Accurate and timely radiographic evaluation can be essential in preventing complications of small bowel volvulus. Given the potentially misleading presentation, however, identifying this condition can be challenging. This article summarizes the typical radiographic features of small bowel volvulus originating distal to the ligament of Treitz in patients found at surgery to have normal rotation of the gastrointestinal tract and normal mesenteric development.
is in the Department of Radiology, Brooke Army Medical Center,
Fort Sam Houston, TX.
ccurate and timely radiographic evaluation can be crucial for
preventing the severe complications of small bowel volvulus. The
upper gastrointestinal series is the usual method of detecting
midgut volvulus associated with malrotation.
Although the exact incidence is unknown, however, a small but
significant subset of patients can have either focal or extensive
small bowel volvulus without malrotation. In the absence of an
enteric tube, bowel distension, or scoliosis,
the duodenum and ligament of Treitz (LOT) are positioned normally.
Therefore, a positive contrast examination to the level of the LOT
may miss this condition. Moreover, since small bowel volvulus
distal to a normal duodenum and LOT may not be anticipated, distal
gas patterns that would ordinarily suggest volvulus may be
minimized or dismissed as spurious, so that vascular complications
develop as the patient is evaluated by other modalities.
With these pitfalls in mind, this article summarizes the typical
radiographic features of small bowel volvulus originating distal to
the LOT in patients found at surgery to have normal rotation of the
gastrointestinal tract and normal mesenteric development.
Plain film evaluation
Although midgut volvulus with malrotation can produce normal
plain film findings,
this collection without malrotation does not include any normal
plain radiographs. The specific positive findings correlate with
the content (gas or fluid) and extent of the volvulus, and are
similar to the alterations when malrotation is a
A gas-filled volvulus should be suspected when a small bowel
loop assumes a "coffee-bean" configuration
(figure 1A). When correlated with direct inspection, the coffee
bean represents either the tightly folded bowel loop associated
with focal volvulus or a closed loop at the distal end of small
bowel spiraling around the superior mesenteric artery (figure 2).
The depicted loop is twisted focally in both situations. The "lip"
in the center of the bean can be traced to an incisura, which
represents the site of the twist.
In infants, this loop interrupts the uniformly distributed
circular and tubular gas-filled bowel loops normally seen on supine
films. Focal distension (figure 1 A) and/or isolation from other
small bowel loops suggest that this configuration is significant,
rather than a normal variant. Retention of gas on sequential supine
and prone radiographs excludes simple obstruction and distension of
transverse or sigmoid colon by elevation as alternative causes of
focally distended bowel during infancy.
The pseudotumor associated with a fluid-filled volvulus is
distinguished easily from intussusception, normal variations in the
gas pattern, an uncomplicated fluid filled duplication, and medical
conditions that alter the gas pattern. Medical causes of bowel
distension in infants, such as infection and milk-soy protein
typically produce uniform bowel distension. Interruption of uniform
distension by a mass effect implies an acute abdomen with
obstruction--most commonly from intussusception
or small bowel vovulus.
An intraluminal mass and an age over 3 months suggests
intussusception. A soft tissue mass associated with small bowel
obstruction in a younger baby implies small bowel volvulus
producing a pseudotumor sign of Frimann-Dahl
(figure 3). Although an uncomplicated small bowel duplication can
resemble a pseudotumor associated with volvulus, this lesion does
not typically produce the complete small bowel obstruction seen in
figure 3B. Simulation of the pseudotumor and small bowel
obstruction by focal inflation of a tortuous transverse colon on
the supine film (a normal variant in neonates and infants) can be
excluded by displacing gas into the right and left colon in the
Positive contrast studies
We recommend adding a small bowel series to a normal upper
gastrointestinal series when the above gas patterns suggest a
volvulus distal to a normal duodenum and LOT (figures 3C to 3E).
After filling with positive contrast (figure 3E), a pseudotumor
also has a coffee-bean configuration analogous to the gas-filled
coffee bean (figure 1A) and the appearance seen at surgery (figure
2). Like the gas-filled coffee bean, the pseudotumor may represent
a focal volvulus or a closed loop (figures 2, 3A, 3B, and 3E) at
the distal end of small bowel spiraling around the superior
mesenteric artery (figures 3C and 3 D).
Although omphalormesenteric duct remnants,
adhesions, internal hernias, polyps, foreign body impactions,
mesenteric defects, duplications,
and even mesenteric cysts
have been associated with small bowel volvulus without malrotation,
we have noted a more striking association with colonic obstruction
from meconium plugs (figure 3F), small left colon (figure 1B), and
Hirschsprung disease (figure 5). Violent peristalsis around hairpin
turns in the small bowel proximal to the colonic obstruction may
provoke this complication.
In light of this potential association, it is important to
search for colonic obstruction as a potential cause of small bowel
volvulus without malrotation. Conversely, the small bowel should be
inspected carefully for a pseudotumor or gas-filled coffee bean in
any newborn with colonic obstruction from colon inertia and/or
Occasionally, the spiral may extend into the duodenum. In such
cases, a straight descending duodenum that is firmly anchored to
followed by a horizontal spiral distal to that point should suggest
that the spiral originates distal to the LOT and that it is
restrained from a more vertical position by a normally anchored LOT
that is displaced by the volvulus and/or gastrointestinal
(figure 5). When the duodenum spirals because of malrotation, the
spiral is usually more vertical because of a low and medial LOT and
the descending duodenum typically participates in the spiral
Sonography may disclose an unanticipated volvulus during an
evaluation for abdominal pain, possible pyloric stenosis, or
possible intussusception. Alternatively, sonography may be employed
when complete small bowel obstruction is not recognized on the
prone plain film
(figure 3B) so that other possibilities, such as the uncomplicated
small bowel duplication originally postulated for this patient, are
The sonographic appearance of small bowel volvulus (with or
without malrotation) correlates with the position of the transducer
in relationship to the coil (figures 3C and 3D) or pseudotumor
(figures 3A and 3E). When the probe is held axial (transverse) to
the abdomen and the coil (figure 3C), the "whirlpool sign" is
(figure 3G). Color doppler interrogation can be utilized to depict
the vascular components of the whirlpool.
Clockwise motion of the superior mesenteric vein around the
superior mesenteric artery as the transducer is moved caudally is
considered a definite sign of midgut volvulus.
The more distal aggregation of twisted, fluid-filled loops
responsible for the pseudotumor produce a coffee-bean (figure 3H)
or "dumbbell" (figure 3I) configuration depending on the
orientation of the probe in relationship to the pseudotumor. The
coffee bean is depicted when the transducer is directly over the
pseudotumor. The dumbbell may be produced by the very tight twist
at the entrance of the coil into the pseudotumor.
The relative positions of the superior mesenteric artery and the
superior mesenteric vein do not reliably predict the presence or
absence of a predisposing malrotation.
This distinction does not affect the initial clinical management,
CT has the potential to clearly depict the small bowel circling
and encompassing two concentric vascular coils, which in turn
surround the superior mesenteric artery. As axial sections are
evaluated in a cranial to caudal direction, the superior mesenteric
vein rotates around the superior mesenteric artery.
In patients without malrotation, this spiral may be
counterclockwise (figures 7A to 7E) rather than the typical
clockwise rotation seen when malrotation is a predisposition. An
additional "wheel" between this venous spiral and the superior
mesenteric artery is produced by twisted small branches of the
superior mesenteric artery (figures 7A to 7E). Impaired arterial
flow is inferred when the superior mesenteric artery (the "hub" of
these wheels) is abnormally small (figures 7A to 7E). Three
dimensional reconstruction can display the length of the superior
mesenteric vein spiral directly.
Small bowel volvulus without malrotation may occur for no
obvious reason or secondary to known predispositions. In babies,
this condition may be provoked by colonic obstruction from colon
inertia and Hirschsprung disease. Since volvulus may be more
emergent but less obvious than the colonic obstruction, it is
particularly important to anticipate a potential association of
volvulus with a second distal obstruction, and to give a convincing
account of plain film findings that suggest this complication.
Although an upper gastrointestinal series is the preferred
method for confirming volvulus predisposed by malrotation, this
exam, as well as the barium enema, are not adequate for depicting
small bowel volvulus without malrotation. Therefore, when clinical
or plain film findings include this possibility, a small bowel
series should be added to the upper gastro-intestinal series.
Although other imaging studies have been used in this situation,
usually a small bowel series is the most rapid way to confirm this
In addition to the potential for a second more distal
obstruction, three other unique findings may be demonstrated when
these patients are evaluated:
1) restriction of the volvulus to the area between a normally
positioned ligament of Treitz and the cecum;
2) an unaffected descending duodenum while the rest of the
duodenum spirals in a horizontal rather than vertical orientation;
3) counterclockwise rather than clockwise rotation of the small
bowel, superior mesenteric vein, and proximal branches of the
superior mesenteric artery around the superior mesenteric artery.
The views expressed herein are those of the author and do not
necessarily reflect the views of the Department of the Army or
the Department of Defense.
The author wishes to thank Ms. Suzy M. Kai, Editorial Assistant,
Cardiology Service, for her help typing and preparing this
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