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Pancreatoscopy
Peroral pancreatoscopy, in which a small-caliber fiberscope (“baby scope”) is inserted into the pancreatic duct from the papilla through the working channel of a duodenoscope (“mother scope”), was first described by Japanese investigators Takagi and Takegoshi in 1974. Although the idea was very attractive and several investigators studied its feasibility, pancreatoscopy was not widely adopted because of poor visibility and instrument fragility, as well as the relatively large diameter of the instrument compared with the pancreatic duct. The description of intraductal papillary mucinous neoplasm (IPMN) by another group of Japanese investigators, Ohashi et al., made an impact on pancreatoscopy in the early 1980s. This tumor was characterized by mucin secretion with a patulous papilla and a dilated pancreatic duct and was a good indication for pancreatoscopy. Since then, pancreatoscopy has been reassessed as a useful modality for the diagnosis of IPMN showing characteristic endoscopic findings.
Two types of fiberoptic pancreatoscopes were mainly used in previous studies. One is a thin fiberscope (diameter 3.1 to 3.7 mm) that has two-way tip deflection and a working channel. Biopsies can be taken under direct vision, but pancreatic sphincterotomy is usually needed for endoscope insertion because of its large diameter. To insert the scope into a nondilated pancreatic duct, an ultrathin pancreatoscope (diameter 0.75 to 0.8 mm) was also developed by decreasing the number of optical fibers. This scope can be inserted via a standard endoscopic retrograde cholangiopancreatography (ERCP) cannula without the need for sphincterotomy; however, neither tip deflection nor a working channel is present. Cytology sampling and injection of saline were performed through the outer cannula. These fiberscopes suffered the same problem of poor visibility, contingent on the number of optical bundles.
Several recent developments have rekindled interest in pancreatoscopy. The first is the emergence of video (electronic) pancreatoscopes, first made by our group with the development of a miniature charge-coupled device (CCD) video chip in 1999. Video pancreatoscopes provide drastically improved resolution of images of the pancreatic duct compared with those obtained using fiberoptic pancreatoscopes ( Fig. 26.1 ). This development has led to pancreatoscopy with adjunct imaging techniques such as narrow-band imaging (NBI). The second is the development of the SpyGlass Direct Visualization System. This single-operator cholangiopancreatoscopy system was first applied to the biliary tree in 2006. The external diameter (10.5 Fr) of the current miniscope is greater than that of most normal pancreatic ducts and may limit pancreatic applications. However, SpyGlass pancreatoscopy has been applied in the investigation of the dilated pancreatic duct (see Chapter 37 ) with IPMN and in endotherapy for pancreatic stones in selected patients with chronic pancreatitis (see Chapter 55 ).
Video pancreatoscopic images of the pancreatic duct in a normal subject. Fine capillary vessels are clearly visualized on the surface of the pancreatic duct.
( A, From Kodama T, Sato H, Horii Y, et al. Pancreatoscopy for the next generation: development of the peroral electronic pancreatoscope system. Gastrointest Endosc. 1999;49:366–371. B, From Kodama T, Koshitani T, Sato H, et al. Electronic pancreatoscopy for the diagnosis of pancreatic diseases. Am J Gastroenterol. 2002;97:617–622.)
Equipment and Technique
Video Pancreatoscope
At present, Olympus Medical Systems Co. (Tokyo, Japan) offers two types of video pancreatoscopes in Japanese markets. The first type (CHF-BP260) is a thin scope with a 2.6-mm outer diameter and a 0.5-mm working channel. The second type (CHF-B260) is a larger scope with a 3.4-mm outer diameter and a 1.2-mm working channel that permits use of a 0.035-inch guidewire, a 3-Fr biopsy forceps, and an electrohydraulic or laser lithotripsy probe ( Fig. 26.2 ). These scopes use a field sequential imaging system and can be passed through the 4.2-mm working channel of a therapeutic duodenoscope. In the United States these video pancreatoscopes are not commercially available, and only the use of a prototype digital pancreatoscope (CHF-Y0002B; Olympus) is reported. The specifications of available fiberoptic and video pancreatoscopes are compared in Table 26.1 . All baby scopes require a dedicated light source and image processor. Both video pancreatoscopes (CHF-BP260, B260) can be used with a processor (CV-260SL/CV-290; Olympus) for NBI examinations. The baby scope image is projected onto a separate video monitor ( Fig. 26.3 ).
TABLE 26.1
Specifications of Available Fiberoptic and Video Pancreatoscopes and Single-Operator Cholagiopancreatoscopy Systems
| Imaging System | Tip Diameter (mm) | Working Channel (mm) | Tip Deflection (Degrees) | Field of View (Degrees) | |
|---|---|---|---|---|---|
| CHF-BP30 (Olympus) | Fiberoptic | 3.1 | 1.2 | 2-way, 160/130 | 90 |
| FCP-9P (Pentax) | Fiberoptic | 3.0 | 1.2 | 2-way, 90/90 | 90 |
| CHF-BP260 * (Olympus) | Video (field sequential) | 2.6 | 0.5 | 2-way, 70/70 | 90 |
| CHF-B260 * (Olympus) | Video (field sequential) | 3.4 | 1.2 | 2-way, 70/70 | 90 |
| SpyGlass DS (Boston Scientific) | Video | 3.4 | 1.2/0.6/0.6 | 4-way, 30/30/30/30 | 70 |
Two-Operator “Mother–Baby” Method
Peroral pancreatoscopy is performed during ERCP, usually with the patient in the prone position. Using a two-operator method, one endoscopist operates the mother duodenoscope and the other operates the baby scope ( Fig. 26.4 ). The duodenoscope is positioned at the ampulla and the baby scope is inserted through the working channel of the duodenoscope. A prior pancreatic sphincterotomy or balloon sphincteroplasty is typically needed when inserting a relatively large pancreatoscope. Intubation with the baby scope is performed by the endoscopist who operates the duodenoscope. Given that the baby scope is fragile at the bending part of its tip, care is taken to advance the baby scope with the elevator of the duodenoscope when maximally opened. For baby scopes equipped with a 1.2-mm working channel, inserting the baby scope over a guidewire reduces the need for elevator use and minimizes the risk of scope damage. Alternatively, for baby scopes with a 0.5-mm working channel, the scope must be inserted directly into the pancreatic duct.
Once in the pancreatic duct, the baby scope can be advanced deeply under both direct endoscopic and fluoroscopic guidance. The torturous pancreas head is the most difficult part to pass. The baby scope is mainly steered by the endoscopist handling the duodenoscope, while repositioning the duodenoscope relative to the papilla. The endoscopist handling the baby scope can fine-tune the view using tip deflection. Water irrigation is usually needed to optimize visualization. Protein plugs in the pancreatic duct may impair visualization and need to be irrigated with sterile saline solution. Intravenous secretin (100 units) has been used to stimulate pancreatic juice flow in an effort to improve visualization of the pancreatic duct. To facilitate insertion of accessories such as biopsy forceps or a lithotripsy probe, the elevator of the duodenoscope needs to be relaxed and the angulation of both the duodenoscope and the baby scope reduced.
Single-Operator Cholangiopancreatoscopy
The SpyGlass Direct Visualization System (Boston Scientific, Marlborough, MA), although only recently developed, has been applied for pancreatoscopy. The first-generation system had a 10-Fr disposable four-lumen catheter (SpyScope, now called Spy Legacy) containing a 0.9-mm channel for the SpyGlass fiberoptic probe, a 1.2-mm instrumentation channel, and two dedicated 0.6-mm irrigation channels. The current system has two light-emitting diode lights on the catheter tip and a single complementary metal-oxide semiconductor chip for imaging that provides improved resolution (×4) and a 60% wider field of view than the first-generation system. The SpyScope catheter has four-way tip deflection (each more than 30 degrees), is strapped to the duodenoscope just below the operating channel, and is operated by a single endoscopist (see Table 26.1 ) ( Fig. 26.5 ).
The SpyScope is inserted through the 4.2-mm working channel of a therapeutic duodenoscope. In most cases, a small pancreatic sphincterotomy is required to insert the scope into the pancreatic duct. The SpyScope is usually inserted over the guidewire under combined fluoroscopic and visual guidance. The clarity of the luminal visual field improves significantly with water irrigation via two dedicated irrigation channels connected to the irrigation pump. Intermittent sterile saline irrigation at the minimal setting is recommended for pancreatic use. Biopsy specimens can be obtained using the 3-Fr SpyBite forceps under direct visualization. The 1.2-mm working channel of the SpyScope also allows insertion of an electrohydraulic or laser lithotripsy probe for stone fragmentation under direct vision.
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