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Keywords
Pancreas divisum, ERCP, EUS, MRCP
Introduction
Pancreas divisum is the most common congenital anomaly of the ductal system of the pancreas. It is the result of non-fusion of the dorsal and the ventral pancreatic ducts embryologically during the second month of gestation. Autopsy series report a prevalence of 4-14%.1-4 ERCP studies have indicated presence of pancreas divisum in up to 7.5%.5 These numbers do not necessarily reflect accurate prevalence data since ERCP is done in a selected group of patients referred for evaluation of pancreatitis, and the ventral pancreas is not consistently cannulated or injected. The dorsal pancreatic duct, which drains the majority of the pancreatic gland, fuses with the ventral duct draining the head of the pancreas to open at the major duodenal papilla. However in the case of pancreas divisum the majority of the gland is drained by the dorsal pancreatic duct through the minor pancreatic papilla. (Figure 1). This anomaly can result in impediment to the flow of pancreatic secretions and lead to pancreatitis in a subset of patients. This may potentially lead to acute recurrent or chronic pancreatitis in the dorsal duct. The etiologic role of pancreas divisum in acute and chronic pancreatitis is somewhat controversial. In general, medical pancreatologists are skeptical of the connection, while interventional pancreatic endoscopists believe in a cause-and-effect relationship with pancreatitis and offer therapy.
Evaluation/Diagnosis of pancreas divisum
ERCP is considered the reference standard for evaluation of pancreas divisum. This is partly due to the historical absence of any other diagnostic modality for visualization of the pancreatic ductal system. When ERCP is performed, one will usually see a short ventral duct when cannulation of the pancreatic duct is performed selectively at the ampulla. The ventral duct is typically 1-4 cm in length and the duct does not cross the midline.6 Arborization, or branching of the duct into tiny secondary and tertiary branch ducts, is suggestive of a ventral pancreas and pancreas divisum. In a third of the cases of pancreas divisum, the ventral duct can be completely absent.7 Practically, it can be impossible to distinguish failure to cannulate the pancreatic duct via the major papilla from pancreas divisum. Furthermore, it is important clinically is to distinguish between pancreas divisum and incomplete filling of the pancreatic duct secondary to a benign stricture or tumor. It is thus sometimes important to visualize a dominant dorsal pancreatic duct in order to confirm pancreas divisum.8 The obvious limitation to ERCP is the inherent risk of post-ERCP pancreatitis, which is especially high in patients with pancreas divisum and acute recurrent pancreatitis. In addition, minor papilla cannulation can be very challenging with a substantial failure and complication rate. These and other issues render ERCP a less than ideal modality simply for the diagnosis of pancreas divisum.
Endoscopic ultrasound provides an alternate method of evaluation of pancreas divisum. The intitial report was that the role of EUS consisted of radial instrument evaluation of 6 patients with known pancreas divisum, where the stack sign or visibility of bile and pancreatic ducts as a stack from the bulb of the duodenum was possible in only 2 of the 6 patients.9 In a subsequent study using a linear echo endoscope the continuity of the pancreatic duct was assessed prior to ERCP and comparison was made to the pancreatograms obtained at ERCP. In this study 162 patients were evaluated. In 73% the pancreatic duct was visualized well and pancreas divisum was reported in 13% with an overall sensitivity and specificity of 95% and 97%.10 Thus EUS seems to be a reasonable alternative in identifying pancreas divisum. (Figure 2) The limitations of EUS consist of operator expertise and occasional inability to visualize the pancreatic duct, which occurred in 27% of cases in the above study. In a recent study evaluating the role of EUS in a busy clinical practice over more than a decade the sensitivity of EUS was 50% with a specificity of 94.8%. A majority were evaluated with radial EUS.11 A significant advantage of doing EUS prior to considering ERCP is that it also helps identify underlying chronic pancreatitis, which may be important to establish prior to considering endoscopic or other therapy. EUS can also evaluate other parenchymal features that cannot be evaluated with ERCP, particularly pancreatic tumors which could give an impression of a divisum by pancreatography secondary to obstruction (pseudo-divisum). Moreover patients with pancreas divisum may possibly have an increased risk of developing tumors.12, 13
There are also case reports of fine needle injection of contrast into the pancreatic duct at the time of EUS in those with failed cannulation at ERCP and failure of delineation of pancreatic duct anatomy at MRCP.14 In addition, fine needle injection of methylene blue into the dorsal duct has been used to aid in endoscopic localization of otherwise obscure minor papilla.15 Finally, EUS has been used as a rendezvous technique to puncture the pancreatic duct via a transgastric route and pass a wire antegrade through the minor papilla for endoscopic access in case of failed pancreatic cannulation.16 (Figure 3)
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Figure 1 |
Figure 2 |
Figure 3 |
Magnetic resonance cholangiopancreatography is a non-invasive mode of evaluation of the biliary and pancreatic systems. Enhancement of MR imaging by stimulating the pancreas by secretin administration has resulted in better visualization and improved test characteristics, and the results are comparable to the ERCP which is the reference gold standard.17, 18 MRCP is essentially devoid of risk, and is not subject to failed cannulation. MRCP can also visualize ducts above and below strictures. In centers with high quality MRCP, secretin MRCP (sMRCP) has quickly become the method of choice for diagnosis of pancreas divisum. (Figure 4a and b). Incomplete divisum may also be diagnosed (Figure 5). In addition, some functional information can be gained with respect to degree of duct dilation after secretin stimulation, which may indicate functional obstruction at the minor papilla.
There are relatively few studies which directly compare secretin MRCP with ERCP in diangnosis of pancreatic duct anomalies. In one study, addition of secretin to MRCP improved detection of pancreas divisum by 23%, with a final sensitivity and specificity of >95% for secretin MRCP. In practice, variable quality of MRCP and inconsistent use of secretin limit the accuracy in detection of pancreatic ductal abnormalities.
The main limitation to MRCP is contraindication in patients with pacemakers, and variable quality at different centers, especially of pancreatic imaging. Use of secretin for MRCP is sporadic, and many imaging centers have not developed a protocol for its use.
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Figure 4a |
Figure 4b |
Figure 5 |
Efficacy of CT scanning to detect pancreas divisum was recently evaluated. If the pancreatic duct was visualized on a multi row detector CT then the sensitivity and specificity of CT was 90% and 97-98% to identify pancreas divisum. Inter observer agreement was excellent.19 In another study coronal reconstruction increased the sensitivity to 100% with a specificity of 90%.20 These studies had a small number of patients and larger studies are needed to generalize these results.
Endoscopic therapy of pancreas divisum consists of minor papillotomy, dorsal duct stenting, and if strictures or stones are present, dilation and stone extraction.
Studies of endoscopic therapy for PD have generally divided patients into three classes based on their clinical presentation. Patients with recurrent acute pancreatitis (RAP) have episodes of acute pancreatitis with pain and elevated pancreatic enzymes, separated by symptom free intervals of varying length. Patients with chronic pancreatitis (CP) have evidence of longstanding pancreatic disease, which may include pancreatic calcifications, duct abnormalities, and possibly, evidence of parenchymal and duct wall abnormalities detectable only by EUS. Finally, patients with pancreatic pain only have bouts of pain or continuous pain without evidence of structural abnormalities in the pancreas (other than pancreas divisum) and without associated pancreatic enzyme elevations; many of these patients have incomplete resolution of pain between exacerbations. One of the problems in interpreting the literature, and in dealing with these patients in clinical practice, is that many patients do not fit neatly into any one group: that is to say, they do have elevations in pancreatic enzymes on occasion, also have evidence of chronic pancreatitis detectable by endoscopic ultrasound but not by pancreatography, and/or also have intractable continuous abdominal pain between exacerbations.
Early data from retrospective case series suggest that endoscopic therapy may improve the clinical course of patients with RAP and pancreas divisum.21-31 Although the studies used different modalities for treatment of pancreas divisum, with some using stenting alone or in combination with endoscopic papillotomy or balloon dilation of the minor papilla, all of the interventions were aimed at reducing obstruction to flow through the minor papilla and improving drainage of the dorsal pancreatic system. Over a follow-up period of 18 to 39 months, all of these series demonstrated a decrease in either the frequency of episodes of acute pancreatitis, frequency of hospitalization, or subjective pain score compared to pre-procedure baseline. The largest of these series 29 demonstrated decreased complications with stenting after minor papillotomy compared to papillotomy alone.
The lack of control groups combined with the intermittent symptoms in patients with RAP makes the data from retrospective series difficult to interpret definitively. One randomized controlled trial attempts to clarify the role of endoscopic therapy in pancreas divisum with RAP. Lans, et al randomized 19 patients with RAP to dorsal duct stenting versus none and found a significant decrease in ER visits and hospitalizations over 30 months of follow-up.31 When combined with the data from retrospective case series, this data suggests that endoscopic therapy may be promising in patients with pancreas divisum and RAP.
The results of endoscopic therapy for chronic pancreatitis or pancreatic pain alone have been less promising than those for RAP. In all series which have also included patients with RAP, the response rates in CP and pancreatic pain patients have been lower. In the one series looking at only patients with CP and PD, less than one third were pain free at follow-up.
The available data on endoscopic therapy for pancreas divisum also highlight the potential risks associated with minor papilla interventions. Short-term complications include pancreatitis, which may occasionally be severe, particularly if the minor papilla is instrumented but a dorsal duct stent cannot be placed. A recent multicenter study found minor papillotomy to be an independent risk factor for post-ERCP pancreatitis.32 Additionally, several investigators have noted delayed risks associated with stent migration, plugged stents, and stent induced duct damage. Although improvements in technique and stent technology may ameliorate these complications, particularly use of long, unflanged, smaller caliber (3 or 4 French) stents rather than the traditional 5 to 7 French rigid flanged stents, risks of endotherapy for pancreas divisum remain salient.33
A recent large, single center, retrospective series examining endoscopic therapy for clinical syndromes associated with pancreas divisum suggests that outcomes may be less favorable than earlier data suggest for all groups.34 Through review of their experience over eight years, Gerke et al found 89 patients treated at their center for symptomatic pancreas divisum. All patients included in the study received endoscopic minor papillotomy and short-term dorsal duct stenting. Follow-up was collected by telephone interview. Although all patients were included in reporting of immediate procedural complications, which were limited to mild or moderate pancreatitis in 11%, only the 53 patients available for follow-up were included in the analysis of long-term results.
Patients were grouped for analysis based on their clinical presentation. The majority of the patients (57%) had RAP, while the remainder had either recurrent pancreatitis without complete resolution of pain between exacerbations (26%) or chronic abdominal pain without objective evidence of pancreatitis (17%). Based on their follow-up interview, patients were characterized as having immediate improvement if their symptoms were relieved following intervention and long-term improvement if they had no recurrence of symptoms at the time of follow-up. Patients who had recurrence of symptoms but good response to repeat intervention were classified as having long-term improvement.
The rate of immediate improvement following endoscopic intervention was 60% in the group as a whole, though at follow-up only 32% of the patients had continued improvement. Consistent with previous data, the clinical response in patients with RAP and PD was better than in other groups. Almost three quarters of the patients with RAP garnered immediate benefit following intervention. With over half of the patients in the study classified as having RAP, the immediate response rate in this group drives much of the immediate response rate in the study population as a whole. At follow-up, 43% of the RAP patients had long-term improvement, a rate that was not statistically different from that in the other two groups.
Also consistent with previous data, the response in patients with a component of chronic abdominal pain was poor. In patients with pancreatitis and chronic abdominal pain or chronic abdominal pain alone, the immediate response rate to minor papillotomy and stenting was less than 50%, and the long-term response was even lower (21% and 11% respectively).
Analysis of patient response based on pancreatographic assessment of the dorsal duct demonstrated a trend towards better immediate and long-term response in patients with normal dorsal duct anatomy versus those with a dilated or irregular dorsal duct, though this trend did not reach statistical significance.
This latest report of response to endoscopic therapy for symptomatic pancreas divisum highlights the shortcomings of much of the available data on the subject.35 The lack of sham controls and the presence of symptom free intervals in the majority of the patients prior to intervention makes meaningful interpretation of immediate results difficult, if not impossible. In patients with RAP, even long-term response is difficult to assess without information about pre-procedural frequency of symptoms. In patients with chronic abdominal discomfort, with or without evidence of pancreatic disease, these latest data call into question the strategy of aggressive endoscopic therapy.
One of the major problems with interpretation of these data is the lack of repeat endoscopic intervention in the majority of patients. It is well known that achieving a complete minor papillotomy may be technically difficult, especially in patients with diminutive minor papilla, and may relate to the technique used (wire-guided pull-type papillotomy versus needle-knife over a stent) and depth of incision. Restenosis and/or incomplete ablation is relatively common, and may respond to more aggressive repeat intervention. Additionally, some patients may present with pancreatic ductal strictures that require long term or repeated therapy.
To summarize, indications for minor papilla therapeutic ERCP in pancreas divisum include:
1) recurrent episodes of acute pancreatitis in the absence of other etiologies
2) chronic pancreatitis with obstruction of the dorsal pancreatic duct
3) possibly (with reservations), pancreatic-type abdominal pain in the absence of any other etiology, as long as there is evidence of functional dorsal duct obstruction by secretin-stimulated imaging.
Cannulation of the minor papilla is technically demanding and should be performed only by those trained in pancreatic endoscopic therapy. As stressed above, it is always best to know in advance that the patient has pancreas divisum by other imaging techniques, and that minor papilla therapy is indicated, prior to embarking on minor papilla cannulation. The goal is to obtain deep cannulation and wire access for therapy rather than a diagnostic study which may be difficult and potentially dangerous.
The minor papilla is generally located cephalad (anterior and superior) to the major papilla. It is preferable that one examines the minor papilla while intubating the duodenum rather than on withdrawal. For cannulation of the minor papilla a “long scope” or “semi long” scope position where there is a significant loop of the shaft of the duodenoscope in the stomach is favorable.
Once minor papilla is identified cannulation is performed using a variety of techniques. Some authors have described use of a 5 Fr catheter with a blunt tip.36 Once the cannulation is performed with the blunt tip of the catheter, small diameter wire (0.018 inch in diameter) is advanced and the catheter is exchanged for a different catheter based on the intent of therapy.
In our experience, we have found that use of a tapered tip catheter 5-4-3Fr catheter with a 0.20 inch hydrophilic wire (usually angled tip) is most useful for initial cannulation (Video 1). Once the orifice is visualized, the tip of the glidewire is used to enter the orifice without any contact by the tip of the catheter. We feel that it is particularly important not to probe at the minor papilla with the catheter as this may induce edema and reduce chances of successful cannulation. Once the wire has entered at least a cm or so, contrast can be injected through the side-arm adaptor to outline the course of the dorsal duct. It is very common for the glidewire to exit side-branch ducts, therefore contrast injection is essential to aid in redirect of the wire deep into main dorsal duct. After the hydrophilic wire is advanced to the tail, the catheter is advanced deeply into the dorsal duct over the wire, and the wire removed and exchanged for a more stable 0.018 inch Roadrunner or similar nitinol wire, over which therapy can be performed.
In pancreas divisum identifying the papillary orifice can be challenging at times since the papilla may be prominent, inconspicuous or absent. With use of various techniques, the reported success of cannulation of the minor papilla is between 77-100%.35
Intravenous secretin stimulates secretion of the pancreas which can be visualized endoscopically. Flow of the pancreatic secretion through the minor papilla helps identify the orifice and aid in subsequent cannulation. (Video 2) Synthetic secretin is now commercially available and is usually given at a dose of 15 micrograms/kg body weight. In a randomized study of 29 patients with previously failed cannulation of minor papilla, administration facilitated cannulation in 81% compared to 7.3% in the placebo group and further cross over lead to cannulation in 89%.37
Methlyene blue/Indigo carmine spray may also be useful. In some situations despite administration of secretin it is difficult to identify the minor papilla especially in those with an inconspicuous papilla. One could spray methylene blue or indigo carmine on the minor papilla or in the area anatomically representing the minor papilla. Pancreatic secretions, particularly if stimulated with secretin, wash the dye at the papillary orifice facilitating visualization of the orifice and aiding subsequent cannulation.38(Video 2)
Despite the above-mentioned techniques cannulation of minor papilla can be difficult at times. Some patients (up to 20%) have an incomplete pancreas divisum where there is a vestige communication between the dorsal and ventral pancreatic ducts. In these situations it may be possible to cannulate the ventral duct and pass a guide wire through the vestige communication so that it exits through the minor papilla. Using a mini snare the wire is pulled through the accessory channel of the duodenoscope and a catheter is passed over the wire into the dorsal pancreatic duct. In one study this technique was attempted in 6 patients with successful cannulation in all.39
If the dorsal pancreatic duct is dilated and cannulation at ERCP is unsuccessful percutaneous puncture of pancreatic duct under ultrasound guidance with subsequent endoscopic exchange or rendezvous techniques have been described; however these are quite risky and technically difficult.40 We have recently reported using endoscopic ultrasound to puncture the pancreatic duct and pass a guidewire antegrade for subsequent endoscopic rendezvous.16 The advantage of this technique over the percutaneous approach is that it performed at one setting in the same unit as the ERCP, and may have less morbidity than the percutaneous approach.
Minor papillotomy
Once minor papilla access is achieved, minor papillotomy can be performed either with a wire-guided traction sphincterotome (Figure 6a-c) , or via needle-knife over a previously placed stent. We prefer the wire-guided traction technique, but use a pure cutting current (which can be achieved with ERBE-type generators), and use a very small amount of cutting wire (1-2mm) in contact with the tissue, to avoid cutting too deep. (Video 1) There is a definite propensity either to cut too little, which is ineffective and likely to restenose, or to cut too deep, in which perforation (rarely seen after minor papillotomy), or more likely scarring of the duct and subsequent stricturing may result. Finding the right balance is quite challenging and requires substantial experience, and examination of the individual anatomic papillary and ductal landmarks of each patient.
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Figure 6a |
Figure 6b |
Figure 6c |
Repeat intervention is often required in patients with pancreas divisum, particularly retreatment of stenotic or incomplete minor papillotomies. This may require careful extension of the papillotomy, or balloon dilation followed by stent placement. Tattooing of the minor papilla in those with an obscure papillary orifice requiring multiple endoscopic interventions has been described.41
Irrespective of the techniques adapted for cannulation one should place a stent in the pancreatic duct since the risk of post ERCP pancreatitis is high in this group. If no further intervention is planned, use of a stent with no internal flange, which will spontaneously fall out, is useful. Placing a longer (8 to 10cm) small caliber (3 or 4 Fr) unflanged single pigtail stent is generally recommended, as these stents probably cause less ductal injury compared to larger stents with internal flanges, and also tend to fall out spontaneously within two weeks. (Figure 7). Larger 5-7 French or multiple stents are generally recommended only for treatment of papillary restenoses or strictures.
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Figure 7 |
Any pathology that can occur in chronic or acute pancreatitis may occur in the dorsal duct of patients with pancreas divisum. Thus treatment of duct leaks, communicating pseudocysts, strictures, or dorsal pancreatic duct stones may be indicated. The techniques are similar to those employed via the major papilla.
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