Page 342 - Problem-Based Feline Medicine

334 PART 6 CAT WITH WEIGHT LOSS OR CHRONIC ILLNESS

● Cysts vary in size and tend to increase in number Early cases may be asymptomatic.
and size with time. Eventually progressive cyst
Signs associated with chronic renal failure result
enlargement compresses the adjacent renal
from failure of excretory, regulatory and synthetic
parenchyma and if sufficient renal mass is affected
functions of the kidney.
renal failure will develop. Renal failure may occur
at any age, however affected Persian cats typically Polydipsia is the most commonly reported clinical
present at approximately 7 years. sign. The polydipsia is compensatory to an obliga-
● Renomegaly may be obvious with the kidneys tory polyuria. If fluid intake is insufficient, dehydra-
being irregular in outline. Laboratory evaluation is tion will result. Polyuria results from:
necessary to determine the extent of the renal dys- ● Increased solute load in surviving functional
function. Ultrasonographic examination is non- nephrons (solute diuresis).
invasive and a very sensitive diagnostic technique ● Disruption of medullary anatomy.
for this condition. Cysts are seen as multiple, round ● Impaired response to antidiuretic hormone.
anechoic regions.
Inappetence or anorexia, weight loss and poor body
In chronic renal failure resulting from many of the dis- condition are common clinical signs as the disease
ease processes, renal function often slowly deterio- progresses.
rates over months or years, but the rate of deterioration
Lethargy, weakness and depression.
is very variable between cats. Deterioration is not neces-
sarily linear and many cats are stable for long periods of Vomiting (with possible hematemesis) is usually inter-
time with intermittent acute decrements. The postulated mittent and often low grade. Vomiting and nausea
causes of progression include: may be associated with:
● Primary disease process; the inciting cause may ● The action of uremic toxins on the medullary
lead to ongoing renal damage. emetic chemoreceptor trigger zone.
● Systemic and metabolic derangements of chronic ● Uremic gastritis and gastrointestinal ulceration.
renal failure.
Constipation is common and results from dehydration.
● Renal compensatory mechanisms (increase in sin-
gle nephron glomerular filtration rate). Severe uremia associated with an acute exacerbation
of chronic renal failure (acute on chronic) or end-stage
In chronic renal failure, surviving functional nephrons
chronic renal failure may be associated with extreme
undergo compensatory changes including glomerular
clinical signs including:
hypertension, hypertrophy and hyperfiltration (leading to
● Halitosis, ulceration of oral mucosa or tongue
an increase in single nephron glomerular filtration rate).
and brownish discoloration of dorsal surface and
● These adaptive mechanisms compensate for the
sloughing of anterior tip of tongue (due to fibinoid
loss of nephrons and so minimize the overall
necrosis, arteritis and bacterial degradation of urea
decrease in glomerular filtration rate.
to ammonia).
● However, it is postulated, based on extrapolation
● Occasionally diarrhea, which may be hemorrhagic
from other species, that these compensatory
from uremic enterocolitis.
changes are maladaptive and represent a final com-
● Terminally, seizures, stupor or coma may occur.
mon pathway for the progression to eventual
glomerular sclerosis and end stage renal failure. Clinical signs relating to systemic arterial hypertension
are common. Hypertension is reported in 29–61% of
cats with chronic renal failure. Clinical signs which
may be associated with hypertension include:
Clinical signs
● Ocular signs include sudden blindness with dilated
Chronic renal failure is mainly a disease of older pupils, hyphema or retinal hemorrhage, retinal
cats, with Persian, Abyssinian, Maine coon, Siamese edema, retinal vessel tortuosity, retinal detachment.
and Burmese breeds of cat being identified to be at ● Systolic heart murmurs and a gallop rhythm.
increased risk. ● Neurological signs including seizures and stupor.