Application value of MRI examination in classification diagnosis of rectal mucinous adenocarcinoma

Objective To investigate the application value of magnetic resonance imaging (MRI) in the classification diagnosis of rectal mucinous adenocarcinoma. Methods The retrospective and descriptive study was conducted. The clinical data of 74 patients with rectal mucinous adenocarcinoma who were admitted to Chongqing Traditional Chinese Medicine Hospital from July 2009 and February 2019 were collected. There were 40 males and 34 females, aged (46±8)years, with a range from 32 to 82 years. Among the 74 patients, 41 were simple mucinous adenocarcinoma, 26 were partial mucinous adenocarcinoma, and 7 were focal or small foci mucinous adenocarcinoma. All patients underwent MRI plain scan and dynamic enhanced scan. Observation indicators: (1) morphology of rectal mucinous adenocarcinoma; (2) the lesion margin of rectal mucinous adenocarcinoma; (3) the value of apparent diffusion coefficient (ADC) of rectal mucinous adenocarcinoma; (4) internal enhancement features of rectal mucinous adenocarcinoma; (5) timesignal intensity curve of rectal mucinous adenocarcinoma. Measurement data with normal distribution were represented as Mean±SD, and count data were described as absolute numbers. Results (1) Morphology of rectal mucinous adenocarcinoma: 74 patients had different morphological changes. Among the 41 cases of simple mucinous adenocarcinoma, 22 were oval, 8 were round, and 11 were irregular. Among the 26 patients with partial mucinous adenocarcinoma, 15 were oval, 8 were round and 3 were irregular. Among the 7 patients with focal or small foci mucinous adenocarcinoma, 2 were oval, 1 was round and 4 were irregular. (2) The lesion margin of rectal mucinous adenocarcinoma: the lesion margin of 74 patients was mainly unclear and irregular. Among the 41 cases of simple mucinous adenocarcinoma, 32 had unclear and irregular margin, 7 had clear margin, and 2 had unclear margin combined with fissure. Among the 26 cases of partial mucinous adenocarcinoma, 20 had unclear margin combined with fissure, 5 had unclear margin and irregular margin, and 1 had clear margin. Among the 7 patients with focal or small foci mucinous adenocarcinoma, 5 had unclear or irregular margin, 1 had unclear or irregular margin, and 1 had clear margin. (3) The value of ADC of rectal mucinous adenocarcinoma: diffusion weighted imaging of 74 patients showed diffused limited changes. The average ADC value was (1.24±0.23)×10-3 mm2/s of 41 patients with simple mucinous adenocarcinoma, (0.91±0.42)×10-3 mm2/s of 26 patients with partial mucinous adenocarcinoma, and (1.07±0.24)×10-3 mm2/s of 7 patients with focal or small mucinous adenocarcinoma. (4) Internal enhancement features of rectal mucinous adenocarcinoma: 74 patients showed delayed heterogeneous enhancement and marginal enhancement. Among 41 cases of simple mucinous adenocarcinoma, 24 showed delayed heterogeneous enhancement, 17 showed marginal enhancement, and none showed homogeneous enhancement. Among 26 patients with partial mucinous adenocarcinoma, 20 showed marginal enhancement, 6 showed homogeneous enhancement, and none showed heterogeneous enhancement. All the 7 cases of focal or small foci mucinous adenocarcinoma showed heterogeneous enhancement. (5) Timesignal intensity curve of rectal mucinous adenocarcinoma: 74 patients showed mainly outflow type in the timesignal intensity curve. Among the 41 cases of simple mucinous adenocarcinoma, 22 presented progressive curve, 12 presented platform type, and 7 presented outflow type. Among the 26 patients with partial mucinous adenocarcinoma, 17 presented outflow type, 8 presented platform type, and 1 presented progressive type. Among the 7 patients with focal and small forci mucinous adenocarcinoma, 4 presented outflow type, 2 presented platform type, and 1 presented progressive type. Conclusions MRI findings show different results for different types of rectal mucinous adenocarcinoma. A correct understanding of the MRI features of different types of rectal mucinous adenocarcinoma is helpful for the classification diagnosis of rectal mucinous adenocarcinoma. Key words: Rectal neoplasms; Rectal mucinous adenocarcinoma; Mucous lake; Magnetic resonance imaging