Diagnostic Ultrasound - Abdomen and Pelvis

Cystic Peritoneal Mass
Differential Diagnoses:
Abdominal Wall/Peritoneal Cavity
DIFFERENTIAL DIAGNOSIS
Common
• Abscess
• Organizing Hematoma
• Complicated Ascites
• Pancreatic Pseudocyst
• Cystic Ovarian Masses
Less Common
• Paraovarian/Paratubal Cyst
• Localized Collections
○ Biloma, Urinoma, CSF Pseudocyst
• Pedunculated Cyst/Diverticula
• Peritoneal Inclusion Cyst
• Cystic Non Ovarian Malignant Neoplasm
○ Cystic Metastasis
○ Pseudomyxoma Peritonei
○ Pedunculated Cystic Tumor
– Gastrointestinal Stromal Tumor (GIST)
– Cystic Leiomyosarcoma
– Pancreatic Mucinous
Cystadenoma/Cystadenocarcinoma
○ Cystic Mesenchymal Tumor
– Malignant Fibrous Histiocytoma
– Synovial Sarcoma
• Cystic Benign Neoplasm
○ Mesenteric Teratoma
○ Multicystic Mesothelioma
• Cystic Lymph Nodes
Rare but Important
• Mesenteric/Omental Cyst
○ Lymphangioma
○ Nonpancreatic Pseudocyst
○ Enteric Duplication Cyst
○ Enteric Cyst
○ Mesothelial Cyst
• Urachal Cyst/Abscess
• Infarcted Accessory Spleen
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
• Lesions with relevant history
○ Abscess, organizing hematoma
• Lesions with characteristic appearances
○ Peritoneal inclusion cyst, pseudomyxoma peritonei,
mature teratoma (dermoid), enteric duplication cyst
• Lesions with thin-walled cystic appearance unless
complicated
○ Mesenteric/omental cysts
○ Pedunculated cyst from adjacent organs
• Lesions with complicated appearance
○ Any cystic neoplasm mentioned above or cystic lesion
with complication (infection/hemorrhage)
○ Bowel wall origin suggests GIST
○ Other lesions nonspecific, need clinical information to
make specific diagnosis and biopsy/aspiration to confirm
Helpful Clues for Common Diagnoses
• Abscess
○ Pyogenic
– Unilocular/multiloculated; thin-/thick-walled plus
debris-fluid level
– Echogenic foci with "ring-down" artifacts/"dirty"
shadow = gas
□ Consider infection with gas forming organism or
bowel leak
– Occasionally, surgical hemostatic agents (cellulose)
will mimic gas-containing collection, surgical history is
key
○ Tuberculous
– With features of TB peritonitis or GI/renal/mesenteric
lymph node involvement
○ Parasitic
– Hydatid disease: 12% affects peritoneum
– Variable appearance ranging from heterogeneous
solid-looking mass to complex cystic mass
• Organizing Hematoma
○ History of trauma, coagulopathy, or anticoagulant
therapy
○ Organization with liquefaction in subacute to chronic
stage
○ Localized collection with multiple thick septa horizontally
aligned ± layering debris
○ May be difficult to determine origin with ultrasound
• Complicated Ascites
○ Infection, hemorrhage, inflammation
○ Septations and loculation develop over time
– Multiple, thick, irregular septa in chronic cases
• Cystic Ovarian Masses
○ Benign and malignant cystic neoplasms
○ Mucinous and serous cystadenoma and
cystadenocarcinoma
○ Mature cystic teratoma
○ Variable appearances depending on pathology
Helpful Clues for Less Common Diagnoses
• Paraovarian/Paratubal Cyst
○ Typically small and simple, separate from ovary
• Localized Collections
○ Urinomas, lymphoceles, bilomas
○ CSF pseudocyst associated with ventriculoperitoneal
shunt, due to inflammation or infection
– Cysts are close to shunt tip and contain tubing
• Pedunculated Cyst/Diverticula
○ Hepatic, splenic, renal cyst, or GI diverticula
○ Origin may be difficult to trace
○ May cause abdominal pain and palpable mass if
hemorrhagic or infected
• Peritoneal Inclusion Cyst
○ Fluid conforming to peritoneal cavity with internal septa
producing multilocular lesion
○ Low-resistance flow sometimes present in septa from
vessels in mesothelial lining
○ May appear complicated if containing
debris/hemorrhage
○ Loculated fluid may surround normal ipsilateral ovary
and produce characteristic "spider in web" appearance
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