Polyuria Flashcards
What is the difference between polyuria and high urinary frequency and how do you differentiate between the 2 clinically?
In both, will be passing urine more often than before.
- polyuria - passing abnormally large volumes of clear urine each time
- high urinary frequency - volume voided each time will be normal or reduced
collect 24 hour urine sample
What are Dx of polyuria?
ENDOCRINE:
Diabetes Mellitus
Diabetes insipidus
Hyperthyrodism
HEART FAILURE
ELECTROLYTE IMBALANCE:
- hypercalcaemia
- hypokalaemia
MEDICATION:
Diuretics, caffeine, alcohol, lithium
PSYCHIATRIC
• Psychogenic polydypsia
Renal failure
hypercalcaemia
BONE metastases - hypercalcaemia
Steroids and Cushing’s cause polyuria by causing DM
What questions will help you narrow down the cause of polyuria?
What is the temporal pattern of urine output?
Any fatigure, weight loss, recurrent infections? suggests diabetes
Any LUTS? frequency, urgency, hesitance, terminal dribbling, incomplete voiding
Any pain, change in urine frequency, colour, smell? UTI
Drug history- diuretics
Family history - DM
What will you ask about on PMHx of polyuria?
RENAL
History of renal problems or triggers of renal problems? vasculitides, urinary retention,
hypertension
CANCER:
Older patients: ask about cancer and known bony involvement
PSYCHIATRIC
Any psychiatric disorders
What should you look for in the drug history of someone with polyuria?
Diuretics, lithium (causes nephrogenic DI)
What should you look for in the family history of someone with polyuria?
Diabetes, any cancers
Why do we not need to urinate when we sleep?
at night, the kidneys concentrate the urine in order to retain fluid
What is nocturia a sign of?
(in absence of other causes such as BPH) early sign of loss of ability to concentrate urine.
What are simple tests in someone with polyuria? What are they used to detect/exclude?
Capillary blood glucose (DM) and urinalysis (UTI + glucose and ketonuria for DM)
What are further Ix for polyuria?
simple tests are capillary blood glucose and urinalysis
Fasting glucose, urine osmolality, electrolytes (primary polydypsia will have hypOnatremia), urea, creatinine, EGFR, calcium and TFTs
What are the two different mechanisms that can cause polyuria and how do they reflect in the urine osmolality
Inability to reabsorb solutes - remain in the urine and keep water with them -> high urine osmolality
Inability to reabsorb water (can be due to ADH deficiency) -> low urine osmolality
how will the results of electrolytes differ in someone with polydipsia to the other pathologies of polyuria?
polydipsia - serum sodium will be diluted due to excessive water intake
other pathologies - will be high because of dehydration
Why do we test for urea, creatinine and eGFR in patients with polyuria?
to rule of out chronic kidney disease
Polyuria. No DM. Urine osmolality low and normal serum sodium.
What is the differential?
diabetes insipidus
What are the types of diabetes insipidus and whitest can be done to differentiate between then.
Cranial and nephrogenic
cranial - problem with the posterior pituitary (low/no ADH secretion). kidneys are normal
nephrogenic - problem with the kidneys, not sensitive to ADH
water deprivation test - give desmopressin.
- cranial DI - can now concentrate the urine
- nephrogenic - no change in urine concentration