4 Urine cortisol: creatinine ratio
This simple diagnostic test is a great screening test for hyperadrenocorticism, one of the most common endocrine diseases
in dogs. A single urine sample, usually collected at home by the owners, is submitted, and the ratio of cortisol to creatinine
is determined. This test has a high sensitivity (few false negative results), and a result within the reference range virtually
assures you that the patient does not have hyperadrenocorticism.
However, the urine cortisol:creatinine ratio has low specificity (many false positive results) and is not useful for diagnosing
Cushing's disease. A result above the reference range may be due to hyperadrenocorticism, excitement, concurrent illness,
or normal circadian variation in cortisol concentrations.
An often-overlooked component of the minimum database, a urinalysis should be submitted at the same time a complete blood
count (CBC) or serum chemistry profile is performed. The urine specific gravity, one of the most important parameters measured
on a urinalysis, is essential for localizing azotemia (prerenal, renal, postrenal). Additionally, low urine specific gravity
is seen with many serious diseases including renal failure, liver disease, and both hyperadrenocorticism and hypoadrenocorticism.
Bilirubinuria may be an early indicator of liver disease, and a urine sediment examination may help with diagnosing renal
disease, assessing the risk of urolith formation, or identifying animals with asymptomatic urinary tract infections.
When proteinuria is noted on the urinalysis in the absence of an active urine sediment or signs of lower urinary tract disease,
a urine protein:creatinine ratio is indicated. Since proper management of protein-losing nephropathies may increase survival
time, proteinuria warrants treatment and serial monitoring.6,7 Proteinuria in patients with renal failure worsens prognosis; however, appropriate treatment may improve both a patient's
quality of life and survival time.
6 Bacterial culture and antimicrobial sensitivity testing
Many patients presented to their veterinarians for evaluation of various clinical signs are empirically treated with an antibiotic,
which—without a doubt—can be effective. However, in many animals, the clinical signs return, and it becomes unclear whether
infection has recurred or was inadequately treated or whether the initial antibiotic course simply had a placebo effect. Additionally,
the prevalence of multidrug-resistant infections such as methicillin-resistant Staphylococcus aureus has been increasing, so responsible antibiotic therapy is essential.
Consequently, all patients—even those with their first urinary tract infection, first bout of otitis, or initial bout of coughing—should
undergo bacterial culture and antimicrobial sensitivity testing before receiving antibiotics whenever possible, even though
this adds expense for clients.8 Obtaining a sample of urine, purulent material, or tracheal wash fluid is generally a simple procedure and can be essential
in directing appropriate antibiotic choice.
7 Coagulation time
Testing coagulation time is much easier now with point-of-care machines. Knowing a patient's coagulation status is particularly
useful in diagnosing possible rodenticide toxicosis, liver failure, or disseminated intravascular coagulation. Assessing coagulation
time allows you to prioritize differential diagnoses and diagnostic tests and to help determine prognosis and treatment options.
Coagulation testing also preemptively establishes the risks associated with more invasive diagnostic tests. Identifying abnormalities
in coagulation times allows the problem to be addressed before serious consequences such as hemorrhage, shock, or death occur.