Diagnostic Ultrasound - Abdomen and Pelvis

Large Bowel Malignancy
Diagnoses: Bowel
• Multisegmental involvement in Crohn disease
Colonic Lymphoma
• Hypoechoic/anechoic; single or multifocal
• Typically circumferential with destruction of gut signature
• Transition from tumor to normal bowel is gradual
• Dilatation of lumen
• Bulky mesenteric/retroperitoneal nodes
Gastrointestinal Stromal Tumors
• Rare in large bowel
• Rounded mural mass; exophytic or project into lumen
• Large central necrotic cavity may communicate with lumen
• No lymph node enlargement
Intussusception
• "Bowel-within-bowel" appearance
• Eccentrically placed crescentic echogenicity representing
intussuscepted mesentery
Infectious Colitis
• Longer segment of involvement
• Accordion sign in Clostridium difficile colitis may be seen on
CT or US
Colonic Ischemia
• Can demonstrate hypoechoic segmental bowel thickening,
mimicking colon cancer
• Location: Watershed regions, splenic flexure; rectal sparing
• Color Doppler may demonstrate absence of arterial flow
• Pneumatosis or portal venous gas
PATHOLOGY
General Features
• Etiology
○ Adenoma-carcinoma sequence: Benign adenoma
progressing to malignant transformation
○ Risk factors
– Colonic polyps
– Family history of colorectal cancer (CRC)
– Inflammatory bowel disease
– Diet: High fat, low roughage, high alcohol
– Inherited conditions: Familial adenomatous polyposis
(FAP) and hereditary nonpolyposis colon cancer
(HNPCC) account for 5% of CRCs
Staging, Grading, & Classification
• AJCC TNM stage
• Modified Astler Collier staging (MAC)
○ Original MAC was based on the modified Dukes
classification
• Original Dukes classification
○ A: Tumor limited to bowel wall
○ B: Tumor extending through bowel wall
○ C: Nodal metastasis
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Hematochezia, altered bowel habit, weight loss,
tenesmus, abdominal pain (from bowel obstruction or
perforation)
• Other signs/symptoms
○ Asymptomatic and detected through screening
programs.
Demographics
• Epidemiology
○ 2nd and 3rd most common cancers in Europe and United
States, respectively (Europe: 183,000; USA: 79,000 new
cases per year)
Natural History & Prognosis
• 5-year survival: 50-60%.
• 30-50% of patients either present with or develop distant
metastases in liver &/or lungs
Treatment
• Surgery
○ 85% of patients undergo resection with curative intent
• Chemotherapy
• Radiotherapy
DIAGNOSTIC CHECKLIST
Consider
• Colonic carcinoma in differential of short segment bowel
wall thickening
Image Interpretation Pearls
• Short segment thickening
• Asymmetric thickening
• Loss of gut signature
• Extramural tumor extension
• Local lymph nodes
Reporting Tips
• Recommend colonoscopy for histologic confirmation
• Recommend CECT for confirmation and complete staging
when US suspicious for colonic cancer
• EUS &/or MR for locoregional staging of rectal cancer
SELECTED REFERENCES
1. Shibasaki S et al: Use of transabdominal ultrasonography to preoperatively
determine T-stage of proven colon cancers. Abdom Imaging. ePub, 2014
2. Martínez-Ares D et al: Ultrasonography is an accurate technique for the
diagnosis of gastrointestinal tumors in patients without localizing
symptoms. Rev Esp Enferm Dig. 101(11):773-86, 2009
3. Smith NJ et al: Preoperative computed tomography staging of
nonmetastatic colon cancer predicts outcome: implications for clinical trials.
Br J Cancer. 96(7):1030-6, 2007
4. O'Malley ME et al: US of gastrointestinal tract abnormalities with CT
correlation. Radiographics. 23(1):59-72, 2003
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