Page 367 - Problem-Based Feline Medicine

18 – THE THIN, INAPPETENT CAT 359

The kidneys are usually small, firm and irregular on Routine biochemistry should be evaluated.
palpation. ● Plasma protein concentrations may be variable,
with hypoalbuminemia occurring if the protein loss
Both conditions are associated with an underlying
is severe. Conversely, hyperglobulinemia may
chronic antigenic stimulus, including infectious,
occur associated with the chronic inflammatory
inflammatory and neoplastic diseases. Clinical signs
focus initiating the lesion.
may also relate to the underlying disease.
● Hypercholesterolemia is reported as a characteris-
Systemic hypertension may occur and result in hyper- tic feature of the nephrotic syndrome, however it is
tensive retinopathy, acute-onset blindness or neurolog- a common non-specific finding in cats with any
ical signs. form of renal disease.
● Azotemia and a low urine specific gravity will indi-
The prognosis is variable depending on the cause of the
cate the presence of renal failure.
protein-losing nephropathy, although is generally con-
sidered poor if actual renal failure is present. Abdominal radiography and ultrasound may provide
● Clinical signs in glomerulonephritis may wax and information on renal architecture and size.
wane, and occasionally undergo complete or pro-
Renal biopsy is the only definitive method of dis-
longed periods of remission.
tinguishing between glomerulonephritis and amy-
● Amyloidosis tends to be slowly progressive, and is
loidosis.
generally fatal.
● Complete morphological classification of glomeru-
lar lesions may require light, electron and immuno-
fluorescence microscopy.
Diagnosis
● Amyloid deposits demonstrate characteristic green
Diagnosis of protein-losing nephropathy is made on birefringence after Congo red staining when viewed
the documentation of proteinuria, in the absence of under polarized light.
pre- and post-renal causes. A complete urinalysis – The diagnosis is frequently difficult to achieve if
should therefore be carried out. glomerular involvement is minimal or absent,
● Urinalysis typically reveals proteinuria with requiring medullary biopsies.
a benign sediment. A benign sediment excludes
A thorough investigation for an underlying inflam-
lower urinary tract disease as a cause of the
matory focus should be made, including assessment
proteinuria.
of FeLV and FIV status.
● Hyaline casts may be noted on sediment examina-
tion.
● In the early stages of disease, urine-concentrating TOXOPLASMOSIS
ability may be retained.
● Proteinuria is usually detected on qualitative Classical signs
screening tests, such as urine dipstick reagent
● Especially in immuno-compromised
strips.
individuals, particularly free-roaming cats.
The protein:creatinine ratio should be evaluated to ● Weight loss, lethargy and inappetence.
further quantify the urinary protein loss. ● Fever.
● Although the magnitude of the proteinuria can be ● Respiratory distress.
used to predict the site of protein loss, there is great ● Icterus.
variability in ratios with different diseases. ● Uveitis.
● The quantity of protein loss in glomerular disease is ● Neurological signs including ataxia and
massive compared with that in pre-renal and post- seizures.
renal proteinuria. Protein:creatinine ratios of ● Muscle hyperesthesia.
greater than 13 commonly occur in glomerular pro-
teinuria, although ratios generally range from mild See main references on page 376 for details (The
to severe (ratio of 5–13). Pyrexic Cat).