Page 708 - Small Animal Internal Medicine, 6th Edition

680 PART V Urinary Tract Disorders

neoplasms, but there is no discernible associated inflamma- femoral artery embolism), or sudden blindness may occur
tory or neoplastic disease in up to 50% of dogs with reactive because of retinal detachment resulting from systemic
VetBooks.ir systemic amyloidosis. hypertension.
Physical examination findings usually are related to the
The cause of species differences in the tissue tropisms of
reactive amyloid deposits is unknown. In the dog, amyloid
poor hair coat, dehydration, oral ulceration, small irregu-
AA deposits are most common in the kidney, and clinical presence of CKD and uremia (e.g., poor body condition,
signs are caused by renal failure and uremia. The spleen, lar kidneys). Other physical examination findings may be
liver, adrenal glands, and gastrointestinal tract also may be related to the presence of underlying infectious, inflamma-
involved, but associated clinical signs are rare. In the cat, tory, or neoplastic diseases. Affected Shar Pei dogs may have
there is widespread deposition of amyloid deposits, but clini- a previous history of so-called Shar Pei fever, episodic joint
cal signs are due to renal failure and uremia. The Shar Pei swelling usually involving the tibiotarsal joints, and high
dog, Siamese cat, and Oriental Shorthair cat can be excep- fever that resolves within a few days, regardless of treat-
tions to these general rules. Severe liver deposition of amyloid ment. Some physical examination findings may be related
can cause rupture of the liver and acute hemoabdomen in to severe protein loss (e.g., ascites, edema, poor body condi-
these breeds. Within the kidney itself, the distribution of tion and hair coat). Retinal hemorrhages, vascular tortuos-
amyloid deposits varies among species. For example, amy- ity, and retinal detachment may occur because of systemic
loidosis is primarily a glomerular disease in the dog, whereas hypertension.
amyloid deposits may have a predominant medullary distri-
bution in the cat. Laboratory Findings
A careful search for known associated diseases (see Box 40.1)
is a crucial part of the diagnostic evaluation, despite the fact
CLINICAL FINDINGS that the glomerular disease ultimately is idiopathic in most
cases. Marked persistent proteinuria with inactive urine
Most animals with glomerular disease are middle-aged or sediment is the hallmark of glomerular disease. Increased
older at presentation. There is no sex predilection in dogs, numbers of hyaline casts and occasionally lipid droplets may
but approximately 75% of cats with GN are males. Any breed be observed in the urine sediment of animals with nephrotic
can be affected by glomerular disease, but familial forms of range proteinuria. Isosthenuria (urine specific gravity,
membranoproliferative GN have been reported in soft- 1.007-1.015) may be observed if 67% or more of the nephron
coated Wheaten Terriers (associated with mutations in the population has become nonfunctional, and earlier loss of
slit diaphragm proteins, nephrin, and Neph3/filtrin), Brit- concentrating ability may occur in animals with medullary
tany Spaniels (associated with hereditary deficiency of the deposition of amyloid (e.g., Abyssinian cats, Shar Pei dogs).
third component of complement), and Bernese Mountain Glomerulonephritis or amyloidosis can lead to chronic
dogs (often associated with positive serology for Borrelia renal failure with the expected biochemical abnormalities
burgdorferi). Hereditary defects of GBM type IV collagen (e.g., azotemia, hyperphosphatemia, metabolic acidosis).
occur as an autosomal recessive trait in English Cocker Hypoalbuminemia occurs in many dogs with glomerular
Spaniels and as an X-linked dominant trait in male Samo- disease (up to 75% of dogs with amyloidosis and 60% of dogs
yeds. Basement membrane defects are also suspected to with GN). Hypercholesterolemia occurs in most dogs with
occur in Doberman Pinschers and Bull Terriers. Familial glomerular disease (up to 60% of dogs with GN and 90% of
renal amyloidosis occurs in young Abyssinian, Siamese, and dogs with amyloidosis) but tends to be a nonspecific finding
Oriental Shorthair cats and in Shar Pei dogs. Familial amy- in cats with renal disease. Hypercholesterolemia may be
loidosis also has been reported in Beagles and English caused in part by increased hepatic synthesis of cholesterol-
Foxhounds. rich lipoproteins secondary to chronic hypoalbuminemia.
The UPC ratio avoids the confounding effect of total urine
History and Physical Examination Findings solute concentration (i.e., specific gravity) on the qualitative
There are several possible clinical presentations of dogs and assessment of proteinuria. It correlates well with 24-hour
cats with glomerular disease. Clinical signs may be related urinary protein loss but is much easier to measure—that is,
to the presence of CKD if more than 75% of the nephron it does not require a 24-hour urine sample. The magnitude
population has become nonfunctional (e.g., anorexia, weight of increase in UPC is roughly correlated with the nature of
loss, lethargy, polyuria, polydipsia, vomiting). This presenta- glomerular disease. UPCs are highest in dogs with glomeru-
tion is common. Signs may be related to an underlying infec- lar amyloidosis (often >10) and lowest in those with intersti-
tious, inflammatory, or neoplastic disease, or proteinuria tial renal disease (usually <10). Animals with GN have very
may be an incidental finding detected during diagnostic variable UPC (normal to >30). The presence of hematuria or
evaluation of another medical problem. Clinical signs occa- pyuria potentially can make the UPC difficult to interpret; it
sionally may be related to classical nephrotic syndrome (e.g., may cause a false-positive result. Normal UPC is < 0.5 in
ascites, subcutaneous edema). Signs may be related to dogs and < 0.4 in cats. In one study of dogs, results of UPC
thromboembolism (e.g., sudden onset of dyspnea with pul- obtained on three separate urine samples correlated well
monary embolism, sudden onset of paraparesis with iliac, or with a single determination made from a pooled sample of