Page 98 - Clinical Small Animal Internal Medicine

66 Section 2 Endocrine Disease

status, and recent changes in weight. Organomegaly and/
Box 8.1 Diseases associated with secondary
VetBooks.ir nephrogenic diabetes insipidus or lymphadenopathy may raise suspicion of a neoplastic
process. In cats, palpation for thyroid nodules may be
Renal failure
Hyperadrenocorticism
Hyperglycemia Hypoadrenocorticism useful in evaluating for possible hyperthyroidism. Females
should be examined for evidence of vulvar discharge.
Hypercalcemia Hypokalemia Pyelonephritis should be suspected in patients with flank
Pyelonephritis Hepatic disease or abdominal pain.
Pyometra Hyperthyroidism (cats) Before embarking on a diagnostic work‐up for the
Leptospirosis (dogs) Polycythemia cause of PU/PD, it is often useful to make sure the prob-
Acromegaly Neoplasia lem truly exists. This can be done through a combination
Renal medullary solute Drugs (i.e., anticonvulsants, of history and evaluation of the urine specific gravity to
washout glucocorticoids, diuretics) document isosthenuria or hyposthenuria.
It may also sometimes be useful to ask the owners to
quantify water intake at home (remember to discuss
Nephrogenic DI can be further classified as primary access to other sources of water such as ponds, pools,
and secondary. The primary form of NDI is due to an toilets, etc.). Water consumption may vary from day to
extremely rare congenital structural or functional defect day so assessing water intake over several days may be
of the kidneys. Secondary NDI is the most common necessary. Polydipsia is documented in a patient with a
cause of polyuria and polydipsia in veterinary medicine water intake in excess of 100 mL/kg/day for dogs and
and is due to nonrenal causes, which interfere with the 45 mL/kg/day in cats.
kidneys’ ability to respond to AVP. The urine should also be evaluated for other diagnostic
clues.
Signalment
● Urine specific gravity (USG): Patients with normal
renal function who are truly polydipsic should have a
Polyuria and polydipsia (PU/PD) can occur in any breed of USG <1.030 in dogs and <1.035 in cats. If the USG is
dog or cat and at any age. However, certain diseases are consistently >1.035, other problems such as inconti-
associated with specific age groups and breeds. For exam- nence or dysuria should be considered.
ple, primary polydipsia would be a consideration for a ● Glycosuria: The presence of glucose may be suggestive
young dog whereas hyperadrenocorticism may be sus- of diabetes mellitus or, in some cases, primary renal
pected in a middle‐aged patient. Reproductive status glycosuria.
should also be considered as conditions such as pyometra ● Proteinuria: In conjunction with a low USG, proteinu-
can result in these clinical signs. In addition, diseases ria may be seen in patients with hyperadrenocorti-
such as Fanconi syndrome have been described in basen- cism, pyelonephritis, lower urinary tract infection, or
jis and Norwegian elkhounds. glomerulonephritis. A urine culture and/or urine
protein:creatinine ratio may be warranted.
History and Clinical Signs Initial diagnostics should also include a complete
blood count (CBC), chemistry profile with electro-
A thorough history is critical when evaluating a patient lytes, and a total thyroxine level in middle‐aged to
with polyuria and polydipsia. A recent history of trauma, older cats. A urine culture should be performed even
drug administration, (including topical medications), or in the face of an inactive sediment. Patients with
environmental change will help narrow the list of differ- underlying diseases such as hyperadrenocorticism or
entials. Loss of appetite and lethargy may raise the pos- diabetes may be unable to mount an appropriate
sibility of liver or renal disease whereas polyphagia may immune response so pyuria may not be noted. In addi-
increase the index of suspicion for hyperthyroidism in tion, dilute urine can make it difficult to identify
cats or hyperadrenocorticism in dogs. Diet should be bacteriuria.
discussed as well as salt content may affect water intake. These initial tests often provide some direction as to
the underlying cause (e.g., presence of azotemia or an
Diagnosis elevation in liver values). In dogs, leptospirosis should be
considered as a cause of PU/PD in endemic areas even in
the absence of liver or renal abnormalities although the
First‐Tier Diagnostic Tests exact mechanism for why this occurs is not clearly
Physical examination findings in patients with PU/PD understood.
may be unremarkable or nonspecific. Special attention The serum sodium concentration may also provide
should be paid to body condition, muscle mass, hydration some insight into whether the patient has primary