Introduction Although most patients recover within several weeks after acute COVID‐19, some of them develop long‐lasting clinical symptoms. Renal transplant recipients have an increased mortality risk from COVID‐19. We aimed to describe complications occurring after COVID‐19 in this group of patients. Methods A prospective single‐center cohort study was conducted at University Hospital Centre Zagreb. Patients with two negative reverse transcriptase‐polymerase chain reaction (RT‐PCR) tests for SARS‐CoV‐2 after COVID‐19 were eligible for further follow‐up at our outpatient clinic. They underwent detailed clinical and laboratory assessments. The primary outcome was the development of complications after COVID‐19. Results Only 11.53% of renal transplant recipients who survived acute COVID‐19 were symptomless and free from new‐onset laboratory abnormalities during the median follow‐up of 64 days (range: 50–76 days). Three patients died from sepsis after discharge from the hospital. In 47 patients (45.2%), clinical complications were present, while 74 patients (71.2%) had one or more laboratory abnormalities. The most common clinical complications included shortness of breath (19.2%), tiredness (11.5%), peripheral neuropathy (7.7%), self‐reported cognitive impairments (5.7%), and dry cough (7.7%). Most common laboratory abnormalities included shortened activated partial thromboplastin time (50%), elevated D‐dimers (36.5%), elevated fibrinogen (30.16%), and hypogammaglobulinemia (24%). Positive RT‐PCR for cytomegalovirus (8.7%), Epstein–Barr virus (26%), or BK virus (16.3%). Multivariate analysis identified the history of diabetes mellitus and eGFR CKD‐EPI as predictors for the development of post‐COVID clinical complications. Six months after acute COVID‐19, elevated D‐dimers persisted with normalization of other laboratory parameters. Twenty‐nine patients were hospitalized, mostly with several concomitant problems. However, initially reported clinical problems gradually improved in the majority of patients. Conclusion Post‐COVID‐19 clinical and laboratory complications are frequent in the renal transplant population, in some of them associated with significant morbidity. All patients recovered from acute COVID‐19 should undergo long‐term monitoring for evaluation and treatment of complications.

Current knowledge on histopathological changes occurring after COVID‐19 in transplanted kidneys is limited. Herein, we present renal allograft pathology findings in patients recovered from COVID‐19. Six patients underwent indication biopsy, and one required allograft nephrectomy after acute COVID‐19. Demographic data, clinical characteristics, and laboratory findings were recorded. The histopathological analysis included light microscopy, immunostaining, and electron microscopy. Five patients were hospitalized for acute COVID‐19, and all were diagnosed with imaging‐confirmed pneumonia, one requiring mechanical ventilation, and two requiring dialysis. Two patients had mild form. Histopathologic examination of renal allograft specimens revealed collapsing, perihilar, tip‐lesion and secondary FSGS in one patient each. One patient had borderline acute cellular rejection, and two had chronic antibody‐mediated rejection. Histopathologic changes of glomerular tufts were accompanied by acute tubular injury in four patients. None of our patients had signs of viral inclusions in kidney cells. One patient died and one remained dialysis‐dependent after the good initial response to treatment. Patients with collapsing and perihilar FSGS had further progression of their chronic allograft nephropathy still without need for dialysis. In conclusion, diverse kidney pathology may be found in SARS‐CoV‐2–infected renal transplant patients. It seems that viral infection may affect the immune system with triggering of glomerular diseases, while the acute tubular injury is of multifactorial etiology. Direct viral effect is less likely.

Background/Aims: There is a growing body of evidence that the long-term hemodialysis (HD) treatment leads to disturbances of carnitine homeostasis but the results of L-carnitine supplementation in HD patients have been conflicting. In the present prospective study, we investigated the effectiveness of intravenous L-carnitine in mitigating dialysis-related protein-energy wasting (PEW) based on pre-treatment albumin levels. Methods: Fifty patients (46% male, mean age 63±18.28 years, HD vintage 37.5 (7-288) months) received 1 g L-carnitine intravenously at the end of every HD session for 12 months. Clinical data were obtained from the medical records and charts. Intradialytic hypotension periods (defined as a decrease of systolic blood pressure by ≥ 20 mmHg) were recorded. Dietary habits were evaluated using a self-administered questionnaire prior to L-carnitine supplementation. Laboratory parameters were measured prior to the supplementation and controlled in 6-months intervals. Anthropometric measurements were performed prior to HD session, including „dry“ body weight and height, body mass index (BMI), and body composition analysis using bioimpedance spectroscopy. Malnutrition-inflammation score (MIS) was used as a scoring system representing the severity of PEW and an indicator of general functional capacity. Results: A significant increase in total cholesterol, predominantly on the account of LDL was found (p=0.005). Simultaneously, HDL decreased (p=0.001) while triglyceride levels remained unchanged. Although the rise in serum prealbumin could be observed, lean tissue index (LTI) decreased and fat tissue index (FTI) increased which resulted in reduction of the LTI/FTI ratio (p=0.002). When divided into two groups according to the pre-treatment albumin values (< 35 g/L or ≥35 g/L), patients from the higher albumin group showed significant increase in prealbumin (p=0.005), and improved MIS (p=0.03). Multivariate regression analysis showed that higher FTI after introduction of L-carnitine led to greater hemodynamic stability (OR 1.709, 95% CI 1.006-2.905, p=0.048). As there was no differences in HD treatment characteristics, primery kidney disease or residual diuresis we could conclude that positive energy balance (with an increase in prealbumin and FTI) eventually led to better hemodynamic stability. Conclusion: Our results show significant effects of L-carnitine supplementation on lipid metabolism. Further clinical trials, as well as experimental research are needed to define the role of lipid metabolism in CKD population. Significant benefits of L-carnitine supplementation in patients with better initial serum albumin levels suggest that this therapy should not be restricted to patients with the worst nutritional and overall status.

Although glucocorticoid therapy is considered to be the main pathogenic factor, a consistent body of evidence suggests that other immunosuppressants might also play an important role in the development of the post-transplant renal osteopathy (PRO) through their pleiotropic pharmacological effects. Glucocorticoids seem to induce osteoclasts' activity suppressing the osteoblasts while data regarding other immunosuppressive drugs are still controversial. Mycophenolate mofetil and azathioprine appear to be neutral regarding the bone metabolism. However, the study analyzing any independent effect of antimetabolites on bone turnover has not been conducted yet. Calcineurin inhibitors (CNIs) induce trabecular bone loss in rodent, with contradictory results in renal transplant recipients. Suppression of vitamin D receptor is probably the underlying mechanism of renal calcium wasting in renal transplant recipients receiving CNI. In spite of an increased 1,25(OH)2 vitamin D level, the kidney is not able to reserve calcium, suggesting a role of vitamin D resistance that may be related to bone loss. More efforts should be invested to determine the role of CNI in PRO. In particular, data regarding the role of mammalian target of rapamycin inhibitors (mTORi), such as sirolimus and everolimus, in the PRO development are still controversial. Rapamycin markedly decreases bone longitudinal growth as well as callus formation in experimental models, but also lowers the rate of bone resorption markers and glomerular filtration in clinical studies. Everolimus potently inhibits primary mouse and human osteoclast activity as well as the osteoclast differentiation. It also prevents the ovariectomy-induced loss of cancellous bone by 60 %, an effect predominantly associated with a decreased osteoclast-mediated bone resorption, resulting in a partial preservation of the cancellous bone. At present, there is no clinical study analyzing the effect of everolimus on bone turnover in renal transplant recipients or comparing sirolimus versus everolimus impact on bone, so only general conclusions could be drawn. Hence, the use of mTORi might be useful in patients with PRO due to their possible potential to inhibit osteoclast activity which might lead to a decreased rate of bone resorption. In addition, it should be also emphasized that they might inhibit osteoblast activity which may lead to a decreased bone formation and adynamic bone disease. Further studies are urgently needed to solve these important clinical dilemmas.