Chest X-ray - Tubes
NG Tubes - Position

Key points

  • Chest X-rays are used to determine nasogastric (NG) tube position if aspiration of gastric fluid is unsuccessful
  • An understanding of the anatomical location of the oesophagus is required

If aspiration of gastric fluid following placement of an nasogastric (NG) tube is unsuccessful, then a chest X-ray can be used to help determine tube position.

Oesophagus anatomy

A correctly positioned NG tube passes vertically down the oesophagus into the stomach. As the oesophagus is not visible on a plain chest X-ray, it is essential to have an understanding of its anatomical position in relation to other visible structures.

Oesophagus anatomy

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Oesophagus anatomy

  • The oesophagus passes posteriorly and slightly to the left side of the trachea
  • The oesophagus is located immediately to the right of the aortic knuckle
  • From this level the oesophagus passes down in the midline to the level of the gastro-oesophageal junction which is at the level of the diaphragm

Correct NG tube position

A correctly positioned nasogastric tube passes vertically in the midline, or just to the left of the midline. Below the level of the carina the tube must not follow the course of either of the main bronchi, but should remain in the midline down to the level of the diaphragm where it passes through the gastro-oesophageal junction.

The tip of the NG tube should be visible at least 10 cm beyond the gastro-oesophageal junction.

Correct NG tube position

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Correct NG tube position

  • Check the tube passes vertically in the midline, or near the midline, below the level of the carina (red ring)
  • The tube MUST NOT follow the course of the right or left main bronchi
  • Check the tube continues vertically in the midline down to the level of the diaphragm where it passes through the gastro-oesophageal junction (orange ring)
  • The tip of the tube (green ring) must be visible below the diaphragm and on the left side of the abdomen - 10 cm or more beyond the gastro-oesophageal junction

If the nasogastric tube passes below the level of the diaphragm but its tip is not visible, a second image may be necessary to determine its position.

NG tube tip position - Image 1 - tip not visible

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NG tube tip position - Image 1 - tip not visible

  • The tube passes in the midline below the level of the carina (red ring)
  • The tube does not enter the right or left bronchi
  • The tube stays in the midline below the carina to the level of the gastro-oesophageal junction (orange ring)
  • The tip of the tube is projected below the lower edge of the image and so its position cannot be determined

NG tube tip position - Image 2 - tip visible

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NG tube tip position - Image 2 - tip visible

  • An additional image shows the NG tube tip located below the diaphragm on the left side of the abdomen

Important note: An X-ray of tube positioning only offers information regarding tube positioning at the time the X-ray was acquired. It is essential that the external tube position is documented using its external length markers. Once tube position is established to be correct, rechecking the external position is required prior to each feeding.