Novel scoring system for determining fetal candidacy for prenatal intervention for severe congenital lower urinary tract obstruction

Fetal Lower Urinary Tract Obstruction: Current Diagnostic and Therapeutic Strategies and Future Directions

BACKGROUND

Fetal lower urinary tract obstruction (LUTO) is a rare congenital anomaly in which the bladder cannot empty properly. The clinical presentation is variable. On the severe end of the spectrum, the amniotic fluid index can be sufficiently low, resulting in fetal lung development that is incompatible with life outside the womb. The pressure in the urinary tract system can also result in severe damage to the kidney, resulting in renal failure in utero or in the first couple years of life. Therefore, much work has been done to determine which fetuses need intervention in utero to allow for survival outside of the womb and avoidance of end-stage renal disease. Multiple therapies have been developed to relieve the obstruction in utero with the mainstay being vesicoamniotic shunting and posterior urethral valve ablation.

SUMMARY

While much has been investigated to determine which fetuses would benefit from fetal intervention, the current indications are not without their flaws. This review describes the current indications and their shortcomings, as well as new experimental methods of determining need for intervention. Additionally, this review describes the milestone animal studies that established the challenges of current fetal interventions and the utility of an experimental valved shunt in sheep over the last 20 years.

KEY MESSAGES

Our understanding of LUTO and which fetuses benefit from in utero intervention has grown over the last 20 years. However, traditional markers have proven to be less predictive than previously thought, opening the door to exciting new advances. Vesicoamniotic shunting, while lifesaving, does not preserve bladder function and frequently dislodges. Animal studies over the last 20 years have established the utility of a valved shunt to maintain bladder function. Current advances are working to create such a shunt that can be percutaneously deployed and have greater adherence to the bladder wall to avoid dislodgement.

Fetal bladder morphology as a predictor of outcome in fetal lower urinary tract obstruction

OBJECTIVE

We evaluate survival of fetuses with severe Lower Urinary Tract Obstruction (LUTO) based on bladder morphology. We hypothesize that fetuses with a "floppy" appearing bladder on initial prenatal ultrasound will have worse infant outcomes than fetuses with full/rounded bladders.

METHOD

We retrospectively reviewed all cases of LUTO evaluated in our fetal center between January 2013 and December 2021. Ultrasonographic assessment, renal biochemistry, and bladder refilling contributed to a "favorable" or "unfavorable" evaluation. Bladder morphology on initial ultrasound was classified as "floppy" or "full/rounded." Vesicoamniotic shunting was offered for favorably evaluated fetuses. Baseline demographics, ultrasound parameters, prenatal evaluations of fetal renal function, and infant outcomes were collected. Fetuses diagnosed with severe LUTO were included in analysis using descriptive statistics. The primary outcome measured was survival at 6 months of life.

RESULTS

104 LUTO patients were evaluated; 24 were included in analysis. Infant survival rate at 6 months was 60% for rounded bladders and 0% for floppy bladders (p = 0.003). Bladder refill adequacy was lower in fetuses with floppy bladders compared with rounded bladders (p value < 0.00001).

CONCLUSION

We propose that bladder morphology in fetuses with severe LUTO may be a prognostication factor for predicting infant outcomes and provides a valuable, noninvasive assessment tool.

Predictors of advanced chronic kidney disease in infancy after definitive vesicoamniotic shunting for congenital lower urinary tract obstruction

BACKGROUND

Severe congenital lower urinary tract obstruction (cLUTO) is associated with poor postnatal outcomes, including chronic and end stage kidney disease, and high mortality. Studies of the impact of fetal intervention through vesicoamniotic shunting are marred by a device malfunction rate of up to 60%. In this study, we delineate the postnatal course and infant kidney function following definitive urinary diversion in utero.

MATERIALS AND METHODS

This is a retrospective, single-center cohort study of 16 male infants who survived the fetal intervention to birth, from 2010 to 2014 at a single center. All had patent shunts in place at birth. Perinatal and biochemical characteristics were collected with patients followed for one year, or until demise, with serial measures of serum creatinine (SCr) and serum cystatin C (CysC).

RESULTS

Of the 16 males, 81% were non-white (38% black, 43% Hispanic). Shunts were placed at a median of 20 weeks (IQR 19,23) gestation, with median fetal bladder volume of 39 cm³ (IQR 9.9,65). All neonates were born preterm [median 34 weeks (IQR 31,35)] and the majority with low birth weight [median 2340 grams (1,895, 2,600)]. 63% required positive pressure ventilation. Advanced chronic kidney disease stage 4-5 at 1 year of age was predicted by neonatal characteristics: peak SCr ≥2 mg/dl, time to peak SCr > 6 days, discharge SCr ≥1.0 mg/dl, CysC ≥2.5 mg/l, urine protein:creatinine ≥4.8 mg/mg, urine microalbumin:creatinine ≥2.2 mg/mg. In infancy, a nadir SCr ≥0.5 mg/dl occurring before 160 days (5.3 months) of age was also predictive of advanced chronic kidney disease stage 4-5 at 1 year. Three patients died in the neonatal period, with 1 receiving kidney replacement therapy (KRT). Three additional patients required KRT before 12 months of age.

CONCLUSIONS

Even with definitive vesicoamniotic shunting for cLUTO, postnatal morbidity and mortality remain high, emphasizing the role of renal dysplasia, in spite of urinary diversion, in postnatal kidney dysfunction. Neonatal and infant biochemical parameters exhibit distinct trends that offer families and physicians a better understanding of the prognosis of childhood kidney function.