The Mineralogy and Chemistry of Urinary Stones from the Arabian Gulf
Urinary Stones: Definition
Urinary stones are crystals, mainly of oxalate, and /or phosphate and urate formed in the urine or in the kidney. Statistical studies showed that men with ages in the range of 20 to 40 have the highest risk. People living in the arid areas (warme climates) have the highest incidence rates. The common diet in these areas are usually vegetables and tea
Most stones are formed due to dietary factores, like the intake of high dairy products or salts which would increase the amount of Ca in the urine. Low intake of water would increase the percentages of stones in the urine. Genetic effects, intake of vitamine C may play also a rolle in the formations of stones. Pain in the lower back below the ribs and blood in the urine indicate the presence of stone. Stones smaller than 5mm will usually pass. The lithrotripsy shock waves vibrate the stone so that it shatters into smaller sand like fragments usually without injury to surrounding tissue. Pressure is felt, but not pain. This process is repeated until the doctors can see on the x rays that the stone has been crushed by the shock waves. The resulting stone fragments then pass out of the body over a period of time that may be three months or more. Passing these fragments are similar to passing small stones; and more than one sufferer has stated that next time they will opt for some type of physical stone removal to avoid the prolonged painful period of these fragments being passed. While some larger or complicated cases may require more than one treatment, lithotripsy usually allows the sufferer to return to their normal
Common Mineralogical methods like the use of polarizing microscopy, X-Ray diffraction, Infra-Red and thermal analysis proved to be a ensitive tool in the investigation of urinary calculi and gave more information than chemical analysis.The role of dietary factors and enzyme triggering mechanism leading to accelerated crystallization is discussed in relation to renal stones in the Arabian Gulf States.
Urinary stones may contain various combinations of chemicals. The most common type of stone contains calcium in combination with either oxalate or phosphate. A less common type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Much less common are the uric acid stone and the rare cystine stone. The most common stones are composed of the follwoings minerals: calcium phosphate •calcium oxalate •magnesium ammonium phosphate ( "struvite") .Hoever, diammonium calcium phosphate, magnesium phosphate, cystine , urate and xanthine were also described in few cases. A less common type of stone is caused by infection in the urinary tract. This type of stone is called a struvite or infection stone. Much less common are the uric acid stone and the rare cystine stone.
Urinary tones have become increasingly common in most parts of the world (ANDERSON,1966; HODGKINSON and MARSHALL, 1975). Calculous disease of the urinary tract is common in the Arabian Gulf States (SJOVALL,1986), but reports on the disease are scarce. Several studies have examined the factors predisposing to the formation of urinary and kidney stones (PIERRATOS et al.,1994; HESS et al., 1976; GRASES et al., 1990; OKA et al., 1987; MARTIN et al .1992) The analysis o furinary calculi only by chemical methods is rather unsatisfactory (PRIEN et al., 1947; RANDALL, 1942). Polarized light microscopy has found application in many fields of scientific study but has been little used in solving medical problems. It is extensively used by mineralogists in the identification of natural and synthetic minerals and rocks and their textural relations. Calculi are closely analogous to natural minerals and their study by physical methods can shift the problem from the time-consuming chemical assaying to simple inspection of a stone thin section (PRIEN et al., 1947; RANDALL, 1942). Common mineralogical methods include the use of polarizing microscopy, thermal analysis, Infra-Red, Ultraviolet and X-ray diff raction.
X ray diffraction identifies the constituents of a calculus by their unique diffraction patterns, which allows definite identification of an unknown crystalline substance. The major advantage of x ray diffraction is its almost absolute identification of crystalline materials and mixtures of crystalline materials.
According to the results of X-Ray diffraction the stones from the Arabian Gulf can be divided into the following groups:
These stone consist mainly of struvite, dehrnite and podolite (A.S.T.M.card No.15-762, 569,and respectively). Ammonium calcium phosphate hydrate is trace (A.S.T.M card No. 22-35). These represent 11.5% of the investigated calculi.
The stones represent up 38.5% of the investigated calculi. They consists only of whewellite (A.S.T.M.card No. 20-231). Weddellite (A.S.T.M. card No.17-762) was observed as mino rmineral only in one sample.
Uricite (A.S.T.M. card No 28-2016) forms the major mineral in these stones, whereas whewelliteoccurs as a minor or a trace mineral. They represent 11.5% of the investigated stones.
4-Mixed stones These stones are a mixture of group 1 and 2 and represent 38.5% of the total stones.
Polarization Optical Crystallography With a polarizing microscope it is possible to establish the presence of crystalline material and obtain optical constants that are helpful in its identification; the polarizing microscope also may be the only available means for observing and identifying crystals. Some optical properties that may be determined are the crystal system (monoclinic, hexagonal, tetragonal, rhombic, orthorhombic, etc.), the optical sign, the refractive index, the angle of extinction, and the presence of birefringence. These properties may be compared with known data. If sufficient material is present and there is doubt about the identification, confirmatory studies by other methods are necessary. It should be remembered that proper use of the polarizing microscope requires a great deal of skill, patience and experience. It cannot be used on a casual basis. Polarizing microscopy is not applicable to analysis of calculi that contain only amorphous compounds, such as large phosphatic calculi, or those consisting of complex salts of uric acid.
. The objective of microscopy to make visible the nucleus, the crystalline structure and the order of deposition of components. The true nucleous is invisible because it is the first crystal or aggregate of crystals precipitated from solution and deposited at what eventually becomes the stone site. The nucleous is either a region from which crystalline forms radiate or the geometric center surrounded by concentric laminations. The nucleous may be roughly in the center of the stone, or it may be closer to one pole, as in a staghorn calculus . The order of deposition of components is determined including identification of nucleous, and identification of other patterns whether homogeneous, or characterized by layered, concentric or radial deposition structure. Nucleous may form from precipitation of crystals from supersaturated urine, from microscopic debris in urine, from artifacts or foreign bodies, from drugs or drug metabolites, or from calcium plaques in the renal papillae. Finding any of these components may give a clue to the petrogenesis of the stone.
Laminated oxalate (Monohydrate-Wehwellite) stone under the microscope
Mixed stone (Oxalate + Phosphate steone)
notice high interference colors of oxalate in comparison to white phosphate
The results of Microscopy show that the stones from the Arabian Gulf can be divided into the following groups:
1-Phsophatestones(SamplesC-2,C-15,andC-22) The tones range from a creamy white and chalky to buff or brown.They are characterizd by zoned texture composed of alternating colorless and thin brownish layers.The concretion is built around a non-crystalline reddish brown core.Similarly, the brown layers are isotropic and non-crystalline while the colorless layers are well crystalline and consists of radial crystals of struvite and/or podolite. The brown layers are mainly ammonium calcium phosphate hydrate as evident from X-ray powderdiffraction.
Most of these stones are brown in color and vary in shape from spheroidal to irregular-shaped asses. The stones are dense and hard.They show well developed colloform texture with alternating pale brown and colorless laminae of whewellite.The laminae are concentrated around a deep red brown amorphous core. The crystals are mostly fibrous. Crystallization increases toward the rim of the stones.
The urate stones are small and tend to have an oblate or near spheroid shape.They are characterized by colorless radial and elongated crystals of uricite.The uricite crystals show distinct parting.
The stones are of mixed type (phosphate + oxalate). The stones are pale brown, yellow with white patches with various shapes and structures. They are formed mainly of whewellite which occurs either as colorless radial crystals or brown amorphous to microcrystalline grains.The interspaces between whewellite laminae are filled with brown microcrystalline phosphate mainly podolite and/or dehrnite which form the cementing material.The texture is mainly colloform. Spindle shape texture was observed in one sample.The crystalline parts are commonly replace the amorphous brown part of the stone.
Infrared spectroscopy is specific, rapid, and versatile and can be used with specimens of various sizes. In the infrared region of the electromagnetic spectrum, light is absorbed as the vibrational stretching and bending of groups of covalently bonded atoms occur in response to excitation at specific wavelengths. Most organic and inorganic solids have absorption patterns that include several absorptance maxima at wavelengths characteristic of particular functional groups that make up the molecule. Correlation of specific observed absorption maxima of the unknown with reference spectra allows positive identification of a sample. Infrared spectroscopy is useful for the identification of noncrystalline materials, including amorphous and fatty substances. This gives it an advantage over x ray diffraction, which is useful primarily for analyzing crystalline compounds. Such compounds as carbonate apatite and hydroxyl apatite, may give weak, diffuse lines on an x ray diffraction pattern but may be identified and measured by infrared spectroscopy. A particular application of this method is the identification of drugs and drug metabolites in urinary calculi, which often have well resolved absorption maxima. Since drugs are often partially metabolized, positive identification may depend on analytic studies, the patient's drug history, and pharmacokinetic information. Infrared spectroscopy is useful also for the identification of the many artifacts that appear in calculi. Usually, infrared analysis will reveal the true nature of these artifacts. Other common artifacts easily identified by infrared spectroscopy are quartz and kaolin, both of which have highly characteristic spectra.
Differential thermal analysis (DTA) and thermo gravemtric analysis (TGA):
Temperatures of the endo thermic and exothermic reactions are characterized by the temperature at the crest of their peaks. In the phosphate stones (struvite, podolite and ammonium calcium phosphate hydrate),asymmetric broad endothermic DTA peak occurs at 128.2oC. In the oxalate stones (whewellite) , two endothermic peaks are found; one is small and symmetric and occurs at 64.2oC, and the second is large, symmetric and occurs at 204.7oC. These peaks are accompanied by a slight loss in weight as represented by the TGA curves. Peaks which occur at temperature below 150oC are mostly due to the loss of hygoscopic water. The second endothermic peaks in the oxalate stones are mainly due to the loss of water of crystallization. These peaks occur at a temperature rangeo f338.1o C to 381.1oC in the phosphate stones and are mainly due to the loss of ammonia and water of crystallization. The presence of three peaks is due to the presence of three different phosphates (struvite, podolite and ammonium calcium phosphate). Two small exothermic DTA peaks occur at the temperature range 446.7oC to 698.1oC in the phosphate stones. The first one represents dehydration and the second represents recrystallization of Mg-hydrogen phosphate to Mg-pyrophosphate. Most of loss in weight corosponds to the endothermic peaks, whereasl oss in weight due to the exothermic peaks is minor. Three exothermic peaks occur at 408oC to 501.4oC in the oxalate stone. These peaks represent a structural change of anhydrous Ca-oxalate to Ca-carbonate and loss of CO gas. All Ca-oxalate change to Ca-carbonate at 652.8oC. The decomposition of Ca-carbonate is represented by large a symmetric endothermic peak at 779.8oC. The loss in weight is gradual and in different stages.
Chemical analysis The results of chemcial analysis confirm the mineralogical results. Chemical analysis of the phosphate alculi indicates that the stones consist mainly of P2O5, MgO, CaO, C, H and N. They belong to the non-infection stones (Category I ) of ABDEL-HALIM et al. (1993). Mineralogically, these stones consist of struvite, podolite and ammounium calcium phosphate. In omparison, the oxalate calculi are poor in P2O5, MgO and rich in CaO and C. The mixed calculi are mainly oxalate and are rich in CaO and P2O5 whereas MgO is relatively low. The oxalate and the mixed types calculi belong to the infection stones (Category II) of ABDEL-HALIM et al .(1993). The urate calculi are rich in C and N, similar to uric acid stone (UrI4) described by ABDEL-HALIM et al. (1993)
The percentage incidence of phosphate, urate and oxalate stones is lower than that reported in Egypt (HAMMOUDet al ., 1973) and similar to that reported from western countries (PRIEN et
al., 1947; RANDALL, 1942; HERRING, 1962; FELLSTROM et al.,1 986). Oxalatestones and mixed
type of oxalate-phosphate stones seem to be the most common type which is in agreemnet with that reported elswhere (HERRING, 1962; FELLSTROM et al., 1986). In the Gulf States, the climate is very hot and humid and the temperature may exceed 50oC in summer. It seem likely that this climate play a major role in the incidence of urolithiasis (AL-NAAM et al., 1987; WISE and KARKE, 1961). However, an increase in the intake of animal proteins and carbohydrates lead to an increase ofoxalate and urate stones (ANDERSON, 1972; DRACH, 1978; ROBERTSON and PEACAOCK, 1982; PARKS etal., 1994). The iet of the people in the Arabian Gulf States is rich in oxalate, sugar and animal proteins. Such a diet may play a role in the formation of calcium oxalate and uric acid stones. Triggering mechanism, however, may lie in enzyme disorder. However, natural mineral crystals are the result of chemical deposition from a solution in an open space, such as a vug, or cavity in a rock formation. The first stage in the growth of acrystal is that of nucleation, which
implies that growth can commence only after a nucleus ( or seed) has been formed. In most cases the nuclei are the initial products of precipitation in a solution. The nucleus is the resut of the coming together of various ions in a saturated solutiont form the initial regular structural pattern of a crystalline solid. If a nucleus is to survive, it can do this by rapid growth so that it reduce its surface energy (the ratio of surface area to volume). If a nucleus reaches a critical size through rapid deposition of further layers of ions to its outer surface, it will have a high chance of surviving as a larger crystal. Temperature, pressure and concentration are the major factores controlling crystallization from a solution. Any solution has a point where it can no longer retain all ions and solid
begins to precipitate at this point. However, hot solution will
dissolve more ions than cold solution. Again, the higher the pressure, the more ions solution can hold in it.Thus lowering temperature or pressure, supersaturation will decrease and crystallization starts.
To prevent stone formation, drink large amounts of water and stope taking food rich oxalates such as: apples, black pepper , broccoli, cheese, chocolate, cocoa, coffee, cola, ice cream, orange, milk, spinach, tea, vitamin C and yogurt. It is adviced to take a lot of lemons to reduce the amount of Ca in the urine. Eating excessive sugar & animal protein ( meat, milk) can cause changes in the chemical composition of the urine that lead to formation of stones. In contrast, eating plenty of cereal fibre may protect these patients from the abnormalities that lead to renal stones. Eating fibre (natureal foods like wholemeal bread), flakes, brown rice, spaghetti, lasagne and plenty of fruit will increase the fibre intake and lower the risk of stones. Uric acid stones can be prevented in many cases through use of an alkaline agent that regulates the acidity of the individual's urine, a key factor controlling crystallization of uric acid. Phosphate stones (Struvite ) are composed of magnesium, phosphate, and ammonium This type of stone can result in severe urinary damage. They occur mainly due to infection with a certain type of bacteria that tends to flourish and invade the urinary following a course of antibiotic therapy. For this reason, the best preventive measure against this type of urinary stone is to be aware of the need to be careful in the use of antibiotics. Cystine stones occurs in individuals with the relatively rare inherited defect of urinary function causing cystinuria. .
References ABDEL-HALIM,R.E.,AL-SIBAAI,A.,andBAGHLFF,A.O.Ionicassociationswithin 460non-infectionurinarystones.Scand.J.Urol.Nephrol.,27:155-162.1993 ABDEL-HALIM,R.andHARDLY,M.J.:Theproblemofurinarystonesinthewestern regionofSaudiArabia.SaudiMed.J.7:394-401.1986 ABOMELLAH,M.S.,ABDULLAH,A.A.,andARNOLD,J.UrolithiasisinSaudiArabia. ŠUrology,35:31-34.1990. AL-NAAM,L.M.,BAQIR,Y.,RASOUL,H.,SUSAN,L.P.,ALKHADDAR,M.,The incidenceandcompositionofurinarystonesinsouthernIraq.SaudiMed.J.8:456-461. 1987. ANDERSOND.A.Environemntalfactorsintheaetiologyofuralithiasis.In:Cifuentes DELATTEL,.RAPADOA.,HODGKINSONA.,Eds.Proceedingsofinternational symposiumonreanlstoneresearchBasel:Karger,130-144.1972 ANDERSON,D.A.,AsurveyoftheincidenceofurolithiasisinNorwayfrom1853to 1966.J.OsloCyHosp.16:10-14.1966. DRACH,G.W.Urinarylithiasis.In:HarrisonJ.H.,GittesR.F,PerlmutterA.D.,Stamey T.A.,WalshP.C.eds.Compbell'surology,Vol.1.Eastbourne:WBSaunders,779- 878.1978 FELLSTROM,B.,DANLIELSON,B.G.,KARLSTROM,B.,LITHELL,H.,LUNGHALL S.,VESSBYB.,WIDE,L.Effectsofhighintakeofdietraryanimalproteinonmineral metabolismandurinarysupersaturationofcalciumoxalateinrenalstoneformers.Br.J. Urol.56:263-269, 1986. GRASESF.,MILLANA.,CONTE,A.Productionofcalciumoxalatemonohydrate,dihy- drateortihydrate.Acomparitivestudy.UrolRes.18:17-25.1990. HAMMOUDA.F.,EL-AsSKARYM,A.,BADT,M.,IBRAHIMF.Mineralogicalcomposi- tionofEgyptianurinarycalculi,TantaMed.J.1:1-27,1973 HESEEA.,BERGW.,SCHNEIDERH.J.,HEINZSCHE.Acontributiontotheformation mechanismofcalciumoxaltaeurinarycalculi.IIInvitroexperimentsconcerningthe theoryoftheformationofwhewelliteandweddelliteurinarycalculi.UrolRes.4:157- 160.1976. HERRING,L.C.Observationsontheanalysisoftenthousandurinarycalculus.J.Urol. 88:545-555.1962. HODGKINSON,A.,MARSHALL,R.W.Changesinthecompositionofurinarytract stones.Invest.Urol.13:131-137.1975 KASSIMIM.,ABDEL-HALIMR.,HARDYM.Theproblemofurinarystonesinthe westernregionofSaudiArabia.SaudiMed.J.7:394-401.1986 MARTINX.,SMITHL.H.,WERNESSP.G.Calciumoxalatedihydrateformationinurine. KidneyIt.25:948-952.1992 OKAT.,YOSHIOKAT.,KOIDET.,TAKAHAM.,SONODAT.Roleofmagnesiumin thegrowthofcalciumoxalatedihydratecrystals.UrolInt.43:89-95.1987. SJOVALL,A.UrinarytractdiseaseintheUnitedArabEmirates:Aradiologicalstudy. Saudi.Med.J.7:143-148.1986 SUTOR,D.J.,WOOLEYS.E.,ILLINGWOTHJ.J.Someaspectsoftheadulturinary stoneprobleminGreatBritainandNorthernIrland.Br.J.Urol.46:275-279.1974. PARKS,J.H.,andCOE,F.L.Anincreasngnumberofcalciumoxalatestoneevents worsenstreatmentoutcome.KidneyInt.45:1722-1730.1994. PIERRATPSA.E.,KHALAFFP.T.,CHENGK.,PSHRAMISK.,JEWETTM.A.S. Clinicalandbiochemicaldifferencesinpatientswithpurecalciumoxalatemonohydrate andcalciumoxalatedihydratekidneystones.J.Urol.151:571-574.1994 PRIENDALL,FrondelC.Studiesinuroliathiasis:I.Thecompositionofurinarycalculi.J. Urol.57:949-991.1947. RANDALL,A.Analysisofurinarycalculithroughtheuseofthepolarizingmicroscope.J. Urol.48:624-649.1942. ROBERTSONW.G.,PEACOCKM.,ThepatternofurinarystonediseaeinLeedsandin theUnitedKingdominrelationtoanimalproteinintakduringtheperiod1960-1980. UrologyInternational37:394-399.1982 WISE,R.O.,andKARK,A.E.,.UrinarycalculiandserumcalciumlevelsinAfricansand Indians.SouthAfricanMed.J.35:47-50.1961 _________________________________________________________ Struvite:NH4MgPO4.6H2O,Dehrnite:(Ca,Na,K)5(PO4,CO3)3(OH) Podolite:(Ca10(PO4)6CO3.H2O,Whewllite:C2CaO4.H2O WeddelliteC2CaO4.2H2O,UriciteC4(NH)2)O2C(NH)2O Ammoniumcalciumphosphatehydrate:NH4Ca2H3(P2O7)2H2O
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