The patients suffering from stenosing colorectal cancer are frequently treated for occlusion (20%) and stenosis (16%) 1. The elective surgical treatment concerning the stenosis is to be performed after the preoperative assessment of the colonic segments upstream the cancer.

If the endoscopic instrument can pass over the lesion, the gold standard is the colonoscopy. On the other hand, when the instrument cannot surmount the stenosis, the proximal segment of colon is to be evaluated through a double contrast barium enema. This approach shows low sensitivity and specificity particularly in the right colon 2.

Threfore when barium enema does not lead to an accurate evaluation, the patient needs an intra-operatory colonoscopy 3. This investigation implies a few difficulties as the patient needs to be positioned on the operating table. It also requires additional time and can make the abdominal closure more difficult, because of the bowel distension caused by the insufflated air 45.

When the endoscopic procedure is incomplete because of the presence of a severe stenosing lesion, a further colonoscopy is required at 3-month follow up 67, in order to rule out a missed synchronous lesions.

The recent introduction of CTC allows a more adequate preoperative assessment of colon showing higher sensitivity and specificity 8. The aim of this study is to illustrate our experience with the CTC for the pre-operative assessment of the entire colon in the patients with stenosing colorectal cancer.

From January 2005 till March 2009, we observed and treated 43 patients with stenosing colorectal neoplastic lesions presenting with changes in the bowel habit, constipation, abdominal pain and lower gastrointestinal bleeding. We observed 28 males and 15 females aged between 47 and 73 years (average age 65 years). All patients did not tolerate the endoscopic procedure. For this reason they underwent a CTC in order to have a complete pre-operative assessment of the entire colon. All 43 patients underwent a pre-operative CTC in order to have a complete assessment of the entire colon. All 43 patients underwent surgical resections and specimen was carefully evaluated to search for any synchronous lesions. Furthermore all patients underwent a follow-up colonoscopy at 3 months from surgery.

The results from CTC were compared with both macroscopic examination of specimen and the follow-up colonscopy.

The CTC showed synchronous lesions in 4 patients (9.3% of the cases) (Table 1):

• a pedunculated polyp in two cases (8 and 12 mm of diameter) both in the left colon;

• a sessile polyp (18 mm of diameter) in ascending colon;

• a voluminous vegetating lesion (36 mm of diameter) in the ascending colon.

The patients with synchronous colonic lesions are usually treated through a laparotomic access, as identifying laparoscopically synchronous lesions without a tattoo marked preoperatively is difficult.

Furthermore, often it is not possible to identify synchronous lesions by intra-operative palpation even if the diameter is larger than one centimetre 910. This supports the need of good preoperative assessment.

In our series the patients with synchronous neoplastic lesions underwent the following surgical treatments (Table 1):

• Left laparoscopic hemicolectomy (stenosing sigmoid cancer with adjacent peduncalated polyp of descending colon)

• Laparoscopic anterior resection of rectum (stenosing rectal cancer with adjacent peduncalated polyp of sigmoid colon).

• Left laparotomic hemicolectomy associated with excision of polyp through enterotomy in the ascending colon (stenosing cancer of sigmoid colon associated a sessile polyp of ascending colon).

• Subtotal laparotomic colectomy for two synchronous neoplastic lesions located in distant colic segments (descending colon stenosing cancer associated with vegetant neoplastic lesion of ascending colon).

Computed Tomographic Colonography (CTC) is also known as "virtual colonoscopy" and it was introduced in 1994. It is considered a noninvasive method of imaging and it allows to explore the colon by employing a helical CT 11.

Data from literature show that CTC is safer than colonoscopy. Indeed a colonic perforation occurs in 1:1000 patients undergoing conventional colonoscopy and mortality associated with this procedure is 1:5000 121314151617, while the morbidity and mortality associated with CTC are similar to those of the air-contrast barium enema (perforation rate of 1:10000 and mortality rate of 1:50000) 181920.

There is only one study in literature showing a perforation rate, which is very low, up to 0.04% (3/7180) 21 and no study showing a case of death after performing a CTC.

The CTC has recently been proposed as the standard investigation for the pre-operative assessment of the colonic segments proximal to the obstructive cancer, being well tolerated, less invasive and showing good results 422232425.

Usually the colonoscopy is not fully carried out up to the ileocecal valve in 5-10% of the patients; this is mainly due to 26:

• presence of stenosing neoplastic lesion of rectum or distal colon (58,3%):

• presence of dolicocolon (33%);

• presence of spastic colon (11,7%).

• presence of extrinsic compressions (1,6%);

• presence of intestinal malrotation (1,6%);

• presence of visceral adhesions.

In the past in all these cases the alternative investigation was an opaque enema. Nowadays, CTC shows a higher sensitivity making it the choice investigation when the traditional endoscopy cannot be carried out satisfactorily 26.

All CTCs performed in the above mentioned cases were successful (91,7-100%) (table 4) 4222327.

This study shows CTC as a valid pre-operative investigation (sensitivity 83.7%) in order to detect synchronous neoplastic lesions in the patients who do not tolerate the conventional colonoscopy because of stenosing colorectal cancer. The main benefits from from its employment are that the intraoperative colonoscopy is not needed and more synchronous lesions are detected and treated at the time of the elective surgery for the stenosing cancer avoiding further surgery later on.

The Authors state that none of the authors involved in the manuscript preparation has any conflicts of interest towards the manuscript itself, neither financial nor moral conflicts. Besides none of the authors received support in the form of grants, equipment, and/or pharmaceutical items.

All authors contributed equally to this work.

Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.