USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 37-year-old man with a history of irritable bowel syndrome presents to the emergency department with acute intermittent abdominal cramping, vomiting, and constipation that started the night before, 2 hours after dinner. The patient stated he has never felt this pain before, and rated it as a 9 on a 10 point scale. Physical exam revealed a tympanic and asymmetrically distended abdomen in the right lower quadrant. The patient was rushed to the operating room for an emergency procedure. As the surgeon operates, he most likely resects structures supplied by which of the following arteries?
The term volvulus actually comes from the Latin word volvere, which means “to roll”.
So a volvulus is an obstruction caused by a loop of the intestine that rolls or twists around itself and its surrounding mesentery, which is the tissue that attaches the intestine to the back wall of the abdomen.
The three most common types of volvulus are a sigmoid volvulus, which happens in the the last part of the large intestine, leading to the rectum; a cecal volvulus, which happens in the beginning of the large intestine, and a midgut volvulus, which happens in the small intestine.
Now, a sigmoid volvulus is the most common type of volvulus, and it can happen in a variety of settings.
One classic one being pregnancy, because the growing fetus can cause displacement and twisting of the colon.
It can also develop, though, in middle-aged and elderly individuals.
This can sometimes happen as a result of chronic constipation, where a big load of stool can act like a pivot point around which the rest of the colon can twist.
In addition, there are also abdominal adhesions, where internal scar tissue creates a physical attachment between two parts of the abdomen, which again serves as a pivot point around which the colon can twist.
A cecal volvulus is usually found in young adults, and usually happens in individuals who didn’t develop their abdominal mesentery normally during fetal development.
Since some mesentery contacts may be missing in these individuals, the colon can flop around freely and any large object—like a baby in pregnancy or a load of stool in someone constipated—can act as a pivot point in the cecum and cause the colon to twist.
Midgut volvulus is most commonly found in babies and small children and is the result of abnormal intestinal development in fetuses.
In normal fetal development, the digestive tract starts as a straight tube from the stomach to the rectum.
Once the fetus reaches around 10 weeks, though, the intestine pulls back out of the umbilical cord, and returns to the abdominal cavity and makes two turns, so that it is no longer a straight tube.
Babies with malrotation can later develop twisting of the small intestine, which is a midgut volvulus.