[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Radiology](https://durgical.com/en/radiology/) › [Chest](https://durgical.com/en/radiology/areas/chest/) › Pneumothorax on the chest X-ray # Pneumothorax on the chest X-ray - Finding Air leaks into the space around the lung and the lung pulls away from the chest wall. The X-ray shows a thin white line with no lung pattern beyond it. Updated Nov 12, 2026 ## Key points - Thin pleural line with no lung markings beyond = pneumothorax. - Supine: deep sulcus sign; the apex can look normal. - Tension is clinical: decompress first, image later. - Skin folds and bullae are the classic mimics; CT if in doubt before any drain. ## What it is A pneumothorax is air in the pleural space. On an upright chest X-ray the air rises to the apex: one sees the visceral pleura as a thin, sharp white line, with no lung markings between that line and the chest wall. On a supine film, as in trauma, the air collects in front and at the base instead, so the signs are subtle: an unusually deep, dark costophrenic angle (deep sulcus sign), a lucent hemithorax and a very sharp heart or diaphragm edge. Tension pneumothorax pushes the mediastinum away and flattens the diaphragm, but it is a clinical diagnosis to treat at once, not one to confirm on film. ## What it looks like - Visceral pleural line: a thin white line, parallel to the chest wall, with no vessels beyond it. - Upright film: look at the apices first, where the air collects. - Supine film: deep sulcus sign, hyperlucent hemithorax, unusually sharp heart border or hemidiaphragm. - Tension: mediastinum and trachea shifted away, flattened or inverted hemidiaphragm, widened rib spaces. - Size (British guidance): a rim of air of 2 cm or more at the level of the hilum is large; American guidance measures apex to dome, 3 cm or more. ## Why it looks that way - Air in the pleural space lets the lung recoil toward the hilum, so the pleural edge becomes visible against air on both sides. - Air rises: upright it goes to the apex, supine it goes to the front and the base of the chest. - In tension, a one-way valve traps air with each breath; rising pressure shifts the mediastinum and kinks venous return. ## Differential and pitfalls - Skin fold: a broad edge rather than a thin line, often running beyond the chest wall, with lung markings on both sides. - Large bullae in emphysema mimic a pneumothorax; their wall is concave to the chest wall. CT separates them before any drain. - The medial edge of the scapula, clothing and tubes can mimic a pleural line; trace it to its end. - A small or supine pneumothorax is often missed on X-ray; CT is the most sensitive and lung ultrasound helps at the bedside. - Lung ultrasound: absent lung sliding and no B-lines suggest it; finding the lung point confirms it. ## Next step - Suspected tension (hypotension, distress, shift): decompress at once and call a senior; do not wait for an X-ray. - Stable patient: size on the upright film plus symptoms and lung disease decide observation, aspiration or a chest drain. - Unclear pneumothorax versus bulla, or a supine trauma film with doubt: CT of the chest. - Bedside in trauma or the critically ill: lung ultrasound (eFAST) can show it before the X-ray. - After aspiration or drain insertion: repeat the chest X-ray to check re-expansion and the drain position. ## Test yourself Think of the answer, then tap the question to see it. ## What is the deep sulcus sign? On a supine film, an abnormally deep and dark lateral costophrenic angle from air collecting at the front and base of the chest: a sign of pneumothorax. ## How do you tell a skin fold from a pneumothorax on the X-ray? A skin fold is a broad edge, often extends beyond the chest wall and has lung markings on both sides; a pneumothorax is a thin line with no markings beyond it. ## Should a chest X-ray be taken before treating a suspected tension pneumothorax? No. Tension is a clinical diagnosis; decompress immediately and image afterwards. ## Which lung ultrasound finding confirms a pneumothorax? The lung point: the place where sliding lung meets the non-sliding air, seen at the edge of the pneumothorax. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/radiology/pneumothorax-on-the-chest-x-ray/) ## Connections ## Related 6 - [Reading a chest X-ray step by step](https://durgical.com/en/radiology/reading-a-chest-x-ray-step-by-step/) - [Is this chest X-ray good enough? Projection, rotation, inspiration and exposure](https://durgical.com/en/radiology/is-this-chest-x-ray-good-enough-projection-rotation-inspiration-and-exposure/) - [Lines and tubes on the chest X-ray: where each tip should be](https://durgical.com/en/radiology/lines-and-tubes-on-the-chest-x-ray-where-each-tip-should-be/) - [Free air in the chest: pneumomediastinum and subcutaneous emphysema](https://durgical.com/en/radiology/free-air-in-the-chest-pneumomediastinum-and-subcutaneous-emphysema/) - [Lung ultrasound: A-lines, B-lines and lung sliding](https://durgical.com/en/radiology/lung-ultrasound-a-lines-b-lines-and-lung-sliding/) - [The FAST and eFAST exam in trauma](https://durgical.com/en/radiology/the-fast-and-efast-exam-in-trauma/) ## Related conditions 1 - [Pneumothorax](https://durgical.com/en/conditions/pneumothorax/) [← All of radiology](https://durgical.com/en/radiology/) Educational content; it does not replace a radiologist's report and is not a clinical instruction. Each study is ordered on the patient's assessment and your institution's protocols. Sources: [Acute Pneumothorax Evaluation and Treatment](https://www.ncbi.nlm.nih.gov/books/NBK538316/) (StatPearls (NCBI Bookshelf), 2025); [Tension Pneumothorax](https://www.ncbi.nlm.nih.gov/books/NBK559090/) (StatPearls (NCBI Bookshelf), 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/radiology/pneumothorax-on-the-chest-x-ray/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/radiology/pneumothorax-on-the-chest-x-ray/