Graded-Compression Appendix Ultrasound

Graded-compression ultrasound is a first-line, radiation-free test for suspected acute appendicitis, particularly in children, adolescents, thin adults and pregnant patients. Gentle progressive transducer pressure displaces overlying gas-filled bowel to reveal the appendix. A blind-ending, non-compressible tubular structure with an outer diameter of 6 mm or more is the principal diagnostic criterion.

Indications

Suspected acute appendicitis with right iliac fossa pain
Children and adolescents in whom ionising radiation is best avoided
Pregnant patients with right-sided abdominal pain
Thin adults and equivocal clinical presentations
Follow-up of a treated appendiceal mass or abscess

Contraindications & Cautions

No absolute contraindications; ultrasound is safe and non-ionising
Marked obesity, extensive bowel gas and guarding limit visualisation and compression
A retrocaecal or pelvic appendix may be difficult or impossible to identify
A non-visualised appendix does not exclude appendicitis; consider MRI (pregnancy/children) or CT (adults)

Patient Preparation

No specific preparation required; the patient can indicate the point of maximal tenderness
Supine position, sometimes with left lateral decubitus to access a retrocaecal appendix
Begin scanning at the site the patient localises as most painful
Apply gentle, progressively increasing (graded) compression to displace bowel gas
Explain that mild pressure discomfort is expected

Technique & Parameters

High-frequency linear 7-15 MHz probe; switch to curvilinear 3-6 MHz for deep or retrocaecal appendix or larger patients
Identify the ascending colon and follow the caecum to the appendiceal base
Trace the blind-ending, non-peristaltic tubular structure to its tip in transverse and longitudinal planes
Apply graded compression to displace gas and assess compressibility
Measure the maximal outer-to-outer diameter perpendicular to the long axis
Add colour Doppler to demonstrate mural hyperaemia and survey for secondary signs

Systematic Review

Identify the appendix as a blind-ending, non-peristaltic, gut-signature tubular structure from the caecal base
Measure the maximal outer diameter and assess compressibility
Assess wall thickness, layering and mural hyperaemia on Doppler
Look for an appendicolith with posterior acoustic shadowing
Evaluate periappendiceal echogenic fat, free/loculated fluid and phlegmon or abscess
Consider alternative diagnoses in the right iliac fossa and pelvis

Key Findings & Significance

Non-compressible, blind-ending tubular structure with outer diameter >=6 mm is the primary criterion for appendicitis
Aperistaltic appendix with wall thickening and mural hyperaemia on colour Doppler
Appendicolith with posterior shadowing, often associated with complicated appendicitis
Periappendiceal inflamed echogenic fat and free fluid as secondary signs
Loss of wall layering, loculated fluid or a phlegmon/abscess indicates perforation
A fully compressible appendix under 6 mm with no secondary signs argues against appendicitis

Differential Considerations

Right iliac fossa pain: appendicitis vs mesenteric adenitis vs terminal ileitis (Crohn/infective) vs typhlitis
Gynaecological: ovarian torsion, ruptured cyst, ectopic pregnancy, tubo-ovarian abscess
Urological: ureteric colic, pyelonephritis
Appendiceal diameter 6-7 mm borderline: early appendicitis vs normal variant; use secondary signs and re-evaluation
Right-sided diverticulitis and epiploic appendagitis

Pearls & Pitfalls

Scan directly over the point of maximal tenderness; the sonographic Murphy sign supports the diagnosis
Graded compression is key: gentle progressive pressure displaces gas and tests compressibility
A diameter of 6-7 mm is borderline; weight secondary signs (hyperaemia, fat, fluid) and consider short-interval re-scan
A non-visualised appendix is non-diagnostic, not negative; escalate to MRI (pregnancy/children) or CT as appropriate
Always look for an alternative cause, especially gynaecological pathology in women

Structured Report

State transducer, technique and whether the appendix was visualised in full
Report maximal outer diameter, compressibility, wall changes and mural hyperaemia
Note appendicolith, periappendiceal fat, fluid and any phlegmon or abscess
Describe relevant alternative diagnoses when the appendix is normal or not seen
Give an impression (positive, negative or equivocal) and recommend further imaging when non-diagnostic

References

ACR Appropriateness Criteria: Right Lower Quadrant Pain - Suspected Appendicitis
Puylaert JB. Acute Appendicitis: US Evaluation Using Graded Compression. Radiology 1986
AIUM Practice Parameter for the Performance of an Ultrasound Examination of the Abdomen
Trout AT et al. Sonographic Diagnosis of Appendicitis in Children. Radiographics

Educational clinical decision support only. Protocols vary by institution and equipment; always confirm with a qualified radiologist and local guidelines before clinical use.

Graded-Compression Appendix Ultrasound

📋 Indications

⛔ Contraindications & Cautions

🧑‍⚕️ Patient Preparation

⚙️ Technique & Parameters

🔎 Systematic Review

🩻 Key Findings & Significance

🧠 Differential Considerations

💡 Pearls & Pitfalls

📝 Structured Report

📚 References