What is a kidney (renal) biopsy?
A kidney biopsy is an important but invasive procedure with pros and cons, which we will now go through. Its normal to be a little anxious
But what is it? It’s a procedure to take a sample of kidney tissue, about the size of a small pin, which is examined under the microscope.
Why do I need a kidney biopsy?
You may need a kidney biopsy if you have:
- A significant reduction in kidney function – either short term (AKI) or long term (CKD). This is especially true if the doctors suspect a problem with the glomeruli of the kidney
- A high level of protein in the urine (proteinuria)
- A kidney transplant that is not working properly ..
.. and the diagnosis cannot be made by blood tests or an ultrasound scan.
How do I prepare for the kidney biopsy?
Most kidney biopsies are done as a day case procedure. You will need to have some blood tests done beforehand to ensure it is safe to go ahead with the biopsy. You may need to attend the hospital for these. Some biopsies are done as an inpatient.
If you take any blood thinning medicines, these must be stopped at least a week before the procedure, and your kidney doctor will discuss this with you. On the day of the biopsy take all other medications as normal.
Bring any medication that you take regularly. It is important that your blood pressure is well controlled to be able to go ahead with the biopsy. If your blood pressure is too high (it should be 140/90 or lower) on the day the biopsy is planned, the biopsy will be postponed.
Do not drive on the day of the biopsy.
What will happen?
The doctor will discuss how the biopsy will be done, the risks involved and ask you to sign a consent form.
The kidney biopsy is usually performed in the x-ray department. You will be asked to lie on your front and a pillow may be placed under your stomach to help in the procedure. The doctor will do an ultrasound scan to check the position of your kidneys, and allow the him/her to choose a site from which to take the biopsy.
Either kidney may be biopsied, though it is more commonly the left one. You will be covered with sterile towels. The skin will be cleaned and numbed with an injection of local anaesthetic into the skin over your kidney. There may be some slight discomfort. Once the skin is numb, a biopsy needle is inserted through the skin to take the biopsy. This may be repeated 1-2 times.
You will be asked to take a breath in and hold your breath so that your kidney does not move. Most people feel only a pushing sensation. Afterwards a plaster is placed over the site and a further scan of the kidney is done to check for any bleeding.
A kidney biopsy being performed
You will then have 6 hours bed rest. You will be encouraged to drink. You will need to use either a urine bottle or a bedpan to pass urine. The nursing staff will check your pulse and blood pressure regularly. If you have any bleeding you will be seen again by the doctor and receive treatment if needed. Most patients go home the same day.
What happens afterwards?
Biopsy results take at least 2 weeks. Very specialist tests from the biopsy can take longer. Results will be discussed at your next clinic appointment.
If you get any discomfort from the biopsy site, you should take paracetamol for 24-48 hours after the biopsy. Aspirin or anti-inflammatory agents (tablets or gel) such as ibuprofen should be avoided.
You should not drive for 2 days and should avoid any heavy lifting or strenuous exertion for 10 days. You can shower or bathe as normal. If you notice any blood or clots in your urine, feel any new or severe back pain, or become faint after you have gone home, you should attend your local A&E immediately.
The slides that are made from the biopsy are kept indefinitely in the Pathology Department in case we need to refer to them for comparison with other biopsies in future years.
What are the risks of a renal biopsy?
Renal biopsies are not without risk. Fortunately serious complications are extremely rare. Most risks are to do with internal bleeding after the biopsy. You will be observed very closely so any bleeding is detected and treated early.
Common risks
- Mild discomfort over the biopsy site, which can be treated with pain relief, e.g. paracetamol
- 1 in 10 chance of minor bleeding with blood in the urine may occur after a biopsy – this usually settles quite quickly
- I in 20 chance of failure of the biopsy to obtain sufficient kidney tissue to make a diagnosis. It will usually need to be repeated
- 1 in 50 chance of a collection of blood around the kidney (bruise-haematoma), which can cause discomfort, but usually settles on its own.
Unusual risks (1 in 100 or less)
Heavier bleeding requiring the need for a blood transfusion, or an x-ray treatment (embolisation) to stop a bleeding blood vessel
Rare risks (1 in 1000 or less)
- More severe bleeding requiring an operation including removal of the bleeding kidney, leading to ..
- Kidney dialysis – that can be permanent, or
- Death.
What increases the risk of bleeding after a renal biopsy?
Several factors are know to increase the risk of bleeding:
- Age
- Small kidneys (one or both is less than 10cm long)
- High blood pressure – especially if 150/95 or higher
- Drugs to thin the blood
- Bleeding disorders.
Note. If you have one or more of these risk factors, it is important to question your kidney doctor as to whether the risks of bleeding outweigh the possible benefits.
Should I have a kidney biopsy if I only have one kidney?
No, not usually. Having a single kidney may not increase the risk of bleeding. But if we need to remove the kidney after extreme bleeding, this is a disaster – as it will obviously put you on permanent dialysis. The doctors will need an extremely good reason to recommend a kidney biopsy in this situation.
Summary
We have described a kidney (renal) biopsy. They are nothing to be frightened of. Most go well, with no complications.
Other resource
There is more information on renal biopsy written by the renal team at UHCW Coventry.
Last Reviewed on 30 April 2024