 |
Coronal post contrast CT section through pancreas showing
absent 3rd part of duodenum beneath the pancreas. |
 |
Axial post contrast CT section through kidneys showing clumped duodenum infero medial to pancreas with antero posterior relation of superior mesenteric vessels.
|
Intestinal
malrotation can be broadly defined as any deviation from the normal 270°
counterclockwise rotation of the midgut during embryologic
development.
·
Malrotation
results not only in the malposition of the bowel but also in the malfixation of
the mesentery.
·
The
normally broad mesenteric attachment is shortened to a narrow pedicle that
predisposes the patient to the complication of midgut
volvulus.
·
Internal
hernia related to abnormal peritoneal fibrous bands (of Ladd) that attach to the
right colon is another complication of malrotation seen in
adults.
·
Conventional
radiography is neither sensitive nor specific for malrotation, although
right-sided jejunal markings and the absence of a stool-filled colon in the
right lower quadrant may be suggestive of this finding.
·
The
upper gastrointestinal barium series remains accurate for detection, and the
rules familiar to pediatric radiology also apply for adults—that is, the
duodenal—jejunal junction fails to cross the midline and lies below the level of
the duodenal bulb.
·
An
abnormal junction in an adult should not be dismissed as a normal variant.
·
Contrast
enema examination usually shows malposition of the right colon, but the cecum
may assume a normal location in up to 20% of patients.
·
The
contrast enema findings are also nonspecific because cecal location can be
variable without malrotation.
·
Many
cases of quiescent malrotation in adults are currently being detected on
cross-sectional imaging performed for various unrelated
reasons.
·
CT
not only shows the intestinal malpositioning seen on barium studies but also
depicts associated extraintestinal findings not evident on conventional
examinations. For example, deviation from the normal relationship between the
SMA and SMV is a useful indicator of malrotation.
·
In
most patients with quiescent malrotation, the SMA and SMV will assume a vertical
relationship or show left—right inversion.
·
Analogous
findings can be seen on sonography.
·
Abnormalities
of SMA—SMV orientation are not entirely diagnostic, however, because some
patients with malrotation will have a normal relationship, and a vertical or
inverted relationship can also be seen in patients without malrotation.
·
Therefore,
isolated detection of such an abnormality is not sufficient for diagnosis but
should warrant closer examination of the bowel.
·
Finally,
inspection of the pancreas in malrotation will reveal underdevelopment or
absence of the uncinate process.
·
Acute
complications of malrotation:
1.
Midgut
volvulus
2.
Internal
hernia
·
Regardless
of patient age, surgical treatment of quiescent malrotation should be considered
because surgery remains the only real safeguard against
complications.
Reference
: Intestinal Malrotation in Adolescents and Adults: Spectrum of Clinical and
Imaging Features, AJR December 2002 vol. 179 no. 6
1429-1435.
