A general bloodwork mostly consists of 2 things: counting blood cells in “full” blood and measuring proteins/fats/ions/ … (biochemistry exam) in serum. Full blood is blood to which an anti-coagulant has been added, whereas this is not the case for serum. Serum is the clear liquid that is collected after the blood has coagulated and is spun at high speed.
A blood examination is done to detect anomalies that can point to a disease or indicate that certain procedures (such as anesthesia, surgery) should be avoided. This way, one can evaluate the bone marrow function, check whether the calcium values have increased (some malignant tumours are capable of extracting calcium from the bones leading to muscle cramps, heart arrhythmias and kidney damage). Blood values are regularly checked before and after treatment to make sure there are no complications and the treatment is safe (such as during chemotherapy and radiation therapy, but also during treatment with anti-inflammatory drugs, thyroid medication, antibiotics, etc).
Blood is taken from a vein: for this a small needle is inserted in a vein and the blood is collected in blood tubes. This usually takes less than 5 minutes.
The number and quality of circulating blood cells can be evaluated after blood collection:
Your veterinarian can deduct from the bloodwork whether your dog has anemia (a shortage of red blood cells), an infection (abnormal values of white blood cells), an inflammation (high values in white blood cells). Cancer patients can have an obvious tumour as well as a perfectly normal screening of the blood cells. On the other hand, dogs can develop cancer consisting of certain blood cells which can be detected via a blood sample, as is the case with leukemia. As a consequence of a tumour, the amount of certain blood cells (such as red blood cells) can be too low and this can be a clue for your veterinarian that a tumour is developing and possibly an indication to perform a bone marrow punction or other investigations.
The serum is used to determine e.g. proteins and/or hormones that represent the function of certain organs, such as the kidneys, the liver, the digestive system, the thyroid. Electrolytes, such as sodium, potassium and calcium can be determined as well in the serum. These values can be an indication that there are anomalies in certain organs that require further examination or indicate that certain procedures are not possible at the moment.
Certain tumours can be found spread in several organs (such as for forms of lymphoma, certain leukemias, histiocytic sarcomas and mast cell tumours). Their presence in multiple organs can lead to increased liver and/or kidney values as well as changes in protein and electrolyte levels linked to the digestive tract. Solid tumours can involve and impair the function of several organs due to their large size, thus leading to abnormal blood values. However, many patients with cancer will have normal blood values. In these cases, further investigation is advised via ultrasound or CT to track down anomalies in the organs that can eventually be biopsied and examined.
