Tacrolimus has a narrow therapeutic window; a whole-blood trough target concentration of between 5 and 8 ng/mL is considered a safe level for stable kidney transplant recipients. Tacrolimus serum levels must be closely monitored to obtain a balance between maximizing efficacy and minimizing dose-related toxic effects. Currently, there is no specific tacrolimus toxicity biomarker except a graft biopsy. Our study aimed to identify specific serum metabolites correlated with tacrolinemia levels using serum high-precision liquid chromatography–mass spectrometry and standard laboratory evaluation. Three machine learning algorithms were used (Naïve Bayes, logistic regression, and Random Forest) in 19 patients with high tacrolinemia (8 ng/mL) and 23 patients with low tacrolinemia (5 ng/mL). Using a selected panel of five lipid metabolites (phosphatidylserine, phosphatidylglycerol, phosphatidylethanolamine, arachidyl palmitoleate, and ceramide), Mg²⁺, and uric acid, all three machine learning algorithms yielded excellent classification accuracies between the two groups. The highest classification accuracy was obtained by Naïve Bayes, with an area under the curve of 0.799 and a classification accuracy of 0.756. Our results show that using our identified five lipid metabolites combined with Mg²⁺ and uric acid serum levels may provide a novel tool for diagnosing tacrolimus toxicity in kidney transplant recipients. Further validation with targeted MS and biopsy-proven TAC toxicity is needed.

Renal cell carcinoma (RCC) accounts for 2–3% of all adult malignant neoplasms and is even rarer in patients under 45 years old. Clear-cell carcinoma represents most of the pathological subtypes. Our study aimed to investigate the association between preoperative computer tomography imagistic evaluation and histopathological diagnosis of renal tumors in young adults. Patients younger than 45 years old with renal tumors who were referred for medical treatment at the Clinical Institute of Urology and Renal Transplantation Cluj-Napoca from 2012 to 2019 were considered eligible for the study. Medical charts were retrospectively reviewed, and patients with complete data regarding preoperative diagnostic, histopathological evaluation, and follow-up data, regardless of gender, were included in the study. Sixteen patients younger than 45 years fulfilled all the inclusion criteria and were evaluated. With two exceptions, the evaluated patients were in a T1 and T2 stage, with no vascular invasion or of the adjacent organs. Two-thirds of our patients had a clear-cell renal cell carcinoma. None of our patients fitted in the low complexity surgery category of the R.E.N.A.L. Nephrometry Score and 37.5% of them benefited from partial nephrectomy. Half of the suppositions made based on imaging were concordant with the histopathology report. Fifteen of the patients showed no recurrence during the respective follow-up interval. Computer tomography imaging reports showed on our sample a higher concordance with the histopathological report in the more common subtypes (namely Renal Clear Cell RCC), with typical appearances.