Endoscopic Balloon Dilation for Removal of Bile Duct Stones: Special Indications Only

In this issue of Endoscopy, Arnold and colleagues report on a randomized pilot study comparing endoscopic balloon dilation (EBD) and endoscopic sphincterotomy (EST) for removal of bile duct stones [1]. The authors claim that their results indicate that EST is superior in terms of stone removal, complication rate and duration of the procedure and conclude that EST should remain the standard technique for endoscopic stone removal.

A total of 60 patients with bile duct stones were randomly assigned to either EST or EBD. EBD was performed with an 8-mm dilation balloon which was inflated twice for 60 seconds to its maximum diameter and pressure; EST was performed according to standard guidelines. Patient groups were comparable for the most important predictors of successful stone removal, i. e. stone size and stone number. In both groups, successful stone removal in one endoscopic session was achieved in all patients, but in the EBD group seven patients (23 %) required an additional EST as an “escape” procedure. The authors consider EBD to have failed in these patients, and therefore conclude that the success rate of EBD is 77 %; significantly worse than the 100 % success rate in the EST group. Of the seven EBD patients who required an “escape EST”, six, however, had all their stones removed in the same endoscopic session. According to the intention-to-treat principle, these patients cannot be considered as patients with failed stone removal. Arnold et al. used liberal stone selection criteria (< 20 mm, stone number < 5), did not allow for mechanical lithotripsy and considered the use of an ”escape” EST a failure, irrespective of whether subsequent stone removal was successful or not. Since EBD does not enlarge the biliary orifice to the extent of EST, these premises inevitably lead to a lower success rate for EBD, which makes the observation in the present study more logical than relevant. Stone size and stone number are independent predictors for successful stone removal after EBD and EST as well as predictors for secondary outcomes such as the use of lithotripsy or an ”escape” EST after EBD [2]. Two large randomized studies have shown that relatively easy stones (stone size < 10 mm and stone number < 3) can be removed after EBD in over 90 % of cases without the need for lithotripsy or an additional EST [2] [3] . As far as success rate is concerned, EBD may thus be an alternative for this category of patients. For complicated stones (stone size >10 mm or stone number > 3) the success rates of both EBD and EST are inevitably lower but not significantly different (in our series 84 % and 83 %, respectively) [2]. It is in this latter category of stones, however, where EBD requires lithotripsy at a higher rate than EST (50 % vs. 23 %) and where the “escape” ESTs are required (23 % in our series) [2]. In only a few of these patients EBD will be considered to be a valid alternative to EST.

An important reason why EBD has not evolved as a widespread routine procedure is the fear of complications, especially pancreatitis. This is mainly based on the findings of the EDES study, a randomized multicenter study from the United States comparing Endoscopic Balloon Dilation with Endoscopic Sphincterotomy for removal of bile duct stones [3]. In this study, 16 out of 118 EBD patients developed pancreatitis, including four cases of severe pancreatitis and a fatal outcome in two. In the EST group, five out of 114 patients developed pancreatitis (none severe) (P < 0.001). The EDES study was published in abstract form in 1998 and has still not been published in a peer-reviewed journal. Other randomized trials and uncontrolled series, including over 850 patients, have not shown a higher rate of pancreatitis after EBD but some groups have reported an increased rate of asymptomatic hyperamylasemia [4]. In the study by Arnold and colleagues, complications occurred in five of the 30 EST patients vs. nine out of 30 EBD patients [1]. Pancreatitis occurred in three EST patients (all cases graded as mild) and in six EBD patients (mild n = 4, severe n = 2). In both groups there were three patients with asymptomatic hyperamylasemia.

Theoretically there are several reasons why EBD could be associated with an increased risk for pancreatitis. First, during balloon dilation of the biliary sphincter the trauma is applied circumferentially and therefore partially in the direction of the pancreatic duct. This in contrast to EST where, ideally, the incision of the biliary sphincter is directed away from the pancreas. Second, during balloon dilation of the biliary sphincter the sphincter ampulla is also dilated. This sphincter, which is shared by the common bile duct and main pancreatic duct at their most distal part, has a variable length and may measure several millimeters in patients with a long common channel. Studies in pigs have shown that immediately after EBD there is transmural inflammation and intramucosal bleeding of the biliary sphincter [5] and this most likely also occurs with the sphincter ampulla. In theory, this may result in a relative outflow obstruction of the pancreatic duct causing an increase in the rate of hyperamylasemia and/or pancreatitis. This may be especially relevant in patients in whom prior cannulation of the bile duct was difficult, with multiple cannulations of the pancreas. Another reason why hyperamylasemia and/or pancreatitis may occur more frequently after EBD is that stone removal takes more time and involves more manipulation of the papillary complex. Yasuda et al. have reported an increased rate of hyperamylasemia after EBD in patients who underwent mechanical lithotripsy compared with patients in whom stones were fragmented with extracorporeal shockwave lithotripsy (ESWL) [6], a fact that may be explained by less manipulation of the papillary complex in the latter group. Arnold and colleagues did not use lithotripsy techniques, although they included patients with stones up to 20 mm in size [1]. Other series have shown that stones larger than 10 mm virtually always require mechanical lithotripsy for removal after EBD [2]. In order to remove these large stones after EBD, forceful stone extraction may have been necessary. In our randomized study, the only death occurred in an EBD patient who developed a retroperitoneal perforation after forceful extraction of a 15-mm bile duct stone [2]. The “severe papillary swelling as a consequence of EBD and initial stone removal” as reported by the authors may therefore have been responsible for some of the observed cases of pancreatitis and might have been prevented by either crushing the stones prior to extracting them from the ducts or by restricting inclusion to patients with smaller stones.

Ideally, randomized studies should compare techniques which have evolved beyond their learning phase. To some extent the present study may suffer from the contradictio in terminis of its title. Nevertheless, we agree with the authors’ most important conclusion: that EST should remain the standard procedure for removal of bile duct stones. This is not because the results of EBD are so disappointing but because many of the arguments that led to the revival of EBD have been taken away. Prospective studies have shown that EST for bile duct stones is much safer than previously suggested [7]. The risk of post-sphincterotomy bleeding, the one complication that can be prevented by performing EBD, is approximately 1 % in routine circumstances, leaving little room for EBD to do better. On the other hand, the most important complication of endoscopic stone removal is pancreatitis, the one complication for which EBD may carry an increased risk. The possibility of long-term complications after EST has been another reason to explore EBD as a sphincter-preserving alternative. Although EST results in a permanent loss of sphincter function, chronic duodenobiliary reflux with bacterial colonization and low-grade inflammation of the biliary system [8], long-term follow-up studies have not revealed any severe late complications [9], thus challenging the relevance of sphincter preservation after EBD.

So when should EBD be considered for removal of bile duct stones? The primum non nocere concept still leads us to perform EBD in the small subgroup of young patients (< 40 years?) with small stones. These stones can easily be removed without lithotripsy or ”escape” EST and the sphincter function is retained in these patients with a long life expectancy. Unfortunately, young age by itself is a risk factor for pancreatitis [7]. Together with the conflicting results concerning the rate of post-EBD pancreatitis and the observed higher rate of asymptomatic hyperamylasemia after EBD [4], this makes us reluctant to perform EBD in patients with risk factors for pancreatitis. In the case of difficult cannulation of the bile duct with multiple passes into the pancreatic duct and/or pancreatic opacification, we therefore still perform an EST. It is important to note that there are no data available to substantiate this policy.

EBD may also be considered in circumstances where EST is more difficult or dangerous. Others have demonstrated its low bleeding risk in patients with risk factors for bleeding and this issue has been discussed elsewhere recently [10].

EBD may be especially suited for removal of bile duct stones in patients with a prior Billroth-II gastrectomy because EST is more difficult in these patients. In a randomized trial comparing EBD and EST in Billroth-II gastrectomy patients, we achieved complete stone removal in 14 of 16 EBD patients (88 %) vs. 15 of 18 EST patients (83 %) [11]. Mechanical lithotripsy was required in three and four patients in these groups, respectively, and only one EBD patient required an ”escape” EST for stone removal. The median time required for stone removal was 30 minutes in both groups. Complications occurred in seven EST patients (39 %; including three bleedings) and in three EBD patients (19 %; including one pancreatitis). EBD in Billroth-II gastrectomy patients seems successful and safe and may be superior to EST. This may also hold for the occasionally encountered patient with periampullary diverticula where the position of the papilla prohibits a safe sphincterotomy. Although no series are available exploring its use in this situation, EBD may be a safe and easy alternative to EST.

The vast majority of patients with bile duct stones, however, do not fall in one of the small subgroups outlined above. EST, therefore, remains the cornerstone of the endoscopic management of bile duct stones. EBD is a technique which should be reserved for special indications only.

References

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• 11 Bergman J J, van Berkel A M, Bruno M J, et al. A randomized trial of endoscopic balloon dilation and endoscopic sphincterotomy for removal of bile duct stones in patients with a prior Billroth-II gastrectomy.  Gastrointest Endosc. 2001;  53 19-26