Indications for Kidney Biopsy
Kidney biopsy is the gold standard for diagnostic evaluation of glomerular diseases and should be performed when the biopsy result is expected to modify treatment and/or provide additional prognostic information. 1
Primary Indications
Proteinuria
- Persistent proteinuria ≥0.5 g/24 hours or UPCR ≥500 mg/g 1
- Nephrotic-range proteinuria (especially with normal-sized kidneys) 1
- Albumin:creatinine ratio >30 mg/mmol 1
Kidney Function Abnormalities
- Unexplained decrease in GFR 1
- Acute kidney injury stage 3 1
- eGFR <60 ml/min/1.73m² with decline >2 ml/min/1.73m² per year 1
- Unexplained renal impairment with normal kidney size 2
Urinary Abnormalities
- Proteinuria with glomerular hematuria and/or cellular casts 1
- Persistent isolated glomerular hematuria (after excluding other causes) 1
- Isolated leukocyturia (after excluding infection or drug causes) 1
Systemic Diseases with Kidney Involvement
- Lupus nephritis with evidence of kidney involvement 1
- Cancer patients with significant new-onset proteinuria (>1 g/day) or worsening kidney function 1
- Suspected monoclonal gammopathy of renal significance (MGRS) 1
Special Considerations
When Biopsy May Be Deferred
Biopsy may not be required in certain conditions where serological diagnosis is highly specific:
- PLA2Rab+ membranous nephropathy (especially with normal eGFR) 1
- MPO+ or PR3+ ANCA vasculitis 1
- Anti-glomerular basement membrane disease 1
- Alport disease 1
- Fabry disease 1
- Familial focal segmental glomerulosclerosis with well-characterized mutations 1
- Systemic lupus erythematosus with typical presentation 1
Contraindications
- Cancer patients with poor prognosis 1
- When expected gain from diagnosis is less than patient's expected survival 1
- Uncontrolled hypertension 3
- Uncorrectable bleeding disorders 3
- Solitary kidney (relative contraindication) 4
Biopsy Adequacy Standards
For adequate diagnostic evaluation:
- Light microscopy: 8-10 glomeruli minimum 1
- Immunohistology: Testing for IgG, IgA, IgM, C3, C4, C1q, fibrin, κ/λ light chains 1
- Electron microscopy: To define location and characteristics of immune deposits 1
Repeat Biopsy Indications
Repeat kidney biopsy should be performed if:
- Information will potentially alter the therapeutic plan 1
- Information will contribute to estimation of prognosis 1
- Evaluating long-term consequences of systemic therapy 1
- Patient initially treated based on seropositivity but doesn't follow expected course 1
Special Populations
Cancer Patients
- Consider biopsy for significant new-onset proteinuria (>1 g/day) or worsening kidney function 1
- In patients with kidney cancer undergoing surgery, examination of non-neoplastic kidney tissue is highly recommended 1
- For cancer survivors without active cancer and good prognosis, follow general population guidelines 1
Transplant Recipients
- Consider biopsy in allogeneic hematopoietic cell transplantation recipients with kidney injury, as findings are heterogeneous (thrombotic microangiopathy, acute tubular injury, membranous nephropathy) 5
High-Risk Patients
- Alternative biopsy approaches may be considered for patients with bleeding risk:
- Transjugular (transvenous) biopsy
- Laparoscopic biopsy
- Open (surgical) biopsy 6
Diagnostic Value
The most common histological findings in patients with unexplained renal impairment and normal-sized kidneys are:
- Interstitial nephritis
- Rapidly progressive glomerulonephritis
- Various types of glomerulonephritis 2
In biopsied AKI patients, findings often include:
- Acute interstitial nephritis (commonly drug-induced)
- Acute tubular injury
- Coexisting glomerular diseases (IgA nephropathy, minimal change disease, focal segmental glomerulosclerosis) 7
Kidney biopsy remains indispensable, and its diagnostic and prognostic value cannot be substituted by other clinical or laboratory variables 1. Despite the risks, the benefits of diagnosing treatable conditions like interstitial nephritis and rapidly progressive glomerulonephritis outweigh the disadvantages 2.