Sand Colic

Horses that live in sandy environments are predisposed to ‘sand colic’.

There are regions around the world where sand ingestion occurs commonly. These include south western Australia, certain regions in the USA (including Florida), Scandinavia, and the Middle East. There is a difference between how individual animals handle sand ingestion, and therefore making blanket recommendations across a herd can be difficult. In some research horses the amount of sand entering the gastrointestinal tract was the same as the amount leaving the tract in manure. These animals do not accumulate large sand loads and can tolerate sandy pastures. Conversely, there are some horses that will accumulate sand in their large intestine, predisposing them to intestinal obstruction and colic. What predisposes these animals to sand accumulation is the subject of debate. An important consideration is the sand particle size: in regions with very fine particles the sand tends to set, similar to concrete, whereas in regions where the particle size is large it tends to be more apt to pass through. Particle size also influences the sand sounds heard on auscultation of the ventral abdomen.

Sand and dirt accumulation in young foals is very frustrating. For some reason, beyond any known nutritional deficiency, some foals will develop an ‘addiction’ to eating sand. This appears to be a vice. It is also not uncommon to see sand loads also develop in adult horses that have not been previously exposed to sandy pastures.


Diagnosis

The suspicion of a sand problem is based on several historical and physical findings.

The primary clinical sign of sand ingestion is colic. This is typically due to intraluminal obstruction (blockage) of the large intestine. The abdominal pain is caused by a couple of mechanisms. Firstly, waves of contraction passing over the obstruction cause intermittent ‘cramping’ signs. Secondly, there is distention of the intestine ahead of the sand obstruction with gas that is produced from fermentation. This causes abdominal distention (paunch) and more persistent signs of colic.

Weight loss and diarrhoea are other signs that are frequently ascribed to sand ingestion. The mechanism of diarrhoea is not known, but a popular theory is that is caused by sand irritation to the intestinal mucosa.

In some cases there may be large amounts of sand passed in the faeces, but this is unusual. A sand sedimentation test can be performed. Sand sedimentation is easily done by mixing feces with water in a rectal sleeve. A negative sedimentation test does not rule out sand however a large amount of sand certainly supports it.

A strongly positive sand sedimentation test.
Sand passed in maure, or manure passed in sand (source unknown)

Auscultation of the cranioventral abdomen is very helpful in supporting a sand diagnosis. This relies on intestinal motility being present. Many horses with moderate to severe signs of colic will experience intestinal stasis. Also popular sedative analgesic drugs, like xylazine and detomidine, will also reduce large intestinal motility. The classic sand sounds are reminiscent of a long wave breaking on a quiet beach.

Sand is rarely palpable on rectal examination, as most obstructions are ventrally located due to their weight. The presence of sand on the glove or in manure pulled from the rectum can be supportive of a diagnosis, but an absence does not rule out sand as the primary cause of the colic.

Ultrasound examination can semi-quantitate sand in the ventral abdomen. Radiography is the technique of choice to determine the presence and amount of sand in the abdomen.

A radiograph demonstrating a severe sand load in the colon. Note the stretching of the ventral colon, a structure that is normally sacculated.

Is sand colic seasonal?

This probably varies with geographic location, and therefore climate. In south western Australia the condition does occur with a much greater frequency in late autumn and winter. After a long, dry summer where pasture has disappeared the onset of rains bring green shoots to the paddock. Enthusiasm for anything green results in devouring of shoots, roots and often a lot of sand.


Treatment and Prevention

Management of the colic associated with sand ingestion is dictated by the degree of pain, magnitude of the heart rate increase, status of the circulatory system, and degree of abdominal distention. Techniques may include use of sedative analgesics, synthetic narcotics, and non-steroidal anti-inflammatory drugs to control signs of abdominal pain. In some horses the obstruction of the large colon is complete and the pain becomes persistent and moderate to severe. This frequently necessitates the need for surgery and removal of the sand.

In some cases decompression of the caecum can provide some temporary relief, particularly if surgery is not an option.

A 14 gauge catheter inserted sterilely into the caecal base
Confirmation of gas removal is seen by bubbling through a liquid

There are several strategies that are used to try and remove the sand, without surgery.

Common therapies to eliminate sand loads include mineral oil (5-10 mL/kg bodyweight), magnesium sulphate (Epsom salts, 1 gm/kg bodyweight daily for 3 days), and sodium sulphate (Glauber’s salts, 1 gm/kg bodyweight daily). Some vets will use a combination of therapies in the early stages of managing sand colic.

Fluid therapy is an important component in the management of colic due to sand ingestion. In most cases this achieved by drenching water ± electrolytes using a nasogastric tube.


Psyllium mucilloid is used in sand impactions because of its property as a bulk laxative. The efficacy of psyllium in the removal of intestinal sand has been controversial, although most vets who work with this problem agree that it is highly beneficial.

Psyllium husk is derived from the tiny seeds of the shrub Plantago ovata. It is a water-soluble source of fibre and is widely advocated and used in human health. There are many controversies surrounding the use of psyllium in horses.

How much to use? Dosages that are typically quoted in the literature vary between 0.5 to 1.0 gram of psyllium per kilogram of bodyweight once daily. That is a lot of raw psyllium husk.

What products to use? The products to use are dependent on whether you are trying to eliminate an existing load or simply trying to minimize the amount of sand present. You can purchase native psyllium husk that is 100% psyllium. Feeding that product would require the horse consuming up to 500 grams daily; that is a very large volume to feed and most horses would not consume that amount. To reduce the volume vets will often use more dense commercial preparations, such as Metamucil, Genfiber, Bonvit or similar products. These dense preparations are particularly important when administering psyllium via a nasogastric (stomach) tube to eliminate very large sand loads, often combined with other laxative compounds. It is important to note that many of these preparations are not 100% psyllium; they often include sugar to improve palatability. Consequently, some of these products may only be 48-60% psyllium. In a study we performed our horses were more likely to consume the orange-flavoured Metamucil product than natural or other flavours. There are a large number of commercial pellet formulations that are based on psyllium. Some are 100% psyllium, whereas others may only contain a small amount of the ingredient. It is important to calculate the amount of psyllium that will be fed daily and note how it compares to the recommended amounts.

How long to feed for? As a soluble fibre psyllium can be used as an energy source. Consequently, prolonged feeding is thought to negate any effect as a bulk laxative. This is related to ability of the intestinal flora to adapt to psyllium in the diet. It is often recommended to feed psyllium for no more than 7-10 days every month to prevent the gut from breaking it down.

When not to use psyllium? The gastrointestinal tract must be patent (unblocked) before psyllium is used. If sand is causing a blockage then psyllium may sit ahead of the blockage and ferment, causing gas production which will worsen any signs of colic. For this reason vets will not start using psyllium in a horse with sand colic until the blockage has been resolved.

Any other issues with psyllium? Psyllium is very hydrophilic and will rapidly expand when added to water. Care should be taken when administering psyllium using a nasogastric tube, especially to miniatures and small ponies. My preference is to administer psyllium in a fasted state to prevent gastric overdistention. Another related problem is administering psyllium and water in a nasogastric tube – this requires a certain level of skill and experience. The ability to stir and pump rapidly and simultaneously is needed to prevent psyllium from ‘setting’ inside the tube, rendering the tube useless. This is not a client winning move. This problem is avoided by mixing psyllium with mineral oil. Psyllium also will negatively impact the absorption of a range of drugs, and from a potentially positive point-of-view, in horses with EMS can attenuate the glucose and insulin increases after a meal. A further note of caution: I have seen several horses where the administration of psyllium to asymptomatic (non-colicky) horses led to episodes of severe colic. It is believed that the treatment caused sand to move on top of existing sand, causing a blockage. This is very hard to predict.

Recently, positive results were reported by Drs. Izzy Entwistle and Emma McConnell using a combination of psyllium, epsom salts and mineral oil to remove sand from horses with colic.

Dioctyl sodium succinate (DSS), raw (not boiled) linseed oil, and berg oil (wood tar, gum turpentine and methylated spirits) are occasionally used, but are not recommended.

Management

As discussed above not all horses on sandy pasture will accumulate sand in their large intestine. Simple techniques to monitor for sand include auscultation of the ventral abdomen, listening for characteristic ‘sand’ sounds, and monitoring the faeces for sand using water sedimentation. Both techniques are unreliable in determining sound loads, although the presence of sand sounds should raise an index of suspicion.

The most useful method for determining intestinal sand loads is plain abdominal radiography. There are several practitioners in Western Australia that have the equipment to obtain diagnostic images in most horses. Some larger horses may need to travel to hospital-based practices with larger capacity radiography units to effectively image the ventral abdomen.

An important aspect of management is to manage pasture through low stocking density. This may be difficult in areas with a primary sand base. Feeding hay over a rubber mat or concrete slab will reduce the amount of sand picked up in foraging remaining hay.

As always, provide access to shade and a consistent source of clean, fresh drinking water is essential.


Tags: Gastrointestinal; colic; sand; psyllium