contrast - enhanced computed tomography colonography ( ce - ctc ) is the best technique for colorectal cancer sites and staging ( 12 ) , as well as to diagnose synchronous colonic lesions ( 3 ) in patients with obstructing cancers .
ce - ctc is also useful to preoperatively evaluate others colorectal diseases , such as diverticular disease and inflammatory bowel disease ( 45 ) .
the laparoscopic approach for colonic surgery has become common and widely used because of the multiple advantages compared to conventional laparotomy .
laparoscopic surgery produces smaller surgical incisions , less intraoperative blood loss , faster recovery of normal bowel function , and shorter hospitalization ( 67 ) .
nevertheless , the disadvantages to this approach include lack of a panoramic view of the operative field and tactile sensation , leading to potential inaccurate localization of a colonic lesion and difficulties with vessel ligation and lymph node dissection ( 8) .
only a few studies have analysed the vascular anatomy of the colon using multidetector ct ( 91011 ) and only one used ct colonography ( 12 ) .
bowel preparation consisted of a low - fiber diet and a mild laxative ( macrogol solution ) the day before ct .
faeces were tagged by administering 60 - 90 ml amidotrizoate meglumine and 500 ml water at least 3 hours before the examination .
the colon was distended by insufflating at least 3 l of carbon dioxide using an automatic insufflator .
we performed a pre - contrast scan with the patient in the prone position using low mas and different post - contrast scans in the supine position after injecting 500 - 600 mgi / kg / body weight .
post - contrast scans may have included arterial ( obtained using bolus - tracking monitoring technique ) , portal venous , and delayed phases depending on the disease .
comprehending the complex three - dimensional ( 3d ) anatomy of the colon and branching vessels is difficult on axial images , particularly for inexperienced readers .
3d imaging provides surgeons with a precise and immediate understanding of the patient 's anatomy , including colonic loop shapes , colonic lesion sites , and the courses and relationships of the branching vessels .
we obtained 3d fused images using a dedicated workstation ( advantage workstation 4 , general electric healthcare , waukesha , wi , usa ) by processing the ct dataset from the arterial and portal - venous phases .
three reformations with different settings ( 3d colon map and two different 3d vascular presets ) were prepared separately and fused together into a single volume , which included the 3d colon map , a 3d arteriogram , and a 3d venogram , with the mesenteric arteries colored in red and relevant venous branches colored in blue .
this resulted in a colon map that overlapped with the vascular map and showed the mesenteric branching pattern and the relationships between the colonic lesions , arteries and veins .
the 3d images could be tilted and rotated to obtain the view that best simulates the intraoperative field of view .
ct colonography allows for an accurate pre - operative assessment of colonic anatomy , and the locations of the colonic lesions and lymph nodes .
post - contrast acquisition and the vascular map allow for a precise evaluation of mesenteric artery branching patterns and the relationships between arterial and venous vessels .
although the laparoscopic approach has many obvious benefits compared to laparotomy , it suffers from a restricted operative field of view and an inability to manipulate tissues , which can result in time - consuming dissections when searching for anatomical landmarks , lymph nodes , or vessels .
intraoperative conversion rates to laparotomy from laparoscopic colectomy are 10 - 20% ( 713 ) and is often due to difficulties identifying mesenteric vessels , synchronous tumors , intraoperative bleeding or procedure length ( 7 ) .
complications , such as bleeding and bowel ischemia , can occur because of vascular injury while dissecting nodes or ligating a vessel .
previous knowledge of the patient 's mesenteric vascular anatomy , including arterial branching variants and relationships with adjacent veins , reduces operative time and the incidence of intraoperative complications ( 11 ) .
the branching pattern of the superior mesenteric artery ( sma ) must be assessed before a right hemicolectomy and right transverse colon surgery .
the middle colic artery ( mca ) and the ileocolic artery ( ica ) are present in almost all patients , whereas the right colic artery ( rca ) is present in about 50% of cases ( figs . 1 , 2 ) .
the inconsistency in the presence of the accessory left colic artery ( alca ) , known as the artery of riolan , originates from the sma or mca and anastomoses with the left colic artery ( lca ) , feeding the transverse colon ( figs . 3 , 4 ) . the common origin of the mca , rca , and ica ( fig .
the most significant variant to be considered during laparoscopic right hemicolectomy is the relationship between the colic arteries and the superior mesenteric vein ( smv ) ; arteries cross anterior to the smv in most patients , but a posterior crossing pattern of the ica , mca , or rca is also common ( figs . 5 , 6 ) .
it is important to locate the alca and the branching pattern of the inferior mesenteric artery ( i m a ) when planning left transverse colon surgery and left hemicolectomy .
moreover , pre - operative planning for sigmoidectomy should include an evaluation of the sigmoid artery ( sa ) branching pattern because the i m a can be preserved if the sas are selectively ligated .
the number of sas varies and they can either originate from the i m a or lca ( figs . 2 , 4 , 7 ) ( 15 ) .
the relationship between arteries and the inferior mesenteric vein ( imv ) can also vary : lca and sas can either cross anteriorly or posteriorly to the imv ( figs . 8 , 9 ) .
because of their close proximity , the relationships between the lca , sas , and the left gonadic vein and ureter must be assessed .
the origins of other splanchnic arteries from the sma or i m a must also be considered be .
7 ) ( 15 ) . variants in mesenteric vein drainage should also be evaluated ( fig . 8) .
vascular maps from a ce - ctc examination are easily obtained by modifying the standard protocol and are easy to interpret .
the laparoscopic surgeon , regardless of the disease , can benefit from vascular maps , as they limit risks concerning vessel ligation and/or lymph node dissection .
 contrast - enhanced computed tomography colonography ( ce - ctc ) is a useful guide for the laparoscopic surgeon to avoid incorrectly removing the colonic segment and the failure to diagnose of synchronous colonic and extra - colonic lesions . 
 lymph node dissection and vessel ligation under a laparoscopic approach can be time - consuming and can damage vessels and organs . 
 moreover , mesenteric vessels have extreme variations in terms of their courses and numbers . 
 we describe the benefit of using an abdominal vascular map created by ce - ctc in laparoscopic colorectal surgery candidates . 
 we describe patients with different diseases ( colorectal cancer , diverticular disease , and inflammatory bowel disease ) who underwent ce - ctc just prior to laparoscopic surgery . 
INTRODUCTION
Contrast-Enhanced CT Colonography Protocol
Vascular Mapping
Benefits for the Laparoscopic Surgeon
Main Vascular Variants Related to Colonic Laparoscopic Surgery
SUMMARY