Dr Liesel van der Merwe is a small animal medicine specialist. Send her your questions: This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr Liesel van der Merwe

I sometimes see cases referred from other vets or as second opinions. These are accompanied by a letter outlining the history and the tests and procedures already performed as well as the medications administered.

This is vital to help me formulate a plan going forward as these results can guide me. If the tests were recently performed, I can use this information directly. Some systems change daily and a test performed one day may not be of any value in two days’ time. Additionally, medication could affect blood and urine test results, and this needs to be taken into account when interpreting results.

I may suggest additional tests and the client will say that the organ has already been tested and is normal. It is important to understand what a test can and cannot do. The liver, for example, is responsible for metabolising drugs, hormones and toxins. It also makes proteins and glucose, stores energy in the form of glycogen, and gets rid of waste products in the form of bile.

Routine liver tests evaluate the liver for damage to the cells, which could be caused by inflammation or toxin. The inflammation could be caused by infection or may be sterile. These enzymes in the blood are very non specific; they show that the liver is not happy, but they don’t tell you why. They may also be normal, even if the liver is damaged, because the liver is not actively damaged.

In liver cirrhosis, for example, there is much less normal functional liver tissue and the damaged cells have been replaced by scar tissue. In these cases the blood tests may be normal, but the liver is actually failing. We need to do special tests to see if the liver is working properly, including bile acids and testing protein, glucose and cholesterol. If we find that it is not working properly, or if the enzymes are very high, we still need to find out why this is happening.

Then we may do a liver scan (ultrasound) to look at the size and shape of the liver and gall bladder and check the blood supply. The liver may have cancer, an abscess, a blocked gall bladder, all of which will cause symptoms of liver disease. And even then these lumps in the liver could be normal old age changes. To ensure that the correct diagnosis is made a liver biopsy needs to be taken.

There are two ways of examining body tissues: a needle aspirate, which looks at a small number of cells; and a biopsy where a piece of tissue is taken, preserved in formalin, sliced ultra fine, and examined under a microscope. Biopsy gives you a definitive diagnosis, but a surgical procedure is required. An aspirate using a needle could be diagnostic in some cases and very non specific in others.

There is not one definitive test for any organ. Many clients will question additional testing. Ask your veterinarian which aspects of the disease or organ the tests will evaluate and which additional tests will be needed if results are inconclusive.

Diagnosing disease is a process which could cost a lot of money in more obscure conditions. The need for various alternative tests on an organ does not imply that your vet  is “experimenting” on your animal. We are administering or performing proven medications or diagnostic procedures, but we are not sure that the treatment will be 100% effective or that the procedure or test will give the answer. The test will help get to the answer, but it may just be another sign on the journey.

Ask questions. Make sure you understand why your vet is doing things. Take literature home, read it and ask questions the next day. An informed client is a co-operative and understanding client, communication is improved and the outcome is better.