AJR 2000; 174:685-687
© American Roentgen Ray Society
The Ileosigmoid Knot
CT Findings
Sang-Hoon Lee1,
Young Ha Park1 and
Yong Sung Won2
1
Department of Radiology, St. Vincent's Hospital, The Catholic University of
Korea, 93 Ji-Dong, Paldal-gu, Suwon, Kyunggido 442-723, South Korea
2
Department of General Surgery, St. Vincent's Hospital, The Catholic University
of Korea, Kyunggido 442-723, South Korea.
Received May 24, 1999;
accepted after revision August 24, 1999.
Address correspondence to S.-H. Lee
Introduction
The ileosigmoid knot (also known as compound volvulus) is a rare cause of
intestinal obstruction [1]. The
condition is initiated by loops of ileum wrapping around the base of a
redundant sigmoid loop. We provide a drawing outlining the specific features
of the ileosigmoid knot in our patient
(Fig. 1A). Because of its
infrequency, the radiographic findings of the ileosigmoid knot are
sporadically described [2] and
include a dilated loop of the pelvic colon, the evidence of a small intestinal
obstruction, and the retention of feces in an undistended proximal colon. To
our knowledge, the CT findings of the ileosigmoid knot are not described in
the radiology literature.
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Fig. 1A. —76-year-old man with ileosigmoid knot, acute colic, and abdominal
distention (symptom duration, 1 day). Drawing depicts anatomic relationship of
colon and small intestine. Note medial deviation of descending colon and cecum
(arrows) with medial beak appearance (arrowheads).
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Case Report
A 76-year-old man was admitted to the hospital with acute colic and
distention of the abdomen (symptom duration, 1 day). One year before this
admission, the patient had been diagnosed with irritable bowel syndrome. At
that time, barium enema revealed a mildly redundant sigmoid colon. An
abdominal radiograph with the patient supine (taken after this admission)
revealed diffuse dilatation of small-bowel loops in association with a large
gas-filled loop of the bowel in the mid abdomen extending to the right lower
abdomen (Fig. 1B).
Contrast-enhanced abdominal CT (Tomoscan AV Expander Plus 1; Philips Medical
Systems, Best, the Netherlands) revealed findings suggestive of a sigmoid
volvulus: a dilated loop of the sigmoid colon with a thin wall in the right
lower abdomen (Fig. 1C),
whirling of the sigmoid mesocolon and mesenteric root (Figs.
1D,1E,1F),
and afferent and efferent limbs of the sigmoid colon with beak appearances
(Figs. 1D and
1E). Additionally, ileal loops
were wrapped around the central whirl resulting in an ileosigmoid knot (Figs.
1D,1E,1F).
The whirl sign is visible on more contiguous slices extending from L4 to the
mid sacral level. We also noted dilated distal small bowel loops with
pneumatosis. The cecum and the distal descending colon (retaining a small
amount of fecal material) were deviated medially with a pointed appearance of
their medial border (Fig.
1D).
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Fig. 1B. —76-year-old man with ileosigmoid knot, acute colic, and abdominal
distention (symptom duration, 1 day). Abdominal radiograph with patient supine
reveals dilated sigmoid loop (small arrows) in mid abdomen extending
to right lower abdomen with distended small intestine. Note medially deviated
distal descending colon with faintly visualized feces (large
arrows).
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Fig. 1C. —76-year-old man with ileosigmoid knot, acute colic, and abdominal
distention (symptom duration, 1 day). CT scan at level of L3 shows markedly
dilated ahaustral sigmoid colonic loop with air-fluid level
(arrows).
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Fig. 1D. —76-year-old man with ileosigmoid knot, acute colic, and abdominal
distention (symptom duration, 1 day). CT scan at level of aortic bifurcation
shows dilated loop of intestine with central mesenteric vessels forming whirl
(large white arrow) and tightly twisted ileum (small white
arrows). Note beak appearance of afferent limb of volvulus (white
arrowhead) and medially deviated distal descending colon and cecum with
pointed appearance at medial aspect (black arrowheads).
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Fig. 1E. —76-year-old man with ileosigmoid knot, acute colic, and abdominal
distention (symptom duration, 1 day). CT scan obtained 3 cm below level of
C shows beak appearance of efferent limb of volvulus (black
arrow). Note twisted ileal loops (arrowheads) surrounding
central whirl (white arrow).
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Fig. 1F. —76-year-old man with ileosigmoid knot, acute colic, and abdominal
distention (symptom duration, 1 day). CT scan obtained at level slightly lower
than D reveals gas-filled ileal loops (arrowheads) surrounding
whirl (arrow).
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Discussion
The ileosigmoid knot is a well-recognized condition in certain African,
Asian, and Middle Eastern nations; however, the condition is an unusual entity
in the Western world [3]. In an
ileosigmoid knot, closed proximal loops of the ileum become congested and
gangrenous in a few hours; therefore, the early recognition and surgical
treatment of ileosigmoid knots are essential. Despite reports that describe
the radiographic appearance and clinical features of the ileosigmoid knot,
diagnosis of an ileosigmoid knot is difficult because of its infrequency and
atypical radiographic findings. Consequently, this rare abdominal condition is
usually diagnosed during exploratory laparotomy.
Although the basic requirements for an ileosigmoid knot are still
controversial, most radiologists agree that they include a hypermobile small
intestine with markedly elongated mesentery and a redundant omega-shaped
sigmoid colon with a long mesocolon and a short attachment at the base of the
mesentery. Shepherd [4]
described the ileosigmoid knot as a primary event with a hyperactive ileum
winding around the narrow pedicle of a passive sigmoid. In most cases, the
ileum (active component) wraps around the sigmoid colon rather than the
reverse; therefore, there is a higher incidence of small-bowel strangulation
than of sigmoid strangulation. In our patient, a short period of active
abdominal symptoms preceded gangrenous change of the bowel loops despite
urgent surgical intervention. We presume that a tight ileal twist caused a
closed-loop obstruction, resulting in acute vascular compromise and
small-bowel necrosis.
CT can reveal the findings of a sigmoid volvulus including the
characteristic whirl sign created by the twisted intestine and mesocolon
[5,6].
CT can also reveal signs of bowel ischemia caused by strangulation such as
pneumatosis. However, the findings of an ileosigmoid knot are not easily
detected because the ileal twist is higher in the abdomen than the location of
a sigmoid volvulus. The whirl is visible on more contiguous slices than that
of the sigmoid volvulus. Compared with a radiograph of the abdomen, CT can
detect medial deviation of the distal descending colon with a pointed
appearance of its medial border—a distinct feature of the ileosigmoid
knot. We presume two possible causes for these features. First, a traction
effect causes the peritoneum of the left paracolic gutter to move toward the
center of the knot. Second, a mass effect of distended ileal loops interposes
between the descending and proximal sigmoid colon and the left body wall. Even
though the cecum may be deviated medially in many patients, the pointed
appearance of its medial border concurrent with the medial deviation of the
distal descending colon are helpful features in diagnosing an ileosigmoid
knot. In our patient, we noted ascites in both paracolic gutters with tightly
stretched terminal ileum between the sigmoid mesocolon and the cecum. This
finding might have had a role in causing the medial deviation of the cecum and
descending colon.
In conclusion, the ileosigmoid knot is a rare cause of intestinal
obstruction. As the knot tightens, closed-loop obstruction of the small bowel
ensues, with rapid gangrene of the involved loops. Treatment of an ileosigmoid
knot should differ from that of a sigmoid volvulus. More conservative care,
such as endoscopic or hydrostatic reduction, often alleviates problems
associated with a sigmoid volvulus. Though uncommon, an ileosigmoid knot
should be differentiated from a sigmoid volvulus.
References
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Alver O, Oren D, Tireli M, et al. Ileosigmoid knotting in Turkey.
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Shepherd JJ, Ninety-two cases of ileosigmoid knotting in Uganda.
Br J Surg
1967;54:561-566[Medline]
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Catalano O. Computed tomographic appearance of sigmoid volvulus.
Abdom Imaging
1996;21:314-317[Medline]
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Shaff MI, Himmelfarb E, Sacks GA, et al. The whirl sign: a CT
finding in volvulus of the large bowel. J Comput Assist Tomogr
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