Week 2 Renal Investigations Flashcards
What are the 7 main functions of the kidneys?
- Filter blood
- Remove waste and excess fluid
- Retain proteins
- Regulate blood pressure
- Produce erythropoietin (EPO)
- Activate vitamin D
- Eegulate acid-base balance.
Which of these function is significant re. proteinuria?
- Filter blood
- Remove waste and excess fluid
- Retain proteins
- Regulate blood pressure
- Produce erythropoietin (EPO)
- Activate vitamin D
- Eegulate acid-base balance.
Retain proteins
Proteins in the urine is therefore a sign of kidney disease
What does proteinuria tell you that blood in the urine doesn’t?
Blood could come from anywhere, could be urethra, bladder, ureta, anywhere in the kidney.
Whereas protein can only really be present if there is a problem with the kidney
What is proteinuria?
Presence of excess protein in the urine; a cardinal sign of kidney disease.
What is the correct medical term: proteinuria or proteinurea?
Proteinuria.
When should proteinuria be tested for?
Routine medical checks, hypertension, diabetes, oedema, possible systemic disease.
Does urinary tract infection commonly cause proteinuria?
No. Sending an MSU (midstream urine sample) to exclude infection is not the correct response to finding proteinuria.
Low proteinuria could be a UTI however other investigations should be done as well.
What is the significance of both protein and blood in urine?
Suggests glomerular disease; urgent investigation needed.
What ACR ranges indicate normal, micro-, and macroalbuminuria?
- Normal: < 3.5 mg/mmol
- Microalbuminuria: 3.5–30 mg/mmol
- Macroalbuminuria: > 30 mg/mmol
What are the 4 methods to measure kidney function?
- Serum creatinine
- Estimated GFR (eGFR)
- Creatinine clearance
- Isotope GFR (e.g., 51Cr-EDTA).
Most common cause of kidney failure in the western world?
Diabetes
Why do you have to you have to take in muscle levels when measureing plasma creatinine?
Creatinine levels are dependant on muscle mass
Name the 3-layered filtration barrier in the glomerulus.
Podocytes, glomerular basement membrane, and glomerular endothelium.
What causes congenital nephrotic syndrome?
Mutations in podocyte-specific genes like nephrin.
What happens to the number of nephrons with age?
Number of functioning nephrons
decreases with age
What are the features of nephrotic syndrome?
Heavy proteinuria, oedema, hypoalbuminaemia, hyperlipidaemia, thrombosis risk, infections.
Why is albuminuria clinically significant?
It’s a modifiable, independent risk factor for cardiovascular disease in both diabetic and non-diabetic populations.
How much albumin does normal urine contain?
Normal urine contains tiny amounts of albumin
What is creatinine used for?
To estimate GFR
How would we calculate a perfect GFR?
How would we calculate GFR in reality?
Getting an average of urine concentration and output would require constant collecting throughout the day which is impractical for the large numbers of people in hospital who aren’t in for very long.
Instead we estimate form plasma creatinine alone using various equations that take into account other factors affecting creatinine such as muscle mass
How do you use eGFR to diagnose chronic kidney disease?
“Diagnosis” of CKD usually requires eGFR consistently to be < 60 mL/min/1.73 m2
- But can involve eGFR >60 if any of:
- persistent proteinuria / microalbuminuria
- haematuria
- renal anatomical/genetic abnormality
For AKI why is eGFR not that useful?
What would you use?
eGFR is not useful for AKI because it is not accurate for rapidly changing kidney function
Need to use a combo of:
* ⇑plasma creatinine of:
≥26 µmol/L within 48 hr
≥50% in the last 7 days
* UO < 0.5 mL/kg/hr for >6 hr in adults
To diagnose AKI you need the following:
- ⇑plasma creatinine of:
≥26 µmol/L within 48 hr
≥50% in the last 7 days - UO < 0.5 mL/kg/hr for >6 hr in adults
Why is this an issue?
What do we do?
It takes a bit of time or knowledge of baseline creatinine. As a result lots of early AKI is missed.
Can use an algorythm to estimate baseline creatinine and rise in creatinine
