Diagnostic Ultrasound - Abdomen and Pelvis

Appendiceal Mucocele
TERMINOLOGY
Definitions
• Distension of appendiceal lumen as result of mucin
accumulation
○ Macroscopic description and not pathologic diagnosis
IMAGING
General Features
• Best diagnostic clue
○ Distended tubular, round or pear-shaped cystic
intraperitoneal structure in right lower quadrant traced
from cecal pole
○ Presence of calcification in wall strongly supports
diagnosis
• Location
○ Right lower quadrant of abdomen
• Size
○ Transverse diameter: 1.5-7.0 cm
– Giant mucoceles can grow up to 25 cm in size
• Morphology
○ Tubular, round or pear-shaped cystic structure
Ultrasonographic Findings
• Grayscale ultrasound
○ Cystic tubular or pear-shaped structure
– ± acoustic shadowing from mural calcification
○ Intraluminal contents can have a variable appearance
– Typically low-level echoes
– Sometimes concentric layering of dense mucoid
material producing onion skin appearance
○ Transvaginal pelvic ultrasound improves image quality
and helps to differentiate from ovarian cystic masses in
women with pelvic appendiceal mucoceles
○ Soft tissue thickening and irregularity of mucocele wall
suggest malignancy
○ Fecalith or appendicolith may be visible in obstructive
type (simple mucocele)
○ Echogenic surrounding inflamed fat seen in acute
obstructive type and in inflamed or perforated
appendicular mucoceles
CT Findings
• CECT
○ Cystic tubular, round or pear-shaped, well-encapsulated
mass with base indistinguishable from appendicular base
○ Central homogeneous low attenuation (15-25 HU) with
peripheral enhancing wall
○ Wall calcification seen in < 50% of cases
– Calcification can be punctate or curvilinear
○ Atypical features reflect secondary complication, such as
infection/perforation, malignancy, or unusual underlying
pathology
– Soft tissue thickening and irregularity of wall
– Soft tissue stranding in surrounding fat
○ Intraluminal gas bubbles or air-fluid level within
mucocele are indicative of super added infection
○ Myxoglobulosis is rare mucocele variant where there are
multiple intraluminal, small, pearly filling defects, which
may be visible on CT if calcified
○ Intussusception into colon is rare complication of
appendiceal mucocele
– Cystic leading point may be visible
○ Dense calcific appendicolith or fecalith may be visible in
simple obstructive form of appendiceal mucocele
• CTC
○ On 3D endoluminal view mucoceles cause smooth
impression in medial aspect of cecal pole, suggesting
extramucosal or extrinsic compression
– Similar appearance also noted at endoscopy
MR Findings
• T1WI
○ Cystic structure with base indistinguishable from
appendix
○ Contents homogeneous and hypo- or isointense
○ Wall calcification less apparent
• T2WI
○ Contents homogeneous and hyperintense
• T1WI C+
○ Enhancing wall
○ Centrally homogeneous and hypo- or isointense
Imaging Recommendations
• Best imaging tool
○ Contrast-enhanced CT scan
– Relationship of cystic mass and cecum is easily
identified, especially with multiplanar reformations
– More sensitive in detecting wall calcification
• Protocol advice
○ Contrast-enhanced CT of abdomen and pelvis
– Oral contrast optional
DIFFERENTIAL DIAGNOSIS
Cystic Ovarian Neoplasm
• Appendicular mucoceles are intraperitoneal and can mimic
cystic ovarian and tubal masses in females
○ Appendix identified separately
○ Right gonadal vessels traced to cystic mass
Hydrosalpinx
• Tubular structure traced to uterine cornu with narrow
medial and wide distal ends
• Hydrosalpinx has partial folds and small mural nodules
producing characteristic 'cogwheel' appearance
• Appendix identified separately
Tubo-Ovarian Abscess
• Usually bilateral
• Multilocular thick-walled collections with internal debris
and peripheral hyperemia
• Clinical signs and symptoms of infection
Duplication Cyst
• Thin walled with all 3 layers of the bowel wall (gut
signature), sometimes visible on trans abdominal
ultrasound
• May or may not be adjacent to bowel
Appendiceal Obstruction From Appendiceal
Carcinoma/Cecal Carcinoma
• Distended appendix
Diagnoses: Bowel
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