Gallstones
are the most common biliary pathology. It is estimated that gallstones are
present in 10–15% of the adult population in the USA. They are asymptomatic in
the majority (> 80%) (Conlon 2008).
Approximately
10% of patients with gallbladder stones have coexisting CBD stones. For patients
younger than 60 years, however, the frequency ranges from 4% to 7%. This
increases to 18% for those aged 70- 79 years and over 30% for those over 80
years. Indeed, increasing life expectancy in many countries seems likely to be
associated with an increase in the number of patients with symptomatic
gallstones, particularly stones in the bile duct (Roberts 2004).
Regarding the risk factors of
gallstones formation, the two most important determinants of gallstones
frequency in any population are age and gender. Gallstones become more common
with increasing age, and at least twice as common in women (Scragg
1984).
Other factors realted to the
development of gallstones include obesity, ileal disease or resection, liver
cirrhosis, cystic fibrosis, diabetes mellitus, long term parentral nutrition,
impaired gall bladder emptying, periods of dieting on a very low fat diet,(Festi
1998) as
with any rapid weight loss program (medical or surgical), the development of
gallstones is markedly increased during the period of rapid weight loss to an
incidence of about 30% to 40% in patients previously without gallstones (Tipton et al., 2004), and positive family history of previous
cholecystectomy (Nakeeb 2002). Pigment
gallstones occur commonly in patients with various hemolytic anemias, and
especially in hereditary spherocytosis and certain forms of thalassemia and
sickle cell hemoglobinopathies (Tipton et
al., 2004).
The
usual sequence of events is the development of stones in the gallbladder, after
which they may migrate into the bile duct. These bile duct stones are usually
called secondary stones (Ko
et al., 2002).
On
the other hand, Primary stones form within the bile ducts in about 15% of
patients with CBD stones in the setting of gallbladder agenesis, and patients
with bile duct stones with or without gallbladder stones (Nakeeb 2006).
One
of the rare causes of primary CBD stones is the presence of foreign body in the
CBD. This foreign body may be a parasite like Fasciloa or Ascaris, which is
more common in Asian population (Manson-Bahr
et al., 1940).
On the other hand, the commonest type of nonparasitic foreign body in the
common bile duct is a residual object from previous surgery, such as a metal
clip after laparoscopic cholecystectomy or suture material, which can act as a
nidus for stone formation. The recent increase in descriptions of bile duct
stone formation due to a residual metal clip after laparoscopic cholecystectomy
is especially noteworthy (Tamura et al., 2002). Another rare possibility is an ingested foreign body
included in food. (Kaji
et al., 2004).
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