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CHAPTER 65

Intestinal Malrotation and

Midgut Volvulus

Johanna R. Askegard-Giesmann
Christopher C. Amah
Brian D. Kenney

Introduction Anomalies of Migration
Malrotation is a spectrum of anatomic abnormalities of incomplete Omphalocele
rotation and fixation of the intestinal tract during foetal development. Return of the midgut from the yolk sac back into the abdominal cavity
Disorders of intestinal rotation and fixation are of paramount impor- is usually completed by week 12 of intrauterine life. This enables the
tance to the paediatric surgeon because they are most commonly seen anterior abdominal wall mesodermal folds to meet at the central umbili-
in infancy and childhood and can have catastrophic consequences when cal ring, thereby closing the anterior abdominal wall. When the return
midgut volvulus occurs. Early diagnosis and surgical treatment of this of the midgut is delayed or arrested, the anterior abdominal wall folds
disorder can be life saving. fail to meet, and an omphalocele in the central umbilical area of the
Demographics abdomen is the result.
1,2
Malrotation is thought to occur in approximately 1 in 500 live births. Congenital diaphragmatic hernia
The exact incidence is not known because many patients may live their If return of the midgut into the abdominal cavity, which divides the
entire lives without experiencing problems or consequences from their celomic cavity into peritoneal and pleural compartments, occurs before
malrotation. Approximately 80% of patients with malrotation will pres- the closure of the pleuroperitoneal membrane at 8 weeks gestation, part
ent within the first month of life, and of those, most will present within of the returning midgut loop may herniate into the pleural cavity. This
the first week of life. 1–4 occurs usually in the posterolateral position on the left side.
Embryology/Pathophysiology Subhepatic appendix
Embryology With completion of the 270° rotation of the ileocecal limb of the midgut
The adult midgut extends from the second portion of the duodenum loop, the caecum is brought to the right upper quadrant of the abdomen.
to the proximal third of the transverse colon, and is derived from the The caecum with the attached appendix then further descends down to
embryologic midgut loop. The normal development of the human the right lower quadrant position in the right iliac fossa and becomes
intestine involves two processes: rotation of the midgut and the sub- fixed to the posterior abdominal wall. The caecum and appendix may
sequent fixation of the colon and mesentery. These processes occur in fail to migrate and remain in that subhepatic position. This condition
three stages. may cause a serious diagnostic dilemma in acute appendicitis.
Stage 1 consists of umbilical cord herniation, lasting from Anomalies of Rotation
approximately weeks 5 to 10 of embryonic development. The midgut Nonrotation
lengthens disproportionately during this period and undergoes rotation Nonrotation may occur when the midgut returns to the abdominal cav-
around the superior mesenteric artery (SMA) axis for a total of 270° ity en masse without rotating. Then, the first and second parts of the
in the counterclockwise direction. Stage 2 is the return of the midgut duodenum are situated normally but the third and fourth parts descend
loop back into the abdomen; it occurs at approximately weeks 10 to 11. vertically downward along the right side of the superior mesenteric
As the intestines re-enter the abdominal cavity, the cephalad midgut artery. The small bowel lies on the right and the colon is doubled on
completes its 270° counterclockwise rotation as the caudad midgut itself to the left of midline. 7
also completes its rotation, resulting in the duodenum coursing inferior
and posterior to the SMA and the caecum located in the right lower Reversed rotation
quadrant. When completed, this rotation ensures that the attachment Reversed rotation has the caecum and colon positioned posterior to the
of the base of the midgut loop is spread along a diagonal stretching superior mesenteric vessels, and the duodenum subsequently crosses
from the ligament of Trietz on the left upper quadrant to the ileocecal anterior to it.
junction in the right lower quadrant of the abdomen. Stage 3 is the Malrotation
period of fixation, and lasts from the end of stage 2 until just after Malrotation is a spectrum of abnormalities that occurs when the normal
birth. The descending and ascending colon mesenteries fuse with the process of rotation is arrested at various stages. Most frequently, the
retroperitoneum, and the small bowel is fixed by a broad mesentery duodenojejunal flexure is located inferiorly and to the right of the mid-
from the duodenojejunal junction in the left upper quadrant to the line. In addition, the caecum has failed to reach its normal position in
ileocecal valve in the right lower abdomen. The broad base of the small the right iliac fossa and lies in a subhepatic or central position.
bowel mesentery stabilises its position and prevents volvulus. 5,6 Anomalies of Fixation
Malrotation can be grouped into syndromes arising from anomalies
of three categories: migration, rotation, and fixation. Volvulus neonatorum
A normal fixation of the midgut loop results in a broad diagonal attach-