Page 720 - Small Animal Internal Medicine, 6th Edition

692 PART V Urinary Tract Disorders

administered to normal dogs at an infusion rate of 0.8 µg/ and cats are listed in Box 41.2 and familial diseases of dogs
kg/min, it significantly increased GFR and fractional excre- and cats are listed in Box 41.3.
VetBooks.ir tion of sodium. In a study of dogs and cats with AKI, however, Staging
no significant differences in BUN or SCr, length of hospital
stay, and survival were found between animals treated with
Kidney Foundation to refer to human patients with five
fenoldopam and those not treated with the drug. The term chronic kidney disease is used by the National
Dialysis may be the only way for a dog or cat with AKI stages of renal disease. Patients in stage 5 CKD have a GFR
2
to survive the metabolic consequences of advanced uremia, less than 17% of normal (<15 mL/min/1.73 m ), are azo-
especially in the presence of oliguria or anuria. Hemodialysis temic, and are classified as being in chronic renal failure.
removes uremic waste products and retained water very effi- Those in stage 4 CKD have a GFR 17% to 32% of normal
2
ciently but is technically demanding, very expensive, and (15-29 mL/min/1.73 m ), and might also be azotemic and in
available for dogs and cats only at a limited number of treat- chronic renal failure. CKD in dogs and cats can be staged
ment facilities. Even with intermittent hemodialysis, overall similarly using guidelines proposed by the International
survival at time of discharge was only 53% for dogs and 50% Renal Interest Society (IRIS), an international group whose
for cats with AKI in one study. Peritoneal dialysis requires mission is to help veterinarians better understand the diag-
less technical expertise, is less expensive, and is more widely nosis and management of CKD in dogs and cats. Guidelines
available than hemodialysis. Historically, dialysis has been for staging CKD in dogs and cats based on SCr are shown
attempted mainly late in the clinical course of dogs and cats in Table 41.2. According to IRIS guidelines, dogs and cats
with AKI when fluid, acid-base and electrolyte abnormali- with stages 2, 3, and 4 CKD are azotemic and thus have mild,
ties, and azotemia are advanced. Early institution of dialysis moderate, or severe CKD, respectively. SCr always should be
in severe AKI may provide greater opportunity for survival interpreted along with USG and the physical examination
and recovery and diagnostic imaging findings, especially renal size. Guide-
lines established by IRIS also include substaging based on
Prognosis the extent of proteinuria (i.e., magnitude of UPC ratio) and
Oliguria or anuria that persists or develops during treatment hypertension (see http://www.iris-kidney.com/guidelines/).
is associated with a poor prognosis. The most common
causes for death or euthanasia during initial management of
AKI in the maintenance phase are hyperkalemia, metabolic
acidosis, or severe azotemia. Overhydration with resultant
pulmonary edema as a consequence of aggressive fluid BOX 41.2
therapy is another important cause of death or euthanasia. Causes of CKD in Dogs and Cats
The underlying cause of AKI also affects prognosis because
some causes of AKI are worse (e.g., ethylene glycol intoxica- Dog
tion) than others (e.g., leptospirosis). Aminoglycoside neph- • Chronic interstitial nephritis (CIN) of unknown cause
rotoxicity and NSAID-induced AKI also often are associated (most common pathologic diagnosis)
with a poor prognosis. Other organ system disease or failure • Chronic pyelonephritis (can be difficult to distinguish
also worsens the prognosis (e.g., heart failure, diabetes mel- histologically from CIN)
litus, liver disease, pancreatitis, disseminated intravascular • Chronic glomerulonephritis (can be difficult to
coagulation, neoplasia, sepsis). AKI patients require inten- distinguish histologically from CIN)
sive care and major surveillance, so the level of medical care • Amyloidosis
available also affects prognosis. Overall, death or euthanasia • Familial renal disease (several dog breeds can be
affected)
can be expected in approximately 50% of dogs and cats with • Healing of acute kidney injury
AKI. Of those that survive, approximately half can be
expected to develop CKD and the other half to become clini- Cat
cally normal, based on the SCr. • CIN of unknown cause (most common pathologic
diagnosis)
• Chronic pyelonephritis (can be difficult to distinguish
CHRONIC KIDNEY DISEASE histologically from CIN)
• Chronic glomerulonephritis (can be difficult to
CKD culminates in renal failure when compensatory mecha- distinguish histologically from CIN)
nisms are no longer able to maintain the normal excretory, • Amyloidosis (uncommon in mixed-breed cats but
regulatory, and endocrine functions of the kidneys. The familial in Abyssinians)
resultant retention of nitrogenous solutes, derangements of • Polycystic kidney disease (familial in Persians)
• Healing of acute kidney injury
fluid, electrolyte, and acid-base balance, and failure of • Neoplasia (renal lymphoma)
hormone production constitute the syndrome of CKD. A • Pyogranulomatous nephritis caused by feline infectious
diagnosis of CKD is made when these abnormalities have peritonitis
been present for 3 months or longer. Causes of CKD in dogs