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Transvaginal Sonography as an Adjunct to Endorectal Sonography in the Staging of Rectal Cancer in Women

¹ Department of Medical Imaging, Toronto General Hospital, University of Toronto, 585 University Ave., Toronto, ON M5G 2C4, Canada.
² Present address: Diagnostic Imaging, Henderson General Hospital, Hamilton, ON L8V 1C3, Canada.
³ Department of Medical Imaging, St. Joseph's Health Centre, University of Toronto, Toronto, ON M6R 1B5, Canada.

Received August 30, 2004; accepted after revision April 19, 2005.

 
Address correspondence to S. R. Wilson (stephanie.wilson{at}uhn.on.ca).

Abstract

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OBJECTIVE. The purpose of this study was to evaluate the contribution of transvaginal sonography (TVS) in the staging of rectal cancer in women.

MATERIALS AND METHODS. Sixty women with rectal tumors underwent TVS. Forty-five of the 60 women also underwent endorectal sonography. Forty-nine of the women had rectal carcinoma; nine, tubulovillous adenoma; and two, gastrointestinal stromal tumor confirmed at surgical pathologic examination (n = 41) and biopsy before chemoradiation therapy (n = 19). Four of the 49 rectal carcinomas were T1; seven, T2; 35, T3; and three, T4. Images from TVS and endorectal sonography were shown independently to two blinded reviewers, who staged the tumors and assessed examination adequacy for tumor presence, size, and depth and nodal status. Staging results with TVS were compared with those obtained with endorectal sonography and histopathologic examination.

RESULTS. All tumors were seen with TVS. In 30 of the 49 rectal carcinomas confirmed at surgical pathologic examination TVS tumor staging was accurate in 25 (83.3%) of the cases. Two (6.7%) of the 30 tumors were understaged, and 3 (10%) were overstaged. All tumors selected for chemoradiation (n = 19) were correctly staged T3. Endorectal sonography was suboptimal for tumors that were stenotic (n = 3), large (n = 2), high at the rectosigmoid junction (n = 4), or low at the anal canal (n = 3). In these 12 cases, TVS successfully depicted the lesion, and the images gave enough information for prediction of stage. In interpretation of the images of 45 patients who underwent both TVS and endorectal sonography, the blinded reviewers had good agreement and comparable accuracy for staging in adequate examinations with each technique. Four of the nine villous adenomas were overstaged as T1 on TVS. Gastrointestinal stromal tumors manifested as intramural vascular masses.

CONCLUSION. TVS is an excellent adjunct to endorectal sonography in the staging of rectal cancer in women. It helps resolve the findings after endorectal sonography has been unsuccessful because the tumors are stenotic or in a high or low position.

Keywords: cancer • colon • gastrointestinal radiology • oncologic imaging • rectum • sonography

Introduction

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Endorectal sonography is preferred to CT and conventional MRI in the preoperative local staging of rectal tumors [1-5]. The capability of sonography to resolve the layers of the rectal wall facilitates assessment of depth of invasion and thereby of precise tumor stage [6, 7]. Accurate tumor staging affects patient care because adjuvant therapy has an important role in the management of stage T3 and T4 disease, whereas local excision is preferred for T1 tumors [8-10]. Studies comparing CT with endorectal sonography have shown superior results with endorectal sonography for the assessment of both depth of invasion and lymph node involvement [2, 3]. The accuracy of endoluminal sonography is 69-97%, whereas that of CT is 41-82% [1-5, 11-15]. An important role of CT, however, is assessment of distant metastasis and contiguous organ involvement in advanced cancers [5, 16]. Therefore in many centers the combination of endorectal sonography and abdominal and pelvic CT is an accepted pretreatment strategy in the care of patients with rectal cancer.

Conventional MRI has proven to be inferior to endorectal sonography in the definition of the layers of the rectal wall. The accuracy rate is similar to that of CT [17-19]. However, the superior spatial resolution and anatomic detail afforded by endorectal surface coils have allowed equivalent efficacy, ranging from 70% to 90% in a number of small studies, to sonography in local staging of rectal tumors [20-22]. In the assessment of regional lymph nodes, endorectal MRI has not proven to be superior to endorectal sonography [23, 24]. Comparisons of endorectal sonography with double-contrast MRI have shown similar accuracy rates [25-27].

View larger version (175K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A —Advantages of sodium phosphate (Fleet Phospho-Soda, CB Fleet) enema. Transverse transvaginal sonographic (TVS) image of normal rectum in 62-year-old woman. Fluid (F) in rectal lumen appears black. Rectum is evident in its entirety as multilayered ring. All five layers of rectal wall are well delineated.

View larger version (197K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B —Advantages of sodium phosphate (Fleet Phospho-Soda, CB Fleet) enema. Transverse TVS image of rectum in 67-year-old woman shows large polypoid rectal mass (M) outlined by enema solution (arrows).

Transvaginal sonography (TVS) performed with a high-frequency end-fired probe placed in the vagina provides excellent-resolution images of not only the uterus and ovaries but also of the portions of the urinary and gastrointestinal tracts close to the vaginal vault. TVS has been used with variable success in the assessment of nongynecologic pathologic conditions within reach of a vaginal probe [30, 31]. The fixed position of the rectum deep in the pelvis directly posterior to the vagina is a prime choice for study by the transvaginal approach. Our objective was to assess the role of TVS in the staging of rectal cancer in women, especially in instances in which examination was difficult or considered a failure with traditional endorectal sonography.

Materials and Methods

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Patient Population
A retrospective study was conducted with the records of 60 women (age range, 35-81 years) in two medical centers who underwent endoluminal sonography for staging of rectal tumors between January 2000 and December 2003. Forty-five of the 60 patients underwent endorectal sonography that was followed by TVS at the larger center. Fifteen patients underwent TVS alone at the other institution. Selection of patients for both studies or one study was related only to the center at which sonography was performed. Patients who underwent only endorectal sonography in the time frame of the study were not included in the study. We received ethics committee approval for chart review.

Final pathologic results on the 60 tumors included 49 rectal carcinomas, nine tubulovillous adenomas, and two cases of gastrointestinal stromal tumor (GIST). Tumor size ranged from 1.0 to 8.0 cm. Surgical pathologic confirmation was obtained for 30 of the 49 rectal carcinomas, all nine tubulovillous adenomas, and both cases of GIST. Nineteen cases of locally invasive rectal carcinoma were confirmed by biopsy before chemoradiation therapy. The final tumor stage for the 49 rectal carcinomas was based on comprehensive clinical, colonoscopic, radiologic, and pathologic correlation. Four of the 49 rectal carcinomas were stage T1; seven, T2; 35, T3; and three, T4. Surgical confirmation of locoregional metastatic lymphadenopathy was obtained in 10 cases.

Imaging Techniques
At the larger institution involved in this study, a physician experienced in endorectal sonography and TVS obtained all the scans. Both examinations were performed on the same day, and a single comprehensive report of tumor stage was generated. The technical feasibility and effectiveness of TVS in comparison with endorectal sonography were documented at the time of the procedure. At the secondary institution, 15 cases of rectal carcinoma were staged only with TVS by a physician initially trained at the larger institution.

All patients received a sodium phosphate (Fleet Phospho-Soda, CB Fleet) enema 1 hour before the examination (Figs. 1A and 1B). A digital rectal examination was performed immediately before TVS. TVS was performed with an HDI 5000 scanner (Philips Medical Systems) with conventional end-firing 9- to 5-MHz TVS probes (C9-5, Philips) with the patient in the supine position. Color Doppler assessment was performed for all the tumors imaged with TVS. Endorectal sonography was performed with rotating axial 10-MHz and side-firing biplane 7-MHz probes (type 8537, Bruel and Kjaer). The probe head used for endorectal sonography was covered with a condom filled with 50 mL of degassed water. A sonolucent plastic cone (type WA 0453, Bruel and Kjaer) was used if evaluation of the anal canal was included in the tumor staging. All endorectal sonographic examinations were performed before TVS.

Analysis
Blind interpretation—A neutral person who was neither an investigator nor a reviewer selected separate TVS and endorectal sonographic image files for the 45 patients who underwent both procedures and for the 15 patients who underwent only TVS. Image files were shown independently to two blinded reviewers, both of whom were investigators in the study but had not seen any of the images in at least 6 months. The TVS and the endorectal sonography images were incorporated into a file and randomized so that the TVS image for a given patient was not shown to the reviewers in association with its corresponding endorectal sonography scan. The reviewers assessed each image file as either adequate or inadequate to determine tumor presence, size, and depth of penetration and nodal status. Then they determined a sonographic stage using the TNM criteria (Table 1) [32]. In case of disagreement between reviewers for a single technique, a consensus stage was obtained at a separate meeting.

Technical comparison: endorectal sonography versus TVS—Images from endorectal sonography and TVS for each patient were studied side by side to determine the image quality of a technique as equivalent, superior, or inferior to that of the other.

Correlation of TVS staging with histopathologic findings—In the 30 cases in which surgical pathologic correlation was available, the consensus sonographic stage from the blind interpretation of TVS images was compared with the histopathologic stage to establish the accuracy of TVS for comparison with published results in the staging of rectal cancer by endorectal sonography and other techniques.

Results

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Blind Interpretation
Assessment in the blind interpretation for adequacy of examination showed that TVS was successful in all 60 cases and that endorectal sonography was successful in 37 of 45 cases in which that technique also was used. Assessment of adequacy on both examinations included visualization of wall layers as depicted in Figure 2. The blind interpretation showed good agreement between the two reviewers with regard to adequacy of examination and tumor staging with endorectal sonography and TVS. The kappa coefficient was 0.85, indicating significant interreviewer agreement (p < 0.001). In three cases in which the reviewers gave different results of staging with a single technique, a consensus stage was reached at a separate meeting after the blind interpretation.

View larger version (169K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2 —Schematic shows gut signature. Cross-sectional (left) and longitudinal (right) representations of histologic layers of gut wall that correspond to the five layers seen on a sonogram. Blue layers are hypoechoic, yellow and pink layers are hyperechoic.

Among the 45 patients who underwent endorectal sonography, there were eight failed examinations, in which imaging was not possible, and four suboptimal scans, in which the part of the tumor visible on the scan was staged. Endorectal sonography was technically suboptimal in assessment of stenotic tumors (n =3), large tumors (n = 2), tumors high at the rectosigmoid junction (n = 4), and tumors low involving the anal canal (n = 3). In the 37 cases in which images with both techniques were available, the blind interpretation of tumor stage showed good agreement between the techniques ( =0.78; p < 0.001) (Table 2). In five (11%) of the 45 cases, staging was discordant between endorectal sonography and TVS, but the tumor stage classifications differed by only one level.

Technical Comparison of Endorectal Sonography Versus TVS
For all pathologic conditions, endorectal sonography and TVS were judged of equivalent efficacy in determination of tumor size and depth of penetration and nodal status in 30 (67%) of 45 patients. TVS was judged by the reviewers to be adequate for tumor staging in all 45 patients. In three (6.6%) of the 45 cases, TVS scans were suboptimal. The lesions in these cases were small posterior tumors, and gas and fluid in the rectal lumen interfered with visualization. Nonetheless, all of these tumors were both measured and staged with TVS. Endorectal sonography was suboptimal in 12 (27%) of the cases. Eight of the 12 examinations were assessed as complete failures, in which the tumor was not visualized. In four of the 12 examinations, tumor assessment was incomplete because of an inability to determine the extent of the tumor, but the part of the tumor seen was staged. In all 12 cases, TVS was successful in depicting the lesion and its extent, and the stage was correctly predicted.

Correlation of TVS Staging with Histopathologic Findings
TVS stage of the 49 rectal carcinomas determined by blind interpretation consensus was compared with histopathologic stage in the cases of the 30 patients who underwent surgery (Table 3). TVS was accurate in staging 25 (83.3%) of 30 tumors (Figs. 2, 3A, and 3B). Two (6.7%) of the 30 tumors were understaged, one of these T3 instead of T4, a clinically inconsequential event. The other tumor was staged T2 instead of T3. In the latter case, surgical pathologic examination showed only focal invasion of the perirectal fat, and post-operative chemoradiation therapy was considered adequate management. Three (10%) of the 30 tumors were overstaged. Two were staged T2 instead of T1 and one T3 instead of T2. The case diagnosed T3 and found to be T2 at pathologic examination was considered for surgery because the lesion was fairly mobile at colonoscopy and because the sonographic finding of mild irregularity of the perirectal fat layer in focal areas suggested early T3 disease. The two tumors staged T2 instead of T1 with TVS were polypoid tumors successfully resected at colonoscopy.

View larger version (181K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A —65-year-old woman with T2 N0 rectal carcinoma. Both scans show submucosa is penetrated by tumor and tumor involvement of muscularis propria. Arrows mark border of submucosa at margin of tumor. Endorectal sonogram obtained with axial rotating probe shows eccentric mass (M) between 11:30- and 4-o'clock positions. Mass obliterates submucosa and bulges deep border of wall but does not show extension into perirectal fat.

View larger version (61K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B —65-year-old woman with T2 N0 rectal carcinoma. Both scans show submucosa is penetrated by tumor and tumor involvement of muscularis propria. Arrows mark border of submucosa at margin of tumor. Transvaginal sonogram shows mass (M) of similar size and location to that in A. Wall-layer definition is superior to and border of submucosa at margin of tumor (arrows) is better delineated than in A. Disruption of involved layers is evident.

Sensitivity and specificity for staging of rectal cancer with TVS were determined by comparison of sonographic stage with histopathologic results in the 30 cases in which rectal carcinoma was surgically removed. Comparison of tumor confined within the bowel wall (stages T1 and T2) and tumor that extended beyond the bowel wall (stages T3 and T4) yielded a sensitivity of 94.7% and a specificity of 90.9% (Table 4).

The 19 (39%) of 49 patients with biopsyproven rectal cancer who did not undergo surgery had either advanced T3 or T4 disease and underwent neoadjuvant chemoradiation therapy before consideration for surgery (Figs. 5A, 5B, and 5C). Because we did not have gross anatomic pathologic results for these patients, their data were not included in the calculation of sensitivity and specificity. In all 19 cases, sonographic local staging showed clear T3 disease on the basis of destruction of all wall layers by the tumor and extension into the perirectal fat. The finding of T4 disease in two of the 19 patients was based on CT and MRI findings.

View larger version (145K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5A —76-year-old woman with gross T3 rectal carcinoma seen on transvaginal sonography (TVS) after failed endorectal sonography. Long-axis (A) and transverse (B) TVS images show large hypoechoic stenosing tumor with complete loss of wall-layer definition. Lumen (L) is narrowed. Gross invasion of perirectal fat (arrows) is evident in B.

View larger version (156K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5B —76-year-old woman with gross T3 rectal carcinoma seen on transvaginal sonography (TVS) after failed endorectal sonography. Long-axis (A) and transverse (B) TVS images show large hypoechoic stenosing tumor with complete loss of wall-layer definition. Lumen (L) is narrowed. Gross invasion of perirectal fat (arrows) is evident in B.

View larger version (173K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 5C —76-year-old woman with gross T3 rectal carcinoma seen on transvaginal sonography (TVS) after failed endorectal sonography. Sagittal TVS image through mesorectum shows three lymph nodes (arrows) in perirectal fat. Patient underwent preoperative chemoradiation therapy.

View larger version (189K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6A —57-year-old woman with tubulovillous adenoma. Endorectal sonogram obtained with rotating axial probe shows eccentric mass (m) in anterior aspect between the 11-o'clock and 3-o'clock positions. Wall layering is not well defined at base of tumor, but tumor does not extend into perirectal fat. Polypoid intraluminal nature of mass is not evident because inflated rectal balloon compresses soft tumor into rectal wall. Arrowheads indicate submucosa.

View larger version (185K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6B —57-year-old woman with tubulovillous adenoma. Sagittal transvaginal sonogram shows polypoid intraluminal mass (m) outlined by enema fluid and clearly defined submucosa (arrowheads). Suggestion of wall disruption (arrow) is evident at base of stalk.

View larger version (118K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 6C —57-year-old woman with tubulovillous adenoma. Projection in B with addition of color Doppler shows disruption is related to vascular stalk of tumor rather than tumor invasion through rectal wall.

View larger version (167K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7A —46-year-old woman with asymptomatic gastrointestinal stromal tumor. Sagittal transvaginal sonogram shows large hypoechoic mass (M) related to anterior rectal wall and arising from outer hypoechoic layer, muscularis propria. Submucosa is intact. Arrows outline two echogenic layers that constitute submucosa of anterior and posterior rectal wall. Luminal surfaces are in apposition and appear as gray line between two echogenic layers.

View larger version (117K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 7B —46-year-old woman with asymptomatic gastrointestinal stromal tumor. Color Doppler image at same location as A confirms mass is solid and vascular.

View larger version (169K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8A —35-year-old woman with invasive rectal cancer and necrotic lymphadenopathy. Transverse transvaginal sonogram of rectovaginal septum shows two large nodes (arrows) with necrotic centers.

View larger version (164K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 8B —35-year-old woman with invasive rectal cancer and necrotic lymphadenopathy. Axial CT scan shows two large nodes (long arrows) depicted in A and diffuse rectal wall thickening (short arrows) not shown in A.

View larger version (174K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4A —70-year-old woman with T3 N0 rectal carcinoma confirmed at surgery. Axial endorectal sonogram shows penetration of all rectal wall layers with irregularity of deep border of mass (M) into perirectal fat (arrows).

View larger version (172K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4B —70-year-old woman with T3 N0 rectal carcinoma confirmed at surgery. Transverse transvaginal sonogram shows concordant information with convincing evidence of irregular extension of tumor (M) into perirectal fat (arrows).

Discussion

Top Abstract Introduction Materials and Methods Results Discussion References

 
Because of its proven efficacy in resolution of the layers of the rectal wall, sonography continues to be the best imaging technique for local staging of rectal tumors [1-11]. Our initial experience with TVS for staging of rectal cancer was with patients with rectal tumors who underwent inadequate endorectal sonography (n = 12). TVS frequently resolves the limitations posed by endorectal sonography in women with rectal cancer. In patients with stenotic tumors, the endorectal probe may not be advanced into the rectum beyond the tumor and therefore is limited in defining tumor extent. The TVS approach clearly defines the superior and inferior tumor extent and helps determine the depth of invasion (Figs. 9A and 9B). In the four patients with tumors high in the rectum close to the rectosigmoid junction, the tumors were visualized only on TVS. Endorectal sonography did not show the tumor because of the limitations of probe length and the fixed direction of insonation of a side-fired probe (Figs. 10A and 10B). Use of an end-fired transvaginal probe allowed a much more flexible and greater field of view. Anal canal involvement was easily assessed with TVS in all patients, and TVS caused less discomfort than did endorectal sonography (Figs. 11A, 11B, and 11C). Furthermore, TVS can be performed with conventional probes used for routine pelvic examinations.

View larger version (138K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9A —56-year-old woman with large stenotic rectal tumor. Endorectal sonographic examination failed. Transverse (A) and sagittal (B) transvaginal sonograms show extensive circumferential rectal wall tumor (T), destruction of wall layers, irregular residual lumen (arrows, A), and perirectal lymphadenopathy (arrows, B). Images show tumor only with no normal bowel wall. Lumen is obliterated and visible as central irregular white line related to residual luminal content, air, or both.

View larger version (180K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 9B —56-year-old woman with large stenotic rectal tumor. Endorectal sonographic examination failed. Transverse (A) and sagittal (B) transvaginal sonograms show extensive circumferential rectal wall tumor (T), destruction of wall layers, irregular residual lumen (arrows, A), and perirectal lymphadenopathy (arrows, B). Images show tumor only with no normal bowel wall. Lumen is obliterated and visible as central irregular white line related to residual luminal content, air, or both.

View larger version (171K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 10A —51-year-old woman with T2 cancer of rectosigmoid junction not seen on endorectal sonography. Transvaginal images show eccentric hypoechoic mass (m) in bowel. Destruction of echogenic wall layer represents submucosa with infiltration through hypoechoic muscularis propria. Perirectal fat is not invaded. Transverse image.

View larger version (181K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 10B —51-year-old woman with T2 cancer of rectosigmoid junction not seen on endorectal sonography. Transvaginal images show eccentric hypoechoic mass (m) in bowel. Destruction of echogenic wall layer represents submucosa with infiltration through hypoechoic muscularis propria. Perirectal fat is not invaded. Long-axis image shows rectal wall layers opposite tumor are intact.

View larger version (126K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11A —62-year-old woman with cancer of anal canal. Transverse (A) and long-axis (B) transvaginal sonograms show hypoechoic mass (M) in anal canal close to anal verge. C, Color Doppler image shows intense vascularity of mass.

View larger version (112K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11B —62-year-old woman with cancer of anal canal. Transverse (A) and long-axis (B) transvaginal sonograms show hypoechoic mass (M) in anal canal close to anal verge.

View larger version (110K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 11C —62-year-old woman with cancer of anal canal. Color Doppler image shows intense vascularity of mass.

Our findings are in agreement with published results of preliminary studies that have shown the feasibility of TVS in staging rectal cancer with high accuracy and technical competence [33, 34]. Scialpi et al. [35] described the use of a water enema with TVS for local staging of advanced stenotic rectal tumors. Fedyaev et al. [36] used TVS with a waterfilled balloon in the rectal lumen for staging rectal cancer in women. In our experience, Fleet enema was sufficient for both bowel preparation and provision of the necessary amount of fluid to distend the rectum. The luminal fluid served to enhance wall-layer definition and to outline the intraluminal component of a polypoid mass (Figs. 1A and 1B). TVS was valuable for study of all lesions regardless of size and stage. TVS was uniformly better at delineating lymph nodes in the mesorectum because of the more compliant nature of the vagina compared with the rectum and the enhanced field of view for depth obtained with an end-fired probe.

TVS used alone has a limitation related to lack of a panoramic axial view of the rectum such as that afforded by the rotating axial probe used with endorectal sonography. Survey of the entire rectum therefore takes much longer with TVS than with endorectal sonography. On endorectal sonography, the axial scan performed with a rotating mechanical transducer crystal is excellent for survey of the entire rectum and perirectal soft tissues. This capability is most often beneficial when the tumor is not felt with digital rectal examination before the procedure. Once it is localized with an axial probe, the tumor can be studied in more detail with a biplane probe, which provides better resolution than a mechanical rotating crystal.

The limitations of this study include its retrospective nature and the fact that the same investigator performed both TVS and endorectal sonography at a single visit. Nonetheless, the examinations were performed with separate sonographic machines, making it possible to separate image files for each technique on our PACS and facilitating retrieval and selection for blind interpretation. Endorectal sonography was always performed before TVS, which may have introduced a bias. However, the initial interpretation was not used for the comparison of staging with histopathology. Furthermore, the person performing the initial interpretation of the scans also participated in the blind interpretation. We believe that this is not problematic because staging a tumor on the basis of a sonogram is not highly subjective and reflects a simple interpretation as to the degree of invasion of the rectal wall. In addition, the number of patients was comparatively small, and our association with a large oncology facility may have presented us with an unusually large percentage of tumors at an advanced stage.

Perhaps the most important limitation of this study relates to the lack of confirmatory surgical histopathologic results for the 19 patients with rectal cancer who had advanced invasive T3 tumors on TVS, endorectal sonography, or both and underwent chemoradiation therapy with biopsy before surgery was considered. Before the start of this retrospective review, the standard of practice at our institution had been to confirm clinically suspect T3 disease by endorectal sonography and biopsy before administration of neoadjuvant therapy. The treatment of the 19 patients with gross T3 disease therefore complied with our institutional practices. Surgical pathologic results are rarely available for this patient population. Our results showed excellent agreement of endorectal sonographic and TVS findings in all stages of rectal cancer (Table 2). Furthermore, in the 17 patients with stage T3 disease for whom there was pathologic correlation, TVS stage and pathologic stage were in complete agreement (Table 3). We therefore believe that inclusion of this group of patients is reasonable. All patients with T3 disease who received radiation therapy underwent clinical evaluation by an experienced colorectal and oncology specialist. Having for many years performed digital rectal examinations on all patients undergoing endorectal sonography for staging of rectal tumors, we believe large, hard, fixed invasive tumors are much different from other tumors at digital examination. In fact, the requisitions that we receive on this group of patients usually request confirmation of T3 disease whereas other requisitions request staging of rectal tumors.

Another limitation of our study was that the investigators performed the blind interpretation of image files organized by a neutral third person. This procedure was necessary because we lacked staff trained in and capable of interpreting images obtained with endorectal sonography and TVS. We believe our method was reasonable because a minimum of 6 months, and in most instances more than 6 months, had passed between sonographic examination and blind interpretation. In addition, the reviewers were not providing a diagnosis; they were staging the tumors and assessing the adequacy of examinations.

We learned a great deal about tubulovillous adenoma since the beginning of the retrospective review. A TVS approach allowed us for the first time to see the soft, pliable nature of these tumors, which are often very large. Real-time evaluation with compression of the tumors with the vaginal probe allowed us to better visualize the intraluminal portion of the tumors and their hypervascular stalks and showed continuous submucosa at the level of the tumor stalk. Use of TVS allowed us to avoid our previous tendency toward overstaging these superficial tumors as T1 rather than T0 because of compression of the soft tumor into the adjacent rectal wall with the axial endorectal ultrasound probe covered by an inflated balloon (Figs. 5A, 5B, and 5C). Although using both TVS and endorectal sonography we overstaged some tubulovillous adenomas in this study, we overstaged three of five tumors with endorectal sonography but correctly staged them with TVS (Table 2) as confirmed at pathologic examination of the excised lesion. Differentiation of T0 and T1 disease remains a difficult task with any sonographic examination.

No questionnaire either oral or written was given to our patients regarding their preference of procedure. Nonetheless, at our institution and others, TVS is routinely used for gynecologic examinations and is not considered invasive, painful, or otherwise troublesome. In all of the cases of rectal cancer in our study, there were no technical problems or instances of patient dissatisfaction with TVS. Endorectal sonography, however, is often associated with considerable patient anxiety and, in some patients, rectal and anal discomfort. We have found that rectal discomfort is much more frequently encountered in patients with large rectal tumors than in patients undergoing endorectal sonography for other indications, such as prostate evaluation.

In conclusion, our study showed successful TVS evaluation of all rectal tumors in which it was attempted, including stenotic tumors and those involving both the anal canal and the rectosigmoid region. These sites are well recognized as potential problem areas for endorectal sonography. We consider TVS an excellent adjunct to endorectal sonography for staging rectal cancer, and we believe that particular benefit is appreciated in difficult cases.

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