Pediatric Nephrology and Urology
Nephrology and Urology items test the nephrotic versus nephritic distinction, the timing and interpretation of imaging after urinary tract infection, fluid and electrolyte emergencies, and the timing of surgery for common urological anomalies.
Nephrotic syndrome
- Triad: heavy proteinuria, hypoalbuminaemia below 2.5 g/dL and oedema, with hyperlipidaemia.
- A child aged 1-10 years with normal complement, no haematuria and no hypertension can be treated with steroids without biopsy.
- Prednisolone 60 mg/m2/day (maximum 60 mg) for four weeks, then 40 mg/m2 on alternate days for four weeks.
- Biopsy indications: age under 1 or over 10 years, macroscopic haematuria, hypertension, low C3, renal impairment, or steroid resistance.
- Complications: pneumococcal peritonitis, thrombosis, hypovolaemia. Immunise against pneumococcus.
Acute glomerulonephritis
Post-streptococcal disease follows pharyngitis by 1-2 weeks with haematuria, hypertension, oedema and low C3; management is supportive with salt and fluid restriction and antihypertensives.
Urinary tract infection
- Under 3 months: full sepsis screen, intravenous antibiotics and admission.
- Always obtain a culture before antibiotics; E. coli predominates.
- Ultrasound for all infants under 6 months and for atypical or recurrent infection; DMSA scan for scarring; voiding cystourethrography for recurrent or atypical disease and to grade vesicoureteric reflux.
Acute kidney injury and electrolytes
Stage by creatinine rise and urine output. Prerenal injury responds to volume; intrinsic injury does not. Hyperkalaemia: give calcium gluconate for cardiac protection, then salbutamol, insulin with dextrose, and consider dialysis.
Urology
- Undescended testis: orchidopexy between 6 and 18 months.
- Nocturnal enuresis: manage from 5 years with an alarm or desmopressin; never punish or restrict fluids punitively.
- Posterior urethral valves: bilateral hydronephrosis in a male infant with a poor stream; catheterise urgently.
Worked example
A 6-year-old presents with periorbital oedema, blood pressure 125/85, and urine showing 3+ blood and 3+ protein. Complement C3 is low and the creatinine is mildly raised, two weeks after a sore throat. This is post-streptococcal glomerulonephritis, not nephrotic syndrome. Treat with salt restriction, furosemide and antihypertensives; complement should normalise within 6-8 weeks, and if it does not, reconsider membranoproliferative disease.
Traps
Biopsying every nephrotic child, giving steroids in nephritis, and omitting the culture before antibiotics in urinary tract infection.