Renal physiology
Key points
Infant formula feeds in renal failure e.g., Renastart™ - low phosphate and aluminium +/- calcium carbonate to bind phosphate
Renal tublular acidosis
Metabolic acidosis due to impaired reuptake of HCO3 or impaired secretion of H+
Usually normal anion gap, high chloride
Caused by cystinosis, chemotherapy
Type 4 RTA - defect in reabsorption of sodium so decreased K+ and H+ secretion in distal tubule
Mimics low aldosterone - Low Na+, high K+
Happens after obstructive uropathy - resolves weeks later
Peritoneal dialysis
Automated peritoneal dialysis is used in children - personalised regimen - e.g. dialysis overnight
Continuous ambulatory peritoneal dialysis is rarely used in children
PD fluid is hypertonic dextrose - long term use results in peritoneal fibrosis
Haemodialysis
Continuous renal replacement therapy (CRRT)
3 types:
Continuous venovenous haemofiltration (CVVH) - Convective: Solute passing through membrane pores dragged by moving ultrafiltrate
Continuous venovenous haemodialysis (CVVHD) - Diffusive - Movement by concentration only
Continuous venovenous haemodiafiltration (CVVHDF) - Combined
Should not place haemodialysis line in subclavian, as risks subclavian stenosis - will not be able to form AV fistula as adult
Renovascular hypertension in children
Causes
Fibromuscular dysplasia is most common - unknown aetiology, also affects external iliacs and mesenteric vessels. 'String of pearls' appearance on angiography
Takayasu Arteritis
Kawasakis disease
Umbilical artery catheterisation
Mid-aortic syndrome (Congenital or Acquired)
Treatment
Antihypertensives
IR angioplasty
Autotransplant
Aortorenal bypass
Nephrectomy
Renal osteodystrophy
Back and hip pain
Skeletal deformities if not treated
Diffuse ground glass appearance, sclerotic areas - seen in distal clavicles, pelvic surfaces, metaphysis + diaphysis of long bones
Paediatric RIFLE criteria
Risk, Injury, Failure, Loss, End stage
RIF - based on eGFR + urine output vs time
LE - Loss for 4 weeks then 3 months
If infant has GFR of 40, then 70% chance of needing renal replacement therapy by age 20
Nutcracker syndrome
Extrinsic compression of the left renal vein
< 45 degrees between the aorta and SMA
Haematuria, left flank pain, varicocele in males, proteinuria, anaemia
Conservative treatment with elastic compression stockings is recommended first for patients with mild symptoms
ACEi have been shown to improve orthostatic proteinuria
Thin patients may benefit from weight gain
Endovascular treatment or open surgery if refractory or gross haematuria, severe pain, or renal dysfunction
Page edited by Mrs Charnjit Seehra BSc November 2024
References
Holcomb and Ashcraft’s Pediatric Surgery, 7th edition, 2020, Chapter 4
Penfold D, Lotfollahzadeh S. Nutcracker Syndrome. [Updated 2022 Dec 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing