Concretions

CONCRETIONS (from Latin concrementum - a growth), stones, concretions - dense, often stony formations that occur under pathological conditions in the animal body. In most cases, this term refers to formations that develop in the cavities of organs and in the excretory ducts of various glandular apparatuses as a result of precipitation of salts from solution. However, according to tradition, this term is sometimes also applied to calcareous deposits in tissues, for example, to a lymph gland petrified due to petrification, to a petrificate in the area of infarction, in the area of fat tissue necrosis, etc. (see Calcareous deposits, metastases). Moreover, this term does not always imply a salt formation; thus, some call protein, bacterial, fibrinous concretions the clots of fibrin in the renal pelvis, and fecal stones - clots of coagulated feces. However, it is most correct to apply the term C., as well as the terms stones, concretions, only to salt formations developing in the cavities of organs and ducts. Such C. most often form in the bile ducts and in the gallbladder, as well as in the urinary tract; also in the oral cavity at the neck of teeth (dental calculus); less frequently C. are observed in the ducts of salivary glands, in the pancreas, in the intestine, in the bronchi, in the nasal passages, in the crypts of the tonsils, in the umbilical depression, in the veins, in the cavities of the pleura, peritoneum, vaginal tunics of the testes, in the joints. In each of the listed cavities, one C. or several can form. Often, for example, in the gallbladder there are several tens or even hundreds of stones. The shape of C. can be extremely diverse. A single C., freely lying in the cavity and not completely filling it, usually has a round or oval shape. If, however, C. closely fills a given cavity, then its shape repeats the shape of this cavity and C. represents as it were a cast of it; the most typical in this sense are the branched stones of the renal pelvis. If several C. are located in a cavity, closely pressed against each other, then their contacting parts become flat, as if ground (faceted C.); the presence of such facets on C. gives them a special shape; for example, when 2-3 C. form in the gallbladder, arranged in a row, these C. acquire a barrel-shaped shape; with numerous small stones in the gallbladder, with multiple C. in the large intestine, the C. have faceted pyramidal and polygonal shapes. The faceted shape of C. in some cases (for example, in fecal stones) is explained as a result of pressure of C. on each other; in other cases, the matter is that the deposition of new salts occurs more on the parts of C. free from contact than on the contacting parts. - The sizes of human C. vary within very wide limits: from the size of a sand grain to the size of a child's head (some C. of the bladder, intestine). - The consistency of C. can also be very different; some C. (for example, pigment stones of the bile ducts, phosphates of the urinary tract) are soft, easily broken, even crushed by fingers, other C. (for example, urates and oxalates of the urinary tract) can be stony-hard, and they can only be sawn with a saw or split with a hammer. Different density can be observed in the core of C. and in its crust, as well as in different layers of it. - The surface of C. is sometimes smooth, sometimes rough; there are C. (for example, oxalates of the urinary tract) for which a spiny surface is characteristic, giving C. a resemblance to a mulberry. On a cut or break of C., a layered structure is usually found, which is an expression of the periodicity, as it were, of attacks in salt deposition; in some C. (for example, cholesterol stones of the gallbladder) on the break, a crystalline structure and radial striation are noticeable. Often the central part of the stone has a different chemical composition than its peripheral layer, which gives a different appearance to the central core and the peripheral crust of C. (combined, complex C.). Some C. have several central nuclei, around which there is periodic deposition of salts. Sometimes stones partially dissolve, and on them form

are ulcers (caries concretions). A detailed study of the structure of concretions shows that the basis of each is an organic substance impregnated with one or another amorphous or crystalline salts. The role of the aforementioned organic basis of concretions is played by various substances: desquamated epithelium of the given cavity, thickened mucus, protein precipitates, fibrin, bacterial masses, food residues, and hairballs (in the intestine); in some cases, however, the role of the material on which salts are deposited is played by a foreign body, e.g., a fragment of a catheter in the bladder, fruit stones, etc. in the intestine. The character of the salts of which a consists depends entirely on what salts are dissolved in the fluid present in the cavity or washing that cavity in which the forms. Thus, concretions in the bile ducts consist of cholesterol, bile pigments, and lime (see Gallstone disease); concretions of the urinary tract may in their composition have uric acid, uric acid salts, calcium oxalate, calcium phosphate, ammonium magnesium phosphate, more rarely-calcium carbonate, cystine, xanthine. Concretions in all other places consist of calcium carbonate and calcium phosphate. Sometimes a consists of only one substance (pure cholesterol stones of the gallbladder, stones of calcium oxalate in the bladder, etc.); in other cases, concretions consist of various substances, either closely mixed or, more often, distributed in layers. It often happens that the nucleus or several nuclei of a consist of one substance, while successive layers have a different composition; thus, for example, gallbladder concretions may have nuclei of pure cholesterol, while subsequent layers consist of cholesterol-pigment-lime masses; in the bladder, concretions are observed whose nucleus consists of calcium oxalate or uric acid salts, and the peripheral layer of phosphates. The difference in salt composition in such combined concretions is entirely connected with changing conditions of salt deposition, which in turn depends on the alternation, often extremely complex and diverse, of changes in the given secretion and walls of the given cavity (see below). In general, a detailed study of the composition of concretions in their various layers can reveal the entire 'history' of their formation, sometimes very complex. Regarding the causes and mechanism of formation of concretions, it can be noted that the formation of those concretions which represent the result of impregnation of an organic basis with lime salts in the form of either thickened mucus, as is the case in bronchial and dental stones, stones of the excretory ducts of salivary glands and the pancreas, or food residues in intestinal stones, thrombotic masses in venous stones, fibrin in concretions of serous cavities, is explained more or less simply. Here there is adsorption of lime salts by colloids of dead mass, which brings this type of concretions closer to the so-called dystrophic calcification (see Lime deposits, metastases). In particular, the same origin have concretions, occasionally found in the cavities of the pleura, peritoneum, vaginal tunic of the testicle, joints. The basis of these concretions are fibrin clots (in joints also detached and dead villi of the synovial membrane), which are impregnated with lime salts. A somewhat different course of the process must be assumed in those free concretions of the abdominal cavity, which under the microscope reveal a picture of calcified dead fat tissue; these concretions represent necrotic appendices epiploicae, in which during fat breakdown calcium soap was formed, and subsequently-calcium carbonate and calcium phosphate. Detachment of such a necrotic and petrified appendix epiploicae turns it into a freely lying in the abdominal cavity. The causes and mechanism of formation of bile and urinary concretions are much more complex and not yet fully elucidated. Schematically, the causes of formation of the above-mentioned concretions can be divided into two categories: 1. In some cases, the primary importance is the change in solubility of certain salts in bile or urine without any other changes in the secretion or in the walls of the cavities. 2. In other cases, the main importance is the appearance in the cavity contents of an organic substrate favorable for the deposition of salts in it, which is often associated with an inflammatory condition of the cavity wall. To the causes of the first category could be attributed the increase in concentration of certain substances in the secretion or excretory fluid-or from increased secretion of these substances into the fluid, e.g., cholesterol into bile in hypercholesterolemia, calcium oxalate and uric acid salts in the so-called uric acid diathesis, or from absorption of water due to stagnation of the secretion or excretory fluid. However, such supersaturation of the liquid contents of the cavity with one or another substance usually cannot yet cause precipitation of this substance from solution; for this to happen, a complex disturbance of the chemistry in the contents is required, resulting in the change or removal of those so-called protective or protective colloids that keep supersaturated salts in solution. To the causes of the second type belongs the inflammatory change of the cavity wall, accompanied by increased secretion of mucus, desquamation of epithelium, exudation; besides, the mere presence of bacteria in the cavity contents, on the one hand, produces a change in its chemistry, and on the other-gives an organic substrate that can serve as the basis of concretions. The above division of the causes of formation of concretions into two categories is the basis of the division of bile and urinary concretions by the school of Aschoff according to their mode of formation into non-inflammatory and inflammatory concretions. The first includes concretions forming aseptically, without the participation of an inflammatory process, due to a change in the concentration of certain salts in the cavity contents on the basis of metabolic disorders or due to stagnation of the contents; the second includes those that develop as a consequence of inflammatory processes in the cavities. However, such a division of concretions can be carried out only at the very beginning of their formation, since almost every concretion, however it was formed, subsequently causes inflammation of the cavity and often promotes the penetration of bacteria; in connection with this, new layers of a different chemical composition are formed on the original nucleus. Therefore, the division proposed by the school of Aschoff has not found practical application. As for the mechanism of formation of concretions, from the point of view of colloid chemistry, it is considered either as the penetration of crystalloid bodies into coagulating colloids (Lichtwitz) or as the combined precipitation of colloidal and crystalloid substances (Schade). Of practical interest is the question of the possibility of regression, i.e., dissolution of concretions. The research of Hansemann and Aoyama showed that human gallstones can dissolve only in the bile of rabbits and dogs; on the other hand, under natural conditions in the human gallbladder, one can sometimes find concretions with signs of partial dissolution, and sometimes concretions disintegrating into parts. Although these data are not fully conclusive in the sense of the possibility of complete dissolution of concretions under natural conditions in humans, they still make this possibility more or less probable at least for some gallstones. The significance of concretions-see Stone disease, Gallstone disease, Fibrinous stones, Litholysis, Pleural cavity, Testicles (their tunics), Joints, etc.