Nephritic Syndrome: Post-strep glomerulonephritis

Question 1

Definition

Answer 1

Acute glomerulonephritis most commonly occurs as a result of recent infection (post-streptococcal glomerulonephritis)- usually with streptococcus (e.g. tonsillitis), but can also sometimes be due to staphylococcus or pneumococcus.

Question 2

Which bacteria most commonly affects?

Answer 2

Group A Beta-haemolytic streptococci = specific antigen A presented on surface

Question 3

What type of reaction does it innitiate?

Answer 3

Type 3 hypersensitivity reaction

Question 4

Pathophysiology

Answer 4

Immune complexes of Ab and Ag deposit in the subepithelial layer of the glomerular basement membrane. Initiate inflammatory process which leads to deposition of C3 compliment, inflammatory cytokines, oxidants and proteases which damages the glomerulus allowing larger molecules to filter through like red blood cells and protein = dark urine
Also leads to oliguria
More fluid retained = oedema and peri-orbital oedema

Question 5

Epidemiology

Answer 5

Children

Question 6

Infection duration

Answer 6

6 weeks after skin infection = Impetigo
1-2 weeks post throat infection = pharyngitis

Question 7

Signs and symptoms

Answer 7

Signs:
- Oliguria
- Haematuria
= macroscopic: children
= microscopic: adults
- Oedema
- Cervical lymphadenopathy
- Hypertension
Symptoms:
- Pink, red or “coke” tinged urine
- Foamy urine
- 2 week post URTI infection
- Crusty yellow skin infection: impetigo as a recent trigger

Question 8

Diagnosis

Answer 8

Primary investigations:
- Urine dipstick: blood and protein would be expected
- U&Es: allows the assessment of baseline renal function, as well as monitoring for deterioration
- C3 levels: reduced levels due to consumption
- Blood tests = show antibodies against group A strep = anti-DNase B + low C3 + low CH50
- Positive streptozyme test confirms recent group A streptococcal infection = GOLD STANDARD

Consider: Renal biopsy
- Light microscopy = enlarged, hypercellular
- Electron microscopy = subepithelial deposits which appear as “humps”
- Immunofluorescence = “starry sky” granular appearance along the mesangial cells and other supporting cells

Question 9

Treatment

Answer 9

Usually self limiting
Furosemide given as initial treatment of HTN
- Loop: furosemide
Amlodipine: in case of uncontrolled hypertension, a CCB may be required