Kidney Problems in Dogs

Causes
Causes of nephropathy include administration of analgesics, xanthine oxidase deficiency, and long-term exposure to lead or its salts. Chronic conditions that can produce nephropathy include systemic lupus erythematosus, diabetes mellitus and high blood pressure (hypertension), which lead to diabetic nephropathy and hypertensive nephropathy, respectively.

Analgesics
Main article: Analgesic nephropathy
One cause of nephropathy is the long term usage of analgesics. The pain medicines which can cause kidney problems include aspirin, acetaminophen, and nonsteroidal anti-inflammatory drugs, or NSAIDs. This form of nephropathy is "chronic analgesic nephritis," a chronic inflammatory change characterized by loss and atrophy of tubules and interstitial fibrosis and inflammation (BRS Pathology, 2nd edition).
Specifically, long term use of the analgesic phenacetin has been linked to renal papillary necrosis (necrotizing papillitis).

Over the last few weeks, your nine year old Bullmastiff girl has been on your mind. She is drinking more then normal and asking you in the middle of the night to let her out to urinate. That in itself is not the worry; it is the weight loss and overall lethargy that has you really concerned. The last straw was when she started vomiting – you had her into the vet the next morning for a full work up but his diagnosis floored you! How could she have chronic renal disease? How could her kidneys be so far gone and you never noticed until now?

The early stages of renal disease are hard to notice as many of the symptoms are mostly benign and can be written off as advancing age. Symptoms include:

Drinking excess water
Frequent urination
Urine will not concentrate so it is pale in color with hardly any odor
Leaking urine (more common in females)
Vomiting
Weight Loss
Anorexia
Lethargy
Muscle Weakness
And, once blood and urine samples are run, the doctor will find:

An elevated blood urea nitrogen (BUN) and creatinine
High levels of protein in the urine
Urine does not concentrate
Most owners do not notice the decline in their pet until the vomiting begins and the dog is off their food. When a dog with usually an unstoppable appetite suddenly will not eat their favorite food, alarm bells go off the unsuspecting for owners. Unfortunately, by the time symptoms begin to show, the kidneys are already working at below twenty-five percent of full function, making the alarm bells ring for the vet!

Our kidneys are the filtering system for our blood. They also produce hormones that stimulate red-blood-cell production, help regulate calcium, magnesium and phosphorous levels and keep our blood pressure within normal parameters. Kidneys are filled with thousands of tiny funnels called nephrons that work to filter and balance fluid levels in the body. When they do not work right, it affects our entire bodies, not just our urine output. Thankfully nephrons are hardy and the canine, as well as human body, come with an overabundance of these microscopic funnels and it is not until the level of functioning nephrons drops below 25% that they no longer can keep up with the physical demand of clearing out the blood of toxins and maintaining a correct fluid balance. As the level of functioning nephrons drop, the remaining nephrons cannot compensate and symptoms develop. Although, if the disease progressed slowly enough, the remaining nephrons can adjust to the higher demand placed on them.

There are two types of renal disease – chronic and acute. Chronic is the slow onset of the disease usually caused by old age and although it is not entirely reversible, the progress of the disease can be reversed to a point, slowing down the decline tremendously. Acute renal disease is usually caused by trauma, poisoning, infection, cancer and auto-immune diseases but many disorders can negatively affect the kidneys. If an animal survives a traumatic incident such as being hit by a car or falling, the next big hurdle is surviving the damage done to the kidneys when the animal went into shock. Shock kills more animals then anything else once they survive the initial incident. Reversing acute kidney failure is possible although not always, it depends on the severity of the disease and how quickly the correct treatment was implemented.

Although there are many toxins that cause acute renal failure, the most commonly seen poisonings are ethyleneglycol in antifreeze and calciferol in rat poison. As little as a teaspoon of ethyleneglycol-based antifreeze causes crystals to form inside the nephrons, shutting down renal function entirely. This is normally fatal unless treatment begins immediately i.e. owner induces vomiting after witnessing the animal lick the antifreeze. Calciferol increases the level of calcium in the body, allowing mineral deposits to develop, damaging the kidneys. There are also medications and treatment for other diseases that can damage the kidneys so always check with your veterinarian before administering anything to your pet.