Paediatrics: Polyuria and frequency

2021-03-04 12:00 AM

This is often subjective and difficult to assess, particularly in small children.

Polyuria and frequency

This is often subjective and difficult to assess, particularly in small children. Frequency can be considered to be the inappropriate and frequent passage of small amounts of urine. Polyuria can be quantitatively defined as the passage of greater than 2000mL/1.73m2 per 24hr period.

Assessment of polyuria and frequency requires a detailed history of urinary frequency habit.

Causes of polyuria

  • Renal disorders:

o chronic kidney disease;

o post-obstructive uropathy;

o nephrogenic diabetes insipidus;

o Fanconi syndrome.

  • Metabolic/endocrine disorders:

o diabetes mellitus;

o cranial diabetes inspidus;

o hypoadrenalism.

  • Excess and inappropriate water intake: psychogenic polydipsia.

Causes of urinary frequency

  • Urinary tract infection.
  • Bladder irritability and instability.
  • All causes of polyuria.
  • Small bladder capacity.

Investigations

Baseline screening investigations should include the following.

Urine

  • Urinalysis by urine dipstick testing.
  • Urine culture.
  •  Urine osmolality.

Blood

  • Urea and electrolytes.
  • Plasma osmolality.
  • Blood glucose (random or fasting).