Raised creatinine or low eGFR found (acute or chronic?)

• Refer to the emergency department or the nephrologist the same day; enclose previous serum creatinine results and the list of medicines.
• Rise ≥ 26.5 µmol/L in 48 h or × 1.5 in 7 days, collapsed urine output, hyperkalaemia, glomerular syndrome (haematuria, proteinuria, hypertension) or extrarenal signs.
• Urine dipstick (in the practice, as soon as AKI is suspected)

Laboratory tests

• Serum creatinine with eGFR (CKD-EPI), repeat
• Serum electrolytes (potassium)
• Urea (if acute kidney injury suspected)if neededRecent rise in creatinine compared with previous values (possible AKI): urea is part of the laboratory work-up of AKI ^[2]; its NABM coverage is limited to AKI, CKD (nutritional assessment) and dialysis ^[8].
• FBC (if acute kidney injury suspected)if needednon-French guidelineRecent rise in creatinine: the full blood count with differential is part of the AKI work-up and points to thrombotic microangiopathy or vasculitis ^[2].

Urine tests

• Urine albumin:creatinine ratio (ACR), spot sample, preferably first morning urine
• Urine dipstick (in the practice)
• Urine microscopy and culture with quantitative cytology (if dipstick positive for blood or leucocytes)if neededDipstick positive for blood or leucocytes: haematuria (> 10 RBC/mm³ after ruling out a urological cause) or leucocyturia (> 10 WBC/mm³ without infection) are markers of renal involvement ^[1].
• Take the serum creatinine sample at a distance (at least 12 hours) from a meal of cooked meat or fish and without creatine supplements.
• Renal and bladder ultrasound (obstruction, size and appearance of the kidneys).