipramine, amitriptyline.
- Cholinergic agents — neostigmine, aceclidine, carbachol (stimulate smooth muscle).
- $\alpha_1$-adrenergic blockers — prazosin, doxazosin (relax the internal sphincter).
- Centrally acting muscle relaxants — baclofen, tizanidine (used for increased external sphincter tone).
Intravesical injections of botulinum toxin type A are used as second-line therapy. Desmopressin is used for the symptomatic treatment of nocturia.
To remember the radiological appearance of type III posterior urethral valves on VCUG, the "wind in the sail" sign is used — this is how the eccentric valve looks when ballooning forward during micturition.
Class and exam questions
Why is it essential to take an image without a urethral catheter during a voiding cystourethrography (VCUG)?
A micturition image without the catheter ("catheter out" view) is necessary to avoid missing the pathology. A retained catheter can tightly press a small valve leaflet against the urethral wall, rendering it invisible to the radiologist.
Is a follow-up VCUG sufficient after surgical ablation of posterior urethral valves?
No, performing VCUG alone is not sufficient. Cystoscopy is a mandatory control method, as residual valve leaflets are easily missed on radiographs.
How are anal and urethral anomalies related?
In anorectal malformations (anal atresia), a rectourethral fistula frequently forms. High-pressure loopogram through a distal colostomy is used for its diagnosis.
What else to study on this topic
- Cryptorchidism and Embryogenesis of the Undescended Testis
- Radioisotope Imaging (99mTc-DMSA) for Assessing Split Renal Function
- Embryological Classification of Uterine and Vaginal Malformations
- Radiological Signs of Congenital Scaphoid Megaurethra
- Technique of Videourodynamics in Dysfunctional Voiding
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