PU/PD Flashcards
polyuria
excessive volume excretion of urine
pollakiuria
excessive frequency/urgency of urination
dysuria
difficult or painful urination
stranguria
slow, painful urination, caused by muscular spasms of the urethra and bladder
polydipsia
excessive volume drinking
what is the definition (numbers) of polyuria?
> 50 mL/kg/day
very difficult to determine without special metabolic cages or urinary catheterization
what is the definition (numbers) of polydipsia?
> 60-80 mL/kg/day
in the majority of causes, is the patient having primary polyuria or primary polydipsia?
primary polyuria with secondary/compensatory polydipsia
what factors are involved in maintaining water balance physiologically?
- hypothalamus and pituitary: ADH and vasopressin
- kidneys: respond to signals and increase blood volume and plasma osmolality
then thirst center gets activated
what two organs are you concerned about with PU/PD?
brain, kidney
what differential diagnoses would you think of relating to the brain with a PU/PD patient?
- central diabetes insipidus
- primary polydipsia
what differential diagnoses would you think of relating to the kidneys with a PU/PD patient?
- primary nephrogenic DI
- secondary nephrogenic DI
- osmotic diuresis
what does the word diabetes actually translate to?
greek: siphon; to pass through
how common are your differential diagnoses for PU/PD?
central DI: rare
primary polydipsia: less common
primary nephrogenic DI: very rare
secondary nephrogenic DI: common
osmotic-induced diuresis: common
what is the general principle of osmotic diuresis?
ADH is normal or increased, but other osmotic agents keep water from leaving tubule
what are specific rule-outs you should think about with osmotic diuresis?
- diabetes mellitus
- post-obstructive diuresis
- chronic kidney disease
- fanconi’s syndrome
what is the basis of diabetes mellitus?
excess glucose overwhelms renal reabsorption
the pancreas has decreased insulin secretion, too much insulin overwhelms the kidneys’ ability to absorb. Glucose pulls water out: osmotic issue
what is fanconi’s syndrome?
tubular defect prevents various solute reabsorption, including glucose and Na+. get diuresis! receptors defective and can’t pull solutes into cells
basenji’s prone! and small breed dogs
post-obstructive diuresis
“blocked tom cat”
urea can’t get out and accumulates until obstruction relieved
also some tubular damage from pressure
how can chronic kidney disease cause diuresis?
decreased functional nephrons means less urea and sodium reabsorption
also loss of medullary gradient
what is secondary nephrogenic DI? (NDI)
- interference with ADH receptor
- interference with tubule cell function
- lack of medullary gradient
kidney functioning, but something interfering. disease won’t allow for gradient: get medullary washout and can’t conserve water
what osmotic diuresis rule-outs are common?
DM, post-obstructive diuresis, chronic kidney disease are common
fanconi syndrome uncommon
what are the major rule-outs with NDI?
- hyperadrenocorticism
- hypoadrenocorticism
- hyperthyroidism
- pyometra
- hypercalcemia
how does cushing’s cause secondary NDI and thus PU/PD?
- excess of glucocorticoids
- interferes with ADH receptors
- interferes with ADH release
- primary polydipsia?
how does addison’s cause secondary NDI and thus PU/PD?
- lack of glucocorticoids and mineralocorticoids!
- lack of ALDOSTERONE!! responsible for saving Na and dumping K+. leads to Na+ wasting.
- osmotic agent, get medullary washout
how can hyperthyroidism cause secondary NDI and thus PU/PD?
pt in a hypermetabolic state, increased cardiac output, increased blood flow, leads to decreased time for Na reabsorption. this makes for a decreased medullary gradient. primary polydipsia?
how can pyometra cause secondary NDI and thus PU/PD?
pyometra is e.coli bactera: releases endotoxins! this interferes with the ADH receptor by blocking it. PU/PD is often a presenting complaint for pyometra!
how can hypecalcemia cause secondary NDI and thus PU/PD?
interferes with function of ADH receptors and tubular cells
multifactorial and poorly understood!
what are causes of primary polydipsia? what does this lead to?
- hyperthyroidism
- hyperadrenocorticism
- hepatic disease
leads to overhydration and eventual medullary washout
kidneys are usually functioning properly in these cases!
what is psychogenic polydipsia?
learned behavior, usually dogs
what should you be differentiating polyuria from?
pollakiuria
frequency, straining, amount, urgency, blood, changing litter often, night time urination, accidents? etc
what happens to a patient with no ADH?
water channels don’t get inserted into the distal tubules = no water absorption = DIURESIS
what causes central diabetes insipidus?
- partial or complete lack of ADH
- trauma
- neoplasia
- idiopathic
is the polydipsia physiologic or pathologic? what questions should you be asking?
more exercise?
weather changes?
stress?
at water bowl more?
filling water bowl more?
drinking out of toilets recently?
PU/PD is a _________ problem
systemic! need to ask about systemic changes: weight loss, weight gain, V+/D+, neuro signs, sudden blindness?
what is the first diagnostic you should do for a PU/PD patient?
URINALYSIS
assess state of dehydration. if dehydrated, urine should be concentrated. recheck using first morning urine! animals don’t drink at night, and usually will concentrate at night
NEVER WITHOUT WATER! could cause AKI!
if diabetes mellitus is a top differential for a cat you are seeing, what should be something you absolutely should be checking for on a physical exam?
frosty paws!
if a patient’s urine is hypersthenuric, what would their USG be? what would clinical signs be?
dog: USG > 1.030/1.035
cat: > 1.040/45
NOT PU/PD!