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SILICA STONES IN THE URINARY BLADDER

D. A. LEVISONS. BANIM

P. R. CROCKERD. M. A. WALLACE

Departments of Histopathology, Cardiology, and Urology,St Bartholomew’s Hospital, London

Summary Three urinary bladder stones composed ofpure silicon dioxide (silica) were found in a

patient who had been taking magnesium trisilicate compoundthree times a day for 40 years.

Introduction

URINARY calculi may consist of (1) uric acid and urates, (2)calcium oxalate, or (3) calcium and ammonium magnesiumphosphate. These constitutents are often combined. Calciumand ammonium magnesium phosphate or "mixed" stones arelaid down in alkaline urine and often form a laminated outer

layer on the surfaces of uric-acid and oxalate stones whichform in acid urine. There are also, rarely, stones containingcystine or xanthine. The different types of stone can normallybe identified macroscopically and are often not sent by thesurgeon for chemical analysis. One well-recognisedmacroscopic appearance is that of the spiky calcium-oxalatestone or jackstone (fig. 1). We report here a case in which sucha spiky stone, analysed by X-ray analysis and infra-redspectroscopy, turned out to consist almost entirely of silicondioxide (silica). A likely source of the silica was identified, andpossible implications of the case are discussed.

Case-reportAn 80-year-old man was admitted to St Bartholomew’s Hospital

for insertion of a pacemaker for heart block. During his stay inhospital acute retention of urine developed, and this was treated bytransurethral resection of the prostate and removal of three stonesfrom the bladder. The prostatic fragments proved to be benign. Thestones, together weighing 200 mg, had a distinctive macroscopicappearance (fig. 1) and were thought by all who examined themmacroscopically to be jackstones composed of calcium oxalate.They were sent to the clinical chemistry department for chemicalanalysis, but they seemed chemically inert. They were then sent tothe microanalytical section of the histopathology department forinfra-red spectroscopic analysis and X-ray energy spectroscopic(XES) analysis. Infra-red analysis was done by grinding part of astone with a mortar and pestle and taking 1 - 5 mg of the groundsample to produce a standard 13 mm KBR disc for a Perkin Elmerinfra-red spectrophotometer (model 577). For XES analysis a stonewas placed, first intact and then split in two, in a Jeol 35 CF

Fig. 1-Left, silica stone from our patient. Right, calcium-oxalatejackstone.

Reduced by one-third from x 7.

TABLE I-COMPARISON OF SILICON-DIOXIDE STONE AND

MACROSCOPICALLY SIMILAR CALCIUM-OXALATE JACKSTONE

scanning electron microscope, with Kevex X-ray analyticalequipment attached. Infra-red analysis showed the stone to consistentirely of silicon dioxide. XES showed a reading for pure silicononly (organic elements are not identified by XES).

The Stones

The patient’s stones were compared in a number of wayswith a calcium oxalate jackstone from another patient (table I,figs. 1-3). Figs. 2 and 3 are scanning electron microscopic(SEM) photographs of the two types of stone. There aresubtle differences between the stones in both the macroscopicand the SEM appearances. The spikes of the silica stoneblend with the surface of the stone, whereas those of theoxalate stone appear demarcated from the main body of thestone (figs. 1-3). The surface of the silica stone is smootherthan that of the oxalate stone in he SEM image (figs. 2 and 3).

The Source of Silica

Rereading of the patient’s hospital notes revealed that hehad said he was taking magnesium trisilicate oral compoundBP for indigestion. His current practitioner was unaware thathe was taking this preparation, for the patient had nevercomplained to him of indigestion. On further questioning,the patient admitted to taking one teaspoonful of magnesium

Fig. 2-Scanning electron micrograph of silica stone.

Note the smooth surface and moulding of the spikes to the surface. Reducedby one-third from x 40.

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Fig. 3-Scanning electron micrograph of calcium-oxalate jackstone.Note the rougher surface and angular junction of the spike with the surface.

Reduced by one-third from x 40.

trisilicate oral compound BP dissolved in a glass of waterafter every meal since February, 1941-i.e., three times perday for over forty years.Each gram of magnesium trisilicate oral compound BP is

composed of 250 mg of magnesium trisilicate, 250 mg ofchalk, 250 mg of heavy magnesium carbonate, and 250 mg ofsodium bicarbonate. One heaped teaspoon contains 4’ 0 g ofthe compound and, thus, 1 - 0 g of pure magnesium trisilicate.The quantities of the compound, of pure magnesiumtrisilicate, and of silicon dioxide (Si02, silica) which thepatient had ingested are summarised in table II. The

quantities of silica excreted in the urine by our patient (table11) are calculated from the finding that ingestion of

magnesium trisilicate containing a total of 9 - 2 g of silicaincreased silica excretion in the urine by 484 mg on average. IIn other words, they appeared to excrete in the urine 5 - 3% ofthe orally ingested dose of silica.

Discussion

Compounds of silicon are not, as is still widely thought,substances that are entirely foreign to human metabolism.Silica is a normal metabolite, absorbed from the

gastrointestinal tract, present in the blood, and in normalsubjects present in the urine in concentrations of about 10 mgper day.2 It is present in the urine in amounts proportional tothat in the diet-vegetables, whole grains (husks), and sea-food all containing significant quantities of silica.

Silica stones in the urinary tract are, however, seldomreported. One report3 describes a patient who ingested a totalof 19’ 162 kg of magnesium trisilicate compound in a three-year period and produced a single urinary bladder stone ofsilica weighing 8 mg. Our patient ingested 175-0 kg over a40-year period and produced three silica stones in the urinarybladder totalling 200 mg in weight.

TABLE II-QUANTITIES OF MAGNESIUM TRISILICATE AND SILICA

INGESTED AND SILICA EXCRETED IN URINE BY OUR PATIENT

The fact that silica stones in the urinary bladder are soseldom recognised does not necessarily mean that they areexceptionally rare. We know that many stones removed bysurgeons from the urinary tract are not sent for analysis, andalso that stones which cannot be analysed chemically are notroutinely passed on for infra-red and XES analysis. Thestones in our patient might well have been thought onmacroscopic grounds to be calcium-oxalate stones.That our patient had taken such a large total amount of

magnesium trisilicate does not mean that such large amountsare necessary for the production of silica stones in the urinarytract, since the patient in the other case-report quoted3 hadtaken only about 19% of the total dose taken by our patient.This case reminds us of how easily and commonly silicon

gets into the blood; for it can only be via the bloodstream thatthe silicon travels from the gastrointestinal tract to the

urinary tract. This may explain the not-infrequent finding,with XES, of silicon in tissues in various parts of the body.We often find silicon, for example, in the granulomatouslesions of sarcoidosis and in Kveim-test biopsy specimens(D. A. Levison P. R. Crocker, unpublished). Whether thesilicon has a role in the pathogenesis of these lesions or ismerely an epiphenomenon remains to be determined.We thank Dr H. Isenberg, the patient’s general practitioner, for his

cooperation and Miss Helen Trussler for typing the manuscript.Correspondence should be addressed to D. A. L., Department of

Histopathology, St Bartholomew’s Hospital, London EC1A 7BE.

REFERENCES

1. Page RC, Heffner RR, Frey A. Urinary excretion of silica in humans following oraladministration of magnesium trisilicate. Am J Dig Dis 1941; 8: 13-15.

2. King EJ, Stantial H. Biochemistry of silicic acid; microdetermination of silica. Biochem J1933; 27: 990-1001.

3. Herman JR, Goldberg AS. New type of urinary calculus caused by antacid therapy.JAMA 1960; 174: 1206-07.

SILENT PYONEPHROSIS AS A CAUSE OFCHRONIC ILL-HEALTH

DAVID KIRK*

Department of Urology, Bristol Royal Infirmary andSouthmead Hospital, Bristol

Summary 8 patients who presented with generaldebility but without symptoms indicative of

primary renal disease are reviewed. The clinical picture andpreliminary investigations suggested underlying malignantdisease, but in each case the cause proved to be a

pyonephrosis. All the patients returned to good health afternephrectomy. The possibility of pyonephrosis should beconsidered in any patient with chronic ill-health of uncertaincause.

Introduction

THE doctor treating a patient with symptoms and signssuggestive of disseminated malignant disease must alwaysconsider that the condition may be due to some other,curable, cause. This was the case with the 8 patientspresented here, who were ultimately found to have chronicpyonephrosis amenable to surgery.

Patients

4 of these patients were seen personally over a 30-month period.The other 4 were identified retrospectively with the aid of thepathology department records. The 8 patients probably represent

*Present address: Department of Urology, Royal Infirmary, Glasgow.