A Prospective Study of Common Bile Duct Calculi in Patients Undergoing Laparoscopic Cholecystectomy

Abstract

Objective:

To define the incidence of problematic common bile duct calculi in patients undergoing laparoscopic cholecystectomy.

Summary Background Data:

In patients selected for laparoscopic cholecystectomy, the true incidence of potentially problematic common bile duct calculi and their natural history has not been determined. We evaluated the incidence and early natural history of common bile duct calculi in all patients undergoing laparoscopic cholecystectomy with intraoperative and delayed postoperative cholangiography.

Methods:

Operative cholangiography was attempted in all patients. In those patients in whom a filling defect was noted in the bile duct, the fine bore cholangiogram catheter was left securely clipped in the cystic duct for repeated cholangiography at 48 hours and at approximately 6 weeks postoperatively.

Results:

Operative cholangiography was attempted in 997 consecutive patients and was accomplished in 962 patients (96%). Forty-six patients (4.6%) had at least one filling defect. Twelve of these had a normal cholangiogram at 48 hours (26% possible false-positive operative cholangiogram) and a further 12 at 6 weeks (26% spontaneous passage of calculi). Spontaneous passage was not determined by either the number or size of calculi or by the diameter of the bile duct. Only 22 patients (2.2% of total population) had persistent common bile duct calculi at 6 weeks after laparoscopic cholecystectomy and retrieved by endoscopic retrograde cholangiopancreatography.

Conclusions:

Choledocholithiasis occurs in 3.4% of patients undergoing laparoscopic cholecystectomy but more than one third of these pass the calculi spontaneously within 6 weeks of operation and may be spared endoscopic retrograde cholangiopancreatography. Treatment decisions based on assessment by operative cholangiography alone would result in unnecessary interventions in 50% of patients who had either false positive studies or subsequently passed the calculi. These data support a short-term expectant approach in the management of clinically silent choledocholithiasis in patients selected for LC.

Choledocholithiasis were found in 3.4% of patients selected for laparoscopic cholecystectomy. On repeated tube cholangiography, more than one third of these had spontaneous clearance of their common bile ducts at 6 weeks postoperatively, leaving only 2.2% of patients requiring endoscopic retrograde cholangiopancreatography stone retrieval.

Although laparoscopic cholecystectomy has been widely adopted as the procedure of choice for gallbladder removal, there is uncertainty about the management of common bile duct calculi in this setting. This is particularly so for those patients where choledocholithiasis is not predicted by preoperative imaging, usually ultrasonography of the biliary tree. In such circumstances many surgeons do not perform routine operative cholangiography, and clinical experience suggests that the frequency of subsequent symptoms or complications from biliary calculi is low and in the order of 2–3%. This is 30–50% less than that predicted by operative cholangiography, suggesting overdiagnosis, spontaneous passage, or silent persistence of many common duct calculi. A significant proportion of patients may therefore undergo unnecessary biliary instrumentation with its inherent morbidity and mortality.^1–5 Where a confident diagnosis of choledocholithiasis was made, 20–50% patients who underwent preoperative endoscopic retrograde cholangiopancreatography (ERCP) had no demonstrable calculi.^6–11 Similarly, almost 20–40% of patients who have bile duct filling defects at per-operative cholangiography have either a negative surgical bile duct exploration or a negative postoperative ERCP.^12–14

Patient selection for biliary intervention has been flawed partly because of the lack of a sensitive noninvasive imaging modality and also because the incidence and natural history of asymptomatic common bile duct calculi has not been determined in patients selected for laparoscopic cholecystectomy. In this study of patients undergoing laparoscopic cholecystectomy, we prospectively define the true incidence of common bile duct calculi and their early natural history by undertaking intraoperative cholangiography and delayed postoperative cholangiography in those who had demonstrable intraoperative filling defects in their bile ducts.

MATERIALS AND METHODS

Over an 11-year period (July 1990 to July 2001), 999 patients (810 females + 189 males), aged 49 ± 15 years underwent laparoscopic cholecystectomy by a single surgeon (G.O.S.) for symptomatic cholelithiasis. One hundred and nine (10.9%) operations were undertaken at the time of the acute presentation. In all cases, the diagnosis of gallbladder calculi was confirmed by conventional ultrasonography, and the common bile duct was considered normal. None of the patients were jaundiced, and there was no sonographic evidence of intra or extrahepatic biliary dilatation or choledocholithiasis. Previous history of jaundice or acute pancreatitis was recorded, as were serum bilirubin, alkaline phosphatase, gamma glutamyl transferase, and aspartate aminotransferase at the time of admission for surgery. During the same period, 24 more patients were referred for laparoscopic cholecystectomy after ERCP clearance of symptomatic common bile duct calculi because of obstructive jaundice, unresolved pain, or recurrent or unresolving pancreatitis. These are not discussed further.

Operative cholangiography was attempted in all patients using a 4-Fr or 5-Fr ureteric catheter with a nylon stylet (Porges SA, Cedex, France). This catheter is marked at 1-cm intervals and has 2 distal apertures located 1 and 2 cm proximal to the tip. This was introduced through the abdominal wall via a needle through a separate skin puncture wound and advanced through the cystic duct, if possible to the 5 cm mark, where it was secured with 2 titanium clips (Ligaclip®Extra, Ethicon). The plastic stylet was then withdrawn and backflow of bile through the tube was awaited. Two syringes (one containing saline and the other contrast–30% Hypaque solution) were then connected to the tube by a 3-way stopcock attached to a butterfly needle. Bile was aspirated through the connecting system to eliminate gas bubbles. The catheter was then flushed through with saline solution while inspecting at the site of insertion into the cystic duct for leakage. Leakage occurred rarely, mostly when the catheter was not sufficiently advanced through the cystic duct. In these circumstances, repeat cannulation was attempted with a new catheter, and if unsuccessful, the cholangiogram was abandoned.

After satisfactory connection, 3 mL of contrast was injected and the biliary tree was imaged using an image intensifier. Further contrast was injected and the operating table position was altered if required to image the proximal ducts. Two “permanent” films were obtained and were interpreted independently by the surgeon at the time of surgery. In those cases where any filling defect of the common bile duct (CBD) was identified, the cholangiogram catheter was left in situ and the cholecystectomy was completed laparoscopically. The common bile duct was not directly manipulated, dissected or palpated during the course of the operation. All retained catheters were required to be advanced more than 5 cm into the cystic duct and to be secured by 2 titanium clips. When necessary a new catheter was reinserted, and secured. The catheter was allowed to drain freely overnight and was then occluded. At 48 to 72 hours, a cholangiogram was performed via the catheter to confirm its position and to examine for filling defects. It was then reoccluded and covered with a standard wound dressing. At 6 weeks, an additional cholangiogram was undertaken and patients with persistent filling defects underwent ERCP. (Fig. 1) All postoperative tube cholangiography studies were performed in the x-ray department by a consultant radiologist using digital fluoroscopy. The catheter was removed after a negative study at 6 weeks or after a repeat study after ERCP. The choice of the 6-week interval was based on a number of considerations. In the era of open cholecystectomy and open exploration, retained common bile duct calculi occasionally passed within 6 weeks of surgery and therefore a delayed policy of intervention was favored. This would also allow sufficient time for the formation of a mature tract around a relatively nonreactive cannula and hence allow its safe removal. It was also reasoned that the delay of ERCP for up to 6 weeks would have the advantage of reducing morbidity caused by negative intervention without undue inconvenience to the patients. We have previously reported in a preliminary study that the presence of the cholangiogram catheter in the cystic duct for over 6 weeks was safe and without complications.¹⁵

FIGURE 1. Operative cholangiography (A) showing multiple filling defects at time of surgery. Repeat cholangiography at 48 hours (B) shows confirmed calculi in the common bile duct, and cholangiography at 6 weeks (C) illustrates the common bile duct clear of calculi.

Cholangiograms that were positive intraoperatively and negative at 48 to 72 hours were classified as false-positive operative cholangiograms. Cholangiograms that showed filling defects intraoperatively and similar appearances at 48 to 72 hours were considered true positive. Spontaneous passage of calculi was defined where the true positive cholangiograms were negative on the 6-week study.

Bile duct and liver function data were compiled on a database (Microsoft Access XP) for analysis (Microsoft Excel XP and SPSS for Windows V10.0). Differences between means were tested with the Student t test and proportions were compared with the χ² statistic. A P value of less than 0.05 was deemed significant. Multivariate regression analysis was performed to examine for correlation between liver function tests and asymptomatic choledocholithiasis. Each patient gave written informed consent and the study was performed in accordance with the ethical guidelines of the Mercy Hospital and Teaching Hospitals University College Cork.

RESULTS

Cholecystectomy was commenced laparoscopically in all 999 patients, but in 21 cases (2.1%), conversion to open surgery was necessary because of unclear anatomy (15 cases), cholecystenteric fistulae (2 cases), necrotic gallbladder (2 cases), bleeding (1 case), or subvesical hepatic abscess (1case).

Although intraoperative cholangiography was attempted in all cases except for 2 patients with a documented contrast allergy, it was successful in 962 patients (96%). Of the patients in whom cholangiography was successful, 46 patients had filling defects in the common bile or common hepatic duct, and 6 others had a dilated common bile duct (>10 mm). In these cases the cholangiogram catheter was left in situ. In 4 other cases, the catheter was left because of either nonemptying of CBD despite hyoscine butylbromide (1 patient) or concerns about abnormal anatomy (3 patients). These studies were normal at 48 hours.

Of the 46 patients with filling defects on per-operative cholangiography, 12 had a normal cholangiogram at 48 hours (26%); each of these also had a normal study at 6 weeks. A further 12 had a normal cholangiogram at 6 weeks (26%; Fig. 1). One of these patients achieved a complete and asymptomatic clearance of bile duct calculi involving the complete duct system, including the biliary radicals (Fig. 2). None of the patients developed complications during passage of stones; 2 reported a single episode of pain each. The remaining 22 patients underwent ERCP after 6 weeks postoperatively within a week of the tube cholangiogram. Of these, 2 were unable to have ERCP stone extraction because of the presence of duodenal diverticula at the ampulla. These were not demonstrated on either of the cholangiogram studies. These patients were then recommended expectant management, the cholangiogram catheter was removed, and at a follow-up of 5 years they have not had sequelae or further investigations. All of the others had common bile duct stones, which were removed endoscopically. None of the patients with a dilated common bile duct in the absence of a filling defect had a positive cholangiogram at 48 hours.

FIGURE 2. Operative cholangiography showing calculi filling the common bile duct and common hepatic duct (A). These calculi are still present at 48 hours (B) but have passed at 6 weeks (C).

Acute Presentation

Of the 999 patients documented above, 109 were operated on after acute presentation. Of these, 11 had filling defects on cholangiography intraoperatively, 5 at 48 hours, and 1 remained at 6 weeks. Nine percent (n = 10) of the acute cases required open surgery because of difficulties with gallbladder removal as compared with 1.5% of the elective cases (P < 0.0001).

Preoperative Biochemistry and Common Bile Duct Calculi

Serum aspartate transaminase, gamma-glutamyl transpeptidase, alkaline phosphatase, and bilirubin were recorded preoperatively on all patients. Using multivariate regression analysis, there was a significant correlation between the presence of calculi and a raised serum alkaline phosphatase (P < 0.005) and patient age (P < 0.009; Table 1). However, neither the alkaline phosphatase levels nor age were predictive of spontaneous passage of the calculi. Of the 962 patients who had successful operative cholangiography 85 had serum alkaline phosphatase levels greater than 300 international units (IU; normal range 30–300 IU). Common bile duct calculi were significantly more prevalent in the presence of elevated serum alkaline phosphatase (11/85 vs. 22/877; P < 0.001) The spontaneous passage rate was similar for patients with elevated or normal alkaline phosphatase values (5/11 vs. 7/22; NS). Common bile duct stones were present in 7/84 patients age greater than 70 years as compared with 27/878 patients age less than 70 years (P < 0.001). Spontaneous passage of calculi was similar for both age groups (4/7 vs. 8/27; NS).

TABLE 1. The Predictive Ability of Liver Function Indices on the Presence of Common Bile Duct Calculi

Bile Duct Diameter, Calculi Number, and Size

The common bile duct diameter was measured from external wall to external wall using the external diameter of the size 4-Fr ureteric cannula as reference. Of the 34 patients with confirmed calculi at 48 hours, 10 had CBD diameter greater than 10 mm. There was no difference in the spontaneous passage rate between those patients with common bile duct diameters greater or less than 10mm (3/10 vs. 9/24; NS)

The calculus size was similarly determined using the size 4-Fr ureteric cannula. The largest calculus for each patient was recorded and the sizes varied between 2 and 15 mm. The number of calculi within the CBD ranged between 1 and more than 50 for the patients who cleared their ducts (Figs. 1 and 2) and was between 1 and 8 for those who had retained calculi at 6 weeks. There was no relationship between calculus size and bile duct clearance; stones less than 5 mm were often retained whereas stones of 15 mm passed spontaneously.

Morbidity

There were no intraoperative complications attributable to the cholangiography. No patient reported any catheter-related problems either before or after its removal. In particular, there was no case of cholangitis while the catheter was in situ and no bile leaks occurred on its removal.

DISCUSSION

This study shows that in patients undergoing laparoscopic cholecystectomy the incidence of common bile duct calculi with the potential for long-term morbidity is less than 2.5%. This is less than half of those patients diagnosed by operative cholangiography and suggests that decisions based on intraoperatively acquired data alone would result in many patients being subjected to unnecessary instrumentation of the common bile duct. These findings have implications for surgical practice. In the era of open cholecystectomy, choledocholithiasis was diagnosed at per-operative cholangiography and calculi were removed by CBD exploration, a natural extension of the operative procedure. However, laparoscopic cholecystectomy is now the optimal approach with postoperative morbidity and mortality rates and duration of hospital stay lower than for standard incision cholecystectomy^16–20 and similar to small-incision cholecystectomy.²¹ This has altered the approach to choledocholithiasis, as laparoscopic exploration of the bile duct, particularly for asymptomatic stones, is technically demanding and individual surgeons’ experience is limited. A surgical practitioner performing 100 laparoscopic cholecystectomies or less per annum would be unlikely to develop or maintain the skills necessary for laparoscopic common bile duct exploration. In this series of 999 cases over 10 years, only 46 could have been considered for exploration and in 24 of these, intervention would have been unnecessary.

The practice of routine operative cholangiography has been questioned and even abandoned by many surgeons. Advantages cited by proponents of intraoperative imaging are the diagnosis of unsuspected calculi, the delineation of biliary anatomy to immediately detect or reduce injury risk, and the value of a negative assessment and permanent intraoperative record when confronted with a symptomatic patient on postoperative follow up. Many of these concepts were formulated in the era of open cholecystectomy but may not have the same validity in modern surgical practice, where noninvasive techniques are the norm and where improved imaging by endoscopic ultrasound and magnetic resonance cholangiography has facilitated a policy of more selective and therapeutic ERCP.

Operative cholangiography was attempted in all patients in this series with a success rate of 96% and an apparent false-positive rate for calculi of 25%, figures similar to previous reports of open cholecystectomy.^22–25 We prospectively classified the disappearance of filling defects on cholangiograms at 48 hours as a false-positive intraoperative study. This may be unduly rigorous as when the intraoperative films were subsequently re-evaluated by an independent biliary radiologist at 48 hours, it was felt that in at least 6 of these 12 patients the intraoperative images were more in keeping with biliary calculi than gas artifact. Characteristics suggesting calculi in 6 patients were irregularity of outline and/or variable size of multiple filling defects with a constant location on both intraoperative films. Although this issue is untestable, it is possible that spontaneous passage of calculi may happen within 48 hours of cholecystectomy and that operative cholangiography is more accurate than determined by our strict classification. Although it is also possible that intraoperative ultrasound evaluation might help exclude the false-positive cases, it would not predict those stones that pass spontaneously. We also submit that by prior exclusion of obvious common bile duct calculi, there would be a trend towards increased false positive rates in the small/normal caliber bile ducts.

The frequency of persistent choledocholithiasis, those most likely to cause long-term problems, was 2.5% in this study. This is half that predicted by operative imaging (in this study) and suggests that in greater than 95% of patients, operative cholangiography did not influence patient management. Assuming a low morbidity for patients whose calculi were managed expectantly, intraoperative diagnosis may be less important and operative cholangiography may be employed selectively, and reserved for situations where there are concerns about biliary anatomy.²⁶

Initially, to reduce the need for bile duct exploration, preoperative ERCP was performed by many surgeons on all patients suspected of having choledocholithiasis, but this approach led to a significant proportion of nontherapeutic ERCPs and unnecessary patient morbidity.^1–5 In this study, biliary calculi were associated independently with increasing age and an elevated serum alkaline phosphatase but neither of these accurately select for treatment. The ability to select patients for ERCP preoperatively has been greatly facilitated by the introduction of magnetic resonance cholangiography, which reliably detects stones greater than 3 mm diameter and it is likely that this and endoscopic ultrasound evaluation will reduce the incidence of nontherapeutic ERCP.^27–29

Although there is little information available on the long-term expectant management of asymptomatic bile duct stones, it is the default option of surgeons who do not perform routine operative imaging. This study supports a policy of delayed management at least for 6 weeks after cholecystectomy as clearance of calculi occurred without significant complication in 12/34 patients. Selection of patients at 6 weeks could be performed by magnetic resonance cholangiography. It is possible that more calculi would have passed after 6 weeks, thus favoring further expectant management. A recent report comparing immediate and expectant management of 8 and 14 patients respectively with small common bile duct calculi (less than 5 mm) diagnosed intraoperatively found expectant management to be safe and cost effective.³⁰ In a comparison of expectant versus immediate treatment the risks from complications of choledocholithiasis are balanced against the risks of ERCP or bile duct exploration in the 50% of patients who do not need treatment. Resolving this by clinical trial would require a pool of 8000 patients who had laparoscopic cholecystectomy with operative cholangiography to ensure randomization of 200 patients with persistent calculi (assuming the rate of 2.5% persistent calculi in this study).

Intubation of the cystic duct for 6 weeks with fine-bore cannulae facilitated repeated radiographic assessment or biliary decompression where necessary in the event of biliary obstruction. Even when the bile ducts were clear the cannulae were left in situ for 6 weeks to allow development of a peritubular inflammatory tract and avoid intraperitoneal leakage of bile on withdrawal of the tube. Apart from occasional mild discomfort of the skin there were no complications. Bile duct obstruction or the need for biliary decompression did not occur during the study. Even though, the luminal diameter of these tubes was 1.0–1.5 mm the volume of bile drained during the initial 12 hours was similar to previous experience with standard T-tubes, usually greater than 100 mL. Thus, this technique may occasionally be safely used for decompression or clarification of biliary anatomy following laparoscopic cholecystectomy.

CONCLUSIONS

The incidence of choledocholithiasis in patients undergoing laparoscopic cholecystectomy is approximately 3.5%. Up to one third of these patients do not require intervention because they clear their ducts of calculi spontaneously after surgery. It is reasonable to manage asymptomatic choledocholithiasis expectantly in the short term after laparoscopic cholecystectomy.