Post-streptococcal acute glomerulonephritis in children: Association between proteinuria levels and renal outcomes.

Background: Post-streptococcal acute glomerular nephritis (PSAGN) is mostly a benign condition. The usual sequelae of PSAGN include hypertension, its complications, and acute kidney injury. Severe PSAGN is associated with significant long-term morbidity, and histological abnormalities such as crescentic glomerulonephritis are infrequently reported. PSAGN has also been linked to late-onset chronic kidney disease in some populations due to high levels of proteinuria.

Aim: To evaluate the association between proteinuria levels and renal outcomes in children with PSAGN.

Methods: This prospective observational study was conducted at Lady Ridgeway Hospital (Colombo, Sri Lanka) over 15 months. Children with PSAGN were enrolled based on clinical and laboratory criteria. Persistent proteinuria ≥ 2+ for 2 weeks and serum creatinine > 100 μmol/L warranted renal biopsy, assessed via light microscopy and immunofluorescence. Normalization of complement 3 (C3) within 6 to 8 weeks was required for inclusion. Data on clinical features, urine protein levels, and renal function were collected from patient records, and potential associations were analysed using Statistical Package for the Social Sciences and R language for statistical computing. Ethical approval was obtained from the Ethical Review Committee, Lady Ridgeway Hospital for Children (Ref No: LRH/ERC/2021/60).

Results: Forty-four patients were recruited. There were 27 (61.4%) male patients and 17 (38.6%) female patients. Thirty-seven (84%) of them were above 5 years of age. Twenty (45%) patients had a history of skin sepsis, and eighteen (41%) had a history of throat infection. Among patients with proteinuria ≥ 2+, 53% had serum creatinine > 100 µmol/L, while among those with proteinuria < 2+, 7% had serum creatinine > 100 µmol/L. The association of high-degree proteinuria with elevated serum creatinine was significant (χ² = 7.8, P = 0.005) in PSAGN. The odds ratio of the logistic regression model was 1.049 (95% confidence interval: 1.003-1.098), indicating a positive direction with statistically significant association (P = 0.037). There was no significant association between proteinuria and the degree of hypertension or estimated creatinine clearance. Ten children underwent renal biopsy. Crescents (less than 50%) were demonstrated in five children, while three children had typical diffuse proliferative glomerulonephritis. One child had severe acute tubular necrosis, and another had crescentic glomerulonephritis (crescents > 50%). The immunofluorescence studies revealed deposition of immunoglobulin G and C3 in all biopsy specimens.

Conclusion: High-degree proteinuria was significantly associated with elevated serum creatinine (> 100 μmol/L) in children with PSAGN. The majority of children with persistent proteinuria ≥ 2+ for more than 2 weeks and the highest recorded serum creatinine > 100 μmol/L had atypical renal histological findings.