AJR 2003; 180:1003-1006
© American Roentgen Ray Society
CT Diagnosis of Volvulus of the Descending Colon with Persistent Mesocolon
Albert Chen1,
Fei-Shih Yang1,
Shin-Lin Shih1,2 and
Chin-Yin Sheu1
1 Department of Radiology, Mackay Memorial Hospital, No. 92, Sec. 2, Chung-Shan
N. Rd., Taipei 10449, Taiwan.
2 Department of Radiology, Taipei Medical University, No. 250, Wu-Hsing St.,
Taipei 110, Taiwan.
Received May 29, 2002;
accepted after revision August 8, 2002.
Address correspondence to S.-L. Shih.
Introduction
Persistent descending mesocolon is a congenital anomaly that, in most
cases, is asymptomatic because of its short length
[1]. However, it may cause
intestinal obstruction by twisting of the colon
[2] or internal hernia with or
without a mesenteric defect [3,
4]. We report a case of
surgically proven volvulus of the descending colon with persistent mesocolon
in a 51-year-old woman. We discuss the probable pathogenesis, imaging
findings, and treatment.
Case Report
A 51-year-old woman with a history since childhood of chronic constipation
presented with increasing cramping abdominal pain of 6 days' duration.
Multiple similar episodes had occurred in the previous 2 years, with
spontaneous remission. The physical examination showed a distended abdomen
with decreased bowel sounds and tenderness on the left side. The findings of
routine laboratory tests were normal. There was no history of surgery or
laxative use.
Abdominal radiography revealed a large, air-filled bowel loop in the left
upper abdomen with marked elevation of the left hemidiaphragm. The ascending
and transverse colons were distended with feces. CT (Figs.
1A,
1B,
1C,
1D,
1E,
1F) showed a markedly dilated
(12 cm) bowel loop with two limbs that tapered in size and coursed inferiorly
into a round soft-tissue mass with a whirled configuration in the left colonic
compartment. The afferent and efferent loops of the descending colon formed
the caudal aspect of the whirled mass. No bowel distention was identified
distally. Loops of small bowel were seen in the left iliac fossa. No signs of
bowel strangulation or perforation were seen. These imaging findings were
interpreted as a simple closed-loop colonic obstruction caused by a tightly
twisted mesentery, compatible with volvulus.
View larger version (110K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A. —51-year-old woman with volvulus of descending colon. CT
topogram shows markedly distended loop occupying left upper abdomen.
Feces-filled ascending and transverse colons are mildly dilated and
displaced.
|
|
View larger version (106K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C. —51-year-old woman with volvulus of descending colon.
Contrast-enhanced CT scan obtained 2 cm caudad to B shows other limb of
distended loop (arrows) tapering in size and coursing into round
soft-tissue mass with whirled configuration (arrowheads).
|
|
View larger version (104K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1E. —51-year-old woman with volvulus of descending colon.
Contrast-enhanced CT scan obtained 2 cm caudad to D shows afferent and
efferent loops of whirled mass (arrowheads) are at level of
descending colon. Note medial position of descending colon
(arrows).
|
|
View larger version (101K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1F. —51-year-old woman with volvulus of descending colon.
Contrast-enhanced CT scan obtained at level of iliac fossa reveals normally
distributed mesentery and mildly dilated transverse colon and cecum. Note
opacified small-bowel loops in iliac fossa.
|
|
At surgery, we found a 720° clockwise rotation of a segment of the
descending colon that resulted in volvulus
(Fig. 1G). The descending colon
was redundant and had a persistent, long mesocolon. The cecum and the
ascending, transverse, and proximal descending colons were dilated. The
collapsed distal descending and sigmoid colons appeared normal. No bowel
necrosis or perforation was found. Derotation and segmental colectomy were
performed with primary end-to-end anastomosis. The patient had an uneventful
course after surgery and was discharged from the hospital 12 days after
admission.
Discussion
Volvulus of the colon represents the third most common cause of colonic
obstruction after carcinoma and diverticulitis. The disorder is caused by a
twisting of the intestine on its mesenteric axis, resulting in complete or
partial obstruction. It may reduce spontaneously and recur chronically, but
more frequently volvulus of the colon presents acutely. When the blood supply
to the bowel is compromised, necrosis and perforation supervene.
Volvulus occurs in those portions of the colon possessing a mesentery,
including the sigmoid, cecum, and transverse colon. Rarely, volvulus develops
in the splenic flexure [5]
because of congenital absence or surgical division of the normal fixation
structures (the gastrocolic, phrenicocolic, and splenocolic ligaments). The
descending colon is usually surrounded by peritoneum on three sides and is a
retroperitoneal structure without a mesocolon. However, the primitive dorsal
mesocolon may fail to fuse with the parietal peritoneum in the fourth through
the fifth month of gestation, resulting in a persistent descending mesocolon
[1]. This failure permits
mobility of the descending colon, resulting in considerable variation in its
position. Commonly, the descending colon swings to the midline or slightly to
the left of the midline [3],
leaving a space into which all or a part of the small bowel may migrate. In
addition, chronic constipation may result in a markedly redundant, dilated
colon that is often associated with an elongated mesocolon.
Because of persistence of the suspending dorsal mesentery and her long-term
constipation, our patient had a long, redundant segment of descending colon;
an associated large mesocolon; and approximation of two ends of the loop. This
configuration allowed torsion, resulting in a closed-loop obstruction. It is
likely that the patient's periodic abdominal pain and distention may have
represented recurrent episodes of volvulus with spontaneous derotation.
The diagnosis of colonic volvulus can generally be suspected on
conventional abdominal radiography and can be confirmed with a barium enema.
However, the latter offers no information about complications such as bowel
ischemia or other abnormalities outside the bowel wall.
A specific CT sign for volvulus is the whirl sign (Figs.
1C and
1E), which was originally
described in the midgut by Fisher
[6]. Subsequently, this sign
was found to be helpful in diagnosing sigmoid
[7] and cecal
[8] volvulus. The whirl is
composed of tightly twisted bowel, mesentery, and vessels. The tightness of
the whirl is proportional to the degree of rotation. CT findings of
strangulation include circumferential thickening of bowel wall, intestinal
pneumatosis, mesenteric congestive haziness, and mesenteric hemorrhagic fluid
[9]. CT is thus much more
specific than a barium study in delineating the presence, cause, level, and
degree of bowel obstruction; signs of strangulation; and associated
abnormalities outside the bowel wall, such as calcified lymph nodes in the
mesentery [8].
In our patient, the markedly distended bowel loop depicted on radiography
was suggestive of volvulus, but the exact level of obstruction was hard to
identify with confidence. The whirl sign in the left colonic compartment was
diagnostic for volvulus, and the level of the obstruction was indicated by
identifying the afferent and efferent loops as being from the descending
colon. If a patient is not known to have persistent mesocolon, one would
hesitate to make the diagnosis of volvulus of the descending colon because it
is thought of as a retroperitoneal organ. The medial position of the
descending colon and small-bowel loops in the left iliac fossa might serve as
a diagnostic clue for the presence of persistent mesocolon. To our knowledge,
only one other such case has been reported
[2], but the report did not
include imaging studies. Our report is the first to include the findings of
descending colon volvulus on radiography and CT.
The main differential diagnosis is splenic flexure volvulus, which is
caused by lack of fixation structures and a resultant highly mobile colon.
Although no CT appearance has been described in the literature, we believe
that in our patient the normal position of the splenic flexure and afferent
and efferent loops at the level of the descending colon are highly
discriminatory features. Surgical exploration may be needed to make the
definitive diagnosis.
The treatment for volvulus depends on whether the bowel is strangulated.
Fever, the presence of significant leukocytosis, or peritoneal signs suggest
bowel strangulation or perforation. Strangulated volvulus demands immediate
operative reduction and has a grave prognosis. The goals of therapy in
non-strangulated volvulus are relief of torsion and prevention of
recurrence.
Our patient had no clinical or radiologic evidence of strangulation or
perforation. Decompression by barium enema or colonoscopy was not attempted
because of the distance of the obstruction from the anal verge and the
tightness of the twisting seen on CT. Viability of the bowel was confirmed
surgically. The patient underwent segmental colectomy to prevent volvulus
recurrence.
In summary, volvulus of the descending colon may occur when a persistent
mesocolon is present. Chronic constipation leads to lengthening of the colon
and is a predisposing factor for volvulus. The location of the whirl sign,
associated bowel dilatation, and the origin of the afferent and efferent loops
on CT accurately determine the cause and level of obstruction. CT can also
show signs of strangulation and perforation and thus is helpful in planning
treatment.
References
- Balthazar EJ. Congenital positional anomalies of the colon:
radiographic diagnosis and clinical implications. II. Abnormalities of
fixation. Gastrointest Radiol
1977;2:49
–56[Medline]
- Vyas KC, Joshi CP, Misra S. Volvulus of descending colon with
anomalous mesocolon. Indian J Gastroenterol
1997;16:34
–35[Medline]
- Morgenstern L. Persistent descending mesocolon. Surg
Gynecol Obstet
1960;110:197
–202
- Liew KL, Choong CS, Shiau GF, Yang WC, Su CM. Descending mesocolon
defect herniation: case report. Changgeng Yi Xue Za
Zhi 1999;22:133
–137[Medline]
- Mindelzun RE, Stone JM. Volvulus of the splenic flexure:
radiographic features. Radiology
1991;181:221
–223[Abstract/Free Full Text]
- Fisher JK. Computed tomographic diagnosis of volvulus in intestinal
malrotation. Radiology
1981;140:145
–146[Abstract/Free Full Text]
- Shaff MI, Himmelfarb E, Sacks GA, Burks DD, Kulkami MU. The whirl
sign: a CT finding in volvulus of the large intestine. J Comput
Assist Tomogr 1985;9:410[Medline]
- Frank AJ, Goffner LB, Furauff AA, et al. Cecal volvulus: the CT
whirl sign. Abdom Imaging
1993;18:288
–289[Medline]
- Balthazar EJ, Birnbaum BA, Megibow AJ, et al. Closed-loop and
strangulating intestinal obstruction: CT signs.
Radiology
1992;185:769
–775[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Introduction
Case Report
