This week, our mini-series is looking at the use of ultrasound in our feline friends, and specifically for use in the detection of Polycystic Kidney Disease (PKD). It is vitally important to understand how to diagnose this condition as failure to do so may result in eventual kidney failure.

The kidney is the organ responsible for cleaning out toxic products present in the blood, which are eventually passed out the body as urine. A previous article discussed a condition where this process was inhibited due to the generation of kidney stones and can be accessed here. However, what happens if a cat suffers from PKD?

PKD is a condition that affects cats from birth and can be characterised by the presence of cysts which are filled with fluid and are present in the kidney. The number of cysts present may vary, and may range in size. Imagine that these cysts are little balloons that live inside the kidney that over time may become increasingly inflated, therefore reducing the surface area of the actual kidney tissue. It is this process that is responsible for the kidney failure, as eventually there are not enough cells left to perform kidney function effectively. If the kidney only contains a few of these cysts its function may only be mildly affected and the cat may not fall ill from PKD or from kidney failure. Interestingly, despite the large variety of cat breeds, PKD is most prevalent in the Persian and Exotic Shorthair cats. Furthermore, although the cat is affected by PKD as soon as it is born, symptoms (such as an increase in drinking, and a decrease in appetite) may not typically reveal themselves until the cat turns 3 years old, or alternatively could be delayed until the cat reaches 10 years of age.

Now for the science-y bit. In their simplest form, genes are molecules in our body that can help to code for certain characteristics that we exhibit and can be passed down generations. There can be different variations of a gene, even though our body will as a general rule only end up choosing one. An example is our eyes – the gene that codes for the iris colour in our eyes can have 4 variations, namely blue, brown, green and grey. Nevertheless, most of us only display one eye colour, termed the ‘dominant’ gene, whilst the other colours fade into the background and can be termed ‘recessive’. In PKD, the gene responsible for this condition is the dominant gene, meaning that if this gene is present in only one of the parents, the resultant kitten will automatically suffer from this condition. It should be noted that this is only part of the story, as the way that genes are passed on is much more complex and is a discussion for another week!

So how can ultrasound help? Veterinary ultrasound imaging can aid in screening cats for the presence of PKD. As is always the case with ultrasound, the non-invasive nature of this method ensures minimal distress to the cat suspected of suffering from PKD, whilst the results are able to be analysed almost immediately following scanning.  Furthermore, ultrasonography can actually help to differentiate between cysts present in the kidney and other similar growths such as abscesses or kidney stones. Unlike with an X-ray, ultrasound can detect the presence of fluid, which is very important in conditions such as the occurrence of ‘water puppies’ in dogs that has been previously discussed. Dogs also form the focus for the next article in this mini-series, looking at the role ultrasound can play in canine Benign Prostatic Hyperplasia.