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Waikar, Sushrut

Background: The patterns, performance characteristics, and yield of diagnostic tests ordered for the evaluation of acute kidney injury (AKI) have not been rigorously evaluated. Methods: We characterized the frequency of AKI diagnostic testing for urine, blood, radiology, and pathology tests in all adult inpatients who were admitted with or developed AKI (N = 4903 patients with 5731 AKI episodes) during a single calendar year. We assessed the frequency of abnormal test results overall and by AKI stage. We manually reviewed electronic medical records to evaluate the diagnostic yield of selected urine, blood, and radiology tests. Diagnostic yield of urine and blood tests was determined based on whether an abnormal test affected AKI diagnosis or management, whereas diagnostic yield of radiology tests was based on whether an abnormal test resulted in a procedural intervention. In sensitivity analyses we also evaluated appropriateness of testing using prespecified criteria. Results: Frequency of testing increased with higher AKI stage for nearly all diagnostic tests, whereas frequency of detecting an abnormal result increased for some, but not all, tests. Frequency of detecting an abnormal result was highly variable across tests, ranging from 0 % for anti-glomerular basement membrane testing to 71 % for urine protein testing. Many of the tests evaluated had low diagnostic yield. In particular, selected urine and blood tests were unlikely to impact AKI diagnosis or management, whereas radiology tests had greater clinical utility. Conclusions: In patients with AKI, many of the diagnostic tests performed, even when positive or abnormal, may have limited clinical utility.

Background: Acute kidney injury requiring renal replacement therapy (AKI-RRT) is associated with high morbidity, mortality and resource utilization. The type of vascular access placed for AKI-RRT is an important decision, for which there is a lack of evidence-based guidelines. Methods: We conducted a prospective cohort study over a 16-month period with 154 patients initiated on AKI-RRT via either a non-tunneled dialysis catheter (NTDC) or a tunneled dialysis catheter (TDC) at an academic hospital. We compared differences in renal replacement delivery and mechanical and infectious outcomes between NTDCs and TDCs. Results: Patients who received TDCs had significantly better RRT delivery, both with continuous venovenous hemofiltration (CVVH) and intermittent hemodialysis (IHD), compared to patients who received NTDCs; these findings were confirmed after multivariable adjustment for AKI-specific disease severity score, history of chronic kidney disease, renal consult team, and AKI cause. In CVVH and IHD, the median venous and arterial blood flow pressures were significantly higher with TDCs compared to NTDCs (p < 0.001). Additionally for CVVH, the median number of interruptions per catheter was higher with NTDCs compared to TDCs (Rate Ratio (RR) 2.7; p < 0.001), and for IHD, a higher median blood flow was seen with TDCs (p < 0.001). There were a significantly higher number of mechanical complications with NTDCs (RR 13.6 p = 0.001). No significant difference was observed between TDCs and NTDCs for positive blood cultures per catheter. Conclusions: Compared to NTDCs, TDCs for patients with AKI-RRT had improved RRT delivery and fewer mechanical complications. Initial TDC placement for AKI-RRT should be considered when not clinically contraindicated given the potential for improved RRT delivery and outcomes. Electronic supplementary material The online version of this article (10.1186/s12882-017-0760-x) contains supplementary material, which is available to authorized users.

Heme oxygenase-1 (HO-1) catalyzes the degradation of heme, which may be involved in the pathogenesis of AKI. Length polymorphisms in the number of GT dinucleotide repeats in the HO-1 gene (HMOX1) promoter inversely associate with HMOX1 mRNA expression. We analyzed the association between allelic frequencies of GT repeats in the HMOX1 gene promoter and postoperative AKI in 2377 white patients who underwent cardiac surgery with cardiopulmonary bypass. We catego- rized patients as having the short allele (S; ,27 GT repeats) or long allele (L; $27 GT repeats), and defined AKI as an increase in serum creatinine $0.3 mg/dl within 48 hours or $50% within 5 days, or the need for RRT. Compared with patients with the SS genotype, patients with the LL genotype had 1.58-fold (95% confidence interval, 1.06 to 2.34; P=0.02) higher odds of AKI. After adjusting for baseline and operative characteristics, the odds ratio for AKI per L allele was 1.26 (95% confidence interval, 1.05 to 1.50; P=0.01). In conclusion, longer GT repeats in the HMOX1 gene pro- moter associate with increased risk of AKI after cardiac surgery, consistent with heme toxicity as a pathogenic feature of cardiac surgery-associated AKI, and with HO-1 as a potential therapeutic target.