August 2005 Issue

Featured Case Study: nine-year-old DSH female cat, Muriel Jones
Dennis B. DeNicola, DVM, PhD, DACVP

Presentation

Patient—Nine-year-old DSH female cat

Presenting Complaints—Mild PU/PD, intermittent vomiting sometimes containing hair, weight loss

Physical Exam—Moderate dental tartar, unkempt coat, evidence of diarrhea on tail, tachycardia, dehydration and palpable thyroid nodule

Interpretive Summary

Hematology
There is minimal polycythemia that is most likely relative polycythemia related to the dehydration identified on physical examination. Leukocytes are high normal in number; however, there is a mild mature neutrophilia (no immature neutrophil forms were identified during microscopic evaluation of the blood film). Lymphocytes are on the low end of the reference range. This leukocyte pattern is most likely associated with a glucocorticoid response ("stress"); however, mild inflammation may be present also.

Clinical Chemistry Profile
There is a mild azotemia (minimal increase in BUN and creatinine), indicating minimal decreased glomerular filtration rate (GFR). In face of the mildly concentrated urine (urine specific gravity = 1.045), prerenal azotemia is most likely, which is compatible with the clinically identified dehydration. The slight increase in ALT and ALKP indicate minimal hepatocellular injury and cholestasis, respectively. Although the sodium and chloride are within reference range limits, the relative decrease of chloride compared to sodium suggests chloride loss or sequestration; loss associated with the intermittent vomiting is most likely, and metabolic alkalosis should be considered. Complete electrolyte profile evaluation, including measurement of TCO₂ and calculation of the anion gap, will help further characterize any underlying metabolic acid-base disturbance. The finding of even a very slight hypokalemia in a cat with evidence of decreased GFR is of concern and potential significant decreased body stores of potassium should be considered. Serial potassium measurements are warranted as the dehydration is corrected and GFR returns to normal. Hypokalemia can occur with many feline diseases, including CRF (chronic renal failure) and hyperthyroidism. Total T₄ in markedly elevated and hyperthyroidism is likely, especially considering the associated polycythemia, azotemia and elevated liver enzymes.

Urinalysis
Urine specific gravity is mildly concentrated and is compatible with the clinical identification of dehydration. The urine protein:creatine ratio is moderately elevated, especially in light of an inactive urine sediment (no blood or inflammatory cells or other formed cellular elements present).

Radiography
Mild cardiomegaly is present, characterized by biatrial enlargement. This is recognized on the VD view (valentine heart). Nuclear scintigraphy shows a right-sided, unilateral lesion, which is less common than a bilateral lesion in feline hyperthyroidism.

Additional testing
Blood pressure systolic 180 mm/Hg—if repeatable, consistent with mild hypertension.

Diagnosis
The clinical diagnosis is hyperthyroidism with likely concurrent chronic renal disease.

Treatment/Plan
Hyperthyroidism can increase cardiac output, decrease peripheral vascular resistance, increase renal blood flow and increase GFR. This chain of events can not only decrease BUN and creatinine, but also perhaps lead to glomerular hypertension and hyperfiltration, thereby potentially inducing or worsening concurrent renal disease.

Systemic hypertension, as well as secondary renal disease, can be associated with hyperthyroidism. Monitoring patient urine protein:creatinine (UPC) values can be of great benefit in these cases, especially when assessed with serial blood pressure measurements. With successful treatment of hyperthyroidism (radioactive iodine, methimazole, thyroidectomy), the UPC may return to normal or may worsen if CRF is progressive. Careful monitoring of this patient is recommended.

The recommendations contained in Diagnostic Edge educational materials are intended to provide general guidance only. As with any diagnosis or treatment, you should use clinical discretion with each patient based on a complete evaluation of the patient, including physical presentation and complete laboratory data. With respect to any drug therapy or monitoring program, you should refer to product inserts for a complete description of dosages, indications, interactions and cautions.

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Chose from two urinalysis options from IDEXX Laboratories for more insight into your patient's renal status

1. In-house: The IDEXX Urine P:C Ratio for the VetTest® Chemistry Analyzer The first in-house fully quantitative test for early detection of renal disease. It consists of two slides: urine protein (UPRO) and urine creatinine (UCRE). The urine protein:creatinine ratio is the gold standard in testing for proteinuria, and the IDEXX Urine P:C Ratio is the only in-house fully quantitative measurement of urine protein loss. You now have the ability to diagnose early renal disease and better assess your monitoring and treatment protocols—quickly and efficiently, in-house.

2. IDEXX Reference Laboratories: Our urinalysis results include a proteinuria confirmation using the sulfosalicylic acid (SSA) precipitation test—at no additional charge.*

The SSA test measures
all fractions of protein in urine, rather than just albumin. As a first step, a positive SSA screen semi-quantifies proteinuria and provides an early warning to alert you of potential renal damage.

Once proteinuria is found in the SSA screen, localization, proof of persistence and tracking of trends can be performed via the urine protein:creatinine (UPC) ratio.

The UPC ratio offers a technique to fully assess proteinuria in dogs and cats. The UPC ratio can:

• Confirm screening tests

• Quantify protein loss

• Monitor disease progression

• Evaluate therapeutic response

If your urinalysis produces a positive SSA result, you have two options for adding a UPC test:

• Automatic UPC test, if indicated • Test Code 950
  
  

  When you request this test along with any urinalysis, IDEXX will automatically run and report a UPC ratio on every sample with an indicative SSA value and an inactive urine sediment. When you order this test, you will receive a UPC result and you will be charged only when this test is run. You may want to consider whether you will need to charge your clients up front or wait to see if the test is run before charging the fee for this test.

• You decide when to add a UPC test • UPC add-on—Test Code 997
  
  

  IDEXX includes a note in your report whenever the SSA test indicates abnormal levels of proteinuria, indicating the need for an add-on UPC test. Call us within two days of submitting your sample and add the test, or add this test to any urinalysis or profile at the time of your order.

Get the most out of every urinalysis with IDEXX’s full-service reference laboratories’ comprehensive results, and take advantage of these urinalysis testing options today!

For more information, call us at 1-888-433-9987.

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Getting the Message Out About Heartworm and Lyme Diseases

Simple steps to educate clients

Educating clients about heartworm and Lyme disease and how these diseases endanger the health of pets is a good first step toward motivating clients to bring their pets in for annual testing and vaccinations.

Many practices send reminders for these warm-weather diseases. However, these reminders are only sent to clients with pets that have previously received a heartworm test or Lyme vaccination at the practice. This leaves a substantial group of clients with pets who do not regularly receive information about heartworm or Lyme disease. How do you let these clients know about the importance of an annual heartworm test? Here are some suggestions.

• Mass mailing. Send an informational letter to all canine pet owners alerting them to the increased threat of heartworm and Lyme disease during the summer months. Create your own informational letter or use preprinted educational heartworm letters available from IDEXX Computer Supplies
  (1-888-224-4408).

• Newsletter or Web site. If your practice has a newsletter or Web site, use it to publicize the dangers of warm-weather diseases.

• Telephone message. If your practice uses a recorded phone message that plays when clients are waiting for an answer or are on hold, add a statement about the importance of a heartworm test and vaccinating to prevent Lyme disease.

• Invoice/Statement message. Change the message lines that print on your invoices and statements to "Make a heartworm appointment to prevent this deadly disease in your canine companion," or a similar message for Lyme disease.

Raising your clients' awareness of heartworm and Lyme disease helps your clients understand the importance and value of annual testing and vaccinations.

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Education and Events

We offer a variety of seminars and teleconferences about emerging trends and best practices in veterinary diagnostics—in a forum designed to involve, educate and motivate you and your staff.

Here are some of the educational events in August

• The Most Commonly Misdiagnosed Diseases in Veterinary Medicine by Fred Metzger, DVM, DABVP
• Bridging the Gap: Assessing the Anion Gap and Acid-Base Imbalances presented by Dennis DeNicola, DVM, PhD, DACVP with Kristen Hibbetts, DVM, DACVIM, DACVECC and Peter Kintzer, DVM, DACVIM

Visit the seminar and teleconference calendar, click the date to view the details, fill out and submit the form to register.

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Helpful Hints on Ammonia Tolerance Testing
by Dennis B. DeNicola, DVM, PhD, DACVP

The IDEXX VetTest® NH₃ slide can be used to assess liver function. The following are a few helpful hints on how to get the most out of this test:

• WORK FAST! Ammonia is not a very stable compound so you will have to work fast and plan ahead. Make sure the VetTest® Chemistry Analyzer is available and do a quick and clean blood draw. Spin down the blood immediately in a lithium heparin tube and run the plasma sample as soon as possible.
• If there is going to be a delay, cap your sample and place it in an ice bath.
• Minimize the exposure of the blood and plasma to room air whenever possible.
• Never perform an ammonia tolerance test if the baseline ammonia concentration is elevated. Liver function is compromised when the baseline ammonia levels are elevated.
• If doing an ammonia tolerance test, try administering the ammonia in something that will help mask the smell and taste. Also consider giving the ammonia rectally instead of orally—it is often faster and easier.
• Don’t run your ammonia test with the BUN and Total Protein slides as they can potentially interfere with the results.
• In people, headaches are the first sign of hepatic encephalopathy and are often the presenting complaint. Since we can’t tell when our patients have painful headaches, consider running an ammonia plasma concentration test to monitor all patients at risk for developing hepatic encephalopathy.

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Can you identify these cells?

Test your hematology knowledge by trying to identify the three nucleated cells in the picture below. History: blood film from a clinically normal two-year-old male guinea pig.

The first 10 respondents to name all three correctly will receive a complimentary issue of the popular IDEXX Laboratories Guide to Hematology in Dogs and Cats.

Respond by sending an e-mail to: diagnosticedge@idexx.com.
Please include your name, practice name, address and telephone number.

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July Survey Results— Here is what you said...

1.	What is the primary reason you attend a veterinary conference?
2.	Which criteria influence your decision about which conference to attend?
3.	What's the most important criteria you use when evaluating the experience of attending a conference?

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