Obstruction occurs from various causes, of which one of the commonest is Gall-stones as described above. Inflammation of the ducts sometimes produces obstruction, the inflammation being nearly always due to an extension of catarrh from the stomach and duodenum. As the duct near the orifice is narrow a trivial inflammatory swelling may produce an obstruction, which the bile, possessing a low pressure, is unable to overcome. Tumours and inflammations around the duct may cause obstruction. This is not infrequently the case with Cancers of the head of the pancreas or those involving the lymphatic glands in the portal region of the liver. We have already seen that an obstruction of the hepatic ducts in the substance of the liver occurs in cancer of the liver, in cirrhosis, etc.
Congenital atresia of the main bile-ducts is by no means an uncommon lesion. The ducts in part or as a whole are reduced to the condition of solid threads, or they are altogether indistinguishable. This is due to a defect occurring mostly in early fetal life, and in some instances several members of the same family have been affected. The occlusion leads to intense icterus, and in this case as in icterus of newly-born children generally the bilirubin assumes the crystalline form. An intense monolobular cirrhosis resulted in a case observed by the author. Inflammation and thrombosis of the umbilical vein producing swelling around the duct at the porta of the liver was a cause of obstruction in a newly born child observed by the author. A septic thrombophlebitis resulted after the separation of the cord. In this case also the bilirubin had a crystalline form.
The Results of obstruction vary according to the site of the obstruction. The usual result is Icterus or Jaundice, but this does not occur if the obstruction be limited, as is not uncommon in the case of gallstones, to the cystic duct.
If the Cystic duct alone be obstructed then the consequence is that no bile can get into the gall-bladder. In that case the bladder may shrink, and any mucus in it dry-in and perhaps afterwards become chalky. In many cases, however, there is an abundant secretion of mucus, and the bladder gets filled with it. The mucus often after a time gives way to a more fluid secretion, and the bladder may be converted into a thin-walled cyst (Hydrops vesicae felleae) which may be as large as the fist, with clear fluid contents.
When the gall-bladder is thus cut off and no longer available as a store for the bile, there sometimes occurs a Dilatation of the larger bile ducts chiefly in the portal region of the liver, so that the bile may lie here instead of in the gall-bladder, and pass into the duodenum during digestion. This constitutes an imperfect compensation for the loss of the gall-bladder. Gall-stones may form in the dilated ducts.
In the case of Obstruction of the ductus choledochus, there is stagnation both in the gall-bladder and in the whole system of bile ducts. The stagnation tells first on the gall-bladder, which dilates readily and stores up the bile. There may even be rupture of the gall-bladder from excessive dilatation. If the obstruction be prolonged great dilatation occurs throughout the whole system, and serious changes frequently result in the liver itself.
Next to the gall-bladder the ductus choledochus and the larger bile ducts, which are not supported by the firm liver tissue, are most liable to dilate. This dilatation may be very extreme, these ducts becoming sometimes as great in circumference as the thumb, and it may even go on to rupture.
There is sometimes even an Acute inflammation of the bile ducts apparently from decomposition of the bile, and this may lead to Biliary abscesses. This occurs when the obstruction is incomplete, as when it is produced by the pressure of the tumour, and there is therefore the possibility of the propagation of septic decomposition from the duodenum to the stagnant bile. There may be numerous abscesses filled with, a tenacious bile-stained pus.