Kidney Biopsy (Renal Biopsy)

Blood and urine tests can tell you that your kidneys are leaking protein or losing function. Often they can't tell you why. Protein in the urine, for example, can come from several different kidney diseases. Some need strong medicines that suppress the immune system, and others need none.

A kidney biopsy removes two or three thin cores of kidney tissue with a hollow needle passed through the skin of your back. Ultrasound guides the needle to the lower edge of the kidney, away from its large blood vessels. A pathologist then studies the tissue with special stains and several kinds of microscope, which show the pattern of damage and usually its cause.

The result often changes treatment directly. It can confirm a disease such as IgA nephropathy or lupus nephritis and show how active the inflammation is. It also reveals how much permanent scarring there is, which tells your nephrologist how much function might still be saved. Bleeding is the main risk. Most of it is minor and stops on its own, which is why you rest in bed for several hours afterwards.

Our nephrology department performs kidney biopsies as part of diagnosing conditions such as glomerulonephritis, nephrotic syndrome and diabetic kidney disease, and then manages treatment and long-term follow-up with you.

Your nephrologist suggests a biopsy when the answer is likely to change your treatment. It isn't done when the kidneys are already small and shrunken on ultrasound, because long-standing scarring leaves little to treat.

Kidney tissue needs special processing, so results take longer than a blood test. If treatment is urgent, a first reading can be ready within a few days. The full report usually takes 1 to 2 weeks, because it includes immunofluorescence (stains that show antibody deposits) and electron microscopy (very high magnification, often done at a specialist laboratory).

The report names the pattern of disease, such as minimal change disease, FSGS (focal segmental glomerulosclerosis), membranous nephropathy, IgA nephropathy, lupus nephritis with its class, or diabetic kidney disease. It also says how active the inflammation is and how much of the kidney is scarred (fibrosis). Active inflammation with little scarring usually means treatment has a good chance of helping. Heavy scarring means some damage is permanent, and the focus moves to protecting the function that's left.

Your nephrologist goes through the report with you and plans treatment, which might be steroids or other immune-suppressing medicines, blood pressure tablets that also cut protein leakage, or regular monitoring. Occasionally the sample is too small to answer the question and the biopsy has to be repeated.