PU/PD Flashcards
Polydipsia definition (PD)
water intake is greater than 100ml/kg/day
- >50 in cats
polyuria definition
urine output is >50ml/kg/day compared to a normal output of 1-2ml/kg/hour
USG < __ confirms PU while USG >__ is unlikely PU
1.020, 1.030
Antidiuretic Hormone
produced in the hypothalamus then stored/released from the posterior pituitary targeting V2 receptors and creating increased aquaporins
central diabetes insipidus is __ ADH deficiency while nephrogenic is a lack of__ to ADH
partial/complete, responsiveness
what is the most common cause of PU/PD in small animals?
secondary nephrogenic DI
primary is rare
primary polydipsia is __ while primary polyuria is __
behavioral, impaired renal concentrating capacity
psychogenic polydipsia
behavioral disorder of unknown cause, anxiety is speculated
non-pathologic polydipsia
pain, stress, hyperthermia, heat, exercise
Hyperadrenocorticism
glucocorticoids inhibit ADH release and renal response to ADH
Hepatic Disease
unknown; behavorial secondary to encephalopathy vs decreased urea concentration in medullary insterstitium
hyperthyroidism
unclear, decreased medullary solute washout from increased renal blood flow vs thyrotoxicosis- induced psychogenic polydipsia
primary polydipsia differentials
psychogenic polydipsia
non-pathologic polydipsia
hyperadrenocorticism
hepatic dz
hyperthyroidism
primary polyuria - extra renal causes
- central DI
- hypercalcemia
- hypokalemia
- pyometra
- hypoadrenocorticism (hyponatremia)
- DM
- Hypersomatotropism (acromegaly)
- pheochromocytoma
- hyperviscosity syndrome/polcythemia
- neoplasia
- low protein diet
-splenic hemangiosarcoma - drug induced secondary nephrogenic DI
Central DI
absent or decreased ADH production
hypercalcemia
downregulation of aquaporin, impaired ADH action, impaired NaCl transport in loop of henle, decreased GFR from vasoconstriction, and eventually tubular dysfunction from nephrocalcinosis
hypokalemia
downregulation of aquaporin/decreased ADH response
pyometra
bacterial endotoxin competitively inhibits and damages ADH receptors and decreases NaCl transport into medullary interstitium
hypoadrenocorticism
decreased medullary osmolarity from sodium loss which also impairs normal stimuli for ADH release in dehydration
Diabetes mellitus
osmotic diuresis from glucosuria
pheochromocytoma
catecholamine- induced inhibition of ADH release and response
hyperviscosity syndrome/polycythemia
decreased ADH secretion from inhibition from ANP
neoplasia (intestinal leiomyosarcoma)
paraneoplastic secondary nephrogenic DI
low protein diet
loss medullary gradient from decreased urea nitrogen
splenic hemangiosarcoma
paradoxical: compensatory polyuria following ADH release from hypovolemia in addition to stimulated thirst mechanism
drug induced secondary nephrogenic DI
impaired renal ADH response. Vasopressin, ofloxacin, amp b, aminoglycosides, cisplatin, etc.
primary polyuria - renal causes differentials
- Primary/congenital nephrogenic DI
- CKD
- AKI
- pyelonephritis
- fanconi syndrome
primary/congenital nephrogenic DI
mutation of V2 receptors or aquaporin
CKD
decreased number of functional nephrons -> osmosis diruesis of remaining nephrons + distortion of medullary architecture -> disruption of counter-current mechanism
AKI or post- obstructive diuresis
osmotic diuresis
Pyelonephritis
loss of medullary gradient from interstitial inflammation + impaired ADH action from endotoxemia
fanconi syndrome
osmotic diuresis from renal glucosuria
> 100ml/kg/day __ PD and 80-100 is __
confirms, suggestive
if you see hyperglycemia on a chem what do you think of first?
DM
elevated ALP and hypercholesterolemia is suggestive of what?
hyperadrenocorticism
hypoalbuminemia , hypocholesterolemia, low BUN, hypoglycemia +/- elevated liver enzymes indicates what?
liver disease
differentials for azotemia
CKD, AKI, pyelonephritis
differentials for hypothenuria (USG <1.008)
central DI
primary nephrogenic DI
primary psychogenic PD
hypercalcemia
hyperadrenocorticism
liver disease
pyelonephritis or pyometra
hemangiosarcoma/hemorrhage
lack of app concentration (USG 1.008 -1.030) differentials
CKD
Hypercalcemia
cushings
liver disease
DM
pyelonephritis or pyometra
hyponatremia
hypokalemia
concentrated urine (USG > 1.030) differential
NOT PU
intermittent PU
DM
Fanconi syndrome
what additional dx tests can be performed for pu/pd?
- abdominal ultrasound
- urine culture (pyelonephritis)
- MAT+ PCR (lepto)
- Bile acid stimulation Test (liver dz)
- endocrine testing
when is the water deprivation test indicated?
when the remaining dx’s are primary/psychogenic polydipsia (most commoon) and central and nephrogenic DI
desmopressin is a synthetic form of __ that if after administered the patient decreases water intake and increases USG indicates __ while an absent/decreased response would indicate __
ADH, central DI, primary nephrogenic DI or primary polydipsia
