CHAPTER VII.

URINARY CONCRETIONS.

Urinary concretions or calculi consist of an aggregation of solid matter that has become separated or precipitated from the urine. They may form in any part of the urinary tract, from the tubules of the kidney to the meatus urinarius. They vary very much in their composition, but invariably consist of certain constituents of the urine-either normal or pathologic that have separated or become precipitated from it. The nucleus may, however, consist of a foreign body that has been introduced into the urinary passages, or of certain substances that have their nativity in the body, such as mucous or blood coagula, or fragments of morbid tissue that have become detached. Of the foreign substances that have been found to form the nucleus of urinary calculi may be mentioned peas or beans that have been introduced into the urethra by the insane or by children, pieces of catheters or bougies that have been accidentally broken off in the urethra or bladder, pieces of soap or candles, hairpins, pins, needles, and bullets that have lodged in some portion of the urinary tract. From this it is seen that the nucleus of a urinary calculus may be any substance that has its origin in the body and that exists in solid form in the urinary passages, or a foreign body that may have been accidentally or intentionally introduced into them.

The conditions of the urine favoring the growth of calculi are variable. Among the causes may be mentioned (1) a diminution in the amount of water excreted; (2) a change in the reaction of the urine, whether abnormally acid or alkaline; (3) an increased formation of some of the less easily soluble constituents of the urine. Changes in the

reaction embrace hyperacidity, which favors the deposition of uric acid and urates and of calcium oxalate by diminishing the solvent action of the urine over these substances; and an alkaline condition of the urine, which causes the separation of the phosphates and carbonates of calcium and magnesium and of ammonium urate. The chief effect of an increased acidity of the urine is to lessen the solubility of the uric acid by diminishing the amount of alkali with which it may enter into combination. Uric acid is usually present in the urine in solution in the form of normal urate of sodium or potassium, which is very soluble in water. In case the uric acid is deprived of a part or the whole of its base, either the acid urate of potassium or sodium or uric acid is the result. These substances, being much less soluble in water than the normal urates, separate from the urine, and tend to become aggregated in the form of concretions. An alkaline reaction of the urine may be due to the presence of either a fixed alkali or to free ammonia and ammonium carbonate. It rarely happens that a calculus forms as a result of a deposition of the earthy phosphates by a fixed alkali, as is well demonstrated in those cases in which alkaline remedies are given for a long time, as in the treatment of acute rheumatism, and also in those cases in which the urine is habitually alkaline, as in some cases of faulty metabolism.

Of much greater importance is an ammoniacal reaction that frequently results in a calculus formation by the deposition of triple phosphate, amorphous phosphates, and ammonium urate. (See Reaction, p. 31.) Concretions from this cause are quite commonly met with in cases of irritation or inflammation of the bladder, the change from a normally acid to an alkaline reaction being due to the presence of the urea ferment that decomposes the urea. A deposit of phosphates always tends to increase the size of any calculi that may already exist.

A diminution in the amount of water excreted, particularly when coupled with an increased formation of any of the slightly soluble constituents of the urine, such as uric acid and acid urates, calcium oxalate, cystin, and very rarely xanthin, favors the tendency to the formation of concretions within the urinary passages, since these substances do not find a sufficient amount of urine to hold them in solution.

CONSTITUENTS OF URINARY CALCULI.

These are either organic or inorganic or a mixture of the two. They are conveniently divided into two classes, as follows: (1) Primary constituents, or those which separate from the urine without any material change in the character of the urine, other than changes referable to altered metabolism; and (2) secondary constituents, or those which separate from the urine as a result of ammoniacal fermentation.

Urate of ammonium, calcic carbonate, and calcic phosphate may, therefore, be either primary or secondary constituents.

Urinary concretions are most commonly found in the pelvis of the kidney and in the bladder, but they may form in any part of the urinary tract. In the Warren Museum at the Harvard Medical School is a rare specimen showing a number of medium-sized concretions in the pelves of both kidneys and in both ureters, also a large calculus in the bladder. Calculi are also sometimes formed in sinuses connecting the urinary passages with the intestines, uterus, or vagina.

The number of concretions that may be present in the urinary passages is almost unlimited; often there is only a single stone, but there may be several hundreds.

Urinary concretions vary in size from that of a pinhead to that of an orange or even larger. Those of small size

have been somewhat arbitrarily termed sand or gravel, while those of large size are called stones or calculi. The size of a calculus is limited only by the dimension of the cavity in which it is formed. The smaller concretions usually emanate from the kidney or pelvis of the kidney, while those of large size generally come from the bladder. Concretions vary in weight from a few milligrams to several grams; in the Dupuytren Museum, at Paris, is a calculus weighing 1596 grams.

The surface of a urinary calculus varies with its composition and its location in the urinary tract. Those consisting of uric acid, phosphates, and cystin are usually smooth, while those made up of calcium oxalate are generally rough and lobulated-mulberry calculi In case several concretions occupy a single cavity-for example, the bladder their surfaces are often polished in those portions that rub against each other during the natural movements of the bladder wall or during the changes in position of the body. The smooth or polished surfaces are termed facets.

The shape of urinary calculi varies as the location. Those in the kidney proper are generally very irregular; they often have small projections that have extended into cavities formed by the destruction of the renal tissue. Calculi in the pelvis of the kidney when large usually assume the form of that cavity, projections taking place into the calices, and giving the calculus in some cases a shape not unlike that of an elephant; small concretions in the pelvis are generally round or oval. Calculi in the bladder vary greatly in shape. If only a single concretion be present, it is usually round, oval, or sometimes flat. If numerous calculi are present, their form may be modified by constant pressure against each other. Occasionally, a calculus becomes partially encysted in the bladder, so that the deposit takes place only upon one portion, thereby causing the growth of the calculus to take place in one direction only, and giving it a very irregular shape. Those that have formed in the urethra are generally oblong or cylindric in shape, and when there are several, the ends of those that are adjacent are often highly polished.

The color of calculi varies with their composition and the admixture of organic subtsances such as blood, pus, fibrin, etc. Those consisting of uric acid and urates are always colored, varying between a pale straw and a dark brown,

the coloring-matter being derived chiefly from the urine. Calculi consisting of calcium oxalate are often of a darkbrown color due chiefly to the presence of decomposed blood and of fibrin. Phosphatic calculi are generally grayish or white, while those made up of cystin are usually yellow in color.

The composition of urinary calculi may be simple, consisting of only one constituent of the urine, such as uric acid or calcium oxalate, or it may be compound, with two or more primary deposits occurring in separate and alternate layers, the most common of these constituents being uric acid and calcium oxalate. Several of the constituents may be mixed in any portion of the stone. It is not uncommon to find a calculus with a central portion composed of alternate layers of two or more of the primary constituents and an outer layer of some one of the secondary constituents.

Most urinary calculi consist of three distinct parts—i. c., the nucleus; the body; and the crust. The nucleus occupies the center and may have the same composition as the rest of the concretion, but it often consists of some albuminous body, such as a coagulum of fibrin, or mucus or pus mixed with uric acid, urate, or calcium oxalate crystals about which are deposited other similar or perhaps entirely different urinary constituents. A concretion may have several nuclei, as, for example, when two or more small calculi become united to form a single stone; these nuclei are readily seen when a section is made through the calculus. The nucleus varies much in size and usually occupies the center of the concretion, but it may be excentrically placed especially if the growth of the calculus is only in one direction.

The body comprises the greater part of the calculus and surrounds the nucleus; it may or may not have the same composition as the nucleus. The body may consist of concentric layers of two or more urinary constituents, such as a layer of uric acid and urates, another of calcium oxalate, and so on for several layers. The several layers of the body may be differently colored; even those having the same composition may be variously colored.

The crust or external envelop of the calculus is deposited upon the body, and always consists of one or more of the secondary constituents of the urine, the phosphates usually predominating; in other words, the crust is always found