Polyuria is defined as excessive urine production of more than 3 liters per day in adults. It can be caused by either water diuresis or solute diuresis. Water diuresis is characterized by dilute urine of less than 250 mosmol/L and is caused by problems with antidiuretic hormone production or kidney response. Solute diuresis produces urine of more than 300 mosmol/L and is caused by increased glucose, urea, or other solutes. Polyuria can be pathological due to diseases like diabetes, pharmacological due to medications or fluids, or physiological for compensatory reasons.

2. polyuria
 excessive or abnormally large production
and/or passage of urine (>3 L per day in
adults).
 Frequent urination – accompanying
syndrome
 Diuresis – increased production and passage
of urine

3. Mechanisms of polyuria
 Due to excretion of increased
nonabsorbable solutes(such as glucose)
– SOLUTE DIURESIS
 Due to excretion of increased
water(from a defect in ADH production
or renal responsiveness) – WATER
DIURESIS

4. Water diuresis
 Urine output >3 L per day
 Urine is dilute (<250 mosmol/ L)
 Causes – polydipsia , central diabetes
insipidus , nephrogenic diabetic
insipidus

5. Solute diuresis
 Urine output > 3 L per day
 Urine osmolarity > 300 msmol/L
 Causes – increased glucose,mannitol or
urea medullary cystic
diseases,obstruction,diuretics

6. TYPES OF POLYURIA
I. pathological polyuria
 Polyuria caused by a disease of the
kidney or disorder anywhere in the body
eg. Diabetes mellitus, diabetes
insipidus,liver failure

7. II. Pharmacological polyuria
 Polyuria caused by administerd fluids or
by medication such as glucocorticoids or
diuretics

8. III. Physiological poyuria
 Compensatory mechanism to increased
fluid intake
 Cold diuresis – in hypothermia as a
result of peripheral
vasoconstriction,hyperglycemia and
decresed renal tubular reabsorption
 Altitude diuresis

9. polydipsia
 Increase in thirst
 Often appear in conjugation with
polyuria
 It can either be cause or effect of
polyuria

10. Psychogenic polydipsia
 Also called primary polydipsia
 Patient intakes increased amount of fluid
due to sensation of having a dry mouth
 Most commonly due to phenothiazine
medication used in mental disorders

11. Diabetes insipidus
 Disorder that causes polyuria
 due to impaired urinary concentrating
ability leading to increased free water
clearance
 Polydipsia present
 Plasma sodium may be normal

12. .
 Free water is the water free of solutes
 Free water clearance = urine flow rate –
osmotic clearance
 Osmotic clearance = urine flow rate x
urine osmolality/plasma osmolality

13. Two types of DI
 Central DI – amount of ADH produced
by the pituitary is below normal
 Nephrogenic DI – kidney’s ability bto
respond to ADH is defective