Preprocedural Planning (see also Chapter 9)

In addition to standard laboratory testing and obtaining plain abdominal radiographs of the pancreatic area or abdominal computed tomography (CT) scan for detection of pancreatic calcifications, magnetic resonance imaging (MRI) is currently the best modality for the selection of patients who may benefit from endoscopic treatment and for planning endoscopic therapy (Fig. 52.1).

Fig. 52.1 Example of pretherapeutic planning in a patient with CP and severe pain. The plain film (A) shows a dense calcification, which is even more clearly visible on an unenhanced CT scan (B), while the dynamic S-MRCP shows an impacted stone at the level of the genu of the pancreas, with upstream dilation, while the distal MPD is normal size (C). This patient will undergo ESWL before any endoscopic intervention.

MRI performed with secretin stimulation (S-MRCP) allows information about pancreatic ductal anatomy, presence of peripancreatic fluid collections, and possible obstruction of the bile duct to be determined. Moreover, S-MRCP can be used to quantify pancreatic exocrine function and to evaluate the short- and long-term effects of pancreatic ductal drainage procedures (Fig. 52.2).^13,14

Fig. 52.2 A patient with a residual prepapillary stricture after extraction of stone fragments (A), treated by placement of two 8.5 Fr stents side by side (B). The comparison of S-MRCP performed before (C) and after (D) drainage shows the decrease in MPD diameter and earlier duodenal filling of pancreatic secretions.

MPD Cannulation and Endoscopic Pancreatic Sphincterotomy

MPD cannulation and endoscopic pancreatic sphincterotomy (EPS) are the first steps of pancreatic endoscopy and provide improved access to the MPD. Minor papilla sphincterotomy may be needed in up to 20% of patients in cases of dominant dorsal duct anatomy (complete or incomplete pancreas divisum, ansa pancreatica). In a small subset of patients, EPS itself may resolve papillary stenosis and allow the removal of small floating pancreatic duct (PD) stones. In Western countries, calcifications in the head of the pancreas seen on routine radiographic images and unenhanced abdominal CT almost always implies that PD stones are deeply impacted in the ductal wall and will be very difficult to remove. In these cases, ESWL should be performed prior to attempted endoscopic intervention and, as more recently shown, may be the only intervention required in selected patients.

Biliary sphincterotomy performed before EPS is performed in the setting of cholangitis or obstructive jaundice or when it is technically necessary to facilitate access to the PD. If a biliary sphincterotomy is performed, the PD orifice is located between the 3 o’clock and 6 o’clock positions on the right margin of the sphincterotomy. After pancreatic opacification, a hydrophilic guidewire (Terumo Inc., Japan; Glidewire, Boston Scientific, Natick, Mass.) can be maneuvered through the stricture or alongside the stones, using a torque device under radiologic guidance (Fig. 52.3). Pancreatic sphincterotomy is then performed over the guidewire after deep cannulation with a standard or tapered pull-type sphincterotome. We prefer to use pure cutting current, extending the incision to the duodenal wall. The same technique can be used for minor papilla sphincterotomy (see Chapters 19 and 20). Alternatively, a PD stent can be inserted into the PD and sphincterotomy performed with a needle knife over the stent.

Fig. 52.3 The use of a minitome (Cook Endoscopy, Winston-Salem, N.C.) with a 0.018 J-tip Terumo guidewire manipulated by the assistant using a torque device offers the best performance for cannulating difficult and tortuous strictures under fluoroscopic control.

Extracorporeal Shock Wave Lithotripsy

In tertiary referral centers that specialize in endoscopic management of severe chronic pancreatitis, ESWL is often performed before endoscopic therapy is undertaken. High-resolution plain films of the pancreatic area are taken in left and right oblique positions to define location of stones and to optimize ESWL delivery, as the fluoroscopy used during lithotripsy is of lower resolution.

Technically, it is important to use a lithotriptor with a bidimensional x-ray focusing system and a high-power generator. Ultrasonic localization of pancreatic stones lacks precision. When performed under general anesthesia or deep sedation, 3000 to 6000 shock waves can be applied at an intensity of 0.33 to 0.54 mJ/mm², which provides complete stone fragmentation after a median of one session, though in our experience up to five sessions may be needed.^15,16 With the patient in the prone position the shock wave generator is placed to the patient’s right side when stones are located in the head of the pancreas and to the patient’s left side when stones are located in the body or tail of the pancreas. ESWL is much more effective for fragmentation of calcium carbonate pancreatic stones than for biliary stones. Stones fragmented into millimeter size can usually be easily removed during endoscopic retrograde cholangiopancreatography (ERCP) (Fig. 52.4). When the lithotriptor is located within or close to the endoscopy unit, ESWL and therapeutic ERCP may be performed consecutively during one general anesthetic session.

Fig. 52.4 The same patient as in Fig. 52.1. Successful fragmentation (A versus B) after ESWL is illustrated by a decrease in radiologic density, an increase of the stone surface area, and heterogeneity of the stones (powderlike material). After fragmentation a pancreatic sphincterotomy is performed (C), a guidewire is inserted in the pancreatic duct (D), and a small Dormia basket (E) is maneuvered alongside the guidewire to remove the stone fragments. At the end of the procedure a nasopancreatic catheter is left in place (F).

Intraductal Lithotripsy

Some endoscopists have reported successful pancreatic stone fragmentation using intraductal mechanical lithotripsy.¹⁷ However, the success of mechanical lithotripsy depends on the ability to capture the stone within the basket, which is most often impossible with impacted, calcified stones. A pulsed dye-laser lithotriptor has also been used to fragment pancreatic stones under direct endoscopic visualization with a pancreatoscope (see Chapter 25) or using fluoroscopic guidance alone.^18,19 Laser lithotripsy has proven to be effective in a minority of patients. Intraductal fragmentation remains anecdotal and is not as effective as ESWL. ESWL is the gold standard for pancreatic stone fragmentation because of its efficacy, simplicity, and relative lack of adverse events.

Stone Extraction and Dilation

After ESWL, minute stone fragments can be visualized within the PD. If located upstream to a stricture, the stricture is dilated using a 4- to 6-mm balloon (Maxforce, Boston Scientific) to facilitate stone removal. We prefer to use a small Dormia basket to remove stone fragments (Fig. 52.4). When stones are visible on fluoroscopy, a useful trick is to introduce a guidewire into the MPD and then follow with the Dormia basket using minimal or no contrast injection, which allows fluoroscopic localization of residual fragments that become isodense when contrast is injected, and then the basket can be manipulated to trap them. Most often the basket is left opened in the duct, turning on its axis while gently perfusing the duct with saline. A slightly inflated balloon catheter may be used in some cases but is of limited use in the pancreas because sharp stone fragments frequently rupture the balloons. Tight strictures are often present and although balloon dilation is used most frequently, bougies (Soehndra dilators, Cook Endoscopy, Winston-Salem, N.C.) may be necessary; in a case of strictures in which catheter passage proves impossible, a Soehendra screw stent retriever (8.5 Fr) can usually be rotated through the stricture to allow subsequent passage of a dilation balloon (Fig. 52.5).

Fig. 52.5 Usual techniques of dilation. A, A 4 cm × 6 mm Maxforce balloon is inflated through the stricture, the imprint of which is visible at the beginning of inflation. B, A biliary bougie is passed over a guidewire. C, In extremely tight strictures an 8.5 Fr Soehendra stent retriever is rotated through the stricture to create the room necessary for insertion of a balloon. In this case, after dilation the stent retriever should be removed while turning it counterclockwise in order to avoid the risk of displacing the guidewire.

If multiple endoscopic sessions are necessary for fragmentation and removal of stones, a nasopancreatic catheter (NPC) (see Chapter 21) is left in place for drainage between sessions. This may decrease the risk of acute pancreatitis due to fragment impaction.²⁰ NPC placement can also be used to predict the need for pancreatic stenting; if NPC perfusion is well tolerated without producing pain, an underlying significant MPD stricture duct is unlikely and stent placement may be avoided. In contrast, if NPC perfusion is painful, the catheter should be placed for gravity drainage and further stone extraction or stent placement should be performed.

Stent Placement

When an obstructed MPD stricture is present, adequate outflow from the pancreas to the duodenum must be achieved by PD stent placement. In contrast to stent placement to prevent post-ERCP pancreatitis in high-risk patients (see Chapter 7), multiple and larger diameter (7 to 10 Fr) stents are used. Stent lengths are selected based on pancreatic duct length and stricture location. Our approach is to replace stents every 6 months or “on demand” when symptoms recur; stents remain in place for up to 2 years. Stent placement has evolved from single to multiple side-by-side stents. Two 8.5 Fr stents usually can be placed after a dilation to 6 mm. The number of stents can be further increased over successive exchanges if the upstream ductal diameter of the pancreas allows it (Fig. 52.2). This approach has been used to reduce duration of stenting and prolong symptom relief.²¹ Multiple stent placement is facilitated by placement of two guidewires across the stricture followed by successive stent placement. This technique avoids the need to recannulate the pancreatic duct and negotiate a guidewire across a tight stricture with a stent already in place.

The use of the Fusion system (Cook Endoscopy) allows intraductal exchange and placement of multiple side-by-side stents without losing access and using only one guidewire (see Chapter 21). This system has become our preferred technique for placement of multiple 8.5 Fr plastic pancreatic stents.