What are the primary radiological signs to look for in a Contrast-Enhanced Computed Tomography (CECT) abdomen scan?

Primary Radiological Signs in CECT Abdomen

The most important radiological signs to look for in a Contrast-Enhanced Computed Tomography (CECT) abdomen scan include organ-specific abnormalities, enhancement patterns, and structural changes that indicate pathology across abdominal organs and systems. 1

Systematic Approach to CECT Abdomen Interpretation

Technical Parameters

• Optimal slice thickness of 3mm for adequate spatial resolution 1
• Proper contrast administration protocol with appropriate timing of arterial, portal venous, and delayed phases 1
• Adequate bowel preparation and insufflation to avoid misinterpretation 1

Liver Assessment

• Focal lesions with specific enhancement patterns during arterial, portal venous, and delayed phases 1
• Multiphase contrast-enhanced CT has 91-95% accuracy for hemangiomas and 85-93% accuracy for focal nodular hyperplasia 1
• Abnormal density, contour irregularities, and parenchymal changes 1

Pancreatic Evaluation

• Pancreatic necrosis (visible after 72 hours from onset of symptoms) 2
• Peripancreatic fluid collections and inflammation 2
• CT Severity Index (CTSI) for pancreatitis grading based on:
  • Pancreatic inflammation/enlargement
  • Peripancreatic fluid collections
  • Extent of necrosis (>50% necrosis associated with intra-abdominal hypertension) 3

Bowel Assessment

• Wall thickness (>4mm considered abnormal) 2
• Enhancement patterns (mucosal, submucosal, serosal) 2
• Surrounding fat stranding and inflammation 2
• Pneumoperitoneum indicating perforation 1
• Round belly sign (RBS) - predictor of intra-abdominal hypertension in acute pancreatitis 3

Appendix Evaluation

• Normal appendix diameter <6mm with no wall thickening 1
• Optimal cutoff for maximum outer diameter is 8.2mm (sensitivity 88.8%, specificity 93.4%) 1
• Periappendiceal fat stranding and fluid collections 4
• CECT has sensitivity of 92% and specificity of 85% for appendicitis in equivocal cases 4

Vascular Structure Assessment

• Aorta and major branches for aneurysms, dissection, or stenosis 1
• Portal venous system for thrombosis or varices 1
• Active extravasation of contrast in cases of GI bleeding 2
• Abnormal enhancement of bowel walls suggesting ischemia 1

Fluid Collections and Ascites

• Presence, location, and density of fluid collections 2
• Moderate-gross ascites (associated with intra-abdominal hypertension) 3
• Abscess formation (hypodense center with rim enhancement) 2

Small Bowel Specific Signs

• Distension patterns (best visualized with neutral oral contrast) 2, 5
• Mural thickening and enhancement patterns 2
• Congregated small bowel loops (as in abdominal cocoon) 6
• Fistulous tracts and strictures 2

Phase-Specific Findings

Arterial Phase

• Hypervascular lesions (neuroendocrine tumors, hypervascular metastases) 1
• Active bleeding (extravasation of contrast) 2
• Arterial abnormalities (stenosis, aneurysms) 1

Portal Venous Phase

• Most abdominal pathologies are best visualized 1
• Optimal for parenchymal organ assessment 1
• Venous thrombosis detection 1

Delayed Phase

• Useful for characterizing certain liver lesions 1
• Urinary tract evaluation 1
• Fibrotic lesions that show progressive enhancement 1

Common Pitfalls and Caveats

• Inadequate bowel distension may obscure or mimic mucosal abnormalities 2
• Hyperintense bowel contents may obscure subtle masses or vascular abnormalities 2
• Cone-beam artifacts can limit visualization 2
• Neutral oral contrast may dilute contrast extravasation, making active bleeding harder to identify 2
• Post-contrast acute kidney injury concerns, though recent meta-analyses show limited association 2

By systematically evaluating these radiological signs in CECT abdomen scans, clinicians can accurately diagnose various abdominal pathologies and guide appropriate management decisions.