Approach to PUPD

Question 1

What is the S.G of urine in different bits of the renal tubule?

Answer 1

PCT - 1.010
Loof of Henle - 1.060
DCT - 1.001
Collecting duct - 1.001 - 1.060

Question 2

Below what level is very little ADH secreted?

Answer 2

Serum osmolality of <280

Question 3

What stimulates ADH release?

Answer 3

baroreceptors and osmoreceptors both lead to thirst and ADH release (baroreceptors angiotensin)

Question 4

What USG supports PUPD

Answer 4

If consistently below 1.020

Question 5

What are the Ddx for PUPD

Answer 5

DM
DI
HAC/ high T4/ Addisons/ Acromegaly/ hyperaldosteronism
Liver failure
Fanconi syndrome
V low protein diet/ High salt diet
Low K, high Ca
Pyo/ septicaemia
CKD/ AKI/ pyelonephritis
Primary glucosuria
Post obstructive diuresis
Glucocorticoids/ diuretics/ levothyroxine/ phenobarb/ vitamin D
Primary PD
Medullary washout

Question 6

how does a pyo cause PUDP

Answer 6

Tocins compete with binding sites at renal tubular cells (oft e.coli)

Question 7

How does high Ca cause PUPD

Answer 7

Inhibits binding of ADH/ damages receptors/ downregulates aquaporin 2

Question 8

How do
liver failure
HAC
low K
Addisons
high T4
Acromegaly
Cause PUPD

Answer 8

liver failure - low urea
HAC - decrease release and action of ADH/ primary pd
low K - down regulates AP 2
Addisons - Na wasting
high T4 - ? increased blood to kidneys
Acromegaly - DM or glomerulopathy

Question 9

What Dx cause osmotic diuresis

Answer 9

DM
Fanconi syndrome
Primary glucosuria
Renal failure
Post obstructive diuresis

Question 10

What are the main types of PUPD

Answer 10

Primary PD
Osmotic
Central Nephrgenic
Iatrogenic

Question 11

What does an S.G of <1.006 mean?

Answer 11

Rules out CKD

More likely DI, PP, HAC