Glomerular disease: nephrotic syndrome Flashcards
1
Q
Diagnostic criteria for glomerulonephritis
A
- proteinuria >3g/day
- hypoalbuminaemia <30g/dL
- oedema
- raised cholesterol
2
Q
Mechanism of proteinuria
A
- glomerular structure
- basement membrane = podocytes + collagenous membrane + endothelial cells
- disrupted in nephrotic syndrome so proteins (mostly albumin) can get through
3
Q
Assessment of proteinuria
A
- urine dipstix (all patients routine)
- get blood, protein, leukocytes, nitrites and pH from this
- simple bedside test
- protein = negative, trace, 1-4
- 24 hour urine collection is gold standard but practically not reliable
4
Q
Dipstix protein results
A
Negative trace = 15-30 mg/dL 1+ = 30-100 mg/dL 2+ = 100-300 mg/dL 3+ = 300-1000 mg/dL 4+ = >1000mg/dL
5
Q
Protein/creatinine ratio
A
- daily creatinine excretion constant = 1000mg/8.8mmol per day
- so do PCR
- normal PCR 100mg/mmol/1g/day
- nephrotic syndrome = 3g/day so 300mg/mmol
6
Q
Why do patients get oedema in nephrotic syndrome?
A
UNDERFILL HYPOTHESIS
- best understood
- decrease in intravasc colloid osmotic pressure as low serum albumin
- intravasc volume depletion
- RAAS activation = salt and water retention
OVERFILL HYPOTHESIS
- primary sodium retention
- peritubular capillaries in nephron Na-K ATPase pump active so water in from lumen
- resistance to ANP
7
Q
What are the main 2 factors in the underfill hypothesis?
A
- transcapillary hydrostatic pressure
vs. - transcapillary oncotic pressure
= movement of water from vasc space into interstitium
8
Q
What is the relevance of Starling’s law?
A
underfill hypothesis
net filtration = hydrostatic - oncotic pressure
9
Q
What is colloid oncotic pressure
A
- driven by negative proteins in intravasc and interstitial compartments
- draws fluid from interstitial space into capillaries
- transcapillary oncotic pressure = difference between intravasc and interstitial COP
- lost in nephrotic syndrome in intravasc compartment
10
Q
Clinical presentation of nephrotic syndrome
A
- oedema
- bp low/normal
- urine dip protein and maybe blood
11
Q
Investigations for nephrotic syndrome
A
- urine dipstix
- PCR
- microscopy to rule out infection
- blood invest = FBC, clotting, U&Es, LFTs
- specialist tests = hepatitis, HIV, Hep C, syphilis serology
- imaging
- US renal tract
- renal biopsy
12
Q
Cause of nephrotic syndrome
A
3 MAIN
- minimal change disease
- focal segmental glomerulosclerosis
- membranous nephropathy
- renal biopsy needed to determine cause
- other less common = diabetes nephropathy, amyloid, congenital
13
Q
Minimal change disease
A
- children common
- normal features on light microscopy
- EM = fusion of podocytes
- 90% of all NS children <10years, 50% >10 years
- absence of microscopic haematuria
- can be in adults
14
Q
Focal Segmental Glomerulosclerosis
A
Focal = not all glomeruli affected Segmental = part of glom sclerosed
15
Q
Membranous Nephropathy Who
A
- common in adults
- male
- Caucasian
