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Crystal growth in bile
Prog. Crys~/Growth Chafer. 1981, Voi. 4, pp. 47 - ES. © Pergamon Prels Ltd. Printed in Great Britain
0146 - ~_'~__/81/0601 - 00474)~.00/0
CRYSTAL GROWTH IN BILE D. June Sutor Oqmamnantof ~ ,
univer~ CoUegeLot,don
20 GonJon Street, London WCIH OAJ
($ubrrdm~ 11~ March 1S81)
ABSTRACT C r y s t a l gro~'ch f r e q u e n t l y o c c u r s i n b i l e , r e s u l t i n g u s u a l l y in the formation of gallstones. From p a t i e n t t o p a t i e n t , t h e s e v a r y i n number, s i z e , c o l o u r and s h a p e , a s w e l l a s i n c o m p o s i t i o n . C h o l e s t e r o l i s t h e mast common c o n s t i t u e n t , b u t certain calcium salts, notably calcium carbonate, are frequently present. F a c t o r s which can c o n t r i b u t e t o t h e c r y s t a l l i s a t i o n of bile are discussed, together with those resultlng in the transferrence o f t i n y n u c l e i i n t o t h e complex s t r u c t u r e s o f g a l l s t o n e s . Some o f t h e s e may be c r y s t a l a g g r e g a t i o n , o v e r g r o w t h and e p l t a x y w h i c h may o r may n o t t a k e p a r t i n a g e l which i s t h e m a t r i x o f g a l l s t o n e s .
1.
INTRODUCTION
Crystal growth frequently occurs in bile resulting usually in the formation of gallstones in the gallbladder. Such s t o n e s can r e a m i n ' s i l e n t ' n o t g i v i n g any symptoms t h r o u g h o u t t h e personWs l i f e . However, s h o u l d a s t o n e move o u t o f t h e g a l l b l a d d e r and become t r a p p e d i n a d u c t , c h o l i c , j a u n d i c e o r o t h e r u n p l e a s a n t symptoms may n e c e s s i t a t e s u r g i c a l i n t e r v e n t i o n . I n England and Wales i n 1972, a b o u t 33,000 p e o p l e underwent such s u r g e r y . G a l l s t o n e d i s e a s e i s a p r o b l e s o£ c o n s i d e r a b l e m a s n i t u d e n o t o n l y i n t h e s e c o u n t r i e s b u t a l s o i n a l l W e s t e r n i s e d c o u n t r i e s and many o t h e r s a s w e l l . The c o s t i n human s u f f e r i n g , h o s p i t a l i z a t i o n , s u r g e r y and l o s t p r o d u c t i v i t y , and a l s o t h e c l i n i c a l b u r d e n c a n n o t be e s t i m a t e d . 2.
THE MEDIUM - BILE
B i l e i s s e c r e t e d by t h e l i v e r and i s r e f e r r e d t o a s h e p a t i c b i l e . This is a l i g h t g o l d e n f l u i d which t r a v e l s down t h e coumon b i l e d u c t end c y s t i c d u c t t o t h e ga1161edder where i t i s s t o r e d and becomes known a s s a l l b l e d d e r b i l e . D u r i n g s t o r a s e i t i s c o n c e n t r a t e d by t h e a b s o r p t i o n a c r o s s t h e g a l l b l a d d e r w a l l 47
48
D. June Sutor o f an i s o t o n i c sodium c h l o r i d e / s o d i u m b i c a r b o n a t e s o l u t i o n . The g a l l b l a d d e r i s impermeable to most constitutents which become concentrated about five times or more. Consequently this bile is much darker and denser, and it can be extremely viscous if mucus is present as it is in many cases of gallstone disease. An average concentration for the main constituents of normal gallbladder bile is given in Table i (I). T a b l e I . A v e r a g e c o m p o s i t i o n o f normal g a l l b l a d d e r b i l e Sodium (mmol/l)
210
Bile salts (mmol/l)
300
Bilirubin (mg/lOOml)
300
P o t a s s i u m (mmol/l)
13
Calcium (mmol/l)
Ii
Cholesterol (mg/IOOml)
C h l o r i d e (mmol/l)
25
Lecithin (mg/IOOml)
B i c a r b o n a t e (mmol/1)
10
Protein (mg/lOOml)
Bile serves as a means of excreting but its main function is to help in meals the gastrointestinal hormone, circulation and among other things, thus expulsion of its contents into
500 3000 280
certain unwanted metabolites from the body, the digestion of fat and protein. During cholecystokinin, is secreted into the causes contraction of the gallbladder and the gastrointestinal tract.
When hepatic bile enters the gallbladder, it does not mix immediately with any concentrated bile present, and in fact gallbladder bile never becomes completely homogeneous. Campbell and Burton (2) and Tera (3) have shown it tends to stratify into layers according to specific gravity, the heaviest being in the lowest part of the gallbladder. This part can vary depending on whether the person is standing up or lying down. The former workers reported an abrupt change in composition from one layer to the next, but Tera thought that the change was more gradual. In e v e n normal g a l l b l a d d e r s i t i s p o s s i b l e f o r some of t h e b i l e t o r e m a i n s t a t i c b e c a u s e o f t h i s l a y e r i n g , and b e c a u s e of t h e n a t u r a l i n a b i l i t y of t h e g a l l b l a d d e r to empty i t s e l f c o m p l e t e l y , b u t t h i s r e s i d u u m may not r e m a i n f o r long. 3.
THE CRYSTALLINE PRODUCT - GALLSTONES
3.1. Description G a l l s t o n e s c o n s i s t p r e d o m i n a n t l y o f c r y s t a l l i n e m a t e r i a l and a r e formed a l m o s t i n v a r i a b l y in the g a l l b l a d d e r . W i t h i n a g a l l b l a d d e r t h e r e may be o n l y one s t o n e p r e s e n t o r t h e r e may be m a l t i p l e s t o n e s p r e s e n t r a n g i n g i n number up t o s e v e r a l thousand ( F i g s . i - 4 ) . M u l t i p l e s t o n e s may become f a c e t e d as a r e s u l t of articulation ( F i g . 3) and o f t e n d i f f e r e n t p o p u l a t i o n groups a r e p r e s e n t (Fig. 3). O c c a s i o n a l l y b i z a r r e shaped s t o n e s a r e found b u t t h e i r f o r m a t i o n r em ai n s a m y s t e r y . F i g u r e 5 shows a b a l l and s o c k e t s t o n e which was composed o f c h o l e s t e r o l and f i l l e d t h e g a l l b l a d d e r . The t h r e e p a r t s move e a s i l y on one another. The p e r f e c t o c t a h e d r o n shown i n F i g . 6 i s composed o f c a l c i t e , a r a g o n i t e and v a t e r i t e and i t i s an e x t r e m e l y r a r e s t o n e . Most g a l l s t o n e s a r e c o l o u r e d y e l l o w , r e d , g r e e n , brown o r b l a c k , o r d i f f e r e n t c o l o u r s may be p r e s e n t i n d i f f e r e n t a r e a s o f t h e same s t o n e . The c o l o u r s r e s u l t from t h e a b s o r p t i o n o f b i l e p i g m e n t s by t h e c r y s t a l l i n e m a t e r i a l o r t h e d e p o s i t i o n of i n s o l u b l e s a l t s of pigment.
C r y s t a l Growth i n B i l e
I
Fig.
49
m
I . S o l i t a i r e g a l l s t o n e o f anhydrous c h o l e s t e r o l c u t i n h a l f t o show t h e r a d i a t i n g c r y s t a l s . S c a l e - lcm.
F i g . 2. M u l t i p l e g a l l s t o n e s ,
slightly
faceted,
of c h o l e s t e r o l
II.
F i g . 3. Two p o p u l a t i o n s of f a c e t e d g a l l s t o n e s . The c o n s t i t u e n t s a n h y d r o u s c h o l e s t e r o l and c h o l e s t e r o l monohydrate a r e p r e s e n t t h r o u g h o u t t h e s t o n e s b u t t h e i n t e r i o r and s u r f a c e a r e a s c o n t a i n some v a t e r i t e and a r a g o ~ i t e . S c a l e s lcm.
D. June Sutor
50
! Fig. 4.
Multiple black stones consisting of apatite, whitlockite and aragonite.
Fig. 5.
Ball and socket stone composed of anhydrous cholesterol, cholesterol monohydrate and cholesterol If.
F i g . 6. An u n u s u a l g a l l s t o n e of a l m o s t p e r f e c t o c t a h e d r a l symmetry. The c r y s t a l l i n e c o n s t i t u e n t s a r e c a l c i t e , aragonite and vaterite. The greatest dimension i s 2cm. ( Reproduced by p e r m i s s i o n of th~ E d i t o r and P u b l i s h e r of S c i e n c e , S c i e n c e 159, I l l 3 (1968). C o p y r i g h t 1968 by t h e American A s s o c i a t i o n f o r the Advancement of S c i e n c e .
Crystal Growth in Bile
Fig.
Fig.
7.
I n t e r i o r o f a g a l l s t o n e showing w h i t e beads of a c a l c i u m p a l m i t a t e , some d e p o s i t e d i n a c e n t r a l f i s s u r e . The i n t e r i o r c o n s i s t s of bands o f r a d i a t i n g anhydrous c h o l e s t e r o l c r y s t a l s and t h e compact s u r f a c e band o f anhydrous c h o l e s t e r o l and v a t e r i t e . Stone d i m e n s i o n s 1.O x l . l c m .
8. S c a n n i n g e l e c t r o n m i c r o s c o p e p i c t u r e o f beads o f c a l c i u m p a l m i t a t e on c h o l e s t e r o l . Nagniflcation = x55. ( Reproduced by k i n d p e r m i s s i o n o f Dr. U. W o s i e w i t z ) .
51
52
D. June Sutor
When a stone is cut carefully in half, its internal structure can be examined. The centre of the stone is assumed to be the nucleus on which further growth has occurred, but that may not always be the case. Several small stones may be joined together and each one would have a nucleus. The author has also cracked open stones to find a crystalline shell full of bile. The centre of conventional stones is almost invariably pigmented and sometimes the centre may be a hole with pigment staining the material around the edges. The material in the interior of the stone may show a wide variety of textures (see Section 3.3) and sometimes there are fissures present on this exposed interior (Fig. 7). The surface of the stone is almost always a compact layer of material (Fig. 7). 3.2.
Composition
The different compounds that can crystallise from bile are shown in Table 2 together with their relative abundance in stones from 331 patients (4). These constitutents can be broadly divided into cholesterols and calcium salts. Stones Table 2.
The crystalline constituents and their relative abundance in a collection of gallstones from 331 patients
Constituent Anhydrous
% amount
cholesterol
52.3
Cholesterol monohydrate
16.0
Vaterite
6.4
Calcium palmitate
5.9
Aragonite
4.6
Calcite
4.1
Cholesterol II*
2.7
Apatite
2.4
Calcium bilirubinate
1.8
Whitlockite
0.4
Palmitic acid
O.I
Artefacts, unidentified materlal
3.3
Cholesterol II is a form of
anhydrous cholesterol
are not usually composed of one constitutent and a mixture of several different compounds can be p r e s e n t . . A very simple classification of gallstones according to composition is given in Table 3 and this shows that only 43% of the gallstones were pure cholesterol ones (5). Table 3. Classification of 578 gallstones based on composition Stone composition Cholesterol Cholesterol + calcium salts Calcium salts Amorphous and unidentified material
No. of stones 249 242 77 IO
% 43 42 13 2
Crystal Growth in Bile
The f o r m a t i o n o f c a l c i u m s a l t s
i s p l a y i n g an i n c r e a s i n g r o l e i n g a l l s t o n e
5~
disease.
Some amorphous m a t e r i a l may a l s o be p r e s e n t i n g a l l s t o n e s . Most p i ~ n e n t i s amorphous and t h e most common o n e , b i l i r u b i n , has p r o b a b l y b e e n a b s o r b e d b y t h e crystalline material. The b l a c k pigment which u s u a l l y a c c o m p a n i e s many o f t h e c a l c i u m s a l t s h a s p r e c i p i t a t e d from b i l e and i s l i k e l y t o be a p o l y m e r ( 5 ) . A l l g a l l s t o n e s i r r e s p e c t i v e o f t h e i r c o m p o s i t i o n a p p e a r t o c o n t a i n an amorphous o r g a n i c m a t r i x o f m u c o p o l y s a c c h a r i d e ( 5 , 7 ) whose s t r u c t u r e i s c l o s e l y r e l a t e d t o that of the gallstone (see Section 3.3). 3.3. T e x t u r e
G a l l s t o n e s v a r y c o n s i d e r a b l y i n t h e t e x t u r e of the m a t e r i a l p r e s e n t . They may be c o n g l o m e r a t e s o f f i n e - o r c o a r s e - g r a l n e d powders, a g g r e g a t e s o f s i n g l e crystals or mixtures of several textures. I n many t h e r e a r e l a m i n a t e d bands o f fine-grained material. The c h o l e s t e r o l s f r e q u e n t l y o c c u r a s l a r g e c r y s t a l s which r a d i a t e from t h e c e n t r e o f t h e s t o n e ( F i g . 1 ) . C h o l e s t e r o l may a l s o o c c u r a s a g g r e g a t e s o f s m a l l c r y s t a l s o r be d e p o s i t e d i n a c l o s e - p a c k e d band ( F i g . 7 ) . The s t r u c t u r e and t e x t u r e o f s t o n e s o f c a l c i u m s a l t s have b e e n d e s c r i b e d i n d e t a i l e l s e w h a r e ( 8 ) . These s t o n e s u s u a l l y c o n t a i n v a r y i n g amounts o f t h e amorphous b l a c k p i ~ e n t and a r e t h e r e f o r e d a r k i n c o t o u r ( F i g . 4 ) . Calcium c a r b o n a t e , i n p a r t i c u l a r a r a g o n i t e , forms v e r y h a r d s t o n e s w h l c h m a y have s m a l l s p i k e s p r o t r u d i n g from the surface. Calcium p h o s p h a t e s t o n e s may have s u r f a c e n o d u l e s . The r a r e calcium palmitate stonesare l a m i n a t e d t h r o u g h o u t and f r a g m e n t e a s i l y i n t o t h e d i f f e r e n t b a n d s . Whereas t h i s m a t e r i a l i s r e d o r brown i n c o l o u r , s m a l l w h i t e b e a d s o f c a l c i u m p a l m i t a t e a r e o f t e n found p a r t i c u l a r l y i n t h e f i s s u r e s ( F i g . 7 ) . These b e a d s have a b e a u t i f u l r o s e t t e s t r u c t u r e ( F i g . 8 ) . The matrix of gallstones has an overall structure related to the texture of the crystalline material with which it is associated. Dissolution of the crystals i n a p p r o p r i a t e s o l v e n t s l e a v e s s m a l l p i e c e s o f n o n - c o h e s l v e m a t r l x from a r e a s composed o f l o o s e c r y s t a l l i n e a g g r e g a t e s i r r e s p e c t i v e o f t h e i r c o m p o s i t i o n . A compact g e l i s o b t a i n e d from d e n s e u s u a l l y l a m i n a t e d a r e a s . Largerediating c r y s t a l s o f c h o l e s t e r o l a p p e a r t o have l i t t l e , if any, matrix. Inlcholesterol s t o n e s , t h e m a t r i x i s o f t e n w h i t e , b u t i t c a n be p i ~ e n t e d g i v i n g a l i g h t o r a n g e o r y e l l o w c o l o u r , sometimes o n l y i n p a r t s . I n s t o n e s composed o n l y o f c a l c i u m s a l t s , t h e m a t r i x i s i n v a r i a b l y p i g m e n t e d by a b l a c k i n s o l u b l e s u b s t a n c e which i s l i k e l y t o be t h e b l a c k amorphous p i g m e n t a l r e a d y m e n t i o n e d , 4.
4.1.
Solubilit~
CRYSTALLISATION FROM BILE
of Constituents
in Bile
B i l e i s a f l u i d which i s n o t r e a d i l y a v a i l a b l e s i n c e no s u r g e o n ofl r e p u t e w i l l a s p i r a t e a normal g a l l b l a d d e r o r p u n c t u r e a b i l e d u c t , Work h a s t h e r e f o r e been confined mainly to bile obtained from patients having their Eallb ,ladders removed. b u t t h i s i s l e a d i n g t o an u n d e r s t a n d i n g o f t h e c o m p o s i t i o n o f b i l e . Bile is a complex f l u i d c o n t a i n i n g many s u b s t a n c e s which a r e v i r t u a l l y i n s o l u b l e i n un aqueous s o l u t i o n . Their solubilities a r e i n c r e a s e d by d i f f e r e n t mechanisms. The most i m p o r t a n t c o n s t i t u e n t , c h o l e s t e r o l , i s k e p t i n s o l u t i o n by a mixed n d c e l l e c o n s i s t i n g o f b i l e s a l t s and l e c i t h i n ( 9 ) . The s o l u b i l i t i e s of the c a l c i u m s a l t s i n t h i s complex f l u i d a r e n o t known, b u t b i l e c o n t a i n s s u b s t a n c e s , p r o b a b l y t h e mixed m i c e l l e s and p r o t e i n s , which i n h i b i ~ i n v i t r o t h e n u c l e a t i o n and c r y s t a l grov~h o f v a t e r l t e (10) and o c t a c a l c i u m p ~ s p - - ~ e ,
54
D. June Sutor
a precursor of apatite
(II).
In s p i t e o f t h e s e and p o s s i b l y o t h e r p r o t e c t i v e mechanisms, s u p e r s a t u r a t i o n f o l l o w e d by n u c l e a t i o n must o c c u r . In p a t i e n t s w i t h p u r e c h o l e s t e r o l g a l l s t o n e s , t h e h e p a t i c b i l e was found t o be s u p e r s a t u r a t e d w i t h c h o l e s t e r o l ( 1 2 ) , and p a t i e n t s w i t h c a l c l u m c a r b o n a t e i n t h e i r g a l l s t o n e s had a r a i s e d l e v e l o f t o t a l CO2 a l s o i n t h e i r h e p a t i c b i l e ( 1 3 ) . Thus a l t h o u g h t h e s o u r c e o f t h e ' a b n o r m a l ' b i l e i s t h e l i v e r , g a l l s t o n e s a r e found i n t h e g a l l b l a d d e r s u g g e s t i n g a d e f i n i t e r o l e f o r t h a t o r g a n i n s t o n e f o r m a t i o n . N u c l e a t i o n may a l s o r e s u l t from c o n d i t i o n s w i t h i n t h e g a l l b l a d d e r i t s e l f . In v i t r o e x p e r i m e n t s (14) have shown t h a t d i f f e r e n c e s i n t h e r a t e of d i f f u s i o n o f d i f f e r e n t c o n s t i t u e n t s a c r o s s t h e i n t e r f a c e s i n s t r a t i f i e d b i l e to which a l a y e r o f w a t e r was added i n one i n s t a n c e and a d i l u t e a r t i f i c i a l b i l e i n a n o t h e r , l e d to t h e f o r m a t i o n o f c h o l e s t e r o l c r y s t a l s a t t h e i n t e r f a c e , and e v e n t u a l l y a s ~ l l stone.
4.2.
Methods of N u c l e i R e t e n t i o n
Once b i l e has n u c l e a t e d and m i c r o c r y s t a l s have formed, mechanisms must be p r e s e n t f o r r e t a i n i n g t h e c r y s t a l s i n t h e g a l l b l a d d e r and p e r p e t u a t i n g t h e i r g r o ~ : h . The g a l l b l a d d e r may t r a p t h e n u c l e i i n a number o f ways. I.
As a r e s u l t o f s t r a t i f i c a t i o n o f b i l e and i n c o m p l e t e e ~ t y l n g g a l l b l a d d e r , a few n u c l e l may be r e t a i n e d .
2.
C r y s t a l s mey become t r a p p e d i n a s m e l l p o c k e t in t h e g a l l b l a d d e r w a l l .
3.
C r y s t a l s may become t r a p p e d i n mucus.
4.3.
of the
Stone Formation
The t r a n s f e r e n c e o f t h e c r y s t a l n u c l e i i n t o complex s t o n e s may t a k e p l a c e i n t h e presence or absence of a gel (the r~ucopolysaccharide). ~ t r i x has been shovm t o be an e s s e n t i a l c o n s t i t u e n t o f most g a l l s t o n e s and i t s s t r u c t u r e i s c l o s e l y r e l a t e d to t h a t of the c r y s t a l l i n e m a t e r i a l . ~omack (15) has s h o ~ t h a t in h a m s t e r s f e d a d i e t l e a d i n g t o t h e f o r m e t i o n o f c h o l e s t e r o l s t o n e s , ~mucus c o l l e c t e d i n s m a l l v i s c i d masses s h o r t l y b e f o r e c h o l e s t e r o l c r y s t a l s a p p e a r e d . F i r s t a s o f t , and l a t e r a compact c h o l e s t e r o l s t o n e was formed. O t h er a u t h o r s r e p o r t e d a p u r e m a t r i x s t o n e which b l o c k e d one o f t h e b i l e d u c t s ( 1 6 ) , but such stones are rare. That c r y s t a l growth always o c c u r s i n a g e l i s c e r t a i n l y n o t well-established. Often the presence of a g a l l s t o n e in the g a l l b l a d d e r causes the g a l l b l a d d e r e p i t h e l i u m t o s e c r e t e mucus, and l a t e r i f n o t e a r l i e r c r y s t a l growth may t a k e p l a c e i n such a medium. Growth o f s t o n e s may o c c u r by d e p o s i t i o n o f m a t e r i a l on t h e n u c l e i from t h e s u p e r s a t u r a t e d b i l e , by a g g r e g a t i o n o f c r y s t a l s o r t i n y s t o n e s and by e p i t a x y . Once s t o n e s b e g i n to grow, t h e a b i l i t y of t h e g a l l b l a d d e r t o c o n t r a c t and e x p e l b i l e may d i ~ n l s h and e v e n t u a l l y s t o p a l t o g e t h e r . Such c o n d i t i o n s p r o v i d e a g r e a t e r d e g r e e o f s t a s i s f o r s t o n e g r o w t h , and s h o u l d t h e g a l l b l a d d e r l o s e c o m p l e t e l y i t s a b i l i t y t o f u n c t i o n , o t h e r c o n s t i t u e n t s such as b i l e s a l t s may p a s s t h r o u g h t h e g a l l b l a d d e r w a l l , and t h e c o m p o s i t i o n o f t h e b i l e changes drastically. 4.4.
Epitaxy
One c u r i o u s f e a t u r e o f g a l l s t o n e s i s t h e r e l a t i v e l y a b r u p t change i n c o m p o s i t i o n which can o c c u r from t i m e t o t i m e d u r i n g growth ( 1 7 ) . ~ r e o v e r in a d i s t i n c t s t o n e band, two d i f f e r e n t compounds may be d e p o s i t e d . L o n s d a l e (18)
Crystal Growth in Bile
55
s u g g e s t e d t h a t e p i t a x y c o u l d a c c o u n t f o r t h e growth and s t r u c t u r e o f g a l l s t o n e s once a s u i t a b l e seed had formed. That e p i t a x y i s p o s s i b l e i s shown i n T a b l e 4 which g i v e s t h e p e r c e n t a g e m i s f i t s on so~e n a t u r a l l y o c c u r r i n g f a c e s of Table 4. Substance
Face
Cholesterol
Possible epltaxy in gallstones
Dimensions of net (~)
% misfit
(O10)
14.OO x 31.38 (90 °)
-
-
(O01)
14.OO x 33.71 (96° )
0
6.6
Calcite
(I0~0)
14.97 x 34.12 (90 ° )
7.O
8.8
Aragonite
(001)
14.88 x 31.88 (90 ° )
6.3
1.6
Vaterite
(IO~0)
14.32 x 33.96 (90° )
2.3
7.3
Apatite
(I120)
13.76 x 32.62 (90 °)
1.6
3.1
c o n s t i t u e n t s whose u n i t c e l l d i m e n s i o n s a r e known. F u r t h e r m o r e t h e r e a r e o t h e r c l o s e r e l a t i o n s between some of t h e o t h e r p o s s i b l e f a c e s . So t h a t e p i t a x y i s i n d e e d l i k e l y and i t would e x p l a i n t h e e a s e w i t h which one s u b s t a n c e a c t s as a s u b s t r a t e f o r a n o t h e r i n s t o n e s . The o r g a n i c m a t r i x may t a k e p a r t i n t h e e p i t a x y , or i t s r o l e may be s e c o n d a r y . 5.
CONCLUSIONS
G a l l s t o n e s can be o b j e c t s o f g r e a t b e a u t y w i t h t h e i r i n t r i c a t e a r r a n g e m e n t s of m a t e r i a l and c o l o u r . No one has y e t succeeded i n growing i n v i t r o , a n y t h i n g r e s e m b l i n g t h e complex a r r a n g e m e n t o f m a t e r i a l produced i n v i v o . As w e l l as many f a c t o r s d e s c r i b e d h e r e which i n f l u e n c e g a l l s t o n e f o r m a t x o n , o t h e r s may a l s o be i n v o l v e d . These c o u l d i n c l u d e p r e s s u r e , a g i t a t i o n and, i n t h e e a r l y s t a g e s of s t o n e f o r ~ t l o n , t h e flow of b i l e i n and o u t of t h e g a l l b l a d d e r l i k e n i n g the system to a continuous c r y s t a l l i s e r . The probles~ i s a f a s c i n a t i n g and c h a l l e n g i n g o n e , and a g r e a t d e a l of work i n t h e f i e l d o f c r y s t a l growth i s n e c e s s a r y b e f o r e t h e f o r m a t i o n o f such complex s t r u c t u r e s i s f u l l y u n d e r s t o o d .
REFERENCES 1.
I . A. D. B o u c h i e r and J . W. F r e s t o n ,
2.
B.A.
3.
H. T e r a ,
4.
D. J . S u t o r and S. E. Wooley, Gut 12, 55 (1971).
5.
D. J . S u t o r , The c o m p o s i t i o n of g a l l s t o n e s . I n : G a l l s t o n e s , Eds. H. M. F i s h e r , C. A. Goresky, E. A. S h e f f e r and S. M. S t r a s b e r g , Plenum P r e s s , New York and London (1979).
6.
N. A. Womack, R. Zeppa and G. L. I r v i n , Ann. Sur&. 157, 670 (1963).
7.
D. J . S u t o r and S. E. Wooley, Gut 15, 487 (1974).
8.
D.J.
Campbell and A. C. B u r t o n , Acta c h i r .
The I ~ n c e t , 340 (1968).
s u r g . G~nec. O b s t e t . 888, 731 (1949).
Scand. Supplemantum 25§, 1 (1960).
S u t o r and S. E. Wooley, Gut 1_.44, 215 (1973).
56
9.
D. June Sutor
D. M. S m a l l , G a s t r P e n t e r o l o g y 5_~2, 607 (1967).
10.
D. J . S u t o r and J . M. P e r c i v a l ,
C l i n . chim. Acta 89, 479 (1978).
ii.
D. J. Sutor and J. M. Percival, Gut 17, 506 (1974).
12.
W. H. Admirand and D. M. Small, J. clin. Invest. 47, 1043 (1968).
13.
D.J.
14.
P. Fitz-James and A. C. Burton, Canad. J. Res. E 27, 309 (1949).
15.
N. A. Womack, Surg. Gynec. Obstet. 133, 937 (1971).
16.
H.J.
Hanm~rman, B. A. Shatz and R. G. Evens, Radiology 124, 31 (1977).
17.
D.J.
Sutor and S. E. Wooley, Gut 15, 130 (1974).
18,
K. Lonsdale, Nature 217, 56 (1968).
Sutor and L. I. Wilkie, Gut 19, 220 (1978).
Crystal Growth in Bile
57
THE AUTHOR
D. June Sutor The author is a graduate in chemistry and crystallography from the University of New Zealand and University of Cambridge. She has spent the last 14 years studying the composition and structure of urinary stones and gallstones by X-ray diffraction, and investigating the composition of urine and bile from which growth of this crystalline material has occurred. Since becoming partially-sighted in 1979, she has become interested in theoretical aspects of stone growth.
0146 - ~_'~__/81/0601 - 00474)~.00/0
CRYSTAL GROWTH IN BILE D. June Sutor Oqmamnantof ~ ,
univer~ CoUegeLot,don
20 GonJon Street, London WCIH OAJ
($ubrrdm~ 11~ March 1S81)
ABSTRACT C r y s t a l gro~'ch f r e q u e n t l y o c c u r s i n b i l e , r e s u l t i n g u s u a l l y in the formation of gallstones. From p a t i e n t t o p a t i e n t , t h e s e v a r y i n number, s i z e , c o l o u r and s h a p e , a s w e l l a s i n c o m p o s i t i o n . C h o l e s t e r o l i s t h e mast common c o n s t i t u e n t , b u t certain calcium salts, notably calcium carbonate, are frequently present. F a c t o r s which can c o n t r i b u t e t o t h e c r y s t a l l i s a t i o n of bile are discussed, together with those resultlng in the transferrence o f t i n y n u c l e i i n t o t h e complex s t r u c t u r e s o f g a l l s t o n e s . Some o f t h e s e may be c r y s t a l a g g r e g a t i o n , o v e r g r o w t h and e p l t a x y w h i c h may o r may n o t t a k e p a r t i n a g e l which i s t h e m a t r i x o f g a l l s t o n e s .
1.
INTRODUCTION
Crystal growth frequently occurs in bile resulting usually in the formation of gallstones in the gallbladder. Such s t o n e s can r e a m i n ' s i l e n t ' n o t g i v i n g any symptoms t h r o u g h o u t t h e personWs l i f e . However, s h o u l d a s t o n e move o u t o f t h e g a l l b l a d d e r and become t r a p p e d i n a d u c t , c h o l i c , j a u n d i c e o r o t h e r u n p l e a s a n t symptoms may n e c e s s i t a t e s u r g i c a l i n t e r v e n t i o n . I n England and Wales i n 1972, a b o u t 33,000 p e o p l e underwent such s u r g e r y . G a l l s t o n e d i s e a s e i s a p r o b l e s o£ c o n s i d e r a b l e m a s n i t u d e n o t o n l y i n t h e s e c o u n t r i e s b u t a l s o i n a l l W e s t e r n i s e d c o u n t r i e s and many o t h e r s a s w e l l . The c o s t i n human s u f f e r i n g , h o s p i t a l i z a t i o n , s u r g e r y and l o s t p r o d u c t i v i t y , and a l s o t h e c l i n i c a l b u r d e n c a n n o t be e s t i m a t e d . 2.
THE MEDIUM - BILE
B i l e i s s e c r e t e d by t h e l i v e r and i s r e f e r r e d t o a s h e p a t i c b i l e . This is a l i g h t g o l d e n f l u i d which t r a v e l s down t h e coumon b i l e d u c t end c y s t i c d u c t t o t h e ga1161edder where i t i s s t o r e d and becomes known a s s a l l b l e d d e r b i l e . D u r i n g s t o r a s e i t i s c o n c e n t r a t e d by t h e a b s o r p t i o n a c r o s s t h e g a l l b l a d d e r w a l l 47
48
D. June Sutor o f an i s o t o n i c sodium c h l o r i d e / s o d i u m b i c a r b o n a t e s o l u t i o n . The g a l l b l a d d e r i s impermeable to most constitutents which become concentrated about five times or more. Consequently this bile is much darker and denser, and it can be extremely viscous if mucus is present as it is in many cases of gallstone disease. An average concentration for the main constituents of normal gallbladder bile is given in Table i (I). T a b l e I . A v e r a g e c o m p o s i t i o n o f normal g a l l b l a d d e r b i l e Sodium (mmol/l)
210
Bile salts (mmol/l)
300
Bilirubin (mg/lOOml)
300
P o t a s s i u m (mmol/l)
13
Calcium (mmol/l)
Ii
Cholesterol (mg/IOOml)
C h l o r i d e (mmol/l)
25
Lecithin (mg/IOOml)
B i c a r b o n a t e (mmol/1)
10
Protein (mg/lOOml)
Bile serves as a means of excreting but its main function is to help in meals the gastrointestinal hormone, circulation and among other things, thus expulsion of its contents into
500 3000 280
certain unwanted metabolites from the body, the digestion of fat and protein. During cholecystokinin, is secreted into the causes contraction of the gallbladder and the gastrointestinal tract.
When hepatic bile enters the gallbladder, it does not mix immediately with any concentrated bile present, and in fact gallbladder bile never becomes completely homogeneous. Campbell and Burton (2) and Tera (3) have shown it tends to stratify into layers according to specific gravity, the heaviest being in the lowest part of the gallbladder. This part can vary depending on whether the person is standing up or lying down. The former workers reported an abrupt change in composition from one layer to the next, but Tera thought that the change was more gradual. In e v e n normal g a l l b l a d d e r s i t i s p o s s i b l e f o r some of t h e b i l e t o r e m a i n s t a t i c b e c a u s e o f t h i s l a y e r i n g , and b e c a u s e of t h e n a t u r a l i n a b i l i t y of t h e g a l l b l a d d e r to empty i t s e l f c o m p l e t e l y , b u t t h i s r e s i d u u m may not r e m a i n f o r long. 3.
THE CRYSTALLINE PRODUCT - GALLSTONES
3.1. Description G a l l s t o n e s c o n s i s t p r e d o m i n a n t l y o f c r y s t a l l i n e m a t e r i a l and a r e formed a l m o s t i n v a r i a b l y in the g a l l b l a d d e r . W i t h i n a g a l l b l a d d e r t h e r e may be o n l y one s t o n e p r e s e n t o r t h e r e may be m a l t i p l e s t o n e s p r e s e n t r a n g i n g i n number up t o s e v e r a l thousand ( F i g s . i - 4 ) . M u l t i p l e s t o n e s may become f a c e t e d as a r e s u l t of articulation ( F i g . 3) and o f t e n d i f f e r e n t p o p u l a t i o n groups a r e p r e s e n t (Fig. 3). O c c a s i o n a l l y b i z a r r e shaped s t o n e s a r e found b u t t h e i r f o r m a t i o n r em ai n s a m y s t e r y . F i g u r e 5 shows a b a l l and s o c k e t s t o n e which was composed o f c h o l e s t e r o l and f i l l e d t h e g a l l b l a d d e r . The t h r e e p a r t s move e a s i l y on one another. The p e r f e c t o c t a h e d r o n shown i n F i g . 6 i s composed o f c a l c i t e , a r a g o n i t e and v a t e r i t e and i t i s an e x t r e m e l y r a r e s t o n e . Most g a l l s t o n e s a r e c o l o u r e d y e l l o w , r e d , g r e e n , brown o r b l a c k , o r d i f f e r e n t c o l o u r s may be p r e s e n t i n d i f f e r e n t a r e a s o f t h e same s t o n e . The c o l o u r s r e s u l t from t h e a b s o r p t i o n o f b i l e p i g m e n t s by t h e c r y s t a l l i n e m a t e r i a l o r t h e d e p o s i t i o n of i n s o l u b l e s a l t s of pigment.
C r y s t a l Growth i n B i l e
I
Fig.
49
m
I . S o l i t a i r e g a l l s t o n e o f anhydrous c h o l e s t e r o l c u t i n h a l f t o show t h e r a d i a t i n g c r y s t a l s . S c a l e - lcm.
F i g . 2. M u l t i p l e g a l l s t o n e s ,
slightly
faceted,
of c h o l e s t e r o l
II.
F i g . 3. Two p o p u l a t i o n s of f a c e t e d g a l l s t o n e s . The c o n s t i t u e n t s a n h y d r o u s c h o l e s t e r o l and c h o l e s t e r o l monohydrate a r e p r e s e n t t h r o u g h o u t t h e s t o n e s b u t t h e i n t e r i o r and s u r f a c e a r e a s c o n t a i n some v a t e r i t e and a r a g o ~ i t e . S c a l e s lcm.
D. June Sutor
50
! Fig. 4.
Multiple black stones consisting of apatite, whitlockite and aragonite.
Fig. 5.
Ball and socket stone composed of anhydrous cholesterol, cholesterol monohydrate and cholesterol If.
F i g . 6. An u n u s u a l g a l l s t o n e of a l m o s t p e r f e c t o c t a h e d r a l symmetry. The c r y s t a l l i n e c o n s t i t u e n t s a r e c a l c i t e , aragonite and vaterite. The greatest dimension i s 2cm. ( Reproduced by p e r m i s s i o n of th~ E d i t o r and P u b l i s h e r of S c i e n c e , S c i e n c e 159, I l l 3 (1968). C o p y r i g h t 1968 by t h e American A s s o c i a t i o n f o r the Advancement of S c i e n c e .
Crystal Growth in Bile
Fig.
Fig.
7.
I n t e r i o r o f a g a l l s t o n e showing w h i t e beads of a c a l c i u m p a l m i t a t e , some d e p o s i t e d i n a c e n t r a l f i s s u r e . The i n t e r i o r c o n s i s t s of bands o f r a d i a t i n g anhydrous c h o l e s t e r o l c r y s t a l s and t h e compact s u r f a c e band o f anhydrous c h o l e s t e r o l and v a t e r i t e . Stone d i m e n s i o n s 1.O x l . l c m .
8. S c a n n i n g e l e c t r o n m i c r o s c o p e p i c t u r e o f beads o f c a l c i u m p a l m i t a t e on c h o l e s t e r o l . Nagniflcation = x55. ( Reproduced by k i n d p e r m i s s i o n o f Dr. U. W o s i e w i t z ) .
51
52
D. June Sutor
When a stone is cut carefully in half, its internal structure can be examined. The centre of the stone is assumed to be the nucleus on which further growth has occurred, but that may not always be the case. Several small stones may be joined together and each one would have a nucleus. The author has also cracked open stones to find a crystalline shell full of bile. The centre of conventional stones is almost invariably pigmented and sometimes the centre may be a hole with pigment staining the material around the edges. The material in the interior of the stone may show a wide variety of textures (see Section 3.3) and sometimes there are fissures present on this exposed interior (Fig. 7). The surface of the stone is almost always a compact layer of material (Fig. 7). 3.2.
Composition
The different compounds that can crystallise from bile are shown in Table 2 together with their relative abundance in stones from 331 patients (4). These constitutents can be broadly divided into cholesterols and calcium salts. Stones Table 2.
The crystalline constituents and their relative abundance in a collection of gallstones from 331 patients
Constituent Anhydrous
% amount
cholesterol
52.3
Cholesterol monohydrate
16.0
Vaterite
6.4
Calcium palmitate
5.9
Aragonite
4.6
Calcite
4.1
Cholesterol II*
2.7
Apatite
2.4
Calcium bilirubinate
1.8
Whitlockite
0.4
Palmitic acid
O.I
Artefacts, unidentified materlal
3.3
Cholesterol II is a form of
anhydrous cholesterol
are not usually composed of one constitutent and a mixture of several different compounds can be p r e s e n t . . A very simple classification of gallstones according to composition is given in Table 3 and this shows that only 43% of the gallstones were pure cholesterol ones (5). Table 3. Classification of 578 gallstones based on composition Stone composition Cholesterol Cholesterol + calcium salts Calcium salts Amorphous and unidentified material
No. of stones 249 242 77 IO
% 43 42 13 2
Crystal Growth in Bile
The f o r m a t i o n o f c a l c i u m s a l t s
i s p l a y i n g an i n c r e a s i n g r o l e i n g a l l s t o n e
5~
disease.
Some amorphous m a t e r i a l may a l s o be p r e s e n t i n g a l l s t o n e s . Most p i ~ n e n t i s amorphous and t h e most common o n e , b i l i r u b i n , has p r o b a b l y b e e n a b s o r b e d b y t h e crystalline material. The b l a c k pigment which u s u a l l y a c c o m p a n i e s many o f t h e c a l c i u m s a l t s h a s p r e c i p i t a t e d from b i l e and i s l i k e l y t o be a p o l y m e r ( 5 ) . A l l g a l l s t o n e s i r r e s p e c t i v e o f t h e i r c o m p o s i t i o n a p p e a r t o c o n t a i n an amorphous o r g a n i c m a t r i x o f m u c o p o l y s a c c h a r i d e ( 5 , 7 ) whose s t r u c t u r e i s c l o s e l y r e l a t e d t o that of the gallstone (see Section 3.3). 3.3. T e x t u r e
G a l l s t o n e s v a r y c o n s i d e r a b l y i n t h e t e x t u r e of the m a t e r i a l p r e s e n t . They may be c o n g l o m e r a t e s o f f i n e - o r c o a r s e - g r a l n e d powders, a g g r e g a t e s o f s i n g l e crystals or mixtures of several textures. I n many t h e r e a r e l a m i n a t e d bands o f fine-grained material. The c h o l e s t e r o l s f r e q u e n t l y o c c u r a s l a r g e c r y s t a l s which r a d i a t e from t h e c e n t r e o f t h e s t o n e ( F i g . 1 ) . C h o l e s t e r o l may a l s o o c c u r a s a g g r e g a t e s o f s m a l l c r y s t a l s o r be d e p o s i t e d i n a c l o s e - p a c k e d band ( F i g . 7 ) . The s t r u c t u r e and t e x t u r e o f s t o n e s o f c a l c i u m s a l t s have b e e n d e s c r i b e d i n d e t a i l e l s e w h a r e ( 8 ) . These s t o n e s u s u a l l y c o n t a i n v a r y i n g amounts o f t h e amorphous b l a c k p i ~ e n t and a r e t h e r e f o r e d a r k i n c o t o u r ( F i g . 4 ) . Calcium c a r b o n a t e , i n p a r t i c u l a r a r a g o n i t e , forms v e r y h a r d s t o n e s w h l c h m a y have s m a l l s p i k e s p r o t r u d i n g from the surface. Calcium p h o s p h a t e s t o n e s may have s u r f a c e n o d u l e s . The r a r e calcium palmitate stonesare l a m i n a t e d t h r o u g h o u t and f r a g m e n t e a s i l y i n t o t h e d i f f e r e n t b a n d s . Whereas t h i s m a t e r i a l i s r e d o r brown i n c o l o u r , s m a l l w h i t e b e a d s o f c a l c i u m p a l m i t a t e a r e o f t e n found p a r t i c u l a r l y i n t h e f i s s u r e s ( F i g . 7 ) . These b e a d s have a b e a u t i f u l r o s e t t e s t r u c t u r e ( F i g . 8 ) . The matrix of gallstones has an overall structure related to the texture of the crystalline material with which it is associated. Dissolution of the crystals i n a p p r o p r i a t e s o l v e n t s l e a v e s s m a l l p i e c e s o f n o n - c o h e s l v e m a t r l x from a r e a s composed o f l o o s e c r y s t a l l i n e a g g r e g a t e s i r r e s p e c t i v e o f t h e i r c o m p o s i t i o n . A compact g e l i s o b t a i n e d from d e n s e u s u a l l y l a m i n a t e d a r e a s . Largerediating c r y s t a l s o f c h o l e s t e r o l a p p e a r t o have l i t t l e , if any, matrix. Inlcholesterol s t o n e s , t h e m a t r i x i s o f t e n w h i t e , b u t i t c a n be p i ~ e n t e d g i v i n g a l i g h t o r a n g e o r y e l l o w c o l o u r , sometimes o n l y i n p a r t s . I n s t o n e s composed o n l y o f c a l c i u m s a l t s , t h e m a t r i x i s i n v a r i a b l y p i g m e n t e d by a b l a c k i n s o l u b l e s u b s t a n c e which i s l i k e l y t o be t h e b l a c k amorphous p i g m e n t a l r e a d y m e n t i o n e d , 4.
4.1.
Solubilit~
CRYSTALLISATION FROM BILE
of Constituents
in Bile
B i l e i s a f l u i d which i s n o t r e a d i l y a v a i l a b l e s i n c e no s u r g e o n ofl r e p u t e w i l l a s p i r a t e a normal g a l l b l a d d e r o r p u n c t u r e a b i l e d u c t , Work h a s t h e r e f o r e been confined mainly to bile obtained from patients having their Eallb ,ladders removed. b u t t h i s i s l e a d i n g t o an u n d e r s t a n d i n g o f t h e c o m p o s i t i o n o f b i l e . Bile is a complex f l u i d c o n t a i n i n g many s u b s t a n c e s which a r e v i r t u a l l y i n s o l u b l e i n un aqueous s o l u t i o n . Their solubilities a r e i n c r e a s e d by d i f f e r e n t mechanisms. The most i m p o r t a n t c o n s t i t u e n t , c h o l e s t e r o l , i s k e p t i n s o l u t i o n by a mixed n d c e l l e c o n s i s t i n g o f b i l e s a l t s and l e c i t h i n ( 9 ) . The s o l u b i l i t i e s of the c a l c i u m s a l t s i n t h i s complex f l u i d a r e n o t known, b u t b i l e c o n t a i n s s u b s t a n c e s , p r o b a b l y t h e mixed m i c e l l e s and p r o t e i n s , which i n h i b i ~ i n v i t r o t h e n u c l e a t i o n and c r y s t a l grov~h o f v a t e r l t e (10) and o c t a c a l c i u m p ~ s p - - ~ e ,
54
D. June Sutor
a precursor of apatite
(II).
In s p i t e o f t h e s e and p o s s i b l y o t h e r p r o t e c t i v e mechanisms, s u p e r s a t u r a t i o n f o l l o w e d by n u c l e a t i o n must o c c u r . In p a t i e n t s w i t h p u r e c h o l e s t e r o l g a l l s t o n e s , t h e h e p a t i c b i l e was found t o be s u p e r s a t u r a t e d w i t h c h o l e s t e r o l ( 1 2 ) , and p a t i e n t s w i t h c a l c l u m c a r b o n a t e i n t h e i r g a l l s t o n e s had a r a i s e d l e v e l o f t o t a l CO2 a l s o i n t h e i r h e p a t i c b i l e ( 1 3 ) . Thus a l t h o u g h t h e s o u r c e o f t h e ' a b n o r m a l ' b i l e i s t h e l i v e r , g a l l s t o n e s a r e found i n t h e g a l l b l a d d e r s u g g e s t i n g a d e f i n i t e r o l e f o r t h a t o r g a n i n s t o n e f o r m a t i o n . N u c l e a t i o n may a l s o r e s u l t from c o n d i t i o n s w i t h i n t h e g a l l b l a d d e r i t s e l f . In v i t r o e x p e r i m e n t s (14) have shown t h a t d i f f e r e n c e s i n t h e r a t e of d i f f u s i o n o f d i f f e r e n t c o n s t i t u e n t s a c r o s s t h e i n t e r f a c e s i n s t r a t i f i e d b i l e to which a l a y e r o f w a t e r was added i n one i n s t a n c e and a d i l u t e a r t i f i c i a l b i l e i n a n o t h e r , l e d to t h e f o r m a t i o n o f c h o l e s t e r o l c r y s t a l s a t t h e i n t e r f a c e , and e v e n t u a l l y a s ~ l l stone.
4.2.
Methods of N u c l e i R e t e n t i o n
Once b i l e has n u c l e a t e d and m i c r o c r y s t a l s have formed, mechanisms must be p r e s e n t f o r r e t a i n i n g t h e c r y s t a l s i n t h e g a l l b l a d d e r and p e r p e t u a t i n g t h e i r g r o ~ : h . The g a l l b l a d d e r may t r a p t h e n u c l e i i n a number o f ways. I.
As a r e s u l t o f s t r a t i f i c a t i o n o f b i l e and i n c o m p l e t e e ~ t y l n g g a l l b l a d d e r , a few n u c l e l may be r e t a i n e d .
2.
C r y s t a l s mey become t r a p p e d i n a s m e l l p o c k e t in t h e g a l l b l a d d e r w a l l .
3.
C r y s t a l s may become t r a p p e d i n mucus.
4.3.
of the
Stone Formation
The t r a n s f e r e n c e o f t h e c r y s t a l n u c l e i i n t o complex s t o n e s may t a k e p l a c e i n t h e presence or absence of a gel (the r~ucopolysaccharide). ~ t r i x has been shovm t o be an e s s e n t i a l c o n s t i t u e n t o f most g a l l s t o n e s and i t s s t r u c t u r e i s c l o s e l y r e l a t e d to t h a t of the c r y s t a l l i n e m a t e r i a l . ~omack (15) has s h o ~ t h a t in h a m s t e r s f e d a d i e t l e a d i n g t o t h e f o r m e t i o n o f c h o l e s t e r o l s t o n e s , ~mucus c o l l e c t e d i n s m a l l v i s c i d masses s h o r t l y b e f o r e c h o l e s t e r o l c r y s t a l s a p p e a r e d . F i r s t a s o f t , and l a t e r a compact c h o l e s t e r o l s t o n e was formed. O t h er a u t h o r s r e p o r t e d a p u r e m a t r i x s t o n e which b l o c k e d one o f t h e b i l e d u c t s ( 1 6 ) , but such stones are rare. That c r y s t a l growth always o c c u r s i n a g e l i s c e r t a i n l y n o t well-established. Often the presence of a g a l l s t o n e in the g a l l b l a d d e r causes the g a l l b l a d d e r e p i t h e l i u m t o s e c r e t e mucus, and l a t e r i f n o t e a r l i e r c r y s t a l growth may t a k e p l a c e i n such a medium. Growth o f s t o n e s may o c c u r by d e p o s i t i o n o f m a t e r i a l on t h e n u c l e i from t h e s u p e r s a t u r a t e d b i l e , by a g g r e g a t i o n o f c r y s t a l s o r t i n y s t o n e s and by e p i t a x y . Once s t o n e s b e g i n to grow, t h e a b i l i t y of t h e g a l l b l a d d e r t o c o n t r a c t and e x p e l b i l e may d i ~ n l s h and e v e n t u a l l y s t o p a l t o g e t h e r . Such c o n d i t i o n s p r o v i d e a g r e a t e r d e g r e e o f s t a s i s f o r s t o n e g r o w t h , and s h o u l d t h e g a l l b l a d d e r l o s e c o m p l e t e l y i t s a b i l i t y t o f u n c t i o n , o t h e r c o n s t i t u e n t s such as b i l e s a l t s may p a s s t h r o u g h t h e g a l l b l a d d e r w a l l , and t h e c o m p o s i t i o n o f t h e b i l e changes drastically. 4.4.
Epitaxy
One c u r i o u s f e a t u r e o f g a l l s t o n e s i s t h e r e l a t i v e l y a b r u p t change i n c o m p o s i t i o n which can o c c u r from t i m e t o t i m e d u r i n g growth ( 1 7 ) . ~ r e o v e r in a d i s t i n c t s t o n e band, two d i f f e r e n t compounds may be d e p o s i t e d . L o n s d a l e (18)
Crystal Growth in Bile
55
s u g g e s t e d t h a t e p i t a x y c o u l d a c c o u n t f o r t h e growth and s t r u c t u r e o f g a l l s t o n e s once a s u i t a b l e seed had formed. That e p i t a x y i s p o s s i b l e i s shown i n T a b l e 4 which g i v e s t h e p e r c e n t a g e m i s f i t s on so~e n a t u r a l l y o c c u r r i n g f a c e s of Table 4. Substance
Face
Cholesterol
Possible epltaxy in gallstones
Dimensions of net (~)
% misfit
(O10)
14.OO x 31.38 (90 °)
-
-
(O01)
14.OO x 33.71 (96° )
0
6.6
Calcite
(I0~0)
14.97 x 34.12 (90 ° )
7.O
8.8
Aragonite
(001)
14.88 x 31.88 (90 ° )
6.3
1.6
Vaterite
(IO~0)
14.32 x 33.96 (90° )
2.3
7.3
Apatite
(I120)
13.76 x 32.62 (90 °)
1.6
3.1
c o n s t i t u e n t s whose u n i t c e l l d i m e n s i o n s a r e known. F u r t h e r m o r e t h e r e a r e o t h e r c l o s e r e l a t i o n s between some of t h e o t h e r p o s s i b l e f a c e s . So t h a t e p i t a x y i s i n d e e d l i k e l y and i t would e x p l a i n t h e e a s e w i t h which one s u b s t a n c e a c t s as a s u b s t r a t e f o r a n o t h e r i n s t o n e s . The o r g a n i c m a t r i x may t a k e p a r t i n t h e e p i t a x y , or i t s r o l e may be s e c o n d a r y . 5.
CONCLUSIONS
G a l l s t o n e s can be o b j e c t s o f g r e a t b e a u t y w i t h t h e i r i n t r i c a t e a r r a n g e m e n t s of m a t e r i a l and c o l o u r . No one has y e t succeeded i n growing i n v i t r o , a n y t h i n g r e s e m b l i n g t h e complex a r r a n g e m e n t o f m a t e r i a l produced i n v i v o . As w e l l as many f a c t o r s d e s c r i b e d h e r e which i n f l u e n c e g a l l s t o n e f o r m a t x o n , o t h e r s may a l s o be i n v o l v e d . These c o u l d i n c l u d e p r e s s u r e , a g i t a t i o n and, i n t h e e a r l y s t a g e s of s t o n e f o r ~ t l o n , t h e flow of b i l e i n and o u t of t h e g a l l b l a d d e r l i k e n i n g the system to a continuous c r y s t a l l i s e r . The probles~ i s a f a s c i n a t i n g and c h a l l e n g i n g o n e , and a g r e a t d e a l of work i n t h e f i e l d o f c r y s t a l growth i s n e c e s s a r y b e f o r e t h e f o r m a t i o n o f such complex s t r u c t u r e s i s f u l l y u n d e r s t o o d .
REFERENCES 1.
I . A. D. B o u c h i e r and J . W. F r e s t o n ,
2.
B.A.
3.
H. T e r a ,
4.
D. J . S u t o r and S. E. Wooley, Gut 12, 55 (1971).
5.
D. J . S u t o r , The c o m p o s i t i o n of g a l l s t o n e s . I n : G a l l s t o n e s , Eds. H. M. F i s h e r , C. A. Goresky, E. A. S h e f f e r and S. M. S t r a s b e r g , Plenum P r e s s , New York and London (1979).
6.
N. A. Womack, R. Zeppa and G. L. I r v i n , Ann. Sur&. 157, 670 (1963).
7.
D. J . S u t o r and S. E. Wooley, Gut 15, 487 (1974).
8.
D.J.
Campbell and A. C. B u r t o n , Acta c h i r .
The I ~ n c e t , 340 (1968).
s u r g . G~nec. O b s t e t . 888, 731 (1949).
Scand. Supplemantum 25§, 1 (1960).
S u t o r and S. E. Wooley, Gut 1_.44, 215 (1973).
56
9.
D. June Sutor
D. M. S m a l l , G a s t r P e n t e r o l o g y 5_~2, 607 (1967).
10.
D. J . S u t o r and J . M. P e r c i v a l ,
C l i n . chim. Acta 89, 479 (1978).
ii.
D. J. Sutor and J. M. Percival, Gut 17, 506 (1974).
12.
W. H. Admirand and D. M. Small, J. clin. Invest. 47, 1043 (1968).
13.
D.J.
14.
P. Fitz-James and A. C. Burton, Canad. J. Res. E 27, 309 (1949).
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N. A. Womack, Surg. Gynec. Obstet. 133, 937 (1971).
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H.J.
Hanm~rman, B. A. Shatz and R. G. Evens, Radiology 124, 31 (1977).
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D.J.
Sutor and S. E. Wooley, Gut 15, 130 (1974).
18,
K. Lonsdale, Nature 217, 56 (1968).
Sutor and L. I. Wilkie, Gut 19, 220 (1978).
Crystal Growth in Bile
57
THE AUTHOR
D. June Sutor The author is a graduate in chemistry and crystallography from the University of New Zealand and University of Cambridge. She has spent the last 14 years studying the composition and structure of urinary stones and gallstones by X-ray diffraction, and investigating the composition of urine and bile from which growth of this crystalline material has occurred. Since becoming partially-sighted in 1979, she has become interested in theoretical aspects of stone growth.