Renal dysplasia

Practical Approach to Congenital Anomalies of the Kidneys: Focus on Anomalies With Insufficient or Abnormal Nephron Development: Renal Dysplasia, Renal Hypoplasia, and Renal Tubular Dysgenesis

Congenital anomalies of the kidney and urinary tract (CAKUT) accounts for up to 30% of antenatal congenital anomalies and is the main cause of kidney failure in children worldwide. This review focuses on practical approaches to CAKUT, particularly those with insufficient or abnormal nephron development, such as renal dysplasia, renal hypoplasia, and renal tubular dysgenesis. The review provides insights into the histological features, pathogenesis, mechanisms, etiologies, antenatal and postnatal presentation, management, and prognosis of these anomalies. Differential diagnoses are discussed as several syndromes may include CAKUT as a phenotypic component and renal dysplasia may occur in some ciliopathies, tumor predisposition syndromes, and inborn errors of metabolism. Diagnosis and genetic counseling for CAKUT are challenging, due to the extensive variability in presentation, genetic and phenotypic heterogeneity, and difficulties to assess postnatal lung and renal function on prenatal imaging. The review highlights the importance of perinatal autopsy and pathological findings in surgical specimens to establish the diagnosis and prognosis of CAKUT. The indications and the type of genetic testing are discussed. The aim is to provide essential insights into the practical approaches, diagnostic processes, and genetic considerations offering valuable guidance for pediatric and perinatal pathologists.

Congenital anomalies of the kidney and urinary tract

Congenital Anomalies of the Kidney and Urinary Tract (CAKUT) refer to a range of conditions that affect the kidney and urinary tract. These anomalies can be severe, such as kidney agenesis, or milder, such as vesicoureteral reflux. CAKUT affects over 1% of live births and accounts for 40-50% of cases of chronic kidney failure in children. The pathogenesis of CAKUT is caused by various environmental, genetic, and epigenetic factors that disrupt normal nephrogenesis. Environmental factors that can lead to CAKUT include maternal diabetes, obesity, malnutrition, alcohol consumption, or medications affecting kidneys development. Genetic factors can cause an imbalance in the metanephros and the ureteric bud interaction. Defects in specific genes such as PAX2, TBX18, NRIP1, REX, SIX2, BMP4, and chromosome 17 cause CAKUT. Over 50 genes have been identified as the root cause of this condition, with monogenetic variants causing up to 20% of all cases. CAKUTs can be diagnosed through fetal ultrasonography, but some anomalies may remain undetected. GWASs, Next Generation Sequencing for targeted and whole exome DNA sequencing may provide additional diagnostic methods. This review article highlights some the leading factors that cause CAKUT, which adversely affects kidney development and urinary tract function.

Insights into Kidney Dysplasia in Duplex Kidneys: From Radiologic Diagnosis to Histopathologic Understanding

Duplex kidney is a urinary tract anomaly commonly associated with a wide range of primary and secondary parenchymal structural abnormalities. We present a unique comparison of US and MRI findings with histopathology following partial resection of duplex kidneys due to nephropathy. We examined a group of 21 children with duplex kidneys who were qualified for heminephrectomy (24 kidney units (KU)). All patients underwent US and MRI prior to the surgery. The imaging results were compared with histopathologic findings. In 21/24 KU, dysplastic changes were found on histopathology, including all with obstructive nephropathy and 7/10 specimens with refluxing uropathy. The loss of corticomedullary differentiation on US and increased signal on T2-weighted images (T2WI) on MRI were the imaging findings that best correlated with fibrosis. In children with megaureter, there were no statistical differences in histopathological findings between primary megaureter, megaureter with ureterocele, and megaureter with ectopia (p > 0.05). The extent of dysplasia of the affected pole correlated negatively with residual function in MRI. Kidney dysplasia and inflammation in the kidney with obstructive nephropathy are the most important histopathologic findings of this study. US is a valuable screening tool, and MRI enables morphologic and functional assessments of the nephropathy in duplex kidneys.

Multicystic renal dysplasia, a histomorphological spectrum: Seven years experience from a tertiary care hospital

OBJECTIVES

Multicystic dysplastic kidney (MCDK) is defined as the presence of multiple noncommunicating cysts of various sizes, detected sonographically, without evidence of functioning renal parenchyma on dimercaptosuccinic acid renal scan. It has an incidence of 1:4000 live births. They are more commonly diagnosed in boys, usually on the left side, but may also be bilateral. There is the presence of primitive ducts surrounded by fibromuscular connective tissue. These are because of the disturbed connection of the ureteric bud with renal blastema and abnormal division at the stage of metanephros, resulting in an abnormal metanephros differentiation.

MATERIALS AND METHODS

Thirty cases of MCDK were included to study their histomorphology along with their clinical features. Cases were retrieved from the last seven years (2015-2021) from the Department of Pathology, Maulana Azad Medical College.

RESULT

Age ranged from 10 days to 18 years. The cases were between 1 years and 5 years of age. Six out of 30 cases (20%) were infants with three of them being neonates. Twenty-one cases were males. All the cases had unilateral kidney involvement with the left kidney being involved in 20 out of 30 cases. Twenty-eight cases underwent nephrectomy in view of small contracted nonfunctional kidneys with one of them being horseshoe shaped. Five cases had associated hydronephrosis (two ipsilateral and three bilateral). One case had Hirshprung's disease, four had anorectal malformation, two had posterior urethral valves with vesicourethral reflux, one had duplex moiety, and one had undescended testes. On histopathological examination, all of them showed the presence of immature disorganized tubules surrounded by a collarette of immature mesenchymal stroma. One of the cases showed osteoid formation and four had areas of immature cartilage. Normal kidney parenchyma was seen at the periphery in four cases.

CONCLUSION

This series has been presented to highlight the various histomorphological features of MCDK. MCDK can be managed conservatively in most of cases due to autoinvolution and, hence, needs to be differentiated from other close differentials like polycystic kidney disease, cystic nephroma, and cystic partially differentiated nephroblastoma in order to avoid unnecessary surgical intervention.

A renal aplasia case mimicking radiologically as unilateral renal agenesis in a child with spina bifida, atresia ani and unilateral undescended testis: a case report

BACKGROUND

As a result of the failure of embryogenic kidney formation, a condition can occur where not a single kidney appears and this phenomenon is known as unilateral renal agenesis (URA). Both aplastic and dysplastic kidney are different from renal agenesis, atrophy and renal hypoplasia. However, from this case report it can be seen that there are similarities, both radiologically and macroscopically, between cases of unilateral renal aplasia and renal agenesis.

CASE PRESENTATION

A 2 year old Javanese boy came to the health facility with complaints of recurrent fever and urinary tract symptoms such as dysuria and straining. Computerized Tomography (CT) scan of the abdomen and urography showed agenesis of the left kidney and a probable spina bifida. Cystourethrography examination was done and showed grade 5 voiding, then retrograde pyelography was performed with the diagnosis of unilateral renal agenesis was made because there was no visible left side collecting system even though there was a duplication in the left ureter. The next examination was carried out by histopathology and immunohistochemistry after resection of the left side of the ureter and the diagnosis increasingly pointed towards renal aplasia after primitive renal structures were found.

CONCLUSIONS

Renal agenesis and aplastic kidney are difficult to differentiate macroscopically and radiologically. Nevertheless, from this case report, we try to provide some interesting points to differentiate cases of unilateral renal agenesis from Renal Dysplasia which presents as unilateral renal aplasia.

A Spectrum of Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)-Diagnostic Utility of Perinatal Autopsy

OBJECTIVE

To describe the spectrum of congenital renal anomalies and emphasize the critical role of comprehensive autopsy examination in identifying CAKUT, especially of lower urinary tract malformations correlating with prenatal imaging methods.

METHODS

Retrospective analyses of CAKUT diagnosed at fetal autopsy were analyzed over a 7-y period and correlated with prenatal imaging findings.

RESULT

Among the 255 fetal autopsies, 45 cases were detected with CAKUT. Isolated (27%), syndromic CAKUT (51%), and CAKUT associated with other system anomalies (22%) were found. Hydronephrosis, followed by cystic renal diseases and agenesis were the common renal malformations. The gastrointestinal tract (GIT) was the commonest system associated with CAKUT. Among the syndromic CAKUT, the urorectal septum malformation (URSM) was the most frequent one, followed by VACTER-L, acrorenal syndrome, and OEIS complex. When correlating prenatal USG and autopsy findings, a significant change in final diagnosis was observed in 60% of cases.

CONCLUSION

Extrarenal malformations and syndromic associations of CAKUT predominated over isolated ones. Detection of lower urinary tract anomalies in CAKUT is difficult through antenatal imaging methods if associated with oligohydramnios. In these circumstances, the perinatal autopsy has a significant role in arriving at the final diagnosis which guides the clinician in predicting the recurrence risk and the need for genetic workup.

Case report: BCL-2 and CD31 immunoexpression related to clinical and histopathological evaluation of renal dysplasia in a Welsh Corgi Puppy

A case of renal dysplasia (RD) in the Welsh Corgi dog has been reported. Clinically, the affected 3-month-old, female, Welsh Corgi dog showed unclear symptoms of chronic kidney disease. Grossly, both left and right kidneys revealed cystic hypoplasia. Histologically, the primary lesions included immature or fetal glomeruli/tubules, proliferative arterioles, persistent metanephric ducts, persistent mesenchyme, and atypical tubular epithelium were presented. A group of degenerative and inflammatory lesions consisting of interstitial nephritis, interstitial fibrosis, and mineralization of tubules were found. Immunohistochemically, the epithelial cells of immature (fetal) tubules had BCL-2 labeling whereas CD31 (PECAM-1) was labeled in the endothelial cells of the proliferative arterioles. The immunohistochemical findings were confirmed and consolidated with the routine histopathological findings. This study was the first demonstration of the clinical, histopathological, and immunohistochemical features of RD disease in a Welsh Corgi puppy.

Acute kidney injury in pediatrics: an overview focusing on pathophysiology

Acute kidney injury (AKI) is defined as an abrupt decline in glomerular filtration rate, with increased serum creatinine and nitrogenous waste products due to several possible etiologies. Incidence in the pediatric population is estimated to be 3.9 per 1,000 hospitalizations, and prevalence among children admitted to intensive care units is 26.9%. Despite being a condition with important incidence and morbimortality, further evidence on pathophysiology and management among the pediatric population is still lacking. This narrative review aimed to summarize and discuss current data on AKI pathophysiology in the pediatric population, considering all the physiological particularities of this age range and common etiologies. Additionally, we reported current diagnostic tools, novel biomarkers, and newly proposed medications that have been studied with the aim of early diagnosis and appropriate treatment of AKI in the future.

The Impact of Functional and Structural Maturation of the Kidney on Susceptibility to Drug and Chemical Toxicity in Neonatal Rodents

Drug responses are often unpredictable in juvenile animal toxicity studies; hence, optimizing dosages is challenging. Renal functional differences based on age of development will often result in vastly different toxicologic responses. Developmental changes in renal function can alter plasma clearance of compounds with extensive renal elimination. Absorption, distribution, metabolism, and excretion of drugs vary depending on animal age and kidney maturation. Toxicity can result in malformations or renal degeneration. Although renal morphologic development in humans generally occurs in utero, maximal levels of tubular secretion, acid-base equilibrium, concentrating ability, or glomerular filtration rate (GFR) are reached postnatally in humans and animals and subject to drug effects. Maturation of renal metabolism and transporters occurs postnatally and plays a critical role in detoxification and excretion. Maturation times must be considered when designing juvenile toxicity studies and may require cohorts of animals of specific ages to achieve optimal dosing schemes and toxicokinetics. In recent years, critical end points and windows of susceptibility have been established comparatively between species to better model pharmacokinetics and understand pediatric nephrotoxicity. There are examples of agents where toxicity is enhanced in neonates, others where it is diminished, and others where rat nephrotoxicity is expressed as juvenile toxicity, but in humans as gestational toxicity.

Congenital Unilateral Renal Aplasia in a Cynomolgus Monkey (Macaca fascicularis) With Investigation Into Potential Pathogenesis

We describe and characterize unilateral renal aplasia in a cynomolgus monkey (Macaca fascicularis) from a chronic toxicology study adding to the limited histopathology reports of congenital renal anomalies in macaques. In the current case, the affected kidney was macroscopically small and characterized microscopically by a thin cortex with an underdeveloped medulla and an absent papilla. The remnant medulla lacked a corticomedullary junction and contained only a few irregular collecting duct-like structures. The cortex had extensive interstitial mature collagen deposition with fibromuscular collar formation around Bowman's capsules. Due to parenchymal collapse, mature glomeruli were condensed together with occasional atrophic and sclerotic glomeruli. The majority of the cortical tubules were poorly differentiated with only small islands of fully developed cortical tubules present. Histochemical and immunohistochemical stains were utilized to demonstrate key diagnostic features of this congenital defect, to assist with differentiating it from renal dysplasia, and to provide potential mechanistic pathways. Immunostaining (S100, paired box gene 2 [PAX2], aquaporins) of the medulla was compatible with incomplete maturation associated with aplasia, while the immunostaining profile for the cortex (vimentin, calbindin, PAX2-positive cortical tubules, and smooth muscle actin-positive fibromuscular collars) was most compatible with dedifferentiation secondary to degenerative changes.

Challenges in primary focal segmental glomerulosclerosis diagnosis: from the diagnostic algorithm to novel biomarkers

Primary or idiopathic focal segmental glomerulosclerosis (FSGS) is a kidney entity that involves the podocytes, leading to heavy proteinuria and in many cases progresses to end-stage renal disease. Idiopathic FSGS has a bad prognosis, as it involves young individuals who, in a considerably high proportion (∼15%), are resistant to corticosteroids and other immunosuppressive treatments as well. Moreover, the disease recurs in 30–50% of patients after kidney transplantation, leading to graft function impairment. It is suspected that this relapsing disease is caused by a circulating factor(s) that would permeabilize the glomerular filtration barrier. However, the exact pathologic mechanism is an unsettled issue. Besides its poor outcome, a major concern of primary FSGS is the complexity to confirm the diagnosis, as it can be confused with other variants or secondary forms of FSGS and also with other glomerular diseases, such as minimal change disease. New efforts to optimize the diagnostic approach are arising to improve knowledge in well-defined primary FSGS cohorts of patients. Follow-up of properly classified primary FSGS patients will allow risk stratification for predicting the response to different treatments. In this review we will focus on the diagnostic algorithm used in idiopathic FSGS both in native kidneys and in disease recurrence after kidney transplantation. We will emphasize those potential confusing factors as well as their detection and prevention. In addition, we will also provide an overview of ongoing studies that recruit large cohorts of glomerulopathy patients (Nephrotic Syndrome Study Network and Cure Glomerulonephropathy, among others) and the experimental studies performed to find novel reliable biomarkers to detect primary FSGS.

Quercetin treatment reduces the severity of renal dysplasia in a beta-catenin dependent manner

Renal dysplasia, the major cause of childhood renal failure, is characterized by defective branching morphogenesis and nephrogenesis. Beta-catenin, a transcription factor and cell adhesion molecule, is markedly increased in the nucleus of kidney cells in human renal dysplasia and contributes to its pathogenesis by altering target genes that are essential for kidney development. Quercetin, a naturally occurring flavonoid, reduces nuclear beta-catenin levels and reduces beta-catenin transcriptional activity. In this study, we utilized wild type and dysplastic mouse kidney organ explants to determine if quercetin reduces beta-catenin activity during kidney development and whether it improves the severity of renal dysplasia. In wild type kidney explants, quercetin treatment resulted in abnormal branching morphogenesis and nephrogenesis in a dose dependent manner. In wild type embryonic kidneys, quercetin reduced nuclear beta-catenin expression and decreased expression of beta-catenin target genes Pax2, Six2, and Gdnf, which are essential for kidney development. Our RD^B mouse model of renal dysplasia recapitulates the overexpression of beta-catenin and histopathological changes observed in human renal dysplasia. RD^B kidneys treated with quercetin resulted in improvements in the overall histopathology, tissue organization, ureteric branching morphogenesis, and nephrogenesis. Quercetin treatment also resulted in reduced nuclear beta-catenin and reduced Pax2 expression. These improvements were associated with the proper organization of vimentin, NCAM, and E-cadherin, and a 45% increase in the number of developing and maturing nephrons. Further, our results show that in human renal dysplasia, beta-catenin, vimentin, and e-cadherin also have abnormal expression patterns. Taken together, these data demonstrate that quercetin treatment reduces nuclear beta-catenin and this is associated with improved epithelial organization of developing nephrons, resulting in increased developing nephrons and a partial rescue of renal dysplasia.

Renal dysplasia masquerading as a renal mass in a child on hemodialysis

Pathological renal mass is uncommon in children. It is important to differentiate this from a benign mass or mass-like lesion (pseudomass) for proper management. Renal dysplasia is a common finding in patients with end stage renal disease and can mimic a renal mass. Here, we report a 16-year-old girl on hemodialysis who was found to have a nodular right renal mass in the sonogram. Magnetic resonance imaging confirmed the nodular mass. She underwent right nephrectomy and the histopathology revealed features of renal dysplasia and end stage kidney disease without any evidence of malignancy. No further treatments were necessary. This case demonstrates that a nodular renal mass in dialysis patients does not always mean malignancy and could be a pseudomass from severe renal dysplasia. Since a sonogram may not be able to clearly define the etiology of solid mass in these patients, further evaluations including a renal histology and/or other imaging modalities are often necessary.

Zinner syndrome mimicking bladder outlet obstruction managed with aspiration

Zinner syndrome is a rare cystic malformation of seminal vesicle which consists a triad of unilateral renal agenesis, ipsilateral seminal vesicle cyst, and ejaculatory duct obstruction. The usual presentation is between the third and fourth decades of life, with infertility being the most common complaint. Ultrasound, cystoscopy, and magnetic resonance tomography (MRI) can easily detect this condition. Treatment option varies according to the presenting symptoms of the patient. We present a case of a 19-year-old male with recurrent episodes of urinary tract infection (UTI) and poor urinary stream. On ultrasound examination, the patient was found to have absent right kidney with a cystic swelling noted to be arising from prostate or seminal vesicle region which was further confirmed on MRI examination. Cystoscopy reveals a bulge on the right side of the verumontanum abutting the neck of the bladder. An ultrasound-guided aspiration of the cyst was performed which relieved the symptoms of the patient. Cystic abnormalities of the seminal vesicle are very uncommon. Symptomatic cases may present as recurrent UTI, infertility, bladder outlet obstruction, and painful ejaculation. Surveillance may be the option in the absence of clinical manifestations. Interventions such as image-guided aspiration or surgical procedures are appropriate when conservative measures prove ineffective.

Thyroid-Like Follicular Renal Cell Carcinoma Arising Within Benign Mixed Epithelial and Stromal Tumor

Thyroid-like follicular renal cell carcinoma (TLF-RCC) is an extremely rare tumor with less than 40 published reports. These tumors are morphologically distinct with striking resemblance to thyroid follicular tumors, but immunohistochemically different due to lack of thyroglobulin and thyroid transcription factor 1 expression. TLF-RCCs arise in younger patients (mean age = 41 years) with female predominance and in all reported cases were solitary tumors without coexisting epithelial or mesenchymal kidney neoplasms. In this article, we report a case of a 42-year-old woman who presented with an incidental 4-cm solid and cystic left renal mass of the upper pole, which was resected. A detailed imaging assessment, pathologic findings, and immunohistochemical studies revealed a partially encapsulated TLF-RCC arising in a background of mixed epithelial and stromal tumor.

Management of antenatally detected kidney malformations

Congenital anomalies of the kidneys and the urinary tract (CAKUT) are one of the most common sonographically identified antenatal malformations. Dilatation of the renal pelvis accounts for the majority of cases, but this is usually mild rather than an indicator of obstructive uropathy. Other conditions such as small through large hyperechogenic and/or cystic kidneys present a significant diagnostic dilemma on routine scanning. Accurate diagnosis and prediction of prognosis is often not possible without a positive family history, although maintenance of adequate amniotic fluid is usually a good sign. Both pre- and postnatal genetic screening is possible for multiple known CAKUT genes but less than a fifth of non-syndromic sporadic cases have detectable monogenic mutations with current technology. In utero management options are limited, with little evidence of benefit from shunting of obstructed systems or installation of artificial amniotic fluid. Often outcome hinges on associated cardiac, neurological or other abnormalities, particularly in syndromic cases. Hence, management centres on a careful assessment of all anomalies and planning for postnatal care. Early delivery is rarely indicated since this exposes the baby to the risks of prematurity in addition to their underlying CAKUT. Parents value discussions with a multidisciplinary team including fetal medicine and paediatric nephrology or urology, with neonatologists to plan perinatal care and clinical geneticists for future risks of CAKUT.

Renal dysplasia characterized by prominent cartilaginous metaplasia lesions in VACTERL association: A case report

BACKGROUND

Renal dysplasia is the most important cause of end-stage renal disease in children. The histopathological characteristic of dysplasia is primitive tubules with fibromuscular disorganization. Renal dysplasia often includes metaplastic cartilage. Metaplastic cartilage in renal dysplasia has been explained as occurring secondary to vesicoureteral reflux (VUR). Additionally, renal dysplasia is observed in renal dysplasia-associated syndromes, which are combinations of multiple developmental malformations and include VACTERL association.

CASE PRESENTATION

We observed the following multiple developmental malformations in a 108-day-old male infant during a nephrectomy: a nonfunctioning right kidney with VUR, hemidiaphragmatic eventration, a ventricular septal defect (VSD) with tetralogy of Fallot in the heart, cryptorchidism, and hyperdactylia. These developmental anomalies satisfied the diagnostic criteria for VACTERL association. A surgical specimen of the right nonfunctioning kidney revealed prominent cartilaginous metaplasia in the renal dysplasia with VUR. The densities of the ectopic cartilaginous lesions in this nonfunctioning kidney were extraordinarily high compared with other renal dysplasia cases. Giemsa banding of his genome produced normal results. The patient has not undergone further detailed genomic investigation.

CONCLUSION

This case might be a novel type of VACTERL association, that is, renal dysplasia combined with prominent cartilaginous metaplasia, tetralogy of Fallot and VSD of the heart, hemidiaphragmatic eventration, and hyperdactylia.

Renal development in the fetus and premature infant

Congenital abnormalities of the kidney and urinary tract (CAKUT) are one of the leading congenital defects to be identified on prenatal ultrasound. CAKUT represent a broad spectrum of abnormalities, from transient hydronephrosis to severe bilateral renal agenesis. CAKUT are a major contributor to chronic and end stage kidney disease (CKD/ESKD) in children. Prenatal imaging is useful to identify CAKUT, but will not detect all defects. Both genetic abnormalities and the fetal environment contribute to CAKUT. Monogenic gene mutations identified in human CAKUT have advanced our understanding of molecular mechanisms of renal development. Low nephron number and solitary kidneys are associated with increased risk of adult onset CKD and ESKD. Premature and low birth weight infants represent a high risk population for low nephron number. Additional research is needed to identify biomarkers and appropriate follow-up of premature and low birth weight infants into adulthood.

Epididymis-like Tubules in Adult Renal Hypodysplasia: Immunohistochemical Features Indicate a Mesonephric Origin

We report the presence of epididymis-like tubules in unilateral renal hypodysplasia in 3 adult men. Microscopy showed dilated tubules lined by ciliated columnar epithelium and smaller basal cells, morphologically resembling epididymal tubules. Small tubules lined by cuboidal epithelium were also present in all cases, with glomeruli in 2 cases. The epididymis-like tubules expressed CD10, CK7, PAX8, and AR in the luminal epithelium, while the basal cells were positive for p63, CK7, and focally for CD10. The smooth muscle bundles around the epididymis-like tubules were focally AR and WT1 (cytoplasmic) positive. The epididymis-like tubules were negative for ER, PR, and WT1. CK7 and PAX8 stained all the collecting ducts, with AR staining some. Bowman's capsule, parietal and visceral epithelial cells expressed CD10; WT1 stained the visceral and parietal epithelial cells. Glomerular parietal cells expressed PAX8 and focally, CK7. Proximal tubules were positive for CD10 (luminal membranous and weak cytoplasmic). Distal tubules expressed CK7, PAX8 and AR. An occasional small tubule was ER positive. Scattered stromal cells expressed ER, PR, and AR. The urothelium of the renal pelvis/upper ureter expressed CK7 in all layers, CD10 in the superficial layers, PAX8 in the basal layers and p63 in all layers except the umbrella layer. The epididymis-like tubules replicate the pattern of the mesonephros-derived normal epididymis in expressing CK7, PAX8, CD10, and AR. This supports a mesonephric rather than metanephric origin for these tubules. The aberrant expression of some markers may be a manifestation of the dysplastic nature of the kidneys.

The Good and Bad of β-Catenin in Kidney Development and Renal Dysplasia

Congenital renal malformations are a major cause of childhood and adult onset chronic kidney disease. Identifying the etiology of these renal defects is often challenging since disruptions in the processes that drive kidney development can result from disruptions in environmental, genetic, or epigenetic cues. β-catenin is an intracellular molecule involved in cell adhesion, cell signaling, and regulation of gene transcription. It plays essential roles in kidney development and in the pathogenesis of renal dysplasia. Here, we review the function of β-catenin during kidney development and in the genesis of renal dysplasia.