Answer for BIR CoW 18 Jul 2021
Reversed intestinal rotation with midgut volvulus
Findings:
The CT scan demonstrated a markedly altered anatomy of the midgut and hindgut. The duodenum crossed from right to left ventral to the superior mesenteric artery (image 1), suggesting an intraperitoneal position in all of its portions, with the duodenojejunal flexure situated slightly to the left of the midline. The proximal jejunum then crossed back to the right abdomen, posterior to the SMA, suggesting a retroperitoneal position (image 5). Further distally the distal jejunum/proximal ileum crossed back to the left lower abdomen, remaining in an intraperitoneal position ventral to the mesenteric root. Most of the ileal loops were situated in the left upper abdomen (video); the cecum was found in the subhepatic region in close proximity to the ligament of Treitz (video), thus suggesting a narrow mesenteric pedicle. The transverse colon dorsally crossed the pedicle of the SMA and the superior mesenteric vein (SMV) in a retro-arterial position (Image 5), defining this anatomic midgut variation as reversed rotation, and extended to the left abdomen to continue as a normal left colic flexure and descending colon. Doppler and CT noted an inverted relationship of the SMV to the SMA with the vein lying to the left and anterior of the artery(image 2). There is a whirl – like appearance around the superior mesentric vascular pedicle(image 3)
Discussion:
Intestinal malrotation is a rare congenital disorder, defined by an abnormal position of the bowel within the peritoneal cavity, which results from a failure in the normal course of midgut rotation and fixation during embryologic development. Depending on which stage of the physiological sequence of midgut development is stopped or disrupted, a variety of anatomic anomalies can occur, comprising non-rotation, incomplete rotation, mixed-rotation, and reversed rotation. Reversed rotation, by far the rarest presentation of intestinal rotation and fixation anomalies, accounts for 2–4% of all malrotation cases. Normal gut development : In the normal sequence of intestinal development, the midgut, which extends from the entrance of the bile duct into the duodenum to the last third of the transverse colon, rotates 270 degrees counterclockwise around the axis of the SMA. This rotation occurs during the fourth through to the 12th week of gestation . Due to the rapid growth of the midgut, it initially extends into the extra-abdominal cavity and forms the umbilical loop, which is positioned sagittally. This process is known as physiological herniation of the midgut. Further growth of this umbilical loop is associated with a rotation of 90 degrees around the axis of the SMA in a counterclockwise direction, resulting in a horizontal position of the umbilical loop. The small intestine comes to lie to the right and the cecum to the left of the SMA. Between 8.5 and 9.0 weeks of development, the physiological umbilical hernia resolves as the abdominal cavity becomes sufficiently large. The loops of the small intestine return first from the umbilical stalk into the abdomen, while the cecum returns last, undergoing an additional 180 degrees counterclockwise rotation . As a result of this, the duodenum acquires a position posterior to the SMA, the duodenojejunal junction a left-sided and the cecum a right-sided position . The broad mesenteric base runs obliquely from the inferior part of the duodenum to the ileocecal valve preventing the small bowel from twisting around the SMA. Reversed intestinal rotation: Reversed intestinal rotation was first reported in 1883 by Tscherning. In 1923, Dott suggested that reversed rotation occurs when the initial 90 degrees counterclockwise rotation of the umbilical loop is followed by an 180 degrees clockwise rotation, resulting in a net 90 degrees clockwise rotation. Estrada further classified reversed intestinal rotation into two subtypes: retro-arterial and pre-arterial. In the more common retro-arterial subtype the migration into the peritoneal cavity begins with the cecum, passing to the right and posterior to the SMA. As a consequence, the transverse colon lies behind the duodenum and is separated from it by the SMA. The duodenum remains intraperitoneal, anterior to the SMA. In the less common pre-arterial subtype, the pre-arterial segment is thought to return first into the peritoneal cavity, lying anterior to the SMA in the left abdomen. The post-arterial segment then ends up in the right abdomen.
Findings:
The CT scan demonstrated a markedly altered anatomy of the midgut and hindgut. The duodenum crossed from right to left ventral to the superior mesenteric artery (image 1), suggesting an intraperitoneal position in all of its portions, with the duodenojejunal flexure situated slightly to the left of the midline. The proximal jejunum then crossed back to the right abdomen, posterior to the SMA, suggesting a retroperitoneal position (image 5). Further distally the distal jejunum/proximal ileum crossed back to the left lower abdomen, remaining in an intraperitoneal position ventral to the mesenteric root. Most of the ileal loops were situated in the left upper abdomen (video); the cecum was found in the subhepatic region in close proximity to the ligament of Treitz (video), thus suggesting a narrow mesenteric pedicle. The transverse colon dorsally crossed the pedicle of the SMA and the superior mesenteric vein (SMV) in a retro-arterial position (Image 5), defining this anatomic midgut variation as reversed rotation, and extended to the left abdomen to continue as a normal left colic flexure and descending colon. Doppler and CT noted an inverted relationship of the SMV to the SMA with the vein lying to the left and anterior of the artery(image 2). There is a whirl – like appearance around the superior mesentric vascular pedicle(image 3)
Discussion:
Intestinal malrotation is a rare congenital disorder, defined by an abnormal position of the bowel within the peritoneal cavity, which results from a failure in the normal course of midgut rotation and fixation during embryologic development. Depending on which stage of the physiological sequence of midgut development is stopped or disrupted, a variety of anatomic anomalies can occur, comprising non-rotation, incomplete rotation, mixed-rotation, and reversed rotation. Reversed rotation, by far the rarest presentation of intestinal rotation and fixation anomalies, accounts for 2–4% of all malrotation cases. Normal gut development : In the normal sequence of intestinal development, the midgut, which extends from the entrance of the bile duct into the duodenum to the last third of the transverse colon, rotates 270 degrees counterclockwise around the axis of the SMA. This rotation occurs during the fourth through to the 12th week of gestation . Due to the rapid growth of the midgut, it initially extends into the extra-abdominal cavity and forms the umbilical loop, which is positioned sagittally. This process is known as physiological herniation of the midgut. Further growth of this umbilical loop is associated with a rotation of 90 degrees around the axis of the SMA in a counterclockwise direction, resulting in a horizontal position of the umbilical loop. The small intestine comes to lie to the right and the cecum to the left of the SMA. Between 8.5 and 9.0 weeks of development, the physiological umbilical hernia resolves as the abdominal cavity becomes sufficiently large. The loops of the small intestine return first from the umbilical stalk into the abdomen, while the cecum returns last, undergoing an additional 180 degrees counterclockwise rotation . As a result of this, the duodenum acquires a position posterior to the SMA, the duodenojejunal junction a left-sided and the cecum a right-sided position . The broad mesenteric base runs obliquely from the inferior part of the duodenum to the ileocecal valve preventing the small bowel from twisting around the SMA. Reversed intestinal rotation: Reversed intestinal rotation was first reported in 1883 by Tscherning. In 1923, Dott suggested that reversed rotation occurs when the initial 90 degrees counterclockwise rotation of the umbilical loop is followed by an 180 degrees clockwise rotation, resulting in a net 90 degrees clockwise rotation. Estrada further classified reversed intestinal rotation into two subtypes: retro-arterial and pre-arterial. In the more common retro-arterial subtype the migration into the peritoneal cavity begins with the cecum, passing to the right and posterior to the SMA. As a consequence, the transverse colon lies behind the duodenum and is separated from it by the SMA. The duodenum remains intraperitoneal, anterior to the SMA. In the less common pre-arterial subtype, the pre-arterial segment is thought to return first into the peritoneal cavity, lying anterior to the SMA in the left abdomen. The post-arterial segment then ends up in the right abdomen.
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!