Diagnostic Ultrasound - Abdomen and Pelvis

Peritoneal Space Abscess
636
Diagnoses: Abdominal Wall/Peritoneal Cavity
Lymphocele
• History of lymph node dissection or vascular surgery,
adjacent to transplant kidneys
• Fluid collections along lymphatic drainage that may occur
lateral to bladder
• Usually anechoic but may be multilocular
Biloma
• History of biliary or hepatic surgery
• Perihepatic fluid collection commonly in gallbladder fossa
or Morison pouch
• Hypoechoic rounded collections or complex cystic
collections
Other Fluid Collections
• Pseudocyst: History and signs of pancreatitis, may be
complex with debris or hemorrhage, may be infected
• Hematoma: May be indistinguishable from abscess,
aspiration required to exclude infection
Necrotic Tumor/Peritoneal Carcinomatosis
• Known primary malignancy, not febrile; associated with
ascites, peritoneal nodularity, omental cake
Gossypiboma
• Gas- and fluid-containing collection around retained surgical
gauze or cotton with history of abdominal surgery
• May be asymptomatic or present with acute or subacute
infection
• Ultrasound: Heterogeneous; cystic with internal linear
echogenicity or solid with hypoechoic and bright echoes;
acoustic shadowing from gas, calcification, or fibrosis
• Characteristic radiopaque marker on radiography or CT,
variable surrounding "mass" with fluid or gas
Oxidized Cellulose Packing or Other Hemostatic
Agents
• History of surgery with use of such agents in preceding
month
• Highly reflective mass lesion with posterior reverberation
• May have associated hypoechoic rim of fluid
• Gas density on CT or radiography
PATHOLOGY
General Features
• Etiology
○ Postoperative (most common) or post traumatic
– Bowel anastomotic leak or bowel ischemia
– Dropped gall stones; late presentation with abscess or
fistula
○ Bowel perforation
– Appendicitis, diverticulitis, Crohn disease, peptic ulcer
○ Complication of pancreatitis
○ Extension from visceral abscess: Liver, spleen,
gallbladder, kidney, tubo-ovarian
○ Spontaneous bacterial peritonitis becoming loculated
○ CAPD with secondary infection
Staging, Grading, & Classification
• Organism: Bacterial, fungal, amebic
• Related to organ of origin (i.e., liver abscess)
• Intraperitoneal or extraperitoneal
• Communicating
○ Fistula to GI tract or biliary/pancreatic ducts
Gross Pathologic & Surgical Features
• Pus collection; often polymicrobial from enteric organisms
• Often confined by adherent omentum or bowel loops
• May or may not have peripheral fibrocapillary capsule
Microscopic Features
• Polymorphonuclear leukocytes (PMN) and white cell debris
• Bacteria, fungi, or parasites
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Fever, chills, abdominal pain, tachycardia, ↓ blood
pressure if septic
• Clinical profile
○ Leukocytosis, with blood/peritoneal cultures and ↑ ESR
Demographics
• Epidemiology
○ Most common in postoperative setting
○ Increases with age, diabetes, and immunocompromise
Natural History & Prognosis
• Variable depending on extent of abscess, patient immune
system status, and comorbidities, good prognosis when
small and confined
• May progress to sepsis, septic shock, septic inflammatory
response syndrome, and multiorgan failure
Treatment
• Dependent upon etiology, size of abscess, and patient
factors
• Broad spectrum antibiotics
• Percutaneous ultrasound or CT-guided drainage
• Surgical drainage and washout
DIAGNOSTIC CHECKLIST
Consider
• Iatrogenic hemostatic agents or dilated hypoperistaltic
bowel as mimic of gas-containing collection
• Other loculated fluid collections, such as pseudocyst,
biloma, hematoma
Image Interpretation Pearls
• Appropriate clinical context and aspiration of collection
required for diagnosis
SELECTED REFERENCES
1. Weledji EP et al: The challenge of intra-abdominal sepsis. Int J Surg.
11(4):290-5, 2013
2. Tirkes T et al: Peritoneal and retroperitoneal anatomy and its relevance for
cross-sectional imaging. Radiographics. 32(2):437-51, 2012
3. Manzella A et al: Imaging of gossypibomas: pictorial review. AJR Am J
Roentgenol. 193(6 Suppl):S94-101, 2009
4. Arnold AC et al: Postoperative Surgicel mimicking abscesses following
cholecystectomy and liver biopsy. Emerg Radiol. 15(3):183-5, 2008