Calculi or Stones

CALCULI or STONES may occur in any hollow organ in which there is stagnation of the fluid contents together with an excess of some particular substance in solution : they may also occur in the ducts leading from glands from the same cause (see Plate). The chief places where stones occur are in the urinary system and in the gall-bladder.

Urinary Calculi.

Calculi may be found in almost any part, of the urinary system from the collecting tubules in the kidney where they are microscopic in size, to the bladder where they are known as sand, gravel or stones, according to size. In the kidney calculi are usually composed of a mixture of uric acid and water, and occasionally of calcium oxalate. There is evidence that minute concretions of these substances may form in the collecting tubules of the kidney, and pass down to the renal pelvis where they become the nucleus for the further deposit of material to form larger stones. Numerous small stones may be found in the renal pelvis, or a single large branching calculus may be formed, filling up the entire pelvis of the kidney. A small calculus may pass down the ureter into the bladder and there increase to a considerable size ; in passing down the ureter, it gives rise to renal colic (see CoLic). If the calculus becomes impacted, usually at the upper end of the ureter, the condition known as hydrone phrosis occurs and this is likely to be followed by an infective inflammation going on to suppuration and ulceration.

Calculi in the bladder may have their origin in the kidney, as already stated, or in the bladder itself ; in the latter case they may occasionally form around foreign bodies introduced into the bladder, but in the majority of cases this is not so and the exact method of formation de novo is not yet fully understood, but may be due to the deposition of crystals on organic debris, or on a small focus of organisms. The exact nature of the crystalline material forming the stone depends almost entirely upon the chemical constituents of the urine in which they are formed. In many cases a stone is formed over a period of years, and as the urine may alter its character frequently in this time, a stone is often composed of layers very different in colour, chemical corn position and hardness. Calculi may grow to a great size without causing any symptoms, if smooth, but as they are usually angular or rough on the surface, bleeding generally occurs.

Sometimes a calculus composed almost entirely of one sub stance is found, the substances which give rise to such a stone being uric acid, calcium oxalate, xanthin, cystin or calcium phos phate. More commonly one of these substances forms the nucleus of a larger stone, the outer layers of which may be formed of several different substances such as carbonates and phosphates. The nature of calculi varies according to their composition ; uric acid calculi are hard, smooth and oval or rounded when found in the bladder, or moulded to the cavity when found in the renal pelvis. Pure calcium oxalate stones are rare, but mixed stones in which this substance forms a considerable part are common. Such stones are often formed around a nucleus of uric acid or urates and are distinguished by their dark brown colour and very rough, jagged exterior. Further deposition of other substances may convert the jagged stone into a smooth one. Phosphatic calculi are formed when the bladder is inflamed and are usually rough and often crumble easily. Cystine calculi are very rare ; when they occur they are rather soft and may reach the size of a hen's egg. Xanthin calculi also are extremely rare, only a few isolated specimens having been described in medical literature.

The effect of a large calculus is obstruction : so long as the stone remains loose the obstruction will be intermittent and may largely depend upon the posture of the patient. If the stone be comes impacted or large, obstruction will become complete.

Biliary Calculi or Gall-stones

are formed from the con stituents of the bile together with a certain amount of organic material, and their formation largely depends upon stagnation of bile in the gall-bladder. Their composition and shape vary in the same manner as urinary calculi, the chief constituents being cholesterol, bile pigments and lime salts. There is usually a nucleus which is commonly almost pure cholesterol. Occasionally a stone is composed of almost pure cholesterol and is quite clear and pale yellow in colour : these stones are usually oval and solitary, lying loose in the neck of the gall-bladder. More often they are covered by a coloured secondary deposit. The com monest type by far is the mixed calcium-bilirubin-cholesterol stone; these may occur as single large stones or multiple smaller ones numbering many hundreds in a single case. The large single ones are oval, and the smaller multiple ones facetted. The colour varies from pure white through yellow and green to black. All gall-stones contain a considerable quantity of organic matter and may contain living bacteria.

Gall-stones, either single or multiple, may cause no symptoms and are often not discovered during life ; on the other hand they may give rise to serious effects, partly mechanical and partly in flammatory in character. The inflammatory effects cause in flammation of the gall-bladder or cholecystitis. A large stone may become impacted in the neck or the duct of the gall-bladder and cause great distension, a smaller gall-stone may pass out of the gall-bladder and become impacted lower down the common bile duct giving rise to biliary colic and jaundice. In more chronic cases with a subsequent acute inflammation, a gall-stone may ulcerate through either into the peritoneal cavity or into some portion of the gut. In the former case, peritonitis will set in, and in the latter the stone may be small enough to pass right through the bowel or may become impacted and give rise to acute intestinal obstruction. This may also be the result when the stone passes down the duct from the gall-bladder into the gut. Subsequent to passage of a gall-stone through the common bile duct or coincident with the presence of a gall-stone in the gall bladder, localized carcinoma may develop.

Pancreatic Calculi

are rare. They form in the pancreatic duct and are composed mainly of calcium carbonate and phosphate: they are usually small in size and may be numerous. In shape they are rounded or oval, and in colour whitish. If they be come impacted in the duct obstruction will follow and bacteria may gain a foothold and set up an acute inflammation. When some pancreatic juice can escape the duct becomes distended.

Salivary Calculi

may occur in the ducts of the salivary glands, probably from the depositions of salts on inspissated mucus. They are uncommon, but when they occur they are rough, ir regular and white : they consist chiefly of calcium phosphate and carbonate. They may occlude the duct partially or completely, causing inflammation and dilatation of the duct and atrophy of the gland. Dentists refer to tartar on teeth as salivary calculus.

Intestinal Calculi

always have a nucleus of some indigest ible material; in countries where oatmeal is largely eaten they are not infrequent. They may cause little or no symptoms, but if large may cause intestinal obstruction. In animals such as the horse and cow they are of relatively common occurrence and may attain to many pounds in weight ; they occur chiefly in the stomach and have a nucleus of hair. Another type of concretion found in the intestine is called Intestinal Sand and is probably formed in the upper part of the large intestine.

Preputial Calculi

are sometimes formed by the deposition of urinary salts upon the accumulated smegma under a prepuce that cannot be retracted.

Prostatic Calculi

occur chiefly in the lateral lobes by the deposition of salts on the normal corpora amylacea. They may reach a considerable size and obstruct the outflow of urine.

Nasal Calculi or Rhinoliths

occur around nasal secretions or blood clots, but most frequently around foreign bodies intro duced into the nasal cavities; they contain a considerable amount of organic matter.

Mammary Calculi

are sometimes formed in the lactiferous ducts of the breast causing a similar condition in the gland to salivary calculi.

Lung Calculi

are occasionally found in the bronchi. They may be formed in the same manner as calculi in other sites, or as the result of a piece of calcified lung tissue becoming separated through suppuration. If the obstruction be complete collapse of that portion of the lung behind the obstruction follows, if incom plete the result is bronchiectasis.

Uterine Calculi or Womb Stones

sometimes occur, usually as the result of calcareous degeneration of a tumour ; occasionally a foetus may die in utero and later become encapsuled and calci fied, forming a large calcified mass in the cavity of the uterus known as a lithopaedion.

A considerable amount of work of different kinds has been done on calculi, especially the commoner ones. Their chemical com position is known moderately accurately; gall-stones, as has been stated, may be formed round a nucleus of organisms, and if these belong to the typhoid group, the stones may be a source of danger by starting an epidemic of typhoid fever at a later date. Certain gall-stones from cases of cancer of the gall-bladder have been found to contain minute traces of radioactive substances. In some cases both gall-stones and urinary calculi will act upon a photographic plate in the dark ; this action is believed to be due to the action of hydrogen peroxide produced from turpines, or to minute traces of ammonia. The effect can be produced either at room temperature or at 37°C ; at the latter temperature a few hours may suffice. (P. L.-B.)