What I'm Learning This Week

This weeks Problem Based Learning Case is really interesting. It's a 16 year old male, neutered domestic short hair cat named Rambo. Rambo presented with inappetance and losing weight over several weeks duration. In recent weeks he has also become PU/PD (drinking a lot of water and peeing a lot). His owner has brought him in because he has stopped eating, drinking, urinating and defacating the past 2 days. So far we have submitted and are awaiting results of a full blood profile and urinalysis along with a urine culture and sensitivity (results will be back tomorrow). In the meantime we have taken survey radiographs and noticed that his kidneys are smaller and irregularly shaped. Also their are crystals on the radiographs that appear to be nephroliths and ureterliths. So far I am guessing that this is a case of Chronic Renal Failure (CRF). CRF is one of the most common diseases to affect older cats. The bloodwork results that I get tomorrow will hopefully confirm my presumed diagnosis.
I have spent the past 2 days learning all about renal physiology (how the kidneys function) and researching how I should treat Rambo if indeed this is CRF. On physical examination Rambo was 10% dehydrated, so I have also been researching what type of fluid therapy would be appropriate in this situation. One of the things that I have found really interesting so far is that dehydration causes a decrease in tubular flow rates which would then result in increased Blood Urea Nitrogen(BUN), even before glomerular filtration rate is decreased. Basically what I've learned is that the BUN can be falsly elevated due to dehydration and that CRF patients may have a better prognosis then I would originally expect by just looking at the BUN alone. From what I've read so far, you should first re-hydrate the patient and then re-evaluate the bloodwork to truely measure the kidneys ability to remove urea from the blood and to give a correct prognosis. Interesting stuff, hugh?