Congenital Renal Tract Abnormalities: a Neonatal Perspective

Congenital renal tract abnormalities: a neonatal perspective

Congenital renal and urinary system malformations are among the commonest congenital anomalies. They represent a wide spectrum of disorders with varying degrees of postnatal clinical significance. Many of these conditions can be detected on antenatal ultrasonography as part of the 18-20 week anomaly scan. This article will cover the postnatal management of renal dilatation and other commonly seen anomalies.

1 Pallavi Prasad he kidneys and urinary tract are the ■ Renal pelvic dilatation most common sites for congenital MBChB, MRCPCH, BMS BSc T ■ Congenital renal anomalies ST5 Paediatric Nephrology abnormalities and can account for 15-20% of all prenatally detected congenital • Renal agenesis 1 • Ectopic kidney Catherine Agar anomalies.1 Congenital renal and urinary - Pelvic kidney MBChB, MRCPCH system malformations are seen in 3-4% of - Crossed renal ectopia ST3 Community Paediatrics the population.2 - Horseshoe kidney Various conditions can result in renal Cath Harrison • Duplex kidney malformations seen on an antenatal BMedSci, BM BS, DTM&H, FRCPCH anomaly scan. Neonatal healthcare ■ Congenital cystic kidney disease Consultant Neonatologist1 and Consultant professionals should be aware of congenital • Multicystic dysplastic kidney (Neonatal Lead)2 renal abnormalities as early postnatal • Dysplastic kidney (renal dysplasia) ■ Posterior urethral valve (PUV) 1Leeds Teaching Hospitals NHS Trust intervention and appropriate long-term 2Embrace Transport Service follow-up will ensure prompt diagnosis FIGURE 1 Renal anomalies that are and management, avoid unnecessary commonly encountered in neonates. investigations and minimise renal damage. This article will review the postnatal management of the renal anomalies seen Kidney in FIGURE 1.

Anatomy of the urinary system The urinary system produces, stores and removes urine from the body. The kidneys Keywords make urine by filtering the blood to remove waste products. From the kidneys Ureter kidney; renal dilatation; congenital Pelviureteric the urine flows through the ureters to the abnormality; neonatal junction urinary bladder and then to the outside of Bladder Key points the body along the urethra during Prasad P., Agar C., Harrison C. Congenital urination. The basic anatomy of the Vesicoureteric renal tract abnormalities: a neonatal urinary tract can be seen in FIGURE 2. junction Urethra perspective. Infant 2017; 13(3): 100-104. 1. The kidneys and urinary tract are the Renal pelvic dilatation FIGURE 2 most common sites for congenital Fetal renal pelvic dilatation is a common Anatomy of the urinary system. abnormalities. anomaly detected on antenatal scanning, 2. Detection of renal anomalies during an with an incidence of 0.5-1% in pregnancy.3 significant morbidity. Renal pelvic antenatal scan enables prompt The presence of renal pelvic dilatation can dilatation can be classified according to the diagnosis and management in the indicate diseases such as structural NHS fetal anomaly scan national standards postnatal period. anomalies, obstruction or vesicoureteric (FIGURE 3).3 3. A robust screening pathway is essential reflux (VUR – an abnormal backward flow Renal pelvic dilatation is usually detected to ensure early detection, avoid of urine from the bladder to the upper on the 20-week anomaly scan with some unnecessary investigations and reduce urinary tract).3 Although mostly a benign centres offering a further serial scan at parental anxiety. condition, it can in some cases cause 30-36 weeks’ gestation.5,7 Evidence suggests

100 VOLUME 13 ISSUE 3 2017 infant REVIEW that there is uncertainty in how fetal renal Grade Renal pelvic diameter disruption in the metanephric stage in the pelvic dilatation reflects postnatal abnor- first few weeks of gestation. An important malities but it is generally agreed that there Normal <7mm differential diagnosis for unilateral agenesis is an undiagnosed ectopic kidney.11 Renal is a greater likelihood of postnatal Mild 7-10mm problems with increasing pelvic dilatation.3,8 agenesis can be diagnosed on the 20-week It is therefore essential to have a robust Moderate 10-15mm antenatal anomaly scan and/or during investigations for urinary tract infections. screening pathway to identify those infants Severe >15mm with significant renal problems to ensure In approximately 50% of children with early intervention and long-term follow- FIGURE 3 Renal dilatation grading by unilateral agenesis there is an association 3-6 up, yet avoid unnecessary investigations. anteroposterior pelvic diameter. with other congenital abnormalities of the An example of a screening pathway is urinary tract: ■ shown in FIGURE 4. ■ Renal dilatation >10mm with or with- VUR occurs in 28% of children with uni- Renal pelvic dilatation should be out other abnormalities. The infant lateral agenesis ■ managed in the following way: will require prophylactic antibiotics pelviureteric junction obstruction ■ Uncomplicated renal dilatation ≤7mm. (trimethoprim) from birth. Ideally ultra- (PUJ – blockage at the junction where the If there are no other associated renal sound will be performed before dis- ureter attaches to the kidney) and/or abnormalities (such as duplex kidney) no charge. Follow-up is required in the vesicoureteric junction obstruction (VUJ postnatal investigations are required. neonatal or urology clinic. – blockage where the ureter meets the ■ Uncomplicated renal dilatation bladder) occur in 20% of children with 10,11 7-10mm. The infant does not require Congenital renal anomalies unilateral agenesis. Seventy per cent of children with antibiotics. The first renal ultrasound Unilateral agenesis scan should take place at one month of unilateral agenesis have associated genital Unilateral agenesis – the absence of a single age; it is important the scan is not anomalies that can be either minor or kidney – has an incidence of approximately major, such as an absent gonad on the delayed. Follow-up is necessary after the 9,10 one in 1,000 to one in 3,200 live births. ipsilateral side.6,12 Long-term outcomes can one-month scan if the abnormalities Renal agenesis occurs after a major persist. be varied and dependent on the quality of

Guidelines for the investigation of prenatal renal pelvic dilatation

Renal pelvis 7-10mm Renal pelvis >10mm OR Antenatal Ureters normal dilated ureters (20 week scan) +/- other suspicious features

Ultrasound scan before discharge + antibiotics No antibiotics Bilateral dilatation in a boy Early postnatal Pelvis <15mm Pelvis ≥15mm OR Urgent MCU Ureters and calyces dilated calyces OR ureter(s) (Valves?) normal Urgent surgical Pelvis and calyces only Dilated ureters OR referral Probable PUJ thickwalled bladder 1 Month Ultrasound scan Ultrasound scan + No valves Ultrasound + prompt MCU Unexpected MAG3 renogram Normal scan Pelvis 6-14mm* No reflux Mild reflux valves pelvis ≤5mm Stop antibiotics VUJ? (Grade 1)

Significant reflux Ultrasound scan (grades 2-5) Static situation* 3 Months or residual Reducing dilatation dilatation ≥10mm pelvis <10mm

Outcome Discharge Surgical referral Monitor/treat Refer nephrology *If pelvis increases ≥15mm Ureters OR calyces dilated – investigate as significant FIGURE 4 The Leeds Teaching Hospital’s neonatal guideline for investigation of prenatal renal pelvic dilatation.6 Key: MCU = micturating cystourethrography (used to examine whether reflux is occurring during urination), PUJ = pelvicureteric junction obstruction, MAG3 = MAG3 renogram (a scan to assess whether the kidneys are draining properly into the bladder), VUJ = vesicoureteric junction obstruction. infant VOLUME 13 ISSUE 3 2017 101 REVIEW the existing kidney. If there is normal renal VUR. They can be associated with non- cases.10 Renal calculi can also occur in function and no other associated abnor- renal anomalies (cardiac, skeletal) or part approximately 20-60% of patients due to malities the outcome is excellent.5,10,12 of syndromes such as in CHARGE the presence of hydronephrosis (a build-up syndrome and VACTERL association.15, 16 of urine leading to distension and dilation Action Pelvic kidneys are the commonest form of the kidney) or obstruction causing Infants should have a postnatal ultrasound of renal ectopia (90%) with a left-sided urinary stasis and infection. PUJ scan as an out-patient within the first predominance.5 The majority of patients obstruction is seen due to the high inser- month of life to measure the size of the with this are asymptomatic. tion of the ureter into the renal pelvis and single kidney and to look for other renal In crossed renal ectopia, one kidney displacement of the isthmus.14 Other abnormalities. Small ectopic kidneys and crosses the midline and its ureter re-crosses complications include: trauma to the pelvic kidneys can be difficult to visualise the midline to fuse with the bladder on the isthmus, an increased risk of Wilms’ on antenatal scans, therefore a postnatal correct side. In the majority of cases tumour and hypertension secondary to scan is indicated to verify the antenatal (85-90%) the two kidneys are fused, most renal cortical scarring.10 findings. There may also be evidence of commonly the lower pole of the normal Action compensatory renal hypertrophy (>50th kidney with the upper pole of the ectopic centile for age and height) on the kidney as it sits inferiorly, medially and Infants should have a postnatal ultrasound contralateral normal kidney, which is a abnormally rotated.12, 17 This condition is to confirm the ectopic kidney and to deter- reassuring sign. associated with ureteric and lower tract mine if there is any associated There is no need for antibiotic prophy- lesions and with cloacal and anorectal hydronephrosis and obstruction in either laxis or other investigations provided the malformations.10 kidney. If there is evidence of hydro- ultrasound shows a normal single kidney. A horseshoe kidney (FIGURE 5) is the nephrosis the baby will require further commonest form of fusion anomaly with investigations in the first six weeks Follow-up an incidence of one in 400-800 babies, with including: Infants should have serial ultrasound scans a male to female prevalence of 2:1.5,14 A ■ a micturating cystourethrogram (MCU) at six months and 12 months to monitor horseshoe kidney usually involves fusion of to detect reflux for compensatory renal hypertrophy. If the lower poles of the kidneys by a narrow ■ a MAG3 renogram (technetium 99m- present, yearly blood pressure monitoring isthmus of renal tissue.17 The kidneys are mercaptotriglycylglycine, Tc99m) to and urine analysis to check for proteinuria also more caudally situated than normal.15 exclude obstruction is recommended (in primary care). If there There is a strong association with chromo- ■ a 99mTc-DMSA (dimercaptosuccinic is any evidence of raised blood pressure or somal abnormalities, such as in Turner acid) scan to detect ectopic renal tissue. syndrome, and females with a horseshoe proteinuria with a raised creatinine level, Follow-up referral to a paediatric nephrologist is kidney should have karyotyping.12 Infants will need follow-up with urology or advised. If absent, glomerular filtration rate Horseshoes kidneys are usually asympt- with a nephrologist depending on the measurement is recommended at one year omatic (90%) and found incidentally. findings and the renal function. of age by the nephrology team. In the Occasionally, however, they can cause presence of abnormal renal function or problems such as UTIs, abdominal pain Advise 12 10 and haematuria. There are recognised size, long-term follow-up is advised. Parents should be advised of the need for complications of horseshoe kidneys: UTIs prophylactic antibiotics if there is evidence Advise secondary to VUR occur in up to half of of obstruction or recurrent UTIs. Parents should be advised about early detection and management of urinary tract Duplex kidney infections. Kidney This is a common anomaly, often familial There is now evidence to show that and occurs in 1% of the population.10 It children with a single kidney need not arises by the duplication of the ureteric avoid contact sports.13 bud resulting in two collecting systems with two renal pelves and two ureters Ectopic kidney (FIGURE 6). Duplex kidneys are mostly The incidence of an ectopic kidney – benign and asymptomatic but can be any kidney not located in its normal associated with obstruction and reflux.5 6,14 anatomical position – is one in 1,000. In complete duplication the kidney has Ectopic kidneys can be found anywhere two moieties and each of these has its own along the embryological ascending ureter that enters the bladder separately. pathway within the abdomen and thorax, The upper pole ureter enters the bladder although the majority are found in the medially and below that of the lower pole pelvis.12,14 They are mostly unilateral, very ureter. It can also insert ectopically into the rarely bilateral and not of reniform Bladder Isthmus urethra or vagina causing dribbling and shape5,10,15 and can lead to obstruction, the development of an ureterocoele (a urinary tract infections (UTI) or renal FIGURE 5 The horseshoe kidney usually cystic dilatation of the ureter), which can calculi. There is also a high incidence of involves fusion of the lower poles of the lead to obstruction and hydronephrosis of urological complications, particularly kidneys by a narrow isthmus of renal tissue. the upper pole. The lower pole ureter is at

102 VOLUME 13 ISSUE 3 2017 infant REVIEW risk of reflux and scarring. It can also Advise occasionally lead to a PUJ obstruction or Antibiotics are not necessary unless the dysplasia of the lower pole.10 ultrasound scan shows evidence of hydronephrosis. Action If there is evidence of hydronephrosis, Posterior urethral valves (PUV) ureteric dilatation or other suspicious A PUV is an obstructing membranous fold features, follow the renal tract dilatation in the posterior male urethra leading to guideline (FIGURE 4). bladder outlet obstruction in newborn Follow-up baby boys. Often diagnosed on antenatal scans, this is a serious condition presenting If the infant is asymptomatic with no with bilateral renal pelvic dilatations and abnormal signs, further imaging is oligohydramnios. The incidence is one in generally not required. Some centres do 5,000-8,000 male live births.18 PUV is the offer a routine ultrasound scan at 1-3 most common cause of urinary tract months.5 Ureterocoele obstruction in males.1 The severity of the Advise obstruction varies; one third of babies will have end stage renal failure.6 Milder cases Parents should be advised about early FIGURE 6 A left duplex kidney. The kidney has detection and management of UTIs. two moieties, each with its own ureter. of PUV can present in infancy with infection, poor urinary stream and/or a palpable bladder. Cystic kidney disease regression and then every 2-3 years. Multicystic dysplastic kidney (MCDK) Regular blood pressure monitoring and Action This is the commonest and severest form urine analysis are also recommended. Once Antenatal counselling is essential. A post- of cystic kidney disease. It is twice as regression has developed, this could be natal ultrasound scan and MCU should be common in males as females and is mostly performed in primary care. performed in the first few days of life. Early diagnosed on antenatal scans. The There is a life-time risk of malignancy of catheterisation (per urethra or supra-pubic incidence is one in 45,000 for unilateral one in 2,500. A nephrectomy may be catheter) by a paediatric surgeon/urologist 6 MCDK with the left kidney being more performed to prevent Wilms’ tumour. may be necessary. Refer to a nephrologist affected, and one in 20,000 for bilateral Advise especially in the presence of abnormal MCDK, which is fatal.6,18 This condition is renal function and hypertension. Parents should be advised that there is no believed to be secondary to dysfunctional need for antibiotics unless an ultrasound genetics, abnormal differentiation of the Follow-up scan shows evidence of hydronephrosis. metanephros or in utero ureteral Ongoing input from the urology and obstruction. Dysplastic kidney (renal dysplasia) nephrology teams is necessary. Further ultrasound, MCU and DMSA studies will Within the kidney there are numerous A dysplastic kidney is usually small with be needed. The infant may require long- non-communicating cysts separated by unusual architecture on histology with dysplastic tissue with very limited func- term management for chronic kidney malformed renal parenchymal tissue such 6 18 disease. tional renal tissue. If the contralateral as the presence of immature tubules, cysts kidney is normal there should be evidence and non-renal tissue (eg cartilage and Conclusions of compensatory hypertrophy. The contra- fat).6,18 The incidence is two to four in Various conditions can result in kidney lateral kidney is hydronephrotic in 5-10% 1,000 live births.18 Renal dysplasia can be of cases, and can be associated with other unilateral or bilateral; for bilateral, the malformations. Fetuses presenting with problems such as VUR, rotational and male to female ratio is 1.3:1 and for abnormalities at an antenatal scan should positional anomalies and dysplastic areas.6,18 unilateral 1.9:1. Genetic syndromes that be investigated early in the postnatal affect multiple body systems can cause period. Identifying these conditions Action kidney dysplasia, however it can also be promptly will ensure timely management Babies with an antenatal diagnosis should non-syndromic. There may be an and can prevent or reduce renal damage, have an ultrasound scan in the first two association with posterior urethral valves. however, a balance is needed between over weeks of life; a DMSA study at three investigation and treatment to identify months to confirm non-function of the Action high risk babies yet minimise parental affected kidney; and a MAG3 renogram at A postnatal ultrasound scan is required to anxiety. three months if obstruction in the other confirm the size of the kidney(s). kidney is seen on an ultrasound scan. References Follow-up 1. Chiaramonte C., Bommarito D., Zambaiti E. et al. Follow-up The infant should be referred to the renal Genetic basis of posterior urethral valves Usually MCDK disappears (involutes) by team for further investigation. If an ultra- Inheritance. Urology 2016;95:175-79. 2. Menasinkai S.B., Chiniwar M.A., Sarawathi G. the time a child reaches school age. An sound scan shows signs of obstruction Urinary system anomalies at birth. Int J Res Med Sci annual ultrasound scan under the care of further studies will be necessary 2015;3:743-48. the renal team is recommended until (MCU/MAG3). 3. Kirwan D., NHS Fetal Anomaly Screening infant VOLUME 13 ISSUE 3 2017 103 REVIEW

Programme. Fetal Anomaly Scan National Standards pelvic dilatation. Prenat Diagn 2012;32:519-22. 1019-27. and Guidance for England. NHS FASP; 2010. 9. Cascio S., Paran S., Puri P. Associated urological 14. Rosenblum N.D. Renal Ectopic and Fusion Anomalies. 4. Hothi D.K., Wade A.S., Gilbert R., Winyard P.J.D. Mild anomalies in children with unilateral renal agencies. 2015 [online]. Available at: www.uptodate.com/ fetal renal pelvic dilatation: much ado about J Urol 1999;162:1081-83. contents/renal-ectopic-and-fusion-anomalies nothing? Clin J Am Soc Nephrol 2009;4:168-77. 10. Rees L., Webb N., Brogan P. Paediatric Nephrology. [Accessed 4 May 2017]. 5. Wallis S. Renal Abnormalities. Bradford Royal 1st Ed. 2007. New York: Oxford University Press 15. Meizner I., Barnhard Y. Bilateral fetal pelvic kidneys: Infirmary. pp:42-49 and 56-59. documentation of two cases of a rare prenatal 6. Preece J., Booth D., Ramsden W., Humphrey T. Leeds 11. Parikh C.R., McCall D., Engelmann C., Schrier R.W. finding. J Ultrasound Med 1995;14:487-89. Neonatal Guideline for Investigation of Prenatal Congenital renal genesis: case-control analysis of 16. Evans J.A., Stranc L.C., Kaplan P., Hunter A.G. Renal Dilatation. Leeds Health Pathways. birth characteristics. Am J Kidney Dis 2002;39:689- VACTERL with hydrocephalus: further delineation of 7. Liverpool Women’s NHS Foundation Trust. Renal 94. the syndrome(s). Am J Med Genet 1989;34:177-82. Pelvis Dilation. 2011 [online]. Available at: 12. Webb N., Postlethwaite R. Clinical Paediatric 17. Bhatt K., Herts B.R. et al. Crossed fused renal www.liverpoolwomens.nhs.uk/library/our_services/ Nephrology. 3rd Edition. 2003. New York: Oxford ectopic. J Urol 2014;191:475-76. maternity/fmu/renal_pelvis_dilation.pdf [Accessed University Press pp:239-42. 18. Niaudet P. Renal Cystic Diseases in Children. 2016 4 May 2017]. 13. Grinsell M.M., Showalter S., Gordon K.A, Norwood [online]. Available at: www.uptodate.com/contents/ 8. Kumar S., Walia S., Ikpeme O. et al. Postnatal V.F. Single kidney and sports participation: renal-cystic-diseases-in-children [Accessed 4 May outcome of prenatally diagnosed severe fetal renal perception versus reality. Pediatrics 2006;118: 2017].

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