34th Annual Scientific Meeting proceedings

Geriatric horses are an increasing proportion of the equine population.   Estimates suggest that the percentage of horses > 20 years of age have increased from approximately 5% of the horse population in 1998 to over 11% in 2015.¹ This change has been attributed to improvements in veterinary care, husbandry, and management, and evolution of the human-horse relationship whereby horses are more often seen as companions and family members.  Colic is the most common reason for veterinary visits for most geriatric horse populations,^2,3 and age has been associated with reduced survival in several colic studies.^3,4  Age has also been associated with increased likelihood of developing of certain complications following colic surgery.^5,6  Since owners consider veterinarians to be trusted advisors to aid decision-making in emergency situations, it is important to understand the expectations and prognosis for geriatric horses following colic surgery.

Geriatric horses are empirically thought to be more stoic and demonstrate fewer outward signs of clinical illness, although this impression has not been proven in clinical studies.⁷  Geriatric horses presenting with colic are more likely to be moderately to severely painful and are more likely to have absent borborygmi than non-geriatric horses.⁷  Peritoneal total protein was also higher when measured in geriatric horses compared to non-geriatric horses.⁷  This was considered to support that geriatric horses had more severe gastrointestinal disease than non-geriatric horses, despite no significant differences in heart rate, hematocrit, creatinine, or lactate between geriatric and non-geriatric colic populations.^7-10  Admission rectal temperature was lower and blood total protein was higher in geriatric horses undergoing surgery than non-geriatric horses undergoing surgery.⁹  The etiology of this more severe gastrointestinal disease is typically strangulating small intestinal disease, which is particularly prevalent in geriatric horse populations.^3,8,9,11  Large colon lesions are less common in geriatric horses.⁷  In addition to age predispositions with different types of colic, there are breed differences in geriatric vs non-geriatric horse populations.  Arabians, Arabian-type horses, and ponies are over-represented in geriatric horse populations and Thoroughbreds are more common in non-geriatric horse populations.^8,9

When the treatment options are evaluated for geriatric horses compared to non-geriatric horses, it is found that geriatric horses are more likely to be euthanized without surgery or to be euthanized in surgery than non-geriatric horses.^3,11  This is attributed to the increased need for surgery in geriatric horses with colic and the higher cost associated with strangulating small intestinal lesions, which are more prevalent in geriatric horses.^3,4,11  If recovered from anesthesia, geriatric horses have similar short-term outcomes as non-geriatric horses for colic surgery, regardless of if procedures such as jejunojejunostomy, jejunoileostomy, or jejunocecostomy were performed.^3,9,11-13  However, when evaluating other types of colic, geriatric horses appeared to have lower survival rates for large colon simple obstructions¹¹ and idiopathic colic⁸ compared to non-geriatric horses.  The reason for this difference is not entirely clear, although it was observed that geriatric horses in the idiopathic colic category had higher blood lactate, higher hematocrit, and more band neutrophils than non-geriatric horses, suggesting a high degree of critical illness.⁸ Coincidentally, geriatric horses with colitis were found to have lower odds of survival than non-geriatric horses.¹⁰

When evaluating short-term postoperative recoveries and complications, many of the apparent differences between geriatric and non-geriatric horses in their recoveries are eliminated when controlled for lesion category.^9,12  Although age has been associated with development of post-operative reflux in some studies,^5,6 in more recent studies, development of post-operative reflux or high volume post-operative reflux was not associated with age or geriatric vs non-geriatric horses.^9,12  There are some postoperative findings that do differ.  Inappetance and duration of tachycardia (heart rate > 50 beats/minute) appear to be more common in geriatric horses than non-geriatric horses.⁹  Peak rectal temperature was associated with outcome for geriatric horses, whereas peak heart rate, duration of tachycardia, peak rectal temperature, duration of fever, peak hematocrit, lowest total protein, and lowest WBC count were associated with outcome for non-geriatric horses.⁹  Development of complications appeared to more impactful on outcome for non-geriatric horses than geriatric horses,⁹ although this was likely partially attributable to lack of power.  Complications associated with a poorer prognosis for geriatric horses were high fever (>39.4°C), incision complications, and laminitis, whereas complications associated with a poorer prognosis for non-geriatric horses were post-operative reflux, high fever (>39.4°C), diarrhea, leukopenia, laminitis, colic, and repeat laparotomy.⁹

When collating the results of these studies together, geriatric horses have a higher prevalence of strangulating small intestinal disease than non-geriatric horses.  Therefore, early referral to a surgical facility is advised to facilitate surgical treatment if possible.  If surgery is indicated, multiple studies indicate that geriatric horses can recover from colic surgery, even complicated surgeries, with similar prognoses to non-geriatric horses.  Clinical workups should be detailed, because initial clinical findings may underestimate the severity of intestinal injury.  For seemingly simple colics, such as large colon obstructions and idiopathic colic, a thorough workup, including hematology, should be pursued to evaluate for signs of clinical compromise and critical illness.  Hyperthermia responses appear to be blunted in geriatric horses, so elevated rectal temperatures may reflect a higher inflammatory response in geriatric horses than that same temperature in non-geriatric horses.^9,10 Geriatric horses may benefit from more supportive care, including appropriate analgesia, proactive nutritional support to prevent negative energy balance, and attentive nursing care to stimulate appetite.⁹ 

Long-term survival studies are complicated by the increasing mortality rates from other infirmities of old age in geriatric horses as they become older.  Horses aged 15-20 years have a mortality rate of 4-6 horses per 100 horse years compared to 35-42 horses per 100 horse years for horses greater than 30 years of age with lameness and colic being the most common reasons for euthanasia.¹⁴  In one long-term survival study, it was found that geriatric horses had significantly shorter median survival times of 72 months compared to 122 months for non-geriatric horses; however, this difference was attributed to remaining lifespan in geriatric horses.¹³

References

1. Anon. Age-related trends in demographics of equids in the United States.  In: USDA/APHIS National Animal Health Monitoring System (NAHMS) Studies. 2015. https;//www.aphis.usda.gov/animal_health/nahms/equine/downloads/equine15/Equine15_is_TrendsAge.pdf.  Accessed 16 May 2025.
2. Brosnahan MM, Paradis MR.  Demographic and clinical characteristics of geriatric horses: 467 cases (1989-1999).  J Am Vet Med Assoc. 2003;223:93-98.
3. Krista KM, Kuebelbeck KL.  Comparison of survival rates for geriatric horses versus nongeriatric horses following exploratory celiotomy. J Am Vet Med Assoc. 2009;235:1069-1072.
4. Southwood LL, Dolente BA, Lindborg S, Russell G, Boston R.  Short-term outcome of equine emergency admissions at a university referral hospital.  Equine Vet J. 2009;41:459-464.
5. Holcombe SJ, Rodgriguez KM, Campbell JO, Chaney KP, Sparks HD.  Prevalence of and risk factors for postoperative ileus after small intestinal surgery in 233 horses.  Vet Surg. 2009;38:638-372.
6. Brown JA, Holcombe SJ, Southwood LL, Byron CR, Embertson RM, Hauptmann JG.  End-to-side versus side-to-side jejunocecostomy in horses: a retrospective analysis of 150 cases.  Vet Surg. 2015;44:527-533.
7. Southwood LL, Gassert T, Lindborg S.  Colic in geriatric compared to mature nongeriatric horses.  Part 1: retrospective review of clinical and laboratory data.  Equine Vet J. 2010;42:621-627.       
8. Silva AG, Furr MO.  Diagnoses, clinical pathology findings, and treatment outcome of geriatric horses: 345 cases (2006-2010).  J Am Vet Med Assoc. 2013;243:1762-1768.
9. Gazzerro DM, Southwood LL, Lindborg S.  Short-term complications after colic surgery in geriatric versus mature non-geriatric horses.  Vet Surg. 2015;44:256-264.
10. Sage SE, Bedenice D, McKinney CA, Long AE, Wagner B, Mazan MR, Paradis MR.  Assessment of the impact of age and of blood-derived inflammatory markers in horses with colitis.  J Vet Emerg Crit Care. 2021;31:779-787.
11. Southwood LL, Gassert T, Lindborg S.  Colic in geriatric compared to mature nongeriatric horses. Part 2: treatment, diagnosis and short-term survival. Equine Vet J. 2010;42:628-635.
12. Boorman S, Stefanovski D, Southwood LL.  Clinical findings associated with development of postoperative reflux and short-term survival after small intestinal surgery in geriatric and mature nongeriatric horses.  Vet Surg. 2019;48;795-802.
13. Rudnick MJ, Denagamage TN, Freeman DE.  Effects of age, disease and anastomosis on short- and long-term survival after surgical correction of small intestinal strangulating diseases in 89 horses. Equine Vet J. 2022;54:1031-1038.
14. McGowan CM, Ireland JL.  Welfare, quality of life, and euthanasia of aged horses.  Vet Clin Equine. 2016;32:355-367.