Acute
interstitial nephritis (AIN) is the cause of over 15% cases of acute loss of
kidney function Unlike many other causes of acute loss of kidney function, AIN
is treatable with steroids if culprit is stopped in many occasions. Diagnosis
of AIN is often difficult and there have been various markers in the history of
AIN
Currently,
AIN commonly occurs because of various non–β-lactam antibiotics, proton
pump inhibitors, nonsteroidal antiinflammatory drugs, and cancer
immunotherapy agents.
The
classically used urine eosinophils was thrown
under the bus few years ago. Yet, many still order that test that is
very non specific and not sensitive for AIN.
Imaging
studies such as MAG-3 scans are rarely used and not as sensitive or specific
for AIN. A kidney biopsy is often needed before giving steroids. Often this is
not possible due to active infection, recent infection, anticoagulation.
A
recent study published in JCI shows some novel urinary markers that
might be used to diagnosis AIN. In a single center, 15% of patients had AIN. Participants with AIN had consistently
higher levels of urine TNF-α and IL-9 than those with other diagnoses,
including acute tubular injury, glomerular diseases, and diabetic kidney
disease, and those without any kidney disease. The higher the TNF and IL-9, the
higher the index of renal biopsy injury. The kidney biopsies with AIN also
stained highly with TNF and IL-9. In
addition, the clinicians diagnosis index improved significantly with addition
of these urinary markers.
AIN is a tough
diagnosis to make. This study adds value in perhaps using other biomarkers that
show signs of T cell activation. Is this specific for renal disease is a trend
to watch? To me, there are no clinical signs that are real obvious clues. Urine
eos- most useless, MAG-3 scans,- not useful. Serum eos trends- maybe useful.
Urine WBCS casts and WBCS- not specific. The current
study adds to the most specific findings thus far for an AIN diagnosis
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