[A diagnostic-therapeutic pathway for patients with kidney stone disease: 2020 update]

The natural history of urinary kidney stone disease includes the risk of relapses and can be associated with the risk of chronic kidney disease, bone and cardiovascular disease. For this reason, a wide clinical-metabolic assessment of the kidney stone patient is of great importance since the first presentation of the stone, to set an appropriate preventive treatment. The proposed diagnostic-therapeutic pathway includes a careful medical history, in order to highlight a secondary kidney stone disease and the main risk factors for kidney stones, chronic renal disease, or cardiovascular and bone disease; a metabolic evaluation on multiple levels, according to the severity of the disease, and the presence or absence of risk factors, and appropriate instrumental investigations. Thus, the information collected makes it possible to set a preventive treatment consisting of general rules and, if necessary, specific pharmacological or nutritional interventions. This paper has been prepared by the Italian Multidisciplinary Study Group for Kidney Stone Disease, and it is addressed to the several professional figures involved in the management of patients suffering from nephrolithiasis, from the emergency doctor to the general practitioner, urologist, nephrologist, radiologist, and dietician. A diagnostic-therapeutic pathway for patients with kidney stone disease was first published on this Journal in 2010. The present contribution aims at amending and updating the article published exactly ten years ago, to serve as an easy-to-use reference and to guide good clinical practice in this field.

Anthropometric variables, physical activity and dietary intakes of patients with uric acid nephrolithiasis

To evaluate anthropometric variables, energy expenditure by physical activity and nutrient intake of uric acid stone formers (UA-RSFs) compared to non-forming subjects (C). The study included 33 consecutive male patients with a diagnosis of "pure" stones of anhydrous uric acid at infrared spectroscopy and 49 male control subjects with no history of urinary stones. A personal interview was conducted including questionnaires for physical activity and dietary intakes. Anthropometric parametric and blood pressure were measured. Mean age, weight, height, waist circumference, body mass index, systolic and diastolic blood pressure values, dietary energy, carbohydrate intake, lipid intake, dietary acid load, time spent for different physical activities and total energy expenditure for physical activity were not different in UA-RSFs with respect to C. Mean dietary protein (76.2 ± 19.6 vs 65.4 ± 14.7 g/day, P = 0.006) and ethanol intake (10.4 ± 8.8 vs 4.1 ± 8.6, P = 0.002) were higher in UA-RSFs than in C. History of renal disease, heart disease and treatment with thiazides or allopurinol were more frequent and mean serum glucose and triglycerides (104 ± 12 vs 97 ± 11 mg/dl, P = 0.043) (172 ± 77 vs 123 ± 52 mg/dl, P = 0.023) were higher in UA-RSFs. Metabolic syndrome was more frequent in UA-RSFs (57% vs 39%) but not significant (p = 0.09). Increased dietary animal protein (and ethanol) intake can act as co-factors for uric acid stone formation although a more complex and not fully elucidated metabolic background can have an even more crucial role in the pathogenesis of this disease even in the absence of overweight.

A preliminary survey of practice patterns across several European kidney stone centers and a call for action in developing shared practice

Currently an evidence-based approach to nephrolithiasis is hampered by a lack of randomized controlled trials. Thus, there is a need for common platforms for data sharing and recruitment of patients to interventional studies. A first step in achieving this objective would be to share practice methods and protocols for subsequent standardization in what is still a heterogeneous clinical field. Here, we present the results of a pilot survey performed across 24 European clinical kidney stone centers. The survey was distributed by a voluntary online questionnaire circulated between June 2017 and January 2018. About 46% of centers reported seeing on average 20 or more patients per month. Only 21% adopted any formal referral criteria. Centers were relatively heterogeneous in respect of the definition of an incident stone event. The majority (71%) adopted a formal follow-up scheme; of these, 65% included a follow-up visit at 3 and 12 months, and 41% more than 12 months. In 79% of centers some kind of imaging was performed systematically. 75% of all centers performed laboratory analyses on blood samples at baseline and during follow-up. All centers performed laboratory analyses on 24-h urine samples, the majority (96%) at baseline and during follow-up. There was good correspondence across centers for analyses performed on 24-h urine samples, although the methods of 24-h urine collection and analysis were relatively heterogeneous. Our survey among 24 European stone centers highlights areas of homogeneity and heterogeneity that will be investigated further. Our aim is the creation of a European network of stone centers sharing practice patterns and hosting a common database for research and guidance in clinical care.

Defining metabolic activity of nephrolithiasis - Appropriate evaluation and follow-up of stone formers

Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3-6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1-2 years.

The Risk of Chronic Kidney Disease Associated with Urolithiasis and its Urological Treatments: A Review

PURPOSE

Urolithiasis can impair kidney function. This literature review focuses on the risk of kidney impairment in stone formers, the specific conditions associated with this risk and the impact of urological surgery.

MATERIALS AND METHODS

The PubMed® and Embase® databases were searched for publications on urolithiasis, its treatment, and the risk of chronic kidney disease, end stage renal disease and nephrectomy in stone formers.

RESULTS

In general, renal stone formers have twice the risk of chronic kidney disease or end stage renal disease, and for female and overweight stone formers the risk is even higher. Patients with frequent urinary tract infections, struvite stones, urinary malformations and diversions, malabsorptive bowel conditions and some monogenic disorders are at high risk for chronic kidney disease/end stage renal disease. Shock wave lithotripsy or minimally invasive urological interventions for stones do not adversely affect renal function. Declines in renal function generally occur in patients with preexisting chronic kidney disease or a large stone burden requiring repeated and/or complex surgery.

CONCLUSIONS

Although the effect size is modest, urolithiasis may cause chronic kidney disease and, thus, it is mandatory to assess patients with renal stones for the risk of chronic kidney disease/end stage renal disease. We suggest that all guidelines dealing with renal stone disease should include assessment of this risk.

Metabolic diagnosis and medical prevention of calcium nephrolithiasis and its systemic manifestations: a consensus statement

BACKGROUND

Recently published guidelines on the medical management of renal stone disease did not address relevant topics in the field of idiopathic calcium nephrolithiasis, which are important also for clinical research.

DESIGN

A steering committee identified 27 questions, which were proposed to a faculty of 44 experts in nephrolithiasis and allied fields. A systematic review of the literature was conducted and 5216 potentially relevant articles were selected; from these, 407 articles were deemed to provide useful scientific information. The Faculty, divided into working groups, analysed the relevant literature. Preliminary statements developed by each group were exhaustively discussed in plenary sessions and approved.

RESULTS

Statements were developed to inform clinicians on the identification of secondary forms of calcium nephrolithiasis and systemic complications; on the definition of idiopathic calcium nephrolithiasis; on the use of urinary tests of crystallization and of surgical observations during stone treatment in the management of these patients; on the identification of patients warranting preventive measures; on the role of fluid and nutritional measures and of drugs to prevent recurrent episodes of stones; and finally, on the cooperation between the urologist and nephrologist in the renal stone patients.

CONCLUSIONS

This document has addressed idiopathic calcium nephrolithiasis from the perspective of a disease that can associate with systemic disorders, emphasizing the interplay needed between urologists and nephrologists. It is complementary to the American Urological Association and European Association of Urology guidelines. Future areas for research are identified.

Decreased transcriptional activity of calcium-sensing receptor gene promoter 1 is associated with calcium nephrolithiasis

BACKGROUND

CaSR gene is a candidate for calcium nephrolithiasis. Single-nucleotide polymorphisms (SNPs) encompassing its regulatory region were associated with calcium nephrolithiasis.

AIMS

We tested SNPs in the CaSR gene regulatory region associated with calcium nephrolithiasis and their effects in kidney.

SUBJECTS AND METHODS

One hundred sixty-seven idiopathic calcium stone formers and 214 healthy controls were genotyped for four CaSR gene SNPs identified by bioinformatics analysis as modifying transcription factor binding sites. Strontium excretion after an oral load was tested in 55 stone formers. Transcriptional activity induced by variant alleles at CaSR gene promoters was compared by luciferase reporter gene assay in HEK-293 and HKC-8 cells. CaSR and claudin-14 mRNA levels were measured by real-time PCR in 107 normal kidney medulla samples and compared in patients with different CaSR genotype.

RESULTS

Only rs6776158 (A>G), located in the promoter 1, was associated with nephrolithiasis. Its minor G allele was more frequent in stone formers than controls (37.8% vs 26.4%, P = .001). A reduced strontium excretion was observed in GG homozygous stone formers. Luciferase fluorescent activity was lower in cells transfected with the promoter 1 including G allele at rs6776158 than cells transfected with the A allele. CaSR mRNA levels were lower in kidney medulla samples from homozygous carriers for the G allele at rs6776158 than carriers for the A allele. Claudin-14 mRNA levels were also lower in GG homozygous subjects.

CONCLUSIONS

Minor allele at rs6776158 may predispose to calcium stones by decreasing transcriptional activity of the CaSR gene promoter 1 and CaSR expression in kidney tubules.

Prevalence of renal stones in an Italian urban population: a general practice-based study

Kidney stones represent a common condition characterized by significant morbidity and economic costs. The epidemiology of kidney stones is not completely understood and may vary substantially based on geographic, socioeconomic and clinical factors; the present study aims at defining the prevalence and diagnostic patterns of kidney stones in a cohort representative of the general population in Florence, Italy. A sample of 1,543 adult subjects, all Caucasians, was randomly selected from a population of over 25,000 subjects followed by 22 general practitioners (GPs). Subjects were administered a questionnaire requesting the patient's age and sex, any history of kidney stones and/or colics and the prescription of kidney ultrasound (US) examination. GPs data-bases were also interrogated. Crude and adjusted prevalence proportions and ratios (PRs) with corresponding 95% confidence intervals (CIs) were computed. Furthermore, the association between the practice pattern of each physician with respect to US prescription and the prevalence of kidney stones was investigated. The overall prevalence of kidney stones was 7.5% (95% confidence interval 6.2, 8.9%), increasing with age until 55-60 years and then decreasing. About 50% reported recurrent disease. There were no significant differences in prevalence among males and females. GPs who tended to prescribe more US examinations were more likely to have more patients with kidney stones (adjusted PR 1.80, 95% CI 1.11, 2.94; p = 0.020). The present study confirms both the high prevalence and the regional variability of kidney stones. Practice patterns may be involved in such variability.

Diagnostic and Therapeutic Approach in Patients with Urinary Calculi

The natural history of urolithiasis includes the risk of recurrence and of the development of chronic kidney and/or bone disease, which is why a thorough clinical and metabolic evaluation of these patients is of the utmost importance at disease onset. This paper is aimed at identifying the type of urolithiasis, the related risk factors, and the corresponding treatment options. The diagnostic and therapeutic approach described here includes 1) accurate history taking to detect secondary nephrolithiasis and screen for the main risk factors for kidney and bone disease; 2) metabolic evaluation graded according to different complexity levels based on the severity of the disease and the presence of risk factors; 3) carrying out appropriate imaging procedures. The resulting information allows to plan treatment based either on general rules of lifestyle and diet, or on selected medical intervention, if necessary. This report, which is based on current guidelines, was produced by the Gruppo Italiano di Studio Multidisciplinare per la Calcolosi Renale. It is addressed to all professionals involved in the management of patients suffering from nephrolithiasis, first of all general practitioners, who often become involved immediately at the onset of the disease.

[Diagnostic and therapeutic approach in patients with urinary calculi]

The natural history of urolithiasis includes the risk of recurrence and of the development of chronic kidney and/or bone disease, which is why a thorough clinical and metabolic evaluation of these patients is of the utmost importance at disease onset. This paper is aimed at identifying the type of urolithiasis, the related risk factors, and the corresponding treatment options. The diagnostic and therapeutic approach described here includes 1) accurate history taking to detect secondary nephrolithiasis and screen for the main risk factors for kidney and bone disease; 2) metabolic evaluation graded according to different complexity levels based on the severity of the disease and the presence of risk factors; 3) carrying out appropriate imaging procedures. The resulting information allows to plan treatment based either on general rules of lifestyle and diet, or on selected medical intervention, if necessary. This report, which is based on current guidelines, was produced by the Gruppo Italiano di Studio Multidisciplinare per la Calcolosi Renale. It is addressed to all professionals involved in the management of patients suffering from nephrolithiasis, first of all general practitioners, who often become involved immediately at the onset of the disease.

Idiopathic hypercalciuria and calcium renal stone disease: our cases

Renal idiopathic stone disease affects about 8% of the Italian population. The most common form in western countries (70- 80% of the cases) is calcium nephrolithiasis, with stones formed mainly by calcium oxalate and phosphate. One of the main metabolic anomalies that is often associated with calcium nephrolithiasis is hypercalciuria. Primary hypercalciuria is a metabolic defect characterized by an increased renal calcium excretion. This metabolic alteration is present in the general population with a frequency of 5-10%, but can reach 45-50% in subjects affected by nephrolithiasis. We studied 149 patients affected by idiopathic calcium nephrolithiasis.The aim of the present study was to evaluate the association between familiarity for nephrolithiasis and hypercalciuria in this population of patients.

The general practitioner and nephrolithiasis

Nephrolithiasis is a multifactorial disease the genesis of which is influenced by genetic, metabolic and environmental factors which determine a series of alterations in the urinary excretion of a number of substances, the cause of the disease itself. The general practitioner is often the first professional to be consulted as regards clinical and therapeutic treatment at the moment of the onset of nephrolithiasis, renal colic, inasmuch as contacted directly by the patient. His role however should not be limited to this initial phase but becomes of strategic importance throughout the subsequent diagnostic procedure; this is especially true with regard to relapses, in correctly placing the patient and, if necessary, referring him/her to the most appropriate specialist area. Running through the entire process which the lithiasic patient encounters from the onset of the disease until therapeutic treatment begins, it is clear how an appropriate initial approach can, in many cases, simplify and optimise such process. On the basis therefore of a complete medical record, and a few simple, biochemical and instrumental tests, the general practitioner is in a position to decide whether to treat the patient directly or to refer him/her to the most appropriate specialist field for investigation at a higher level.Over the last decades nephrolithiasis has progressively changed from being a disease of mainly surgical pertinence to being one of multidisciplinary medical interest in which the figure of the General Practitioner has a primary role, both during the initial diagnostic phase, by means of the correct physio-pathological identification of the problem, and in the subsequent phases as regards the choice and co-ordination of the various specialists involved.

Biochemical evaluation in renal stone disease

Renal stone disease may ensue from either derangements of urine biochemistries or anatomic abnormalities of kidneys and urinary tract. Genetic, environmental and dietary factors may also cooperate in the pathophysiology of nephrolithiasis. An adequate metabolic evaluation should focus on the urinary excretion of promoters and inhibitors of stone formation as well as on the occurrence of systemic diseases potentially related to secondary nephrolithiasis (i.e., endocrine disturbances, malabsorption, bone diseases). Moreover, metabolic investigations should provide reliable information on patient's dietary habits, guide towards the best therapeutic approach and enable the physician to verify patient's compliance to prescribed therapies.AN EXTENSIVE METABOLIC EVALUATION IS RECOMMENDED IN PATIENTS WITH ACTIVE STONE DISEASE (NAMELY, AT LEAST ONE NEW STONE WITHIN THE LAST TWO YEARS), OR IN THOSE HAVING HAD A SINGLE STONE EPISODE OCCURRED IN PECULIAR CONDITIONS: familial history of disease, childhood, menopause, pregnancy, systemic diseases. Simplified protocols may be adequate in non-active nephrolithiasis or in patients with single stone and no relevant risk factors.In our Stone Centre, a so-called "first level screening" is performed by routine, in order to assess urinary supersaturation with stone forming salts and evaluate the excretion of dietary-related metabolites in urine. Relative blood and urine determinations are reported below.IN VENOUS BLOOD: urea, creatinine, uric acid, Na, K, total and ionised Ca, Mg, P, Cl, alkaline phosphatase, gas analysis. In 24-hr urine samples: urea, creatinine, uric acid, Na, K, Ca, Mg, P, Cl, oxalate, inorganic sulphate, citrate, pH, ammonia and titratable acidity. IN FASTING URINE SAMPLES: Ca, citrate, creatinine, hydroxyproline, Brand's test for cistinuria, urine sediment, urine culture. If the first-level evaluation suggested an abnormal bone turnover, then further determinations are warranted, namely, calciotropic hormones (blood Vitamin D and PTH), markers of bone resorption (urine pyridinium crosslinks, serum crosslaps) and formation (serum osteocalcin) bone mineral density.EVENTUALLY, MORE SOPHISTICATED INVESTIGATIONS ARE REQUIRED TO IMPROVE THE DIAGNOSIS OF PECULIAR DISEASES: serum oxalate and glycolate, urine glycolate and L-glycerate, hepatic AGT activity (primary hyperoxalurias); genetic tests (hereditary nephrolithiasis); acidification tests (renal tubular acidosis).

Echocardiographic evaluation of children with and without family history of essential hypertension

A family history of hypertension is considered a risk factor for developing hypertension. We studied two groups of normotensive children (aged 14 years): one comprising 14 subjects with family history of hypertension, the other comprising 15 subjects without family history of hypertension. Children were comparable with respect to age, weight, height, body surface area, heart rate, and arterial blood pressure. M-mode echocardiography demonstrated higher interventricular septum/posterior wall ratio in progeny of hypertensive subjects. Interestingly, all the parameters evaluated were within the normal limits. Our data suggest that a certain degree of cardiac changes is present in children with positive family history of hypertension, though further studies are needed before considering these findings predictive of future essential hypertension.

A modified bladder washout test to improve diagnostic results in chronic urinary tract infections

Bladder washout (BWO) and antibody-coated bacteria (ACB) tests were performed on 25 patients with radiological and/or clinical evidence of chronic upper urinary tract infection (UTI) and 12 patients with asymptomatic bacteriuria. Using a traditional single-washout procedure, the BWO test gave equivocal results in many cases of chronic pyelonephritis; this seemed mainly due to the lack of complete bladder sterilization. A modified procedure, including double sterilization and irrigation, biochemical typing of isolated bacteria, and evaluation of temporal pattern of bacteriuria recurrence, was then introduced. Although preliminary results of the modified BWO test demonstrated a general improvement in the diagnosis of the infection site, it seemed rather difficult, at least in chronic UTI, to establish localizing criteria based on definite numeric changes in bacterial counts after washout.

The maternal 24-h blood pressure (BP) profile as a predictor of fetal distress

No mention is made of any aspect of BP bioperiodicity, among current clinical criteria for diagnosing pregnancy-related hypertension. The abnormal BP, based on a single unqualified measurement, is accepted and utilized as a clinical feature to identify pregnancy at risk. Systolic, diastolic and mean arterial blood pressure were measured every 15 min for 24 h in 5 women (2 non pregnant clinically healthy subjects, 1 clinically healthy subject in her third trimester of pregnancy, 1 presenting mild and 1 severe toxiemia, also in their third trimester of pregnancy) by an automated BP recording apparatus (Dynamap). All variables, analyzed by the single cosinor method, exhibited statistically significant circadian rhythms. A high amplitude could nullify the time-unqualified usual range. The change in circadian amplitude precedes an overt mesor hypertension and constitutes a tool for earlier detection of fetal distress.

Assessment of optimal dose of diuretic associated with fixed dose of beta-blocking: a new experimental model based on multiple sampling of blood pressure performed by self-measurements

A new experimental model is presented for determining the optimum dose of 3 different doses (13 mg, 25 mg, 37 mg per day) of hydrochlorothiazide employed to enhance hypotensive effect of 200 mg/day of metoprolol in human hypertension. The model takes into account the circadian variability of blood pressure as sinusoidal function and wash-out effect as a linear trend so as to compensate for bias due to normal temporal variability.