Martha’s Laboratory Test Results

Great news for Martha!

Martha’s test results are back and I’m happy to report that our initial worries reported July 2, 2009 prior to testing were not confirmed.

Martha does have a couple of a common feline kidney problems. It is important to understand about kidneys that they have many, many functions. While we won’t go into a complete renal dissertation today, we will discuss how Martha’s two kidney issues are affecting her.

Recall that one of Martha’s complaints was drinking and urinating excessive amounts. Her blood and urine tests show that she is filtering waste products adequately from the bloodstream, and that she is not losing excessive amounts of important ingredients (like protein and sugar) into the urine. Such results are incredibly impressive for a cat who is 15 ½ years old.

She does, however, have a problem with water balance, leading to an abnormal test result called specific gravity. Specific gravity (SG) is a measure of how dilute or concentrated one’s urine is. Let’s look at two scenarios:

  1. It’s Super Bowl Sunday. You’ve invited friends over and you’ve made a huge pitcher of iced tea. Everyone is excited about the game and seeing all of their friends and drinking tea without paying attention to just how much they’re drinking. Pretty soon they have to go to the bathroom to urinate because the body senses that there is a lot of fluid coming in, much more than the body needs. The resulting urine is very dilute or has a low specific gravity.
  2. You are crossing the Mojave Desert in your Range Rover. The vehicle breaks down, and you set out on foot to get help, canteen in hand. Eventually your canteen is empty and your body recognizes that there is no new fluid coming in. Still, it knows that waste products must be removed from the body, so it makes a very small volume of urine with a large amount of waste products. The resulting urine is very concentrated or has a high specific gravity.Specific gravity  can range from about 1.004 to over 1.060. The SG of plain water is 1.000. Normal urine SG for cats is between 1.015 and 1.060. A patient’s kidneys’ ability to maintain proper water balance is determined by simulating “desert” conditions as in Scenario 2, above. Water is withheld for 12 hours prior to the test. If urine SG fails to reach normal levels we know that the kidneys have lost their ability to concentrate urine. Suffering from this condition a patient not taking in fluids would quickly become dehydrated, as the body would not stop producing low specific gravity urine.

Such is the situation Martha finds herself in. While her SG is 1.015, just inside the normal range, any feline patient whose SG is lower than 1.025 is going to be experiencing high water intake and output. The only significance of low SG is that we will be filling water bowls more often and scooping urine clumps out of the litterbox more often. If kidney filtration function is good, but specific gravity is low, the applicable term is “glomerulotubular imbalance.”

Martha also has urinary tract infection (UTI).  The microscopic portion of her urinalysis shows that she has rod-shaped bacteria causing the infection.  Rod-shaped bacteria differ from cocci or round bacteria both in shape and likelihood for resistance to various antibiotics.   This is potentially a serious issue for Martha, especially if the kidneys are infected and not just the urinary bladder.

We will submit a urine bacterial culture and sensitivity, a two-part test that first grows the bacteria causing the infection and identifies the causative agent, then subjects the bacteria to a number of different antibiotics to determine which one(s) will kill the organism.  Those that are ineffective in the laboratory will likely be ineffective in the body, too, and therefore will not be used.  Those that did kill the organism in the laboratory have a high likelihood of being effective in the body and we will select a first antibiotic from that list.

Martha’s other test abnormality is probably also a function of old kidneys: anemia. Kidneys produce a bone marrow-stimulating hormone called erythropoietin. As kidneys get older they become smaller and produce less erythropoietin. Therefore less bone marrow stimulation occurs and fewer red blood cells are produced. To correct the anemia we will start with administration of a hematinic. If that does not resolve the problem we will pursue other methods of bone marrow stimulation.

Your pet’s doctor can provide injections of Erythropoietin to supplement what the body produces.

Martha’s other complaint was weight loss. Upon disconnecting her automatic feeder so that she would have a 12-hour fast her for blood and urine testing, I discovered that a diet change I had recently made had resulted in a reduction of the feeder’s output. Upon receiving her test results I have increased her feeding allowance slightly and expect her weight to return to normal.

Martha is fortunate to have a mid-normal blood glucose (sugar), which means she doesn’t have diabetes, and a thyroid hormone level of 2.6, which means she doesn’t have hyperthyroidism.

Still, a 2.6 thyroid reading is above the midrange of normal, which means followup testing will be in order to see if her number rises. Cats above age eight are predisposed to hyperthyroidism.

My wife, Brenda, and I breathed a sigh of relief after reading these results.

If there are changes in Martha’s health we will keep you updated.

