We found that the most cost-effective treatment for patients with symptomatic cholelithiasis when the probability of CBD stones is 4%-100% is LC with IOC and postoperative ERCP if stones are detected on IOC. If the probability of CBD stones is 0%, LC alone is the most cost-effective approach. However, at the extremes of CBD stone probabilities, the differences in cost and LOS between the LC with IOC and postoperative ERCP strategy and some of the other strategies were small, and therefore may not be financially meaningful, rendering these strategies essentially equivalent. In addition to the probability of CBD stones, our model was sensitive to one health input: specificity of IOC, and three costs: cost of hospitalization for LC with CBDE (without complications), cost of hospitalization for LC without CBDE (without complications), and cost of LC with IOC.
The NIH state-of-the-science statement on ERCP for diagnosis and therapy supports the use of IOC for patients with suspected CBD stones 4
. In patients with CBD stones, this statement indicates that laparoscopic CBDE and postoperative ERCP are comparable in safety and clearing stones from the CBD duct 4
. However, the consensus panel proposes that postoperative ERCP appears to be associated with greater health care cost and longer LOS, and suggests that laparoscopic CBDE is more efficient and preferable when surgical proficiency is available 4
. In our analysis, a key determinant of treatment strategy cost was the cost of hospitalization. From the third party payer perspective taken by our analysis, the cost of hospitalization for patients undergoing CBDE in addition to cholecystectomy is much higher than for those undergoing cholecystectomy without CBDE. The cost difference between these two DRGs was large enough to render the laparoscopic CBDE approach not cost-effective. In addition, laparoscopic CBDE is unavailable at many institutions because it requires advanced surgical expertise, whereas expertise in ERCP is more readily available in most US hospitals 44
Our results suggest that IOC should be used across a wide range of CBD stone probabilities. This finding has two implications. First, many studies have tried to devise clinical scoring systems to determine the probability of CBD stones in patients with cholelithiasis 45-50
. However, our results suggest that it is cost-effective to use IOC across almost the entire probability range (4%-100%) of CBD stones. At a 2% probability of CBD stones, the LC alone strategy would cost $746 per hospital day averted compared to LC with IOC ± ERCP. Similarly, at a 3% probability, it would cost $1,421. Perhaps the additional cost may not be worth the decrease in LOS, and LC with IOC ± ERCP may be preferred if the probability of CBD stones is 2%-3%. According to our analysis, it is important to identify those patients with a 0%-1% probability of CBD stones so that these patients can avoid IOC and can undergo LC alone followed by expectant management. Jaundice, abnormal liver chemistries, and ductal dilatation seen on ultrasound are indicators of common bile duct stones. If none of these are present, then it is highly unlikely that CBD stones are present4
. One study of biochemical predictors of the absence of CBD stones reported that patients with a normal serum gamma glutamyl transferase (GGT) had a 2.1% risk of CBD stones (negative predictive value of 97.9%)49
. Therefore, perhaps patients with a normal GGT may be best treated with LC followed by expectant management. Additional studies of predictors of the absence of CBD stones are needed to help to determine which patients should undergo LC followed by expectant management and which should undergo LC with IOC ± ERCP.
The second implication of our findings is that surgeons striving for the most cost effective care should routinely perform IOC. However, in a recent survey of members of the American College of Surgeons, only 381 surgeons out of 1,411 (27%) considered themselves routine (versus selective) IOC users 51
. Some surgeons do not use IOC because they believe it adds too much time to the operation or is too costly, and that this is not worth the potential benefit. Two prospective studies reported that it takes about 15 minutes to perform an IOC 52, 53
, and surgeons who used IOC routinely reported faster IOC completion times than selective IOC users 51
. From a cost perspective, two studies found that routine use of IOC during LC was cost-effective for preventing CBD injury 54, 55
. In our study, the use of IOC in addition to LC added little extra cost. However, the use of CBDE in addition to LC added significantly more cost because the use of CBDE changes the DRG for the hospitalization.
One major advantage of using IOC routinely is that the sensitivity (97%) and negative predictive value (99%) are high 27
. Therefore, if CBD stones are present they should be detected on IOC and a normal IOC almost always means that the CBD is clear. A negative IOC can prevent patients from undergoing unnecessary attempts at CBD clearance 56
and patients can be reassured that the risk of complications from retained CBD stones is extremely low.
The natural history of CBD stones is not well-defined 3, 57
. The results of one study suggest that not all patients with CBD stones found at the time of IOC will need to be removed via postoperative ERCP because some CBD stones will pass spontaneously 58
. However, there is no way to predict which CBD stones will pass and which will lead to costly complications such as pancreatitis or cholangitis.
We did not include patient preferences (health state utilities) in our model for three reasons. First, we assumed that asymptomatic choledocholithiasis would not cause long-term changes in quality of life. Second, we assumed the disability incurred by each treatment strategy, including missed diagnoses of choledocholithiasis, would be included in the denominator of the cost-effectiveness analysis where the cost per hospital day averted was examined. Third, there are no published data for patient preferences for choledocholithiasis, symptomatic or asymptomatic, and we did not want to include invalidated data in the model. Health state utilities would likely impact this analysis and further research on this topic is needed.
Our analysis provides a unique evaluation of the therapeutic options for patients with possible CBD stones because it differs from prior studies in three important ways. First, prior studies modeled scenarios that are not as widely applicable as ours. One study compared ERCP with laparoscopic CBDE for incidentally discovered CBD stones on IOC at the time of LC 8
. Since most surgeons do not use IOC routinely, that study represents a small proportion of all patients undergoing LC 51
. Another study compared several strategies, but each was modeled for two different scenarios, one in which CBD stones were present, and one in which they were absent 9
. Our study examines the decision-making process more broadly than these studies because we started with the more common clinical scenario of a patient with symptomatic cholelithiasis who may or may not have CBD stones. Second, one previous study assumed that there were no procedural deaths and the only complications considered were pancreatitis after ERCP and bile leak after laparoscopic CBDE 8
. We included the risk of death and any complication that increased cost or LOS for each diagnostic and therapeutic procedure in our model. This is important because clinicians decide which procedures to use by considering the associated risks and benefits. Finally, most of these studies used institution costs or costs from the provider perspective 8, 59, 60
. Only one study 9
, in addition to ours, used a third-party payer perspective. Using national Medicare data for the costs makes our results more generalizable across the United States.
The only analysis besides ours to vary the probability of CBD stones found that LC followed by expectant management was the most cost-effective strategy at a CBD stone risk between 0 and 11%; above 55%, ERCP was the most cost-effective 59
. If the risk was between 12% and 54%, endoscopic ultrasound (EUS) was the most cost-effective. If EUS was not available, IOC became the most cost-effective if the risk was between 17% and 34% 59
. Both EUS and magnetic resonance cholangiopancreatography (MRCP) are accurate for detecting CBD stones61, 62
. However, we excluded these modalities from our model because we only included modalities that could be used to both diagnose and treat CBD stones. In addition, that study stated that ERCP was superior to IOC and therefore used a higher sensitivity and specificity for ERCP than IOC. Whereas, in our study, we used test characteristics from current literature and the sensitivity and specificity of IOC are higher than that of ERCP. Finally, in that study the cost perspective is that of the provider and in our study the cost perspective is that of a third party. The most cost-effective diagnostic and therapeutic strategies from the provider perspective may not be the same as those from a third party perspective.
In conclusion, the most cost-effective treatment strategy for the majority of patients with symptomatic cholelithiasis (4%-100% probability of CBD stones) is LC with routine IOC. If stones are detected, CBDE should be forgone and the patient referred for ERCP. For those patients with a 0% probability of CBD stones, LC alone followed by expectant management is the most cost-effective strategy.