Impact of Serum Magnesium Levels on Kidney and Cardiovascular Prognosis and Mortality in CKD Patients.

INTRODUCTION: In the general population, hypomagnesemia has been associated with cardiovascular events and hypermagnesemia with overall mortality. In chronic kidney disease (CKD) the evidence is not so strong. The objective of our study was to investigate the relationship between serum magnesium (SMg) concentration and cardiovascular morbidity and mortality, all-cause mortality, and the progression to kidney failure in a population with CKD. METHODS: Observational study of a cohort of 746 patients with CKD. Baseline characteristics and analytical profile were collected at the first visit, and patients were followed for a mean of 42.6 months. RESULTS: A cohort of 746 patients were analyzed, age 70 ± 13 years, 62.9% were male, 45.2% had CKD grade 3, and 35.9% grade 4. The mean SMg concentration was 2.09 ± 0.33 mg/dL, with a close correlation between SMg concentration and serum creatinine, phosphorus, and intact parathyroid hormone (iPTH) values. Use of calcitriol was associated with higher SMg (SMgH) concentration, while calcium supplements and proton pump inhibitors (PPIs) were associated with lower SMg concentration. For risk of cardiovascular events, patients with hypermagnesemia had an overall higher risk on a crude analysis (Log Rank 4.83, P = .28) and adjusted analysis (HR = 1.34, CI 1.02-1.77, P = .037). For risk of all-cause mortality, patients with hypermagnesemia had an overall higher risk on crude analysis (Log Rank 13.11, P > .001) and adjusted analysis (HR = 1.5424, IC = 1.002-2.319, P = .049). After performing a propensity score matching for SMg concentration, we achieved two comparable groups of 287 patients, finding again higher all-cause mortality in the hypermagnesemia group (LogRank 15.147, P < .001), that persisted in the Cox model adjusted for calcium, phosphorus, and iPTH. No association was found between SMg concentration and initiation of kidney replacement therapy (KRT). CONCLUSIONS: Magnesium concentration increases with decreasing kidney function. Hypermagnesemia predicts cardiovascular events and all-cause mortality in this same population. Thus, magnesium supplementation should be used with caution in these patients.

Efficacy and Safety of CT-Guided Kidney Biopsy for the Diagnosis of Glomerular Diseases in Complicated Patients.

INTRODUCTION: Kidney biopsy is the cornerstone for the diagnosis of glomerular diseases and to guide treatment. Percutaneous ultrasound-guided kidney biopsy is currently the gold standard to obtain cortical specimens. However, in cases where ultrasound-guided kidney biopsy is not deemed safe (obese patients, deep kidneys, or kidneys with a complicated anatomy), CT-guided kidney biopsy could be a convenient alternative to obtain renal tissue samples. The aim of this study was to describe the diagnostic yield and complications of CT-guided kidney biopsies in patients with glomerular diseases that were previously discarded for ultrasound-guided kidney biopsy. MATERIAL AND METHODS: We performed a retrospective, single-center, observational study including patients who underwent CT-guided native kidney biopsies in our center after being contraindicated for ultrasound-guided biopsy. Patients' records were reviewed retrieving baseline characteristics and pre-biopsy clinical, laboratory parameters and concomitant medication. The biopsy needle gauge, site of puncture, and number of needle passes were recorded. The diagnostic yield was evaluated by the number of glomeruli obtained, the rate of specimens that were adequate to reach diagnosis, and the number of biopsies that had to be repeated. Complications were defined as minor (hypotension, hematoma) and major (arteriovenous fistulae, major bleeding requiring embolization, or nephrectomy). The diagnostic yield and complications were compared to ultrasound-guided native kidney biopsies performed during the same period. RESULTS: 56 CT-guided native kidney biopsies were performed during the study period. The number of glomeruli obtained per patient was 11.5 ± 6.3, which was inferior to that obtained from ultrasound-guided biopsies (14.08 ± 8.47, p < 0.05). However, the rate of specimens that were adequate to reach a diagnosis was similar (92.9% vs. 90.8%, p = 0.437). The number of needle passes was higher in CT-guided kidney biopsies (2.0 ± 0.7 vs. 1.7 ± 0.5, p < 0.05), as well as the incidence of post-biopsy perirenal asymptomatic hematomas (66.1% vs. 24.5%, p < 0.01). There were no significant differences in other post-biopsy minor complications (1.8% vs. 2.5%, p = 0.621). There were no major complications after CT-guided kidney biopsies. CONCLUSIONS: CT-guided percutaneous kidney biopsy is a valid alternative for the diagnosis of glomerular diseases in patients with special characteristics such as obesity or deep kidneys that contraindicate ultrasound-guided biopsy. In this population, CT-guided kidney biopsies are safe and provide a high diagnostic yield, reaching a diagnosis in >90% of patients that had been previously discarded for ultrasound-guided biopsy.