1. Polyuria is defined as urine output greater than 5 ml/kg/hr or 2 L/m2/day. Causes include increased fluid intake, increased urinary solute excretion, and impaired urinary concentration.
2. Evaluation of polyuria involves obtaining a detailed history, clinical examination, and investigations including a 24-hour urine output measurement and urine and serum analysis.
3. Distinguishing between central and nephrogenic diabetes insipidus involves tests like the water deprivation test and vasopressin response test.
12. Dr.Padmesh. V
HISTORY:
Age of onset: Congenital / Acquired
H/O fever: UTI
Failure to thrive: DM, Nephrogenic D.I, RTA, CAH, Bartter
H/O head trauma,neurosurgery: Central D.I
H/O meningitis: Central D.I
24. Dr.Padmesh. V
WATER DEPRIVATION TEST
-Determines ability of kidneys to concentrate urine.
-Useful in the diagnosis of DI.
-Requires careful supervision because dehydration and
hypernatremia may occur.
25. Dr.Padmesh. V
WATER DEPRIVATION TEST : Method:
Begin the test after a 24-hr period of adequate hydration &
stable weight.
Obtain a baseline weight after bladder emptying.
Restrict fluids for 7 hours.
Measure body weight and urine specific gravity and volume
hourly.
Check serum Na+ and urine and serum osmolality every 2 hr.
Terminate the test if weight loss approaches 5%.
26. Dr.Padmesh. V
WATER DEPRIVATION TEST: Interpretation:
Normal individuals & Psychogenic DI: Central or Nephrogenic DI:
When water is deprived
Will concentrate urine (to 500-1400 mOsm/L) Urine osmolality remains <150-300 mOsm/L
Plasma osmolality will be 288-291 mOsm Plasma Osmolality > 300 mOsm
Urine specific gravity rises to at least 1.010 Urine Specific gravity remains <1.005
Urine volume decreases significantly No significant reduction of urine volume
There will be no appreciable weight loss. Weight loss of up to 5% usually occurs
27. Dr.Padmesh. V
VASOPRESSIN RESPONSE TEST:
To differentiate CENTRAL D.I from NEPHROGENIC D.I
Baseline Urine osmolality is recorded
Vasopressin injection given
Urine Osmolality measured at 1 hr & 4 hrs after injection
Increase in urine osmolality
>50% increase from baseline <50% increase from baseline
CENTRAL D.I NEPHROGENIC D.I
28. Dr.Padmesh. V
OTHER TESTS:
Central D.I: MRI of hypothalamic-pituitary region
Nephrogenic D.I: Renal imaging
Genetic Studies as required.