Foreign Body and Injection Granuloma

KEY FACTS

Terminology

• Foreign body (FB): Retention of penetrating or iatrogenic object within tissues
• Injection granuloma (IG): Localized tissue reaction to material injected into tissues

Imaging

• US: Modality of choice to detect radiolucent FBs and diagnose IGs
• FB : Nearly 100% are detectable on US

Reflectivity of some objects (wood, metal, glass, plastic) exceeds that of others (bamboo)

Align probe as parallel to FB as possible; FB may be located some distance from entry wound

Echogenic FB ± posterior artifact (reverberation/comet-tail artifact or posterior shadowing)

± hypoechoic rim of edematous inflammatory tissue, granulation tissue, or fibrosis

False-positive US with gas or calcification in soft tissues; correlate with radiographs if necessary

Repeat US in 2-10 days if clinical history is suspicious and US findings negative or equivocal

– Bamboo splints may not be visible initially
• IG : Focal, hypoechoic subcutaneous mass with variable calcification and posterior acoustic shadowing

Especially in buttock and lateral aspect of arm

Clinical Issues

• Almost 90% of FBs can be successfully removed under US guidance

Particularly if injury is recent

Chronically retained FB can be firmly adherent
• Hypoechoic rim can be breached by local anesthetic dissection or blunt forceps dissection

TERMINOLOGY

Abbreviations

• Foreign body (FB)
• Injection granuloma (IG)

Definitions

• FB granuloma: Retention of penetrating or iatrogenic object within tissues with resultant granulomatous reaction
• IG: Localized chronic granulomatous tissue reaction to injected material

IMAGING

General Features

• Best diagnostic clue

FB: Echogenic material ± posterior artifact ± hyperemic hypoechoic rim

IG: Localized hypoechoic swelling of subcutaneous tissues → ill-defined mass with peripheral hyperemia → well-defined mass ± calcification
• Location

FB: Subcutaneous tissues > > deep tissues

– Hands and wrists > feet

IG: Subcutaneous tissue, particularly superolateral aspect of gluteal region and lateral aspect of proximal arm
• Size

FB: Usually small (1-3 cm) but can be large (≥ 10 cm)

IG: Usually small (2-5 cm)

– Dependent on amount and dispersion of injected material
• Morphology

FB: Depends on size and shape of FB and inflammatory response

– Wood (45%), glass (25%), needle (10%), metal (10%), and others (e.g., grit, fish fin, pencil lead) (10%)

IG: Firm to hard subcutaneous nodule

Radiographic Findings

• FB: Detects radiopaque FBs, such as metal, glass, and some plastics

≤ 15% wood FBs are radiopaque

Limited information on exact location of FB and associated soft tissue response
• IG: ± calcified subcutaneous mass

CT Findings

• NECT

FB granuloma

– Typically seen as hyperdense object with variable surrounding inflammation or fibrosis

– Wood may appear hypodense and simulate air

IG: Well-defined subcutaneous mass

– ± lobulated or rim calcification (often dense)

MR Findings

• Less accurate than US at detecting FBs

Good visualization of inflammatory response

Ultrasonographic Findings

• FB

Echogenic object ± posterior artifact (reverberation/comet-tail artifact or posterior shadowing)

Echogenicity is dependent on acoustic impedance between retained FB and surrounding tissue

– Reflectivity of some objects (wood, metal, glass, plastic) exceeds that of others (bamboo)

– Reflectivity also dependent on smoothness of FB and alignment to US beam

± hypoechoic halo of inflammatory edematous tissue, granulation tissue, or fibrosis

– Presence of halo depends on intensity of inflammatory response and duration of retention of FB

May be apparent within 24 hours of retention

– Improves sensitivity and specificity of US detection

– Variable hyperemia of hypoechoic rim
• IG

Focal swelling and disruption of subcutaneous fat

– Similar to early stages of fat necrosis

– ± small areas of liquefaction

– ± mild peripheral hyperemia

Swelling may progress to ill- or well-defined hypoechoic mass

– ± mild peripheral hyperemia

– ± dense calcification

Limits visibility of deep margin of mass

Nuclear Medicine Findings

• IG may accumulate tracer on FDG PET imaging

False-positive for subcutaneous metastatic deposit

Imaging Recommendations

• Best imaging tool

US: Modality of choice to detect radiolucent FBs and diagnose IGs

– Sensitivity and specificity > 90% for radiolucent FB detection
• Protocol advice

FB

– First, check with patient regarding type and size of FB, direction of implantation, and likelihood of FB retention

– Align probe as parallel to FB as possible

– Examine beyond entry wound

– FB may be located some distance from entry wound

e.g., hand entry wound may give rise to FB in distal forearm

Only gold members can continue reading. Log In or Register to continue

Share this:
Click to share on Twitter (Opens in new window)
Click to share on Facebook (Opens in new window)

Related posts:

Hand Vessels Musculoskeletal Ultrasound Artifacts Epidermoid Cyst Shoulder Hip and Pelvis Procedures Baker Cyst

Stay updated, free articles. Join our Telegram channel

Tags: Diagnostic Ultrasound Musculoskeletal

Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off

KEY FACTS

Terminology

TERMINOLOGY

Abbreviations

IMAGING

General Features

Stay updated, free articles. Join our Telegram channel

Radiology Key

Fastest Radiology Insight Engine

Foreign Body and Injection Granuloma

Foreign Body and Injection Granuloma

Imaging

Clinical Issues

Definitions

Radiographic Findings

CT Findings

MR Findings

Ultrasonographic Findings

Nuclear Medicine Findings

Imaging Recommendations

Full access? Get Clinical Tree

Fastest Radiology Insight Engine

Foreign Body and Injection Granuloma

Share this:

Related posts:

Stay updated, free articles. Join our Telegram channel

Full access? Get Clinical Tree