The true incidence of acute interstitial nephritis (AIN) is unknown. Definitive diagnosis requires a biopsy, which may not be performed due to subtle clinical presentation or risk factors for complications, and hence the incidence is underestimated.[4]Praga M, Sevillano A, Auñón P, et al. Changes in the aetiology, clinical presentation and management of acute interstitial nephritis, an increasingly common cause of acute kidney injury. Nephrol Dial Transplant. 2015 Sep;30(9):1472-9.
https://academic.oup.com/ndt/article/30/9/1472/2459920
http://www.ncbi.nlm.nih.gov/pubmed/25324356?tool=bestpractice.com
One study found that AIN incidence was 3.2 per 10,000 person-years in users of proton-pump inhibitors.[5]Antoniou T, Macdonald EM, Hollands S, et al. Proton pump inhibitors and the risk of acute kidney injury in older patients: a population-based cohort study. CMAJ Open. 2015 Apr-Jun;3(2):E166-71.
http://cmajopen.ca/content/3/2/E166.long
http://www.ncbi.nlm.nih.gov/pubmed/26389094?tool=bestpractice.com
Best available estimates come from measuring the prevalence of AIN in kidney biopsy registries. In unselected biopsies, around 2% of cases have AIN, whereas in biopsies of acute kidney injury, the prevalence of AIN is up to 18%.[1]Raghavan R, Eknoyan G. Acute interstitial nephritis - a reappraisal and update. Clin Nephrol. 2014 Sep;82(3):149-62.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4928030
http://www.ncbi.nlm.nih.gov/pubmed/25079860?tool=bestpractice.com
[4]Praga M, Sevillano A, Auñón P, et al. Changes in the aetiology, clinical presentation and management of acute interstitial nephritis, an increasingly common cause of acute kidney injury. Nephrol Dial Transplant. 2015 Sep;30(9):1472-9.
https://academic.oup.com/ndt/article/30/9/1472/2459920
http://www.ncbi.nlm.nih.gov/pubmed/25324356?tool=bestpractice.com
[6]Wilson GJ, Kark AL, Francis LP, et al. The increasing rates of acute interstitial nephritis in Australia: a single centre case series. BMC Nephrol. 2017 Oct 31;18(1):329.
https://bmcnephrol.biomedcentral.com/articles/10.1186/s12882-017-0747-7
http://www.ncbi.nlm.nih.gov/pubmed/29089041?tool=bestpractice.com
AIN is the cause of end stage kidney disease in 1% of patients.[7]United States Renal Data System. 2019 USRDS annual data report: Epidemiology of kidney disease in the United States. 2019 [internet publication].
https://www.niddk.nih.gov/about-niddk/strategic-plans-reports/usrds
In one study, women were more likely to have nonsteroidal anti-inflammatory drug-associated AIN and immune-mediated AIN.[6]Wilson GJ, Kark AL, Francis LP, et al. The increasing rates of acute interstitial nephritis in Australia: a single centre case series. BMC Nephrol. 2017 Oct 31;18(1):329.
https://bmcnephrol.biomedcentral.com/articles/10.1186/s12882-017-0747-7
http://www.ncbi.nlm.nih.gov/pubmed/29089041?tool=bestpractice.com
Drug-induced AIN is more common in older patients, with antibiotics, proton-pump inhibitors, and NSAIDs the most frequently implicated.[8]Nast CC. Medication-induced interstitial nephritis in the 21st century. Adv Chronic Kidney Dis. 2017 Mar;24(2):72-9.
http://www.ncbi.nlm.nih.gov/pubmed/28284382?tool=bestpractice.com
[9]Muriithi AK, Leung N, Valeri AM, et al. Clinical characteristics, causes and outcomes of acute interstitial nephritis in the elderly. Kidney Int. 2015 Feb;87(2):458-64.
https://www.kidney-international.org/article/S0085-2538(15)30061-2/fulltext
http://www.ncbi.nlm.nih.gov/pubmed/25185078?tool=bestpractice.com