Congenital anomalies of the kidney and urinary tract

A Case of Horseshoe Kidney and Autosomal Dominant Polycystic Kidney Disease with PKD1 Gene Mutation

Background/Objectives: Horseshoe kidney is a congenital anomaly characterized by the fusion of the kidneys at the lower pole. Polycystic kidney disease with horseshoe kidney is called polycystic horseshoe kidney. Genetic testing is essential for the diagnosis of polycystic horseshoe kidney disease because it can result from a number of genetic disorders. Fewer than 20 cases of polycystic horseshoe kidney have been reported to date. However, polycystic horseshoe kidney disease was mostly diagnosed via autopsy or radiologic imaging techniques including computed tomography, magnetic resonance imaging, and angiography. Because polycystic kidney disease has various causes, genetic testing is essential for the diagnosis of autosomal dominant polycystic kidney disease (ADPKD) in patients with polycystic horseshoe kidney disease. At present, the diagnosis of ADPKD is made using genetic approaches, including next-generation sequencing. We reported a potentially pathogenic polycystin 1 (PKD1) gene in a patient with ADPKD and horseshoe kidney. Methods: We performed the sequencing of the PKD1 gene and radiological examinations (computed abdominal tomography). Results: Computed abdominal tomography revealed enlarged kidneys with multiple cysts fused at the lower poles, indicating polycystic HSK. The sequencing of the PKD1 gene revealed a heterozygous pathogenic variant c.165_171del (p.Leu56ArgfsTer15), which genetically confirmed the diagnosis of ADPKD. The patient was treated with an angiotensin II receptor blocker. Conclusions: In this case report, we suggest that genetic testing becomes the key approach to the diagnosis of ADPKD with horseshoe kidney. Additionally, this approach offers the benefit of avoiding the possibility of the condition being mistakenly diagnosed or diagnosed late due to its uncommon occurrence and nonspecific symptoms.

The significance of Itga8 and Vangl2 in kidney development: Insights from yotari mice

The permanent kidney develops from the metanephros through the interaction of the ureteric bud (UB) and metanephric mesenchyme (MM). Congenital anomalies of the kidney and urinary tract (CAKUT) are common prenatal diagnoses, and genetic factors play a critical role in their development. This study explores the involvement of Integrin alpha-8 (Itga8) and Van Gogh-like 2 (Vangl2) proteins in kidney development, using the yotari (yot) mouse model, which harbors a mutation in the Dab1 gene, disrupting Reelin signaling. Immunofluorescence was employed to analyze the spatiotemporal expression patterns of these proteins in embryonic and postnatal kidney samples. Our results show that Itga8 and Vangl2 expression is significantly higher in the embryonic kidneys of yot mice than those of wt mice. However, the two groups observed no significant differences in the temporal expression of these proteins in postnatal kidneys. Spatially, Itga8 was most strongly expressed in the metanephric mesenchyme and renal vesicles/immature glomeruli. At the same time, Vangl2 showed the highest expression in the metanephric mesenchyme, renal vesicles/immature glomeruli, and collecting ducts in yot mice. Our findings suggest that the Dab1 mutation disrupts the expression of Itga8 and Vangl2, contributing to kidney developmental defects associated with CAKUT phenotypesThis increased expression suggests a disruption in the normal regulation of these proteins, likely due to the Dab1 mutation, which impairs Reelin signaling. Still, the exact mechanism through which the Reelin/Dab1 pathway influences the expression of examined markers remains to be elucidated. These results offer valuable insights into the factors associated with kidney malformations and suggest potential therapeutic targets for CAKUT abnormalities.

Factors affecting the incidence of congenital anomaly of the kidney and urinary tract: A systematic review and meta-analysis

INTRODUCTION

Congenital anomaly of kidney and urinary tract (CAKUT) is one of the most common congenital anomalies, occurring in over 1 % of live births and accounting for 40-50 % of chronic kidney failure cases in children. The prevalence of CAKUT was multifaceted and varies widely. This study aimed to report the latest evidence of incidence, trends, and risk factors associated with the incidence of CAKUT.

EVIDENCE ACQUISITION

We conducted a systematic search of PubMed, ScienceDirect, Scopus, and Proquest databases. The included studies were then assessed using Newcastle-Ottawa (NOS) risk of bias tools. Meta-analysis was performed using Review Manager version 5.4.1 software and presented as pooled incidence and Odds Ratio (OR) with a 95 % confidence interval.

EVIDENCE SYNTHESIS

Eight studies in total were included from 2004 to 2022 (12.838 infants with CAKUT of all ages). NOS risk of bias tools indicated all studies had low risk of bias. The overall pooled incidence of CAKUT was 13,6 per 1000 births (95 % CI: 4 to 45,7 per 1000 births) in all infants and 4,9 per 1000 births (95 % CI: 1,1 to 21,3 per 1000 births) in term infants without congenital anomalies, with an increasing trend over the years. Factors, such as sex (boys) (OR = 1,53; 95 % CI 1,26-1,86), prematurity (OR = 1,46; 95 % CI 1,27-1,67), low birth weight (OR = 1,28; 95 % CI 1,10-1,48), maternal diabetes (OR = 1,81; 95 % CI 1,43-2,28), maternal obesity (OR = 1,45; 95 % CI 1,23-1,70), and maternal age (>40 years) were also found to be risk factors of CAKUT incidence. Furthermore, one study reported race (black people [OR = 0,89; 95 % CI 0,87-0,91] and Hispanics [OR = 1,22; 95 % CI 1,18-1,25]) to be a risk factor of CAKUT.

CONCLUSIONS

The incidence of CAKUT was high and showed an increasing trend over the years. Several risk factors, such as sex, prematurity, low birth weight, maternal diabetes, maternal obesity, maternal age and race were also found to be associated with CAKUT incidence. These findings should increase awareness regarding CAKUT incidence in at-risk populations.

Prenatal diagnosis and postnatal outcomes of congenital kidney and urinary tract anomalies: results from a tertiary center

BACKGROUND

This study aimed to investigate the prenatal features, genetic findings, and perinatal outcomes of fetuses with congenital anomalies of the kidney and urinary tract (CAKUT), with a particular focus on associations with additional structural or chromosomal abnormalities.

METHODS

A retrospective cohort analysis was conducted on 277 fetuses diagnosed with CAKUT between December 2020 and December 2024 at a tertiary center. Data on anomaly subtypes, associated findings, genetic testing, pregnancy outcomes, and postnatal follow-up were evaluated. Logistic regression was used to identify predictors of termination.

RESULTS

Urinary tract dilatation was the most frequent anomaly (28.2%), followed by multicystic dysplastic kidney (11.6%) and bilateral renal agenesis (11.2%). Extrarenal anomalies were present in 33.9% of fetuses, primarily involving the CNS. Genetic testing was performed in 48.4%; chromosomal abnormalities were found in 17.3%, most commonly trisomy 21 (5.8%). Termination was significantly associated with early diagnosis (adjusted OR = 0.82; p < 0.001), oligohydramnios (OR = 4.94; p < 0.001), CNS (OR = 3.74; p = 0.001), and cardiac anomalies (OR = 4.21; p = 0.002). Neonatal death occurred in 29.2% of cases, and mortality was higher in non-isolated anomalies (60% vs. 32.9%, p < 0.001).

CONCLUSIONS

Fetuses with CAKUT, particularly those with early diagnosis or coexisting anomalies, carry a higher risk of adverse outcomes. Prenatal detection, coupled with comprehensive genetic and structural evaluation, is essential for informed counseling and postnatal planning.

Analysis of Kallikrein 6, Acetyl-α-Tubulin, and Aquaporin 1 and 2 Expression Patterns During Normal Human Nephrogenesis and in Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

Background/Objectives: The human kallikrein-related peptidase 6 (KLK6), a serine protease with trypsin-like properties, belongs to the 15-member kallikrein (KLK) gene family and is predominantly recognized for its role in oncogenesis, neurodegenerative disorders, and skin conditions. Aquaporins (AQPs) are integral membrane proteins that facilitate water transport across cell membranes. AQP1 is constitutively active in the kidneys and plays a crucial role in reabsorbing filtered water, while AQP2 is regulated by vasopressin and is essential for maintaining body fluid homeostasis. The primary objective of the present study is to investigate the spatio-temporal expression patterns of KLK6, AQP1, and AQP2 throughout normal human nephrogenesis and congenital kidney and urinary tract (CAKUT) abnormalities: duplex kidneys, horseshoe kidneys, and dysplastic kidneys. Methods: An immunofluorescence analysis of KLK6, AQP1, and AQP2 was performed on 37 paraffin-embedded fetal kidney samples. The area percentage of KLK6 in the kidney cortex was calculated in normal developing samples during developmental phases 2, 3, and 4 and compared with CAKUT samples. Results: KLK6 exhibits distinct spatiotemporal expression patterns during human kidney development, with consistent localization in proximal tubules. Its subcellular positioning shifts from the basolateral cytoplasm in early phases to the apical cytoplasm in later stages, which may be strategically positioned to act on its substrate in either the peritubular space or the tubular fluid. KLK6 expression followed a quadratic trajectory, peaking at Ph4. This marked increase in the final developmental phase aligns with its strong expression in mature kidneys, suggesting a potential role in proximal tubule differentiation and functional maturation through facilitating extracellular matrix remodeling and activating proteinase-activated receptors, modulating the signaling pathways that are essential for tubular development. In duplex kidneys, structural abnormalities such as ureteral obstruction and hydronephrosis may upregulate KLK6 as part of a reparative response, while its downregulation could impair epithelial remodeling and cytoskeletal integrity, exacerbating dysplastic phenotypes. Conclusions: These findings highlight the potential of KLK6 involvement in normal kidney development and the pathology of CAKUT.

Kidney Transplantation in Congenital Abnormalities of Kidney and Urinary Tract (CAKUT)

Congenital anomalies of the kidney and urinary tract (CAKUT) are a common cause of chronic kidney disease in children. Most patients will reach end-stage renal function and dialysis or transplantation in childhood or early adulthood. Patients with CAKUT deserve a careful evaluation before a kidney transplant; detailed imaging and functional studies are necessary, particularly in the presence of lower urinary tract abnormalities, and surgical procedures are advisable in selected cases. A higher incidence of complications has been reported after a kidney transplant in CAKUT, mainly urinary tract infections. However, in the long term, the prognosis seems to be comparable to other kidney diseases. A large number of reports are available in the literature on medical and surgical management of patients with CAKUT before, during, and after a kidney transplant; almost all recommendations of surgical procedures before a kidney transplantation are based on retrospective not controlled studies or personal opinions; prospective controlled studies are needed. In this narrative, nonsystematic review, we report the results of recently published selected studies and underline questions that should be addressed in future guidelines.

Kidney development at a glance: metabolic regulation of renal progenitor cells

The aberrant regulation of renal progenitor cells during kidney development leads to congenital kidney anomalies and dysplasia. Recently, significant progress has been made in understanding the metabolic needs of renal progenitor cells during mammalian kidney development, with evidence indicating that multiple metabolic pathways play essential roles in determining the cell fates of distinct renal progenitor populations. This review summarizes recent findings and explores the prospects of integrating this novel information into current diagnostic and treatment strategies for renal diseases. Reciprocal interactions between various embryonic kidney progenitor populations establish the foundation for normal kidney organogenesis, with the three principal kidney structures-the nephrons, the collecting duct network, and the stroma-being generated by nephron progenitor cells, ureteric bud/collecting duct progenitor cells, and interstitial progenitor cells. While energy metabolism is well recognized for its importance in organism development, physiological function regulation, and responses to environmental stimuli, research has primarily focused on nephron progenitor metabolism, highlighting its role in maintaining self-renewal. In contrast, studies on the metabolic requirements of ureteric bud/collecting duct and stromal progenitors remain limited. Given the importance of interactions between progenitor populations during kidney development, further research into the metabolic regulation of self-renewal and differentiation in ureteric bud and stromal progenitor cells will be critical.