Acute Renal Failure



Definition

  • Oliguria < 400ml / day
  • Decline in glomerular fxn, rising urea/creat

History

  • Systemic disease (DM, vascular)
  • Hx renal disease
  • Systemic upset (GI Bleed, surgery, ACS)
  • Medications (ACEI, NSAIDs, x-ray contrast, diuretics, Gentamicin, neomycin and other aminoglycosides)

Signs

  • Dehydration (dry eyes/axillae/mucous membs, postural hypotension)
  • Volume overload (JVP, BP, Creps, peripheral oedema)
  • Infection
  • Arthralgia or rash
  • Organ failure (hypoxia, hypotension, metabolic acidosis)

Causes ARF

Pre-renal

  • Cardiogenic shock (AMI, septic etc.)
  • Hypovolaemia/ dehydration
  • Sepsis
  • Contrast nephropathy (? check evidence)
  • Rhabdomyolysis
  • HUS, TTP, Hepatorenal syndrome

Renal

  • ATN (often due to local ischaemia or drugs)
  • Acute nephritis
  • Inflammatory (vasculitis)
  • Vascular (embolism or thrombus)
  • Myeloid

Post-renal (NB - 30% of ARF)

  • Obstruction (stones, malignancy)

Investigations

  • Usual bloods, CXR, ECG
  • Please remember calcium, ESR, CRP, CK
  • Full septic screen (blood cultures, urine etc)
  • NB EXCLUDE post-renal obstruction with imaging
  • Urine and serum creat, osmolality, Na+ and K+
    • Pre-renal if urine Na+ low, Cl- low, osm > 500
  • Urea:creat ratio>0.1 usually pre-renal
  • Creat clearance =(140-age) x weight/Creat (µmol) (x1.2 for men) [CrCl normal = 100ml/min]
  • Auto-antibody screen
  • Dipstick urine and microscopy for casts etc
    • UOB/protein negative dipstick = glomerular disease unlikely
    • Casts usually glomerular disease
    • Lymphocytes or eosinophils usually = interstitial nephritis

Management

  • Resuscitate with O2 and fluids
  • Relieve any obstruction
  • Stop any triggering meds
  • Call renal team
  • Consider
  • Antibiotics if septic
  • Record accurate input/output
  • Lactate / pH / bicarb in VENOUS gases

Indications for urgent dialysis

  • Metabolic acidosis - when correction with bicarb would cause fluid overload ph < 7.2
  • Electrolytes – hyperkalaemia K+ >7.0
  • Intoxication – poisoning : SLIME
  • Overload – pulmonary oedema not responding to diuretics
  • Uraemia complications eg pericarditis, encephalopathy, GI bleeding BUN 70-100 mg/dL

Dialysable drugs

S L I M E

  • Salicylate
  • Lithium
  • Ispropranolol, iron, isoniazid
  • Magnesium, methanol
  • Ethylene glycol

Renal referrals CUH

All haemodialysis/peritoneal dialysis patients – please inform renal team irrespective of pathology.

Transplant patients – on-call team (med or surg etc.) should contact renal team.

AKI other – common sense should prevail!


Content by Dr Íomhar O' Sullivan 11/10/2010. Last review Dr ÍOS 5/12/18.