Patient Education and Consent
Patient counseling remains a challenge, in that diagnostic modalities lack prognostic accuracy and the effectiveness of in-utero intervention remains uncertain.
In Ruano's review of vesicoamniotic shunt placement, 45% had associated complications, most of which were mechanical issues related to the shunt. [25] As vesicoamniotic shunts relieve fetal bladder pressure, detrusor muscle weakness may ensue, leading to postnatal incontinence; thus, the risks and benefits must be carefully weighed prior to intervention. Parents must also be aware that vesicoamniotic shunt placement is a temporizing measure and that further intervention will likely be required.
Equipment
The vesicoamniotic shunt includes a stylet with an introducer, a push rod, and a double pigtail shunt (Rocket of London, London, UK).
Patient Preparation
Anesthesia
Both fetoscopic vesicoamniotic shunt placement and fetal cystoscopy are amenable to local anesthesia with minimal maternal intravenous sedation. For cases predicted to be challenging, an epidural may serve as an alternative.
Positioning
The patient is typically placed in the supine position on the operating room table. Ideally, the fetus will lie in the back-down vertex position, providing a safe window to access the fetal bladder. Depending on the fetal lie and placental location, external manipulation may be required. If external manipulation proves unsuccessful, patient ambulation and case delay may be necessary to reposition the fetus.
Monitoring & Follow-up
Fetal intervention increases the risk of preterm premature rupture of the membrane and preterm delivery; accordingly, patients must be monitored closely after fetal intervention, and any changes in fetal movement or maternal complications should prompt immediate evaluation.
Postnatal follow-up often requires a pediatric nephrology and urology consult. If an obstruction is present at birth, stent decompression can serve as a temporizing measure until definitive reconstruction is performed. Unfortunately, most of the damage has already been done by this point, and frequently, monitoring of serum and urine electrolytes is the most that can be offered.
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Classic keyhole sign seen in patients with posterior urethra valves
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Treatment algorithm for fetal lower urinary tract obstructions. From The Unborn Patient: The Art and Science of Fetal Therapy (p. 272), by Johnson MP, Philadelphia: W.B. Saunders Company. 2001. Adapted with permission.
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Fetal vesico-amniotic shunt illustration.
