Case 38: Diagnostic Testing

Case 38 Index

Take a look at this patient’s laboratory data.
Basic labs
Urine sediment
(Images courtesy of @JoseTesser)
Ultrasound examination
The ultrasound shows kidneys of normal size with increased echogenicity, without hydronephrosis.

Basic Lab Ref

What additional testing should come next (more than 1 may be correct)?
Kidney biopsy
Kidney biopsy would be premature in this case. Findings such as nephrotic range proteinuria or evidence of glomerulonephritis would prompt a more urgent biopsy. Try a less invasive test first!
Serum uric acid
Excellent choice! Based on the urine sediment and this patient’s disease process, this is an important test. Uric acid level is 18.9 mg/dL (normal 2.4-7.0 mg/dL)
Lactate dehydrogenase (LDH)
Great choice! This patient’s LDH is 1621 U/L (normal 140-280 U/L)
Anti-nuclear antibody (ANA)
We might send this test if we suspected a connective tissue disease (CTD), like systemic lupus erythematosus (SLE). This patient’s initial presentation does not suggest SLE or other CTD. Try again!
Urine culture
This patient’s clinical history and data thus far are not consistent with a urinary tract infection. Pick again!
Complement levels (C3, C4)
Glomerular diseases with hypocomplementemia often present with nephritic syndrome. The absence of hematuria/dysmorphic red blood cells/red blood cell casts makes nephritic syndrome less likely. Choose another test!
Serum and urine protein electrophoresis
This test would help us identify a a new monoclonal gammopathy in this patient, but may not help us with the etiology of her diagnosis here.  Try something else!
Peripheral blood smear
Great choice! No schistocytes or helmet cells are seen on the peripheral smear.

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Case 38 Index
Case 38 Introduction
Case 38 Physical Exam