Entering into 2.0 cystinuric management with a medical digital tool to monitor urine pH: a prospective, randomized study

BACKGROUND AND OBJECTIVES

Individuals with cystinuria can experiment recurrent lithiasis events due to the relative insolubility of cystine at physiological urine pH, resulting in renal function decline. The Lit-Control® pH Meter is a medical device that accurately allows urine pH self-monitoring. The main objective of this study was to compare the usability of the Lit-Control® pH Meter with the reactive strips for self-monitoring of urinary pH at home by patients with cystinuria, and their overall satisfaction with each tool.

PATIENTS AND METHODS

We included 28 patients (9 females and 19 males, age 19-76 years), who were randomly assigned to monitor their urine pH with reactive strips (n = 17) or the Lit-Control® pH-meter (n = 11).

RESULTS

After six months of use, the satisfaction with the two methods was similarly high, but the patients rated (0-10 scale) the pH meter better in terms of ease of learning (mean ± SD, 8.11 ± 0.60 vs. 7.06 ± 1.18; P = 0.038), ease to prepare (8.22 ± 0.67 vs. 7.25 ± 1.18; P = 0.034), and ease of use (8.22 ± 0.67 vs. 7.25 ± 1.39; P = 0.062). Overall, patients did not reach the alkalinization goals (pH between 7.0 and 8.0).

CONCLUSIONS

The Lit-Control® pH Meter demonstrated to be an easy-to-use device that can facilitate urinary pH control by cystinuric patients. A prospective study is warranted to assess the correlation between urine pH monitoring, a treat to target approach, and the recurrence of cystine stones.

Update of the SFMV (French society of vascular medicine) guidelines on the conditions and safety measures necessary for thermal ablation of the saphenous veins and proposals for unresolved issues

Venous insufficiency is a very common disease affecting about 25% of the French population (if we combine all stages of its progression). It is a complex disease and its aetiology has not yet been fully elucidated. Some of its causes are well known, such as valvular dysfunction, vein wall defect, and the suctioning effect common to all varicose veins. These factors are generally associated and together lead to dysfunction of one or more of the saphenous veins. Saphenous vein dysfunction is revealed by ultrasound scan, a reflux lasting more than 0.5 seconds indicating venous incompetence. The potential consequences of saphenous vein dysfunction over time include: symptoms (heaviness, swellings, restlessness, cramps, itching of the lower limbs), acute complications (superficial venous thrombosis, varicose bleeding), chronic complications (changes in skin texture and colour, stasis dermatitis, eczema, vein atresia, leg ulcer), and appearance of unaesthetic varicose veins. It is not possible to repair an incompetent saphenous vein. The only therapeutic options at present are ultrasound-guided foam sclerotherapy, physical removal of the vein (saphenous stripping), or its thermal ablation (by laser or radiofrequency treatment), the latter strategy having now become the gold standard as recommended by international guidelines. Recommendations concerning thermal ablation of saphenous veins were published in 2014 by the Société française de médecine vasculaire. Our society has now decided to update these recommendations, taking this opportunity to discuss unresolved issues and issues not addressed in the original guidelines. Thermal ablation of an incompetent saphenous vein consists in destroying this by means of a heating element introduced via ultrasound-guided venous puncture. The heating element comprises either a laser fibre or a radiofrequency catheter. The practitioner must provide the patient with full information about the procedure and obtain his/her consent prior to its implementation. The checklist concerning the interventional procedure issued by the HAS should be validated for each patient (see the appended document).

[A new approach to urinary stone analysis according to the combination of the components: experience with 7949 cases]

OBJECTIVE

To evaluate a new approach to urinary stone analysis according to the combination of the components.

MATERIALS AND METHODS

A total of 7949 stones were analysed and their main components and combinations of components were classified according to gender and age. Statistical analysis was performed using the chi-square test.

RESULTS

Calcium oxalate monohydrate (COM) was the most frequent component in both males (39%) and females (37.4%), followed by calcium oxalate dihydrate (COD) (28%) and uric acid (URI) (14.6%) in males and by phosphate (PHO) (22.2%) and COD (19.6%) in females (p=0.0001). In young people, COD and PHO were the most frequent components in males and females respectively (p=0.0001). In older patients, COM and URI (in that order) were the most frequent components in both genders (p=0.0001). COM is oxalate dependent and is related to diets with a high oxalate content and low water intake. The progressive increase in URI with age is related mainly to overweight and metabolic syndrome. Regarding the combinations of components, the most frequent were COM (26.3%), COD+Apatite (APA) (15.5%), URI (10%) and COM+COD (7.5%) (p=0.0001).

CONCLUSIONS

This study reports not only the composition of stones but also the main combinations of components according to age and gender. The results prove that stone composition is related to the changes in dietary habits and life-style that occur over a lifetime, and the morphological structure of stones is indicative of the aetiopathogenic mechanisms.

TRPC6 mutational analysis in a large cohort of patients with focal segmental glomerulosclerosis

BACKGROUND

Mutations in the TRPC6 gene have been reported in six families with adult-onset (17-57 years) autosomal dominant focal segmental glomerulosclerosis (FSGS). Electrophysiology studies confirmed augmented calcium influx only in three of these six TRPC6 mutations. To date, the role of TRPC6 in childhood and adulthood non-familial forms is unknown.

METHODS

TRPC6 mutation analysis was performed by direct sequencing in 130 Spanish patients from 115 unrelated families with FSGS. An in silico scoring matrix was developed to evaluate the pathogenicity of amino acid substitutions, by using the bio-physical and bio-chemical differences between wild-type and mutant amino acid, the evolutionary conservation of the amino acid residue in orthologues, homologues and defined domains, with the addition of contextual information.

RESULTS

Three new missense substitutions were identified in two clinically non-familial cases and in one familial case. The analysis by means of this scoring system allowed us to classify these variants as likely pathogenic mutations. One of them was detected in a female patient with unusual clinical features: mesangial proliferative FSGS in childhood (7 years) and partial response to immunosupressive therapy (CsA + MMF). Asymptomatic carriers of this likely mutation were found within her family.

CONCLUSIONS

We describe for the first time TRPC6 mutations in children and adults with non-familial FSGS. It seems that TRPC6 is a gene with a very variable penetrance that may contribute to glomerular diseases in a multi-hit setting.

[Tables estimating glomerular filtration rate from plasma creatinine]

Chronic kidney disease (CKD) and its related complications have become an important health and social problem. Very expensive resources are required in end-stage renal disease, and both complications of CKD as well as the important associated cardiovascular risk demand for interventions long before renal substitution therapies are needed. Thus, early diagnosis of CKD is currently considered of paramount importance, and it is based essentially upon the estimation of the glomerular filtration rate by formulae such as the abbreviated equation of the MDRD study. Nevertheless, in spite of international published recommendations, an automatic calculation to estimate the glomerular filtration rate (GFR) from serum creatinine is not reported by most laboratories yet and the need for creatinine assay standardisation is far from being implemented. Thus, we have designed some tables to show the creatinine value corresponding to different GFR for ages between 20 and 90 y/o, at 5 years intervals and in both sexes with both the MDRD-4 and MDRD-IDMS equations (Modification of Diet in Renal Disease-Isotope Dilution Mass Spectrometry). Moreover, we have created a global table including an estimation of GFR from plasma creatinine, age and sex by the MDRD-IDMS formula, the recommended for those laboratories which measure serum creatinine with assays aligned to the reference method. These tables aim to increase the awareness of the different assays for serum creatinine and to facilitate the diagnosis of CKD converting serum creatinine into GFR. This action should allow not only the early detection but also the possibility to establish the appropriate medical actions recommended after CKD detection.

A missense mutation in the chloride/proton ClC-5 antiporter gene results in increased expression of an alternative mRNA form that lacks exons 10 and 11. Identification of seven new CLCN5 mutations in patients with Dent’s disease

Mutations in the voltage-gated chloride/proton antiporter ClC-5 gene, CLCN5, are associated with Dent's disease, an X-linked renal tubulopathy. Our interest is to identify and characterize disease-causing CLCN5 mutations, especially those that alter the splicing of the pre-mRNA. We analyzed the CLCN5 gene from nine unrelated Spanish Dent's disease patients and their relatives by DNA sequencing. Pre-mRNA splicing analysis was performed by RT-PCR. Seven new mutations were identified, consisting of three missense mutations (C219R, F273L, and W547G), one splice-site mutation (IVS-2A > G), one deletion (976delG), and two non-sense mutations (Y140X and W314X). We found that missense mutation W547G also led to increased expression of a new alternative isoform lacking exons 10 and 11 that was expressed in several human tissues. In addition, we describe another novel CLCN5 splicing variant lacking exon 11 alone, which was expressed only in human skeletal muscle. We conclude that missense mutation W547G can also alter the expression levels of a CLCN5 mRNA splicing variant. This type of mutation has not been previously described in the CLCN5 gene. Our results support the importance of a routine analysis at the pre-mRNA level of mutations that are commonly assumed to cause single amino acids alterations.

[Cystinuria and cystine kidney lithiasis. Diagnosis and therapeutic approach]

OBJECTIVE

Cystine renal stone is the only clinical consequence of cystinuria, an autosomal recessive hereditary disease that affects an average of 1 out of 7,000 newborns, and whose geographical distribution varies significantly. The diagnosis and treatment of this condition is reviewed in the light of the advances in genetics and molecular biology.

METHODS

The evolution of current knowledge about this disease is reviewed.

RESULTS/CONCLUSIONS

The advances over the last 8 years have led to the characterization, at the present time, of two genes responsible for this disease, which demonstrates its polygenic origin. By phenotype, cystinuria can be classified into two types: type 1 and non-type 1. Both types show genetic and biochemical, but not clinical differences. From the therapeutic viewpoint, the main objective is to eliminate existing calculi and, above all, prevent recurrence by acting on the pathophysiologic mechanisms of renal cystine. Experience shows that despite the correct use of our current therapeutic armamentarium and the application of the general guidelines discussed in this paper, some cystinuric patients still maintain an important stone-forming activity. Patient clinical evaluation and a genetic study of both patient and family will be decisive for phenotyping.