Chronic renal failure laboratory tests
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Chronic kidney disease is defined as the presence of markers of kidney damage for > 3 months, and may include abnormalities in markers in blood or urine, and imaging test and/or GFR < 60 mL/min/1.73 m2 for > 3 months with or without other signs of kidney damage. The kidneys play an important role in the regulation of serum concentration of electrolytes such as sodium, potassium, calcium, phosphate, bicarbonate and chloride as well as levels of hemoglobin, hematocrit, blood pressure and extracellular volume. Hence, chronic injury to the kidneys can lead to derangement in the normal values of above mentioned parameters.
- Urine sodium excretion (Fractional excretion of sodium):
- Red cell or white cell casts and crystals
- Urine creatinine levels
Fluid and Electrolyte disturbances
- Metabolic acidosis
- Most often is mild, pH is rarely below 7.35
Endocrine and Metabolic disturbances
- Decreased HDL levels
- Vitamin D deficiency
- Increased Parathyroid hormone levels
Measurement of Renal Function
Chronic Kidney Disease is defined as:
- Presence of markers of kidney damage for > 3 months, and may include abnormalities in markers in blood or urine, and imaging tests.
- GFR < 60 mL/min/1.73 m2 for > 3 months with or without other signs of kidney damage.
Glomerular filtration rates
The stages of CKD is based on the GFR and other renal function abnormalities. The different stages of chronic kidney diseases are as follow:
- Stage 1: GFR>90 ml/min/1.73m2 and evidence of kidney damage
- Stage 2: GFR 60-89 ml/min/1.73m2 and evidence of kidney damage
- Stage 3: GFR 30-59 ml/min/1.73m2
- Stage 4: GFR 15-29 ml/min/1.73m2
- Stage 5: GFR <15 ml/min/1.73m2
Using serum creatinine alone as an indicator of kidney function may be misleading. This is because the calculated creatinine levels depends on age, gender, race, nutritional status and muscle mass. At GFR levels ≥60 ml/min/1.73 m2, neither the Cockroft and Gault equation nor the MDRD equation provides a reliable measurement of kidney function. The CKD-EPI equation is more accurate than the Cockcroft and Gault equation and the MDRD equation at GFR levels ≥60 ml/min/1.73 m2.
- Serum creatinine (Cr)
- Determined by glomerular filtration rate (GFR) and by generation, tubular secretion and extrarenal clearance of creatinine
- May be an inaccurate estimate of renal function, particularly in patients with mild renal insufficiency
- Drugs may inhibit tubular secretion of creatinine and falsely report elevated serum creatinine (cimetidine, trimethoprim)
- Creatinine clearance
- Estimate: [(140-age) x body wt (kg)] / [Plasma creatinine x 72] (multiply result x 0.85 for women)
- Calculated based on 24-hour urine collection
- If GFR < 50, Creatinine clearance overestimates GFR
Determination of Chronicity
- Prior creatinine measurements if available
- Acute Renal Failure (ARF) is associated with:
- Chronic renal failure is associated with:
- Schaeffner ES, Ebert N, Delanaye P, Frei U, Gaedeke J, Jakob O; et al. (2012). "Two novel equations to estimate kidney function in persons aged 70 years or older". Ann Intern Med. 157 (7): 471–81. doi:10.7326/0003-4819-157-7-201210020-00003. PMID 23027318.
- Nickolas TL, O'Rourke MJ, Yang J, Sise ME, Canetta PA, Barasch N; et al. (2008). "Sensitivity and specificity of a single emergency department measurement of urinary neutrophil gelatinase-associated lipocalin for diagnosing acute kidney injury". Ann Intern Med. 148 (11): 810–9. PMC 2909852. PMID 18519927. Review in: ACP J Club. 2008 Dec 16;149(6):13 Review in: Evid Based Med. 2009 Feb;14(1):20