Chest drain position on X-ray

Written by the X-Ray Atlas editorial team from the sources listed below · Medical review pending · Updated 24 October 2026 · Level: Intermediate

An intercostal chest drain removes air, fluid, blood or pus from the pleural space. The X-ray after insertion is used to check that the drain is inside the pleural cavity with all its side holes, that it is achieving its purpose (the lung is re-expanding, the fluid is draining), and that insertion has not caused harm. Unlike most devices, the exact tip position matters less than whether the drain works. A drain that is subcutaneous, in the lung, in a fissure or below the diaphragm is a problem, and some of these positions can only be suspected on a frontal film. This page covers the insertion site, the post-insertion checks, malpositions and complications.

1. Drain types and what they look like

• Small-bore drains (commonly around 8–14 French), inserted with a Seldinger (guidewire) technique, are now used for most spontaneous pneumothoraces and many effusions. Many have a "pigtail" curl at the tip.
• Large-bore drains, inserted by blunt dissection, are used more often in trauma, haemothorax and after surgery.
• Most drains have a radiopaque stripe along their length. On many drains, a gap in the stripe marks the last (most proximal) side hole, sometimes called the sentinel hole. This is the key landmark for checking that all the holes are inside the chest.
• Indwelling pleural catheters for malignant effusions are tunnelled under the skin before entering the pleura, so their subcutaneous course is normal.

2. The insertion site: the triangle of safety

The British Thoracic Society (BTS) recommends inserting drains within the "triangle of safety", which avoids major vessels, the internal thoracic artery, the breast and the muscles of the chest wall:

• anteriorly: the lateral border of pectoralis major;
• posteriorly: the anterior border of latissimus dorsi;
• inferiorly: a horizontal line at about the level of the 5th intercostal space (roughly the nipple level in men);
• with the apex just below the axilla.

Insertion below this level risks entering the abdomen, the liver or the spleen, especially when the diaphragm is raised. Imaging guidance (ultrasound) is recommended by BTS for drains inserted for fluid. On the film, the entry point is usually seen as the place where the drain crosses the chest wall in the mid-axillary region.

3. The post-insertion film: what to check

A frontal film shows the drain in two dimensions only. A drain that looks satisfactory can still be in a fissure, in the lung, or just outside the pleura in the chest wall. Clinical checks matter: a drain in the pleura usually shows the fluid in the tubing swinging with respiration, and bubbling if there is an air leak.

4. Tip position: air versus fluid

• For a pneumothorax, a drain directed towards the apex is classically preferred, because air rises in the erect patient.
• For fluid, a drain directed towards the base (posteriorly and inferiorly) is classically preferred.
• In practice, function matters more than the exact tip position. A drain that is not apical but is draining well and has re-expanded the lung does not need to be moved. A drain that looks perfectly placed but is not working needs to be investigated.

5. Malpositions

Malposition	Clues
Subcutaneous (outside the pleura)	The drain follows the curve of the chest wall without entering the thorax. Surgical emphysema around it; no swing in the tubing; no change in the pneumothorax or effusion.
Side hole outside the chest	The gap in the radiopaque stripe lies lateral to the ribs, in the soft tissues. Expect surgical emphysema and an air leak.
In a fissure	The drain lies along the line of the horizontal or oblique fissure, often running horizontally across the mid-zone. It may drain poorly. A lateral film or CT shows it best.
In the lung (intraparenchymal)	Can look normal on the frontal film. Suspect it with haemorrhage around the tip, a persistent air leak or a poorly functioning drain. CT confirms.
Below the diaphragm	The drain tip projects below the hemidiaphragm. Can injure the liver, spleen or stomach. CT confirms.
Mediastinal	The tip crosses the midline towards the mediastinum or heart. Rare and dangerous; urgent senior review.

6. Complications

Surgical emphysema

A small amount of air in the soft tissues around the insertion site is common. Extensive or increasing surgical emphysema suggests a side hole outside the pleura, a blocked or displaced drain, or a large air leak. It can obscure an underlying pneumothorax on the film.

Re-expansion pulmonary oedema

Rapid re-expansion of a lung that has been collapsed for some time (classically more than about 72 hours) can cause pulmonary oedema on the re-expanded side: new air-space opacity in the lung that has just come back up, usually with cough and breathlessness. To reduce the risk, the BTS has advised controlling the rate of fluid drainage, and limiting the volume drained at one time to about 1.5 L. Check your local protocol for the exact rule.

Haemothorax and organ injury

Injury to an intercostal vessel or to the lung can produce a new or enlarging pleural collection. Injury to the liver, spleen, heart or great vessels is rare but catastrophic, and is more likely with insertion outside the triangle of safety or with trocar techniques.

Infection

Empyema and wound infection develop later and are clinical diagnoses supported by imaging, often ultrasound or CT.

7. The drain that isn't working

When a pneumothorax persists or an effusion remains despite a drain, work through the possibilities:

• Blocked or kinked drain: check the tubing and the film for a kink. Small-bore drains block more easily with thick fluid.
• Displaced drain: compare with the previous film. The drain may have pulled back, with the side holes now in the chest wall.
• Wrong place: subcutaneous, in a fissure, or in the lung.
• Persistent air leak: a bronchopleural fistula or large leak, often with continuous bubbling. This needs respiratory or thoracic surgical input.
• Loculated collection: fluid divided by septations, common in empyema. Ultrasound or CT helps.
• Trapped lung: a lung that cannot re-expand because of a thick visceral pleural rind, so a pneumothorax-like space persists despite a working drain.

A drain should never be clamped when it is bubbling, except under specialist direction, because this can convert a pneumothorax into a tension pneumothorax.

Red flags: act now

What to focus on, by role

Role	Priorities
Medical student	The triangle of safety, the idea that side holes must be inside the chest, and the difference between a pneumothorax and surgical emphysema on the film.
Nurse	Swinging, bubbling and drainage volume; keep the bottle below the chest; never clamp a bubbling drain without instruction; report increasing surgical emphysema or breathlessness.
Junior doctor	Check the side holes, the purpose and complications on every post-drain film. Recognise a non-working drain and work through the causes rather than inserting a second drain without senior input.
Radiographer	Include the whole drain, the lateral chest wall and the costophrenic angles. A lateral film may be requested to look for a fissural or subcutaneous drain.
Advanced / FRCR	Fissural and intraparenchymal drains, trapped lung, bronchopleural fistula and when to recommend CT.

See also: chest trauma, central lines and PICCs and the glossary.

Practise on lines and tubes films →

References

1. Roberts ME, et al. British Thoracic Society Guideline for pleural disease. Thorax 2023;78(Suppl 3):s1–s42. thorax.bmj.com
2. British Thoracic Society. Pleural disease guideline resources. brit-thoracic.org.uk
3. RCEM Learning. Spontaneous pneumothorax. rcemlearning.co.uk
4. Radiology Masterclass. Chest X-ray: lines and tubes. radiologymasterclass.co.uk

For education only. Not a substitute for a formal report, senior review or your local policy. Never use this page to make decisions about a real patient.