Clinical and quality aspects of native and transplant kidney biopsies in Sweden

Percutaneous kidney biopsies have been performed since 1944 to establish diagnoses and treatment. Risk factors based on a limited amount of data have shown age, blood pressure, kidney function and needle size as some risk factors for biopsy complications. Although the techniques of biopsy have improved over the years, it is still an invasive procedure and serious complications can occur. The overall aim of this thesis was to obtain a large series of data from biopsy procedures and to use these to bring further light on risk factors to help minimize the risk for patients and to optimize diagnostics. Specific aims were to clarify if different factors, such as gender, diagnoses, localization of biopsies, needle types and sizes, could be useful to help minimize complication risks in native kidney biopsies (Nkb) and transplant kidney biopsies (Txb). Another point to investigate was the value of the Resistive Index (RI) obtained at ultrasound before performing Txb. Materials and methods: A protocol for prospective multicentre registration of various factors and complications associated with Nkb and Txb was designed. Consecutive data were obtained from seven hospitals. All biopsies, except one computer tomography-guided Nkb, were performed using real-time ultrasound guidance and an automated spring-loaded biopsy device. For the biopsies 14- to 20- Gauge (G) needles were used. The kidney function level, i.e. estimated glomerular filtration rate (eGFR), was calculated using the Modification of Diet in Renal Disease (MDRD) formula (GFR in mL/min per 1.73m2). For statistical analyses the IBM SPSS Statistic 22 (Armonk, NY, USA) and OpenEpi (Open Source Epidemiologic Statistics for Public Health, www.OpenEpi.com) were used. Data were presented as Odds Ratio (OR), Risk Ratio (RR) and Confidence Intervals (CI). A two sided p-value of <0.05 was considered significant. In total 1299 consecutive biopsies (1039 native and 260 transplant kidneys) in 1178 patients (456 women and 722 men) were used for investigation. The median age of patients was 55 years (range 16 to 90 years). Major (require an intervention) and minor biopsy complications (no need of intervention) were registered. Results: The overall frequency of biopsy complications for Nkb was 8.8% (major 6.7%, minor 2.1%) and for Txb was 6.5% (major 3.8%, minor 2.7%); no death. Women had a higher risk for development of major (10.7% versus 4.7%, OR 2.4, CI 1.4-4.2) and overall biopsy complications (13.2% versus 6.5%, OR 2.2, CI 1.4-3.5) compared to men in Nkb. In Nkb, major complications were more common after biopsies from the right kidney in women versus men (10.8% vs 3.1%, OR 3.7, CI 1.5–9.5), in patients with lower versus higher BMI (25.5 vs 27.3, p=0.016) and for younger versus older age (44.8 vs 52.3 years, p=0.002). Lower (90 mmHg) compared to higher (98 mmHg) mean arterial pressure in Txb indicated a risk of major complications (p=0.039). Factors such as number of passes and kidney function did not influence complication rates. Biopsy needles of 16 G compared to 18 G showed more glomeruli per pass in Nkb (11 vs 8, p<0.001) and in Txb (12 vs 8, p<0.001). Sub-analysis revealed that 18 G 19 mm side-notch needles in Nkb resulted in more major (11.3% vs 3%, OR 4.1, CI 1.4-12.3) and overall complications (12.4% vs 4.8%, OR 2.8, CI 1.1-7.1) in women than in men. If the physician had performed less compared to more than four Nkb per year, minor (3.5% vs 1.4%, OR 2.6, CI 1.1-6.2) and overall complications (11.5% vs 7.4%, OR 1.6, CI 1.1-2.5) were more common. The localization of biopsy within the kidney (Nkb and Txb) was not a risk factor for complications. Patients with IgA-nephritis compared to patients with other diseases had a higher risk of major complications (11.7% vs 6.4 %, OR 1.8, CI 1.1–3.2). More major complications were found in Nkb if they had higher versus lower degree of glomerulosclerosis (31% vs 20 %, p=0.008) and in Txb if there was a higher versus lower degree of interstitial fibrosis (82% vs 33%, p<0.001). Re-biopsies (Nkb) were more common in patients with IgA-nephritis than those with other diseases (4.7% vs 1.3 %, OR 4, CI 1.5–11), in younger versus older age (42.6 vs 52.3 years, p=0.031), and in those with a higher versus lower degree of interstitial fibrosis (63% vs 34 %, p=0.046). In Txb, a RI≥0.8 compared to RI<0.8 predicted major (13.3% vs 3.2%, RR 4.2, CI 1.3-14.1) and overall biopsy complications (16.7% vs 5.3%, RR 3.2, CI 1.2-8.6). In the group <0.8, RI correlated with age (rs=0.28, p<0.001) and systolic blood pressure (rs=0.18, p=0.02). In the group ≥0.8, RI correlated with degree of interstitial fibrosis (rs=0.65, p=0.006) and systolic blood pressure (rs=0.40, p=0.03). The multiple regression analysis showed that the <0.8 RI group correlated only with age (p<0.001), whereas the ≥0.8 RI group correlated only with the degree of interstitial fibrosis (p=0.003). Conclusions: The present results motivate greater attention to be paid to the possibility of major side-effects after Nkb in women and biopsies from their right side, but as well in younger patients, and in those with lower BMI. This also applies for patients with presumptive IgA-nephritis and higher degree of glomerulosclerosis. In Txb, patients with higher degree of interstitial fibrosis had a greater risk of major complications. Moreover, the present data indicate that Nkb and Txb should be preferably taken with 16 G needles with 20 mm sample size. This results in better histological quality and there is a lower risk for major complications as compared to 18 G needles. The localization of biopsy within the kidney (Nkb and Txb) does not alter complication rates. For Nkb there were fewer complications if the physician had performed at least four biopsies per year. A RI≥0.8 in Txb indicates a greater risk for major and overall complications