Page 366 - Problem-Based Feline Medicine

358 PART 6 CAT WITH WEIGHT LOSS OR CHRONIC ILLNESS

– If the cat has not eaten recently, the fluid may ● Initially the glomerular injury is characterized by
appear only slightly opaque. proteinuria, but as the condition progresses, the
● Lymphocytes are usually the predominant cell type, entire nephron may become non-functional, with
with some non-degenerate neutrophils. decreased glomerular filtration rate and azotemia.
● The concentration of triglycerides in the fluid ● Glomerulonephritis may be found in association
exceeds that of the serum in a true chylous with any chronic antigenic stimulus, including
effusion. infectious, inflammatory and neoplastic diseases.
– In the cat, glomerulonephritis has been particu-
It is important that, where possible, the underlying
larly associated with infectious diseases including
cause is investigated, as this will influence the treat-
FeLV, FIV and FIP, and hemolymphatic neoplasia.
ment and prognosis.
– In the majority of cases an underlying antigen
source is not identified and the disease is classed
PROTEIN-LOSING NEPHROPATHY as idiopathic.
Glomerular proteinuria is characteristically mas-
Classical signs
sive, and in many cases may lead to clinical signs
● Marked weight loss. related to protein loss and eventually the nephrotic
● Initially polyphagia may be present but syndrome.
progresses to inappetence.
The nephrotic syndrome is characterized by mas-
● Polydipsia and polyuria.
sive proteinuria, hypoalbuminemia, hyperlipidemia
● Subcutaneous edema and/or ascites.
and subcutaneous edema and/or ascites.
● The proteinuria leads to hypoalbuminemia and sub-
sequent development of edema.
Pathogenesis
The most common causes of protein-losing
nephropathy are glomerulo-nephritis and renal
Clinical signs
amyloidosis.
Protein-losing nephropathies are uncommon conditions
Renal amyloidosis is characterized by the extra-
in the cat.
cellular deposition of fibrillar proteins arranged in a
● Glomerulonephritis usually affects young adult
beta-pleated sheet configuration.
cats (average age 3–4 years), with males being pre-
● Reactive (secondary) systemic amyloidosis is the
disposed. The condition is rare.
form of amyloidosis occurring in cats.
● Most cats with amyloidosis are over 5 years of age
– It is considered to be secondary to inflamma-
at diagnosis. Systemic reactive amyloidosis occurs
tory, neoplastic and chronic infectious disease,
as a familial disease in Abyssinian cats.
although in many cases the predisposing disease
is not found. Clinical signs in early disease are principally weight
● Severe proteinuria occurs when amyloid deposits in loss with a good appetite and even polyphagia.
the glomerulus cause glomerular damage. ● Signs frequently progress to inappetence and
– Most domestic cats with amyloidosis and at least depression.
25% of Abyssinian cats with familial amyloi- ● Continued protein loss eventually leads to the
dosis have medullary amyloid deposits, without nephrotic syndrome with subcutaneous edema
significant glomerular deposits. and/or ascites.
– In cases of medullary amyloidosis, proteinuria
Polyuria and polydipsia are common if the condition
may be mild or absent, although the deposits will
progresses to renal failure and uremia.
interfere with renal concentrating ability.
● Polyuria and polydipsia are also common if there
Glomerulonephritis is caused by antibody–antigen are medullary amyloid deposits.
complexes present in the glomerulus that lead to ● Clinical signs of uremia may also be noted (see
immune-mediated glomerular damage. page 334, chronic renal failure).