Cobblestoning describes a characteristic ultrasonographic pattern of subcutaneous tissue in which multiple hypoechoic (fluid-filled) or hyperechoic (edematous) septations and fat lobules create a surface that resembles cobblestones. It is a nonspecific sign that indicates interstitial fluid, inflammation, or edema within the subcutaneous fat planes.
Sonographic Features
- Heterogeneous subcutaneous fat with multiple rounded hypoechoic areas separated by echogenic fibrous septa.
- Increased thickness of the subcutaneous layer compared with the contralateral side or normative values.
- Altered echotexture: loss of normal uniform fat echogenicity and increased fluid tracking along septa.
- Dynamic appearance may change with probe compression or patient position; Doppler may show increased vascularity if inflammation is present.
Common Sites
- Lower limbs — anterior/posterior shins and calves (cellulitis, lymphedema).
- Periorbital and facial subcutaneous tissues (inflammatory/edematous states).
- Abdominal wall and groin (postoperative edema, cellulitis).
- Breast and axillary fat in mastitis or post-procedural changes.
Sites of Cobblestoning
1. Subcutaneous Tissue
Cellulitis
Traumatic edema
Soft tissue infections
2. Skin & Breast
Mastitis
Breast cellulitis
Chronic dermatitis / panniculitis
3. Gastrointestinal Tract
Cobblestoning mucosa in Crohn’s disease (small bowel, colon)
Chronic inflammatory enteritis
4. Oropharynx & Upper Airway
Posterior pharyngeal wall (chronic postnasal drip, pharyngitis, allergic rhinitis)
Tonsillar region / lymphoid hypertrophy
5. Head & Neck Soft Tissues
Angioedema (facial / airway soft tissue)
Cervical cellulitis
6. Extremities
Lymphedema
Subcutaneous edema after trauma/infection
7. Other Soft Tissue Planes
Post-radiation tissue edema
Inflammatory panniculitis
Differential Diagnosis
- Cellulitis — cobblestoning with increased skin/subcutaneous thickness and hyperemia on color Doppler.
- Lymphedema — diffuse cobblestoning often bilateral and chronic, may show thickened septa without marked hyperemia.
- Necrotizing fasciitis — may show cobblestoning early, but look for fascial plane fluid, gas (hyperechoic foci with shadowing), and lack of perfusion.
- Traumatic fat stranding and contusion — history of injury and focal distribution.
- Postoperative/Postsurgical edema — localized cobblestoning adjacent to surgical sites or drains.
Cobblestoning — Related Pathologies
- Bacterial cellulitis — acute infection causing interstitial edema and hyperemia; responds to antibiotics.
- Lymphedema — chronic lymphatic insufficiency with persistent subcutaneous thickening and septal fibrosis.
- Venous stasis/edema — commonly in the lower legs with dependent pitting edema and skin changes.
- Inflammatory panniculitis (e.g., erythema nodosum) — may show nodular subcutaneous changes with variable vascularity.
- Early necrotizing soft-tissue infection — requires urgent assessment; cobblestoning alone is not diagnostic but should prompt evaluation for deeper fluid, gas, and systemic signs.
• Hypoechoic fluid (edema, pus) interspersed with hyperechoic fat lobules gives a cobblestone pattern.
• Helps differentiate cellulitis from a discrete abscess.
2. Allergic Reactions (Angioedema)
• Edematous hypoechoic areas between subcutaneous fat septae form cobblestoning.
• Often associated with airway/face swelling.
3. Inflammatory Bowel Disease (Crohn’s Disease)
• Due to deep longitudinal and transverse ulcerations with edematous mucosa between them.
4. Lymphoid Hypertrophy in Oropharynx
• Cobblestoning indicates chronic postnasal drip, allergic rhinitis, or pharyngitis.
5. Chronic Lymphedema
6. Breast / Soft Tissue Infections
7. Dermatological Disorders
- Compare with the contralateral side and correlate with clinical signs (erythema, warmth, pain, fever).
- Use compression and color Doppler: increased blood flow supports cellulitis; absence of flow with deep fluid collections raises concern for necrotizing infection.
- When in doubt, document and recommend clinical correlation or repeat imaging — ultrasound is excellent for superficial assessment but limited for deep fascial evaluation.
