Paeds · nephrology-urology-fluids-and-electrolytes
Congenital anomalies of the kidney and urinary tract
Also known as CAKUT · Congenital kidney and urinary tract anomalies · Multicystic dysplastic kidney · Renal dysplasia · Posterior urethral valves · Horseshoe kidney · Renal agenesis
Fellowship guide to congenital anomalies of the kidney and urinary tract, the CAKUT spectrum that accounts for the largest single cause of paediatric end-stage kidney disease. Covers the embryological basis in the ureteric bud and metanephric mesenchyme interaction, the classification into kidney parenchymal anomalies including multicystic dysplastic kidney and renal agenesis, ureteric anomalies, and bladder and urethral anomalies including posterior urethral valves, the antenatal and postnatal investigation pathway using ultrasound, MCUG, DMSA, and MAG3, the management from prophylactic antibiotics to surgical correction and nephrology surveillance, and the long-term risk of chronic kidney disease that every child with CAKUT carries.
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Red flags
- Bilateral renal agenesis or severe bilateral dysplasia causing Potter sequence with pulmonary hypoplasia and neonatal death
- Posterior urethral valves in a male neonate presenting with a palpable bladder, poor urinary stream, and respiratory distress from pulmonary hypoplasia
- Antenatally detected bilateral hydronephrosis with oligohydramnios signalling obstructive uropathy and impending renal failure
- Recurrent pyelonephritis in an infant with an undiagnosed obstructive uropathy causing progressive renal scarring
- Hypertension in an infant or child with a unilateral multicystic dysplastic kidney or reflux nephropathy
- Failure to thrive with a rising creatinine in a child with posterior urethral valves or bilateral renal dysplasia
- A solitary functioning kidney with proteinuria or hypertension indicating hyperfiltration injury and progressive CKD
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- Defines CAKUT as the spectrum of congenital structural malformations of the kidney and urinary tract from renal agenesis to posterior urethral valves
- Recognises antenatal hydronephrosis as the most common mode of presentation and the rationale for postnatal ultrasound
- Initiates prophylactic antibiotics for obstructive uropathy and refers for specialist urological and nephrology evaluation
- Classifies CAKUT into kidney parenchymal, ureteric, and bladder-urethral anomalies and relates each to the embryological mechanism
- Interprets the postnatal investigation pathway of ultrasound, MCUG, DMSA, and MAG3 and their indications
- Counsels on the long-term risk of chronic kidney disease from CAKUT and the rationale for life-long nephrology surveillance
- CAKUT classification, embryology, and the single-functioning kidney paradigm
- Antenatal hydronephrosis as a predictor of postnatal CAKUT and the investigation pathway
- Management of posterior urethral valves, multicystic dysplastic kidney, and long-term CKD surveillance
- Assesses a neonate with an antenatally detected renal anomaly and constructs a structured investigation plan
- Communicates the diagnosis, prognosis, and surveillance plan for a family whose child has CAKUT
- Recognises the child with progressive CKD from CAKUT and coordinates multidisciplinary care
- Level 1: Recognition of antenatal hydronephrosis and common CAKUT phenotypes
- Level 2: Initiation of postnatal investigation and prophylactic antibiotics for obstructive uropathy
- Level 3: Coordination of multidisciplinary urology and nephrology care and long-term CKD surveillance
- Embryological basis of CAKUT and the ureteric bud to metanephric mesenchyme interaction
- Classification into parenchymal, ureteric, and bladder-urethral anomalies
- Investigation pathway of ultrasound, MCUG, DMSA, and MAG3 and the long-term CKD risk
- Assessment of a newborn with an antenatal renal finding and construction of the postnatal plan
- Interpretation of the renal ultrasound, MCUG, DMSA scan, and MAG3 renogram in a child with CAKUT
- Structured explanation of the management, surgical options, and long-term surveillance
- CAKUT classification and the embryological origin of each anomaly type
- Antenatal hydronephrosis grading and the postnatal evaluation and antibiotic prophylaxis pathway
- Long-term complications including CKD, hypertension, and recurrent UTI
- Recognition of CAKUT as the leading cause of paediatric end-stage kidney disease
- Initiation of prophylactic antibiotics and timely referral for obstructive uropathy
- Family communication around diagnosis, surgical options, and the life-long CKD risk
- Canadian approach to CAKUT with standardised antenatal and postnatal imaging protocols
- Population-based surveillance for long-term renal outcomes in posterior urethral valves
- Transition of care from paediatric to adult nephrology for young adults with CAKUT
Overview & Definition
A newborn with a palpable abdominal mass, an antenatal finding of hydronephrosis, or a male infant with a poor urinary stream has the hallmark presentation of a congenital anomaly of the kidney and urinary tract. The group of structural malformations known by the acronym CAKUT spans the entire urinary tract from the renal parenchyma to the urethra, and it is the single largest cause of end-stage kidney disease in children worldwide. The common thread is a developmental error in kidney or urinary tract formation during embryogenesis, which manifests as malformation, obstruction, or dysplasia. [1]
The spectrum ranges from mild anomalies that cause no symptom and are found incidentally, to severe bilateral malformations that are fatal in the newborn period from pulmonary hypoplasia and renal failure. At one end is the unilateral multicystic dysplastic kidney that involutes over years and needs only surveillance, and at the other is bilateral renal agenesis, the Potter sequence, in which the absence of amniotic fluid prevents lung development and the newborn dies of respiratory failure within hours. Between these extremes lie the common and testable conditions: posterior urethral valves, renal hypoplasia, vesicoureteral reflux, and duplex collecting systems. [4]
The clinical importance of CAKUT lies in its cumulative burden. Individual anomalies may seem minor in isolation, but the risk of urinary tract infection, hypertension, and progressive renal scarring accumulates over childhood. Harambat and colleagues showed that CAKUT accounts for the largest proportion of paediatric chronic kidney disease in registry data, which is why every child with an antenatal renal finding needs structured postnatal evaluation and life-long nephrology surveillance. [10]
References12ShowHide
- [1]Murugapoopathy V, Gupta IR A Primer on Congenital Anomalies of the Kidneys and Urinary Tracts (CAKUT). Clin J Am Soc Nephrol, 2020.PMID 32188635
- [2]Kolvenbach CM, Shril S, Hildebrandt F The genetics and pathogenesis of CAKUT. Nat Rev Nephrol, 2023.PMID 37524861
- [3]Brockwell M, Hergenrother S, Satariano M, et al. Pathophysiology of Congenital Anomalies of the Kidney and Urinary Tract: A Comprehensive Review. Cells, 2024.PMID 39594614
- [4]Rodriguez MM Congenital Anomalies of the Kidney and the Urinary Tract (CAKUT). Fetal Pediatr Pathol, 2014.PMID 25313840
- [5]Matsell DG, Bao C, Po White T, et al. Outcomes of solitary functioning kidneys-renal agenesis is different than multicystic dysplastic kidney disease. Pediatr Nephrol, 2021.PMID 33954810
- [6]Aslam M, Watson AR Unilateral multicystic dysplastic kidney: long term outcomes. Arch Dis Child, 2006.PMID 16754654
- [7]Lee RS, Cendron M, Kinnamon DD, Nguyen HT Antenatal hydronephrosis as a predictor of postnatal outcome: a meta-analysis. Pediatrics, 2006.PMID 16882811
- [8]Robinson CH, Rickard M, Jeyakumar N, et al. Long-Term Kidney Outcomes in Children with Posterior Urethral Valves: A Population-Based Cohort Study. J Am Soc Nephrol, 2024.PMID 39167453
- [9]Caione P, Nappo SG Posterior urethral valves: long-term outcome. Pediatr Surg Int, 2011.PMID 21748651
- [10]Harambat J, van Stralen KJ, Kim JJ, Tizard EJ Epidemiology of chronic kidney disease in children. Pediatr Nephrol, 2012.PMID 21713524
- [11]Rao J, Liu X, Mao J, Tang H, Li Y, Shen Q, et al Genetic spectrum of renal disease for 1001 Chinese children based on a multicenter registration system. Clin Genet, 2019.PMID 31328266
- [12]Liu DB, Armstrong WR 3rd, Maizels M Hydronephrosis: prenatal and postnatal evaluation and management. Clin Perinatol, 2014.PMID 25155734