Renal biopsy

Most acute renal failure is due to pre-renal causes or acute tubular necrosis, and recovery of renal function typically occurs over the course of a few weeks.

Renal biopsy should be performed only if knowing histology will influence management.

Once chronic renal failure is established, the kidneys are small, there is a higher risk of bleeding from biopsy, and the results are usually unhelpful.


Indications for renal biopsy:

• What is the cause of this acute renal failure (p292)?
• Investigating glomerulonephritis, eg is persistent haematuria from IgA nephropathy, thin basement membrane disease, or hereditary nephropathy?
• What is the cause of this heavy proteinuria (eg >1g/d, when you know that diabetes mellitus is not the cause).
• Renal dysfunction post-transplantation (p297): is the cause rejection, acute tubular necrosis, drug toxicity, or recurrence of renal disease?4

Pre-procedure:

• Check FBC, clotting, group & save.
• Obtain written informed consent.
• Ultrasound (if only 1 kidney, risk is magnified).
• Stop aspirin 1 week and warfarin at least 2 days in advance.

Contraindications:

• Abnormal clotting
• Hypertension >160/>90
• Single kidney
• Chronic renal failure with small kidneys (<9cm)
• Uncooperative patient

Procedure:

• Biopsy is done under ultrasound guidance with the patient lying in the prone position and the breath held.
• Samples should be sent to histology.
• A clear indication on the request form of why the test has been done, eg exclude amyloidosis, will help in the selection of special stains, immunofluorescence and use of electron microscopy.

Post procedure:

• Bed rest for a minimum of 6hrs.
• Monitor pulse, BP, symptoms, and urine colour.
• Bleeding is the main complication; most occurs within 8 hrs, although it may be delayed by up to 72hrs.
• Macroscopic haematuria occurs in ~10%, although blood transfusion is only needed in ~1-2%.
• Aspirin or warfarin can be restarted the next day if uncomplicated.

Images of renal histology
Fig 1. Crescentic glomerulonephritis: a proliferation of epithelial cells and macrophages with rupture of Bowman's capsule, in this patient caused by antiglomerular basement membrane (Goodpasture's) disease, see p692.

Fig 2. Immunofluorescence for IgG, showing linear staining for glomerular basement, characteristic of anti-glomerular basement membrane (Goodpasture's) disease.

Fig 3. US-guided biopsy of a transplant kidney— this reduces the risk of damaging the renal vessels and pelvis, as well as any nearby bowel (although the graft is usually extra-peritoneal). The red arrow is
point of entry of the biopsy needle (hyperechoic and casting an acoustic shadow deeper). The hypoechoic tissue around the needle is from the infiltration of local anaesthetic. 3 separate ‘shots’ of the biopsy ‘gun’ are usually enough to get a good sample, though let the patient know what a ‘shot’ sounds like before starting, so that they don't start off down the ward!

Fig 4. Renal allograft rejection: Cellular rejection, showing a tubulointerstitial infiltrate of lymphocytes—this is usually graded according to the Banff criteria. Although ‘rejection’ may sound fierce, it is usually easily and well-treated by increasing immunosuppression eg with a pulse of methylprednisolone. ▶ Watch for infection (eg CMV).

Fig 5. Renal allograft rejection: Antibody-mediated rejection, with diffuse peritubular capillary staining for C4d complement. Humoral (antibody-mediated) rejection is more problematic than cell-mediated rejection (above); it may need immunoglobulin therapy with plasma phoresis in an attempt to clear the system of donor-specific antibodies.