2nd order laboratory parameters – depending on the results of the history, physical examination and obligatory laboratory parameters – for differential diagnostic clarification.
- Small blood count [thrombocytopenia (deficiency of platelets/platelets): due tothrombotic microangiopathy]
- Differential blood count
- Inflammatory parameters – CRP (C-reactive protein) or ESR (erythrocyte sedimentation rate).
- Urine status (rapid test for: pH, leukocytes, nitrite, protein, glucose, ketone, urobilinogen, bilirubin, blood), sediment, urine culture (pathogen detection and resistogram, that is, testing suitable antibiotics for sensitivity / resistance).
- [Prerenal renal failure: inconspicuous urine sediment.
- Differentiation of glomerular from non-glomerular hematuria.
- Renal failure: brown granulated cylinders (dead tubule cells)]
- Electrolytes – calcium, sodium, potassium ↑, magnesium ↑, phosphate ↑.
- Serum bicarbonate
- Determination of fractional or fractional sodium excretion (FENa; sodium excretion in relation to GFR (glomerular filtration rate)):
- > 1 (i.e., sodium reabsorption impaired by tubule damage): renal failure.
- < 1 (i.e., total filtered sodium reabsorbed): prerenal renal failure.
- Blood gas analysis (BGA)
- Liver parameters – alanine aminotransferase (ALT, GPT), aspartate aminotransferase (AST, GOT), glutamate dehydrogenase (GLDH) and gamma-glutamyl transferase (gamma-GT, GGT), alkaline phosphatase, bilirubin.
- Renal parameters – urea, creatinine, cystatin C or creatinine clearance, if necessary.
- Coagulation parameters – PTT, Quick
- Uric acid
- Creatine kinase (CK) – if rhabdomyolysis (dissolution of striated muscle fibers as a complication of various diseases/conditions) is suspected (e.g., statins).
- Oxalate crystals in the urine – if oxalosis is suspected (e.g., in short bowel syndrome).
- Protein electrophoresis in urine
- Total protein in blood serum
- Renal biomarkers that can indicate acute kidney injury (AKI) even before renal function is limited (measurement of renal stress) [not a routine diagnostic test]:
- Neutrophil gelatinase-associated lipocalin (NGAL) – is expressed more abundantly in the early stages of AKI (ischemic or toxic cause) and is secreted by the damaged distal tubule epithelial cells
- Other renal biomarkers include: “tissue inhibitor of metalloproteinases-2”, “insulin-like growth factor-binding protein 7″, tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor-binding protein 7 (IGFBP7).
- Renal biopsy (tissue sampling from the kidney; in individual cases – e.g. glomerulonephritis of different genesis – for further diagnosis).
Note
- The concentration of serum creatinine is not very sensitive. Only when the glomerular filtration rate (≈ functional capacity of the kidney) is reduced by more than 50% are increases apparent.
- Cystatin C is more appropriate as a renal function marker. It shows greater sensitivity (percentage of diseased patients in whom the disease is detected by use of the test, i.e., a positive test result occurs) and specificity (likelihood that actually healthy individuals who do not have the disease in question are also detected as healthy in the test) than serum creatinine in the range between 80-40 ml/min (GFR).
