Acute interstitial nephritis (AIN) is caused by acute inflammation of the renal tubulo-interstitium, commonly mediated by a hypersensitivity reaction to medications. Autoimmune diseases and infections are less common causes.
Usually drug-induced with >250 known triggering medications. Common classes include beta-lactam and fluoroquinolone antibiotics, proton-pump inhibitors, nonsteroidal anti-inflammatory drugs (NSAIDs), and immune checkpoint inhibitors. Also occurs in inflammatory diseases such as sarcoidosis, Sjogren syndrome, IgG4-related diseases, and tubulointerstitial nephritis with uveitis (TINU) syndrome. Various infectious agents (viruses, bacteria, fungi) and some malignancies can also cause AIN.
Presents with acute kidney injury or subacute loss of kidney function. The "hypersensitivity triad" of rash, fever, and eosinophilia occurs rarely (<10%). Nephrotic syndrome may be present in cases triggered by NSAIDs.
Clinical diagnosis relies on maintaining a high index of clinical suspicion for this disease and performing a kidney biopsy to obtain tissue for histologic diagnosis. Histologic features of interstitial immune infiltrate, eosinophils, and tubulitis are considered characteristic of this disease.
May resolve once the triggering medication is discontinued. Corticosteroid therapy may be associated with greater recovery of kidney function.
Most patients have some residual renal impairment after an episode of acute interstitial nephritis.
History and exam
Key diagnostic factors
- use of triggering medication
- loss of kidney function
- decreased urinary volume
Other diagnostic factors
- use of a triggering medication
- age >65 years
- chronic inflammatory disease
1st investigations to order
- serum creatinine and blood urea nitrogen (BUN)
- CBC with WBC differential
- trial of discontinuing triggering medication
- antineutrophil cytoplasmic antibody (ANCA)
- antinuclear antibody (ANA)
- anti-double stranded DNA (anti-ds DNA)
- complement profile
Investigations to consider
- kidney ultrasound
- kidney biopsy
- kidney gallium scan
- urine cytokines
chronic inflammatory disease related
- Acute glomerulonephritis
- Acute tubular necrosis
- Acute vascular injury
- ACR appropriateness criteria: renal failure
- Acute kidney injury: prevention, detection and management
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