Excellent choice! Hematuria should be differentiated as glomerular or non-glomerular if possible, by looking at the urine sediment. What do you see?

Antibodies against proteinase 3 and myeloperoxidase are not detected . Though ANCA-associated vasculitis typically presents as a rapid progressively glomerulonephritis (RPGN) and affects individuals older than 50 years old, it can occur at any age and may present with a nephritic syndrome.

The titer is 1:32.

Excellent choice. C4 is 20 mg/dL (normal: 16 – 48 mg/dL). C3 is 40 mg/dL (normal: 80 – 160 mg/dL).

Antibodies against and serum viral loads of HBV and HCV are undetectable.

This is a low yield test here. Traditionally, this test has been described for acute interstitial nephritis (AIN) – though the sensitivity and specificity for AIN is also poor.

Before moving to an invasive test like this one, we should try to find out whether the hematuria is glomerular or non-glomerular. The cystoscopy would let us look for a bladder malignancy, which might cause non-glomerular hematuria. Let’s try a higher yield test!

The CPK can be markedly elevated in patients with rhabdomyolysis, or breakdown of muscle that can subsequently lead to acute kidney injury. Classically, the urine of these patients is positive for “blood” on the urine dipstick, without the presence of red blood cells. Here, we have numerous red blood cells.

You consult your hematology colleagues and they advise against a bone marrow biopsy as there are no significant complete blood count (CBC) abnormalities. They advise other diagnostic tests to help this patient.

We might order this test in a patient with nephrotic syndrome to look for primary membranous nephroapthy. Given the findings so far, this is a low-yield test here. Try again!