Azotemia

Excerpt

Azotemia is a biochemical abnormality, defined as an elevation or buildup of nitrogenous products (BUN, usually ranging from 7 to 21 mg/dL), creatinine in the blood, and other secondary waste products within the body. Raising the level of nitrogenous waste is attributed to the inability of the renal system to filter waste products adequately, resulting in a decreased glomerular filtration rate (GFR). It is a typical feature of both acute and chronic kidney injury.

Azotemia is crucial when discussing the precipitant syndrome of acute kidney injury (AKI), which has 3 subtypes: prerenal, intrinsic, and post-renal azotemia. There are multiple classification systems used to define AKI, including the RIFLE criteria of 2004, the AKIN criteria of 2007, and the KDIGO system of 2012. AKI is generally diagnosed by an increase in creatinine (Cr) of 0.3 mg/dL, a Cr increase greater than 1.5%, or a decrease in creatinine clearance of less than 0.5 mL/kg per hour. This diagnosis is made with urinalysis (UA), urine electrolytes, metabolic panel (CMP/BMP), and a renal ultrasound (US). With these labs, the clinician can discern the classification and etiology of the AKI, which guides clinical management. Azotemia manifests as a constellation of clinical signs and symptoms, accompanied by biochemical abnormalities, and is termed uremia.