Featured case study:
9-year-old spayed female cocker spaniel, Milly
Submitted by Mary Lindsay, DVM, Westfield Veterinary Group and Wellness Center, 562 Springfield Avenue, Westfield, New Jersey

Physical examination
Other than age-related bilateral nuclear sclerosis and mild bilateral chronic otitis, Milly was in good body condition with no abnormal physical examination findings.

Differential diagnoses
Diabetes mellitus, diabetes insipidus (central or nephrogenic), chronic renal failure, glomerular disease, glomerulonephritis, amyloidosis, hyperadrenocorticism, psychogenic polydipsia with medullary washout and pyelonephritis were all considered as differentials for the PU/PD. Neurogenic (upper motor vs. lower motor neuron) and nonneurogenic incontinence (hormone-responsive incontinence, urge incontinence) were also considered as contributors to the urinary accidents as were transitional cell carcinoma, vaginal or urethral mass and urinary tract infection.

Diagnostic plan
A complete blood count (CBC), general chemistry profile, complete urinalysis with urine culture and sensitivity were performed to screen for metabolic, infectious and inflammatory disease and to potentially characterize primary and secondary organ involvement.

Laboratory data

Erythron—The minimal elevation of MCHC supports the potential of cell-free hemoglobin due to in vitro or in vivo hemolysis.

Leukon—All parameters are within reference-interval-limits; however, the lymphocyte count at the extreme low end of the reference interval is highly suspect for an underlying glucocorticoid influence (stress).

Thrombon—There is a minimal and insignificant thrombocytosis present.

Blood film review—No significant morphologic abnormalities are noted in any cell line.

Clinical chemistry

Kidney panel—There was a increase in the BUN without an increase in creatinine suggesting nonrenal causes, including gastrointestinal bleeding and/or recent high-protein diet. Although there is no support for decreased glomerular filtration because of the
within-reference-interval creatinine, the potential for underlying renal disease should be maintained in the differential because of the nonconcentrated urine specific gravity. Serial laboratory profiling for renal disease (clinical chemistries and urinalyses) should be considered for further evaluation. There was evidence of significant proteinuria, and since there was no evidence of active inflammation or sediment changes explaining this proteinuria, renal proteinuria was indicated. A urine protein:creatinine ratio (UPC) was determined to quantify the degree of proteinuria and provide baseline values for trending over time during case management and reevaluation.

Electrolyte Profile—The finding of moderately increased potassium and a mild decreased sodium:potassium ratio (23, reference interval > 27) warrants investigating a series of possible causes. Differentials for decreased sodium:potassium ratio include hypoadrenocorticism, chronic renal failure, intestinal parasitism and thrombocytosis with potassium release from platelets. If Milly were an Akita or other Japanese canine breed, the potential of hemolysis and release of intracellular potassium from erythrocytes would have been considered, since these breeds have a relatively high intraerythrocyte potassium concentration compared to others. Since there was no laboratory support for renal failure, there was no significant thrombocytosis. Because Milly was not a breed of dog with high intraerythrocyte potassium concentration, investigating hypoadrenocorticism was warranted even though there was evidence of a glucocorticoid influence in the CBC. An adrenocorticotropic hormone (ACTH) stimulation test was performed to screen for hyperadrenocorticism and rule out hypoadrenocorticism.

Additional diagnostics

Abdominal Ultrasound—The kidneys were found to have abnormally increased echogenicity and there were multiple smoothly marginated anechoic cysts present in the cortices of both kidneys. Renal corticomedullary definition was bilaterally reduced. These changes were consistent with chronic immune-mediated or infectious renal disease. The right and left adrenals were of normal size, shape and echogenicity.

Diagnostic summary
An ACTH stimulation test, with pre-ACTH and post-ACTH cortisol levels
within-reference-interval limits, while ruling out hypoadrenocorticism, does not rule out hyperadrenocorticism as approximately 40% of dogs with hyperadrenocorticism will have within-reference-interval results.¹ The finding of normal-appearing adrenals on the abdominal ultrasound in this patient makes pituitary-dependent hyperadrenocorticism unlikely and rules out an adrenal tumor. Proteinuria may be due to prerenal, renal and postrenal causes. Prerenal causes of proteinuria due to increased glomerular permeability, including shock, heart disease, fever and strenuous exercise, have been excluded as likely causes in this case because of the clinical presentation and physical examination findings. Overflow proteinuria where high concentrations of low-molecular-weight proteins in the peripheral blood are filtered and not reabsorbed, including hemoglobin, myoglobin and Bence Jones proteins, has been considered unlikely, again because of clinical presentation and laboratory data evaluation. It should be remembered that Bence Jones proteins commonly do not react with dry-reagent urinalysis strips, which results in a negative protein result or only minimal positive protein even in the face of marked proteinuria. Postrenal causes of proteinuria, such as urinary tract infection, calculi and masses, have also been eliminated as possibilities because of the findings on ultrasound and urinalysis. This proteinuria is best characterized as renal in origin, and given Milly’s previous history of IMHA, the potential of antibody/antigen complex deposition within glomerular membranes and subsequent glomerular damage would have to be strongly considered as an underlying mechanism. Recent studies have shown that protein loss through damaged glomeruli also results in damaged proximal and distal renal tubules resulting in end-stage kidney disease and increased morbidity in dogs.² Definitive diagnosis in this case would require renal biopsy with histopathology, which the owner declined due to the associated risk of the procedure and the patient’s advanced age.

Therapeutic plan
Low-protein diet, aspirin 20 mg every 3 days, azathioprine 25 mg every 4 days, enalapril 2.5 mg every other day

Clinical Outcome
Milly has continued to do well clinically on the therapeutic plan. Her urinalysis, UPC, CBC and clinical chemistry are monitored regularly, thanks to a very compliant and dedicated owner. However, there has been little change in her laboratory parameters or clinical status over the last several months.

References:

1. Feldman EC, Nelson RW. Canine and Feline Endocrinology and Reproduction. 3rd ed. Philadelphia, Pa: WB Saunders; 2004.
2. Jacob F, et al. Evaluation of the association between initial proteinuria and morbidity rate or death in dogs with naturally occurring chronic renal failure. J Amer Vet Med Assoc. 2005;226:393–400.

Recommended Reading:

• Duncan JR, et al. Veterinary Laboratory Medicine: Clinical Pathology. 4th ed. Ames, Iowa: Iowa State University Press; 2003.
• Stockham SL, et al. Fundamentals of Veterinary Clinical Pathology. 1st ed. Ames, Iowa: Iowa State University Press; 2002.

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 history, 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.

Tell us what you think of this case, or let us know if you have a case that you would like to submit. E-mail us at diagnosticedge@idexx.com to get the process started.

Fort Dodge Animal Health reintroduces ProHeart® 6 in U.S.
A quick look at guidelines for use and recommended protocol

ProHeart 6 reintroduced
Recently, Fort Dodge Animal Health reintroduced ProHeart® 6 (moxidectin) to the U.S. veterinary market after a review by the U.S. Food and Drug Administration’s Center for Veterinary Medicine (CVM). ProHeart 6, a heartworm preventative, was voluntarily recalled by Fort Dodge from the U.S. veterinary market in September 2004. Based on CVM requirements, Fort Dodge will implement a surveillance initiative to monitor the safety of ProHeart 6. It will be incumbent upon Fort Dodge to communicate any reported adverse reactions to the CVM.

Veterinarians who wish to purchase and administer ProHeart 6 must first participate in a
Web-based training program to become registered users. For more information, practitioners are directed to the Fort Dodge symposium at: www.vetsymposium.com/proheart6.

Recommended ProHeart 6 protocol
According to the guidelines established by Fort Dodge and approved by CVM, ProHeart 6 may be administered:

• To healthy dogs between six months and seven years of age
• After a thorough history is gathered and a general physical examination is performed by the veterinarian
• After performing a negative heartworm antigen test, a complete blood count (CBC) that includes a platelet count and a chemistry panel that includes baseline liver values

Tools to assist with your ProHeart 6 protocols
IDEXX Laboratories is pleased to provide the most comprehensive diagnostics available to comply with and exceed required CVM guidelines for those practitioners who elect to use ProHeart 6. For in-house use, we recommend a CBC performed with the LaserCyte® Hematology Analyzer or the IDEXX VetAutoread™ Hematology Analyzer, combined with a comprehensive chemistry panel, such as the Diagnostic Health Profile (DHP) on the VetTest® Analyzer or a Chem 17 on the Catalyst Dx™ Chemistry Analyzer. In addition, a SNAP® 4Dx® test should be run and a complete urinalysis is recommended to allow for interpretation of the renal panel in the chemistries. A blood film review should be performed as well to detect morphologic abnormalities.

The DHP is a valuable screen for both the clinically and subclinically sick patient for which the administration of ProHeart 6 is contraindicated. The DHP panel includes ALT, GGT, ALB, ALKP and BUN and provides the most comprehensive patient-side baseline liver values available, not only fulfilling but surpassing the requirements of the CVM. Comprehensive baseline values will prove critical should an adverse reaction to ProHeart 6 occur. Lastly, the flexibility of the VetTest and Catalyst Dx analyzers allows for customized mini panels for more targeted liver testing. IDEXX Reference Laboratories provides similar comprehensive screens.

For more information about ProHeart 6 or Web registration, visit the Fort Dodge Animal Health Web site at www.vetsymposium.com/proheart6. To learn more about the IDEXX instruments and testing protocols above, visit www.idexx.com/vetlab or call 1-800-355-2896.

IDEXX Learning Center

The IDEXX Learning Center provides knowledge you can put into practice. Take part in the evolution of animal diagnostics through an ongoing educational partnership with leading veterinarians from across the globe and take advantage of a wide range of education resources, reference materials and events. Visit the IDEXX Learning Center to see a full listing of available Webinars, seminars and online training courses from IDEXX.
 

Create your own account on the IDEXX Learning Center and see how IDEXX can help you reach your educational goals!

Here are some of the opportunities available this month:

• Evaluate Your Blood Film in Less than 3 Minutes
  Dr. Dennis DeNicola
• Three Steps to a Healthy and Profitable Practice
  Dr. Ernie Ward
• Smart Practice Investments in a Tight Economy
  Gary Glassman, CPA

See a full listing of Webinar opportunities >

• Fecal Analysis
• Bleeding Disorders: The IDEXX Guide
• IDEXX VetTest® Certificate Course

See a full listing of online training opportunities >

• Advances in the Diagnosis and Management of Canine Pancreatitis
  Various Presenters
• Fluid Therapy: Beyond the Basics
  Dr. Robert Hawthorne
• The Most Commonly Misdiagnosed Diseases in Veterinary Medicine
  Dr. Fred Metzger

See a full listing of seminar opportunities >

NEW benefits from Cornerstone® Reminder Service
Developed based on customer input and recommendations

Movers Cards
Market your practice to new potential clients in your area. Select by ZIP Code or by a certain radius around your address. The lists can be edited, saved for future use or used with one of four new mover card designs. A reproducible map of your practice location is also available, which can be added to the front of the card and can be automatically saved to your profile for future use.

Wellness Kits
Send a wellness kit as a reminder card. Clients receive a fecal container for easy handling of stools prior to the visit, along with instructions for taking samples. The kit also includes a $5.00 coupon for Merial Heartgard® heartworm preventative and helps you produce a letter with your logo that includes specific reminders for services.

Promotional Items
Give your clients customized refrigerator magnets. These designs allow for your logo, phone number and times of operation, and one design has room for a personalized message. Customize quantities and colors. Look for the new magnets under the promotional tab.

If you have questions about the Cornerstone Reminder Service, please call
1-888-224-4408 or visit us online at www.idexxreminderservice.com.

Choosing cartridges for the Coag Dx™ Analyzer
How do you choose between citrate or fresh whole blood cartridges?

The Coag Dx Analyzer offers you a choice of cartridges. Not only can you choose between prothrombin time (PT) or activated partial thromboplastin time (aPTT), but you can also choose citrate or fresh whole blood cartridges. How do you decide?

Here are some tips to help you choose the cartridges that are right for your practice.

Citrate PT and aPTT cartridges—test when it’s convenient for you

• Test within two hours when kept at room temperature
• Test both citrate PT and citrate aPTT with one sample draw (if further testing is needed, spin the sample down and ship frozen plasma to an outside laboratory)
• Use a 3.2% sodium citrate evacuated tube or syringe (IDEXX recommends using the 1.8-mL or 2.7-mL 3.2% sodium citrate tubes available from most distributors)

Fresh PT and aPTT cartridges—uses a smaller sample size

• Draw blood with a plastic syringe and dispense it directly on the cartridge
• As little as 0.2 mL of fresh blood is needed
• Fresh samples need to be run immediately
• Separate blood draw needed for each cartridge

For more information on the Coag Dx Analyzer or its cartridges, please call
1-800-355-2896 or visit www.idexx.com/coag.

With FREE continuing education credit!*

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Figure 1—Transtracheal wash from a cat with a chronic cough, Wright’s stain, 100x objective field of view. The cells in this field of view represent the predominating cell population in the preparation.

Figure 2—Transtracheal wash from a cat with a chronic cough, Wright’s stain, 100x objective field of view.

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*Each interactive challenge meets the requirements for 0.5 hour of continuing education credit in jurisdictions that recognize AAVSB’s RACE approval, however, participants should be aware that some boards have limitations on the number of hours accepted in certain categories and/or restrictions on certain methods of delivery of continuing education.

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^†Interactive challenges are also approved in Australia for 0.5 AVA Vet Ed Point and from the following Canadian Veterinary Medical Associations: Alberta, Saskatchewan, New Brunswick and Prince Edward Island.

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