++
Malrotation is a term used to describe a spectrum of anatomic
abnormalities resulting from incomplete rotation and fixation of the
intestine during early fetal development. Variants include incomplete,
nonrotation, or reversed rotation. Midgut volvulus is a devastating
consequence of the lack of bowel fixation that results in ischemic
infarction of much of the small and large intestine, with short
gut syndrome ensuing if volvulus is not recognized and treated emergently.
++
Malrotation is reported to occur with a frequency of 1 in 3500
to 6000 live births, although the actual incidence of malrotation
is unknown because many rotational anomalies remain asymptomatic
throughout life and are therefore undiagnosed.1 Either
sex can be affected, with the anomaly slightly more common in boys.
++
As described in Chapter 381, the midgut
normally herniates out of the peritoneal cavity into the umbilical
stalk at about week 5 of development in the human fetus. As the
intestine returns to the abdominal cavity between the 10th and 12th
week of gestation, a process of rotation turns it around the axis
of the superior mesenteric artery and fixation
of the intestine occurs, culminating with localization of the duodenojejunal
junction (ligament of Treitz) in the left upper abdomen and the
cecum in the right lower quadrant in the full-term infant (see eFig. 381.5). This results in the oblique
broad-based fixation of the mesentery to the posterior abdominal
wall that prevents volvulus from occurring. The various forms of
malrotation result from aberrant rotation and fixation of the bowel,
as well as associated abnormal mesenteric bands that may obstruct
the bowel (Ladd bands).
++
In nonrotation or incomplete rotation, the most common form of
malrotation, the cecum typically resides in the upper abdomen just
to the left of midline, and the duodenaljejunal segment lies anteriorly
and just to the right of midline; fixation of the mesentery is absent. This
anatomic derangement allows axial rotation of the midgut around
the superior mesenteric artery, resulting in midgut volvulus with the
potential for intestinal obstruction, ischemia, and necrosis.
++
Mixed rotational anomalies are a less common and highly variable group
of anomalies in which the rotational process is arrested or disrupted,
causing a spectrum of anatomic variations. Mesocolic (paraduodenal)
hernias are a rare group of malformations that result from failure
of the normal fixation of either the right or left mesocolon to
the posterior body wall. The resulting spaces create the potential
for intestinal obstruction due to sequestration and entrapment of the
small intestine between the mesocolon and the posterior body wall.
++
Rare cases of familial malrotation suggest a genetic link in
some cases.2
+++
Clinical Features
and Differential Diagnosis
++
The clinical consequences of malrotation vary depending upon
the length of the superior mesenteric artery pedicle and the fixation
of the bowel.3 Volvulus is the most ominous and concerning
presentation due to the resultant ischemia and bowel necrosis. It
occurs as the bowel twists on its axis, strangling the mesenteric
base (Fig. 397-1). Malrotation may also present with
obstruction due to kinking of the abnormally positioned duodenum;
duodenal obstruction from extrinsic compression by peritoneal bands
(Ladd’s bands) that extend across the duodenum as they course
from the right upper abdomen to the abnormally located cecum; and
associated intrinsic duodenal atresia, or stenosis.
Midgut volvulus can occur antenatally and result in proximal jejunal
atresia and congenital short gut syndrome.
++
++
Malrotation may occur as an isolated abnormality, but about half of
the patients with malrotation have other associated congenital anomalies,
including gastrointestinal (duodenal and/or intestinal atresias),
central nervous system, cardiac, respiratory, and genitourinary
systems abnormalities.4 All patients with congenital
diaphragmatic hernia (CDH), omphalocele, and gastroschisis have malrotation.
In addition, pyloric stenosis, Meckel diverticulum, Hirschsprung
disease, imperforate anus, esophageal atresia, biliary atresia and
abnormalities of the gallbladder and extrahepatic biliary tree,
prune belly, megacystis-microcolon syndrome, situs inversus, and
the asplenia-polysplenia congenital heart malformation syndrome
have been described in association with malrotation.5
++
Patterns of clinical presentation include midgut volvulus, partial
duodenal obstruction, and occasionally, chronic abdominal complaints.
The onset of symptoms can be acute, intermittent, or recurrent,
and the manner of presentation tends to be age dependent. The classic
and most common presentation of malrotation is with gastrointestinal
obstruction characterized by bilious emesis (see Chapter 389), but not all patients present with bilious emesis.6
++
The majority (75%) of cases of malrotation with volvulus
occur in the first week to month of life, and approximately 90% of
cases occur prior to 1 year of age. Physical findings in infants with
volvulus are variable and unreliable. The infant may be irritable,
with a soft abdomen, until the intestinal ischemia leads to bowel
necrosis, peritonitis, third-spacing of fluid, and signs and symptoms
of septic shock. Hematemesis, melena, and anemia may result from
intestinal mucosal ischemia. Midgut volvulus may be incomplete or
intermittent. Typically, patients are older and have chronic nonspecific
symptoms of abdominal pain, intermittent episodes of emesis (which
may be nonbilious), early satiety, weight loss, failure to thrive,
or malabsorption and diarrhea. With partial volvulus, the resultant
mesenteric venous and lymphatic obstruction may cause chylous ascites
or impair nutrient absorption and produce protein loss into the
gut lumen. Melena, guaiac-positive, or grossly bloody stools may
result from mucosal ischemia and may lead to anemia.
++
Duodenal obstruction may also occur with malrotation from kinking
of the abnormally positioned and tortuous duodenum, from intermittent
volvulus causing duodenal obstruction from torsion, or from extrinsic
obstruction from Ladd bands. Intrinsic duodenal obstruction from
atresia or stenosis must also be considered. Signs and symptoms
are similar and are typical of any high intestinal obstruction. They
include bilious emesis, abdominal pain, or both. Physical findings
may be similar to those patients with volvulus, but the presentation
is typically less acute than in midgut volvulus; thus, patients
may have persistent abdominal distension, vomiting with dehydration
and hypochloremic, hypokalemic, and metabolic alkalosis from vomiting.
Plain abdominal radiographs are variable and may demonstrate findings
suggestive of proximal intestinal obstruction (dilated proximal
intestine and stomach with little distal gas) or may be nonspecific
and unremarkable because proximal intestinal obstructions may be
decompressed by vomiting.
++
Chronic nonspecific abdominal complaints may also be due to malrotation.
This mode of presentation is more common in older patients. Symptoms
include chronic abdominal pain, chronic pancreatitis, weight loss,
failure to thrive, early satiety, intermittent diarrhea or blood
by rectum and are due to chronic partial duodenal obstruction or
intermittent volvulus. Presumably, symptoms result from intestinal obstruction
or from intermittent occlusion of the mesenteric venous or lymphatic
systems, causing edema of the bowel wall, mesentery, and mesenteric
lymph nodes. Chronic arterial insufficiency caused by a partial
volvulus may result in diarrhea, chronic abdominal pain, worsening
pain after meals (intestinal angina), or melena as a result of intestinal
mucosal ischemia.
++
If an infant or child presents with signs of intestinal obstruction,
initial diagnostic testing should not be prioritized over physiologic
stabilization, which occurs concurrent with the diagnostic evaluation.
Initial evaluation begins with a plain abdominal radiograph that
most often demonstrates a proximal bowel obstruction with a distended
stomach and proximal duodenum. Usually, there is a paucity of air
in the distal small bowel, but multiple, dilated loops of bowel
with air/fluid levels are also seen in malrotation with
volvulus. The most worrisome radiograph demonstrates a relatively “gasless” abdomen
secondary to sequestration of fluid into the bowel and abdominal cavity
portending significant intestinal ischemia or necrosis. Physical and
plain radiograph findings may be minimal early in presentation. Therefore,
in any case of bilious vomiting the diagnosis of malrotation with
volvulus should be considered, and an upper GI contrast study should
be performed. The classic contrast study shows a complete obstruction
in the second or third portion of the duodenum, with a tapering,
funnel appearance from the proximal dilated duodenum to the point
of obstruction that is reminiscent of a bird’s beak in
appearance. Partial obstruction of the duodenum shows a spiral or
corkscrew (coiled spring) appearance of the duodenum, with the proximal
small bowel to the right of midline (Fig. 397-2A).
++
++
In patients with malrotation but without volvulus, the diagnosis
of malrotation is made based on the position of the duodenaljejunal junction
(ligament of Treitz) (see Fig. 397-2B). The
normal position of the duodenaljejunal junction is to the left of
the spine at the level of the gastric antrum, fixed tightly to the posterior
body wall. In patients with malrotation, the duodenaljejunal junction
is typically found on the right side of the spine, inferior to the
duodenal bulb, and more anterior than expected. The lateral view
is very useful in assessing the anterior and posterior relations
of the duodenaljejunal junction. In addition, often all of the loops
of the proximal jejunum are found on the right side of the abdomen. Contrast
enema (barium or water-soluble contrast) is often the initial study
used in evaluating infants with more general concerns of neonatal
intestinal obstruction, and this study may suggest malrotation when
there is an abnormal position of the colon, with the entire colon
on the left side of the abdomen and the cecum in the upper abdomen
either midline or just to the left of midline. This finding is suggestive
but not definitive for malrotation because a high-riding or mobile
cecum is found in up to 15% of normal infants. In addition, duodenal
obstruction caused by malrotation may occur in the presence of a
normally positioned cecum.
++
Other imaging studies that demonstrate axial relations, such
as ultrasound or computed tomography (CT), may periodically demonstrate
evidence of malrotation. The typical finding on ultrasound is reversal
in the relation of the superior mesenteric artery (SMA) to the superior
mesenteric vein (SMV). Normally, the SMV is positioned to the right
of the SMA. If the SMV lies in an aberrant location, either anterior
or to the left of the SMA, malrotation may be present. If present,
this finding is noteworthy but not sufficiently reliable to establish
the diagnosis of malrotation with volvulus. Although attractive
as a diagnostic tool because it is noninvasive and generally can be
rapidly performed, its lack of sensitivity and specificity limit
its helpfulness.7 Malrotation may be recognized
as an incidental finding in patients undergoing radiologic investigation
for other disorders or unrelated symptoms.
++
Infants and children with acute presentation of midgut volvulus
or complete bowel obstruction require urgent operative correction
since a delay of only a few hours may determine whether ischemic
intestine remains viable and therefore salvageable. In the patient
in whom malrotation but not volvulus has been radiographically established,
urgency of operative correction is decided by several factors. In
the symptomatic patient, laparotomy and operative correction should
proceed as early as possible because contrast studies are not completely
reliable in determining if volvulus has occurred. In the asymptomatic
patient, the urgency of operative correction is lessened, but it
must be noted that acute vascular insufficiency of the midgut may
occur acutely at any age and at any time. When a diagnosis of malrotation
(without volvulus) is made in the older patient or adult during
the evaluation of nonspecific symptoms such as chronic abdominal
pain or constipation, it is often difficult to be certain whether
the symptoms that prompted radiographic evaluation are being caused
by the malrotation. In these instances some authors have recommended
laparoscopy to assess the width of the mesenteric fixation and possible laparoscopic
correction.8,9 This strategy has demonstrated equivalent
success rates to an open surgical approach and is minimally invasive,
but has not to date been widely accepted. It is controversial whether
an adult with incidental diagnosis of malrotation should undergo
operative intervention because the risk of volvulus is relatively
small.10,11
++
One additional dilemma is the circumstance of midgut rotational
abnormalities associated with congenital heart disease in the heterotaxia
syndromes. In this setting, careful observation of the asymptomatic
patient and deferral of the Ladd procedure until the cardiac physiology
is surgically stabilized appears to be appropriate.12
++
The operative management of malrotation and midgut volvulus has
not changed since the original description by William Ladd in the 1930s.
The procedure begins evisceration of the intestine and mesentery.
If malrotation with volvulus is present, midgut volvulus is relieved
by rotating the affected small intestine opposite the direction
of torsion, generally in a counterclockwise direction. The degree
of torsion is variable but may involve 1 or more complete (360 degree)
twists of the mesentery. Necrotic segments of intestine that do
not improve following reestablishment of blood flow are resected
with the creation of stomas or primary anastomosis of the viable
segments. If the entire midgut is necrotic, options include resection
with one or more stomas and central line placement for parenteral
nutrition, or closure without resection and palliative care following
an appropriate discussion with the family.
++
Once the mesentery has been untwisted, or if there was malrotation
without volvulus, the operative procedure proceeds with division
of Ladd bands. These peritoneal bands extend from the posterior
abdominal wall in the right upper abdomen to the abnormally positioned cecum.
Ladd bands typically cross the duodenum and can cause duodenal obstruction
from external compression. During this portion of the procedure,
the duodenum is also checked for any mechanical kinking and for
the possibility of intrinsic duodenal obstruction. The base of the
mesentery is maximally widened by dividing bands between the duodenum
and colon, and the duodenum and small intestine are placed in the
right abdomen and the cecum and right colon to the left of midline.
Appendectomy is considered standard because the malposition of the
cecum in the left upper abdomen can make diagnosis of a future appendicitis
challenging.
+++
Complications
and Prognosis
++
If the midgut (duodenum to mid-transverse colon) is not salvageable
at laparotomy, the survival rate is approximately 50% and
has historically been achieved only with permanent or long-term
parenteral nutrition. More recently, intestinal transplantation
(with or without liver transplantation) has become an alternative.
++
Results following surgical correction of malrotation are generally excellent,
in the absence of significant bowel loss at the time of surgery.13 Life
expectancy is normal and about half of patients have no further
complications, although many patients have subsequent episodes of
bowel obstruction from adhesion or have feeding difficulties.14 In
modern practice, immediate postoperative mortality is very low, being
increased in patients with intestinal necrosis, prematurity, and
the presence of other abnormalities. Recurrent volvulus and recurrent
duodenal obstruction are rare if the original procedure is complete.
Disorders of intestinal motility are relatively common after operative
correction for malrotation and may relate to adhesions, ischemic
injury to the intestinal nerves and muscles, or an underlying motility
abnormality.
++
The most serious complication of malrotation is short gut syndrome. Approximately
2% of children with malrotation survive with inadequate
intestinal length, and malrotation with midgut volvulus accounts
for about 20% of all children with short gut syndrome in the
pediatric population.15 These patients may be maintained by
parenteral nutrition and may eventually require small bowel transplantation
(see Chapter 131). Long-term outcome can also
be influenced by other associated anomalies, particularly those
that are associated with morbidity and mortality, including diaphragmatic
hernia, biliary tract anomalies, and complex cardiac anomalies.