Clinical characteristics, causes and outcomes of acute interstitial nephritis in the elderly.

Acute interstitial nephritis (AIN) is an important cause of acute kidney injury (AKI), and its prevalence in the elderly may be increasing. It is largely unknown whether AIN in the elderly is similar to that in younger adults; therefore, we investigated the causes and characteristics of AIN in 45 elderly patients (65 years and older) and in 88 younger adults (18-64 years old). Compared with younger patients, the elderly had significantly more drug-induced AIN (87 vs. 64%), proton pump inhibitor-induced AIN (18 vs. 6%), but significantly less AIN due to autoimmune or systemic causes (7 vs. 27%). The two most common culprit drugs in the elderly were penicillin and omeprazole. Compared with younger patients, the elderly had higher prevalence of baseline CKD, higher peak creatinine, and more need for dialysis, all of which were significant. Among the elderly, 86% showed partial or complete recovery within 6 months. Significantly shorter delays in initiation of steroids correlated with recovery at 6 months. Lack of early recovery tended to correlate with progressive CKD. Compared with antibiotic-induced AIN, proton pump inhibitor-induced AIN had less severe AKI, but a longer duration of drug exposure, and was less likely to recover by 6 months, all significant. Thus, the vast majority of AIN cases in the elderly are due to drugs, primarily owing to proton pump inhibitors and antibiotics, while AIN of autoimmune or systemic origin is uncommon.

Biopsy-proven acute interstitial nephritis, 1993-2011: a case series.

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. STUDY DESIGN: Case series. SETTING & PARTICIPANTS: 133 patients with biopsy-proven AIN from 1993 through 2011 at a single center. OUTCOMES: 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). LIMITATIONS: 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.

Idiopathic nodular glomerulosclerosis in Chinese patients: a clinicopathologic study of 20 cases.

BACKGROUND: The objective of this study is to investigate the frequency and clinicopathological features of idiopathic nodular glomerulosclerosis (ING) in Chinese patients, on which there has been no previously published information. METHODS: Native kidney biopsies performed at a kidney histopathological center in Shanghai between January 1, 2009 and December 31, 2011 were retrospectively examined and relevant clinical data were reviewed. RESULTS: All kidney biopsy specimens (3,480) were examined. After excluding specimens from patients with diabetes, fasting hyperglycemia or hemoglobin A1c elevation and other known entities associated with nodular glomerulosclerosis, 20 ING cases (1 in 174 biopsies) were identified. Patients with ING had a median age of 55.5 years, 16 (80 %) were male, 19 (95 %) had a body mass index (BMI) ≥25 kg/m(2) [BMI ≥30 in 8 (40 %)], 18 (90 %) were hypertensive, 17 (85 %) had a history of cigarette smoking (mean pack-years 19.8 ± 2.4), and 10 (50 %) had hyperlipidemia. All 20 patients had >1 g/day proteinuria with a mean of 2.85 ± 0.33 g/day (seven had nephrotic-range proteinuria). Mean serum creatinine at the time of kidney biopsy was 4.23 ± 0.53 mg/dL (338.2 ± 44.7 µmol/L). Histopathologically, all specimens showed varying degrees of nodular glomerulosclerosis, glomerular basement membrane thickening, foot process effacement, interstitial fibrosis and arterial hyalinosis/sclerosis. Immunofluorescence was non-specific. At follow-up of 22.1 ± 1.15 days post-biopsy, six patients had developed end-stage renal failure and five had worsening serum creatinine concentrations not requiring dialysis. CONCLUSION: ING is rare and appears to be associated with overweight, hypertension and cigarette smoking in Chinese patients.

Utility of urine eosinophils in the diagnosis of acute interstitial nephritis.

BACKGROUND AND OBJECTIVES: Urine eosinophils (UEs) have been shown to correlate with acute interstitial nephritis (AIN) but the four largest series that investigated the test characteristics did not use kidney biopsy as the gold standard. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This is a retrospective study of adult patients with biopsy-proven diagnoses and UE tests performed from 1994 to 2011. UEs were tested using Hansel's stain. Both 1% and 5% UE cutoffs were compared. RESULTS: This study identified 566 patients with both a UE test and a native kidney biopsy performed within a week of each other. Of these patients, 322 were men and the mean age was 59 years. There were 467 patients with pyuria, defined as at least one white cell per high-power field. There were 91 patients with AIN (80% was drug induced). A variety of kidney diseases had UEs. Using a 1% UE cutoff, the comparison of all patients with AIN to those with all other diagnoses showed 30.8% sensitivity and 68.2% specificity, giving positive and negative likelihood ratios of 0.97 and 1.01, respectively. Given this study's 16% prevalence of AIN, the positive and negative predictive values were 15.6% and 83.7%, respectively. At the 5% UE cutoff, sensitivity declined, but specificity improved. The presence of pyuria improved the sensitivity somewhat, with a decrease in specificity. UEs were no better at distinguishing AIN from acute tubular necrosis compared with other kidney diseases. CONCLUSIONS: UEs were found in a variety of kidney diseases besides AIN. At the commonly used 1% UE cutoff, the test does not shift pretest probability of AIN in any direction. Even at a 5% cutoff, UEs performed poorly in distinguishing AIN from acute tubular necrosis or other kidney diseases.