Chapter 3: Introduction

 

           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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