Stenosis, and finally occlusion, of the common duct may arise from the cicatrization of an ulcer. Such ulcers may occur in several modes. They may result from catarrhal inflammation of a chronic type, much new connective-tissue material forming, and in the process of cicatrization, with the contraction belonging to it, the lumen of the canal is so far filled up that the passage of bile is effectually prevented. They may be produced in that state of the tissues which accompanies certain cachectic and profoundly adynamic conditions, as in severe typhoid fever. Such ulcers may also be due to the mechanical injury effected by the migration of a gall-stone. In cicatrizing, a tight stricture, impermeable to the passage of bile, may result, or the lumen of the canal be entirely obliterated. In the latter case the duct itself may disappear and leave no trace. An ulcer situated at the duodenal end of the common duct and extending into the duodenum may also in the process of healing so contract as to render the orifice impermeable to bile. The same effect may follow the cicatrization of an ulcer of the duodenum in the immediate vicinity of the orifice of the common duct.
Without the intervention of an ulcer as a means of explaining closure of the common duct, this accident may be caused by a catarrhal inflammation which effects denudation of the basement membrane, and thence union may be produced by the mere contact of the freshly-granulating surfaces. Congenital occlusion of the bile-ducts or obstruction occurring in a few days after birth, it is probable, is effected in this way, but no direct evidence of the process has thus far been offered. During intra-uterine life, as at any period in after-life, it seems necessary to the production of such changes that a peculiar constitutional state must exist; otherwise, such a result might happen to every case of catarrhal inflammation of the bile-ducts. The extent of the changes is further evidence in the same direction; for not only are the walls of the duct in permanent apposition and adhesion, but the duct degenerates into a mere fibrous cord, and in some instances is nearly, even entirely, obliterated.189
189 Ziemssen's Cyclopædia, p. 589.
The cystic or common duct—the latter to be chiefly considered—may be occluded by the retention in its lumen of some foreign body. The impaction of a biliary calculus has already been repeatedly referred to, but there are some additional points demanding consideration. The larger concretions may be stopped in the neck of the gall-bladder; those small enough to enter the canal may be arrested at its bend behind the neck, and the very entrance of the cystic duct may be blocked, as in a case examined by the writer.
The hepatic duct is very rarely permanently occluded. As the calibre of this canal continuously enlarges downward, there is no point at which a stone is likely to be arrested; nevertheless, it occasionally happens that such an obstruction does occur. An example has occurred under the observation of the writer, but the cause was a gunshot wound of the liver.
The most usual, and for very obvious reasons the most important, of the sites where occlusion occurs is the common duct and at the termination of the duct in the small intestine, the intestinal orifice. Just behind and to the right of its orifice the duct is dilated into a fossa—the diverticulum Vateri; and here concretions of a size to pass along the common duct are stopped. It is not essential that the stone fit the canal: it may do so and prevent any bile passing into the duodenum; it may be a polyangular body, and, though wedged in, leave spaces through which more or less can slowly trickle. The symptoms will be modified accordingly. Again, the diverticulum may contain numerous concretions, which distend the canal greatly, but through the interstices of which some bile can flow.
Other foreign bodies very rarely close the intestinal end of the ductus communis; thus, for example, a cherry-seed, a plum-seed, a mass of raisin-seeds, may slip into the orifice after the passage of a gall-stone has stretched it sufficiently. A much more common cause of occlusion is an intestinal parasite, which crawls in and is fastened. The common round-worm is the most frequent offender, and much less often liver-flukes find a lodgment there.
The ductus communis choledochus may be closed by agencies acting from without. They are various, but the most common are the carcinomata. Primary cancer of the gall-bladder and gall-ducts, although not of frequent occurrence, is by no means rare. It develops in connection with the connective-tissue new formations produced by the inflammation following the migration of large calculi. A very instructive example has been examined by the writer. The patient, a woman aged forty-eight, had had numerous paroxysms of hepatic colic, and after death, which followed a protracted stage of jaundice by obstruction, a large ovoid calculus, filling the gall-bladder, was found, and an extensive organized exudation of inflammatory origin was the seat of carcinomatous disease involving the cystic and common ducts and closing the lumen of both. Cancer of the pylorus, of the duodenum, of the pancreas, of the right kidney, and of the liver itself, not unfrequently by exterior pressure permanently occlude the common duct. To this category of obstructing causes must be added enlarged lymphatic glands of the transverse fissure, large fecal accumulations, tumors of the ovaries and uterus, aneurisms of the abdominal aorta, and especially aneurism of the hepatic artery, several examples of which have been reported, and one has occurred in a case seen by the writer.
The effects of obstruction are much less important when the cystic duct is closed. The contents of the gall-bladder accumulate, constituting the condition known as dropsy of the gall-bladder. A catarrhal state of the mucous membrane is set up; the muco-pus formed mixes with the bile, and the mixture undergoes fermentative changes which further alter its character and impart to it irritating qualities, in consequence of which the mucous membrane becomes more decidedly inflamed, and a still more purulent fluid forms, so that ultimately the contents of the gall-bladder are entirely purulent, and that organ may attain to enormous size. Instead of a catarrhal inflammation leading to suppuration, the mucous membrane may pour out serum abundantly, the biliary contents and mucus disappear by absorption, and finally the gall-bladder will be moderately distended by a serous-like fluid. No further disturbance ensues, and the gall-bladder, thus shut off from participation in the hepatic functions, ceases to give trouble.
The results are far different when the obstruction occurs in the hepatic or common duct, for then the bile can no longer perform its double function of secretion and excretion—of contributing materials necessary to digestion and assimilation, and excreting substances whose removal is necessary to health. The liver continuing to functionate after closure of the duct is effected, obviously the secretion of bile continues to accumulate, and the irritation of the mucous membrane causes a catarrhal state; mucus is poured out, and serum escapes from the distended vessels. If the hepatic duct only is obstructed, the dilatation will not involve the cystic duct and gall-bladder, but as the common duct at its termination is occluded, usually the whole system of tubes will be affected by the ensuing changes. The alterations already described as occurring in the gall-bladder take place in all the hepatic ducts. The bile-elements are absorbed, and the fluid distending the whole system of hepatic tubes becomes finally a semi-transparent serum or a very thin sero-mucus, having in bulk a pale sea-green color. Although an intense jaundice coexists with the obstruction, no portion of the bile escapes into the ducts. At the beginning of the obstruction more or less bile is in the tubes, and then the fluid will have a distinct biliary character; but as it accumulates, first the bile-constituents disappear, then the mucus—which at the outset was formed freely—is absorbed, and at last only a colorless serum remains. This fluid, which has been examined chemically by Frerichs, is found to be slightly alkaline, to have only 2 per cent. of solids, and to present no trace of any biliary constituent. As the fluid accumulates the gall-bladder and ducts dilate, sometimes to an enormous extent, the fluid they contain amounting to several pints. The walls of the ducts grow thinner, and may finally give way with the pressure or from external violence, the fluid exciting an intense and quickly-fatal peritonitis. Important changes occur in the structure of the liver also. With the first retention of bile the liver conspicuously enlarges, and may indeed attain to twice its normal size, but it subsequently contracts, and may lessen in as great a degree as it had enlarged. Changes begin in the glandular structure as pressure is brought to bear on the cells by the enlarging ducts. The liver-cells become anæmic and the protoplasm cloudy, but granular and fatty degeneration does not take place. Even more important as an agency affecting the condition of the hepatic cells is the hyperplasia of the connective tissue, which ensues very promptly when an obstruction to the flow of bile arises from any cause, as has been shown by Legg190 and Charcot.191 The liver on section has a rather dark olive-green color, and is firmer in texture, owing to the increased development of the connective tissue; the cells are bile-stained and contain granules of coloring matter and crystals of bilirubin, and although they are at first not altered in outline, subsequently more or less atrophy is produced by the contraction of the newly-formed connective tissue and the pressure made by the dilated hepatic ducts.