Diagnostic Ultrasound - Abdomen and Pelvis

Peritoneal Space Abscess
Diagnoses: Abdominal Wall/Peritoneal Cavity
TERMINOLOGY
• Localized abdominal collection of pus
IMAGING
• Typical intraperitoneal spaces are cul-de-sac, Morison
pouch, and subphrenic spaces
• Complex fluid collection with internal low-level echoes,
membranes, or septations
• Bright linear echoes with reverberation artifacts
representing gas bubbles; highly suggestive of infection
• Dependent echoes representing debris may produce a
fluid-fluid level or gas may produce an air-fluid level
• Inflamed fat adjacent to abscess presents as echogenic
mass
• Hypervascular periphery, avascular center of abscess;
adjacent inflamed fat may be hyperemic
• Bedside US: For critically ill or postoperative patients, can
be effective screening tool to localize intraperitoneal
abscess or collections
KEY FACTS
• CECT: More sensitive for deeper, larger, or gas-containing
collections and as screening test
• CECT: Oral and IV contrast for best accuracy
TOP DIFFERENTIAL DIAGNOSES
• Loculated ascites
• Lymphocele
• Biloma
• Other fluid collections
• Necrotic tumor/peritoneal carcinomatosis
• Gossypiboma
• Oxidized cellulose packing or other hemostatic agents
CLINICAL ISSUES
• Most common in postoperative setting
• Increases with age, diabetes, and immunocompromised
patients
(Left) Graphic shows
preferential sites of peritoneal
collections in the abdomen
and pelvis. 1) Rectovesical or
rectouterine pouch; 2) Right
inframesocolic space; 3) Left
inframesocolic space; 4) Right
paracolic gutter. (Right)
Transverse ultrasound of the
midabdomen shows a large
complex fluid collection with
low-level echoes ſt and
irregular avascular mural
debris st. This was a chronic
abscess.
(Left) Transverse ultrasound of
the pelvis in a woman with
fever and pain after
gastrectomy for carcinoma is
shown. There is a huge abscess
st with a fluid-fluid level ſt.
This was successfully drained
percutaneously. (Right) CECT
of the same patient confirms
the extent of the abscess st,
but it does not show the fluidfluid
level.
634