Kidney Biopsy-Related Complications in Hospitalized Patients with Acute Kidney Disease

Percutaneous Kidney Biopsy and the Utilization of Blood Transfusion and Renal Angiography Among Hospitalized Adults

Introduction

Data on percutaneous kidney biopsy (KBx) incidence and frequencies of hemorrhagic complications among inpatients are limited.

Methods

Using nationally representative US hospitalization discharge data, we report temporal trends in inpatient KBx rates from 2007 to 2014 and estimate frequencies of, and risk factors for, utilization of packed red blood cell (pRBC) transfusion and renal angiography.

Results

From 2007 to 2014, rates of native KBx among adult inpatients increased from 8.2 to 10.0 per 100,000, while transplant KBx rates declined from 3.6 to 3.1 per 100,000. We studied 35,183 and 14,266 discharge records with native and transplant KBx. We found that 5.7% (95% confidence interval [CI]: 5.3%–6.0%) of inpatients undergoing native KBx and 4.9% (4.2%–5.5%) of those undergoing transplant KBx received a pRBC transfusion within 2 days of biopsy. Similarly, 0.6% (0.5%–0.7%) of inpatients undergoing native KBx and 0.4% (0.2%–0.5%) undergoing transplant KBx received a renal angiogram within 2 days of KBx. For inpatient native KBx, female sex, older age, higher chronic kidney disease stage, acute renal failure, lupus, vasculitis, cirrhosis, multiple myeloma/paraproteinemia, and anemia of chronic disease were independently associated with increased odds of pRBC transfusion; cirrhosis and end-stage renal disease (ESRD) were associated with increased odds, and nephrotic syndrome was associated with decreased odds, of renal angiography.

Conclusions

In this large population-based study of inpatient KBx practices, we demonstrate increasing rates of inpatient native KBx among US adults and provide accurate estimates of the frequencies of, and risk factors for, pRBC transfusion and renal angiography following inpatient KBx.

Differentiating Acute Interstitial Nephritis from Acute Tubular Injury: A Challenge for Clinicians

BACKGROUND

Differentiating etiologies of acute kidney injury (AKI) is critical in determining the course of care in clinical practice. For example, acute interstitial nephritis (AIN) requires withdrawal of the offending drug and immunosuppressive therapy, while acute tubular injury (ATI) does not have any disease-specific therapies. Failure to distinguish AIN from ATI in a timely manner can lead to kidney fibrosis and chronic kidney disease. In this review, we discuss current tests and novel biomarkers to distinguish ATI from AIN.

SUMMARY

In a prospective cohort study of 32 participants with AIN and 41 with ATI, clinical features and current, laboratory tests did not provide sufficient distinction between the 2 subpopulations of AKI. The findings in our cohort are consistent with our review of the literature. Given the limitations of clinical features and laboratory assessments, clinical practice relies on kidney biopsy for histological diagnosis, which is not always feasible, and is associated with bleeding complications in high-risk populations. In addition, histological diagnosis is prone to sampling errors and inter-rater variability. In the interest of identifying a novel biomarker, we compared urine and plasma levels of cytokines in the Th1, Th2, and Th9 pathways, which have been implicated in the pathogenesis of AIN. Urine TNF-α and interleukin-9 were higher in AIN participants than in ATI controls and helped discriminate AIN from ATI (area under curve 0.83 [0.73-0.92]). Key Messages: Differentiation between AIN and ATI in patients with AKI using currently available tests is challenging. Urine TNF-α and interleukin-9 may help clinicians separate AIN from ATI.

Complications of Percutaneous Renal Biopsy

Percutaneous renal biopsy is widely used for diagnosis, prognosis, and management of nephropathies. Complications may arise after renal biopsy, most commonly in the form of bleeding. Efforts should be taken to optimize modifiable risk factors such as hypertension, thrombocytopenia, and coagulopathy prior to the procedure. Unmodifiable risk factors such as poor renal function, gender, and underlying histologic diagnosis may be used to identify high-risk patients. Delayed presentation of bleeding complications is common, and close clinical follow-up is crucial.

Urine TNF-α and IL-9 for clinical diagnosis of acute interstitial nephritis

BACKGROUNDClinical diagnosis of acute interstitial nephritis (AIN) is challenging because of lack of a diagnostic biomarker and requires a kidney biopsy. We hypothesized that AIN is mediated by specific T cell subsets such that specific T cell cytokine levels could serve as biomarkers to distinguish AIN from other causes of acute kidney disease (AKD).METHODSWe enrolled consecutive sampling participants who underwent a kidney biopsy for AKD evaluation at 2 centers between 2015 and 2018. Three pathologists independently established AIN diagnosis through review of kidney biopsies. Through univariable and multivariable analysis of 12 selected urine and plasma cytokines, we identified 2 that were diagnostic of AIN.RESULTSOf the 218 participants, 32 (15%) were diagnosed with AIN by all 3 pathologists. Participants with AIN had consistently higher levels of urine TNF-α and IL-9 than those with other diagnoses, including acute tubular injury, glomerular diseases, and diabetic kidney disease, and those without any kidney disease. As compared with participants in the lowest quartile, we noted higher odds of AIN in participants in the highest quartiles of TNF-α levels (adjusted odds ratio, 10.9 [1.8, 65.9]) and IL-9 levels (7.5 [1.2, 45.7]) when controlling for blood eosinophils, leukocyturia, and proteinuria. Addition of biomarkers improved area under receiver operating characteristic curve over clinicians' prebiopsy diagnosis (0.84 [0.78, 0.91]) vs. 0.62 [(0.53, 0.71]) and a model of current tests (0.84 [0.76, 0.91] vs. 0.69 [0.58, 0.80]).CONCLUSIONSInclusion of urinary TNF-α and IL-9 improves discrimination over clinicians' prebiopsy diagnosis and currently available tests for AIN diagnosis.FUNDINGSupported by NIH awards K23DK117065, T32DK007276, K24DK090203, K23DK097201, R01DK113191, UG3-DK114866, P30DK079310; the Robert E. Leet and Clara Guthrie Patterson Trust; and American Heart Association award 18CDA34060118.