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

Updated: Apr 24, 2020
  • Author: Moro O Salifu, MD, MPH, FACP; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

On blood studies, findings that may suggest intrarenal azotemia include the following:

  • Anemia
  • Thrombocytopenia
  • Hypocalcemia
  • High–anion gap metabolic acidosis
  • Plasma BUN–creatinine ratio <  20

On urine studies, findings that may suggest intrarenal azotemia include the following:

  • Low specific gravity (< 1.015)
  • Active sediment (see  Pathophysiology)
  • High sodium (> 40 mEq/L; FENa > 5%)
  • Low osmolality

In patients with long-standing CKD, renal ultrasonography usually shows small, contracted kidneys. However, normal-sized or large kidneys may be seen in CKD from some causes of CKD, 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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