Page 335 - Problem-Based Feline Medicine

17 – THE CAT WITH WEIGHT LOSS AND A GOOD APPETITE 327

Clinical signs may be non-specific. Typically in the Urinalysis may reveal an inactive sediment, with or
later stages there is anorexia, depression, weight loss, without hyaline and/or granular casts.
lethargy and poor coat condition. More specific signs
It is important to try to determine an underlying
include subcutaneous edema, ascites, and polyuria
cause. This may involve screening radiography and
and polydipsia.
ultrasonography, tests for immune-mediated disease,
It tends to takes one of two clinical forms: and numerous tests for infectious disease (see above for
● Nephrotic syndrome with ascites and subcuta- the list of possible diseases).
neous edema, usually affecting the hind legs, ven-
Systemic blood pressure should be assessed.
tral body wall and neck. This form may or may not
be associated with signs of renal failure (polyuria, Abdominal radiographs and ultrasound examination
polydipsia). rarely reveal obvious renal changes.
● Renal failure with no signs of nephrotic syn-
Renal biopsy is necessary to confirm the diagnosis
drome.
and find which type of glomerular disease is present.
Cats with early nephrotic syndrome may present ● Blood clotting times, platelet number, and systemic
with weight loss with a good appetite. blood pressure should be assessed prior to biopsy.
● Ultrasound-guided percutaneous biopsy is rela-
Edema affecting the intestines can exacerbate the pro-
tively safe but laparotomy or laparoscopy reduces
tein loss and result in malabsorption, diarrhea, vom-
the risk of post-operative bleeding. Renal hemor-
iting and weight loss.
rhage is a risk, especially if hypertensive.
Systemic hypertension may arise secondary to the ● Sample must contain >5 glomeruli to make a diag-
renal dysfunction and result in acute blindness, ocular nosis; this usually means multiple needle biopsies
hemorrhages or signs of CNS dysfunction. or a wedge biopsy are required.
● Routine histopathology (fix sample in buffered
Other clinical signs may result from any primary dis-
normal formalin), electromicroscopy (fix sample
ease conditions.
in paraformaldehyde-glutaraldehyde), ± immuno-
On abdominal palpation, the kidneys may appear histochemistry (keep fresh and paraffin embed) are
small and/or irregular or, occasionally, enlarged. needed to confirm a diagnosis.
● On gross inspection kidneys may appear normal,
be slightly small, firm and pale, or show irregular
Diagnosis
pitting and fibrosis.
Cats with nephrotic syndrome have marked pro- ● Light microscopy typically shows diffuse thicken-
teinuria, hypoalbuminemia and hypercholes- ing of the glomerular basement membrane, with
terolemia. variable degrees of cellular proliferation in the
affected glomeruli. Special stains can help to define
Other findings may include hypertriglyceridemia,
the changes, but electromicroscopy and immunohis-
hypocalcemia, non-regenerative anemia and neu-
tochemistry are needed to define the exact nature and
trophilia.
extent of the disease.
Increased concentrations of blood urea and creatinine
(azotemia) and a low urine specific gravity (<1.035) will
indicate whether or not renal insufficiency is present. Differential diagnosis
Persistent proteinuria is the hallmark of glomeru- Chronic renal failure, diabetes, acromegaly, hyper-
lonephritis. adrenocorticism and hyperthyroidism are impor-
● This should be quantified by determining the urine tant differentials in those cats that develop polyuria
protein to creatinine ratio (UPC ratio). and polydipsia. However, the presence of ascites
● UPC ratio: < 0.4 = normal, > 0.4–2 suggestive of in combination with polyphagia is suggestive of lym-
glomerulonephropathy or tubular disease, > 2 con- phocytic cholangitis/cholangiohepatitis complex.
sistent with glomerulonephropathy. Once hypoalbuminemia is detected, then a protein-