24th June 2024

Investigations in AKI

Most investigations in the first instance are routine, with knowledge of specialist tests required, in particular when intrinsic renal causes of AKI are suspected.

Blood tests

• U&Es, LFTs, CRP, FBC, Clotting Screen, Blood Culture (if Sepsis suspected). CK and bone profile. A viral screen may be required in specific cases.
• Urinalysis:
  • Marked haematuria may suggest glomerulonephritis, renal tract malignancy or bleeding disorder. Heavy proteinuria suggests glomerular disease.
  • Protein creatinine ratio and albumin creatinine ratio are useful in the presence of proteinuria.
  • Casts or dysmorphic red cells suggest glomerulonephritis.
  • Leucocytes suggest infection/interstitial nephritis.
  • Crystals may be observed in drug-induced or uric acid nephropathy.

Imaging

• A renal tract ultrasound is the first line imaging investigation. It is often used if there is no clear cause of AKI or if pyelonephritis or pyonephrosis or urinary tract obstruction is suspected

Special Tests

• Immunological tests are performed once common causes of AKI have been excluded or if there is a clinical suspicion based on history.
• Kidney Biopsy is also used for definitive diagnosis in some cases.