Page 574 - Problem-Based Feline Medicine

566 PART 8 CAT WITH ABNORMAL LABORATORY DATA

increased erythropoietin production. These sensors are Treatment
thought to be located in the juxtaglomerular complex.
Treatment should be directed at the space-occupying
Some renal tumors may secrete erythropoietin or an mass, which is the underlying cause of the poly-
erythropoietin-like substance, resulting in erythrocy- cythemia.
tosis.
Nephrectomy may be considered in cases of second-
This kind of polycythemia is secondary to another ary inappropriate polycythemia from a renal space-
pathological condition and inappropriate, since occupying mass, but nephrectomy is considered a
blood O saturation levels are normal. last-resort treatment as the resultant reduction in func-
2
tional renal mass may precipitate renal insufficiency or
Clinical signs failure. Also, polycythemia may reoccur if metastatic foci
secrete erythropoietin or a functionally similar substance.
Clinical signs are referable to the inciting condition,
whether renal or neoplastic. Lethargy, weight loss and
Prognosis
inappetence are common.
The prognosis depends on the underlying cause of
Mucus membranes are dark pink.
the polycythemia. Polycystic renal disease is a
Signs of hyperviscosity may be present including tor- degenerative condition with a poor prognosis, and
tuous retinal vessels, seizures and other CNS signs, and most renal tumors have a guarded prognosis, at best.
intermittent bleeding diathesis. The prognosis with other kinds of neoplasia varies
according to the tumor type.
Signs of renal insufficiency, such as azotemia, reduced
urine specific gravity, polydipsia and polyuria may be
present. However, not all cases of polycythemia from ACUTE SYSTEMIC ANAPHYLAXIS
renal space-occupying masses will be accompanied by
signs of renal insufficiency, due to the relatively large Classical signs
functional reserve of the kidneys.
● Acute dyspnea.
● Hypotensive shock.
Diagnosis
● Collapse.
Renal space-occupying masses are best visualized using ● Pale mucous membranes.
abdominal ultrasound, although intravenous pyelog-
raphy may also be a valuable imaging technique. Pathogenesis
Serum erythropoietin levels are normal or elevated, Acute systemic anaphylaxis is caused by exposure to a
and blood O saturation levels are normal. foreign antigen, usually protein, and generally by the
2
intravenous route.
Differential diagnosis
While prior exposure to the antigen is usually necessary
Secondary inappropriate polycythemia must be differ- for sensitization to occur, anaphylaxis may occur on
entiated from relative polycythemia caused by dehy- first exposure to the antigen. This is termed an ana-
dration, secondary polycythemia from hypoxia and phylactoid reaction.
primary polycythemia.
Anaphylaxis causes increased vascular permeability,
● When a renal space-occupying mass is causing poly-
allowing potentially large amounts of plasma to escape
cythemia, plasma protein concentration and blood
from the intravascular space, resulting in hemoconcen-
O saturation levels should be normal, while serum
2 tration.
erythropoietin concentration is often inappropriately
high. These factors differentiate secondary inappro- It is also hypothesized that epinephrine is released
priate polycythemia due to a renal space-occupying during acute shock, causing splenic contraction and
mass from other conditions causing polycythemia. the infusion of large numbers of stored erythrocytes
into the circulation.