Luis Algranati

Cutaneous necrosis by calcific uremic arteriolopathy.

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.

Renal potassium excretion : Comparison between chronic renal disease patients and old people

Senescence and chronic renal failure bring about a progressive glomerular filtration reduction. Moreover, a reduction in glomerular filtration usually modifies the potassium renal excretion. In the present study, we compared the renal potassium handling between old and chronic renal disease populations. Materials and Methods: Fifty-five volunteers were studied, 43 of them were healthy old persons and 12 were predialysis chronic renal disease patients. Exclusion criteria were: presence of altered plasma potassium (Kp), diabetes mellitus, obstructive uropathy, drugs that could alter plasma potassium levels. All volunteers were on a diet with a potassium content around 50 mmol/day (3-day dietary register). We measured potassium, creatinine, urea in plasma and 24 hours urine. We also measured creatinine clearance (CrCl) and fractional excretion of potassium (FEK), and we studied the relationship between these parameters. Statistical analysis was made using Student’s test. Results: Slopes of the correlation curves between CrCl and FEK. Conclusion: The relationship between creatinine clearance and fractional excretion of potassium in old and chronic renal disease groups were different with the excretion of potassium being lower in the elderly.

Plasma erythropoietin levels in the oldest old

Erythropoietin (EPO) regulates erythrocytes production and is synthesized mainly by the kidney. Its production is reduced during chronic renal failure but is not altered by the senescence process in spite of the morphological changes that occur in the kidney. However, there is no information regarding what happens to erythropoietin synthesis during advanced ageing. Thus, we carried out an investigation to determine whether there was any significant difference in plasma erythropoietin between adults, old and very old people. Material and methods: We studied 74 healthy volunteers: 22 adults, 30 old, and 22 very old. None of them were smokers or were suffering from any disease that may intefere with hemoglobin (Hb) levels or with EPO production. Hematocrit, Hb, plasma creatinine and plasma erythropoietin were measured, and creatinine clearance was calculated from serum creatinine using two different formulae. Statistical analysis was performed using ANOVA and Bonferroni tests. Results and conclusion: Among the three groups we found a significant difference in creatinine clearance (p < 0.001), but not in plasma erythropoietin levels; we conclude that normal senescence does not alter plasma erythropoietin levels, even during advanced ageing.

Hyperphosphatemia and nicotinic acid in peritoneal dialysis patients

Dear Editor, Although hyperphosphatemia represents a serious problem in people on dialysis, an optimal treatment for this disorder has not been reported yet. It is known that the main source of phosphorus comes from the diet, and its absorption results from two combined processes: passive paracellular diffusion and luminal sodium-dependent transport against a concentration gradient [1, 2]. It has been reported that nicotinic acid, a B-complex vitamin, can reduce phosphorus absorption by inhibiting the activity of the abovementioned intestinal sodium–phosphorus transporter [1, 3]. Based on this previous information, we performed a protocol treating 18 hyperphosphatemic dialysis patients (three on haemodialysis and 15 on peritoneal dialysis) using a single dose (500 mg) of controlledrelease nicotinic acid. These patients were on this vitamin treatment for 6 months, except for the ones on haemodialysis, in whom nicotinic acid had to be discontinued due to the appearance of severe episodes of flushing. This symptom, caused by vasodilatation, affected characteristically the upper part of their body: face, neck, and chest. Conversely, these episodes of flushing were practically absent in peritoneal dialysis patients. This difference in adverse reaction to nicotinic acid between the groups could be explained because only the peritoneal dialysis patients were on 200 mg of aspirin, a drug that can reduce the nicotinic-acid-induced flushing [1]. No other side effects secondary to this vitamin, such as thrombocytopenia, hepatic enzymes, or serum glucose elevation, were documented. After 6 months of treatment, we found no statistically significant difference between the initial serum phosphorus levels and postnicotinic treatment levels (Table 1). Thus, we concluded that, at least in our experience, a single dose (500 mg) of controlled-release nicotinic acid was not effective in reducing hyperphosphatemia in peritoneal dialysis patients.

Creatinine clearance with cimetidine in the elderly: response to Dr. Chia-Ter Chao

We thank Dr. Chia-Ter Chao for his comments about our paper. In responding, we will take the opportunity to correct a mistake. Unfortunately, in the paper, we reported the wrong dose of cimetidine: Instead of 800 mg OD (once per day), it should have been written 800 mg BID (twice a day), a dose most recommended in the literature for achieving a complete creatinine secretion inhibition (we referenced these articles in our original paper). We thank Dr. Chao for pointing out this error and giving us the opportunity to correct it [1–3]. Regarding Dr. Chao0s comment on the accuracy of the method used for evaluating the renal reserve, we would like to emphasize that to evaluate this physiological variable we obtained the DELTA value between a peak GFR value and a basal one; thus, obtained DELTA value will be an accurate representation of the magnitude of GFR increase, independently of the accuracy of the applied method for measuring it. Regarding Dr. Chao0s concern about the accuracy of urine volume measurement, we would like to clarify that all the volunteers had a normal bladder voiding (presence of urine retention was one of the exclusion criteria evaluated before the study), and additionally, their urine residual volume was checked by bladder ultrasound after each micturition (this is mandatory when a timed clearance is evaluated). We agree with Dr. Chao that more research is needed in order to know how the aged kidney handles not only creatinine but also cimetidine.

Erratum to: Renal creatinine handling in very old patients with chronic renal disease

Erratum to: Int Urol NephrolDOI 10.1007/s11255-010-9886-5The original version of our paper unfortunatelycontained a mistake. We reported the wrong dose ofcimetidine: instead of 800 mg OD (once per day) itshould have been written 800 mg BID (twice a day),a dose most recommended in the literature forachieving a complete creatinine secretion inhibition.