since homan first described silk suture material acting as a nidus for the development of subsequent cbd stones after cholecystectomy in 1897 , several authors have reported that suture materials may cause choledocholithiasis1 ) . silk , chromic catgut , parasites , and other foreign bodies are known to form occasionally such niduses in the cbd2 - 7 ) . in addition , with the advent of laparoscopic cholecystectomy , several authors have reported cases of choledocholithiasis induced by migrated surgical clips8 - 11 ) . after cholecystectomy for gallstone associated cholecystitis , we infrequently encounter bile duct stones that cause symptoms , such as epigastric pain , cholangitis or right upper quadrant pain . during the past two decades , many studies have been conducted on the pathogenesis of bile duct stones , but nevertheless , their exact pathogenesis remains unknown . however , it has been proposed that gradual erosion with subsequent inflammation induced by suture material , at a cystic duct ligature , might be a leading cause of stone formation within the cbd . in the described case , the core of a biliary calculus in the cbd was found to contain filament - like threads . as a result , we suggest that the careful selection of suture materials , such as synthetic and absorbable threads , could prevent subsequent migration and stone formation in the cbd after hepatobiliary surgery . a 74-year - old man was admitted to our hospital with a two - month history of intermittent episodes of right upper quadrant abdominal pain without jaundice . open cholecystectomy had been performed for symptomatic gallstone - associated cholecystitis approximately 15 years earlier . at that time the distal cbd had been dissected and subsequently repaired with a proline suture after t - tube insertion . over the intervening years the patient had remained asymptomatic until 2 months prior to this presentation . on admission , a physical examination revealed the patient to be relatively weak with an area of pain and mild tenderness to palpation in the right upper quadrant , and a post - operative scar on the abdomen . his vital signs were within normal ranges , i.e. , body temperature 37.5 , blood pressure 120/80 mmhg , heart rate 82/min , respiratory rate 20/min , and biochemical laboratory studies were normal , i.e. , aspartate transaminase 23 iu / l ) , total bilirubin 0.56 mg / dl ( normal 0.1 - 1.2 iu / l ) , alkaline phosphatase 139 iu / l ( normal 80 - 270 initial plain abdominal radiographs demonstrated two surgical clips in the right upper quadrant of the abdomen ( figure 1 ) , and the following abdomen - pelvic computerized tomography ( ct ) scan revealed a small stone in the cbd and some sandy stones in the dependent portion of the cbd without significant biliary dilatation ( figure 2 ) . endoscopic retrograde cholangiopancreatography ( ercp ) was performed 2 days after admission , and clearly demonstrated a large freely movable filling defect suggestive of a cbd stone at a mildly dilated distal cbd , and a mild stricture at the mid - common bile duct . during ercp , after endoscopic sphincterotomy , a large stone was successfully removed using a retrieval balloon catheter and a dormia basket . on gross examination , this irregularly shaped cbd stone , measured 1.00.91.0 cm , had filament - like threads projecting from it ( figure 3 ) . retained stones are the cause of choledocholithiasis after cholecystectomy , and these either arise due to primary formation ( arising de novo ) or as a consequence of biliary surgery . bile duct stones are usually classified into two categories based on sites of formation , i.e. , as primary or secondary stones . while primary or stasis stones are formed de novo and originate in the bile duct , secondary stones are formed primarily in the gallbladder and subsequently migrate to the bile duct , where they are retained12 ) . brown pigment stones are generally regarded as primary stones with bacterial overgrowth that are formed secondary to biliary stasis . several species of bacteria produce -glucuronidase , which deconjugates bilirubin diglucuronide and frees bilirubin complexes , allowing them to complex with calcium and form an insoluble precipitate of calcium bilirubinate12 , 13 ) . various factors predispose stone formation in the biliary tract , such as malignancy , benign stricture , bacterial infection , ascaris ( round worm ) infestation ( especially in east asia ) , and a broad spectrum of foreign bodies6 , 13 ) , the latter of which include metallic hemoclips , retained tubes , ingested foods , and suture materials2 - 5 , 8 , 9 , 14 - 19 ) . it is presumed that these factors play an important role in bile stasis by blocking normal bile flow in the biliary tract . moreover , bile flow blockage could be an initiating factor of nucleus formation in biliary calculi in the cbd . walker et al.19 ) first reported surgical clip migration into the bile duct in 1979 . moreover , since the introduction of laparoscopic cholecystectomy in 1987 , it has become a preferred procedure for the surgical removal of gallbladder stones , and is rapidly replacing open cholecystectomy . however , the mechanism of surgical clip migration into the bile duct is poorly understood . it has been reported that up to one - third of recurrent post - cholecystectomy stones may be due to migrated surgical clips7 ) , and the increasing use of surgical clips and frequency of laparoscopic cholecystectomies has resulted in many reported cases of surgical clip - related stone formation . nevertheless , some cases might have gone unnoticed due to the spontaneous passage of stones caused either by surgical clips or suture materials . non - absorbable sutures , particularly silk , have been found to be responsible for the majority of reported cases of stone formation resulting from a suture material nidus following biliary surgery . the first case of a silk suture serving as a nidus for stone formation after cholecystectomy was reported in 18971 ) . ban et al.5 ) reported that irritating operative residuals , such as non - absorbable suture materials , account for 82% of stones that form around a foreign body . surgical sutures , especially those composed of non - absorbable materials , appear to function as a nidus for crystallization ; bile salts gradually deposit around such nuclei , finally develop into large stones . the role of silk sutures in this context in the biliary tract has been debated by authors . mackie et al.17 ) reported three cases of suture material - related stone formation in the cbd , and suggested the use of an absorbable suture material , such as chromic catgut , for ligating the cystic duct or artery . in our case , the suture material was identified as proline , which was used to repair cbd dissection caused by cbd exploration . these proline sutures , which are non - absorbable synthetic monofilament sutures , are still commonly used in neurosurgery because they induce little tissue reaction and are easily placed . during our review of previous cases , a report was found of a patient in whom chromic catgut had formed a cbd stone nidus , which suggests that absorbable sutures can also cause calculus formation3 ) . the origins of specific causative postoperative sutures have been postulated to be either from cystic duct ligatures or subsequent choledochotomy stitches , which then migrate into the cbd and form biliary calculi . moreover , since laparoscopic cholecystectomy has largely replaced open biliary surgery , the frequency of suture material - induced calculus formation decreased substantially . it has been postulated that the chain of events that causes the migration of suture material into the bile duct , may be the same as that of surgical clip migration11 ) . presumably , repetitive erosion and ulceration of the bile duct by suture material due to an ongoing localized inflammatory process play a primary role in stone formation . when a fragment of suture material is introduced into the cbd , it serves as a nucleus for stone crystallization . over time the nucleus increases in size and moves slowly toward the bile duct as a consequence of biliary duct activity , and eventually forms a sizable calculus . in addition , if any other cause of bile stasis is present as mentioned above , stone formation may be accelerated . endoscopic stone removal with a retrieval balloon catheter and a dormia basket after sphincterotomy has been recommended as the procedure of choice for the majority of patients who have undergone previous cholecystectomy , since it requires a shorter hospital stay than surgical manipulation20 ) . bile duct stones can also be extracted endoscopically in patients with biliary pancreatitis or acute obstructive cholangitis . for those patients who have undergone either open cholecystectomy or laparoscopic cholecystectomy , clip migration or suture knot migration should be considered as a cause of recurrent painful symptoms in the right upper quadrant . the described case gives us the opportunity to remind surgeons and endoscopists that biliary stones can be formed by the surgery - related materials in patients that have undergone previous biliary surgery . thus , here , we report a case in which a surgical suture migrated into the cbd and formed the core of a stone in a patient who had previously undergone open cholecystectomy , and provide a review of the literature . in conclusion , any exogenous biliary tract foreign bodies , including non - absorbable suture materials , can infrequently function as niduses for stone formation in the common bile duct . we emphasize that synthetic , absorbable sutures or other suture materials with low inflammatory reaction potentials , should be used for biliary surgery , and that they be carefully applied to reduce the risk of recurrent stone formation in the biliary tract .
the use of non - absorbable suture materials for cystic duct ligation after cholecystectomy can expose patients to the risk of recurrent stone formation in the common bile duct ( cbd ) . 
 however , in korea suture materials have rarely been found to act as a nidus for common bile duct calculus formation . 
 recently , we experienced a case in which suture material , that had migrated from a previous cholecystectomy site into the cbd , probably served as a nidus for common bile duct stone formation . 
 the stone was confirmed by endoscopic retrograde cholangiopancreatography ( ercp ) and removed successfully using a basket . 
 the authors report a case of surgical suture migration and discuss its subsequent role as a stone forming nucleus within the cbd in a patient who underwent open cholecystectomy ; and include a review of the literature .