Direct Pancreatoscopy

Objectives and Basic Principles

Several imaging procedures, including transabdominal and endoscopic ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI) and endoscopic retrograde cholangiopancreatography (ERCP), have been established for the diagnosis of pancreatic diseases. Among them, ERCP is the current gold standard for diagnosis of pancreatic cancer as well as other diseases involving the pancreatic duct. However, it may fail to differentiate strictures or intraluminal filling defects of the pancreatic duct. It may also fail to detect minimal change, and chronic pancreatitis may not be well visualized with contrast medium. Given these limitations, it is necessary to have a modality with a direct approach to the pancreatic duct. Based on this concept, Japanese endoscopists, including Takekoshi et al. [1], first developed peroral pancreatoscopy through the accessory channel of a duodenal fiberscope in 1975. However, this device proved unpopular in clinical use because of problems which included instrument expense, fragility, low visibility, and its relatively large diameter relative to the duodenal papilla.

Pancreatoscopy was reassessed and found to be useful for a variety of conditions, including intraductal papillary mucinous tumor (IPMT), first described by Ohashi et al. [2] in 1982. Initial pancreatoscope prototypes had no channel or tip deflection, although subsequent devices of more than 3 or 4 mm in diameter were manufactured with one- or two-way tip deflection, and with an accessory channel with potential use for biopsy or lithotripsy [3] [4]. To make insertion of the scope easier, an ultrathin pancreatoscope (0.8 mm in diameter) was developed by decreasing the number of image guide fibers [3] [5]. Finally, the peroral electronic pancreatoscope (PEPS), the smallest known electronic endoscope, was developed recently for superior visualization within the pancreatic duct [6]. With the above advances in technology and imaging, peroral pancreatoscopy has now evolved as a useful technique both in diagnosis and therapeutic procedures within the pancreatic duct, although most procedures continue to be performed in advanced centers of endoscopic excellence.

Intraductal Papillary Mucinous Tumor (IPMT)

In patients with IPMT and equivocal radiographic findings, pancreatoscopy provides valuable information for the differential diagnosis of amorphous filling defects in the main pancreatic duct, and makes possible a definite diagnosis based on the characteristic appearance of papillary tumors and biopsy under direct visualization. Pancreatoscopy also provides valuable information in assessing the extent of the lesion and multicentric lesions, in order to select the best surgical procedure. Kaneko et al. [7] reported that intraoperative pancreatoscopy was effective for determining the resection line of the pancreas during surgery. Pancreatoscopy has also been reported to be useful in the differentiation of benign mucin-producing tumors of the pancreas from more dysplastic lesions [8]. A case report describing IPMT investigated with PEPS has also supported the use of this technique in the differential diagnosis of mucin-producing neoplasms [9].

Differentiation of Stenosis of the Main Pancreatic Duct (Benign or Malignant)

Many series using direct pancreatoscopy have attempted to distinguish focal or chronic pancreatitis from neoplasia. Stenoses with scar formation or mucosal edema are usually observed in chronic pancreatitis, while those with friable erythematous mucosa and erosive changes are more common in pancreatic cancer. Thus, stenoses of benign lesions are usually differentiated from those of pancreatic cancer by direct pancreatoscopy [3] [4] [5] [9]. However, a compressed pancreatic duct wall covered with normal epithelium can be observed in extrinsic malignancy which does not involve the epithelium of the pancreatic duct at the distal site of the stenosis. This can lead to a false-negative diagnosis unless pancreatoscopy is combined with other imaging modalities. Miyakawa et al. [10] classified endoscopic cancerous changes into two groups: superficial and compressed. They reported that malignant cells were detected histopathologically in 41 % of the superficial type and in none of the compressed type, based on transpapillary biopsy or brush cytology.

Early Detection of Pancreatic Cancer

Because most pancreatic cancers are derived from pancreatic duct epithelium, pancreatoscopy can contribute to the diagnosis of early pancreatic cancer if it is located within the main pancreatic duct. Uehara et al. [11] reported diagnosis of in situ carcinoma of the pancreas by peroral pancreatoscopy and pancreatoscopic cytology. They collected pancreatic juice from abnormal sites of the pancreatic duct seen by peroral pancreatoscopy. This method was felt to add significant yield when compared with pancreatic juice cytology sampling obtained by means of the catheter at the time of ERCP. Although there has not been a comprehensive study investigating peroral pancreatoscopy for in situ carcinoma of the pancreas, these authors reported that papillary mucosa, rough mucosa, or nodular mucosa in the pancreatic duct are findings in carcinoma in situ.

Further Investigation and Management of Chronic Pancreatitis

In pancreatoscopic investigation of chronic pancreatitis, protein plugs and calcified stones are found to coexist within turbid pancreatic juice. Findings in the duct characteristically include whitish, rough, scar-like, or erythematous mucosa, with or without side-branch ectasias or smooth stenoses [12]. Fine capillary vessels on the surface of the pancreatic duct are frequently blurred. With the improved resolution of electronic pancreatoscopy, these findings can be observed and analyzed much more precisely than those observed through a conventional fiberoptic scope. This is particularly helpful when the ERCP image is equivocal with regard to the Cambridge criteria of chronic pancreatitis [6] [13]. It is possible that new diagnostic criteria for chronic pancreatitis will be established by electronic pancreatoscope images in the future.

For the management of pain of chronic pancreatitis, lithotripsy has been used to fragment pancreatic duct stones in selected cases. To date, laser and electrohydraulic lithotripsy have been reported in a limited number of patients [14] [15]. Intraoperative electrohydraulic lithotripsy has also been reported to improve the outcome in the surgical management of chronic pancreatitis [16]. Confirmation of clearance of the duct by direct pancreatoscopy has been recommended after all techniques of endoscopic stone management, but this recommendation remains controversial.

References

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• 14 Neuhaus H, Hoffmann W, Classen M. Laser lithotripsy of pancreatic and biliary stones via 3.4 mm and 3.7 mm miniscopes: First clinical results.  Endoscopy. 1992;  24 208-214
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• 16 Tanaka M, Yokohata K, Kimura H. et al . Intraoperative endoscopic electrohydraulic lithotripsy of pancreatic stone.  Int J Pancreatol. 1992;  12 227-231
• 17 Zkan H, Saisho H, Yamaguchi T. et al . Clinical usefulness of a new miniscope in the diagnosis of pancreatic disease.  Gastrointest Endosc. 1995;  42 480-485