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acute kidney injury

@ severe end of spectrum is acute renal failure
1. sudden, potentially reversible, reduction in renal function
oliguria (0.5 ml/kg per hour) usually present
classification
1. prerenal
  1. commonest cause in kids
  2. hypovolaemia
    1. gastroenteritis
    2. burns
    3. sepsis
    4. haemorrhage
    5. nephrotic syn
  3. circulatory failure
2. renal
  1. salt & water restriction; blood, protein & casts present in urine & perhaps sx specific to accompnying disease
  2. vascular
    1. haemolytic uraemic syn (HUS)
      1. triad
        acute renal failure
        microangiopathic haemolytic
        thrombocytopenia
      2. typically 2ndary to GI infection
        E. coli O157:H7
        makes verocytotoxin
        acquired by
        eating uncooked beef
        contact w/ farm animal
        commonly
        Shigella
      3. follow prodrome of bloody diarrhoea
      4. toxin from pathogen enter GI mucosa
        then localises to renal endothelial cells & cause intravasc thrombogenesis
        coagulation cascade activated & clotting normal
        platelets consumed
        microangiopathic haemolytic anaemia results
        due to damage to RBC as they go through microcirculation
      5. brain, heart, pancreas may also be involved
      6. atypical HUS
        no diarrhoeal prodrome
        may be familial
        often relapses
        high risk of HTN & chronic renal failure
        high mortality
      7. Mx
        typical HUS (diarrhoea-assoc)
        supportive therapy
        dialysis
        follow up
        may be persistent proteinuria
        development of HTN
        atypical HUS or cerebral involvement
        plasma exchange/infusions
        unproven efficacy
    2. vasculitis
    3. embolus
    4. renal vein thrombosis
  3. tubular
    1. acute tubular necrosis (ATN)
    2. ischaemic
    3. obstructive
  4. glomerular
    1. glomerulonephritis
  5. interstitial
    1. interstitial nephritis
    2. pyelonephritis
3. postrenal
  1. from urinary obstruction
    1. congenital e.g post urethral valves
    2. acquired e.g. blocked urinary catheter
acute renal failure suggested by
1. growth failure
2. anaemia
3. renal osteodystrophy
  1. disordered bone mineralisation
Mx
1. meticulous monitoring
  1. circulation
  2. fluid balance
2. Ix
  1. US
    1. to ID obstruction of urinary tract
    2. small kidneys of chronic renal failure
    3. large bright kidneys w/ loss of cortical medullary differentiation
      1. typical of acute process
3. prerenal ARF
  1. suggested by hypovolaemia
    1. fractional excretion of Na+ very low as body tries to retain fluid
    2. hypovol needs urgent correction to avoid acute renal tubular necrosis
      1. fluid replacement
      2. circulatory support
4. renal ARF
  1. if circulatory overload present to correct Na+ & water balance, gradually
    1. restrict fluid intake
    2. diuretic
  2. high calorie, normal protein feed
    1. decreases catabolism, uraemia & hyperkalaemia
  3. emergency mx of metabolic abnormalities
    1. metabolic acidosis
      1. sodium bicarbonate
    2. hyperphosphataemia
      1. calcium carbonate
      2. dietary restriction
    3. hyperkalaemia
      1. calcium gluconate if ECG changes
      2. calcium exchange resin
      3. glucose & insulin
      4. dietary restriction
      5. dialysis
  4. if cause of renal failure not obv
    1. renal biopsy
      1. to ID rapidly progressive glomerulonephritis
        may need immediate immunosuppresion
  5. commonest causes of ARN in kids in UK
    1. haemolytic uraemic syn
    2. acute tubular necrosis
      1. multisys failure in ICU
      2. ff cardiac surgery
5. postrenal ARF
  1. needs assessment of site of obstruction
  2. relief of obstruction
    1. nephrostomy
    2. bladder catheterisation
  3. surgery can be done once fluid vol & electrolyte abnormalities corrected
6. dialysis
  1. indications
    1. failure of conservative mx
    2. hyperkalaemia
    3. severe hypo or hypernatraemia
    4. pul oedema or HTN
    5. severe acidosis
    6. multisys failure
  2. peritoneal
  3. haemodialysis
    1. used if plasma exchange part of Rx
    2. continuous arteriovenous or venovenous
      1. if cardiac decompenation or hypercatabolism
generally good prognosis for renal recover unless complicating a life-threatening condition

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acute kidney injury

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	Created by v.djabatey about 10 years ago