The kidneys have become greatly enlarged due to infiltration of neoplastic lymphocytes.
To help you get your bearings - the kidneys are the white masses near the mahogany liver.
Bilateral means affecting both sides and is usually used in reference to something which occurs on both sides of the body.
For example, you would not say "There is bilateral cystitis" as this would imply that the animal has TWO urinary bladders and that both of them are inflamed. However, you could say "There are bilateral corneal ulcers" as most animals have two eyes. However, if you happen to be treating a cyclops, this of course does not hold true...
Since both kidneys are involved in the above patient, we say that the lesions are bilateral as opposed to unilateral in which only one side is involved.
Fatty Liver - Feline
"Fatty liver" is a term used to describe a liver that contains more visible lipid (fat) than one would normally expect to see in a liver.
Livers may become fatty as a result of a disease process (e.g. diabetes) or a physiologic process (e.g. pregnancy).
Cats can develop fatty livers when they are overfat and then fast or are nutritionally stressed. Fat is mobilized for energy as triglycerides and accumulates diffusely in the hepatocytes. The lipid is visible grossly as a diffuse, yellow discoloration to the liver.
The word diffuse implies that the condition or substance is spread widely throughout the tissue and is not localized to a focal area. Diffuse also implies that the distribution is somewhat uniform or even.
Click on the photo to see an enlargement clearly showing the diffuse, pattern of fat accumulation in this liver.
Renal Adenoma - Horse
The yellow mass is a benign tumor of renal tubular epithelial cells (an adenoma) in the kidney.
You can see that there is just the one tumor on the kidney. There are no "satellite" tumors surrounding the adenoma - the lesion is clearly focused into one area of the kidney. Hence we call this a focal lesion.
Hemangiosarcoma in a 12 y.o. Male mix-breed dog
The multifocal red and block dots scattered throughout this section of a dog's brain are metastatic lesions from a primary hemangiosarcoma of the spleen.
The tumors are not of uniform size and are not evenly spread throughout the brain - so you can't really say the tumors are spread diffusely through the brain. The distribution is more multifocal and somewhat random.
You could say this brain has multiple, randomly distributed, metastatic hemangiosarcomas of varying size.
Click on the photo to see a close-up of the central portion of this section of brain.
Patchy implies that the distribution of the lesion is uneven, somewhat diffuse and multifocal. That is, the lesions occur in indistinct patches in scattered places on the organ.
If the lesions were well-defined, the distribution would be multifocal, not patchy. Do you see the difference?
Let's compare patchy to some of the other distribution and location terms you've learned:
- Focal means the lesion is in one well-defined (focused) location.
- Multifocal means the lesions are in defined areas (foci) but there are multiple foci on the organ.
- Diffuse, on the other hand, means the lesion is not focal and is spread evenly throughout the organ.
- Patchy means the lesion is not focal and is spread unevenly, in patches throughout the organ.
- Adrenal Adenoma and Atrophy
Are you ready for a biochemistry flashback?
In this specimen, there was a functional tumor involving only one of the two adrenal glands. The tumor secreted glucocorticoids which elevated plasma levels of the hormones.
The elevated glucocorticoid levels then activated the hypothalamic-pituitary axis negative feedback system which in turn caused the hypothalamus to decrease its production of ACTH. The lowered levels of ACTH then caused the contralateral adrenal gland to atrophy due to lack of stimulation by ACTH.
Phew! Got that?
So what does that mean?
It means we see a very large, neoplastic adrenal gland on the ipsilateral side (the same side as the tumor) and a very small, atrophied adrenal gland on the contralateral side (the side that does not have the tumor).
Unilateral means "affecting only one side" and since only one gland of the pair is neoplastic, we say there is unilateral neoplasia. Similarly, only one adrenal gland is atrophied. So we would say there is unilateral atrophy.