Renal function in congenital anomalies of the kidney and urinary tract

Renal morphology and function from childhood to adulthood in Turner syndrome

BACKGROUND

Turner syndrome (TS) is a chromosomal disorder with various complications, including congenital anomaly of the kidney and urinary tract (CAKUT). However, its renal function remains poorly known. Therefore, this study aimed to evaluate renal function in TS of various ages from childhood to adulthood.

METHODS

We retrospectively analyzed 63 patients with TS who visited our hospital between 1989 and 2020, examined their renal morphology, and analyzed renal function by calculating the estimated glomerular filtration rate (eGFR) using formulas applicable for Japanese populations.

RESULTS

Renal morphological abnormality was observed in 22 cases (35.0%) (horseshoe kidney, 7 [11.1%]; hydronephrosis, 11 [17.5%]; duplex collecting system, 3 [4.8%]; and single unilateral kidney, 1 [1.6%]). We evaluated the eGFR of 47 subjects aged 2.8-39.3 years and classified them into Group 1 (with CAKUT, n = 15) and Group 2 (without CAKUT, n = 32). The eGFR at the first visit and the final follow-up was not statistically different between these groups. In Group 1 with CAKUT, the eGFR was not significantly different between that at the first visit and that at the final follow-up (p = 0.21). During the observation period (median, 7.9 years), the eGFR of all individuals in both groups gradually decreased with age, but did not fall < 60 mL/min/1.73 m², which defines chronic kidney disease (CKD).

CONCLUSIONS

The renal function of TS remained normal in all cases during our investigation period, and no one developed CKD by the age of 40 years.

Retrospective study of the renal function using estimated glomerular filtration rate and congenital anomalies of the kidney-urinary tract in pediatric Turner syndrome

Although Turner syndrome (TS) is frequently associated with congenital anomalies of the kidney-urinary tract (CAKUT), which is a major cause of pediatric chronic kidney disease, renal function in TS is usually considered normal. The present study aimed to analyze the frequency of renal dysfunction and CAKUT in pediatric patients with TS. Our study included 122 patients with TS between the ages of 2 and 18 years from 30 hospitals across Japan. Clinical data related to renal function and CAKUT were retrospectively collected. The estimated glomerular filtration rate (eGFR) was calculated using the serum creatinine-based formula recommended by the Japanese Society for Pediatric Nephrology. An eGFR <90 mL/min/1.73 m² for two consecutive years was defined as renal dysfunction. Fifteen (13.5%) of 122 patients had CAKUT, and four patients had renal dysfunction (3.2%, 95% confidence interval: 0%-6.7%). Three of the four did not have CAKUT. Of the CAKUT manifestations, horseshoe kidney, renal hypodysplasia, and multicystic dysplastic kidney were seen in nine, two, and one patient, respectively. Eight of the nine patients with horseshoe kidney had a normal renal function; however, the remaining patient with renal hypodysplasia had renal dysfunction. A small percentage of patients with pediatric TS may had an eGFR below 90 mL/min/1.73 m² which was not necessarily associated with CAKUT.

Evaluation of Renal Function in Children with Congenital Scoliosis and Congenital Anomalies of the Kidney and Urinary Tract

Background

The aim of this study was to compare renal function in children with congenital scoliosis and congenital anomalies of the kidney and urinary tract, with healthy children.

Material/Methods

Biochemical tests were performed before surgery (pre-therapy) and after surgery (post-therapy) in 16 children with congenital scoliosis and congenital anomalies of the kidney and urinary tract. Thirty-two healthy children were matched for age, sex, and weight (healthy controls). General renal function tests included serum electrolytes, creatinine, urea, cystatin C, and estimated glomerular filtration rate (eGFR). Tests for early renal changes included N-acetyl-beta-D-glucosaminidase (NAG), urine microalbumin, serum transferrin, immunoglobulin G (IgG), urinary alpha-1-microglobulin (A1M), and beta-2-microglobulin (B2M).

Results

Sixteen patients with congenital anomalies of the kidney and urinary tract included eight boys (mean age, 11.38±2.00 years) and eight girls (mean age, 11.00±2.78 years). There were no significant differences in renal function between the pre-therapy and post-therapy groups (P>0.05), or between the three groups (pre-therapy, post-therapy, and healthy controls). In the pre-therapy group, there were significant differences in IgG, A1M, NAG, and serum phosphate levels between boys and girls, urine microalbumin was significantly increased in girls, but not boys (P<0.05). There were no significant differences between the pre-therapy group and post-therapy group (P>0.05).

Conclusions

Routine tests of renal function were normal in children with congenital scoliosis and congenital anomalies of the kidney and urinary tract, but early changes in renal function occurred before surgical treatment, indicating long-term follow-up of renal function is recommended.

Severe antenatally diagnosed renal disorders: background, prognosis and practical approach

Nowadays most renal disorders, especially urinary tract malformations and renal cystic disease, are diagnosed antenatally. In cases of severe bilateral disease, intrauterine renal dysfunction may lead to renal oligohydramnios (ROH), resulting in pulmonary hypoplasia which affects perinatal mortality and morbidity as well as the long-term outcome. However, some infants may only have mild pulmonary and renal disease, and advances in postnatal and dialysis treatment have resulted in improved short- and long-term outcome even in those infants with severe ROH. Here, we review the current state of knowledge and clinical experience of patients presenting antenatally with severe bilateral renal disorders and ROH. By addressing underlying mechanisms, intrauterine tools of diagnosis and treatment as well as published outcome data, we hope to improve antenatal counselling and postnatal care. KEY SUMMARY POINTS: 1. Nowadays most renal disorders are diagnosed antenatally, especially urinary tract malformations and renal cystic disease. 2. Severe kidney dysfunction may lead to renal oligohydramnios, which can cause pulmonary hypoplasia and is a risk factor of perinatal mortality and postnatal renal outcome. However, as considerable clinical heterogeneity is present, outcome predictions need to be treated with caution. 3. Advances in postnatal and dialysis treatment have resulted in improved short- and long-term outcomes even in infants with severe renal oligohydramnios. 4. A multidisciplinary approach with specialist input is required when counselling a family with an ROH-affected fetus as the decision-making process is very challenging.

Factors associated with a vicious cycle involving a low nephron number, hypertension and chronic kidney disease

It has been reported that there is substantial variation in the nephron number between individuals. Previous studies using autopsy kidneys have demonstrated that a low nephron number, in relation to a low birth weight, may result in hypertension (HTN) and/or chronic kidney disease (CKD). However, recent studies have revealed that the association between a low nephron number and HTN is not a universal finding. This observation indicates that a low nephron number is unlikely to be the sole factor contributing to an elevated blood pressure. In addition to the nephron number, various genetic and congenital factors may contribute to increased susceptibility to HTN and/or CKD in a complex manner. Acquired factors, including aging, obesity and related metabolic abnormalities, and various causes of renal injury, may additionally promote further nephron loss. Such a vicious cycle may induce HTN and/or CKD via the common mechanisms of renal hemodynamic maladaptation.

Effect of fetal and child health on kidney development and long-term risk of hypertension and kidney disease

Developmental programming of non-communicable diseases is now an established paradigm. With respect to hypertension and chronic kidney disease, adverse events experienced in utero can affect development of the fetal kidney and reduce final nephron number. Low birthweight and prematurity are the most consistent clinical surrogates for a low nephron number and are associated with increased risk of hypertension, proteinuria, and kidney disease in later life. Rapid weight gain in childhood or adolescence further compounds these risks. Low birthweight, prematurity, and rapid childhood weight gain should alert clinicians to an individual's lifelong risk of hypertension and kidney disease, prompting education to minimise additional risk factors and ensuring follow-up. Birthweight and prematurity are affected substantially by maternal nutrition and health during pregnancy. Optimisation of maternal health and early childhood nutrition could, therefore, attenuate this programming cycle and reduce the global burden of hypertension and kidney disease in the future.

Renal function and injury in infants and young children with congenital heart disease

BACKGROUND

The aim of this study was to investigate renal function and injury in infants and young children with congenital heart disease (CHD).

METHODS

We prospectively enrolled 58 CHD children aged ≤3 years and 20 age-matched controls and divided these into four groups: Group I, acyanotic CHD (n = 24); Group II, cyanotic CHD with arterial oxygen saturation of >75 % (n = 20); Group III, cyanotic CHD with arterial oxygen saturation of ≤75 % (n = 14); Group IV, normal controls (n = 20). Urinary levels of microalbumin (MA), N-acetyl-ß-D-glucosaminidase (NAG), and α1-microglobulin (α1-MG) corrected by creatinine (UCr) were compared.

RESULTS

Children with CHD had elevated urinary α1-MG/UCr levels, with Group III children having the highest level. Groups I and III children had higher urinary NAG/UCr levels than those of Groups II and IV. Urinary MA/UCr levels in the three patient groups were comparable and significantly higher than that in the control group. A α1-MG × 100/ (α1-MG + MA) of <15 %, indicative of glomerular damage, was present in two patients in Group I and one in Group III, but none in Group II.

CONCLUSIONS

Tubular injury can occur in CHD patients during infancy and early childhood. Among our patient cohort, it was most prominent in children with severe cyanosis. Glomerular injury was detected in some individuals with advanced heart failure or severe cyanosis.

Misexpression of Six2 is associated with heritable frontonasal dysplasia and renal hypoplasia in 3H1 Br mice

A radiation-induced mouse mutant, Brachyrrhine (Br), exhibits frontonasal dysplasia and renal hypoplasia, two malformations associated with deficiencies in mesenchymal condensation. The purpose of this study was to resolve the Br locus, evaluate possible candidate genes, and identify developmental defects in the mutant chondrocranium. Linkage analysis mapped the Br mutation to a critical region distal to D17Mit76, which contains only one gene, the transcription factor Six2. Sequence analysis of the Six2 gene, including 1.5 kb of the promoter, failed to reveal the Br mutation. However, homozygous Br/Br embryos showed almost complete absence of Six2 mRNA and protein in craniofacial and renal tissues while heterozygous Br/+ embryos displayed intermediate Six2 levels. Mutant embryos displayed malformations of neural crest-derived structures of the anterior cranium where Six2 is normally expressed. These data suggest a mutation in a novel cis-acting regulatory region inhibits Six2 expression and is associated with frontonasal dysplasia and renal hypoplasia.

Prognosis of antenatally diagnosed oligohydramnios of renal origin

Although clinical outcome data on fetuses with oligohydramnios of renal origin are scarce, prognosis is regarded as poor due to a high risk of renal dysfunction and pulmonary hypoplasia. This review aims to summarize the current knowledge and clinical experience with patients presenting antenatally with renal oligohydramnios. By reviewing the underlying mechanisms, complications, and outcome data, we hope to further improve antenatal counseling and postnatal care. We conclude that prognosis of ROH has changed in recent years. While early data before the introduction of sophisticated neonatal intensive care and renal replacement therapy indicated a poor prognosis, nowadays, a much more optimistic prognosis of children after renal oligohydramnios can be expected from the recent publications in the literature.