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Introduction There is an increased risk of thrombotic complications in patients with COVID‐19. Hemodialysis patients are already at an increased risk for thromboembolic events such as stroke and pulmonary embolism. The aim of our study was to determine the incidence of late thrombotic complications (deep vein thrombosis, pulmonary embolism, stroke, new‐onset vascular access thrombosis) in maintenance hemodialysis patients after recovery from COVID‐19. Methods We performed a retrospective cohort study of 200 prevalent hemodialysis patients in our center at the start of the pandemic. We excluded incident patients after the cohort entry date and those who required hemodialysis for acute kidney injury, and excluded patients with less than 1 month follow‐up due to kidney transplantation or death from non‐thrombotic causes. Findings One‐hundred and eighty five prevalent hemodialysis patients finally met the inclusion criteria; 37 patients (17.6%) had SARS‐CoV‐2 infection, out of which 10 (27%) died during the acute phase of disease without evidence of thrombotic events. There was an increased risk of thrombotic events in COVID‐19 survivors compared to the non‐infected cohort (18.5% vs. 1.9%, p = 0.002) after a median follow‐up of 7 months. Multivariate regression analysis showed that COVID‐19 infection increased risk for late thrombotic events adjusted for age, sex, hypertension, diabetes, antithrombotic treatment, and previous thrombotic events (Odds Ratio (OR) 26.4, 95% confidence interval 2.5–280.6, p = 0.01). Clinical and laboratory markers did not predict thrombotic events. Conclusions There is an increased risk of late thrombotic complications in hemodialysis patients after infection with COVID‐19. Further studies should evaluate the benefit of prolonged prophylactic anticoagulation in hemodialysis patients after recovery from COVID‐19.

BACKGROUND AND AIMS The gold standard for measurement of protein excretion is a 24-h urine collection. However, due to the cumbersome nature as well as the frequent errors in sample collection, it has been suggested that the measurement of albumin-creatinine ratio (ACR) in a spot urine sample could replace 24-h proteinuria as a valid method for the diagnosis and follow-up of renal disease, which is supported by the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines. The aim of our study was to assess the correlation between 24-h proteinuria and spot urine ACR in patients with biopsy-proven glomerulonephritis, METHOD We identified patients with biopsy-proven glomerular diseases who were evaluated during their disease course at our center between 1 January 2005 and 31 December 2021, and included patients with paired 24 h and spot urine samples simultaneously collected at the same day. We excluded patients with interstitial or vascular causes for kidney disease. We contrasted correlation of ACR and 24 h proteinuria according to demographic data, glomerular filtration rate measured at the day of urine collection, and type of glomerular disease. RESULTS A total of 977 paired 24-hr proteinuria and spot urine ACR samples were collected at the same day from 370 patients and included in this study. The mean age of the selected population was 52.1 ± 17.7 years, with a median serum creatinine of 1.26 mg/dL (IQR: 0.94–1.74) and mean eGFR measured by CKD-EPI of 62.4 ± 30.1 mL/min. Median 24-h proteinuria was 1.48 g/day (IQR: 0.59–3.39), and the median ACR was 539 mg/g (IQR: 131–1569). We found an excellent correlation between ACR and 24-h proteinuria (Spearman's r = 0.86, P 3 g/day (Spearman's r = 0.50, P ROC analysis showed that a ACR cutoff of >250 mg/g was the best predictor for 24-h proteinuria >1 g/day, with an area under the curve (AUC) of 0.933, sensitivity 91% and specificity 81%, while an ACR cutoff of >800 mg/g best predicted a 24-hour proteinuria of >3.5 g/day, with an AUC of 0.922, sensitivity of 92% and specificity of 76%. CONCLUSION There is an excellent correlation between ACR and 24-h proteinuria in patients with proteinuria 3 g/day, ACR correlates poorly with proteinuria. We suggest that patients with higher grade proteinuria should always be assessed with a 24-h urine sample protein excretion for therapeutic decisions and follow-up in glomerular diseases.

BACKGROUND AND AIMS Acute interstitial nephritis (AIN) is one of the most frequent causes of acute kidney injury (AKI). Interstitial inflammation can lead to tubular epithelial infiltration producing tubular dysfunction, which could be clinically detected by glycosuria (with or without Fanconi syndrome), leukocyturia, microscopic haematuria or tubular proteinuria. The aim of this study was to determine the predictive value of renal glycosuria in AKI for the diagnosis of AIN. METHOD We conducted a retrospective study of kidney biopsies performed at out centre between May 1998 and December 2021, and included patients whose kidney biopsy was performed while presenting with AKI. We excluded patients with other indications for kidney biopsy, patients with diabetes mellitus and patients who presented a serum glucose level of > 120 mg/dL at presentation. We registered demographic, clinical and laboratory variables at presentation of AKI, and compared patients with a final diagnosis of AIN to patients with other causes of AKI. RESULTS The study included 211 patients; 39 patients (18.5%) with a diagnosis of AIN and 172 patients (81.5%) with other diagnoses for AKI. Eight patients with AIN presented with renal glycosuria (20.5%) compared with seven patients with other causes of AKI (4.1%) (P 100 mg/dL of glycosuria had a specificity of 99.4% for the diagnosis of AIN, with a positive predictive value of 75% (24.3–96.6) and a positive likelihood ratio of 13.2 (1.4–123.8). CONCLUSION AIN can lead to proximal tubular dysfunction, which can be clinically expressed as renal glycosuria. The presence of renal glycosuria in patients with AKI guides towards the diagnosis of AIN, with an excellent specificity when glycosuria > 100 mg/dL.

BACKGROUND AND AIMS It has been postulated that the protein-creatinine ratio in spot urine sample (uPCR) could be an adequate alternative to measurement of proteinuria in 24-h urine samples (24-h proteinuria), which despite being the gold standard for the diagnosis and follow-up of patients with kidney disease, its accuracy is frequently influenced by incorrect sample collection. Several studies have shown a correlation between uPCR in spot urine samples and 24-h proteinuria. However, in daily clinical practice we often find significant differences between both measurements. Therefore, we set out to conduct this study to analyze the concordance between uPCR in first morning spot urine samples and 24-h proteinuria in patients with biopsy-proven glomerular diseases. METHOD We identified patients with biopsy-proven glomerular diseases who were evaluated during their disease course at our center between January 1, 2005 and December 31, 2021, and included patients with paired 24-h protein excretion measurement and spot urine samples that measured protein and creatinine concentration, simultaneously collected at the same day. We excluded patients with interstitial or vascular causes for kidney disease. We performed correlation analyses of uPCR and 24-h proteinuria globally and analyzed the influence of demographic data as well as eGFR and type of glomerular disease in this relationship. The concordance between both measurements was compared using intra-class correlation coefficients (ICC) and Bland–Altman plots. RESULTS About 351 patients with simultaneous uPCR and 24-h proteinuria measured at the same day were included in the study, 67.2% were male and the mean age was 53.9 ± 17.9. Median serum creatinine was 1.28 mg/dl (IQR 0.95–1.86) and mean eGFR measured by CKD-EPI was 60.1 ± 30.6 mL/mi/1.73 m2. Median 24-h proteinuria was 1.70 g/day (IQR: 0.62–3.45) and median uPCR was 1.09 g/g (IQR: 0.35–2.70). Wilcoxon rank test showed a systematic underestimation of uPCR compared with 24-h proteinuria (Z = −8.22, P 60 mL/min of 0.79 (CI 95%: 0.71–0.85, P 3 g/day for 24-h proteinuria, and 3 g/g for uPCR), we performed Cohen's κ test to determine agreement, finding moderate agreement between measurements (κ = 0.46, P CONCLUSION The level of concordance between proteinuria from 24-h urine samples and protein–creatinine ratio from spot urine samples is high regardless of eGFR, age, sex and type of glomerular disease. However, the level of agreement decreases in nephrotic-range proteinuria. Therefore, we suggest that uPCR could be an appropriate measure to assess and follow-up patients with glomerular diseases and non-nephrotic range proteinuria, while the degree of proteinuria should still be monitored with 24-h urine specimens in patients with proteinuria >3.5 g/day.

Background With the ageing population and changes in the indications of diagnostic and protocol biopsies in systemic lupus erythematosus in recent years, an impact on the incidence and presentation of lupus nephritis (LN) is expected. The aim of this study was to analyse the epidemiological changes regarding clinical and histological presentation of LN in kidney biopsies performed from 1994 to 2019 included in the Spanish Registry of Glomerulonephritis. Methods We analysed data from 28 791 kidney biopsies from 130 Spanish hospitals comparing demographic, clinical and histological data. We divided the cohort according to the age of onset of LN into pediatric onset (50 years). Results The incidence of LN has decreased from 9.6% of all kidney biopsies in the period 1994–2013 to 7% in the last quarter of the observation period (2014–2019) (P Conclusions The frequency of biopsy-proven LN has been decreasing in recent years, despite an increasing number of repeat biopsies. Late-onset LN is increasing, presenting with worse kidney function but fewer proliferative lesions compared with younger-onset LN.

Background and Aims There is an increased risk of thrombotic complications in patients with COVID-19. Hemodialysis patients are already at an increased risk for thromboembolic events such as stroke and pulmonary embolism. The aim of our study was to determine the incidence of late thrombotic complications (deep vein thrombosis, pulmonary embolism, stroke, new-onset vascular access thrombosis) in maintenance hemodialysis patients after recovery from COVID-19. Method We performed a retrospective cohort study of 200 prevalent hemodialysis patients in our center at the start of the pandemic. We excluded incident patients after the cohort entry date and those who required hemodialysis for acute kidney injury, and excluded patients with less than 1 month follow-up due to kidney transplantation or death from non-thrombotic causes. Results 185 prevalent hemodialysis patients finally met the inclusion criteria; 37 patients (17.6%) had SARS-CoV-2 infection, out of which 10 (27%) died during the acute phase of disease without evidence of thrombotic events. There was an increased risk of thrombotic events in COVID-19 survivors compared to the non-infected cohort (18.5% vs 1.9%, p=0.002) after a median follow-up of 7 months. Stroke incidence was 38.9 episodes/1000 patient-years in patients infected with SARS-CoV-2, compared to an incidence of 2.8 episodes/1000 patient-years in non-infected patients during the follow-up period. The median time from diagnosis of SARS-CoV-2 to the first thrombotic event was 62 days (interquartile range 5-118 days). Survival analysis with Kaplan-Meier curves revealed an increase in the rate of thrombotic events after SARS-CoV-2 compared to non-infected patients (see Figure 1). Mean survival from thrombotic event was 6.1±0.4 months in the COVID-infected group, compared to 6.97±0.04 months in the non-infected group (p Conclusion There is an increased risk of late thrombotic complications in hemodialysis patients after infection with COVID-19. Further studies should evaluate the benefit of prolonged prophylactic anticoagulation in hemodialysis patients after recovery from COVID-19.

Background and Aims Thirst mechanism is essential to maintain an adequate osmolarity and homeostasis. During summer heat waves, there is an increased morbidity and mortality in elderly patients that has led to generally recommend an increase in fluid intake in all elderly patients beyond thirst stimulation, even in those independent patients with free access to water. The aim of this study was to observe the differences in calculated serum osmolarity (cOsm) between young, elderly and very elderly patients who were neither institutionalized nor hospitalized, in different seasons throughout the year. Method We conducted a retrospective cross-sectional study in outpatients between 18-104 years old that had undergone a blood test between July 2019 and January 2020, in which serum osmolarity could be calculated. Patients with serum creatinine above 1.5 mg/dl were excluded. Results The study included 45236 blood samples from 41132 patients, 56.1% were female. 50% of patients were between 18 and 65 years old, 45.4% were between 65 and 85 years old and 4.6% were >85 years old. The mean cOsm in patients between 18-65 years was 288.3 mOsm/kg, compared to 289.8 mOsm/kg in those between 65- 85 years old (p85 years, mean cOsm was 289.4 mOsm/kg. When comparing cOsm between different seasons of the year, cOsm in summer months was about 1 mOsm/kg higher than in autumn-winter (288.9 mOsm/kg vs 287.8 mOsm/kg in young patients, p=0.0001; 290.5 mOsm/kg vs 289.4 mOsm/kg in elderly patients, p=0.0001). In the very elderly (>85 years) the difference was smaller and non-significant (289.6mOsm/kg vs 289.1mOsm/kg). Conclusion Under physiologic conditions, patients >65 years have a slightly higher calculated serum osmolarity than younger patients, nevertheless staying within normal range. These differences only increase in 1 mOsm/kg during the summer months. Therefore, it is not indicated to force an increase in fluid intake in the elderly or very elderly population under physiologic conditions.