Predictive accuracy of prenatal ultrasound findings for lower urinary tract obstruction: A systematic review and Bayesian meta‐analysis

Abstract

Background Lower urinary tract obstruction (LUTO) is a rare but critical fetal diagnosis. Different ultrasound markers have been reported with varying sensitivity and specificity. Aims The objective of this systematic review and meta‐analysis was to identify the diagnostic accuracy of ultrasound markers for LUTO. Materials and Methods We performed a systematic literature review of studies reporting on fetuses with hydronephrosis or a prenatally suspected and/or postnatally confirmed diagnosis of LUTO. Bayesian bivariate random effects meta‐analytic models were fitted, and we calculated posterior means and 95% credible intervals for the pooled diagnostic odds ratio (DOR). Results A total of 36,189 studies were identified; 636 studies were available for full text review and a total of 42 studies were included in the Bayesian meta‐analysis. Among the ultrasound signs assessed, megacystis (DOR 49.15, [15.28, 177.44]), bilateral hydroureteronephrosis (DOR 41.33, [13.36,164.83]), bladder thickening (DOR 13.73, [1.23, 115.20]), bilateral hydronephrosis (DOR 8.36 [3.17, 21.91]), male sex (DOR 8.08 [3.05, 22.82]), oligo‐ or anhydramnios (DOR 7.75 [4.23, 14.46]), and urinoma (DOR 7.47 [1.14, 33.18]) were found to be predictive of LUTO (Table 1). The predictive sensitivities and specificities however are low and wide study heterogeneity existed. Discussion Classically, LUTO is suspected in the presence of prenatally detected megacystis with a dilated posterior urethra (i.e., the keyhole sign), and bilateral hydroureteronephrosis. However, keyhole sign has been found to have modest diagnostic performance in predicting the presence of LUTO in the literature which we confirmed in our analysis. The surprisingly low specificity may be influenced by several factors, including the degree of obstruction, and the diligence of the sonographer at searching for and documenting it during the scan. As a result, providers should consider this when establishing the differential for a fetus with hydronephrosis as the presence or absence of keyhole sign does not reliably rule in or rule out LUTO. Conclusions Megacystis, bilateral hydroureteronephrosis and bladder wall thickening are the most accurate predictors of LUTO. Given the significant consequences of a missed LUTO diagnosis, clinicians providing counselling for prenatal hydronephrosis should maintain a low threshold for considering LUTO as part of the differential diagnosis.

Trends in Management of Fetuses with Suspected Lower Urinary Tract Obstruction (LUTO): A High-Risk Fetal and Pediatric Center Experience in a Universal-Access-to-Care System

“…Thus, initiation of routine third trimester screening In the present study, LUTO affected mainly male fetuses and a suspected LUTO diagnosis led to constantly high termination rates of nearly 50% during the observation period, confirming previously published data. 3,8 Pregnancies opting for termination were diagnosed earlier, suggesting the presence of more severe ultrasound findings and a poorer potential prognosis. 13,20 Even in those that did not terminate the pregnancy, the mortality rate was as high as 36% which can be ranked to the lower end of the scale according to previously reported rates of 23% up to 75 to 90%.…”

“…Lower urinary tract obstruction (LUTO) affects 2 to 3 of every 10,000 fetuses 1 and is often associated with significant morbidity and mortality due to severe comorbidities such as pulmonary hypoplasia, renal insufficiency, and chronic kidney disease. 2 LUTO may be suspected prenatally in fetuses who exhibit the "classic" prenatal ultrasound features of megacystis, bilateral hydroureteronephrosis, oligohydramnios, and, while not entirely reliable, 3,4 the keyhole sign. 5 Due to the implications of a confirmed LUTO diagnosis on the child and family and the possibility of a poor prognosis, 6 40 to 53% of prospective parents may opt to terminate the pregnancy.…”

“…9 The severity of this condition and its implications stress the importance of obtaining an accurate and reliable prenatal diagnosis. Our previous work has explored the power of combinations of prenatal ultrasound features 3 to strengthen the prediction of LUTO. Despite advances in the accuracy of prenatal screening and technologies, detection rates are still suboptimal (33-62%).…”

Prenatal hydronephrosis: Bridging pre‐ and postnatal management

“…In a systematic review and Bayesian meta‐analysis by Keefe et al., prenatal ultrasound features of fetuses with HN were reviewed to determine which findings are most predictive of LUTO. Megacystis was the strongest predictor of a postnatal diagnosis of LUTO, while the classic “keyhole sign” was found to be a poor predictor 59 …”

“…In a systematic review and Bayesian meta- found to be a poor predictor. 59 Infants with a suspected LUTO should be delivered at a high-risk center due to the need for pediatric urology intervention shortly after birth, as well as neonatal intensive care support and early nephrology consult. Neonatal intensive care is needed for potential complications associated with oligohydramnios, such as lung hypoplasia, intrauterine growth restriction and feeding difficulties.…”