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© Dirk Biddle
Kidney (or renal) biopsies usually are done to check for signs of damage from a disease such as lupus or to evaluate a transplanted kidney. If a necrotising vasculitis condition involving the kidneys is suspected (eg; Polyarteritis Nodosa, Henoch-Schönlein purpura, Churg-Strauss syndrome, IgA nephropathy- Berger’s disease) - for example where blood (haematuria), protein (proteinuria), or excessive waste products are found in the urine and after other less-invasive tests for kidney disease (such as blood and urine tests, ultrasound, or a CT scan) have failed to diagnose a kidney problem clearly, or to define its severity - a kidney biopsy may be recommended. A kidney biopsy is usually done by passing a needle through the back and withdrawing a small amount of kidney tissue for examination. The procedure is termed percutaneous (performed through the skin) fine needle aspirant and usually takes between 30 minutes to one hour to perform.
The patient, usually under light sedation, lies face down with a pillow under their stomach. The exact position of the kidney will be found using an ultrasound and the surgeon will clean and mark an area on the lower back above the kidney. A local anaesthetic will then be injected into the skin. After the skin becomes numb, more anaesthetic is then injected around the kidney. It is particularly important that the patient follow the surgeon’s directions about breathing and keeping still while the test is being performed, as the kidney moves during breathing.
The surgeon will then use a locating needle, guided by ultrasound, to locate the correct position. This will be followed by a collecting needle to gather the required tissue. A small “popping” sound or sensation may be felt by the patient as the needle enters the kidney. An intense and sudden pinching sensation may also be felt as the biopsy sample is taken, however this will last only a second or two. Three or four passes will be needed to gather some cores of tissue, each about 1 to 2 cm long (about half a matchstick in size), from predetermined regions in the kidney. Pressure will then be applied to the site for several minutes to stop any bleeding before a bandage is applied.
Some patients however, may not be able to undergo this procedure if they are prone to bleeding. Thus another, more invasive but less risky, method to gain some biopsy tissue is for the surgeon to make an incision in the back to expose the kidney and remove a “wedge” of tissue. This procedure is carried out with the patient under general anaesthetic. An adequate renal biopsy should contain at least 6 glomeruli so that there is less chance that focal lesions will be missed. Unfortunately, about 20% to 30% of the time, the results of a kidney biopsy are inconclusive and a repeat biopsy is needed (1).
After the procedure the patient will be told to lie on their back for 12 to 24 hours and it is normal to experience some mild pain in the area for 2 to 3 days after. It is also normal for there to be some bright red blood in the urine up to 24 hours after the procedure. Due to the small but significant risk of bleeding, the patient is usually kept under observation in hospital for up to 48 hours following the procedure. During this time the patient’s blood and urine will be monitored (as well as their blood pressure and heart rate) to detect any problems such as bleeding. In rare cases a blood transfusion may be necessary if bleeding does not stop on its own.
An alternate renal biopsy method is termed trans-jugular renal biopsy. A needle is inserted through a catheter that enters the patient’s jugular vein at the neck, the area first being numbed with local anaesthetic. The needle threads down through the catheter to the kidney in order to obtain tissue from the inside without puncturing the outside of the kidney.
Following a renal biopsy procedure, a pathologist will look at the kidney tissue samples to check for unusual deposits, scarring, or infecting organisms that might explain the patient’s condition. A biopsy may also indicate how quickly a disease is advancing. The small piece of kidney tissue which is obtained usually measures 1 to 1.5 cm in length and about 2 mm in width and is cut into smaller pieces for examination using various stains. Several tests are run on the tissue including immunological tests, immunofluorescence tests, staining with various stains such Trichrome, silver, etc, and also taking pictures under an electron microscope, which provides highly magnified pictures of the cells.
Traditionally, attention is focused on the extent of active lesions in a renal biopsy, in order to determine the severity of renal disease and its implication for renal outcome. Because of their significant impact on renal function, combined with their easy recognition, the use of the percentage of normal glomeruli in an adequate biopsy is also utilised in predicting the renal function of patients with systemic vasculitis (2).
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1) http://my.webmd.com/hw/kidney_failure/hw231586.asp
2) Bajema I, Hagen E, Hermans J, Noel L, Waldherr R, Ferrario F, Van Der Woude F, Bruijn J. (1999) Kidney biopsy as a predictor for renal outcome in ANCA-associated necrotizing glomerulonephritis. Kidney International, 56(5), 1751-1758. (Comment in: Kidney International. (2000). 57(5), 2173)
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