Nasogastric tubing is commonly used as a diagnostic (as opposed to a treatment) to determine whether there is fluid (reflux) or gas built up in the upper intestine or stomach. It is a fundamental diagnostic for horses experiencing abdominal pain (colic). It is also commonly used to confirm or rule out a diagnosis or choke (esophageal obstruction).

In an average horse, the stomach is located about 5 feet from their mouth. At the level of the horse's throat there is a fork in the road; the esophageal opening is directly above the opening to the wind pipe (trachea), which carries air to the lungs. Therefore, when performing this diagnostic, a vet must feel their way into the esophagus and ensure the tube does not go into the windpipe.

This procedure should only be performed by a vet or experienced technician because inadvertent passage of the tube into the windpipe, with the introduction of fluid into the lungs can be fatal.

A 3-4 meter long, 1/2" -1" diameter plastic tube is passed through a nostril, into and through a nasal passage and into the pharynx. Here a vet may pause to encourage the horse to swallow. The swallow helps position the tip of the tube in the esophagus. Most horses cough a few times when the tube is around the larynx (voice box). Coughing is severe if the tube inadvertently goes into the windpipe. Persistent coughing may cause the vet to carefully reevaluate the placement of the tube to ensure it is not in the windpipe.

Once the tube is in the esophagus, it is gently pushed down for about a meter to the tight ring of muscle at the entry to the stomach. This ring is gently stretched (or inflated) open and the stomach is entered. When the tube enters the stomach, you may hear (or smell) a short rush of gas from the stomach. In some cases, small amounts of fluid may run out the end of the tube.

If there is a steady stream of fluid from the tube, it usually indicates that there is an accumulation of abnormal fluid in the stomach. Nasogastric tubing is also used as a treatment to remove fluid (refluxing), introduce fluids or other medications, or to gently remove an obstruction causing choke.

Passage of a nasogastric tube is an art and should look easy for an experienced practitioner, even on a resistant horse. If a horse is halter trained, a vet should be able to tube it without sedation or much fuss. I easily tube about 80-90% of the horses I attempt to tube, without sedation and without a twitch. I use a twitch for the remainder. A very small percentage of these remaining horses will not accept a twitch, and in that case I use whatever restraint I need to use to get it done.

I very rarely sedate a horse to pass a nasogastric tube. I think it is almost always unnecessary and in most cases only complicates the assessment of their health. An exception to this is the treatment of the horse with choke. Treatment of choke requires minutes to hours of manipulation of the tube in the esophagus with the intent to break down the obstruction. Sedation is almost always helpful in this circumstance.