DOI:10.2214/AJR.05.1490
AJR 2007; 189:W4-W6
© American Roentgen Ray Society
MDCT Diagnosis of an Appendiceal Mucocele with Acute Torsion
Jeffrey J. Hebert1 and
Perry J. Pickhardt1
1 Both authors: Department of Radiology, University of Wisconsin Medical School,
E3/311 Clinical Science Center, 600 Highland Ave., Madison, WI
53792-3252.
Received August 24, 2005;
accepted after revision October 25, 2005.
Address correspondence to P. J. Pickhardt.
WEB
This is a Web exclusive article.
Keywords: abdominal imaging • acute abdomen • appendiceal torsion • appendicitis • MDCT • mucinous cystadenoma • mucocele
Introduction
Acute torsion of the appendix is a rare cause of the acute abdomen that was
first described in 1918 [1].
One pathology-based review found torsion in only two cases of more than 3,000
appendectomy specimens, whereas a second pathology-based review found no
examples of torsion among 71,000 specimens
[2,
3]. Mucoceles of the appendix,
originally described by Rokitansky in 1842, are not as rare but are found in
only about 0.1–0.3% of appendectomy specimens
[4,
5]. Furthermore, torsion
complicating a mucocele of the appendix is exceedingly rare, with only a few
scattered cases reported in the English-language literature
[4,
6,
7].
To our knowledge, only one case of appendiceal torsion (without mucocele)
had preoperative imaging performed
[8], and no reported cases of
mucocele torsion have been documented on preoperative imaging. We report a
case of acute torsion of an appendiceal mucocele that was diagnosed
preoperatively on MDCT.
Case Report
A 59-year-old man presented to the emergency department with acute onset of
right lower quadrant abdominal pain. Medical history and physical examination
were suggestive of acute appendicitis. Laboratory evaluation included an
elevated WBC count of 12,300/µL with a slight left shift. The patient was
referred for preoperative MDCT evaluation. The study was performed after the
patient had ingested 1,000 mL of dilute iodinated contrast material
(diatrizoate) and after 100 mL of IV contrast material (iohexol) had been
administered. Rectal contrast medium was not administered.
A nonfocused examination of the abdomen and pelvis with the patient in the
supine position was performed on a 16-MDCT scanner using a 1.25-mm collimation
displayed in 5-mm sections during the portal venous phase. The original data
set was subsequently reconstructed and was displayed at 2.5-mm-thick sections
with a 2-mm interval. Soft-copy interpretation was performed on a PACS
workstation using stack mode review technique. Multiplanar reconstructions
were obtained from the thinner sections.
The MDCT study showed an oblong tubular structure that was 12 cm long and
was dilated to 3 cm in width and corresponded to the expected location of the
appendix (Figs. 1A,
1B,
1C, and
1D). The dilated appendiceal
lumen was filled with fluid-attenuation material. Positive oral contrast
material was identified in the cecum, but none was visualized in the abnormal
appendix. At the base of the appendix, abrupt luminal tapering was noted with
a whorled appearance to the supplying mesenteric fat and vessels.
Periappendiceal inflammatory changes were evident. The appendix extended deep
into the pelvis. Curved multiplanar images depicted the mucocele to better
advantage than transverse images alone
(Fig. 1D). A preoperative
imaging diagnosis of mucocele of the appendix complicated by acute torsion was
communicated to the referring clinician and surgeon.
View larger version (104K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1A —MDCT evaluation of 59-year-old man with acute abdominal pain
in right lower quadrant due to torsion of appendiceal mucocele. Transverse
contrast-enhanced MDCT images show contrast-filled cecum (asterisk,
A) and dilated fluid-filled structure (arrow, C)
separated by narrow appendiceal base. Note whorled appearance of
periappendiceal fat and vessels (arrowheads, A and B),
which is indicative of torsion. Note also lateral wall thickening of mucocele
and infiltration of surrounding fat, suggesting inflammation or early
infarction.
|
|
View larger version (104K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1B —MDCT evaluation of 59-year-old man with acute abdominal pain
in right lower quadrant due to torsion of appendiceal mucocele. Transverse
contrast-enhanced MDCT images show contrast-filled cecum (asterisk,
A) and dilated fluid-filled structure (arrow, C)
separated by narrow appendiceal base. Note whorled appearance of
periappendiceal fat and vessels (arrowheads, A and B),
which is indicative of torsion. Note also lateral wall thickening of mucocele
and infiltration of surrounding fat, suggesting inflammation or early
infarction.
|
|
View larger version (114K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1C —MDCT evaluation of 59-year-old man with acute abdominal pain
in right lower quadrant due to torsion of appendiceal mucocele. Transverse
contrast-enhanced MDCT images show contrast-filled cecum (asterisk,
A) and dilated fluid-filled structure (arrow, C)
separated by narrow appendiceal base. Note whorled appearance of
periappendiceal fat and vessels (arrowheads, A and B),
which is indicative of torsion. Note also lateral wall thickening of mucocele
and infiltration of surrounding fat, suggesting inflammation or early
infarction.
|
|
View larger version (149K):
[in this window]
[in a new window]
[as a PowerPoint slide]
|
Fig. 1D —MDCT evaluation of 59-year-old man with acute abdominal pain
in right lower quadrant due to torsion of appendiceal mucocele. Curved coronal
reformatted MDCT image obtained from thin-section reconstructed data shows
torsed mucocele to better advantage than A–C. Note twisted
appendiceal base connecting cecum to mucocele (arrow).
|
|
The patient was taken urgently to the operating room, where an open
appendectomy procedure was performed. The appendix was grossly dilated and
gangrenous, with torsion identified at its base. There was no spillage of the
luminal contents at surgery. Pathologic evaluation revealed a 12 x 6
x 4 cm dilated appendix with acute ischemic changes and areas of
infarction. The appendiceal lumen was filled with more than 100 mL of
tenacious yellow gelatinous mucoid material. The histologic diagnosis was
mucinous cystadenoma. The postoperative course was uneventful.
Discussion
Acute torsion of the appendix is rare, and mucoceles of the appendix are
uncommon. The combination of acute torsion with an appendiceal mucocele is
exceedingly rare, with very few reported cases
[4,
6,
7]. On the basis of our review
of the literature, we believe that our case is the first in which a torsed
mucocele was diagnosed preoperatively and that it is also the first in which
appendiceal torsion is described on CT. In one prior case report,
investigators described the sonography findings of appendiceal torsion without
an underlying mucocele [8].
The clinical presentation of appendiceal torsion is generally
indistinguishable from acute appendicitis. Because it is such a rare entity,
appendiceal torsion is usually not specifically considered on clinical
grounds, particularly a torsed mucocele. This case shows the utility of MDCT
and multiplanar evaluation for diagnosis. The routine use of 2D multiplanar
reconstructions for abdominal MDCT is becoming increasingly common because of
the wide availability of advanced workstations.
In addition to appendiceal mucocele, the differential diagnosis for a
cystic pelvic mass includes ovarian lesion in women and abscess, peritoneal
inclusion cyst, mesenteric cyst, duplication cyst, and Meckel's diverticulum.
As shown in this case, the multiplanar reformatted 2D images may allow the
differential diagnosis to be narrowed by revealing the organ of origin.
Increased diagnostic confidence with multiplanar CT has been shown in more
typical cases in which patients were being evaluated for acute appendicitis
[9].
In our patient, both coronal and sagittal reconstructed images more clearly
depicted the continuity of the dilated fluid-filled tubular structure with the
cecal base. However, transverse CT images are still the mainstay for primary
evaluation; in this case, the transverse images best depicted the whorl of
mesenteric fat and vessels around the appendiceal axis that was indicative of
torsion.
Unlike mucosal neoplasms of the rest of the colon and rectum, most mucosal
neoplasms of the appendix are mucin-rich, show circumferential mucosal
involvement, and have a strong propensity to form mucoceles
[5]. Mucinous neoplasms are the
most common cause of an appendiceal mucocele, which is a macroscopic
description that simply refers to a grossly distended appendix. Most mucoceles
are benign and relatively asymptomatic; they are occasionally detected as an
incidental finding at abdominal imaging. Symptomatic presentation can include
superinfection, intussusception, right ureteral obstruction, pseudomyxoma
peritonei, and torsion.
A preoperative diagnosis of a mucocele should persuade the surgeon to
perform an open procedure to avoid the potential complications of mucinous
spillage. CT is an ideal method for evaluating mucoceles because the anatomic
relationship of the elongated cystic mass to the cecum is usually more
apparent and the sensitivity for detecting mural calcification is increased
compared with other imaging techniques.
In conclusion, this case report documents the preoperative imaging
diagnosis of acute torsion of a mucocele of the appendix and shows the utility
of multiplanar evaluation made possible by MDCT.
References
- Moten AL, Williams RS. Torsion of the appendix. Med J
Aust 2002; 177:632[Medline]
- Val-Bernal JF, Gonzalez-Vela C, Garijo MF. Primary acute torsion of
the vermiform appendix. Pediatr Pathol Lab Med1996; 16:655
-661[CrossRef][Medline]
- Merrett ND, Lubowski DZ, King DW. Torsion of the vermiform
appendix: a case report and review of literature. Aust N Z J
Surg 1992; 62:981
-983[Medline]
- King-Pan C. Volvulus complicating mucocele of the appendix.
Br J Surg 1965;53
: 713-714
- Pickhardt PJ, Levy AD, Rohrman CA, Kende AI. Primary neoplasms of
the appendix: radiologic spectrum of disease with pathologic correlation.
RadioGraphics 2003;23
: 645-662[Abstract/Free Full Text]
- Abu Zidan FM, Al-Hilaly MA, Al-Atrabi N. Torsion of a mucocele of
the appendix in a pregnant woman. Acta Obstet Gynecol
Scand 1992; 71:140
-142[Medline]
- Legg NGM. Rare cases of intestinal obstruction: torsion
complicating mucocele of the appendix. J R Coll Surg
Edinb 1973; 18:236[Medline]
- Uroz-Tristan J, Garcia-Urgelles X, Poenaru D, Avila-Suarez R,
Valenciano-Fuentes B. Torsion of the vermiform appendix: value of
ultrasonographic findings. Eur J Pediatr Surg1998; 8:276
-277
- Paulson EK, Harris JP, Jaffe TA, Haugan PA, Nelson PC. Acute
appendicitis: added diagnostic value of coronal reformations from isotropic
voxels at multi-detector row CT. Radiology2005; 235:879
-885[Abstract/Free Full Text]
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
Top
Introduction
Case Report
