Polyuria Flashcards
What is important thing in history to ascertain for polyuria
If actually polyuria or increased frequency. Ask about whether high volume or if the urine is often clear
What is test to determine if actually polyuria
24hr urine collection. Polyuria if over 3L
DDx for polyuria
DM Diuretics HF Hypercalcaemia Hyperthyroidism Primary polydipsia Hypokalaemia Diabetes insipidus
How does cushings and steroids lead to polyuria
Cause DM
How does hypercalcaemia cause polyuria
Nephrogenic diabetes insipidus
How can chronic renal failure cause polyuria
Nephrogenic diabetes insipidus
How does hypokalaemia cause polyuria
Nephrogenic diabetes insipidus
Why do you wee less at night
As the intake of luid is zero the body retains all the fluid making the urine very concentrated
Why is nocturia relevant in polyuria
Shows the kidneys inability to concentrate the urine thus excluding primary polydipsia
Why are LUTS symptoms relevant in polyuria
Probably not truly polyuria but increased frequency instead
Why is change in urine colour and smell relevant in polyuria
Is as a result of UTI instead most likely
How is PMH relevant in polyuria history
Look for things that could cause renal problems- vasculitides, HTN, chronic urinary retention
Cancer could lead to hypercalcaemia
Relevance of drugs in polyuria history
Diuretics
Lithium leading to nephrogenic polyuria
Fatigue and weight loss relevance in polyuria history
Diabetes Mellitus
Investigations ordered for polyuria
Capillary glucose- diabetes Urinalysis- exclude UTI Urine osmolality U&Es Calcium Thyroid function
What are 2 mechanisms that cause polyuria
Inability to reabsorb solutes so they remain in urine and water follows
Inability to reabsorb water either DCT pathology or ADH system impairment
What is difference in urine osmolality between 2 mechanisms causing polyuria
Inability to reabsorb solutes- 300mosm
ADH deficiency- under 250mosm
What will be main electrolyte abnormality in primary polydipsia
Hyponatraemia
How to differentiate primary polydipsia from all other polyuria causes
In primary polydipsia will be hyponatraemia but in others hypernatraemia
Cranial causes of DI
Surgery Vacular lesion Mets Pituitary tumours Craniopharyngioma
Investigation order for polyuria leading to diagnosis
Check glucose
If normal check urine osmolality
If high then due to kidney inability to reabsorb solutes due to drugs etc
Then check serum sodium- if low psychogenic polydipsia
Then water deprivation test with desmopressin
Recurrent infections to genitals in polyuria history
DM
What ABs are found early on in T1DM patients
Anti glutamic decarboxylase
Causes of DKA
First time diagnosis with T1DM
Ilness
Poor compliance with insulin
