Colic in Horses: Signs, Causes, and Prevention

Colic, defined loosely as abdominal pain from any cause, remains one of the most frequent and costly equine emergencies worldwide [9]. It is a leading cause of morbidity and mortality in horses, with significant welfare and economic implications [3]. While approximately 90% of colic episodes resolve spontaneously or with medical treatment, the remaining 10% can be fatal if not treated promptly and appropriately [16]. Understanding the types of colic, recognizing early warning signs, knowing how to respond in an emergency, and implementing robust prevention strategies are essential for every horse owner, manager, and veterinarian. This article synthesizes the latest scientific evidence and clinical guidelines to provide a comprehensive overview of colic in horses.

Quick Q&A

Question: What are the first signs of colic in horses? Answer: Early signs include restlessness, pawing, looking at the flank, rolling, lying down more than usual, decreased appetite, and reduced fecal output. More subtle behavioural changes such as depression, isolation, or altered posture can also indicate pain. Immediate veterinary assessment is recommended if any of these signs are observed.

Types of Colic

Colic is not a single disease but a clinical sign of abdominal pain arising from various gastrointestinal and non-gastrointestinal causes. The major categories include:

Spasmodic Colic

Spasmodic colic, characterized by increased intestinal motility and cramping, is the most common type, accounting for approximately 68% of cases in some studies [11]. It often results from stress, dietary changes, or mild intestinal irritation and typically responds well to medical management.

Impaction Colic

Impaction colic occurs when ingesta accumulates and obstructs the large colon or cecum. It represents about 28% of colic cases [11]. Risk factors include inadequate water intake, poor-quality forage, dental disease, and reduced exercise [17, 26]. Impactions are often managed medically with fluids and laxatives, but severe cases may require surgery.

Displacement and Entrapment Colic

These occur when a segment of intestine moves to an abnormal position, causing partial or complete obstruction. Left dorsal displacement of the large colon (nephrosplenic entrapment) is a classic example. Surgical closure of the nephrosplenic space significantly reduces recurrence of this specific type [10]. Displacement colic is less common (about 4% of cases) but carries a higher risk of mortality [11].

Strangulating Colic

Strangulating lesions, such as volvulus (twisting) or strangulating lipomas, compromise blood supply to the intestine. This type is a surgical emergency. Biomarkers such as tumour necrosis factor-alpha (TNFα), malondialdehyde (MDA), and nitric oxide (NO) are significantly elevated in strangulating colic compared to non-strangulating forms, reflecting ischemia and inflammation [5].

Sand Colic

Ingestion of sand or soil can lead to accumulation in the colon, causing irritation, impaction, or displacement. Radiographic grading of sand accumulations helps differentiate incidental findings from clinically significant disease; grades 1-2 are common in asymptomatic horses, while larger accumulations are more likely to cause colic [56].

Other Types

Other causes include enteroliths, feed impactions, inflammatory conditions, and parasitic damage. Equine coronavirus (ECoV) and even bovine coronavirus (BCoV) have been detected in horses with colic, suggesting infectious etiologies warrant consideration [38].

Warning Signs: Recognizing Pain Early

Early recognition of colic is critical for a positive outcome [15]. The Equine Acute Abdominal Pain Scale (EAAPS) is a validated tool that helps clinicians and owners assess pain severity quickly and reliably [7]. Pain can be grouped into behavioural changes, posture modifications, and interactions with the environment [15].

Behavioural Signs

• Restlessness, pawing, flank-watching
• Repeated lying down and getting up
• Rolling or thrashing
• Depression, lethargy, isolation from herd
• Reduced or absent appetite
• Changes in drinking or urination

Physical Signs

• Increased heart rate (>44 beats per minute)
• Elevated respiratory rate
• Flared nostrils, sweating (especially in non-exertional contexts)
• Abdominal distension
• Reduced or absent gut sounds
• Decreased or absent fecal output

Pain Scoring Systems

The EAAPS has demonstrated good feasibility in referral hospitals and can be used without prior training [7]. A composite pain scale (CPS) incorporating physiological and behavioural parameters shows excellent inter-observer reliability and correlates with serum cortisol concentrations, providing physiological validation of pain assessment [37]. Automated detection using accelerometers and artificial intelligence (AI) can now identify early colic signs with over 91% accuracy, offering promise for continuous monitoring [2, 4].

Emergency Response: What to Do When Colic Strikes

When a horse shows signs of colic, prompt action can be life-saving.

Initial Steps

1. Remove food and water to prevent further distension or aspiration.
2. Assess vital parameters: heart rate, respiratory rate, mucous membrane colour, capillary refill time, and rectal temperature.
3. Monitor behaviour and note the frequency and severity of pain episodes.
4. Do not administer any medication without veterinary guidance, as some drugs (e.g., flunixin meglumine) can mask signs and complicate diagnosis.

When to Call the Veterinarian

Any horse showing signs of colic should be evaluated by a veterinarian. The decision for referral to a surgical facility depends on the severity of clinical signs, failure to respond to medical therapy, and specific findings such as nasogastric reflux, abnormal rectal palpation, or elevated blood lactate [20, 48]. In first-opinion ambulatory practice, fast localized abdominal sonography (FLASH) using portable wireless ultrasound can detect abnormalities like distended small intestine, thickened walls, and gastric distension, aiding in timely referral decisions [14].

Transport Considerations

If referral is indicated, the horse should be transported carefully to minimize stress and further injury. The AAEP recommends keeping the horse calm, providing a well-bedded trailer, and avoiding sudden stops or sharp turns.

Diagnosis at the Clinic

Upon arrival at a referral hospital, a systematic diagnostic approach is undertaken:

• Physical examination: Heart rate, respiratory rate, mucous membranes, auscultation of gut sounds, and rectal palpation.
• Nasogastric intubation: To check for gastric reflux and decompress the stomach.
• Abdominal ultrasonography: Transabdominal and transrectal ultrasound can identify small intestinal distension, thickening, peritoneal fluid, and specific lesions such as nephrosplenic entrapment [25, 42].
• Bloodwork: Packed cell volume (PCV), total protein, lactate, glucose, and electrolytes are key indicators. Elevated lactate and PCV are associated with strangulating lesions and poorer prognosis [13, 22, 55]. Hyperglycaemia and hyperlactataemia are strong markers of severity [13].
• Peritoneal fluid analysis: Sampling via abdominocentesis can reveal increased protein, white blood cells, or bacteria, indicating peritonitis or intestinal compromise.
• Heart rate variability (HRV): Reduced HRV at admission is associated with non-survival in colic horses, providing additional prognostic information [43].

Treatment Options

Medical Management

Most colic cases (approximately 90%) are managed medically. Treatment includes:

• Analgesics: Non-steroidal anti-inflammatory drugs (NSAIDs) such as flunixin meglumine are the cornerstone, used in over 85% of cases [11]. Opioids like butorphanol are added for more severe pain, but long-term morphine administration (>24 h) increases the risk of post-anaesthetic colic [1]. Hydromorphone does not appear to increase colic risk [8].
• Fluid therapy: Intravenous or enteral fluids to correct dehydration and promote intestinal transit.
• Laxatives and lubricants: Mineral oil or psyllium for impactions.
• Antispasmodics: Buscopan (hyoscine butylbromide) for spasmodic colic [11].
• Gastric decompression: Via nasogastric tube to relieve distension.

Surgical Intervention

Approximately 10% of colic cases require exploratory celiotomy. Indications include:

• Severe, unrelenting pain
• Nasogastric reflux
• Abnormal rectal or ultrasound findings suggestive of strangulation or displacement
• Failure to respond to medical therapy

Short-term survival rates after colic surgery range from 68.5% to 79.1%, with about 80% of horses surviving anaesthesia [16, 51]. Factors associated with poorer prognosis include elevated PCV at admission, low total plasma protein after surgery, poor body condition, and longer surgery duration [16]. Post-operative complications such as incisional infection can be reduced with medical grade honey applied intra-incisionally [33] or with protective stent bandages [45].

Post-operative Care and Rehabilitation

After surgery, horses require intensive monitoring for recurrent colic, ileus, and infection. Core abdominal rehabilitation exercises (CARE) performed post-operatively are safe and associated with faster return to training and improved performance [53]. Long-term survival to one year after discharge is approximately 86%, and most horses return to their prior athletic function [51].

Prevention: Reducing the Risk of Colic

Prevention is the most effective strategy. Multiple risk factors have been identified, many of which are modifiable.

Diet and Feeding Management

• Consistency: Avoid sudden changes in feed or hay type. A recent change in diet is one of the strongest risk factors for colic [28, 54].
• Forage quality: Provide high-quality, dust-free hay. Feeding haylage has been associated with increased colic risk in crib-biting horses [19].
• Concentrate feeding: Limit grain meals to no more than 0.5% of body weight per feeding. High-grain diets are associated with colic [26].
• Water access: Ensure constant access to clean, fresh water. Reduced water intake is a risk factor for impaction colic [26].
• Sand ingestion: Avoid feeding on sandy soil; use hay feeders or mats. Regular psyllium supplementation may help reduce sand accumulation.

Parasite Control

Regular faecal egg count monitoring and targeted anthelmintic treatment are essential. Horses not receiving regular deworming have a higher risk of colic, but administration of anthelmintics within the past week can also be a risk factor, possibly due to die-off of parasites causing temporary inflammation [28]. A strategic deworming program reduces colic incidence [50].

Dental Care

Regular dental examinations and floating (correction of sharp enamel points) are important. Dental disease is a significant risk factor for colic, likely due to improper chewing and subsequent impaction [26].

Stable and Turnout Management

• Turnout: Horses kept at pasture have a lower risk of colic compared to those stabled full-time [28].
• Exercise: Regular exercise is protective; sudden changes in activity level increase risk [54].
• Stabling: Avoid prolonged confinement. Increased duration of stabling during autumn is a risk factor for colic in crib-biting horses [19].

Recognizing High-Risk Individuals

Horses with a history of colic, previous abdominal surgery, or crib-biting/windsucking behaviour are at increased risk [19, 28, 54]. Arabian horses may also have a higher predisposition [28]. For horses with recurrent colic, diagnostic workup including duodenal and rectal biopsies may reveal underlying inflammatory bowel disease [29].

Microbiome Health

Emerging research suggests that disturbances in the gut microbiome may contribute to colic, though it remains unclear whether these changes are a cause or consequence [6]. Prebiotics that promote beneficial bacteria such as Akkermansia muciniphila show promise for maintaining gut health and reducing inflammation, but controlled equine studies are needed [3].

Preventive Surgery

For horses with recurrent nephrosplenic entrapment, laparoscopic closure of the nephrosplenic space significantly decreases the incidence of recurrent colic and eliminates further entrapment episodes [10].

Prognosis and Long-Term Outcome

The prognosis for colic depends on the underlying cause, speed of intervention, and availability of advanced care. For medical colic, the survival rate is excellent. For surgical cases, short-term survival (to discharge) is approximately 70-80%, and long-term survival (to one year) is around 86% [16, 51]. Predictive models using clinical variables such as PCV, lactate, and glucose can help guide decision-making, but their accuracy varies across populations [24, 30]. Artificial intelligence models are being developed to predict the need for surgery and survival likelihood with up to 85% accuracy [32].

Owners should be aware that even after successful treatment, horses may experience recurrent colic episodes. In one study, 60% of horses that returned home after colic surgery had at least one recurrence during the first year [35]. However, with appropriate management and rehabilitation, most horses return to their previous level of performance [35, 51].

Conclusion

Colic remains a complex and potentially life-threatening condition in horses, but with vigilant observation, prompt veterinary care, and proactive prevention, many cases can be managed successfully. Early recognition of pain using validated scoring systems, coupled with advances in diagnostic imaging and AI-based monitoring, offers new opportunities to improve outcomes [2, 4, 7]. By understanding the types of colic, knowing how to respond in an emergency, and implementing evidence-based prevention strategies, horse owners and veterinarians can work together to reduce the incidence and impact of this devastating condition.

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