A renal biopsy is a procedure in which a sample of kidney (also called renal) tissue is obtained. Microscopic examination of the tissue can provide information helpful in diagnosing and treating the kidney disease.
WHAT ARE THE INDICATIONS OF RENAL BIOPSY?
Renal biopsy is indicated in some patients with kidney disease. It is most commonly performed in the following clinical setting.
1. High levels of proteinuria – Proteinuria (protein in the urine) is an abnormality present in a number of kidney diseases. Protein leaking can occur due to a variety of kidney diseases and the exact treatment depends on the diagnosis. The term nephrotic syndrome is used in patients who have heavy proteinuria in associated with edema (swelling) of the arms and legs.
2. Hematuria in the presence of other evidence of renal disease – Hematuria (blood in the urine) is a symptom of a number of conditions affecting the kidneys and urinary tract. While renal biopsy is not indicated in all cases of hematuria, it may be performed in patients who have hematuria along with evidence of progressive renal disease.
3. Acute or chronic (renal) kidney failure – Renal failure refers to kidney injury that is sufficiently severe to markedly impair kidney function. It can occur abruptly (called acute renal failure) or progress over a period of time (called chronic renal failure). The cause of acute renal failure can often be determined without renal biopsy. Biopsy is performed in those instances when the cause is uncertain.
4. A renal biopsy is also obtained when noninvasive evaluation has been unable to establish the correct diagnosis among patients with chronic renal failure. Patients with certain chronic conditions may also have repeat biopsies to monitor changes in the kidney over time. For example, in patients with systemic lupus erythematosus, repeat biopsies can help distinguish between kidney changes from active disease and those related to scarring from previous injury. Such a distinction is important as treatment for each situation is different.
Acute nephritic syndrome – Patients with acute nephritic syndrome present with hematuria, proteinuria, high blood pressure, and impaired renal function. Renal biopsy is typically performed unless the cause can be established by specific blood tests.
HOW IS A RENAL BIOPSY PERFORMED?
In most cases, a “percutaneous” renal biopsy is performed in which the patient is awake and local anesthesia is given to minimize pain. In this procedure, a special needle is inserted through the skin in the back and into the kidney. Once the needle is in contact with the kidney, a sample of renal tissue is withdrawn. Ultrasonography (an imaging method that uses sound waves to visualize structures in the body) is often used to guide the needle to the kidneys.
In patients in whom the risks of percutaneous renal biopsy are too great, a different approach may be used to perform the biopsy. In most of these patients, minor surgery may be performed to obtain the sample of kidney tissue; this procedure is called open renal biopsy.
CAN COMPLICATIONS OCCUR AS A RESULT OF RENAL BIOPSY?
Serious complications of renal biopsy are quite rare. Patients are monitored closely for a number of hours after a biopsy is performed so that any complications can be detected early in the recovery period. Complications that can result from renal biopsy include bleeding, pain, and other less frequent problems.
Bleeding is the most common complication of renal biopsy. Most patients experience microscopic hematuria (blood in the urine that can be seen only under the microscope) for a short time. Rarely, bleeding is severe enough to require a blood transfusion or surgery. It has been estimated from reviews of the medical literature that surgery is required to control the bleeding in 0.1 to 0.4 percent of percutaneous renal biopsies (1 to 4 per 1000) with removal of the kidney required in approximately 0.06 percent (6 per 10,000).
To decrease the risk of bleeding, blood tests to evaluate the body’s normal clotting mechanism are monitored before the biopsy is performed and any abnormalities are corrected. In addition, patients are usually advised to avoid medicines that increase the risk of bleeding (such as aspirin or nonsteroidal antiinflammatory drugs) for at least one week prior to the biopsy. If patients are on warfarin or heparin (other drugs that impair clotting and increase the risk of bleeding), the optimal strategy is decided by the doctor based upon the reasons for the kidney biopsy and why the patient is taking these drugs.
Pain is a common problem and is transient and usually not severe. Pain lasting more than 12 hours occurs in approximately 4 percent of biopsies. Severe or prolonged pain can occur if a blood clot obstructs one of the tubes leading from the kidney or there is a large hematoma (a mass of clotted blood) that stretches the kidney..
Damage to the walls of an adjacent artery and vein caused by the biopsy needle can lead to the development of a fistula or connection between the two blood vessels. Fistulas generally do not cause problems and usually close on their own over one to two years.
4. Urinary tract infection
Urinary tract infection should not occur after renal biopsy unless the patient has an active infection in or around the kidneys.
Death is an extremely rare complication of renal biopsy. Reviews of the medical literature suggest a mortality rate of about 0.1 percent (1 in 1000).
CONTRAINDICATIONS TO A RENAL BIOPSY – Renal biopsy is generally contraindicated in patients who have one or more of the following:
• An uncorrectable bleeding condition
• Small kidneys
• Severe hypertension that cannot be controlled with medication
• Multiple bilateral renal cysts or a renal tumor
• Hydronephrosis (a condition in which the flow of urine is obstructed leading to kidney damage)
• Active infection of the tissues in, or surrounding, the kidney
• An uncooperative patient
As previously mentioned, alternatives to a percutaneous biopsy, such as open or transjugular biopsy, may be utilized among patients with some of these conditions.