Lung ultrasound and the interstitial syndrome in tuberculosis endemic regions: illustrated insights from diverse clinical settings.

Lung ultrasound (LUS) is increasingly used as a diagnostic tool in respiratory medicine, particularly in resource-limited, tuberculosis (TB)-endemic settings. Sonographic interstitial syndrome (IS), characterized by B-line artefacts, has proven valuable in diagnosing cardiogenic pulmonary edema, pneumonia, and chronic interstitial lung disease. However, in TB-endemic areas, its interpretation remains challenging due to overlapping pathologies. This illustrated review explores the diagnostic and prognostic relevance of IS across three clinical contexts: acute respiratory distress, chronic interstitial lung disease, and pulmonary TB. We review current evidence and discuss illustrative cases from TB-endemic settings to highlight sonographic pattern variations and guide clinicians in recognizing key diagnostic features and common pitfalls. IS, while inherently non-specific, gains diagnostic value when contextualized within the patient's background and within additional sonographic findings such as pleural line abnormalities, consolidations, and altered lung sliding. Specific TB manifestations-including miliary TB, cavitary TB, HIV-associated TB, and post-TB sequelae-demonstrate diverse IS presentations. Accurate interpretation requires understanding disease-specific patterns, using appropriate scanning techniques, and adhering to standardized protocols. Greater awareness of IS variations among clinicians can improve diagnostic accuracy and clinical decision-making in TB-endemic regions.