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Chronic Kidney Disease, Occult (Asymptomatic) 167

possible, always submit the entire lesion for SUGGESTED READING AUTHOR: Dennis B. Bailey, DVM, DACVIM
histopathologic evaluation. Waltman SS, et al: Clinical outcome of nonnasal EDITOR: Kenneth M. Rassnick, DVM, DACVIM
VetBooks.ir Technician Tips 2003). Vet Surg 36:266-271, 2007. Diseases and Disorders
chondrosarcoma in dogs: thirty-one cases (1986-
When CSA is suspected, use caution when
positioning the patient for radiographs to
minimize pain and risk of pathologic fracture.

Chronic Kidney Disease, Occult (Asymptomatic) Client Education
Sheet

BASIC INFORMATION stage I or II but has been documented in Etiology and Pathophysiology
stages III and IV. • CKD is the result of a variety of insults to
Definition • CKD causing overt clinical signs (p. 169) the kidney. If the glomerulus is irreversibly
• Chronic kidney disease (CKD): an abnormal- damaged, the associated tubule will degener-
ity in renal structure or function existing for Synonyms ate, and vice versa.
longer than 3 months • Subclinical CKD, latent CKD, preclinical • Histopathologic renal lesions consist
• International Renal Interest Society (IRIS) CKD, renal insufficiency primarily of inflammatory infiltrates in the
staging system for CKD: classification scheme • The terms kidney failure and chronic renal tubulointerstitium, in the glomeruli, or in
for canine and feline CKD based on serum failure are no longer preferred for use. both simultaneously. Concurrent fibrosis is
creatinine and symmetric dimethylarginine Epidemiology usually present to various degrees. Additional
(SDMA), with substages for proteinuria and findings include tubular atrophy and glo-
blood pressure (BP): SPECIES, AGE, SEX merular sclerosis or senescence.
○ At risk: creatinine < 1.4 mg/dL • CKD is one of the most common geriatric • As nephrons are lost, the remaining nephrons
(<124 mmol/mL), dogs; < 1.6 mg/dL diseases of cats. hypertrophy. Although initially adaptive,
(<141 mmol/mL), cats. SDMA ≤ 14 mcg/ • Canine CKD occurs less frequently, but glomerular hypertension damages the
dL, dogs and cats. History suggests manifests in geriatric patients and juvenile nephron, leading to further nephron loss.
increased risk of CKD (e.g., exposure to patients (congenital CKD). After a certain amount of damage has been
nephrotoxic drugs, breed, old age) sustained (generally when creatinine >
○ Stage I: creatinine < 1.4 mg/dL GENETICS, BREED PREDISPOSITION 3.5 mg/dL [>309 mmol/mL]), kidney disease
(<124 mmol/mL), dogs; < 1.6 mg/dL • Multiple studies have not identified a breed may be progressive despite resolution of the
(<141 mmol/mL), cats. SDMA > 14 mcg/ predisposition in cats, but reports do exist of initiating cause.
dL, dogs and cats. Nonazotemic. Some increased frequency in Maine coon, Abys- • The specific cause of CKD is often
other renal abnormality present (e.g., sinian, Siamese, Russian Blue, Burmese, and undetermined.
inadequate concentrating ability without Ragdoll cats. ○ Tubulointerstitial nephritis: most common
identifiable nonrenal cause; abnormal • Familial nephropathies may lead to early- cause in cats
renal palpation, and/or abnormal renal onset CKD and are reported in numerous ○ Glomerular disease: most common cause
imaging findings; persistent proteinuria breeds of dogs and cats (p. 169). in dogs
of renal origin; abnormal renal biopsy ○ Other demonstrable causes: amyloidosis,
results; progressively increasing creatinine RISK FACTORS renal dysplasia, polycystic kidney disease,
concentration) Advanced age, prior episode of acute kidney lymphoma, chronic pyelonephritis,
○ Stage II: creatinine 1.4-2 mg/dL injury (including nephrotoxic exposure, obstruc- obstructing nephroliths or ureteroliths,
(124-177 mmol/mL), dogs; 1.6-2.8 mg/dL tive disease, or infectious disease), familial/breed vasculitis, infarction, and sequelae to acute
(141-248 mmol/mL), cats. Mild renal disposition kidney injury with incomplete resolution
azotemia (lower end of the range lies ○ Obstructive nephropathy from previous
within the reference range for many ASSOCIATED DISORDERS or current ureterolithiasis is increasingly
labs, but the insensitivity of creatinine Cardiovascular disease (e.g., systemic hyperten- recognized in cats.
as a screening test means that animals sion in cats and dogs), endocrinopathies (e.g.,
with creatinine values close to the upper hyperthyroidism and hyperaldosteronism in DIAGNOSIS
end of the reference range often have cats, renal secondary hyperparathyroidism in
excretory failure). Clinical signs usually cats and dogs), and urinary tract infections Diagnostic Overview
absent (UTIs) CKD may be diagnosed based on structural
○ Stage III: creatinine 2.1-5 mg/dL (e.g., nephrolithiasis, renal size/shape changes,
(186-442 mmol/mL), dogs; 2.9-5 mg/dL Clinical Presentation polycystic disease) or functional (e.g., protein-
(256-442 mmol/mL), cats. Moderate renal HISTORY, CHIEF COMPLAINT uria, azotemia, inadequately concentrated urine)
azotemia. Systemic clinical signs often Occult CKD is usually detected incidentally by abnormalities.
present. routine geriatric or pre-anesthetic screening or
○ Stage IV: creatinine > 5 mg/dL (>442 mmol/ during investigation of unrelated illness. Differential Diagnosis
mL), dogs and cats. Severe renal azotemia. Azotemia:
Systemic clinical signs usually present PHYSICAL EXAM FINDINGS • Increased blood urea nitrogen (BUN) from
• Occult CKD: CKD in which no clinical Frequently no abnormal findings. Small or extrarenal factors (e.g., high-protein diet,
signs are present. Usually corresponds to IRIS irregular kidneys may be palpated. gastrointestinal bleeding)

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