[Urinary calculi. 1: Epidemiology, laboratory diagnosis, genetics and infections]

Cystinuria: an inborn cause of urolithiasis

Cystinuria (OMIM 220100) is an inborn congenital disorder characterised by a defective cystine metabolism resulting in the formation of cystine stones. Among the heterogeneous group of kidney stone diseases, cystinuria is the only disorder which is exclusively caused by gene mutations. So far, two genes responsible for cystinuria have been identified: SLC3A1 (chromosome 2p21) encodes the heavy subunit rBAT of a renal b^0,+ transporter while SLC7A9 (chromosome 19q12) encodes its interacting light subunit b^0,+AT. Mutations in SLC3A1 are generally associated with an autosomal-recessive mode of inheritance whereas SLC7A9 variants result in a broad clinical variability even within the same family. The detection rate for mutations in these genes is larger than 85%, but it is influenced by the ethnic origin of a patient and the pathophysiological significance of the mutations. In addition to isolated cystinuria, patients suffering from the hypotonia-cystinuria syndrome have been reported carrying deletions including at least the SLC3A1 and the PREPL genes in 2p21. By extensive molecular screening studies in large cohort of patients a broad spectrum of mutations could be identified, several of these variants were functionally analysed and thereby allowed insights in the pathology of the disease as well as in the renal trafficking of cystine and the dibasic amino acids. In our review we will summarize the current knowledge on the physiological and the genetic basis of cystinuria as an inborn cause of kidney stones, and the application of this knowledge in genetic testing strategies.

[Recurrence prevention of kidney stone disease]

In each urolithiasis patient the individual risk for recurrence determines the need for specific medical treatment. Therefore, a brief evaluation of the risk status after stone passage is mandatory to define patients at high risk for recurrence. Only one quarter of all urolithiasis patients are at high risk or suffer from severe metabolic disorders, which both demand further metabolic work-up prior to medical therapy. However, the other three quarters benefit sufficiently from general preventive measures, such as high fluid intake, well-balanced mixed diet and lifestyle changes. This article summarizes the recent recommendations for stone-specific recurrence prevention, discusses the different pharmacological treatment options and sketches the follow-up concept for high risk patients with ongoing medication.

Diagnostic examination of the child with urolithiasis or nephrocalcinosis

Urolithiasis and nephrocalcinosis are more frequent in children then currently anticipated, but still remain under- or misdiagnosed in a significant proportion of patients, since symptoms and signs may be subtle or misleading. All children with colicky abdominal pain or macroscopic hematuria should be examined thoroughly for urolithiasis. Also, other, more general, abdominal manifestations can be the first symptoms of renal stones. The patients and their family histories, as well as physical examination, are important initial steps for diagnostic evaluation. Thereafter, diagnostic imaging should be aimed at the location of calculi but also at identification of urinary tract anomalies or acute obstruction due to stone disease. This can often be accomplished by ultrasound examination alone, but sometimes radiological methods such as plain abdominal films or more sensitive non-enhanced computed tomography are necessary. Since metabolic causes are frequent in children, diagnostic evaluation should be meticulous so that metabolic disorders that cause recurrent urolithiasis or even renal failure, such as the primary hyperoxalurias and others, can be ruled out. The stone is not the disease itself; it is only one serious sign! Therefore, thorough and early diagnostic examination is mandatory for every infant and child with the first stone event, or with nephrocalcinosis.

[Urolithiasis in children--rational diagnosis, therapy, and metaphylaxis]

With a proportion of 1-5%, children constitute only a small number of all patients with urolithiasis. Nevertheless, pediatric stone disease is an important health care problem because of the high recurrence rate and the threat of progredient renal function impairment with consecutive loss of quality of life. Modern therapies, especially extracorporeal shock wave lithotripsy (ESWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PCNL), have caused a revolution in the operative treatment spectrum. Open surgery is required for stone removal only rarely, such as for the simultaneous repair of urinary tract anomalies. The minimally invasive modalities of modern stone therapy - mainly ESWL as the treatment of first choice - have led to widespread disregard of stone metaphylaxis. The important principle that says an urinary stone is just a symptom and not the cause of the disease is often forgotten. So it must be noted that despite the high standard of care in Germany, not all problems regarding urinary stone disease are being resolved, particularly in childhood. This article presents the current knowledge of the most important aspects of stone therapy and the methods of treatment in children.

[Calcium oxalate stone formation. New pathogenetic aspects of an old disease]

Calcium oxalate (CaOx) urolithiasis is a very common disorder. Surprisingly, the pathogenetic mechanisms leading to CaOx stone formation have been largely unknown so far. The long-accepted simple explanation by an exceeding of the solubility product of lithogenic substances in the urine cannot sufficiently describe the complex processes. Deviating from the hypothesis that proclaims that the initial crystal deposition takes place in the lumens of renal tubules, new insights suggest a primary plaque formation in the interstitial space of the renal papilla. Initially, calcium phosphate (CaPh) crystals and organic matrix are deposited along the basement membranes of the thin loops of Henle and extend further in the interstitial space to the urothelium, constituting the so-called Randall's plaques that can be regularly found during endoscopy of CaOx-stone-forming patients. These CaPh crystals seem to be the origin for the development of future CaOx stones, which form by the attachment of further matrix molecules and CaOx from the urine to the plaque. The driving forces, the exact pathogenetic mechanisms, and the involved matrix molecules remain largely unknown. Possibly, completely different pathomechanisms lead to the common clinical diagnosis of"CaOx stone former."

[Evidence-based pharmacological metaphylaxis of stone disease]

Approximately one-fourth of urolithiasis patients are at high risk for recurrent stone formation or severe metabolic disturbances. These patients need specific metaphylaxis for effective stone prevention, adjusted to their individual metabolic risk. Recent recommendations for the pharmacological treatment of stone diseases are summarized in this article. For the different treatment options, evidence from the literature was assessed. In addition, a follow-up concept for pharmacologically treated high-risk stone formers is discussed.

[What kind of stone prevention for whom? Risk-adjusted metaphylaxis following urinary stone disease]

Approximately 5% of the German population suffers from urinary stone disease, but only 25% of these urolithiasis patients are at risk of recurrent stone disease or a severe metabolic disorder. It is important that patients at high risk are picked up early, so that appropriate therapy and measures designed to prevent secondary stone disease can be implemented. Risk classification is easily achieved by combining stone analysis with a basic diagnostic program. Patients at low risk need no further diagnostic evaluation or treatment, so that it is enough to recommend general metaphylaxis in these cases. In contrast, patients at high risk require additional specific aftercare and should be evaluated with the aid of a comprehensive diagnostic program from the start to allow precise definition of the metabolic targets.

Rational evaluation of urinary stone disease

This article outlines the recent state of the art in the metabolic diagnosis of stone disease. The current literature in the field of urolithiasis-including the existing German and EAU-Guidelines as well as the Conference Book of the 1st International Consultation on Stone Disease-was critically reviewed. As far as possible the references were rated according to the EBM criteria. The occurrence of stone disease in the western world is increasing greatly. Modern lifestyle, dietary habits and excess weight-problems of affluent societies-are emerging as the important promoters of the "stone boom" in the new millennium. This even affects children, whose stone prevalence is otherwise significantly less than that of adults. Criteria for the high-risk group of stone formers were clearly defined. A diagnostic standard is formulated for the basic and the elaborate metabolic evaluation of a stone patient. The diagnostic pathways for the most important stone types and metabolic disorders, respectively, are described. The present concept allows a precise risk classification of each stone former and facilitates the decision whether stone-specific measures in addition to the basic metaphylaxis are recommendable or not.

Diagnosis and metaphylaxis of stone disease. Consensus concept of the National Working Committee on Stone Disease for the upcoming German Urolithiasis Guideline

This review draws the recent state of the art in metabolic diagnosis and metaphylaxis of stone disease. It is the basis for the consensus approval with the other medical societies and institutions in Germany involved in the guideline process of the new "Urolithiasis Guideline". The German Working Committee on Stone Disease reviewed critically the current literature in the field of urolithiasis-including the existing German and EAU-Guidelines as well as the Conference Book of the First International Consultation on Stone Disease. As far as possible the references were rated according to the EBM criteria. On this basis the expert group discussed all pathways and statements regarding the management of stone disease. The present review coincides with the consented guideline draft of the German Working Committee on Stone Disease. Occurrence of stone disease in the western world increases seriously. Modern lifestyle, dietary habits and overweight-problems of the affluent societies-emerge to be the important promoters of the "stone-boom" in the new millennium. This even affects children, whose stone prevalence is otherwise significantly less than that of adults. Criteria for the high risk group of stone formers were clearly defined. A diagnostic standard is formulated for the basic and the elaborate metabolic evaluation of a stone patient. Approximately 75% of all stone patients could anticipate stone recurrence with elementary reorientation of their lifestyle and dietary habits, summarized as general metaphylaxis. About 25% of the stone formers require additional pharmacological intervention to normalize their individual biochemical risk, precisely compiled for each stone type as specific metaphylaxis.

[Calcium oxalate stones and hyperoxaluria. What is certain? What is new?]

Approximately 4 million Germans suffer from stone disease. In the majority of cases (70-75%) it is calcium oxalate. Its pathophysiology is complex and comprises disorders such as hypercalciuria, hyperoxaluria, hypocitraturia, hyperuricosuria, and hypomagnesuria. These biochemical changes in urine are well known as "classic" risk factors of calcium oxalate stone formation. However, studies in the last decade showed that calcium oxalate stones are strongly related with other diseases or disorders such as overweight, hypertension, or a lack of oxalate-degrading bacteria in the gut. The evidence for these "new" risk factors in the literature is very strong. It is particularly important in regard to effective treatment and aftercare of patients with calcium oxalate stones to be familiar with both the "classic" and the new risk factors.

[Outpatient extracorporeal shock wave lithotripsy. Prospective evaluation of 2937 cases]

PURPOSE

Extracorporeal shock wave lithotripsy (ESWL) is mainly performed on inpatient basis in Germany. It has yet to be considered if outpatient treatment in Germany is indicated when sufficient urological care is guaranteed.

MATERIALS AND METHODS

Between September 1989 and December 2002, a total of 10,505 patients with urolithiasis were treated at the Institut zur Steinzertrümmerung in Troisdorf, Germany with the Siemens Lithostar plus. Of these patients, 2937 (43%) were treated on an outpatient basis. The data were collected prospectively from September 1989. Patient satisfaction was evaluated with a self-developed, non-validated questionnaire.

RESULTS

The overall success rate was 81.8%. The complication rate after ESWL was 40.2%, whereas 4.9% of the patients had to be admitted to a hospital; 73.5% did not need auxiliary treatment before and 78.6% after ESWL, respectively. More than 90% of the patients were satisfied with the result of outpatient treatment.

CONCLUSIONS

Outpatient ESWL can be safely performed as minimally invasive treatment after thorough patient selection in Germany. The success and quality of treatment was not altered because of outpatient treatment. A network of ESWL center and post-interventional care center has to be established to guarantee 24-h service for auxiliary necessities.

[Alkaline citrates in urology. A status report]

Alkaline citrates have been used as an efficient therapy in hypocitraturic calcium nephrolithiasis, uric acid lithiasis, cystinuria, and renal tubular acidosis. Furthermore, alkaline citrates are very effective in treating and preventing hyperchloremic metabolic acidosis in patients with urinary diversion. The main physiological effects during urolithiasis therapy have been significant increases in urinary pH, in citrate and potassium, and a decrease in calcium excretion. This paper reviews current indications, therapy modalities, and metaphylactic use reported in the literature and/or recommended by the Deutsche Gesellschaft für Urologie (DGU) and the European Association of Urology (EAU). It is intended to give useful advice for the urologist's daily practice.

[Prevention of nephrolithiasis. Established strategies and new concepts]

During the last 2 decades in Germany, only minor efforts were expended for the prevention of urinary stones. Substantial technical progress simplified the treatment of existing calculi; thus, it was more convenient to treat a new stone than to prevent its recurrence. But times change! In these days of financial squeeze in the medical system, prevention becomes more attractive. Nevertheless, strategies for kidney stone prevention developed. Established concepts for dietary advice were rejected due to the results of new randomized studies. Moreover, new pharmacological substances were introduced for metaphyalxis. The new concepts are feasible for the daily routine. For some treatment modalities in stone prevention, there is valid evidence from the literature, which should encourage us to adopt these modalities in the future. A number of drugs are used as "good common practice" without any proof from a randomized trial. Often prospective and valid studies are not available. The present paper intends to describe the status quo of nephrolithiasis prevention in Germany, focussing on confirmed data and unsolved problems.

[Ureteroscopy under intravenous analgesia with remifentanil]

In a prospective study, from September 2000 to September 2001, all ureteroscopies ( n=140) were performed under local and intravenous patient controlled analgesia using continuous infusion of remifentanil (Ultiva). The dosage of 0.15 micro g/kg/min was adapted to changing intraoperative pain (range 0.08-0.30 micro g/kg/min). Preoperative sedation with midazolam 2 mg was given 5 min prior to ureteroscopy. The efficacy of monitored anesthesia care ("Big MAC") was quantified by the patient using a visual analogue pain scale. A total of 97.1% (136/140) of the procedures were performed and finished under remifentanil. Only four male patients underwent conversion to general anesthesia due to insufficient analgesia. All but one patient would choose remifentanil again for first line anesthesia. Significant differences in pain scale values were noticed for male/female patients and ureteroscopies above/below the iliac vessel crossing. Side effects were rare being mainly hypoxic events (pO(2)<90% in 5.1%). Indication, intraoperative procedure, average surgery time (24 min), complications and primary success rate (96.6/90/63.3% stone free for distal/mid/proximal ureter, respectively) did not differ from the control group under general anesthesia. Ureteroscopies with remifentanil are safe, universally applicable because of refifentanil's organ independent esterase metabolism and as effective as general anesthesia. There is no need for PACU stay for patients due to the ultra-short drug half-life, and therefore remifentanil is cost effective and perfect in an outpatient setting.