Polyuria & Polydipsia Flashcards
What measurements indicate polydipsia and polyuria?
PD = >100 mg/kg/day (normal is 50-60 mg/kg/day)
PU = >50 mg/kg/day (difficult to measure without hospitalization and catheter placement
What are 12 common differentials for PU/PD?
- diabetes mellitus
- chronic renal insufficiency
- Cushing’s
- neoplasia - lymphoma, AGASACA, multiple myeloma, pheochromocytoma
- hypercalcemia
- diabetes insipidus
- liver failure
- hyperthyroidism
- endotoxemia - pyometra, prostatic abscess
- Addison’s
- iatrogenic - steroids, diuretics, levothyroxine, high salt diet
- pyelonephritis
What are 3 common differentials for PU/PD with polyphagia?
- DM
- Cushing’s
- hyperthyroidism
What are 4 common differentials for PU/PD with weight loss?
- renal/hepatic failure
- neoplasia
- DM
- hyperthyroidism
What are 2 common differentials for PU/PD with skin/coat changes?
- Cushing’s
- hyperthyroidism
What is most likely the cause of PU/PD with vulvar discharge?
endotoxemia –> pyometra
What are some abnormalities on physical exam that may give some insight into the cause of PU/PD?
- small kidneys
- small or large liver
- mass felt on rectal exam (AGASACA)
- bilateral cataracts (DM)
- lymphadenopathy (lymphoma, neoplasia)
What are some CBC/Chemistry findings that can give insight into the cause of PU/PD?
- anemia - CKD
- eosinophilia, lymphocytosis - Addison’s
- BG - DM vs DI vs renal glucosuria
- serum calcium - hypercalcemia, need to investigate cause!
- liver function (BUN, albumin, glucose, cholesterol, bilirubin) and enzymes (ALT, ALP, AST, GGT)
- renal values (BUN, CREAT)
How can pre-renal azotemia be ruled out in cases of PU/PD?
urinalysis:
- USG >1.035 only seen in PU/PD patients with marked glucosuria
- USG <1.008 makes renal insufficiency less likely
- glucosuria suggests DM or primary renal glucosuria
How is diagnostic imaging used to diagnose the cause of PU/PD?
- adrenal gland size
- evidence of neoplasia
- liver and kidney size
- pyometra
- prostatomegaly
How is a patient tested for central diabetes insipidus? What is important to note about this test?
trial therapy with vasopressin (dDAVP)
it may take several days to a week to overcome medullary washout of the kidneys before an effect is seen
How is a patient tested for psychogenic polydipsia?
modified water deprivation test (WDT) –> only done if all other diagnostics have been exhausted
- deliberately withhold water and food and frequently monitor hydration status and USG to detect if the animal can concentrate urine (>1.030)
- if urine is concentrated = psychogenic PD
- if urine is not concentrated = DI, then give vasopressin (dDAVP)
When should a modified water deprivation test NOT be performed?
- illness
- azotemia
- dehydration
- hypercalcemia
