genitourinary disorders
Chronic Kidney Disease
Diagnosis of Chronic Kidney Disease
Electrolytes, bloodureanitrogen (BUN), creatinine, phosphate, calcium, complete blood count (CBC) Urinalysis (including urinary sediment examination) Quantitative urine protein (24-hour urine protein collection or spot urine protein to creatinine ratio) Ultrasonography Sometimes renal biopsy Chronic kidney disease (CKD) is usually first suspected when serum creatinine rises. The initial step is to determine whether the renal failure is acute, chronic, or acute superimposed on chronic (ie, an acute disease that further compromises renal function in a patient with CKD—see table). The cause of renal failure is also determined. Sometimes determining the duration of renal failure helps determine the cause; sometimes it is easier to determine the cause than the duration, and determining the cause helps determine the duration. nitrogen, creatinine, phosphate, calcium, and CBC. Sometimes specific serologic tests are needed to determine the cause. Distinguishing Acute Kidney Injury (AKI) from An ultrasound examination of the kidneys is usually helpful in evaluating for Obstructive Uropathy and in distinguishing acute kidney injury from CKD based on kidney size. Except in certain conditions (see table Staging CKD is a way of quantifying its severity. CKD has been classified into 5 stages. Stage 1: Normal GFR (≥90 mL/min/1.73 m2) plus either persistent albuminuria or known structural or hereditary renal disease Stage 2: GFR 60 to 89 mL/min/1.73 m2 Stage 3a: 45 to 59 mL/min/1.73 m2 Stage 3b: 30 to 44 mL/min/1.73 m2 Stage 4: GFR 15 to 29 mL/min/1.73 m2 Stage 5: GFR<15 mL/min/1.73 m2 GFR (in mL/min/1.73 m2) in CKD can be estimated by the Chronic Kidney Disease Epidemiology Collaboration(CKD-EPI 2021) creatinine equation: , where Scr = standardized serum creatinine in mg/dL κ = 0.7 (females) or 0.9 (males) α = -0.241 (female) or -0.302 (male) min(Scr/κ, 1) = minimum of Scr/κ or 1.0 max(Scr/κ, 1) = maximum of Scr/κ or 1.0 Age (years) In contrast to prior versions, the most recent equation does not adjust for race, so as to reduce racial inequities in CKD diagnosis and thus treatment. Alternatively, GFR can be estimated using timed (most commonly 24-hour) urine creatinine clearance that includes measured serum and urine creatinine; this equation tends to overestimate GFR by 10 to 20%. It is used when serum creatinine assessment may not be as accurate (eg, in patients who are sedentary, very obese, or very thin). Serum cystatin C is an alternative endogenous GFR marker used as a confirmatory test in people with nonrenal factors affecting serum creatinine level (eg, extremely high or low muscle mass, exogenous creatine intake, amputations or neuromuscular diseases, and high protein or exclusively plant-based diets). GFR is calculated usingCKD-EPI cystatin C equation. TheCKD-EPI 2021 formulais more accurate than the Modification of Diet in Renal Disease (MDRD) and Cockcroft-Gault formulas, particularly for patients with a GFR near normal values. The CKD-EPI equation yields fewer falsely positive results indicating chronic kidney disease and predicts outcome better than the other formulas. 