23. Polyuria

Question 1

What are Dx of polyuria?

Answer 1

• Diabetes Mellitus • Diuretics (e.g. diuretic medication, caffeine, alcohol, lithium)• Heart Failure • Hypercalcaemia • Hyperthyroidism• Primary Polydipsia• Hypokalaemia • Diabetes Insipidus

Question 2

What questions will help you narrow down the cause of polyuria?

Answer 2

What is the temporal pattern of urine output?Any fatigure, weight loss, recurrent infections? suggests diabetesAny LUTS? frequency, urgency, hesitance, terminal dribbling, incomplete voidingAny pain, change in urine frequency, colour, smell? UTI

Question 3

What will you ask about on PMHx of polyuria?

Answer 3

History of renal problems or triggers of renal problems? vasculitides, urinary retention, hypertensionOlder patients: ask about cancer and known bony involvementAny psychiatric disorders

Question 4

Drug history in polyuria

Answer 4

Diuretics, lithium (causes nephrogenic DI)

Question 5

Family history in polyuria

Answer 5

Diabetes, any cancers

Question 6

What are simple tests in someone with polyuria?

Answer 6

Capillary blood glucose and urinalysis

Question 7

What are further Ix for polyuria?

Answer 7

Fasting glucose, urine osmolality, electrolytes (primary polydypsia will have hypOnatremia), urea, creatinine, EGFR, calcium and TFTs

Question 8

What are 2 types of diabetes insipidus and how do you differentiate between them?

Answer 8

Cranial and NephorgenicWater deprivation test to differentiate between the 2 and give desmopressin.After DDAVP- normal urine osmolality- cranial and low urine osmolality- nephrogenic

Question 9

What are causes of cranial and nephorgenic DI?

Answer 9

Cranial- pituitary tumours, cranipharyngiomas, trauma, mets, vascular lesions, meningitisNephrogenic- pyelonephritis, hypokalemia, hypercalcemia, lithium drugs, hydronephrosis, inherited

Question 10

What is management of cranial DI?

Answer 10

Adequate fluid intake, investigate cause, give ADH replacement