0022-5347/81/1266-0072$02.00/0 THE JOURNAL OF UROLOGY Copyright© 1982 by The Williams & Wilkins Co.
Vol. 127, January Printed in U.S.A.
WHAT IS A UROLITH AND WHAT IS A RECURRENT UROLITH? HANS-JOACHIM SCHNEIDER From the Clinic and Outpatient Clinic of Urology, Friedrich-Schiller- University, Jena, German Democratic Republic
Responses to a questionnaire on the terms urolith and recurrent urolith from 29 stone research workers from all over the world were analyzed. Although a general definition of urolith was possible from these responses the term recurrence raised various opinions and objections. Until more data are obtained on stone genesis additional stone formation in a patient should be referred to as a recurrence, irrespective of its composition, site and interval since the preceding stone episode. (table, Nos. 15 and 19). Gebhardt states that crystalline aggregations may contain high molecular organic substances and/or be membrane-like enveloped by them (table, No.10). According to Colabawalla the definition of urolith should include the kidney as a place of stone formation (table, No. 6). Lutzeyer also suggests that the localization of primary stone formation (in the tubular system, peritubularly and intratubularly) should be defined (table, No. 14). Since the uropoietic system implies the site of urine formation Sutor suggests that the more general word urinary tract should be used (table, No. 24). Scholz defines any mineral deposit in the kidney as a stone, whereas Smith refers only to those within the urinary tract, from the collecting tubules (calcified papillary tips included) down to the urethra (table, Nos. 21 and 22). There are great differences of opinion concerning the question of whether crystals should be referred to as stones. V ahlensieck indicates that uroliths are biocrystals formed in the uropoietic system of an inorganic substance or several inorganic components, which also contain organic substances (table, No. 28). Others regard crystalluria as a physiologic process and indicate that a stone is only the result of an aggregation of crystals (table, Nos. 8, 10, 13, 15, 21 and 25). In contrast to crystalluria only a particle > 1,000 µm. in diameter is defined as a urolith by Robertson (table, No. 19). Scholz, in his definition, mentions the aggregation of crystals that normally occurs in the urine but he neglects stones from drugs (table, No. 21). Budevski's definition also comprises stone size. He states in his defmition " ... a solid crystalline phase of microscopic size, which originates in the urinary tract from qualitatively and/or quantitatively altered urine" (table, No. 5). According to Brien the definition of the urolith must consider the site of origin, composition, cause of formation and size of the concrements. He states, "Uroliths are solid concretions originated within the urinary system as a result of pathologic processes. As a rule they consist of crystalline inorganic and organic substances and to a lesser degree of high molecular substances" (table, No. 3). The most detailed definition was given by Zechner, "The urolith is the potentially clinically relevant manifestation of a disturbance in the physico-chemical balance and/or the hydrodynamic system of the urine and the urinary tract. It is composed of a non-crystalline, protein-containing part (matrix) and one or several crystalline components, the percentage of the different components varying greatly. With a few exceptions (foreign bodies), the chemical structure of a stone is based on components which are also excreted in the urine under normal physiological conditions, though at varying concentrations, which does not in all cases permit to draw conclusions from the composition concerning stone genesis" (table, No. 29). On the basis of the various replies the following general definition of a urolith is suggested and opened to discussion: Uroliths are solid structures that arise from disturbances of the physicochemical balance and/or of the hydrodynamic system of the urine, and the urinary tract from the collecting system
Although urolithiasis is probably as old as mankind itself great differences prevail in the various countries concerning opinions on its frequency, distribution of types, localization and ratio of sexes and age of patients. Bladder stones used to predominate and children were affected most often. However, in most countries today bladder stones are rare and so are uroliths in children. Only in a few countries do uroliths occur endemically in children. 1 In Europe about 1 to 2 per cent of the population are stone patients. Ljunghall found that > 10 per cent of the Swedish male population were affected by stones. 2 In the United States 12 per cent of the population must expect a stone episode in their lifetime. 3 Hence, the general interest in this syndrome is great, which is illustrated by the numerous reports of increasingly interdisciplinary research work as well as by the national and international stone symposia. For comparability of communications on epidemiological inquiries, stone analyses and results of therapy it is necessary to refer to the same conception, which is not often the case. The greatest confusion occurs in connection with the frequently used term recurrent stone. Often researchers start from completely different ideas and sometimes the conception is regarded to be meaningless. An attempt was made to find acceptable definitions of urolith and recurrent urolith by questioning experts from several countries. MATERIAL AND METHODS
Questionnaires were sent to 50 stone research workers and clinicians in 21 countries to discuss the definition of urolith and the conception of recurrent stone. Only 29 answers could be analyzed (see table). RESULTS
General definition of urolith. The definition of urolith provided by Schultheis had been given on the questionnaire as a starting point for discussion-"A solid phase occurring in the urine within the uropoietic system, which is irreversible and is composed of one of several stone forming substances and a matrix". 4 Some colleagues accept this definition with alterations (table, Nos. 2, 16-18, 20 and 23). Others recommend alterations concerning inaccuracies or even mistakes in formulation. They indicate that when the possibility of medicinal litholysis of uric acid stones, and also of cystine and struvite stones, and direct instrumental chemolitholysis are considered the term irreversible is no longer justified (table, Nos. 4, 10, 11 and 14). Thomas claims that not every stone contains a matrix, for example whewellite, and that mentioning it in the definition provides a wrong idea of its importance in stone formation (table, No. 25). Matouschek and Robertson also emphasize that some high molecular organic substance may be but need not be contained Accepted for publication December 5, 1980. 72
WHAT IS UROLITH AND WHAT IS RECURRENT UROLITH?
Respondents to questionnaire Identifying No. in Text 2
3 4 5
6 7 8 9
Respondent Berenyi, M. Boyce, W. H. Brien, G. Brockis, J.C. Budevski, G. Colabawalla, B. N. Finlayson, B. Frang, D.
Hungary United States German Democratic Republic Australia Bulgaria India United States Hungary
12 13 14
Jonas, U. Joost, J. Krizek, V. Lutzeyer, W.
Federal Republic of Germany Netherlands Austria Czechoslovakia Federal Republic of Germany Federal Republic of Ger-
16 17 18 19 20 21
Oravisto, K. Oreopoulos, D. G. Pinto, B. Robertson, W. G. Rutishauser, G. Scholz, D.
Smith, L. H. Si:ikeland, J.
25 26 27 28
Sutor, D. J. Thomas, J. Toth, C. Williams, H. E. V ahlensieck, W.
Finland Canada Spain England Switzerland Federal Republic of Germany United States Federal Republic of Germany England France Hungary United States Federal Republic of Germany Austria
down to the urethra. These structures have a minimal size of 1,000 µm. and consist mainly of crystalline and, to a lesser degree, of amorphous organic and/or inorganic components, which may be mixed with a noncrystalline high molecular substance (matrix). In this definition site and cause of origin, composition and size have been taken into consideration. Intrarenal calcifications (nephrocalcinosis, experimental crystal aggregations after administration of ethylene glycol or oxamid) as well as prostatic concrements, which again and again are mentioned as uroliths, are excluded. On the other hand, rare stone types (silicates, sulfonamide stones and so forth) are included. Recurrent stones. The question "What is a recurrent stone?" was explained on the questionnaire in detail by 4 aspects: 1) any further stone in the course of life, 2) any further stone after a certain period, 3) another stone of the same composition only and 4) another stone in the same organ or on the same side. Half of the experts call any further stone in the course of life a recurrent stone (table, Nos. 2, 4, 7, 8, 11, 15, 16, 21, 23, 26-29). Therefore, it is dear why we found an almost 50 per cent recurrent stone incidence among 50,000 stones analyzed, whereas the recurrence rate in a 10-year period is <20 per cent. 5 In this comprehensive definition some restrictions and additions are necessary. Matouschek indicates that an unambiguous definition is not possible at the present stage of stone research (table, No. 15). If any further stone in the course of life is a recurrent stone a systemic metabolic disease is assumed and heterogeneous influences of the site are neglected. However, this is of decisive importance if the same side or the same organ is included (table, Nos. 3 and 20). The term recurrent stone should only be used if the new formation has been demonstrated by means of modern diagnostics and if it is not due to topographic or mineralogic changes of an existent concrement (table, No. 29). A few researchers questioned consider a temporal restriction necessary (table, Nos. 13, 17, 18 and 25). Thomas and Budevski suggest a 5-year limit but only for idiopathic stones (table, Nos. 5 and 25). Pinto does not call another stone
after 6 years a recurrent stone even if it occurs at the same site and is of the same composition (table, No. 18). Oreopoulos admits recurrences only within 1 year but he, as well as Oravisto, suggests a differentiation between early and late recurrences (table, Nos. 16 and 17). For other researchers the same stone type is an essential criterion of a recurrence (table, Nos. 1, 3, 5, 6, 12 and 19). Time and site were not considered. Cystine stones are a typical example. If in the course of an infection a cystine stone patient has a struvite stone Robertson does not call it a recurrence (table, No. 19). Berenyi then refers to a cystine-struvite recurrence (table, No. 1). According to Robertson it is meaningless to refer to recurrent stones; it is a recurrent stone disease. He states that it is, " ... a disorder in which 2 or more stones of the same stone type form in the urinary tract at different points in time during the life of the patient" (table, No. 19). Whenever the same type of stone is formed the individual is considered a recurrent stone former of a given type (table, No. 7). Many researchers believe that there is a connection with the same organ or the same side if stone formation is caused mainly by pathomorphological or urodynamically effective disturbances in urine flow, for example subpelvic stenoses (table, Nos. 3, 5, 10, 13-15 and 20). Here, heterogeneous influences are of decisive importance. Berenyi indicates that he combines stone type and localization, neglecting time. To him a recurrent urolith is, "another or new stone of same composition in the same organ in the course of life" (table, No. 1). Because of the differences in genesis and epidemiology Colabawalla differentiates between kidney and bladder stones as well as between their recurrences (table, No. 6). Some researchers principally object to the term recurrent stone. Finlayson indicates that recurrent stone disease does not necessarily include formation of a recurrent stone (table, No. 7). 6 Therefore, he believes that a recurrent stone former need not have recurrent stones. Smith also avoids the term recurrent stone and mentions metabolically active urolithiasis (table, No. 22). Not the recurrent stone is essential but the individual who had i;:;2 stone episodes, according to Sutor (table, No. 24). DISCUSSION
Based on the responses to the questionnaire it is possible to suggest a generally acceptable definition of urolith but it is not possible to define recurrent stone or recurrent stone disease. Perhaps it is most logical to refer to the cause of repeated stone formation, which requires 2 definitions: 1) The recurrent stone disease implies the presence of a metabolic disorder and pathologically altered urine composition, irrespective of localization and interval since the first stone. Detailed investigation of metabolism and comparable, reproducible stone analysis are necessary for an exact definition. For analysis it is necessary to classify the main constituent or the nucleus-shell ratio. 2) Recurrent stone disease implies that stone formation is due to the same local factors, for example obstruction with associated infection, irrespective of stone composition and interval. This will only apply to a small number of stones (stones in infected congestive kidney, in ureteroceles, with hair incrustations after reconstruction of the urethra and so forth). In many cases of recurrent stones it will be difficult to demonstrate either metabolic or local causes. For uric acid-oxalate or for mixed oxalate-phosphate stones the main constituent often is varying thus, even the classification of the same stone type is difficult. Certainly, the weddelite kidney stone in a 36-year-old man is not the recurrence of a struvite urethra stone after a DenisBrowne operation in childhood. If a prostate patient suffers from a uric acid bladder stone this can, strictly speaking, be regarded as a recurrence of the previous stone. The criterion of our success in stone treatment and followup is mainly a low recurrence rate. We attempt to decrease the number of first diseased patients by general preventive measures. Although we know about numerous problems in the present situation of knowledge on urolithiasis, the following
definition is suggested and opened to discussion to make comparison possible and to analyze a great number of collected statistics: Any occurrence of a second or any further urolith is referred to as a recurrent stone or recurrent stone disease, irrespective of its composition or localization, or the interval since the first stone episode. This term does not include continuous crystalluria without clinically manifest concrements. If researchers publish data on recurrence rates the type, site and time limit should be discussed in detail. REFERENCES
1. Van Reen, R.: Idiopathic Urinary Bladder Stone Disease. Fogarty International Center Proceedings No. 37, Department of Health, Education and Welfare Publication No. 77-1063. Bethesda: National Institutes of Health, 1977. 2. Ljunghall, S.: Family history of renal stones in a population study of stone-formers and healthy subjects. Brit. J. Urol., 51: 249, 1979. 3. Sierakowski, R., Finlayson, B., Landes, R. R., Finlayson, C. D. and Sierakowski, N.: The frequency of urolithiasis in hospital discharge diagnoses in the United States. Invest. Urol., 15: 438, 1978. 4. Schultheis, Th.: Einteilung und Morphologie der Harnsteine. In: Handbuch der Urologie. Die Steinerkrankungen. Edited by K.
Boshamer. Berlin: Springer-Verlag," chapt. 2, p. 1, 1961. 5. Schneider, H.-J.: Epidemiologische Aspekte der Urolithiasis. Urologe B, 19: 54, 1979. 6. Finlayson, B. and Reid, F.: The expectation of free and fixed particles in urinary stone disease. Invest. Urol., 15: 442, 1978. EDITORIAL COMMENT This study is useful for all persons who engage in studies of urolithiasis. However, I am not able to come to the same conclusion with regard to the definition of recurrent urolithiasis as has Doctor Schneider. At the present stage of research development in urolithiasis I do not believe that we can call the occurrence of a second or subsequent calculus owing to, for example, struvite a recurrence if the initial calculus was caused by cystine. It may be that the cystinuria is under control by various means of therapy. The second urolith composed of struvite could then represent a complication of the initial therapy of the cystine stone patient if such treatment might have induced urinary infection. It would appear that I agree with the concepts proposed by Robertson and Berenyi (table, Nos. 1 and 19). The difference may be trivial but I believe that such a distinction is important. George W. Drach Section of Urology, Department of Surgery University of Arizona College of Medicine Tucson, Arizona