AJR 2005; 184:1143-1149
© American Roentgen Ray Society
Helical CT Evaluation of Acute Right Lower Quadrant Pain: Part II, Uncommon Mimics of Appendicitis
Jinxing Yu,
Ann S. Fulcher,
Mary Ann Turner and
Robert A. Halvorsen
Department of Radiology, Virginia Commonwealth University, Medical
College of Virginia, 401 N 12th St., Third Floor, PO Box 980615, Richmond, VA
23298-0615.
Received July 22, 2004;
accepted after revision September 28, 2004.
Address correspondence to J. Yu.
Abstract
OBJECTIVE. The purpose of our pictorial essay is to highlight the
helical CT features of uncommon mimics of appendicitis and to provide clues to
differentiate them from appendicitis.
CONCLUSION. Uncommon mimics of appendicitis create a diagnostic
challenge in patients with right lower quadrant pain. Recognition of the
helical CT features of uncommon mimics of appendicitis is important in
clinical management and avoiding unnecessary laparotomy.
Introduction
Acute right lower quadrant (RLQ) pain is a common complaint
encountered in clinical practice. A broad spectrum of common and uncommon
entities may mimic acute appendicitis both clinically and on helical CT,
thereby creating a diagnostic challenge
[1-8].
Uncommon mimics include mucocele of the appendix, ovarian vein thrombosis,
ovarian dermoid, necrotic uterine leiomyoma, ovarian torsion, endometriosis,
ruptured ectopic pregnancy, typhlitis, sigmoid diverticulitis,
intussusception, pseudomembranous or cytomegalovirus (CMV) colitis, perforated
peptic ulcer, perforated cholecystitis, and pancreatitis. In this pictorial
essay, the helical CT features of these uncommon mimics along with the
features that aid in differentiating these entities from appendicitis will be
emphasized.
Mucocele of the Appendix
Mucocele of the appendix represents dilatation of the appendiceal lumen by
mucinous secretions [2]. The
obstructing lesions leading to mucocele formation include postappendicitis
scarring, most commonly, and fecaliths and appendiceal tumors. When a mucocele
ruptures, RLQ pain may be the only complaint. The helical CT features of a
ruptured mucocele may be similar to those of appendicitis and include a
dilated appendix (Fig. 1),
periappendiceal stranding, and fluid.
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Fig. 1. —23-year-old woman with right lower quadrant pain. Axial CT
scan shows dilatation of distal appendix (solid arrows) with normal
caliber of proximal appendix (open arrow). No periappendiceal fat
stranding is noted. Mucocele of appendix with early rupture was found
surgically.
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Ovarian Vein Thrombosis
Ovarian vein thrombosis is associated with childbirth, endometritis, pelvic
inflammatory disease, malignant tumors, and gynecologic surgery
[3]. The right ovarian vein is
involved in 90% of cases. At helical CT, thrombosis of the right ovarian vein
appears as a dilated tubular structure with central low attenuation extending
from the pelvis to the infrarenal inferior vena cava (Figs.
2A, and
2B). Although a thrombosed
ovarian vein may be confused with an abnormal appendix, the correct diagnosis
can be made by following the vein cephalad as it enters the inferior vena
cava.
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Fig. 2A. —47-year-old woman with fever and right lower quadrant pain.
Axial CT scan shows enlarged, nonenhancing, thrombosed right ovarian vein
(arrows) with fat stranding (open arrows) in right lower
quadrant adjacent to normal appendix (A).
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Ovarian Dermoid
Ovarian dermoid, or cystic teratoma, is the most common benign ovarian
tumor. Composed of all three germ cell layers, ovarian dermoids contain
variable amounts of fat, fluid, solid, and calcified elements. When
complicated by rupture, torsion, or hemorrhage, dermoids usually present with
acute lower quadrant pain. If rupture occurs, a fat-fluid level may be seen in
the peritoneal cavity and may be located in the pelvis, paracolic gutters,
Morison's pouch, or perihepatic space (Fig.
3).
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Fig. 3. —51-year-old woman with acute abdominal pain. Axial CT scan
shows large left adnexal mass that contains calcification and fat density
(open arrows). Fat-fluid level is seen in right anterior pelvis
(solid arrow). There is moderate amount of pelvic free fluid (F).
Surgery confirmed diagnosis of rupture of left ovarian dermoid.
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Necrotic Uterine Leiomyoma
Twenty to thirty percent of women older than 30 years harbor uterine
leiomyomata, which are usually asymptomatic. However, necrotic uterine
leiomyomata can present with acute lower abdominopelvic pain. CT findings
include a uterine mass with central low attenuation representing necrosis
(Figs. 4A, and
4B). Fat stranding adjacent to
the necrotic leiomyoma may be present.
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Fig. 4A. —41-year-old woman with acute right lower quadrant (RLQ) pain
and clinically suspected acute appendicitis. Axial CT scan shows large
necrotic leiomyoma (arrows) arising from right side of uterus (U).
Minimal fat stranding is noted in RLQ adjacent to leiomyoma.
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Fig. 4B. —41-year-old woman with acute right lower quadrant (RLQ) pain
and clinically suspected acute appendicitis. Axial CT scan obtained superior
to A shows tip of appendix filled with air (arrow) lateral to
inferior vena cava.
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Ovarian Torsion
Ovarian torsion represents twisting of the ovary pedicle resulting in
vascular compromise. The most common CT finding is an ovarian mass, which may
be cystic, solid, or complex, ranging from 4 to 10 cm. Often low-attenuation
structures comprise most of the ovary and represent enlarged follicles that
have become fluid-filled and engorged as the result of venous compromise. Fat
stranding associated with torsion may extend adjacent to the appendix and may
suggest appendicitis (Figs. 5A,
and 5B).
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Fig. 5A. —28-year-old woman with sudden-onset right lower quadrant
(RLQ) pain. Axial CT scan shows fat stranding (arrows) predominating
in RLQ posterior to cecum (C) and appendix (A) and heterogeneous mass in upper
pelvis representing enlarged ovary (O).
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Fig. 5B. —28-year-old woman with sudden-onset right lower quadrant
(RLQ) pain. Axial CT scan obtained inferior to A shows that torsed
ovary (O) contains cyst (asterisk). Fluid in RLQ (arrows) is
noted. Emergent surgery confirmed diagnosis of right ovarian torsion.
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Endometriosis
Endometriosis involving the intestinal tract may mimic a number of diseases
clinically and radiologically
[4]. The terminal ileum is a
relatively common site of endometrial implants; right lower quadrant pain may
be the initial complaint in these patients. On helical CT, endometriosis of
the terminal ileum produces wall thickening with fat stranding in the right
lower quadrant mimicking appendicitis (Figs.
6A, and
6B). Identification of the
normal appendix is the key in excluding appendicitis.
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Fig. 6B. —39-year-old woman with acute right lower quadrant pain. Axial
CT scan obtained inferior to A shows fat stranding (arrows)
medial to cecum (C). Mildly thickened terminal ileum (asterisk) is
identified lateral to uterus (U). On basis of CT findings, diagnosis of acute
appendicitis was raised, although appendix was not detected. Normal appendix
and endometriosis of terminal ileum were detected at surgery.
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Rupture of Ectopic Pregnancy
Ectopic pregnancy remains one of the leading causes of maternal death in
the United States [5]. An
adnexal mass with diffuse hemoperitoneum
(Fig. 7) may be seen at CT
when it ruptures. Although hemorrhagic infiltration of periappendiceal fat may
obscure the appendix and may suggest acute appendicitis, identification of
hemoperitoneum centered in the adnexa and correlation with serum ß-human
chorionic gonadotropin will establish the correct diagnosis.
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Fig. 7. —37-year-old woman with acute abdominal pain and clinical
suspicion of perforated appendicitis. Axial CT scan shows fluid collection in
right lower quadrant with attenuation of 77 H, consistent with blood
(arrows). High-attenuation foci (arrowheads) are located to
right of the uterus (U), indicative of active bleeding. Rupture of ectopic
pregnancy in right fallopian tube was confirmed surgically.
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Typhlitis
Typhlitis, or neutropenic colitis, is an inflammatory condition seen in
immunocompromised patients [6].
It affects the cecum and ascending colon and frequently presents with RLQ
pain. Helical CT features include segmental bowel wall thickening, pericolonic
fluid collection or fat stranding, pneumatosis coli, and intramural
low-attenuation regions indicative of edema or necrosis
(Fig. 8), which may be
confused with the reactive changes of appendicitis. However, the length of the
cecum involved by typhlitis is generally much greater than that associated
with appendicitis.
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Fig. 8. —74-year-old man with acute leukemia presenting with right
lower quadrant pain and fever. Axial CT scan shows findings of typhlitis with
marked circumferential thickening (double arrow) of cecal wall (C)
and pericecal fat stranding (arrows). Mildly thickened terminal ileum
is noted (asterisk).
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Sigmoid Colon Diverticulitis
Sigmoid colon diverticulitis is the most common cause of acute pain in the
left lower abdomen in older adults. Clinically, appendicitis may be suspected
when the diverticular inflammation is localized to a right-sided loop of the
sigmoid colon or if there is extensive sigmoid colon diverticulitis that
extends into the right lower quadrant
[7]. The appendix may be
secondarily affected if it is located within the area of inflammation.
Identification of a connection from the abscess to the inflamed diverticula
and a thickened sigmoid colon (Figs.
9A,
9B, and
9C) are features helpful in
establishing the diagnosis of sigmoid colon diverticulitis.
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Fig. 9A. —43-year-old woman with perforated sigmoid diverticulitis
extending into right lower quadrant (RLQ). Axial CT scan shows normal distal
appendix (solid arrow) and abscess (open arrow) lateral to
appendix.
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Fig. 9C. —43-year-old woman with perforated sigmoid diverticulitis
extending into right lower quadrant (RLQ). Delayed axial CT scan obtained
inferior to B shows thickened sigmoid colon (S) with fistula (open
arrows) that extends from sigmoid colon (S) to abscess, which contains
air and contrast material (solid arrows).
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Intussusception
Intussusception in adults may be associated with an underlying disease such
as neoplasia, celiac disease, or inverted Meckel's diverticulum. Helical CT
features include a layered appearance of varying densities including fat
inside the bowel lumen, proximal bowel obstruction
(Fig. 10), and sometimes a
mass corresponding to the pathologic lead point.
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Fig. 10. —40-year-old man with acute right lower quadrant pain. Axial
CT scan shows fat (asterisks) and soft-tissue mass (M) within loop of
right colon with thickened wall (open arrows). Fat stranding
(solid arrows) is noted surrounding this loop of bowel. Surgery
confirmed colocolic intussusception with bowel ischemia and found that lead
point was Burkitt lymphoma.
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Pseudomembranous Colitis and CMV Colitis in AIDS
Pseudomembranous colitis (Figs.
11A, and
11B) and CMV colitis
(Fig. 12) in AIDS patients
commonly present with fever, leukocytosis, diarrhea, and abdominal pain
mimicking appendicitis. The helical CT features include marked low-attenuation
thickening of the colonic wall due to edema. These colitides are often
pancolonic. However, involvement confined to the right colon is not unusual,
and when present in association with periappendiceal fat stranding, these
findings may mimic appendicitis.
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Fig. 11A. —68-year-old woman with abdominal pain and fever who was
treated with antibiotics for 2 weeks. Axial CT scan shows thickened right and
left colon (open arrows) consistent with pseudomembranous colitis in
this clinical setting. Slightly enlarged appendix with mild wall enhancement
and periappendiceal stranding is noted (solid arrows). Coincident
acute appendicitis cannot be excluded on basis of imaging findings.
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Fig. 11B. —68-year-old woman with abdominal pain and fever who was
treated with antibiotics for 2 weeks. Repeat axial CT scan obtained 2 days
after A shows appendix filled with oral contrast material (solid
arrows). Diagnosis of appendicitis is excluded, although medial aspect of
appendix wall is thickened (arrowhead), which is result of adjacent
inflammation. Open arrows indicate thickened right and left colon.
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Perforated Peptic Ulcer, Perforated Cholecystitis, and Pancreatitis
In some patients with perforated peptic ulcer (Figs.
13A, and
13B), perforated cholecystitis
(Figs. 14A, and
14B), or pancreatitis (Figs.
15A, and
15B), the clinical symptoms
are similar to those of appendicitis because the gastric contents, bile, and
pancreatic secretions descend along the paracolic gutter into the RLQ and
cause chemical periappendicitis
[8]. A false-positive diagnosis
of appendicitis may be made. In these conditions associated with fat stranding
in the RLQ, the normal appearance of appendix helps to exclude
appendicitis.
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Fig. 13B. —37-year-old man with perforation of peptic ulcer in duodenal
bulb. Axial CT scan obtained superior to A shows oral contrast material
extravasation in perihepatic space (arrows), which leaked from
perforated duodenum (D).
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Fig. 14B. —55-year-old woman with right lower quadrant pain. Axial CT
scan obtained superior to A shows gas (arrowheads) and fat
stranding (arrows) surrounding gallbladder (GB), consistent with
emphysematous cholecystitis with perforation.
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References
- Macari M, Balthazar EJ. The acute right lower quadrant: CT
evaluation. Radiol Clin North Am2003; 41:1117
-1136[Medline]
- Madwed D, Mindelzun R, Jeffrey RB Jr. Mucocele of the appendix:
imaging findings. AJR1992; 159:69
-72[Abstract/Free Full Text]
- Jain KA, Jeffrey RB Jr. Gonadal vein thrombosis in patients with
acute gastrointestinal inflammation: diagnosis with CT.
Radiology1991; 180:111
-113[Abstract/Free Full Text]
- Buy JN, Ghossain MA, Moss AA, et al. Cystic teratoma of the ovary:
CT detection. Radiology1989; 171:697
-701[Abstract/Free Full Text]
- Yantiss RK, Clement PB, Young RH. Endometriosis of the intestinal
tract: a study of 44 cases of a disease that may cause diverse challenges in
clinical and pathologic evaluation. Am J Surg Pathol2001; 25:445
-454[Medline]
- Birnbaum BA, Jeffrey RB Jr. CT and sonographic evaluation of acute
right lower quadrant abdominal pain. AJR1998; 170:361
-371[Free Full Text]
- Ripolles T, Concepcion L, Martinez-Perez MJ, Morote V. Appendicular
involvement in perforated sigmoid disease: US and CT findings. Eur
Radiol 1999;9:697
-700[Medline]
- Ripolles T, Martinez-Perez MJ, Morote V, Solaz J. Diseases that
simulate acute appendicitis on ultrasound. Br J Radiol1998; 71:94
-98[Abstract]
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Abstract
Introduction
