Page 726 - Small Animal Internal Medicine, 6th Edition

698 PART V Urinary Tract Disorders

in these CKD cats, but the primary gastric lesions observed of 8.9% of body weight in the year preceding diagnosis, and
were fibrosis and mineralization. Vomiting is more common weight loss accelerated as the disease progressed. Body
VetBooks.ir in uremic dogs than in cats, possibly as a consequence of the weight <4.2 kg at the time of diagnosis was associated with
significantly shorter survival time. In a study of dogs with
differences in gastric lesions observed in cats and dogs with
CKD. Stimulation of the chemoreceptor trigger zone by a
was associated with improved survival. Vomiting is more
uremic toxin may contribute to vomiting in patients with CKD, higher body condition score at the time of diagnosis
CKD. common in dogs with CKD than in cats.
On physical examination, poor body condition and dull
CARDIOVASCULAR COMPLICATIONS dry hair coat are evidence of chronic disease. Dehydration is
Systemic hypertension is present in 20% to 30% of dogs and common because of inadequate food intake and insufficient
cats with CKD and in 50% to 80% of dogs with glomerular water intake to keep pace with PU. Oral ulcers may be
disease. Normal blood pressure in dogs and cats is similar to observed in dogs with CKD. Pallor may be evident if anemia
that of humans (i.e., systolic 120 mm Hg, diastolic 80 mm is present. Clinical manifestations of bone demineralization
Hg), but interactions in the hospital setting increase the are extremely rare in adult dogs and cats with CKD, but
blood pressure of dogs and cats (so-called white coat effect), fibrous osteodystrophy can be dramatic in young growing
making identification of mild to moderate hypertension dif- dogs with uremia (so-called rubber jaw). Despite a lack of
ficult. Factors contributing to hypertension include renal clinical signs, CKD has been shown to be associated with
ischemia associated with CKD that results in activation of histologic evidence of decreased cancellous and cortical
the renin-angiotensin system and increased sympathetic bone mineral density in cats. The presence of subcutaneous
nervous system activity. An intrarenal mechanism for edema or ascites suggests the possibility of glomerular
sodium retention plays an important role in the hyperten- disease.
sion in patients with glomerular disease. Clinical and patho-
logic manifestations of systemic hypertension include ocular Clinicopathologic Findings and Imaging
abnormalities (e.g., retinal detachment, retinal hemorrhages, Nonregenerative anemia may be observed on the CBC but
retinal vascular tortuosity) and cardiovascular abnormalities can be masked by dehydration—that is, the hematocrit
(e.g., left ventricular enlargement, medial hypertrophy of should be evaluated in conjunction with total protein con-
arteries, murmurs, gallop rhythms). centration. Mature neutrophilia and lymphopenia reflect the
stress of chronic disease. Platelet numbers typically are
METABOLIC COMPLICATIONS normal, but platelet function may be abnormal. Serum
Many small peptides are normally filtered by the kidney, potassium concentrations usually are normal in patients
reabsorbed, and degraded in the proximal tubular cells. Loss with CKD unless oliguria or anuria develop. Azotemia is
of this clearance function can result in metabolic derange- present if 75% or more nephrons are nonfunctional, and
ments because many of these peptides are hormones. Periph- hyperphosphatemia is observed if 85% or more nephrons are
eral insulin resistance and mild fasting hyperglycemia nonfunctional. Serum total calcium concentration is normal
(<150 mg/dL) are common in uremia, but not clinically rel- to slightly low or, rarely, high. Bicarbonate concentration
evant. Excess gastrin increases the stimulation of acid secre- usually is only mildly decreased, and moderate to severe
tion in the stomach and contributes to uremic gastroenteritis, metabolic acidosis is a late finding in dogs and cats with
and excess glucagon may contribute to negative nitrogen CKD.
balance and tissue catabolism. CKD is an important nonthy- In dogs, isosthenuria develops when 67% or more neph-
roidal illness, which can cause confusion in diagnosis of rons become nonfunctional (USG, 1.007-1.015), but some
hyperthyroidism in older cats and must be taken into con- cats with CKD retain concentrating ability after the onset of
sideration when evaluating treatment options. Plasma corti- azotemia. In one study, cats with a 58% to 83% loss of func-
sol concentrations may be slightly increased, and increased tional nephrons could produce concentrated urine (USG,
mineralocorticoids may contribute to hypertension. 1.022-1.067). Thus a cat with azotemia and relatively concen-
trated urine does not necessarily have prerenal azotemia. The
Clinical Findings magnitude of proteinuria is a reflection of intraglomerular
PU and PD may be the first abnormalities noted by obser- hypertension and may be an indicator of the rate of progres-
vant owners of dogs and cats with CKD. In dogs, nocturia sion of renal disease. In one study, a urine protein-to-creat-
may be noted first because the animal begins waking the inine (UPC) ratio >1.0 was associated with more rapid
owner up at night to be allowed outside to urinate. If PU and progression and increased risk of developing uremic crisis
PD are not recognized, nonspecific signs of uremia may be or death. Severe persistent proteinuria with an inactive urine
the first abnormalities the owner detects. Anorexia, weight sediment suggests primary glomerular disease. Microalbu-
loss, and lethargy are common in dogs and cats with CKD. minuria refers to urine protein concentrations >1 mg/dL but
Client surveys have shown that poor appetite is common in <30 mg/dL. Microalbuminuria is an early indicator of endo-
cats with CKD and may negatively impact the animal’s thelial damage and may be a risk factor for progression of
quality of life as perceived by the owner. In a study of cats renal disease. It increases with age and in association with
with CKD, affected animals were shown to have lost a median other systemic diseases, but its prognostic value is uncertain