A deeper dive into enteroliths
With the potential to create considerable pain and discomfort, DR CAROLINE SPELTA explains what causes enteroliths and how they can be treated.
The image of a horse peacefully grazing is a symbol of pastoral tranquillity. Yet, within the complex digestive system of these magnificent animals, a hidden threat can silently develop: an enterolith.
These mineral masses, often undetected until they cause severe distress, pose a significant challenge to equine health. So let’s delve deeper into the formation, clinical signs, treatment, and prevention of these intestinal stones.
The genesis of a stone
Enteroliths are primarily composed of struvite, a mineral compound of magnesium ammonium phosphate. Their formation is a gradual process, often beginning with a small foreign object, or nidus, lodged within the horse’s large colon. This could be anything from a grain of sand or gravel to a stray piece of hair or baling twine. Over time, layers of minerals gather around this nidus, much like the formation of a pearl, slowly but surely increasing the size of the enterolith.
While they are small, they may pass out through the intestinal tract and never cause a problem, or even be noticed. If the stone stays in the large colon and continues to expand in size, they only start to cause problems if they become very heavy, move into one of the smaller diameter colons and get wedged there (the pelvic flexure and small colons are common locations).
More commonly they are in the left ventral colon and move forward to the start of the pelvic flexure where they act like a ball valve blocking it, then they roll away and back again. This can happen over days, weeks, or months resulting in a chronic/repeated colic.
Several factors contribute to this mineral accumulation:
Dietary influences:
- Lucerne hay, a popular feed choice, is a significant culprit due to its high mineral content, particularly calcium and magnesium.
- Imbalances in other dietary minerals can also play a role.
- Horses fed hard feeds generally get a diet higher in minerals compared to those only on pasture.
Genetic predisposition:
- Certain breeds, notably Arabians, exhibit a higher incidence of enteroliths, suggesting a genetic component.
Environmental factors:
- Geographic location can influence mineral content in soil and water, potentially increasing the risk. Sandy and loam country both have a high mineral content. Horses that hoover scraps from the ground are more likely to ingest sand particles which act as the nidus to start the stone.
- Gut PH levels and gut motility are also very important factors.
Silent symptoms
The insidious nature of enteroliths lies in their ability to remain asymptomatic for extended periods. However, as the stones grow, they can cause a range of clinical signs, culminating in potentially life-threatening colic.
Colic: a spectrum of distress
- Colic, abdominal pain, is the hallmark symptom. It can manifest in degrees of severity: from mild, intermittent discomfort to acute, intense pain.
- Affected horses may exhibit behaviours such as pawing, kicking at their abdomen, rolling, and restlessness.
Subtle indicators
- Chronic, recurring episodes of mild colic – stretch out, paw, occasionally roll, but recover with minimal interventions (1-2 drenches and pain relief).
- Weight loss and decreased appetite.
- Changes in manure consistency.
- In some cases, very small enteroliths are passed within the manure, without the horse showing any clinical signs.
Diagnosis
Unfortunately, there is no single test that will diagnose the presence of an enterolith with certainty all of the time. An enterolith is often suspected in horses with a history of recurrent colic, or recurrent mild pelvic flexure impactions. Radiographs of the ventral abdomen can sometimes be rewarding to visualise the enterolith in the ventral colons, as can ultrasonography. Most times though, definitive diagnosis is made at surgery.
Intervention and management
When enteroliths cause significant colic, surgical intervention is typically the only effective treatment. Once of a size that the stones are causing colic, medical management is rarely, if ever, successful.
Surgical Removal:
- The procedure involves entering the abdomen and surgically removing the enterolith from the affected portion of the intestine.
- Early detection and prompt surgical intervention significantly improve the prognosis.
- Age is not a prognostic indicator of a successful recovery from surgery.
Post-Operative Care:
- Post-surgical management focuses on pain control, monitoring for complications, and dietary adjustments.
- Dietary modifications are crucial to prevent recurrence.
Preventive Measures
Proactive management is essential to minimize the risk of enterolith formation.
Dietary Strategies:
- Reduce or eliminate lucerne hay from the diet.
- Provide high-quality grass hay.
- Avoid excessive mineral supplementation.
- Maintain a balanced diet – use a feed ration calculator, or consult an equine nutritionist to make sure your horse’s diet is balanced.
Management Practices:
- Ensure regular exercise and turnout.
- Use feeders to prevent ingestion of sand and other foreign materials.
- Some horse owners have found positive results with adding apple cider vinegar to the feed.
- Regular manure observation.
Veterinary Consultation:
- Consult with a veterinarian for personalised dietary and management recommendations.
Be aware
Horses can also make faecoliths (rock like faeces) which can have a similar presentation to a horse with an enterolith, with moderate to severe signs of colic. Miniature ponies and Shetlands are more likely to have multiple faecoliths at any one time causing colic. Horses as young as one year of age can develop a faecolith (enteroliths are more common in older horses as they take time to form). Horses and ponies can also form up new faecoliths within twelve months.
Similar to the genesis of enteroliths, faecoliths can form around a nidus (piece of gravel, sand or twine). Occasionally, faecoliths can be managed medically with intensive veterinary care, fluid therapy and pain relief – but like enteroliths, sometimes surgery is the only treatment option.
A word of caution
It is vital to emphasise the importance of early detection and veterinary intervention. If you suspect your horse may be suffering from enteroliths, seek professional veterinary assistance immediately.
By understanding the factors that contribute to enterolith formation and implementing preventive measures, horse owners can play a crucial role in safeguarding the health and well-being of their equine companions.
Dr Caroline Spelta has extensive expertise in Australasian equine internal medicine and toxicology, and can be found at Clermont Veterinary Surgery in Clermont, Queensland.
