Renal Biopsy: Indications, Contraindications, and Pre-Procedure Assessment

Overview

• Brenner and Rector's The Kidney, Box 26.1 / Chapter 26
• Harrison's Principles of Internal Medicine 22E (2025), Ch. 55
• Goldman-Cecil Medicine, Ch. 100

Indications for Renal Biopsy

From Brenner & Rector's The Kidney (Box 26.1) - The Standard Reference

Detailed Breakdown by Clinical Scenario

1. Nephrotic Syndrome

• Adults with idiopathic nephrotic syndrome - biopsy is almost always indicated (Goldman-Cecil).
• Children: Biopsy is generally reserved for:
  • Steroid-resistant nephrotic syndrome (SRNS) - near-universal agreement
  • Steroid-dependent nephrotic syndrome (in some centers)
  • Infants (age <1 year) with nephrotic syndrome - early biopsy recommended
  • Persistent elevated serum creatinine, hypocomplementemia, or gross hematuria alongside nephrotic syndrome
  • Children who fail initial empiric steroid therapy
  • Before starting calcineurin inhibitors (cyclosporine, tacrolimus) to establish baseline scarring
• Biopsy is not routinely indicated during the first episode of acute nephrotic syndrome in children (Tintinalli's).

2. Glomerulonephritis / Hematuria

• RBC casts in urine = indication for early renal biopsy (Harrison's 22E). RBC casts have critical implications for diagnosis, prognosis, and treatment.
• Hematuria without RBC casts can also indicate glomerular disease - phase contrast microscopy for dysmorphic RBCs ("acanthocytes") helps refine this.
• Microscopic hematuria with any degree of proteinuria = biopsy indication (Brenner).

3. Acute Kidney Injury (AKI)

• AKI without an identifiable inciting cause - a clear indication (Goldman-Cecil).
• Notable exception: Hospital-acquired kidney failure rarely meets this threshold.
• AKI in specific settings (e.g., suspected rapidly progressive GN, vasculitis, allergic interstitial nephritis with eosinophilia) warrants urgent biopsy.
• Atheroembolic renal failure: Biopsy can confirm diagnosis but is often unnecessary when other stigmata are present (Harrison's 22E).

4. Systemic Disease with Renal Involvement

• Lupus nephritis - biopsy required to classify histological class (I-VI), which guides immunosuppressive therapy (Firestein's Rheumatology, Brenner).
  • Repeat biopsy indicated when there is increased disease activity or change in histologic class.
• Vasculitis (ANCA-associated, anti-GBM disease) - biopsy for classification and severity assessment.
• Henoch-Schonlein Purpura / IgA vasculitis - when hypertension, hematuria, or proteinuria present.
• Diabetic nephropathy - biopsy rarely required UNLESS another cause is suspected (Goldman-Cecil). Kimmelstiel-Wilson nodular glomerulosclerosis is the classic finding but seen in only ~25% of cases.

5. Chronic Kidney Disease (CKD) of Unknown Cause

• Unexplained CKD warrants biopsy - important to exclude treatable causes.
• Full exome genetic testing also has ~20% diagnostic yield in CKD of unknown cause and complements (does not replace) biopsy.

6. Transplant Kidney

• Unexplained deterioration of transplant function - biopsy for rejection classification.
• For management of BK virus nephropathy (threshold: viruria 4-6 log₁₀ on serum testing, then biopsy considered).

Contraindications

Absolute Contraindications

• Uncontrollable bleeding diathesis / uncorrectable coagulopathy
• Uncooperative patient (inability to lie still / follow breath-hold instructions)
• Solitary functioning kidney (relative - open/laparoscopic approach preferred)
• Renal neoplasm / cyst at biopsy site
• Active urinary tract infection (UTI)
• Severe uncontrolled hypertension (BP ≥160/100 mm Hg significantly doubles bleeding risk)

Relative Contraindications

• Thrombocytopenia or prolonged clotting time (can be corrected with FFP, platelets, or DDAVP)
• Hemoglobin <11 g/dL (transfuse to >10 g/dL prior to procedure)
• Solitary kidney (prefer open/laparoscopic approach)
• Small echogenic kidneys (advanced CKD - biopsy yield low, risk:benefit unfavorable)
• Anatomical abnormalities / horseshoe kidney (CT-guided or open biopsy preferred)
• Recent NSAID use (e.g., naproxen within 24 hours)
• Pregnancy after 32 weeks (increased bleeding risk - biopsy complications significantly higher postpartum)

Pre-Biopsy Assessment (Biopsy Flowchart - Brenner & Rector)

Fig. 26.2 Renal biopsy flowchart - Brenner and Rector's The Kidney

1. Ultrasound excludes obstruction or significant anatomical abnormality
2. UTI excluded by negative midstream urine culture (treat infection first if present)
3. Hemoglobin >11 g/dL (transfuse to achieve >10 g/dL if not met)
4. Clotting normal, platelet count normal (correct with FFP/platelets if abnormal; consider transjugular/open biopsy if uncorrectable)
5. Blood pressure <150/90 mmHg (control hypertension first)
6. If all above met → Proceed to percutaneous biopsy

Alternative Biopsy Approaches

Complications of Renal Biopsy

• Overall complication rate: 3.5-13% (majority minor)
• Bleeding: ~50% of patients have a hemoglobin drop post-biopsy; ~1/3 develop hematoma
• Significant bleeding requiring intervention: ≤7%
• Transfusion rate (without coagulopathy): ~1-2% (Goldman-Cecil)
• Arteriovenous fistula: usually asymptomatic, spontaneously resolves
• Sepsis: rare
• Mortality: <0.2% (from uncontrolled hemorrhage in largest series)
• DDAVP (0.3 mcg/kg SC) may reduce post-biopsy bleeding complications, particularly in lower-risk patients

Post-Biopsy Observation

• Minimum 6-8 hours bed rest
• Overnight stay recommended: identifies 85-95% of complications at 12 hours, 89-98% at 24 hours
• Monitor: BP, pulse, urine color for hematuria

Summary Table: Indications at a Glance

• Brenner and Rector's The Kidney, 2-Volume Set - Box 26.1, Chapter 26 (Salama & Cook)
• Harrison's Principles of Internal Medicine 22E (2025) - Chapter 55 (Intrinsic Renal Disease / Hematuria approach)
• Goldman-Cecil Medicine, International Edition - Chapter 100 (Renal Biopsy)
• Comprehensive Clinical Nephrology, 7th Edition
• Smith and Tanagho's General Urology, 19th Edition

Thyroid Ultrasound Scoring: TI-RADS (Thyroid Imaging Reporting and Data System)

What is TI-RADS?

All validated risk stratification systems reduce unnecessary FNAs by at least 45%, in part due to the recommendation not to perform FNA for spongiform nodules. - Harrison's Principles of Internal Medicine 22E (2025)

ACR TI-RADS: The Point-Based Scoring System

ACR TI-RADS Point-Based Scoring System - Goldman-Cecil Medicine, International Edition

Category 1: COMPOSITION (Choose ONE)

Key notes:

• Spongiform: If a nodule is spongiform, stop here - do NOT add further points from other categories
• Assign 2 points if composition cannot be determined due to calcification

Category 2: ECHOGENICITY (Choose ONE)

Assign 1 point if echogenicity cannot be determined

Category 3: SHAPE (Choose ONE)

Assessment: Measured on transverse image - height parallel to sound beam, width perpendicular. Usually assessable by visual inspection.

Category 4: MARGIN (Choose ONE)

• Lobulated = protrusions into adjacent tissue
• Extrathyroidal extension (obvious invasion) = strong indicator of malignancy
• Assign 0 points if margin cannot be determined

Category 5: ECHOGENIC FOCI (Choose ALL that apply)

This is the only multi-select category - add points for each echogenic focus type present

TI-RADS Level Classification (TR1-TR5)

Fig. 73.16 ACR TI-RADS Lexicon, TR Levels, and FNA Criteria - Sabiston Textbook of Surgery, 8th Edition

*For TR5 nodules 5-9 mm (papillary microcarcinomas), refer to specific papillary microcarcinoma management guidelines.

Key Lexicon Definitions

Ultrasound Features Suspicious for Malignancy

• Microcalcifications (punctate echogenic foci)
• Absence of peripheral halo
• Irregular border
• Hypoechoic / very hypoechoic texture
• Taller than wide on transverse imaging
• Marked intranodular vascularity on color Doppler
• Extrathyroidal extension

ATA (American Thyroid Association) Risk Stratification - Companion System

"The American Thyroid Association system is based on ultrasonographic patterns, unlike ACR TI-RADS which is based on a point system." - Goldman-Cecil Medicine

European TI-RADS (EU-TIRADS) - Brief Overview

Workflow: How to Use TI-RADS Clinically

Thyroid nodule detected (palpation or incidental imaging)
    ↓
Measure TSH
    ↓ (if TSH suppressed) → Radionuclide scan → Hot nodule → No FNA needed
    ↓ (TSH normal or elevated)
Thyroid ultrasound with TI-RADS scoring
    ↓
Assign TR1-TR5 based on point total
    ↓
TR1/TR2: Observe, no biopsy
TR3: FNA if ≥2.5 cm
TR4: FNA if ≥1.5 cm
TR5: FNA if ≥1 cm
    ↓
FNA result → Bethesda classification (I-VI) guides surgery/observation

Additional Points from Harrison's 22E

• ACR TI-RADS is the most widely used RSS in the United States
• A spongiform nodule (TR1) has <3% chance of cancer - observation recommended
• 10-20% of solid hypoechoic nodules with smooth borders (TR4) are malignant
• No RSS recommends routine FNA for any nodule <1 cm unless metastatic cervical lymph nodes are present
• Thyroid nodules are present in up to 50% of individuals >50 years on ultrasound
• 18FDG-PET hypermetabolic thyroid nodules carry ~35% malignancy risk and should be biopsied if ≥1 cm (Goldman-Cecil)

• Harrison's Principles of Internal Medicine 22E (2025, McGraw Hill) - Chapter 397: Thyroid Nodules
• Goldman-Cecil Medicine, International Edition - Chapter 207: Thyroid / ACR TIRADS section (citing Tessler et al. 2017)
• Sabiston Textbook of Surgery, 8th Edition - Chapter 73 (Fig. 73.16)
• Cummings Otolaryngology Head and Neck Surgery - Box 114.1
• Tietz Textbook of Laboratory Medicine, 7th Edition - Imaging the Thyroid
• Tessler FN et al. ACR TI-RADS White Paper. J Am Coll Radiol. 2017;14:587-595.