Renal biopsy refers to obtaining a small piece of kidney tissue for microscopic examination. Percutaneous renal biopsy was first performed by Alwall in 1944. In renal disease, renal biopsy is helpful to:
- Establish the diagnosis
- Assess severity and activity of disease
- Assess prognosis by noting the amount of scarring
- To plan treatment and monitor response to therapy
Renal biopsy is associated with the risk of procedure-related morbidity and rarely mortality. Therefore, before performing renal biopsy, risks of the procedure and benefits of histologic examination should be evaluated in each patient.
Indications for Renal Biopsy
- Nephrotic syndrome in adults (most common indication)
- Nephrotic syndrome not responding to corticosteroids in children.
- Acute nephritic syndrome for differential diagnosis
- Unexplained renal insufficiency with near-normal kidney dimensions on ultrasonography
- Asymptomatic hematuria, when other diagnostic tests fail to identify the source of bleeding
- Isolated non-nephrotic range proteinuria (1-3 gm/24 hours) with renal impairment
- Impaired function of renal graft
- Involvement of kidney in systemic disease like systemic lupus erythematosus or amyloidosis
Contraindications
- Uncontrolled severe hypertension
- Hemorrhagic diathesis
- Solitary kidney
- Renal neoplasm (to avoid spread of malignant cells along the needle track)
- Large and multiple renal cysts
- Small, shrunken kidneys
- Acute urinary tract infection like pyelonephritis
- Urinary tract obstruction
Complications
- Hemorrhage: As renal cortex is highly vascular, major risk is bleeding in the form of hematuria or perinephric hematoma. Severe bleeding may occasionally necessitate blood transfusion and rarely removal of kidney.
- Arteriovenous fistula
- Infection
- Accidental biopsy of another organ or perforation of viscus (liver, spleen, pancreas, adrenals, intestine, or gallbladder)
- Death (rare).
Procedure
- Patient’s informed consent is obtained.
- Ultrasound/CT scan is done to document the location and size of kidneys.
- Blood pressure should be less than 160/90 mm of Hg. Bleeding time, platelet count, prothrombin time, and activated partial thromboplastin time should be normal. Blood sample should be drawn for blood grouping and cross matching, as blood transfusion may be needed.
- Patient is sedated before the procedure.
- Patient lies in prone position and kidney is identified with ultrasound.
- The skin over the selected site is disinfected and a local anesthetic is infiltrated.
- A small skin incision is given with a scalpel (to insert the biopsy needle). Localization of kidney is done with a fine bore 21 G lumbar puncture needle. A local anesthetic is infiltrated down to the renal capsule.
- A tru-cut biopsy needle or spring loaded biopsy gun is inserted under ultrasound guidance and advanced down to the lower pole. Biopsy is usually obtained from lateral border of lower pole. Patient should hold his/her breath in full inspiration during biopsy. After obtaining the biopsy and removal of needle, patient is allowed to breath normally.
- The biopsy should be placed in a drop of saline and examined under a dissecting microscope for adequacy.
- Patient is turned to supine position. Vital signs and appearance of urine should be monitored at regular intervals. Patient is usually kept in the hospital for 24 hours.
Kidney biopsy can be divided into three parts for light microscopy, immunofluorescence, and electron microscopy. For light microscopy, renal biopsy is routinely fixed in neutral buffered formaldehyde. Sections are stained by:
- Hematoxylin and eosin (for general architecture of kidney and cellularity)
- Periodic acid Schiff: To highlight basement membrane and connective tissue matrix.
- Congo red: For amyloid.
For electron microscopy, tissue is fixed in glutaraldeyde. In immunohistochemistry, tissue deposits of IgG, IgA, IgM, C3, fibrin, and κ and λ light chains can be detected by using appropriate antibodies. Many kidney diseases are immune-complex mediated.
