Definition and Overview
Kidney biopsy, or renal biopsy, is a medical diagnostic procedure that involves the removal of a small piece of the kidney to assess the condition of the organ's tissues under a microscope, and to eventually diagnose a problem. A renal biopsy can be useful in monitoring the progress of a kidney disease, or to determine the most effective and efficient treatment plan based on the diagnosed condition.
There are different types of kidney biopsy, which include the following:
- Targeted renal biopsy. This procedure, as the name implies, targets a particular lesion in the kidneys where the problem, such as a tumour, has been found. This minimizes the disturbance or eliminates the risk of damaging nearby tissue and other structures.
- Transplant renal biopsy. In this procedure, kidney tissue samples are taken from a transplanted kidney. It is performed when the kidney is not performing as well as expected or when there is a noticeable deterioration in organ function. Kidney tissue samples will be taken from the donor's organ to exclude factors such as BK nephropathy, kidney failure, disease, and rejection as causes of the transplanted kidney's poor performance. This is a standard procedure for many hospitals performing kidney transplants, and is performed right after, three months after, and a year after the transplant procedure.
- Implantation transplant biopsy. Also known as postperfusion transplant biopsy, this procedure is performed to determine the cause of a transplanted kidney's dysfunction.
- Imaging-guided renal biopsy. This type of renal biopsy involves the use of a real-time medical imaging equipment to guide the biopsy instruments, increasing the procedure's efficiency.
- Blind renal biopsy. Using a needle-swing technique to assess the position of the equipment during biopsy, this type of biopsy does not require the use of imaging equipment.
Before the 1950's, kidney biopsies were performed through an open operation. This was until two Danish physicians invented a method that only requires a biopsy needle to collect kidney tissue samples. Recent medical technologies such as CT scanning and ultrasound have improved the accuracy and safety of the procedure.
Who should undergo and expected results
Patients with kidney disease are usually the ideal candidates for this procedure. However, renal biopsy is not the first diagnostic procedure performed on such patients—it is only recommended when other less invasive tests did not produce enough information needed for the diagnosis, monitoring, and treatment of the condition. A nephrologist will determine whether a kidney biopsy is needed.
There are several reasons to perform a renal biopsy and these include the following:
- The presence of blood in the urine. Also known as haematuria, this symptom is typically associated with a variety of issues in the urinary tract in the kidneys. The nephrologist will perform the biopsy to diagnose the presence or absence of progressive renal disease or nephritic syndrome.
- The presence of protein in the urine. Also known as proteinuria, the presence of protein in the urine can indicate renal dysfunction.
- Renal failure. In the case of impaired kidney function due to injury to the organ, the nephrologist will perform the biopsy procedure to determine the cause of chronic or acute renal failure.
For patients who have undergone a kidney transplant, a renal biopsy is performed:
- To determine the presence of hidden disease in the transplanted organ. This is performed at fixed intervals after the transplant procedure to monitor not only the function of the transplanted kidney, but also the emergence of certain conditions.
- To determine the cause of the transplanted kidney's dysfunction.
A renal biopsy will not be performed if the patient is suffering from severe high blood pressure that cannot be managed or bleeding diathesis. The procedure will also not be performed on an uncooperative patient. Precaution and extreme care are needed when the patient has a skin infection on the site where the biopsy needle will be inserted, has anatomical irregularities or abnormalities in the kidney, or has uraemia or azotemia. Patients taking blood thinners as well as pregnant women are also not ideal candidates for the procedure.
How the procedure works
The procedure requires careful evaluation and analysis by the nephrologist before being performed. A renal biopsy does not come without risk, and the nephrologist must determine if the benefits of the procedure greatly outweigh the risks before he or she can proceed. The nephrologist will order blood tests and ultrasound to eliminate infection, blood clotting problems, and structural problems.
Before the renal biopsy procedure, the patient will need to stop taking medication that can prevent blood from clotting properly. This is to minimize the risk of internal bleeding.
The nephrologist will perform the procedure with the assistance of an imaging guide, such as a CT scan or an ultrasound machine to ensure the accuracy and precision of the biopsy. The patient will lie on his or her back. The site where the needle will be inserted is then prepared with an antiseptic and anaesthetic (the patient can also be placed under mild sedation). The patient will remain awake during the entire procedure, which takes around fifteen minutes.
A tiny incision will be made, which will serve as the entry point for the biopsy needle. The biopsy needle is spring-loaded and will require to be "fired" into the kidney to get tissue samples.
Once enough samples are taken, the nephrologist will apply pressure to the site before it is clean and dressed. Due to the small size of the incision at the biopsy site, no sutures are needed after the procedure.
Possible risks and complications
Serious complications caused by a kidney biopsy are rare, especially when the procedure is performed by a trained and experienced professional. However, the most common problem is bleeding within the kidney. This can be prevented by carefully evaluating and briefing the patient before the procedure.
- Lee YZ, McGregor JA, Chong WK. Ultrasound-guided kidney biopsies. Ultrasound Clin. 2009;4:45–55.
- Salama AD, Cook HT. The renal biopsy. In: Taal MW, Chertow GM, Marsden Pa, et al., eds. Brenner and Rector’s The Kidney. 9th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 28.