## Tuberculous Cavitary Patterns: Thin-Walled vs Thick-Walled **Key Point:** The morphology of cavities—thin-walled (smooth, regular borders) vs thick-walled (irregular, shaggy borders)—is a key radiological discriminator in TB and reflects disease activity and chronicity. ### Thin-Walled Cavities (Acute/Healing Phase) - Smooth, regular borders - Minimal surrounding inflammation - Indicates relatively recent cavity formation - Often seen in early reactivation TB - May represent healing or stabilization ### Thick-Walled Cavities (Fibrocaseous TB) - Irregular, shaggy, or nodular inner borders - Extensive surrounding consolidation and fibrosis - Indicates chronic, active disease - Represents fibrocaseous destruction of lung parenchyma - Associated with significant tissue necrosis and fibrosis ### Cavity Wall Morphology Comparison | Feature | Thin-Walled Cavity | Thick-Walled (Fibrocaseous) | |---------|-------------------|----------------------------| | **Wall appearance** | Smooth, regular | Irregular, shaggy, nodular | | **Border definition** | Well-demarcated | Ill-defined, blurred | | **Surrounding inflammation** | Minimal | Extensive | | **Fibrosis** | Minimal | Marked | | **Activity** | Early/healing | Chronic/active | | **Surrounding consolidation** | May be present | Always present | | **Associated findings** | Bronchial spread possible | Bronchial spread, bronchiectasis | **Clinical Pearl:** A thin-walled cavity in the upper lobe of a patient with TB may indicate recent cavity formation or healing; thick-walled cavities with shaggy borders suggest chronic fibrocaseous disease with ongoing destruction. **High-Yield:** Fibrocaseous TB = thick-walled, irregular cavities + extensive fibrosis + bronchial spread. This is the classic "end-stage" TB pattern. **Mnemonic:** **THICK = Chronic, Irregular, Caseous, Kilohertz (fibrosis)** — thick-walled cavities indicate chronic, destructive fibrocaseous disease. 
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