title: Biopsy-proven acute interstitial nephritis, 1993-2011: a case series.
abstract: BACKGROUND
  Acute interstitial nephritis (AIN) is an important cause of acute kidney injury, especially in hospitalized patients. The cause and outcome of AIN, particularly that due to drugs, is changing with prevalent medication use. The effectiveness of steroids for treatment of AIN is debated.
  
  
  METHODS
  Case series.
  
  
  METHODS
  133 patients with biopsy-proven AIN from 1993 through 2011 at a single center.
  
  
  RESULTS
  Recovery of kidney function by 6 months, either complete, partial, or none. Complete recovery was defined as improvement in serum creatinine level to within 25% of baseline (or < 1.4 mg/dL), and partial recovery, as a ≥ 50% decrease in serum creatinine level from its peak value but not reaching within 25% of its baseline value.
  
  
  RESULTS
  Causes of AIN included drugs (70%), autoimmune diseases (20%), and infections (4%). Drug-induced AIN was due to antibiotics in 49%, proton pump inhibitors (PPIs) in 14%, and nonsteroidal anti-inflammatory drugs (NSAIDs) in 11%. Overall, the top 3 drug causes were omeprazole (12%), amoxicillin (8%), and ciprofloxacin (8%). Patients with drug-induced compared to non-drug-induced AIN were older and had higher baseline kidney function, but more severe acute kidney injury. Patients with PPI-induced AIN were older, were less symptomatic, and had longer durations of drug exposure and longer delays in getting kidney biopsy and steroids than for antibiotic-induced or NSAID-induced AIN. At 6 months postbiopsy, 49% of patients with drug-induced AIN treated with steroids achieved complete recovery; 39%, partial recovery; and 12%, no recovery. Correlates of poor recovery included a longer duration of drug exposure (15 vs 30 vs 130 days for complete, partial, and no recovery, respectively; P = 0.04) and longer delay in starting steroid therapy (8 vs 11 vs 35 days, respectively; P = 0.05).
  
  
  CONCLUSIONS
  Retrospective study, selection bias in patients who had kidney biopsy, single-center experience.
  
  
  CONCLUSIONS
  The cause of AIN may be shifting; PPIs are emerging as an important contributor to this disease. Delays in discontinuation of the culprit drug and in initiating steroid treatment adversely affect recovery of kidney function.
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN. Electronic address: muriithi.angela@mayo.edu.
authors.forename: Angela K
authors.initials: AK
authors.lastname: Muriithi
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic, Rochester, MN.
authors.forename: Nelson
authors.initials: N
authors.lastname: Leung
authors.affiliation: Division of Nephrology, Columbia University, College of Physicians and Surgeons, New York, NY.
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Valeri
authors.affiliation: Division of Anatomic Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Lynn D
authors.initials: LD
authors.lastname: Cornell
authors.affiliation: Division of Anatomic Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Sethi
authors.affiliation: Division of Anatomic Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Mary E
authors.initials: ME
authors.lastname: Fidler
authors.affiliation: Division of Anatomic Pathology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN.
authors.forename: Samih H
authors.initials: SH
authors.lastname: Nasr
mesh_terms: D000208:Acute Disease; D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000009:adverse effects*; D001706:Biopsy / Q000379:methods / Q000706:statistics & numerical data; D003404:Creatinine / Q000032:analysis*; D005260:Female; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D007668:Kidney / Q000473:pathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000139:chemically induced / Q000175:diagnosis / Q000188:drug therapy / Q000453:epidemiology / Q000503:physiopathology; D017063:Outcome Assessment, Health Care; D015995:Prevalence; D054328:Proton Pump Inhibitors / Q000009:adverse effects*; D020127:Recovery of Function; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology
chemical_list: D000900:Anti-Bacterial Agents; D000894:Anti-Inflammatory Agents, Non-Steroidal; D005938:Glucocorticoids; D054328:Proton Pump Inhibitors; D003404:Creatinine
keywords: Acute interstitial nephritis (AIN); case series; drug-induced AIN; etiology of AIN; kidney biopsy; prognosis; proton pump inhibitor (PPI); renal failure; steroid treatment of AIN