Acute renal failure
Clinical approach to a child with renal failure
ARF_approach_in_children.jpg

Suspect azotemia if
  • Oliguria (urine output <0.5ml/kg/h)
    • Acute non-oliguric renal failure
    • GFR: 5-15 ml/min/1.73m2
  • Anuria
  • Acidosis (Kussmaul’s breathing)
  • Haematuria, proteinuria or other urinary abnormalities
  • Hypertension
  • S/s of obstructive uropathy
  • S/s of renal tubular dysfunction
    • Polyuria, polydipsia, enuresis (beyond 6 yrs of age), rickets, growth retardation
  • Anemia of unknown etiology
Features to suggest chronicity
  • History
    • Family history of hereditary nephritides
    • History of polyuria, polydipsia, enuresis beyond 6 years
    • Past history of significant renal disease
  • Physical exam
    • Short stature
    • Sallow appearance
    • Anemia
    • Chronic hypertensive retinopathy
    • Dystrophic fingernails
    • Pinguenculae
    • Neuropathy
  • Investigations
    • Renal osteodystrophy/rickets
    • Small shrunken kidneys
Causes of acute renal failure
Pre-renal
Renal
Post-renal
· Heart failure (severe)
· Volume contraction
- GI losses
- Renal losses
- Sweat
· 3rd space losses
- Hypoalbuminemia
- Peritonitis
- Crush injury
- Burns
- Sepsis
· GN
- Acute GN
- Post-infectious GN
- Lupus nephritis
- HSP nephritis
- IgA nephropathy
- RP GN
· Vascular
- HUS
- Renal vein thrombosis
· Interstitial nephritis
- Allergic
- Post-infectious
- Fulminating PN
- Papillary necrosis
· Acute tubular necrosis
- Prerenal (vasomotor)
- Nephrotoxins
- Pigment injury
· Obstructive uropathy
- PUV
- Neurogenic bladder
- Ureteric obst of single kidney
· Crystalluria
- Uric acid:
- Tumor-lysis
- Post-cardiac op for cyanotic CHD
- Dehydration
- Hyperuricemia
- High dose MTX
- Calcium oxalate
- Hyperoxaluria
- Glycol toxicity
Urinary sediment in renal failure
Finding
Cause
Isomorphic red cells
Renal vein thrombosis
Distorted red cells and red cell casts
HUS
GN
White cells
Pyelonephritis
Eosinophils
Acute interstitial nephritis
Renal tubular epithelial cells, tubular cell casts and coarse granular casts
Acute tubular necrosis
Crystals- urate, calcium oxalate
Crystalluria
Scant findings
Pre- or post-renal
Urinary diagnostic indices
Indices
Pre-renal ARF
Ischaemic Intrinsic ARF
Urine osmolality, Uosm
> 500
< 350
Urinary Na+, UNa
< 20
> 40
Fractional excretion of Na+, FeNa
< 1
> 1
Renal failure index, RFI
< 1
> 1
FeNa= U/PNa ÷ U/PCr x 100%
RFI = UNa ÷ U/PCr
Therapeutic trial of volume expansion
ARF_fluid_challenge_in_children.jpg

Problems in management of acute renal failure
Problems
Management
Fluid overload
· Fluid restriction
- 1st 10kg – 100 cal/kg
- Next 10kg – 50 cal/kg
- Next 10kg – 20 cal/kg
- INS H2O loss – 45ml/100cal
- HID H2O metab – 15ml/100cal
- Fluiq req = INS H2O loss – HID
H2O metab + U.O. + other loss
Aim at wt loss 0.5-1.0% daily
­ Nitrogenous waste (Hypercatabolism)
· Adequate caloric intake
· Protein intake 2g/kg/day
(8% of total calories)
· Essential L-amino acids
Hyponatremia
· Dilutional: restrict fluids
· True loss: replacement saline
Hyperkalemia
· IV 10% Ca2+ gluconate 0.5ml/kg
· Salbutamol IV 4mg/kg or nebulized 2.5mg(BW≤25kg)
· IV NaHCO3 3mmol/kg (?)
· IV 50% glucose 0.5g/kg + Insulin IU/5g glucose
· Resin exchange
· Dialysis
Hypocalcemia
· Ca2+ supp 0.5-1.0 mmol/kg/day
Hypertension
· Diuretics – frusemide
· Anti-hypertensives
Convulsions/Coma
- Hypocalcemia
- Hypomagnesemia
- Hypertension
- Uremia
- ICH
- Dialysis
- Dysequilibrium syndrome
· Anti-convulsants
· Correct metabolic abnormalities
· Dialysis
Cardiac failure
· Dialysis
Pericarditis
· Dialysis
Anemia
· Exchange transfusion in neonates
· Dialysis and trransfusion
Infection
· Antibiotics (dose adjustment necessary for nephrotoxic agents
Indications for dialysis
  • Hyperkalaemia K+>7mmol/L unresponsive to conventional treatment
  • Uncontrolled acidosis HCO3- <10mmol/L
  • Severe fluid overload with uncontrollable hypertension, pulmonary edema or cardiac failure
  • Progressive uremia with deterioration of general condition
  • Hypercatabolic states with increase in blood urea by > 10mml/day

Problems of fluid restriction
  • Insufficient calories and protein malnutrition
  • No space for blood products
  • Difficulty in drug delivery
Propensity for hypoglycaemia