Fetal hydronephrosis as a predictor of neonatal urologic outcomes

Deep learning of renal scans in children with antenatal hydronephrosis

INTRODUCTION

Antenatal hydronephrosis (ANH) is one of the most common anomalies identified on prenatal ultrasound, found in up to 4.5% of all pregnancies. Children with ANH are surveilled with repeated renal ultrasound and when there is high suspicion for a ureteropelvic junction obstruction on renal ultrasound, a mercaptuacetyltriglycerine (MAG3) Lasix renal scan is performed to evaluate for obstruction. However, the challenging interpretation of MAG3 renal scans places patients at risk of misdiagnosis.

OBJECTIVE

Our objective was to analyze MAG3 renal scans using machine learning to predict renal complications. We hypothesized that our deep learning model would extract features from MAG3 renal scans that can predict renal complications in children with ANH.

STUDY DESIGN

We performed a case-control study of MAG3 studies drawn from a population of children with ANH concerning for ureteropelvic junction obstruction evaluated at our institution from January 2009 until June of 2021. The outcome was renal complications that occur ≥6 months after an equivocal MAG-3 renal scan. We created two machine learning models: a deep learning model using the radiotracer concentration versus time data from the kidney of interest and a random forest model created using clinical data. The performance of the models was assessed using measures of diagnostic accuracy.

RESULTS

We identified 152 eligible patients with available images of which 62 were cases and 90 were controls. The deep learning model predicted future renal complications with an overall accuracy of 73% (95% confidence inteveral [CI] 68-76%) and an AUC of 0.78 (95% CI 0.7, 0.84). The random forest model had an accuracy of 62% (95% CI 60-66%) and an AUC of 0.67 (95% CI. 0 64, 0.72) DISCUSSION: Our deep learning model predicted patients at high risk of developing renal complications following an equivocal renal scan and discriminate those at low risk with moderately high accuracy (73%). The deep learning model outperformed the clinical model built from clinical features classically used by urologists for surgical decision making.

CONCLUSION

Our models have the potential to influence clinical decision making by providing supplemental analytical data from MAG3 scans that would not otherwise be available to urologists. Future multi-institutional retrospective and prospective trials are needed to validate our model.

Postnatal Outcomes of Fetuses with Prenatal Diagnosis of 6-9.9 mm Pyelectasis

Pyelectasis, also known as renal pelvic dilatation or hydronephrosis, is frequently found on fetal ultrasound. This study correlated prenatally-detected, moderate pyelectasis with postnatal outcomes. This retrospective, observational study was conducted at a tertiary medical center in Israel. The study group consisted of 54 fetuses with prenatal diagnosis of pyelectasis on ultrasound scan during the second trimester, defined as anteroposterior renal pelvic diameter (APRPD) 6-9.9 mm. Long-term postnatal outcomes and renal-related sequelae were obtained using medical records and telephone-based questionnaires. The control group included 98 cases with APRPD < 6 mm. Results indicate that fetal pyelectasis 6-9.9 mm was more frequent among males (68.5%) than females (51%, p = 0.034). We did not find significant correlations between 6-9.9 mm pyelectasis and other anomalies or chromosomal/genetic disorders. Pyelectasis resolved during the pregnancy in 15/54 (27.8%) cases. There was no change in 17/54 (31.5%) and 22/54 (40.7%) progressed to hydronephrosis Among the study group, 25/54 (46.3%) were diagnosed with neonatal hydronephrosis. There were more cases of renal reflux or renal obstruction in the study group compared to the control group 8/54 (14.8%) vs. 1/98 (1.0%), respectively; p = 0.002. In conclusion, most cases of 6-9.9 mm pyelectasis remained stable or resolved spontaneously during pregnancy. There was a higher rate of postnatal renal reflux and renal obstruction in this group; however, most did not require surgical intervention.

Postnatal management of children with antenatal hydronephrosis

Background

Postnatal management of infants with antenatal hydronephrosis (ANH) is still one of the most controversial issues. The majority of infants with ANH are asymptomatic with only few children who develop renal insufficiency. Thus, the biggest challenge for pediatric urologists is to distinguish children who will require further investigations and possible intervention prior to the development of symptoms, complications or renal damage in a cost effective manner without exposing them to the hazards of unnecessary investigations.

Main body

In this review article, literature on ANH were reviewed to present the current suggestions, recommendations, guidelines and their rational for postnatal management of ANH. It is agreed that a large portion of infants with ANH will improve; thus, the protocol of management is based mainly on observation and follow-up by ultrasound to detect either resolution, stabilization or worsening of hydronephrosis. The first 2 years of life are critical for this follow-up as the final picture is mostly reached during that period. Advanced imaging using voiding cystourethrography or renal scintigraphy are required for children at risk. Then, surgical intervention is selected only for a subgroup of these infants who showed worsening of hydronephrosis or renal function.

Conclusions

The protocol of management is based mainly on observation and follow-up by US to detect either resolution, stabilization or worsening of hydronephrosis. Postnatal evaluation should be performed for any neonate with a history ANH at any stage during pregnancy even if it was resolved during third trimester. Exclusion of UTI should be performed by urinalysis for all cases followed by urine culture if indicated. Serum creatinine should be performed especially in patients with bilateral ANH. US is the initial standard diagnostic imaging technique. Other imaging modalities like VCUG and nuclear renal scans may be required according to the results of the US evaluation. The most important items in decision making are the presence of bilateral or unilateral hydronephrosis, presence or absence of hydroureter, presence of lower urinary tract obstruction and degree of hydronephrosis on the initial postnatal US. Then an intervention is selected only for a subgroup of these patients who showed deterioration in renal function or degree of hydronephrosis or were complicated by UTIs. All these recommendations are based on the available literature. However, management of ANH is still a controversial issue due to lack of high evidence-based recommendations. Randomised controlled studies are still needed to provide a high level evidence for different aspects of management.

Prenatal Urinary Tract Dilatation

Urinary tract dilatation (UTD) is the most common congenital anomaly detected on prenatal ultrasonography (US), affecting 1% to 3% of all pregnancies. This article focuses on the prenatal detection of UTD and the postnatal evaluation and management based on the UTD grading system risk assessment. Prophylactic antibiotics and postnatal imaging are discussed. The recent management trend is for a more conservative approach to minimize unnecessary testing and exposures to the fetus and neonate while detecting those who may have clinically significant disorder. The renal bladder US remains a critical part of the evaluation and helps guide further investigations.

Outcome of antenatal hydronephrosis in northeastern Thailand

Background: Antenatal hydronephrosis (ANH) is a condition characterized by fetal renal pelvic dilatation during pregnancy. It is detected in 1%-5% of all pregnancies. Most cases of ANH are physiological in nature, but some are pathological and can cause morbidity.

Objective: To determine: (a) the causes of ANH; (b) the factors associated with complications; and, (c) the factors associated with surgical intervention.

Methods: We reviewed the medical records of infants diagnosed with ANH; defined by a renal pelvic anteroposterior diameter ≥5 mm (based on antenatal ultrasonography) and being followed-up at Srinagarind Hospital.

Results: Forty-six infants (32 boys and 14 girls) with ANH were identified. Over half (57%) were born in our hospital (in-hospital) with the condition. The two most common causes of ANH were ureteropelvic junction obstruction (32%) and transient hydronephrosis (22%). Of the 63 abnormal kidneys, 52% needed surgical intervention. Twenty-two patients (48%) had urinary tract infections and most had more than 1 episode. None of the 46 patients had end-stage renal disease, but one died because of lung hypoplasia during the neonatal period. The severity of ANH and time of first postnatal ultrasonography were related to medical complications, while bilateral ANH and more severe ANH were associated with the need for surgical intervention. A milder degree of ANH and postnatal ultrasound findings were significantly associated with transient hydronephrosis.

Conclusion: Most cases of ANH were pathological and half required surgical intervention. Severe ANH and delayed investigation were associated with poor outcomes.

Prenatal natural history of isolated fetal mild bilateral pyelectasis

OBJECTIVE

To analyze the prenatal outcomes in a cohort of fetuses with mild bilateral pyelectasis and determine whether performing serial ultrasounds is a good follow-up strategy.

METHODS

A prospective longitudinal study was conducted on 62 fetuses with mild bilateral pyelectasis. Fetal mild bilateral pyelectasis was considered when the renal pelvis measured (in millimeters) ≥5.0 to 10.0, ≥7.0 to 10.0, and ≥10.0 to 15 at ≤23 weeks 6 days, 24 to 31 weeks 6 days, and ≥32 weeks, respectively, with no uretero-calyceal dilatation. Ultrasounds were performed every 3 weeks to assess whether the mild bilateral pyelectasis regressed, remained unchanged (Group 1) or progressed (Group 2).

RESULTS

Group 1 consisted of 53 fetuses (85.4%), and progression was observed in 9 cases (Group 2, 14.6%). The initial renal pelvis diameter was significantly larger in fetuses with progression (p=0.028). Statistically significant differences in the renal pelvis diameter were also found at weeks 31 and 35 for both kidneys (p<0.05). The cases requiring intrauterine procedures or early delivery were not observed.

CONCLUSION

Fetal mild bilateral pyelectasis with no calyceal dilatation is a benign condition that can be managed in the postnatal period. The initial renal pelvis diameter and the diameter in week 31 or 35 were valuable parameters for identifying cases that would eventually need specific postnatal procedures.

Characterizing upper urinary tract dilation on ultrasound: a survey of North American pediatric radiologists' practices

BACKGROUND

Radiologists commonly evaluate children first diagnosed with urinary tract dilation on prenatal ultrasound (US).

OBJECTIVE

To establish how North American pediatric radiologists define and report findings of urinary tract dilation on US.

MATERIALS AND METHODS

A web-based survey was sent to North American members of the Society for Pediatric Radiology (SPR) from January to February 2014. Reporting practices and interpretation of three image-based cases using free text were queried. Responses to close-ended questions were analyzed with descriptive statistics, while free-text responses to the three cases were categorized and analyzed as (1) using either descriptive terminology or an established numerical grading system and (2) as providing a quantitative term for the degree of dilation.

RESULTS

Two hundred eighty-four pediatric radiologists answered the survey resulting in a response rate of 19.0%. There is a great variety in the terms used to describe urinary tract dilation with 66.2% using descriptive terminology, 35.6% using Society for Fetal Urology (SFU) grading system and 35.9% measuring anterior-posterior diameter (APD) of the renal pelvis. There is no consensus for a normal postnatal APD or the meaning of hydronephrosis. For the same images, descriptions vary widely in degree of severity ranging from normal to mild to severe. Similar variability exists among those using the SFU system. Ninety-seven percent say they believe a unified descriptive system would be helpful and 87.7% would use it if available.

CONCLUSION

Pediatric radiologists do not have a standardized method for describing urinary tract dilation but have a great desire for such a system and would follow it if available.

Mild to moderate postnatal hydronephrosis--grading systems and management

No universal guidelines exist for the management of patients with mild to moderate antenatal hydronephrosis (ANH). Unsurprisingly, practice patterns vary considerably with respect to recommendations for postnatal evaluation and follow-up imaging schedule. Although some clinical tools are available to specifically grade ANH and postnatal hydronephrosis, these are commonly used interchangeably with varying degrees of success. A universal classification system and nomenclature are needed to best identify patients at risk of renal deterioration, UTI and need for surgical intervention. We present our own approach to postnatal risk stratification and management, including recommendations regarding serial ultrasonography schedule, prophylactic antibiotics, voiding cystourethrogram and renal scintigraphy.