Oliguria

As always... back to the basics:

What is oliguria?
Low urine output (UOP)

What is "normal" adult UOP?
About 30cc/hr

How might you write a post op floor order for this?
"call house officer if 2 hour UOP is < 60cc"

What are the possible causes?
Think pre renal/renal/post renal causes

What is the most common cause?
Pre renal!

Causes of Renal Failure

Causes of Renal Failure broken down by pre-renal, renal, and post-renal.

Source: Clinical Survival Guide for PA Students by G.Broughton, MD, PhD

Diabetes Insipidus, Part 2

Diagnosing DI

Polyuria = urine vol > 3L in 24 hrs - there are many causes of polyuria and it is important to figure out if the cause is DI or something else prior to establishing treatment

Urine osmolality (osm) of > 300 mOsmol/kg + high serum glucose --> think diabetes mellitus
Urine osmolality (osm) of > 300 mOsmol/kg + high serum urea --> think renal dz
Urine osmolality (osm) of < 200 mOsmol/kg + polyuria --> think DI

So you have a patient that has urine ohm < 200 + polyuria and you are thinking DI... how do you differentiate between central DI and nephrogenic DI?

Answer: water deprivation test

Findings:
Central DI
urine osm < plasma osm after dehydration
after ADH injections urine osm increases by >50%

Psychogenic DI

urine osm > plasma osm after dehydration

after ADH injections urine osm increases minimally

Nephrogenic DI

urine osm < plasma osm after dehydration

after ADH injections urine osm increases by <50%

Source: 
Makaryus/Mcfarlane. DI: diagnosis and treatement of a complex disease Cleveland Clinic Journal of Medicine Jan 2006 Vol 73:1
pic source: medicaltextboks.blogspot.com

Diabetes Insipidus, Part 1

Diabetes Insipidus, Part 1

What is it?

• The inability to conserve H20 and maintain optimum free H20 levels
• Pts urinate large amounts of diluted fluid, regardless of the body's hydration state
• Sx: extreme thirst (can even wake pts up at night and drink up to 20L per day!), dry skin, constipation

Click to enlarge

Upcoming...
Part 2: Diagnosing DI
Part 3: Treatment for Central DI and Nephrogenic DI






Source: 
Makaryus/Mcfarlane. DI: diagnosis and treatement of a complex disease Cleveland Clinic Journal of Medicine Jan 2006 Vol 73:1