Transtubular potassium concentration gradient (TTKG) is an index of potassium secretory activity in the distal tubule. Since water reabsorption takes place in the distal tubule as well, urine potassium concentration is a less accurate index evaluating distal K+ secretion because the effect of water is not taken into account on urine potassium concentrations. Potassium secretion and water reabsorption are strongly related to age and renal function. As a consequence, TTKG would be altered in both elderly individuals, as well as in patients with chronic renal failure (CRF). The aim of this study was to assess and compare TTKG in these two groups.Patients & Methods A total of 55 individuals were studied, 12 of them were patients with CRF and 43 healthy elderly subjects with normal renal function. Informed consent was obtained from all patients. Patients with diabetes mellitus, cardiac failure, cirrhosis, obstructive uropathy, hyperkalemia, hypokalemia, or taking any medication that could alter the potassium balance were excluded from the study. All subjects were on a diet containing 50 mmol of potassium intake daily (documented by a three-day dietary record). Plasma potassium, creatinine, urea, glucose and osmolality were measured in all as well. 24 h creatinine clearance (CrCl ) and TTKG were calculated. Statistical analysis was made using Student's t-test. Results TTKG was significantly lower in the elderly group (4.2-1.9 vs 6.2-1.8 , P 0.005)Both groups had a significantly lower TTKG when compared to healthy young people (8-2). Plasma and urine potassium levels, as well as plasma osmolality were similar in the two groups. Only urine osmolality was lower in the CRF group (382-141 vs. 514-180, P=0.01) Conclusion Both old age and renal impairment lead to a reduced TTKG in comparison with young healthy people. Furthermore, TTKG is significantly lower in elderly healthy subjects compared to patients with CRF.

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Furosemide test showed a significantly lower average post-furosemide FE of potassium value, delayed post-furosemide peak FE of Na, K and Cl and a hormonal pattern of aldosterone resistance in very old people.

Background Calcific uremic arteriolopathy is a rare and serious disorder characterized by systemic medial calcification of the arteries and tissue ischemia. Most often it is found in patients with chronic renal failure on dialysis and in renal transplant recipients with secondary hyperparathyroidism. MethodsWe report six patients with end-stage renal disease [five on hemodialysis (one with a nonfunctioning renal graft) and one on peritoneal dialysis] who developed painful livedo reticularis and skin necrosis of the limbs. All had secondary hyperparathyroidism and elevated calcium-phosphorus product. Our patients presented with the following clinical features: white race (six patients), hypoalbuminemia (three patients), diabetes (one patient), and obesity (four patients). ResultsSubtotal parathyroidectomy was performed in three cases. Despite this procedure, two patients died; one patient survived and his lesions healed. One patient was treated with aggressive wound care and hemodialysis (with low dialysate calcium concentration and Renagel phosphorus binders) and one patient received only local wound care, both with improvement of their lesions. In one case, no therapy was performed because the patient died immediately after diagnosis. ConclusionsThe three patients who survived (Cases 4, 5 and 6) had distal lesions, normal serum albumin, and an early diagnosis. There was a relationship between the outcome of the patients and these factors, rather than the type of treatment received.

Background. The impact of renal transplantation (RT) in the elderly with many comorbid conditions is a matter of concern. The aim of our study was to assess the impact of RT on the survival of patients older than 60 years compared with those remaining on the waiting list (WL) according to their comorbidities. Methods. In this multicentric observational retrospective cohort study, we included all patients older than 60 years old admitted on the WL from 01 January 2006 to 31 December 2016. The Charlson comorbidity index (CCI) score was calculated for each patient at inclusion on the WL. Kidney donor risk index was used to assess donor characteristics. Results. One thousand and thirty-six patients were included on the WL of which 371 (36%) received an RT during a median follow-up period of 2.5 (1.4–4.1) years. Patient survival was higher after RT compared to patients remaining on the WL, 87%, 80%, and 72% versus 87%, 55%, and 30% at 1, 3, and 5 years, respectively. After RT survival at 5 years was 37% higher for patients with CCI ≥ 3, and 46% higher in those with CCI < 3, compared with patients remaining on the WL. On univariate and multivariate analysis, patient survival was independently associated with a CCI of ≥3 (hazard ratio 1.62; confidence interval 1.09-2.41; P < 0.02) and the use of calcineurin-based therapy maintenance therapy (hazard ratio 0.53; confidence interval 0.34-0.82; P < 0.004). Conclusions. Our study showed that RT improved survival in patients older than 60 years even those with high comorbidities. The survival after transplantation was also affected by comorbidities.