Asymptomatic constant isolated proteinuria in children

Clinical, pathological, and genetic characteristics of cases with asymptomatic proteinuria not manifesting nephrotic syndrome at onset: a single-center retrospective study

BACKGROUND

Cases with asymptomatic proteinuria (ASP) not manifesting nephrotic syndrome often pathologically show focal segmental glomerulosclerosis (FSGS). However, characteristics of those cases had not been intensively studied so far.

METHODS

We retrospectively reviewed clinical, pathological, and genetic characteristics of 37 children (median age, 9.3 years) who underwent renal biopsy for persistent isolated proteinuria (urine protein-to-creatinine ratio: UP/C, > 0.2 g/g) between 2003 and 2019. Targeted next-generation sequencing (NGS) was utilized for all patients with FSGS, excluding those with secondary FSGS.

RESULTS

At biopsy, all patients with FSGS (N = 14) had UP/C ≥ 0.5 g/g and the median UP/C was significantly higher in those with FSGS than those with minor glomerular abnormalities (MGA) (N = 23) (1.49 vs. 0.53 g/g, P < 0.001). Causative variants were found in seven patients with FSGS (TRPC6, WT1, ACTN4, and INF2 in 3, 2, 1, and 1 patient, respectively): all gene variants were in genes manifesting autosomal dominant inheritance mode. The proportion of the perihilar variant was significantly higher in the genetic FSGS patients than in the non-genetic FSGS patients (4/7 vs. 0/7, P < 0.05). Kaplan-Meier analysis showed that the renal survival rate after ASP diagnosis was significantly lower in the genetic FSGS patients than in the non-genetic FSGS and the MGA patients (P < 0.001).

CONCLUSIONS

UP/C was a simple and useful predictive parameter for the diagnosis of FSGS. APS without nephrotic syndrome at onset may be associated with autosomal dominant causes of FSGS, especially in those with the perihilar variant.

Proteinuria in Children

Although the American Academy of Pediatrics (AAP) removed the screening urinalysis from its health supervision guidelines in 2007, the use of the urinalysis remains an important part of pediatric care. Thus, the incidental finding of proteinuria is still commonplace when a urine sample is collected for various complaints, such as fever and abdominal pain. Knowing when to reassure a patient with proteinuria versus when to perform additional testing is a situation that general practitioners face regularly, but also one that not all may be comfortable dealing with due to the possibility of missing a diagnosis. In addition, proteinuria in certain conditions can signify renal disease and worse outcomes, so general practitioners should know how to screen and interpret the results. Understanding the common benign and pathological causes of proteinuria helps medical providers to better inform and treat their patients, and possibly avoid unnecessary additional testing or subspecialty referrals. [Pediatr Ann. 2020;49(6):e268-e272.].

Benefits of incorporating urinary protein/creatinine ratio measurement in a school urine screening system: The experience of restructuring the school urinary screening system in Osaka Prefecture, Japan

AIM

School urine screening has been established in several countries of Asia, including Japan, Korea and Taiwan. In Osaka prefectural schools, the urine screening system had some problematic issues including an unclear referral procedure for students with abnormal urinary findings. Therefore, the school urine screening system was reviewed and restructured in 2004. The aim of this study was to assess the improvement in school urine screening through evaluation of the restructured Osaka prefectural school urinary screening system.

METHODS

The Osaka prefectural school urinary screening system was reviewed, mainly considering two points. One was the incorporation of standard urinary protein/creatinine ratio measurement instead of the traditional urine dipstick and urine sediment tests; the second point was that all students requiring further examination were referred to regional nephrologists.

RESULTS

After restructuring, the number of students who were referred to a medical institute for detailed examinations decreased to 10%, although the number of students newly diagnosed with kidney disease and the types of diagnosis did not change. The positive predictive value of screening increased to about 8 times the value before the system restructuring. The reductions enabled students who required further examination to be referred to regional nephrologists and has contributed to a decreased cost for these examinations.

CONCLUSION

Incorporating urinary protein/creatinine ratio measurement into the school urinary screening system, and updating the guiding principles, including referral to nephrology specialists, has enabled the school urinary screening system in Osaka Prefecture to become more efficient and have better cost performance.

Renal biopsy criterion in children with asymptomatic constant isolated proteinuria

BACKGROUND

The criterion of a renal biopsy in children with asymptomatic persistent isolated proteinuria is controversial.

METHODS

To determine an adequate renal biopsy criterion in children with asymptomatic constant isolated proteinuria, the optimal cutoff maximum urinary protein/creatinine ratio (uP/Cr) to separate minor glomerular abnormalities (MGA) and other significant glomerular changes was obtained by receiver operating characteristic analysis in 44 children with asymptomatic constant isolated proteinuria (uP/Cr ≥ 0.2 g/g) screened from 1167 patients who underwent a renal biopsy between September 2000 and April 2010. Patients were divided into two groups according to the cutoff value to verify its validity.

RESULTS

The optimal uP/Cr was 0.5 g/g. In Group 1 (uP/Cr <0.5 g/g, n = 15), only one patient (6.7%) showed focal segmental glomerulosclerosis (FSGS) and the other 14 patients (93.3%) had MGA. In Group 2 (uP/Cr ≥ 0.5 g/g at least once before biopsy, n = 29), 5 patients showed FSGS and 7 patients had nephritis such as IgA nephropathy (41.4%, n = 12) and the other 17 patients (58.6%) showed MGA. These findings indicated that the ratio of non-MGA/MGA was significantly higher in Group 2 than that in Group 1 (P = 0.016) and that if renal biopsies were performed with a criterion of a maximum uP/Cr ≥ 0.5 g/g (criterion for Group 2), renal biopsies could be avoided in 45.2% of patients with MGA. One patient with FSGS in Group 1 showed proteinuria with uP/Cr ≥ 0.5 g/g in the clinical course.

CONCLUSIONS

An adequate renal biopsy criterion in children with asymptomatic constant isolated proteinuria is uP/Cr ≥ 0.5 g/g.

End-stage kidney at the onset of nephrotic syndrome in a 4-year-old girl

A previously healthy Japanese girl aged 4 years suddenly developed idiopathic nephrotic syndrome (INS) associated with acute renal failure (ARF). Despite prompt initiation of hemodialysis and prednisolone treatment, her ARF did not recover. A percutaneous renal biopsy performed within a month from the onset of INS revealed lesions of end-stage kidney, which is unusual for the acute stage of INS. Although the etiology of her ARF remains speculative, an acute exacerbation of an underlying chronic disease, such as non-nephrotic focal segmental glomerulosclerosis might be the cause.

Isolated asymptomatic proteinuria

Proteinuria is occasionally detected on "routine" examination (not done for a suspected renal or urinary tract problem) and often presents a diagnostic problem. Even mild proteinuria is abnormal and needs an explanation. Its degree and persistence should be ascertained and associated hematuria looked for. Nonpathological (including orthostatic) proteinuria and renal tubular disorders should be excluded. Persistent proteinuria is mostly due to a primary or secondary (eg hepatitis B) glomerular condition, which requires expert evaluation of renal biopsy. Aggressive therapy may be needed in some cases. The intensity of proteinuria can be decreased with ACE inhibitors. Long-term observation is essential.

Focal segmental glomerulosclerosis: unremitting proteinuria of long duration as a possible etiology?

A Japanese boy aged 9 years referred to our hospital because of steroid-resistant proteinuria. He had a 6-year history of unremitting proteinuria and was diagnosed as having minimal-change disease (MCD) by the repeated renal biopsies performed at the age of 3.5 years and 8.5 years, respectively. His proteinuria fluctuated ranging from 115 mg/100 ml to 645 mg/100 ml, and serum total protein ranged from 59 g/liter to 63 g/liter. The third renal biopsy at the presentation also revealed MCD. Thereafter he was treated with an anti-thrombocyte agent combined with an angiotensin converting enzyme inhibitor. Despite unremitting proteinuria of long duration, he did not have any complaints. At the age of 11.5 years, severe tubulointerstitial lesion was observed in the fourth renal biopsy. The fifth renal biopsy 6 months after the fourth finally revealed the lesion of focal segmental glomerulosclerosis (FSGS). Although the interpretation of his repeated renal biopsies were considered to be limited, these clinical observation suggested that his unremitting proteinuria of long duration might have been attributed to subsequent progression FSGS.

Proteinuria: potential causes and approach to evaluation

Proteinuria may be associated with a renal or systemic disease, or it may be isolated. The latter occurs in asymptomatic patients without evidence of any disease or abnormality of the urine sediment. Isolated proteinuria may be subdivided into two broad groups: (1) benign forms, with a favorable-to-excellent prognosis and (2) persistent forms, some of which have a worrisome prognosis. Functional proteinuria may occur in disorders with altered renal hemodynamics, usually resolves, and is not associated with progressive renal disease. Idiopathic transient proteinuria is typically discovered on routine screening and usually disappears on subsequent testing. In idiopathic intermittent proteinuria, a significant number (50%) of urine samples exhibit abnormal rates of protein excretion. Although structural abnormalities may be observed on renal biopsy, progressive renal insufficiency is unusual. In orthostatic proteinuria, the rate of protein excretion completely normalizes in the recumbent position. Long-term studies show this to be a benign condition. In persistent isolated proteinuria, at least 80% of random urine samples exhibit abnormal protein excretion. This represents a heterogeneous group, but a significant proportion of these patients have prominent renal pathologic findings and progress to serious renal disease. Proteinuria with significant renal disease may be non-nephrotic or nephrotic range. The former does not exclude glomerular disease, but tubulointerstitial or vascular disorders are also likely when proteinuria is less than 2 g/24 hours. Patients with nephrotic-range proteinuria generally have a glomerular disorder. Distinction between benign and more ominous forms of proteinuria requires careful evaluation.

Acute glomerulonephritis superimposed on focal segmental glomerulosclerosis: a case report

A 9-year-old boy was referred to our hospital because of significant hematuria and proteinuria associated with hypocomplementemia. Although he had had a 3-year history of asymptomatic persistent proteinuria detected by urine screening of school children, he did not visit a physician. Finally, he visited a regional hospital, and hypocomplementemia was noted there. A percutaneous renal biopsy performed hospital day 4 revealed diffuse endocapillary proliferative glomerulonephritis with severe tubulointerstitial changes. Although his hematuria and hypocomplementemia spontaneously subsided within a month, proteinuria remained. A renal biopsy performed 4 months after the first renal biopsy revealed the lesion suggesting advanced focal segmental glomerulosclerosis (FSGS). Despite corticosteroid treatment, his proteinuria persisted, and he developed end stage renal failure. These clinical observation indicated that he had acute glomerulonephritis (AGN) superimposed on non-nephrotic FSGS, and that the episode of AGN might cause exacerbation of the FSGS.

Evaluating the child with proteinuria

Proteinuria is a common laboratory finding in children. It might represent a benign condition or herald the presence of a serious underlying renal disease or systemic disorder. Investigation to confirm a diagnosis or seek reassurance is important. This paper discusses the various causes of proteinuria, and those aspects of the history, physical examination, and the laboratory tests that will help determine the cause or reassure that a serious problem is not currently present.

Evaluation of hematuria, proteinuria, and hypertension in adolescents

Signs or symptoms of renal disease in adolescents deserve prompt attention and appropriate evaluation. Adolescents are susceptible to a variety of urinary tract disorders. The key issue in the evaluation of hematuria or proteinuria in adolescents is the existence of concomitant signs of renal disease. For isolated hematuria or proteinuria, demonstration of persistence and a reasoned evaluation are in order. Hypertension in adolescents must be carefully documented and, when present, considered seriously. The fact that most teens with persistent elevated blood pressures have essential hypertension is still a great concern because for most of these adolescents the hypertension will be lifelong and, if left untreated, can be associated with significant morbidity and mortality in the adult years.

Long-term prognosis and prognostic factors of Japanese children with mesangial proliferative glomerulonephritis without IgA deposition

Mesangial proliferative glomerulonephritis without IgA deposition (non-IgA MesPGN) is commonly detected in biopsy specimens, but the clinicopathological correlation with the long-term prognosis still remains obscure. The aim of our study is to elucidate the long-term prognosis and the clinicopathological prognostic factors in patients with non-IgA MesPGN. We mailed questionnaires to 122 patients with primary glomerulonephritis who were biopsied between 1963 and 1975. Information was obtained from 109 of these 122 patients and 55 were histologically rediagnosed as having non-IgA MesPGN. The histological alterations of glomeruli and tubulointerstitium were classified into five grades. The mean period between the biopsy and the questionnaires was 20.5 years. Six of the 55 patients with non-IgA MesPGN developed end-stage renal failure and histopathological alterations of renal biopsies from these six patients were classified into grade IV or V. The presence of hypertension, heavy proteinuria of over 2+ or renal insufficiency at the biopsy was related to the severe histological changes, a grade of IV or V and to a poor prognosis. The renal survival rate of all the 55 patients was 88.3% at 20 years after the biopsy, while that of the 12 patients with severe histological changes was 48.6%. Although non-IgA MesPGN is considered to be a heterogeneous disease, we cannot ignore the incidence of this disease and thus consider it to be one of the important primary glomerulonephritides that occur in childhood.

Isolated proteinuria in children. Natural history and indications for renal biopsy

The significance of isolated proteinuria in pediatric patients is uncertain. Therefore, we retrospectively studied all children evaluated for this urinary abnormality during the 6-year period from 1986 to 1992. Thirty-one patients (19 males), age 2 to 20 years, were identified as having isolated proteinuria that had persisted for a mean interval of 9.6 +/- 1.9 (SEM) months. The diagnosis was based upon the presence of a urine protein:creatinine ratio > 0.2 in an early-morning specimen. None of the patients had hematuria, edema, or azotemia. Seventeen children underwent a renal biopsy. There was no difference between the patients who were biopsied and those who were not with respect to age, magnitude of proteinuria, glomerular filtration rate (GFR), or serum albumin and cholesterol concentrations. The renal histopathology revealed focal segmental glomerulosclerosis (FSGS) (n = 8), membranous nephropathy (n = 1), postinfectious nephritis (n = 2), focal global glomerulosclerosis (FGGS) (n = 1), and normal kidney tissue (n = 5). Twelve of the patients who did not undergo a kidney biopsy and four of the five children with a normal renal biopsy were followed for at least 12 months; there was complete resolution of the proteinuria in 11 (69%) of these patients. The level of proteinuria did not predict the presence or absence of important kidney disease. However, if isolated proteinuria persists for more than 1 year, it is then unlikely to spontaneously remit and a renal biopsy is indicated to clarify the nature of any underlying glomerulopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal biopsy in children with asymptomatic hematuria or proteinuria: survey of pediatric nephrologists

The decision to perform a renal biopsy on children with asymptomatic hematuria or proteinuria remains a problem for clinicians. To assess the current opinion of 349 pediatric nephrologists on this issue, case summaries of a 9-year-old boy with 20 urinary red blood cells per high power field without proteinuria and a 9-year-old boy with 2+ proteinuria (600 mg/day) without hematuria were distributed to each specialist. Seventy-three percent (n = 256; 3:1, male:female) responded. Five percent would biopsy the child with asymptomatic hematuria. The main reasons were academic interest, parental pressure for a diagnosis/prognosis and concern for future economic impact on the child (i.e., life insurance). The determinations to biopsy for hematuria were not related to age or sex of the nephrologist. In contrast, 38% (n = 96) of the pediatric nephrologists would perform a biopsy on the child with proteinuria. The major reasons for biopsy were academic interest and potential for drug therapy. With a normal history, physical examination and laboratory/radiographic evaluation, the vast majority of pediatric nephrologists in North America support a conservative approach to the child with asymptomatic hematuria or proteinuria.