Reply to Matsushita et al.

We thank Drs. Matsushita et al. for their letter and interest in our article [1]. Duodenal duplication cyst (DDC) is a benign congenital anomaly acquired during embryonic development of the digestive system [2]. Surgical resection is the standard therapy [3] [4]; however, the difficulty of the operative procedure owing to the close proximity of the major papilla has resulted in an interest in endoscopic therapies. Using the endoscopic needle-knife and sphincterotome to open the cyst into the duodenum [5] and endoscopic partial resection of the cyst [6] [7] are the favored endoscopic methods.

A new endoscopic treatment method involving needle-knife sphincterotome incision, balloon dilation, and plastic stent implantation for a symptomatic duodenal cystic lesion was described in our article [1]. Our diagnosis for the duodenal cystic lesion was DDC; Matsushita et al. suggest a diagnosis of choledochocele rather than DDC.

In fact, exact distinction between choledochocele and DDC is only possible at pathological examination. Matsushita et al. are justified in their suspicion since no biopsy from the cystic lesion was performed in our case. However, there were three findings which persuaded us to a diagnosis of DDC: (i) In general, DDC is a cystic lesion located distal to the orifice of the papilla, while a choledochocele is located proximal to the orifice of the papilla. In our case, the orifice of the papilla was found at the back side of and proximal to the cystic lesion, as seen in Fig. 1b in our article. (ii) Although the common bile duct and the pancreatic duct were opacified through the common channel, the cystic lesion showed no direct communication with the common bile duct, as may be seen in Fig. 1c,d. (iii) During the endoscopic therapeutic procedure, we observed drainage of a whitish viscous secretion, but not bile, from the cystic lesion. It has been speculated that a DDC might produce viscid mucous secretions [8]; on the other hand, a choledochocele would be expected to contain bile.

When the above findings are considered, a diagnosis of DDC is more likely than one of choledochocele. We suggest that follow-up endoscopic biopsies should not be omitted in such cases, since there are several reported cases of malignancy arising inside a DDC [9] [10] [11].

Competing interests: None

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