Age-related clinical risk patterns of acute kidney injury and tubular injury in adults with minimal change disease: a retrospective cohort study

Adult patients with minimal change disease (MCD), particularly older individuals, may experience acute kidney injury (AKI), tubular injury, and infectious complications. However, the clinical patterns associated with these complications remain incompletely understood. This study aimed to characterize age-related clinical features and the associations of selected clinical variables with renal and infectious complications in adults with biopsy-proven primary MCD. We retrospectively analyzed 225 adults with biopsy-proven primary MCD and classified them into patients aged 18–59 years and those aged ≥ 60 years. Clinical characteristics, renal outcomes, infection status, treatment exposure, and medication exposure were extracted from electronic medical records. Multivariable logistic regression models incorporating restricted cubic splines (RCS) were used to evaluate potential nonlinear associations. The UA–AKI model was adjusted for age, sex, hematuria, diabetes mellitus, systolic blood pressure, and 24-hour urinary protein. The age–tubular injury model was adjusted for serum uric acid, sex, hematuria, diabetes mellitus, systolic blood pressure, and 24-hour urinary protein. Serum albumin and documented CKD history were included in sensitivity analyses where appropriate. Compared with patients aged 18–59 years, those aged ≥ 60 years had higher rates of AKI (44.1% vs. 22.7%, P = 0.001), pathology-reported tubular injury (36.6% vs. 17.4%, P = 0.002), and clinically documented infection (40.9% vs. 21.2%, P = 0.002). RCS analyses showed that admission serum uric acid was significantly and nonlinearly associated with AKI ( P overall < 0.001; P nonlinear = 0.004). This association remained robust after additional adjustment for serum albumin and documented CKD history ( P overall < 0.001; P nonlinear = 0.006). Age was significantly associated with pathology-reported tubular injury ( P overall = 0.021), without evidence of significant nonlinearity ( P nonlinear = 0.253). The age–tubular injury association remained significant after additional adjustment for documented CKD history and after further adjustment for both serum albumin and documented CKD history. Older patients also had higher serum IgG levels than younger patients, including within infection-stratified subgroups. In adults with biopsy-proven primary MCD, admission serum uric acid was nonlinearly associated with AKI, whereas age was associated with pathology-reported tubular injury without evidence of significant nonlinearity. Older patients had higher rates of AKI, clinically documented infection, and pathology-reported tubular injury. These findings highlight age-related heterogeneity in renal and infectious complications among adults with MCD, although causal inference is limited by the retrospective design. Not applicable. This study was a retrospective observational study and was not a clinical trial.