Case 28: Diagnostic Testing

Case 28 Index

Take a look at some initial diagnostic testing below.
Urinalysis/microscopy, urine electrolytes
Urine sediment
Basic labs
Kidney Ultrasound

The right kidney measures 14cm in length (seen here), and the left kidney measures 15cm in length. Both are echogenic.

Basic Lab Ref

What are the highest yield tests to send next (several may be correct)?
ANCA panel
This test would be more useful in the work-up of a glomerulonephritis. Try again!
Viral serologies
Absolutely! Hepatitis C, Hepatitis B, and HIV are all negative in this case.
While these may be useful to work-up or monitor this patient’s Crohn’s disease, they will not be highest yield in sorting out his kidney problem. Try again!
Serum protein electrophoresis (SPEP) and free light chains
Definitely! SPEP shows a polyclonal gammopathy with IgG 1700, IgA 600, IgM 15. The kappa to lambda (free light chains) ratio is within normal limits.
Antinuclear Antibody (ANA)
Good choice! This patient’s ANA is 1:80 (normal <1:80). For good measure you also send an anti-dsDNA, which is negative.
Hemoglobin A1c
You should absolutely check for diabetes in a patient with proteinuria and enlarged kidneys. His A1c is 5.9% consistent with pre-diabetes.
Anti-PLA2R Antibody
It is not unreasonable to send this test in a patient with nephrotic range proteinuria. Unfortunately the lab tells you this will take at least 1 week to come back.

While this testing has proven helpful, we do not yet have a diagnosis for this patient’s kidney dysfunction. Click here to perform the kidney biopsy!

Case 28 Index
Case 28 Introduction
Case 28 Physical Exam