Which lab studies are performed in the evaluation of intrarenal azotemia?

Updated: Sep 19, 2018
  • Author: Moro O Salifu, MD, MPH, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Anemia, thrombocytopenia, hypocalcemia, and high–anion gap metabolic acidosis may suggest intrarenal azotemia. Low urine specific gravity (< 1.015), active urinary sediment (see Pathophysiology), high urinary sodium (>40 mEq/L; FENa >5%), a plasma BUN–creatinine ratio of less than 20, and low urine osmolality may also suggest intrarenal azotemia.

In patients with long-standing CKD, renal ultrasonography usually shows small, contracted kidneys. Some causes of CKD can be associated with normal-sized or large kidneys, such as HIV nephropathy, diabetes, and renal amyloidosis. The renal sonogram usually is diagnostic for patients with polycystic kidney disease. In patients with active urinary sediment, progressive azotemia, proteinuria, or normal-sized kidneys on ultrasonography, a renal biopsy should be considered. Consultation with a nephrologist is imperative in all such patients.


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