Russian Scientific Center of Surgery n.a. academician B.Petrovsky, Moscow, RUSSIA
The aim of the study. To evaluate the possibilities of transrectal ultrasound examination by using three-dimensional reconstruction in the diagnosis of rectal cancer.
Materials and methods. For the period from May 2009 to March 2011 the RSCS named after academician B.V. Petrovsky of the RAMS there were examined 62 patients with the diagnosis of rectal cancer. Transrectal ultrasound was performed on the BK-MedicalProFocus 2202 (USA) device with the use of transrectal probe with scan rate of 6.0 - 12MHz with a 360 ° scanning and application of three-dimensional reconstruction. Results of ultrasound investigation were compared with pathomorphologic data, intraoperative surgical findings and MRT data. Parameters of the rectal wall, fascial mezorectum package, signs of metastatic lymph nodes were evaluated.
Results. Ultrasound picture of rectal cancer was characterized by changes in wall thickness, its five-layer structure and external contour.
In all patients there was observed thickening of the wall on the affected area subject to the degree of infiltration by a tumor process.
In case of cancerous lesions five-layer structure of the rectal wall disrupted. Violation of the integrity of the hypoechoic muscular layer, uneven and fuzzy outer contour of intestine, were considered as the invasion of the tumor into the mesorectal tissue, accompanied by the change of mesorectal echostructure. During the spread of cancer beyond the mesorectal fascia, there was determined violation of the integrity of fascia and signs of tumor invasion into adjacent organs. In the absence of spread of tumor to surrounding organs hyperechoic layer was visualized between them. In the presence of tumor invasion into adjacent organs there was observed disappearance of boundaries between the tumor and organ.
In case of the involvement of the anal ring into the neoplastic process there was identified a fuzzy and uneven outer contour of the wall of the anal canal, with the violation of a five-layer structure. In case of the spread of a tumor into the puborectal loop, its echogenicity and echostructure changed. A characteristic feature of affected regional lymph nodes is the increase of their size, round shape, reduced echogenicity and lack of cortico-medullar differentiation. According to the results of transrectal ultrasound in 6 (9.7%) patients there was detected metastatic involvement of only the mucosal and submucosal layers. 13 (21%) patients had signs of the infiltration of the muscular layer. In 26 (42%) cases the tumor projected beyond the boundaries of the rectum and invaded into mesorectal fiber. In 17 (27%) patients the tumor invaded into the mesorektal fascia, of them 7 (11.3%) patients had ultrasound evidence of tumor invasion into adjacent organs. After surgical resection en block in 3 of 7 patients, no invasion into the adjacent organs was found according to morphological data. This is due to the complexity of the differentiation of ultrasonic signs of perifocal inflammation process surrounding the tumor and infiltrative tumor growth. In 5 (8.1%) cases, the tumor process involved anal canal. In 2 of 5 cases the puborectal loop was affected. In 56 (90.3%) patients enlarged lymph nodes of the first order with a modified echostructure were detected. According to our data, the accuracy of transrectal ultrasound examination of rectal cancer constitutes 92.1%, sensitivity 98%, specificity 86.1%.
Conclusions: Transrectal ultrasound examination with the application of a three-dimensional reconstruction accurately determines the structure of the tumor, depth of invasion of the rectal wall, surrounding tissues and organs.