Gas content within the bowel lumen makes the visibility difficult (Table 41.1).
High-frequency linear probe is used.
Normal gut is compressible by probe. Abnormally thickened gut is noncompressible.
Graded compression is used in acute appendicitis. Slow-graded compression moves the bowel loops out of the way without any discomfort to the patient.
1. Free intraperitoneal gas—Difficult to detect on USG
• Echogenic peritoneal stripe
• Air (ring down artifacts) b/w the abdominal wall and the liver
2. Loculated fluid collection—Aperistaltic collection with varying echogenicity
3. Mesenteric lymphadenopathy—Focal discrete hypoechoic masses of varying size. Loss of echogenic hilum
4. Edematous bowel loops
5. Wall thickening—Normal gut wall—3 millimeters if distended and 5 millimeters if collapsed
6. Loss of normal gut signature
Usually benign lesions involve long segment with concentric thickening and wall layer preservation.
Malignant lesions involve short segment with eccentric disease and wall layer destruction.
Normal appendix is compressible with <3 millimeters wall thickness. Graded compression technique (Puylaert) is required.
Presentation—RLQ pain, high WBC count
• Blind ended, noncompressible, and aperistaltic tube with diameter >6 millimeters arising from the base of cecum
• Inflamed perienteric fat
• Pericecal collections
• Hyperemia of wall
Appendiceal perforation may occur leading to loculated pericecal collection, loss of wall layers (Figure 41.1).
Mucocele of appendix—Large hypoechoic well-defined RLQ cystic lesion with variable internal echoes.