Answer to Twist and Shout
Correct answer is E, the sigmoid colon. For a volvulus to occur, the bowel must be tethered to the posterior abdominal wall via a mesentery. Hence, the potential sites for the colon include the caecum, transverse, and sigmoid colon. The question specifically requires you to select the part of the colon sandwiched by two parts of the digestive tract that are located in the retroperitoneal space, i.e., lacking a mesentery. Above the sigmoid colon is the descending colon, below it is the rectum, both are retroperitoneal structures. Also, it just so happens to be, that the most common sites of volvulus are the sigmoid colon and cecum, but the sigmoid colon is a far more frequent site for the volvulus to occur.
Answer to this question is based on material presented in lectures 7 of the Abdomen Lecture Series.
= Caecum
= Ascending colon
= Ascending colon
= Descending colon
= Sigmoid colon