What is the procedure for a renal biopsy in patients with suspected kidney disease or impaired renal function?

Renal Biopsy Procedure in Patients with Suspected Kidney Disease

A renal biopsy is the gold standard diagnostic procedure for evaluating patients with suspected kidney disease and should be performed when there is evidence of kidney involvement that requires specific diagnosis for treatment decisions, especially in cases of proteinuria, hematuria, or declining renal function. 1

Indications for Renal Biopsy

Strongly Recommended When:

• Nephrotic-range proteinuria (>3.5g/24h)
• Rapidly declining kidney function (>2ml/min/1.73m² per year)
• Acute kidney injury stage 3
• Proteinuria with hematuria
• Albumin:creatinine ratio >30mg/mmol
• Fanconi syndrome 1, 2

Consider Biopsy When:

• Acute kidney injury stage 1 or 2
• eGFR <60 ml/min/1.73m² with slower decline
• Albumin:creatinine ratio 3-30 mg/mmol with eGFR >60 ml/min/1.73m²
• Hematuria with eGFR <60 ml/min/1.73m²
• Persistent proteinuria despite appropriate therapy 1, 2

May Proceed Without Biopsy When:

• PLA2Rab+ membranous nephropathy (especially with normal eGFR)
• MPO+ or PR3+ ANCA vasculitis
• Anti-glomerular basement membrane disease
• Known diagnosis of diabetic kidney disease with typical features
• Well-characterized genetic kidney diseases 1, 2

Pre-Biopsy Assessment

1. Laboratory Evaluation:

   • Complete blood count
   • Coagulation profile (PT, PTT, INR)
   • Kidney function tests (creatinine, eGFR)
   • Urinalysis with protein:creatinine ratio
   • Serum electrolytes and metabolic panel 2

2. Risk Assessment:

   • Bleeding risk factors: female gender, decreased GFR, elevated blood pressure
   • Contraindications: uncontrolled hypertension, bleeding disorders, solitary kidney
   • Consider alternative approaches for high-risk patients 2, 3

Biopsy Procedure

Standard Percutaneous Approach:

1. Patient Preparation:

   • NPO for 6-8 hours prior to procedure
   • Discontinue anticoagulants/antiplatelets per protocol
   • Control blood pressure to normotensive range 4

2. Positioning and Imaging:

   • Patient in prone position with pillow under abdomen
   • Ultrasound localization of lower pole of kidney
   • Mark optimal entry site (usually 1-2 cm below 12th rib) 4

3. Procedure Steps:

   • Sterile preparation and draping
   • Local anesthesia with 1-2% lidocaine
   • Small skin incision (optional)
   • Real-time ultrasound guidance for needle insertion
   • Use of semi-automatic spring-loaded biopsy device
   • Collection of 2-3 core samples (16-gauge needle recommended) 4

4. Post-Procedure:

   • Compression of biopsy site
   • Bed rest for 6-24 hours (varies by institution)
   • Vital sign monitoring
   • Observation for hematuria and flank pain 4

Alternative Approaches for High-Risk Patients:

• Transjugular Renal Biopsy: For patients with bleeding disorders, obesity, or single kidney
• Laparoscopic Biopsy: For patients with anatomical challenges or failed percutaneous approach
• Open Surgical Biopsy: Rarely needed but may be combined with other surgical procedures 3

Specimen Processing

A comprehensive renal biopsy evaluation requires:

1. Light Microscopy:

   • Minimum 8-10 glomeruli for adequate diagnosis
   • Staining: Hematoxylin and eosin, periodic acid-Schiff, Masson trichrome, Jones methenamine silver, Congo red 1

2. Immunohistochemistry:

   • Immunofluorescence or immunoperoxidase staining
   • Evaluation for IgG, IgM, IgA, C1q, C3, kappa and lambda light chains 1

3. Electron Microscopy:

   • Evaluation of ultrastructural changes
   • Assessment of immune deposits, foot process effacement, and basement membrane alterations 1

Complications and Management

• Major Complications: Bleeding (4% risk), arteriovenous fistula, infection
• Management of Bleeding: Selective arterial embolization for major bleeding
• Risk Reduction: Use of 16-gauge needle (balance between diagnostic yield and bleeding risk), limited needle passes, adequate post-procedure monitoring 4

Special Considerations

• Monoclonal Gammopathy: Renal biopsy is essential for diagnosis of monoclonal gammopathy of renal significance (MGRS) 1
• Lupus Nephritis: Biopsy is recommended when there is evidence of kidney involvement to guide therapy 1
• Elderly Patients: Age alone should not discourage biopsy, as most MGRS-related renal diseases occur in patients >50 years 1
• Advanced CKD: Biopsy may still be valuable if findings would alter management, even in advanced disease 2, 5

The renal biopsy remains a cornerstone diagnostic procedure in nephrology, providing critical information for diagnosis, prognosis, and treatment decisions. When performed with appropriate technique and patient selection, it offers substantial diagnostic benefit with manageable risk.