Page 11 - Problem-Based Feline Medicine

1 – HOW TO MAKE A PROBLEM-BASED DIAGNOSIS 3

P : * physical (e.g. heat, cold, water, fire) To rank diseases as likely, possible, or unlikely, cross-
* psychological match the patient’s signalment (breed, age, gender),
* pharmacological (drug effect) clinical signs, and physical examination findings with
the known characteristics of the disease including
I : * infectious (viral, bacterial, mycoplasma,
typical signalment, signs and physical examination
rickettsial, protozoal, fungal, parasitic)
findings of the disease and frequency of disease (how
* immune
common it is).
* iatrogenic (caused by you)
* idiopathic (unknown) ● For the differential diagnosis “diabetes mellitus”, con-
* infarct sider whether the typical signalment, history and
physical examination findings of this disease fit the
T : * trauma
patients findings. An example of the thought process-
* toxic/adverse drug
es are the following: Diabetes mellitus is a very like-
For example, the answer to “WHAT?” diseases could ly cause of the problem because it occurs in older cats,
cause polyuria/polydipsia in a 10-year-old male castrated male cats are more often affected, and the patient has
domestic shorthair cat that has a history of losing weight all the expected signs, including signs of chronic dis-
for 2 months, a good appetite until the last couple of days, ease, polydipsia and polyuria, weight loss and a good
frequently urinating in the litter box, and drinking appetite until recently. The high volume of water
1 liter/day include: drunk by this cat can occur with diabetes mellitus.
● For the differential diagnosis, “chronic renal failure”
D : Chronic renal failure an example of the thought processes is: Chronic renal
failure is a possible cause of the problem because the
A :
expected signs include evidence of a chronic disease,
M : Diabetes mellitus with weight loss and recent inappetence. However, cats
Diabetes insipidus with renal failure that have marked polydipsia often
Hyperthyroidism have a more picky appetite once weight loss is appar-
Hyperadrenocorticism ent, and the volume of water drunk is usually less.
Hepatic failure ● For the differential diagnosis “hepatic failure”, an
Hypercalcemia example of the thought processes is: Hepatic failure
Acromegaly is an unlikely cause of this cat’s problem because
Hypoadrenocorticism although this cat has some of the clinical signs
Hypercalcemia expected with hepatic failure, it does not have all of
the typical signs. The signs of this patient that fit
N : Renal neoplasia
include: chronic disease with lethargy, inappetence
Lymphoma and
and weight loss. Polydipsia can occasionally occur if
pseudohyperparathyroidism
there is liver failure. However, cats with hepatic fail-
Polycythemia vera
ure sufficient to cause weight loss and affect renal
P :
concentrating mechanisms are usually inappetent
I : Infectious Pyelonephritis and jaundiced. In addition, hepatic failure is a rare
Cystic endometrial hyperplasia/ cause of polydipsia in cats.
pyometra ● It helps to know 1–5 lines of information for each
Immune Glomerulonephritis/renal disease on your list of differential diagnoses. You
amyloidosis should know more about the common diseases
than uncommon diseases. Learn the typical signal-
T : Vitamin D toxicity
ment, clinical signs, physical examination findings,
Drugs such as
and frequency of diseases that occur in your area.
corticosteroids
4. Formulate a diagnostic plan to prove or disprove
After listing the diseases, rank the diseases as likely,
each possible disease. Choose the initial diagnos-
possible or unlikely based on cross-matching the
tic tests based on:
patient’s data with the characteristics of the disease.