Proteinuria after kidney transplant is common, and persistent cases threaten graft survival

Why it matters: Proteinuria and high blood pressure are the main drivers of chronic kidney disease progression. After kidney transplantation, proteinuria is increasingly recognized as a treatable risk factor for graft loss and death in adults, and for graft loss in children. Because it is so common and its causes range from benign to serious, clinicians need a clear approach to measuring, interpreting, and treating it.

What was reviewed: This comprehensive narrative review, written by pediatric nephrology and transplant specialists, covers how to measure proteinuria, how often it occurs, its timing and type, its causes, its consequences for graft and patient survival, and treatment options. Only the first sections of the paper were available for this summary (measurement, prevalence, timing and types, degree). The origin, consequences, and treatment sections are summarized from the abstract only.

Key points: Prevalence varies widely, from 11% to 82% across studies, largely because definitions differ. Older adult studies using a 2 g/day cutoff found 10–22%. Newer studies using stricter native-CKD-style cutoffs (0.15–0.3 g/day) found 31–45%. In one pediatric study, all children had proteinuria at 1 week post-transplant. Other pediatric studies found 47–82% affected at 6 months or later. Early proteinuria usually resolves by about 2 months and does not harm long-term graft survival. Proteinuria that appears at 2–3 months or persists beyond 3 months is associated with greater long-term graft loss. Tubular proteinuria predominates, in up to 79% of adults and 80% of children, and the heavier the proteinuria, the more likely it is glomerular. In children it is usually borderline or mild (around 20 mg/mmol creatinine, or 200 mg/m²/day). In adults, 60–80% of those with nephrotic-range proteinuria have glomerular allograft injury, mainly transplant glomerulopathy, versus about 12% of those with non-nephrotic proteinuria.

Practical implications: The authors recommend a first-morning spot protein/creatinine ratio as a practical alternative to 24-hour collection. They suggest measuring total protein plus albumin (glomerular) and alpha-1- or beta-2-microglobulin (tubular) to localize the injury. Per the abstract, children with idiopathic FSGS should have daily proteinuria checks for the first 2–3 weeks to catch recurrence quickly. Causes to look for include rejection, mTOR inhibitors, hypertension, and recurrence. A graft biopsy should be considered if no cause is found. ACE inhibitors and ARBs are the main antiproteinuric therapy, with additional antihypertensives if proteinuria is resistant. The long-term goal is a ratio below 20 mg/mmol (200 mg/g).

Caveats: This is a narrative review rather than a systematic analysis or trial. The pediatric evidence base is small, and cutoffs and methods differ between studies. The text supplied was truncated, so detailed discussion of causes, outcomes, and newer therapies could not be verified.