Increased creatinine concentration – Quick Reference

This is a Quick Reference article. See also the main article Increased blood creatinine concentration and renal function tests .

Investigations and interpretation

• Plasma creatinine concentration, estimated glomerular filtration rate (eGFR ) and urinalysis are the principal renal function tests.
• Large muscle mass may increase creatinine concentration.
• No further investigations are needed if eGFR is over 60 ml/min, unless the patient has haematuria, proteinuria or diabetes with microalbuminuria.
• GFR falls with advancing age (in an elderly person often 60–90 ml/min). In elderly patients, eGFR may be as low as 30–45 ml/min without it signifying progressive renal disease, unless there is also proteinuria, diabetes or hypertension.

Diagnostic assessment

• Underlying causative conditions?
  • Acute illness: epidemic nephropathy , vasculitis
  • Chronic disease: previous renal disease, hypertension, diabetes, atherosclerosis, prostatic hypertrophy, rheumatic disease, myeloma
  • Medicine or other toxic factor (NSAIDs, ACE inhibitors, angiotensin receptor blockers, diuretics, contrast media, substances used as alcohol substitutes; trimethoprim may increase creatinine concentration without impairing renal function)
• Physical examination
  • General condition (dehydration and fever indicate an acute illness)
  • Blood pressure (often elevated in renal disease), auscultation of the arteries
  • Palpation of the abdomen (cystic kidneys, urinary retention)
  • Rectal examination (enlarged prostate, measurement of residual urine if indicated )
  • Oedema (nephrosis, low albumin)
• Other investigations
  • Chemical urine screen; urinary sediment and culture if indicated
  • Albumin/creatinine ratio, and if this is abnormal, overnight collection for urinary albumin especially in diabetes, or 24-hour urine protein
  • Plasma potassium, calcium, phosphate and albumin (if proteinuria > 3 g/24 h)
  • Blood counts (anaemia, thrombocytopenia), CRP, ESR
  • Ultrasound of the kidneys (size, parenchyma, hydronephrosis, cystic disorder)

Indications for a referral

• Emergency referral
  • Acute renal failure or systemic symptoms in addition to high creatinine (e.g. fever, symptoms affecting upper or lower respiratory tract or joints)
  • Low urine output or anuria without a quickly rectifiable cause (obstruction, hypovolaemia)
• Non-urgent referral
  • Progressing disease discovered as an incidental finding (increasing creatinine/decreasing GFR) or if there are other signs of renal disease, e.g. proteinuria
• There is no need to refer a patient with several comorbidities if renal disease plays no particular part in prognosis.