Reference values for urinary protein, albumin, beta 2-microglobulin, and the alpha 1-microglobulin-to-creatinine ratio in Japanese children.

BACKGROUND: The importance of the ratio of creatinine to urinary protein, albumin, and low-molecular weight protein as a urinary marker in chronic kidney disease patients is widely recognized. However, no reference values have hitherto been established for these markers in Japanese children. The present study aimed to establish the reference values for these urinary markers in Japanese children. METHODS: The first morning urine was randomly collected from 1712 pupils aged ≥ 3 to < 18 years during school and kindergarten mass urinary screenings. The upper limit of the reference values was set at the 97.5th percentile of the creatinine ratio per marker. RESULTS: The urinary protein-to-creatinine ratio (PCR), urinary albumin-to-creatinine ratio (ACR), urinary beta 2-microglobulin-to-creatinine ratio (BMCR), and urinary alpha 1-microglobulin-to-creatinine ratio (AMCR) showed an age-related decrease at the 50th percentile reflecting an age-related increase in urinary creatinine. The appropriate reference value for the PCR and ACR was 0.12 g/gCr and 35 mg/gCr, respectively, in the entire cohort. The appropriate reference value for the BMCR was 0.5 µg /mgCr for age ≥ 3 to < 6 years and 0.35 µg/mgCr for age 6 years or older. The appropriate reference value for the AMCR was 5.0 µg/mgCr for age ≥ 3 to < 6 years and 3.5 µg /mgCr for age 6 years or older. CONCLUSION: The present study was the first to determine appropriate reference values for the PCR, ACR, BMCR, and AMCR based on an analysis of the first morning urine samples of a large number of children.

Urine alpha 1-microglobulin-to-creatinine ratio and beta 2-microglobulin-to-creatinine ratio for detecting CAKUT with kidney dysfunction in children.

BACKGROUND: The leading cause of advanced chronic kidney disease (CKD) in children is congenital anomalies of the kidney and urinary tract (CAKUT). However, the most appropriate parameters of biochemical urine analysis for detecting CAKUT with kidney dysfunction are not known. METHODS: The present observational study analyzed data on children with CAKUT (stage 2-4 CKD) and the general pediatric population obtained from school urine screenings. The sensitivity and specificity of urine alpha 1-microglobulin-, beta 2-microglobulin-, protein-, and the albumin-to-creatinine ratios (AMCR, BMCR, PCR, ACR, respectively) in detecting CAKUT with kidney dysfunction were compared with those of the conventional urine dipstick, and the most appropriate of these four parameters were evaluated. RESULTS: In total, 77 children with CAKUT and 1712 subjects in the general pediatric population fulfilled the eligibility criteria. Conventional dipstick urinalysis was insufficient due to its low sensitivity; even when the threshold of proteinuria was +/-, its sensitivity was only 29.7% for stage 2 and 44.1% for stage 3 CKD. Among the four parameters assessed, the AMCR and BMCR were adequate for detecting CAKUT in children with stage 3-4 CKD (the respective sensitivity and specificity of the AMCR for detecting CAKUT in stage 3 CKD was 79.4% and 97.5% while that of BMCR was 82.4% and 97.5%). These data were validated using national cohort data. CONCLUSION: AMCR and BMCR are superior to dipstick urinalysis, PCR, and ACR in detecting CAKUT with kidney dysfunction, particularly stage 3 CKD. However, for AMCR, external validation is required. A higher resolution version of the Graphical abstract is available as Supplementary information.

Long-term morbidity of IgA nephropathy in children evaluated with newly proposed remission criteria in Japan.

BACKGROUND: The long-term outcome of pediatric IgA nephropathy (IgAN) is unclear. Objective IgAN remission criteria were proposed by the Japanese Society of Nephrology in 2013. METHODS: Children with newly developed IgAN followed for >5 years were analyzed. They were divided into two groups based on histological findings at initial kidney biopsy: the focal mesangial proliferation group (Focal group) and diffuse mesangial proliferation group (Diffuse group). The primary outcome was the remission rate according to the newly proposed IgAN remission criteria. RESULTS: The patients comprised 53 children (31 boys; mean age at IgAN onset, 10.0 years). The Focal and Diffuse groups comprised 21 and 32 patients, respectively. No significant differences in patient characteristics were found between the groups except for steroid administration. The median follow-up period from onset was 9.9 years. Sixteen patients in the Diffuse group and 10 in the Focal group had not achieved remission at the last observation. Patient conditions 2 years after the initial treatment were almost identical to those at the last observation. Multivariate analysis revealed that proteinuria, particularly <0.5 g/g Cr at 2 years, was significantly associated with remission at the last observation regardless of proteinuria status at the start of treatment. CONCLUSIONS: Pediatric IgAN has a prolonged course that is longer than expected regardless of severity at diagnosis. Patient conditions 2 years after initial treatment predicted their conditions at the last observation. Although the final renal function of these patients is presently unclear, children with IgAN should be followed beyond adolescence and further into adulthood.

Renovascular hypertension due to bilateral renal artery stenosis treated with stent implantation in a 12-year old girl.

Renovascular hypertension (RVH) in children is a relatively rare disease, but it is important in that it is a treatable condition when properly diagnosed. Percutaneous transluminal renal angioplasty (PTRA) with or without stenting is widely applied to adult patients with RVH. However, limited information is available as to PTRA with stenting in pediatric patients. We experienced a case of RVH in a 12-year-old girl, who had severe hypertension (180/110 mmHg). Bilateral renal artery stenosis was demonstrated by 3D-CT, MR angiography and selective renal arteriography. Renal function and plasma renin activity were normal. Angiotensin blockade was refrained for fear of functional deterioration of the kidney. Medical treatment with amlodipine insufficiently lowered the pressure to 140-160/80-100 mmHg, so we performed PTRA. Stenotic lesion and pressure gradient was still present after balloon angioplasty on both sides, prompting us to place LUMINEXX® stents on both renal arteries. Blood pressure dropped dramatically after the intervention. Amlodipine was discontinued, and then, enalapril and warfarin were administered to prevent neointima and thrombus formation. Her blood pressure and renal function was stable 18 months after PTRA. Oversized self-expanding stent such as LUMINEXX® stent could be used for renal artery stenting even in pediatric patients with RVH.

C1q nephropathy in a 2-year-old boy presenting with steroid resistant nephrotic syndrome.

We experienced a case of a 2-year-old boy, who presented with steroid resistant nephrotic syndrome, which developed insidiously. Renal biopsy revealed that he had focal and segmental glomerulosclerosis on light microscopy, dominant mesangial deposition of C1q by immunofluorescent staining, and electron dense deposits on electron microscopy, which are all compatible with C1q nephropathy. He had no clinical sign of any collagen diseases, including systemic lupus erythematodes. So, the diagnosis of C1q nephropathy was made. An intensive treatment by a combination of cyclosporine, prednisolone and methylprednisolone pulse therapy was successful in achieving remission and disappearance of proteinuria in this patient. Although he developed hypertension requiring calcium blocker and angiotensin converting enzyme inhibitor, his renal function stayed within normal limit for 3 years after the initiation of the treatment. The growth was well preserved during the 3 years of treatment with almost unchanged SD scores for height. He has delay in speech, which may not be associated with the etiology of his nephropathy, based on the absence of such association in the previous reports. C1q nephropathy is still a controversial clinical entity, so accumulation of the cases may help further understand the pathogenesis and clinical manifestation of C1q nephropathy.