Case 37: Diagnostic Testing

Case 37 Index

Take a look at this patient’s laboratory data.
Basic labs
Urine sediment
No casts or cellular elements are seen.
Ultrasound examination
The ultrasound shows kidneys of normal size with normal echogenicity and without hydronephrosis. A fetal ultrasound is normal for gestational age.

Basic Lab Ref

What is the best next step in the work-up (choose 1)?
Kidney biopsy
Kidney biopsy would be premature in this case, and is high risk in pregnancy. An active urine sediment, nephrotic range proteinuria, or rapidly deteriorating kidney function would make a stronger case to perform a biopsy for this patient. Try a less invasive test!
24-hour urine protein
Correct! This is the gold standard test for the most likely diagnosis in this pregnant patient with worsening hypertension, greater than 20 weeks gestation. A spot urine protein:creatinine ratio would be an acceptable alternative. Her 24 hour urine collection reveals 530 mg  proteinuria.
C3, C4
Complement levels may help us in the investigation of a nephritic syndrome. Despite her elevated blood pressure and abnormal kidney function, the absence of red blood cells goes against a nephritic syndrome. Try again!
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 oes not suggest SLE or other CTD. Try again!
Plasma renin activity (PRA) and aldosterone level
This patient’s hypertension has a more likely etiology given her history. PRA and aldosterone levels can be helpful in the investigation of secondary hypertension without a clear etiology. Try something else!
This patient is not thrombocytopenic. Mild anemia can be a common finding in pregnancy. Pick again!

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Case 37 Index
Case 37 Introduction
Case 37 Physical Exam