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International Journal of Anatomical Variations

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Dolichosigmoid with Additional Sigmoidal Branches and Displaced Descending Colon

Author(s): Naveen Babu Kandavalli, Leon Wu, Francis Danquah, Bedia Castellanos

Sigmoid colon is a part of large intestine and normally measures 15” in length that extends from the pelvic brim to the third piece of the sacrum where it becomes the rectum. Dolichosigmoid or redundant sigmoid colon is a term used for sigmoid colon longer than its normal size. The present case had a displaced descending colon and a redundant part of sigmoid colon. During a routine dissection class for medical students, an anatomical variation related to sigmoid colon in an 87-year-old male cadaver was found. The colon was carefully dissected and studied in detail the position, attachment of sigmoid mesocolon, examination of viscera in close proximity and the blood supply to each part of the large intestine. A meticulous review of the literature was conducted as well. An anomalous displacement of descending and sigmoid colons was found. The descending colon is normal in length, retroperitoneal and lying close to the midline leaving out a space to its left that was occupied by loops of jejunum and ileum. The sigmoid colon is composed of redundant ascending and normal descending parts. The redundant part of the sigmoid colon is centrally placed as a loop ascending into the peritoneal cavity reaching the splenic flexure at the level of T11 approximately. The descending part of the sigmoid colon crosses the midline at L1 and runs close to the right midclavicular line continuing as rectum. The total length of sigmoid colon measures 23.2”. The blood supply to the redundant part of the sigmoid comes from a common trunk arising from inferior mesenteric that splits into left colic and two additional sigmoid branches. The blood supply to the descending part of sigmoid is supplied by sigmoidal artery coming directly from inferior mesenteric artery. The branching pattern of sigmoidal arteries compared to previous cases in the literature makes this case very unique. Embryology of gut development is complex and often unpredictable, leading to variations in length and position. The growth and rotation of midgut is divided into four stages. An excess of growth of the caudal segment of gut tube in stage 3 can cause redundant sigmoid. This variation could increase the chances of sigmoid volvulus, constipation and may pose risk as the loops may coil around and form a knot leading to obstruction. A redundant loop of sigmoid colon may be asymptomatic or it might lead to urinary, digestive and vascular complications. The descending colon is normal in length but lies close to the midline which may compress the aorta when loaded with feces. Radiologists and surgeons must be well aware of these variations to establish a correct diagnosis and assert the appropriate management when performing colonoscopy, sigmoidoscopy and abdominopelvic procedures.