Your experience with diagnosing and treating acute renal failure is extensive given your position as an assistant professor
of small animal internal medicine at Purdue University and your special interest in areas of renal disease. Can you describe
some of the most common presentations in dogs vs. cats?
Pressler: In general, patients with acute renal failure are much sicker than patients with azotemic chronic kidney disease (i.e., chronic
renal failure). Both dogs and cats are often moderately to severely dehydrated at the time of diagnosis, and owners may comment
on a recent increase in thirst and urination. Dogs usually have much more severe gastrointestinal (GI) signs (severe vomiting,
in particular) than cats do, which more commonly are reported by their owners to have stopped eating and recently become less
sociable. Anuria or oliguria is the most dreaded presentation for patients with acute renal failure in both species, with
cats more likely to have decreased urine production than dogs.
Ruling out causes: According to Dr. Pressler, a thorough history can help rule out possible toxins and other suspects of
acute renal failure.
Do these patients often present with concurrent disease conditions?
Pressler: Many patients with acute renal failure have additional diseases or conditions diagnosed at the time of presentation. These
concurrent conditions may be the cause of their acute renal failure — for example, pancreatitis, heart failure or hypoadrenocorticism
— or may be consequences of the same conditions that resulted in kidney damage as in the case of disseminated intravascular
coagulopathy (DIC). Concurrent conditions may also have developed secondary to the renal failure itself, as in the case of
pulmonary edema, pancreatitis, hypovolemic or hypotensive shock or pancreatitis. In general, cats seem less likely to have
most of these concurrent diseases, but, on the contrary, they are more likely to have infiltrative renal disease such as lymphoma
or feline infectious peritonitis (FIP) or ureteral obstruction as a cause of their renal failure.
How do you approach diagnosis in suspected cases of acute renal failure?
Pressler: Acute renal failure, by definition, is at least partially reversible with aggressive therapy. Therefore, diagnosing the underlying
cause of kidney disease offers the best chance of preventing damage from progressing via targeted therapy on top of aggressive
general support. Naturally, I always start with a thorough history and physical examination. I never ask owners if their pets
could have gotten into any toxins because many people do not know that some common household plants and drugs can result in
kidney disease. Instead, I run through a list of possible toxins with owners one by one and ask individually about lilies,
NSAIDs, grapes, etc. I treat all dogs with acute renal failure for leptospirosis while awaiting results of serum titers, both
because this disease is prevalent throughout most of the United States and because of the zoonotic risk. I also culture urine
immediately, regardless of urine sediment findings, in the event that renal failure is due to pyelonephritis. Finally, I always
include abdominal imaging in my diagnostic evaluation of patients with acute renal failure in order to diagnose infiltrative
diseases such as lymphoma or FIP or to detect ureteral obstructions.
What are the most important treatment concerns when a dog presents with acute renal failure?
Pressler: The importance of correcting and continually monitoring hydration status cannot be overstated in any patient with acute renal
failure. Many patients are dehydrated at the time of first presentation. Aggressively replacing any fluid deficits (usually
over the course of just a few hours) is required to normalize renal blood flow; this allows urine production that will hopefully
unclog nephrons that have become obstructed by damaged, sloughed cells; provides oxygen to injured and healing tubules; and
maintains blood flow to the renal medulla, which is highly sensitive to hypoxemic damage. Patients with acute renal failure
must be serially monitored to ensure that the intravenous fluid rate is sufficient to maintain hydration. Remember that "two-times-maintenance"
is based on maintenance for that animal being that of a healthy animal. Constant reassessment of body weight, skin turgor
and urine output often leads to adjustments in fluid rate multiple times a day. I also measure central venous pressure if
possible as a more objective measure of hydration status.