Renal biopsy — indications in the older adult

Age alone is not a contraindication. The indications and the incidence of complications of renal biopsy are the same for older and younger adults. However, when a complication does occur in an older adult it is generally more serious — so patient selection and post-procedure monitoring matter more.

Main indications. Nephrotic syndrome (accounts for 50% of biopsy indications in the elderly), unexplained acute kidney injury, suspected rapidly progressive glomerulonephritis, unexplained CKD with normal-sized kidneys, non-nephrotic proteinuria with haematuria, and suspected systemic disease — vasculitis, myeloma, amyloidosis, lupus.

The yield is high and clinically useful. Although older adults formed only 23% of the biopsy series, they were over-represented relative to their share of the population, and primary glomerulonephritis was the most frequent biopsy-proven renal disease in this group — more frequent than in younger adults.

A biopsy finds treatable disease that is easily missed. Crescentic glomerulonephritis peaks at 60–79 years and presents as rapidly progressive renal failure; renal vasculitis is probably the commonest primary cause of renal failure in older adults. Both respond to steroids and cyclophosphamide.

Biopsy also drives the search for a secondary cause. About 20% of membranous nephropathy in the elderly is secondary to an underlying malignancy (chiefly lung and colon adenocarcinoma) or to drugs; minimal change disease may be caused by NSAIDs or associated with lymphoma. The histological diagnosis therefore triggers a malignancy and drug review.

Contraindications and precautions. Uncontrolled hypertension, bleeding diathesis or continuing anticoagulation/antiplatelet therapy, solitary kidney (relative), small echogenic kidneys, active urinary tract infection, large cysts or tumour, and an uncooperative patient. Before biopsy: control BP, stop antiplatelets and anticoagulants, check haemoglobin, platelets and coagulation, and ultrasound for kidney size and number. Afterwards watch for haematuria, perinephric haematoma and arteriovenous fistula.

KDIGO Glomerular Diseases guideline — the "biopsy-free" exception, with an important geriatric caveat. In a patient with nephrotic syndrome, a positive anti-PLA2R antibody and normal kidney function, biopsy is not required to diagnose membranous nephropathy. But in older adults, membranous nephropathy can co-exist with renal amyloidosis or diabetic nephropathy — conditions with entirely different treatment and prognosis — so biopsy should still be performed when the clinical picture is atypical, when renal function is declining, or when a plasma-cell dyscrasia is suspected.