PATIENT HISTORY
Obtaining a thorough clinical history is useful in determining the chronicity of a patient's kidney disease. Polydipsia and
polyuria are classic signs of kidney disease but are not present in all cases. Their presence does not differentiate AKI from
CKD, but their duration may help distinguish between the two. In one study, 70% of cats with CKD presented with an owner complaint
of polydipsia and 31% with polyuria.14
The discrepancy in owners' reporting of polydipsia more frequently than polyuria is likely because owners are better able
to detect abnormalities in water consumption than abnormalities in urination volume or frequency. About half of dogs and cats
with AKI are oliguric or anuric.12,13,15
Decreased appetite, vomiting, or other gastrointestinal signs can be associated with both AKI and CKD, but these signs would
be of recent onset with AKI. In one study, decreased appetite was present in 33% and vomiting in 22% of cats with CKD.14 Often these signs were waxing and waning for months. In addition to complete refusal of food, other common signs include
taking longer to eat or showing interest in food without actually eating. Historical weight loss suggests chronic disease,
although owners frequently do not recognize weight loss when it is slowly progressive and subtle. Compensatory mechanisms
can mask a great degree of the patient's clinical signs at home, leading owners to miss subtle changes. The history should
also include questions about exposure to medications (administered or accidental) or possible toxins.
PHYSICAL EXAMINATION
Figure 1. A cat with poor body condition secondary to CKD. Note the generalized severe muscle wasting, including the epaxial
muscles.
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A thorough physical examination can help differentiate between AKI and CKD. Initially, most patients with AKI without concurrent
disease processes have a normal body condition. However, because kidney disease is a highly catabolic disease, muscle loss
can occur rapidly. Although weight loss and poor body condition are not specific for kidney disease, a poor body condition
with diffuse muscle wasting and an unkempt coat are often some of the first characteristics noted on physical examination
of a patient with CKD (Figure 1). Palpation of the epaxial muscles often reveals subtle but marked muscle loss. Small, irregular kidneys on abdominal palpation
support a diagnosis of CKD, while normal or large kidneys can be associated with either AKI or CKD.
The prevalence of hypertension is 9% to 93% in dogs with CKD16-21 and 19% to 65% in cats with CKD.22-24 With AKI, 87% of dogs25 and 30% of cats are hypertensive (Worwag S, Langston CE, Unpublished data, 2009). Thus, the presence of hypertension does
not distinguish between AKI and CKD. Because the eyes are a target of hypertensive damage, retinal examination is indicated
in any patient with renal disease and is quick and easy to do with an indirect lens. The most common ocular manifestation
of systemic hypertension is exudative retinal detachment.26 Retinal edema can be seen as an early manifestation of systemic hypertension and appears as "pseudonarrowing" of retinal
arterioles. Dilation and tortuosity of retinal vessels, retinal hemorrhage, retinal detachment, and retinal degeneration are
seen more commonly with chronic hypertension.26,27 Identification of any of these ocular signs should prompt blood pressure measurement. Ocular lesions are identified in between
48% and 100% of cats and 20% and 62% of dogs with hypertension.24,28-32 Hypertensive retinopathy tends to gradually progress with chronic hypertension, but an acute rise in blood pressure may
precipitate an acute exudative retinal detachment or hyphema.27
Clinical signs of CKD may be less pronounced when compared with those of AKI with the same level of azotemia,33
although we have observed that some patients with early AKI have minimal clinical signs, which worsen over the subsequent
several days if recovery is not prompt. As with the patient history, the physical examination is just one of multiple pieces
in this clinical puzzle.
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