Acute Renal Failure
- 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)
Causes ARF
Pre-renal
- Cardiogenic shock (AMI, septic etc.)
- Hypovolaemia/ dehydration
- Sepsis
- Contrast nephropathy
- Rhambomyolysis
- 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)
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)
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 (umol) (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
