Post streptococcal glomerulonephritis

N00.9

DESCRIPTION

Acute post-streptococcal glomerulonephritis is a disorder of the kidneys caused by an immunological response of the kidney to nephritogenic strains of streptococci. It develops one to three weeks after a streptococcal throat or skin infection. Immune complexes are deposited in the glomerular basement membrane and/or mesangium of the glomeruli.

DIAGNOSTIC CRITERIA

Clinical

  • Occurs predominantly in children 3–12 years old.
  • Presents 1–3 weeks after streptococcal pharyngitis or skin infection (impetigo).
  • Characteristic features include:
    • facial or generalised oedema,
    • painless macroscopic haematuria (smoky or tea coloured urine),
    • oliguria, and
    • hypertension.

Special investigations to confirm APSGN

Urine analysis
Macroscopic appearance smokey, brown, bloody
Urine test strips 1+ to 3+ haematuria; ± trace to 2+ proteinuria
Microscopic examination dysmorphic red blood cells;
red blood cell and granular casts
Blood investigations
Streptococcus serology
ASO or Anti-DNAseB titre 		positive in the absence of prior antibiotic treatment
(ASO often negative in preceding skin infections)
Complement study
C 3
C 4

decreased
normal
S-biochemistry
Serum electrolytes dilutional hyponatraemia, hyperchloraemic hyperkalaemic metabolic acidosis is common
S-Urea & creatinine mildly elevated in the acute phase
Full blood count dilutional anaemia; thrombocyte count is normal

GENERAL AND SUPPORTIVE MEASURES

  • Bed rest is necessary in children with severe hypertension or pulmonary oedema.
  • Monitor fluid balance and prescribe fluid on a daily basis:
    • Weigh daily and record fluid intake and output strictly.
    • Allowed fluid intake should be calculated based on previous day’s urine output and insensible losses.
    • In small children, fluid balance is best monitored with regular weighing.
    • Never use a potassium-containing solution in an anuric patient.
    • Do not use parenteral fluids if oral intake is possible.
  • Ensure daily fluid calculations using insensible losses and previous day’s output. Fluid management according to fluid status:
    • Pulmonary oedema plus oliguria/anuria: Do not give fluid.
    • Hydrated anuric patient without extra-renal fluid losses: Oral fluid to replace insensible water losses only.
    • Normally hydrated plus oliguria: Oral fluid intake to replace insensible water loss and urine output of previous 24 hours.
    • Normally hydrated plus normal urine output: Give normal fluid intake.

IMPORTANT

Insensible water loss is calculated as:

  • Neonates and young babies: 30 - 40 mL/kg/day
  • Older children: 25 mL/kg/day (400mL/m²/day)

  • Dietary measures:
    • Restrict sodium intake in all patients.
    • Restrict potassium intake until result of serum electrolytes is available.
    • Restrict protein intake to 0.5 g/kg/day.

MEDICINE TREATMENT

Eradication of streptococci

  • Phenoxymethylpenicillin, oral, 50 mg/kg/24 hours in 4 divided doses (6 hourly) for 10 days.
    OR

If unable to take oral medication:

  • Benzathine benzylpenicillin (depot formulation), IM, 30 000 units/kg/dose, 2 doses given 5 days apart.
    • Maximum dose: 1.2 million units.

For severe penicillin allergy:

Hypertension

Hypertension usually develops acutely due to fluid overload and presents as hypertension emergency (crisis), hypertension urgency or persistent significant hypertension. See Chapter: Cardiovascular System, Hypertension in Children .

If Hypertensive emergency/crisis: Patient with signs of hypertensive encephalopathy, i.e. convulsions, retinal haemorrhages, visual loss and end organ disease e.g. left heart failure.

Management for acute hypertensive emergency/crisis due to post streptococcal glomerulonephritis:

  • Furosemide, IV, 1–2 mg/kg/dose.

If oliguric:

  • Furosemide, IV, 5 mg/kg/dose.
    • Administer IV bolus slowly over 5 minutes due to risk of cytotoxicity.

AND

  • Labetalol, IV, 0.2–1.0 mg/kg/dose as a bolus.
    • Maximum bolus dose: 40 mg.
    • Continue infusion: 0.25–3.0 mg/kg/hour.
    • Monitor blood pressure frequently (every 30 minutes).
    • Taper infusion rate up or down according to response.

If Hypertensive urgency : Symptomatic patients with significant elevation of blood pressure with complaints of headache, blurred vision and nausea but lacks the above clinical manifestations or persistent significant hypertension:

  • Propranolol, oral, 1-2 mg/kg/dose, 6 hourly.
    • Maximum dose: 8 mg/kg/24 hours.

If blood pressure is not adequately controlled:

ADD

  • Amlodipine, oral, 0.2 mg/kg/dose.
    • May be repeated 6 hours later, thereafter once every 24 hours.
    • Maximum dose: 5 mg.
    • Crush 5 mg tablet and disperse in 5 mL water: amlodipine 1 mg/mL.

Once blood pressure has normalised, taper and stop antihypertensive treatment. Monitor blood pressure over the next 48 hours to exclude rebound hypertension.

If Volume overloaded

See fluid management in general and supportive measures.

  • Furosemide, slow IV, 2 mg/kg/dose.
    • Maximum dose: 5 mg/kg/dose.
    • Maximum cumulative daily dose: 8 mg/kg/24 hours.

If Pulmonary oedema:

See fluid management in general and supportive measures.

  • Morphine, IV, 0.1 mg/kg/dose.
    • Repeat after 4 hours if required.
  • Oxygen, 100%, 2–3 L/minute by nasal cannula.

REFERRAL

Urgent (as soon as possible)

  • Anuric patient with acute volume overload and unresponsive to furosemide.
  • Uncontrolled hypertension.
  • Oliguric and progressive renal failure.
  • Cardiac failure or pulmonary oedema not responding to treatment.

For specialist advice

  • Macroscopic haematuria persisting for more than 4 weeks or persistent proteinuria.
  • Family history of renal disease.
  • Streptococcal aetiology unproven (ASOT and anti-DNAseB negative, normal C₃ levels, decreased C₄ levels).
  • Decreased complement levels which persist for more than 6 weeks.
  • Persistent renal failure after initial recovery.
  • Persistent hypertension.