A kidney biopsy (or renal biopsy) is a surgical procedure in which a small piece of a kidney is removed from the body and examined. The examination usually includes microscopic observation and may include cultures and other tests.
Reasons For Having A Kidney Biopsy
A kidney biopsy is conducted when there are indications of certain kinds of kidney disease and less invasive diagnostic methods do not suffice for a clear diagnosis. A biopsy may be ordered when the patient has blood appearing in the urine and there are other signs of progressive kidney disease such as nephrotic syndrome.
A biopsy may also be ordered if urine tests reveal elevated protein in the urine. Again, the call for a renal biopsy is usually reserved for cases where other signs of advanced progressive kidney disease are present, or where the level of protein in the urine is rising.
When renal failure occurs, the cause can usually be determined without performing a biopsy, but when the cause is uncertain a biopsy may be ordered to clear up the diagnosis.
A renal biopsy is indicated when other tests indicate a growth on the kidney that may be cancerous. In that case, tissue is taken from the tumor for examination to verify the presence of cancer.
Transplant Kidney Biopsy
All of the situations above call for a biopsy of the patient's own kidney (or "native kidney biopsy"). A biopsy is also indicated in some cases to examine a kidney that is offered by a donor for transplant. This is done when the transplanted kidney is not working as well as expected or when the function of a transplanted kidney deteriorates. Biopsy is performed to rule out the most obvious causes of the transplant failure, such as rejection and recurrence of the disease for which the transplant was performed.
Patients should avoid medicines that impair blood clotting for two weeks before the procedure is performed. These medicines include aspirin, heparin, and warfarin, as well as others.
The procedure does not require general anaesthesia. It is performed with the patient lying prone on an operating table. Mild sedation may be used, along with local anesthetic. The kidney is precisely located using an ultrasound. A small incision is made over the kidney to allow insertion of the biopsy needle, which is usually guided by a real-time medical imaging procedure (normally ultrasound). The biopsy needle is a spring-loaded device that makes a noise as it is driven into the kidney. If the anesthetic is properly administered, however, the procedure causes no pain.
A sample of core kidney tissue, usually less than 1 millimeter in diameter by about a centimeter long, is extracted using the needle. More than one sample may be taken in some cases, depending on the condition that calls for use of the biopsy procedure.
After extraction of the kidney tissue sample, the patient is asked to lie flat for four to six hours to minimize risk of bleeding. After that time, if no complications arise the patient is usually discharged. Mild to moderate pain may occur after the anesthetic wears off and is treated with simple analgesics such as Tylenol. Severe pain is usually an indication of bleeding and calls for post-operative treatment.
Serious complications from kidney biopsy are not common. The most common complication is bleeding. Most bleeding following a renal biopsy resolves itself without treatment. Surgical operations to control serious bleeding may be indicated in very rare cases. It's also possible (but unlikely) that nearby organs such as the intestines or the bladder may be damaged.
All surgical procedures do carry some risks, which is why a biopsy is not ordered routinely or without significant diagnostic benefit.
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