Educational content from recorded physician discussions — not medical advice. Always talk to your child's care team about your child's situation.
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Overview of Prenatal Diagnosis: Cincinnati Fetal Center
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Dr. Mark P. Johnson, research chair in fetal therapy, discusses an overview of prenatal diagnosis of fetal lower urinary tract obstruction. Dr. Johnson describes the most common causes of lower urinary tract obstructions, progressive oligoh
video · 40:34 · Nov 2018
Diagnosis & Workup
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Prenatal diagnosis of fetal lower urinary tract obstruction: Fetal...
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Dr. Mark P. Johnson, research chair in fetal therapy, discusses an overview of prenatal diagnosis of fetal lower urinary tract obstruction. Dr. Johnson describes the most common causes of lower urinary tract obstructions, progressive oligoh
video · 40:14 · Jan 2019
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Every statement below comes from the recorded discussions, with its speaker and moment.
Prenatal diagnosis of fetal lower urinary tract obstruction: Fetal...
The three major causes of LUTO are urethral atresia (complete obstruction with no communication from bladder neck through urethra), posterior urethral valves (flap of tissue in proximal urethra), and mid-urethral hypoplasia (significant tapering and narrowing that becomes progressive obstruction as pelvic anatomy matures).
clinicalMark0:32 ↗
Incomplete urethral obstruction leads to progressive oligohydramnios until anhydramnios, resulting in physical deformations (joint contractures, flattened ears, Potter phenotype), pulmonary hypoplasia from inability to expand chest, and severe hydronephrosis with progressive renal fibrocystic dysplasia and renal failure.
clinicalMark1:30 ↗
In sheep model, early mid-gestational reversal of urethral obstruction prevented progressive dysplastic changes to kidneys and preserved kidney function, giving rise to the concept of vesico-amniotic shunting.
clinicalMark2:58 ↗
Early shunting had highly variable outcomes and success rates.
clinicalMark4:32 ↗
A stepwise approach to identifying fetuses for shunt therapy includes: high-resolution ultrasound to assess anatomy and rule out associated anomalies (myelomeningocele, cardiac disease, genetic syndromes), karyotype confirmation to rule out chromosomal abnormalities, and renal function evaluation by serial bladder drainage.
guidelineMark4:50 ↗
Amnioinfusion is sometimes necessary to expand amniotic fluid space and restore fluid interface for better ultrasound resolution when initial evaluation is difficult.
clinicalMark5:19 ↗
Not an insignificant portion of LUTO cases have chromosomal abnormalities such as major trisomies or Klinefelter syndrome.
epidemiologicalMark5:36 ↗
It is important to confirm male fetus because female fetuses with large bladder-like structures are usually cloacal abnormalities that do not benefit from shunting due to different pathophysiology.
clinicalMark5:53 ↗
Renal function evaluation involves draining the bladder completely on several occasions and analyzing sodium, chloride, calcium, osmolarity, total proteins, and beta-2-microglobulin as reflections of proximal tubular injury and possible glomerular injury.
guidelineMark6:17 ↗
Increased kidney echogenicity is evidence of compression of renal parenchyma rather than a poor prognostic sign per se; following serial bladder drainages and allowing kidneys to drain, re-expansion of parenchyma occurs with more normal echogenicity.
clinicalMark8:10 ↗
Hydronephrosis pathophysiology: as collecting system (balloon) enlarges within kidney (sponge in fishbowl), it compresses parenchyma against serosa, impairing delicate vasculature and causing cell death, progressive fibrosis, and eventually cystic dysplasia.
clinicalMark8:49 ↗
Presence of cortical cysts indicates irreversibly damaged kidney not amenable to in utero therapy.
clinicalMark10:18 ↗
Patent urachus (tract from bladder dome to umbilical cord that reopens with high bladder pressure) is one etiology for LUTO with normal amniotic fluid volume.
clinicalMark12:41 ↗
Megacystis-microcolon-hypoperistalsis syndrome is a neurologic defect in bladder and ureteral muscles preventing contraction and emptying; these patients have massively distended bladder with normal amniotic fluid, thin bladder walls after drainage, and extremely poor survival (most do not survive more than a few years).
clinicalMark14:47 ↗
The first urine specimen from bladder tap is not predictive or reliable because it is exposed to degradation products and osmotic gradients that change electrolyte composition; serial taps (second at 2 days, third at 4 days) sample urine from ureters/intrarenal collecting system and then freshly produced urine, which have much higher predictive value.
clinicalMark19:05 ↗
Prognostic urinary electrolyte cutoff thresholds (sodium <100, chloride <90, osmolarity <210, calcium <8, beta-2-microglobulin <6, total protein <40 mg/dL) predict potential for survival with successful shunt placement; values above these indicate significant renal injury.
guidelineMark18:00 ↗
All prognostic urinary electrolyte cutoff thresholds were based on urine analyzed between 18 to 22 weeks gestation; they cannot be used before 18 weeks or after 22 weeks without adjustment for gestational age.
guidelineMark26:18 ↗
Bladder morphology after drainage can suggest etiology: symmetric thick-walled bladder with difficult keyhole suggests urethral atresia; elongated bladder with more proximal thickening suggests posterior urethral valves; snowman appearance (head-chest-body shape) suggests mid-urethral hypoplasia/prune belly variant with smooth muscle deficiency in bladder dome.
clinicalMark21:19 ↗
In mid-urethral hypoplasia cases, histology shows abnormal smooth muscle from proximal ureters to renal pelvis and severe abnormalities in bladder dome smooth muscle development.
clinicalMark25:13 ↗
The Paris group (Francis Muller, Humberto Nicolini) emphasized importance of using gestational-age-specific cutoffs for urinary electrolytes.
guideline25:53 ↗
Primary goal of fetal bladder shunting is to prevent pulmonary hypoplasia secondary to oligohydramnios; secondary goals are preservation of renal function and bladder function.
guideline28:41 ↗
Vesico-amniotic shunt is a double-tailed silastic pigtail catheter (Rocket or Harrison shunt) with coils in different directions; flat end outside baby's abdomen prevents baby from grabbing and pulling it out, other end inside bladder.
clinical29:08 ↗
Shunt placement is outpatient procedure with IV remifentanyl/propofol, local anesthetic, antibiotic, indomethacin, and possibly nifedipine; mother goes home couple hours later.
clinical29:43 ↗
Amnioinfusion before shunt placement is critical because without good fluid volume around fetus, external end of shunt cannot be deposited properly (most difficult part of procedure).
clinical30:06 ↗
Shunt should ideally be inserted inferior to bladder because higher placement risks holes in shunt ending up in peritoneal cavity as bladder deflates, causing fetal urinary ascites.
clinical31:05 ↗
Birmingham group meta-analysis showed in good-prognosis cases (by urinary electrolytes), there appeared to be some benefit to drainage; in poor-prognosis cases, drainage appeared to have even better result.
clinical31:37 ↗
PLUTO trial was only randomized trial of bladder shunting; babies randomized when physician was uncertain whether to shunt; karyotype and urinalysis were not mandatory, amniotic fluid volume not used as prognostic evaluator.
clinical32:27 ↗
PLUTO trial designed to collect 150 patients over 4 years but only 31 patients randomized; trial stopped early due to poor recruitment (only 20% of planned patients).
epidemiological33:41 ↗
PLUTO trial showed approximately 3-fold increase in survival in shunted fetuses compared to conservative management, but numbers very small and benefit unproven (confidence intervals crossed unity, results not significant).
clinical33:55 ↗
All 12 deaths in PLUTO trial were from pulmonary hypoplasia; improved survival inferred to be related to decrease in lung hypoplasia.
clinical34:36 ↗