Diagnostic Ultrasound - Abdomen and Pelvis

Peritoneal Carcinomatosis
TERMINOLOGY
Definitions
• Peritoneal spread of tumor from epithelial malignancy
resulting in peritoneal thickening, omental infiltration,
serosal implants, and ascites
• Krukenberg tumor: Bilateral ovarian metastases from
hematogenous or lymphatic spread from signet ring gastric
carcinoma (less commonly breast)
IMAGING
General Features
• Best diagnostic clue
○ Omental cake
○ Cystic or solid peritoneal masses or peritoneal thickening
○ Ascites, mesenteric infiltration
• Location
○ Implants develop where peritoneal fluid collects: Dome
of liver, omentum, paracolic gutters, and pelvic recesses
○ Dissemination of tumor also occurs via hematogenous,
contiguous, or lymphatic spread
– To peritoneum, adjacent organs, and mesentery
• Size
○ Variable: Tiny nodules to large confluent omental or
peritoneal masses
• Morphology
○ Omental involvement may be nodular or diffuse,
producing an omental cake
○ Peritoneal masses may be solid, cystic, or mixed,
depending on primary neoplasm
Ultrasonographic Findings
• Grayscale ultrasound
○ Omentum: Thickened and hypoechoic or heterogeneous
with preserved islands of echogenic fat
○ Peritoneum
– Hypoechoic rind-like thickening of peritoneum
– Discrete implants: Irregular nodular masses along
parietal and visceral peritoneum
□ Usually grow inward towards peritoneal cavity; may
grow outwards and invade abdominal wall
□ Pouch of Douglas, Morison pouch, and right
subphrenic space commonly involved
– Psammomatous calcification in peritoneal implants
seen in ovarian serous carcinoma (up to 40% with
stage III/IV disease)
○ Ascites: Complex with septations or internal echoes
(jiggle with transducer pressure)
– May be only finding early on
– Improves conspicuity of peritoneal implants, which
may not be detectable when small
○ Thickening of mesenteric leaves due to desmoplastic
reaction; typically mesenteric side of terminal ileum
– May give "sunburst" appearance
○ ± enlarged hypoechoic retroperitoneal and mesenteric
lymph nodes (more common in lymphomatosis)
○ Primary neoplasm may be evident, e.g., ovarian,
appendiceal, pancreatic, or GI malignancies
• Color Doppler
○ Confirms that omental/peritoneal deposits are solid;
improves biopsy yield when viable tumor is targeted
Nuclear Medicine Findings
• FDG PET/CT: Increased metabolic activity in masses or along
neoplastic peritoneum, most useful in lymphoma
CT Findings
• Ascites, stranding of peritoneal fat, nodular or diffuse
thickening of peritoneum with enhancement
• Omental cake or omental nodules, streaky increased
density of omentum
• Infiltrated or spiculated mesentery or mass
• Thick, fixed bowel wall ± bowel obstruction
MR Findings
• T1WI
○ Low signal ascites; medium signal omental cake, nodules,
and masses
• T2WI
○ Intermediate signal peritoneal mass, nodule, or omental
cake with high signal ascites
• DWI
○ Tumors may variably restrict diffusion depending on
primary neoplasm and presence of necrosis
• T1WI C+
○ Abnormal linear or nodular hyperenhancement of
peritoneum
○ Variable enhancement of nodules and masses
Nonvascular Interventions
• US-guided diagnostic and therapeutic aspiration of
peritoneal fluid
• US-guided fine-needle or core biopsy of omental cake or
peritoneal masses
Imaging Recommendations
• Best imaging tool
○ CECT: Superior for cancer staging
• Protocol advice
○ Optimum CECT requires oral and intravenous contrast,
CEMR is alternative
○ US ideal for guiding diagnostic and therapeutic
aspiration or tissue biopsy
○ US may follow CT/MR for detailed search of primary
tumor involving ovaries, gallbladder, and bile ducts
DIFFERENTIAL DIAGNOSIS
Pseudomyxoma Peritonei
• Secondary to neoplasm, secreting mucin most commonly
appendiceal, or ovarian primary neoplasm
• Low-density loculated complex ascites exerting mass effect
reflecting gelatinous peritoneal fluid
○ Curvilinear surface calcification highly suggestive
• Scalloping of lateral contour of liver and spleen
• Peritoneal nodules, omental invasion
Peritoneal Mesothelioma
• 25% of mesotheliomas are peritoneal; most common in
middle-aged males; associated with asbestos exposure
Diagnoses: Abdominal Wall/Peritoneal Cavity
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