Diagnoses, clinical pathology findings, and treatment outcome of geriatric horses: 345 cases (2006–2010)

Adriana G. Silva Marion duPont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Leesburg, VA 20177.

Search for other papers by Adriana G. Silva in
Current site
Google Scholar
PubMed
Close
 MV, MS
and
Martin O. Furr Marion duPont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Leesburg, VA 20177.

Search for other papers by Martin O. Furr in
Current site
Google Scholar
PubMed
Close
 DVM, PhD, DACVIM

Click on author name to view affiliation information

Abstract

Objective—To compare clinical, clinical pathology, and outcome variables between geriatric and nongeriatric horses.

Design—Retrospective case-control study.

Animals—690 horses (345 horses ≥ 20 years old and 345 horses > 1 and < 20 years old) examined at a referral hospital.

Procedures—Medical records were examined, and data collected included horse description, diagnosis, outcome, and CBC and serum biochemical analysis results. Cases were horses ≥ 20 years old, and controls were horses > 1 and < 20 years old.

Results—Mean ± SD age was 23.9 ± 4.6 years for cases and 9.2 ± 3.6 years for controls. Arabian and pony breeds were significantly overrepresented in the geriatric group, compared with the control group. Diagnoses related to the digestive system, musculoskeletal system, and respiratory system were most common in this hospital population overall (cases and controls). Colic was the most common health problem overall. Digestive system disorders were significantly more prevalent among cases. Short-term survival rates for most categories of colic were no different for cases than for controls, with the exception of the category idiopathic colic. Considering all conditions, cases were significantly more likely to be nonsurvivors than were controls. Minor differences in serum biochemical results were found in some disease subcategories. Geriatric horses with colic were not more commonly euthanized than were adult nongeriatric horses.

Conclusions and Clinical Relevance—Results indicated that in this population of horses in a referral hospital, age was associated with the prevalence of specific disease conditions. Few differences between cases and controls were found in serum biochemical values.

Abstract

Objective—To compare clinical, clinical pathology, and outcome variables between geriatric and nongeriatric horses.

Design—Retrospective case-control study.

Animals—690 horses (345 horses ≥ 20 years old and 345 horses > 1 and < 20 years old) examined at a referral hospital.

Procedures—Medical records were examined, and data collected included horse description, diagnosis, outcome, and CBC and serum biochemical analysis results. Cases were horses ≥ 20 years old, and controls were horses > 1 and < 20 years old.

Results—Mean ± SD age was 23.9 ± 4.6 years for cases and 9.2 ± 3.6 years for controls. Arabian and pony breeds were significantly overrepresented in the geriatric group, compared with the control group. Diagnoses related to the digestive system, musculoskeletal system, and respiratory system were most common in this hospital population overall (cases and controls). Colic was the most common health problem overall. Digestive system disorders were significantly more prevalent among cases. Short-term survival rates for most categories of colic were no different for cases than for controls, with the exception of the category idiopathic colic. Considering all conditions, cases were significantly more likely to be nonsurvivors than were controls. Minor differences in serum biochemical results were found in some disease subcategories. Geriatric horses with colic were not more commonly euthanized than were adult nongeriatric horses.

Conclusions and Clinical Relevance—Results indicated that in this population of horses in a referral hospital, age was associated with the prevalence of specific disease conditions. Few differences between cases and controls were found in serum biochemical values.

Geriatric horses represent a substantial proportion of the equine population, and information regarding the health and care of this cohort has been the focus of several recently published articles.1–10 There is cumulative evidence that increased numbers of older horses are evaluated at referral hospitals for treatment.11–13 In a large retrospective postmortem study14 of geriatric horses (≥ 15 years old), most diagnoses were associated with the digestive system, musculoskeletal system, and reproductive system as well as various types of neoplasia, with strangulating lipoma, laminitis, and pituitary adenoma being the most common specific diseases. Furthermore, survival rate in geriatric horses treated for colic has been reported to be lower than that for nongeriatric horses.10,15 Information is limited, however, regarding risk for a variety of conditions. Furthermore, serum biochemical values in geriatric horses are not commonly reported, and it is unknown how they may differ from those of adult nongeriatric horses in different conditions or influence prognosis and treatment. In addition, senescence of the immune system response has been well documented in geriatric animals, and it has been proposed that this may lead to increased risk of infectious disease and poor response to conditions such as sepsis or systemic inflammatory response syndrome.16–18

Although information regarding disease prevalence and overall survival rates for geriatric horses is increasing, only a few case-control studies are reported in the literature. Additional information on diagnoses and outcomes in the geriatric population will be beneficial for veterinarians treating older horses and provide owners with more accurate advice concerning treatment and prognosis. The purpose of the study reported here was to compare clinical, clinical pathology, and outcome variables between geriatric and nongeriatric horses admitted to a referral teaching hospital. A secondary goal was to determine whether geriatric horses with colic were more commonly euthanized, compared with adult nongeriatric horses.

Materials and Methods

Selection of cases and controls—Electronic medical records were searched to identify horses ≥ 20 years of age at the time of treatment (cases) admitted to the Marion DuPont Scott Equine Medical Center between August 2006 and September 2010. As each case was identified, the next nongeriatric horse (< 20 years of age at the time of treatment), on the basis of computer accession number, was identified as a control. By this procedure, cases and controls were matched for date of recruitment to avoid any bias with respect to temporal changes in clinical practice. Horses were excluded from analysis if they were admitted for euthanasia only, if they were < 1 year of age at the time of treatment, or if the medical record was unavailable or missing core data (eg, age). Furthermore, horses admitted to the hospital that did not have a medical disorder (eg, mares admitted with sick foals) were excluded, and the next admitted horse that met inclusion criteria was enrolled. Horses that were euthanized for solely economic reasons were excluded from outcome analysis.

Medical records review—Age, sex, breed, clinical pathology results, and outcome were recorded for all horses. For each horse, the final diagnosis and organ system affected were recorded. Among horses with colic, diagnoses were classified as enteritis, strangulating or nonstrangulating large intestine displacements, small intestine strangulating lesions, or impactions (large or small colon). If a specific colic diagnosis could not be conclusively established, the diagnosis was coded as idiopathic colic. Clinical pathology data recorded included results of a CBC and serum biochemical analysis obtained within 24 hours after admission. Age was recorded as reported by the owner or horse caretaker.

Outcome was defined as survival to hospital discharge or nonsurvival (died or euthanized). When possible, the reason for euthanasia (poor prognosis, financial constraints, or both) was recorded. To achieve the secondary goal, which was to determine whether elective euthanasia was more common in geriatric horses, those horses that were euthanized without recommended treatment being performed were removed, and the outcome analysis was repeated. Horses considered not treated included those euthanized during surgery because of poor prognosis or anticipated treatment expense, horses euthanized at admission after examination, or those euthanized without surgical exploration if that had been recommended. Horses with evidence of gastrointestinal tract rupture at the time of examination or surgery were not excluded from initial data analysis because this condition is considered fatal.

Statistical analysis—Data were entered into a desktop computer spreadsheet for analysis with commercial statistical analysis software.a Continuous data were summarized and reported as mean ± SD, median, and range values, and categorical data were summarized as proportions. Continuous data were analyzed by use of the Student t test after confirmation that the data were normally distributed by examination of a plot of the residuals. Dichotomous data (eg, survived vs did not survive and disease condition present vs absent) were compared by means of χ2 analysis. Associations were expressed as ORs determined by use of standard formulas from contingency tables and reported as the odds for cases, compared with controls. Not all data were available for all horses in the study.

The association of age with the presence of various disease conditions (eg, colic or neoplasia) was analyzed by use of logistic regression. The ORs were obtained by exponentiation of the coefficients of the logistic regression models; 95% CIs for ORs were obtained with maximum likelihood methods. A value of P < 0.05 was considered significant for all analyses.

Results

The study included 690 horses, of which 345 were cases (≥ 20 years of age) and 345 were controls (< 20 years of age) at the time of hospital treatment. Mean ± SD age of the cases was 23.9 ± 4.6 years (range, 20 to 36 years), and that of the controls was 9.2 ± 3.6 years (range, 1 to 18 years). Among the controls, there were 122 (35%) females, 198 (57%) geldings, and 26 (8%) stallions; among the cases, there were 140 (40%) females, 202 (59%) geldings, and 3 (1%) stallions. These were considered either male or female for analysis, and there was no difference in sex distribution among the horses of the study (P = 0.150). Forty-eight breeds were reported; for analysis, these were grouped into categories of draft, pony, Arabian and Arabian type, Quarter Horse and Quarter Horse type, Thoroughbred, and warmblood. Among the controls, there were 10 (3%) Arabian and Arabian types, 18 (5%) draft horses, 17 (5%) ponies, 80 (23%) Quarter Horse and Quarter Horse types, 130 (38%) Thoroughbreds, and 90 (26%) warmbloods. Among the cases, there were 44 (13%) Arabians and Arabian types, 13 (4%) draft horses, 32 (9%) ponies, 120 (35%) Quarter Horse and Quarter Horse types, 107 (31%) Thoroughbreds, and 29 (8%) warmbloods. The distribution of breed type differed between the 2 study groups (P < 0.001), with 4.4 times as many Arabian and Arabian-type horses and 1.8 times as many ponies in the case group.

One hundred sixty-two diagnoses were recorded, and the body system affected (cardiovascular, endocrine, digestive, genitourinary, hematopoietic, hepatic, integumentary, musculoskeletal [excluding laminitis], nervous, respiratory, special senses [including eye and ear], and lymphoreticular) was also recorded (Table 1). Nine horses in the control group and 1 horse in the case group were not assigned a diagnosis or body system because the recorded diagnosis was fever of unknown origin or multisystemic disease in which the primary body system could not be identified. These horses were included in analysis of overall outcome, but they were removed from analysis of outcome or ORs for specific body systems.

Table 1—

Distribution (number [%]) and ORs of horses with (yes) or without (no [referent category]) primary diseases of various body systems; horses were > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases).

Body systemControlsCasesOR (95% CI)P value
Cardiovascular   0.492
 No329 (98)334 (97)1 
 Yes7 (2)10 (3)1.41 (0.53–3.74) 
Endocrine   0.620
 No334 (99)343 (100)1 
 Yes2 (1)1 (0)0.49 (0.04–5.4) 
Digestive   0.001
 No229 (68)193 (56)1 
 Yes107 (32)151 (44)1.67 (1.22–2.29) 
Genitourinary   0.410
 No322 (96)325 (94)1 
 Yes14 (4)19 (6)1.34 (0.66–2.73) 
Hematopoietic   0.999
 No335 (100)342 (99)1 
 Yes1 (0)2 (1)1.96 (0.18–21.70) 
Hepatic   0.068
 No335 (100)328 (98)1 
 Yes1 (0)6 (2)6.13 (0.74–51.18) 
Integument   0.170
 No320 (95)319 (93)1 
 Yes16 (5)25 (7)1.57 (0.82–2.99) 
Musculoskeletal   < 0.001
 No207 (62)270 (78)1 
 Yes129 (38)74 (22)0.44 (0.14–0.62) 
Nervous   0.157
 No324 (96)338 (98)1 
 Yes12 (4)6 (2)0.48 (0.18–1.29) 
Respiratory   0.477
 No304 (91)325 (95)1 
 Yes31 (9)19 (5)0.55 (0.31–1.00) 
Special senses   0.067
 No321 (96)317 (92)1 
 Yes15 (4)27 (8)1.82 (0.95–3.49) 
Multisystemic  NANA
 No336 (100)343 (100)  
 Yes0 (0)1 (0)  
Lymphoreticular  NANA
 No336 (100)341 (99)  
 Yes0 (0)3 (1)  

NA = Not applicable.

The most common body systems affected were the digestive (258/680 [38%]), musculoskeletal (203/680 [30%]), and respiratory (51/680 [8%]) systems. Less commonly observed were diseases of the cardiovascular (17/680 [3%]), endocrine (3/680 [< 1%]), genitourinary (33/680 [5%]), hematopoietic (3/680 [< 1%]), hepatic (7/680 [1%]), integumentary (41/680 [6%]), nervous (18/680 [3%]), special senses (42/680 [6%]), and lymphoreticular (3/680 [< 1%]) systems. Digestive system disorders were significantly (P = 0.001) more common in the case group. Conversely, cases were less likely (P < 0.001) to be evaluated for musculoskeletal disorders, compared with controls.

Colic was the most common digestive system abnormality as well as the most common health problem overall. Two hundred twenty-six of 690 (33%) horses had a primary diagnosis of colic. Of these, 134 (59%) horses were cases, whereas 92 (41%) were controls (OR, 1.75; 95% CI, 1.26 to 2.41; P < 0.001). Risk of colic increased by 1.04 (95% CI, 1.02 to 1.06) for each year of increasing age. Twenty-five diagnoses were recorded for these horses; however for purposes of analysis, the diagnoses were grouped into categories of idiopathic colic, enteritis (including both large and small intestine), impaction (large or small colon), nonstrangulating displacements of the large intestine, strangulating displacements of the large intestine, and strangulating disorders of the small intestine (eg, volvulus, strangulating lipoma, and epiploic foramen entrapment). Cases were 2.57 times as likely (95% CI, 1.19 to 5.54; P = 0.015) to have a strangulating lesion of the small intestine and less likely to have a strangulating lesion of the large intestine (OR, 0.26; 95% CI, 0.09 to 0.76; P = 0.009), compared with controls (Table 2).

Table 2—

Distribution (number [%]) and ORs of horses with (yes) or without (no [referent category]) specific colic diagnoses; horses were > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases).

DiagnosisControlsCasesOR (95% CI)P value
Idiopathic colic   0.840
 No50 (54)71 (53)1 
 Yes42 (46)63 (47)1.06 (0.62–1.79) 
Enteritis   0.374
 No78 (85)119 (89)1 
 Yes14 (15)15 (11)0.70 (0.65–3.11) 
Impaction   0.588
 No81 (88)121 (90)1 
 Yes11 (12)13 (10)0.79 (0.53–2.89) 
LI nonstrangulating displacement   0.741
 No89 (97)128 (95)1 
 Yes3 (3)6 (5)1.39 (0.34–5.71) 
LI strangulating displacement   0.009
 No80 (87)129 (96)1 
 Yes12 (13)5 (4)0.26 (0.09–0.76) 
SI strangulating lesion   0.015
 No82 (89)102 (76)1 
 Yes10 (11)32 (24)2.57 (1.19–5.54) 

LI = Large intestine. SI = Small intestine.

Diagnoses for horses that were evaluated for digestive system conditions other than colic included inflammatory bowel disease (1 control), dental disease (2 controls and 3 cases), parotid salivary gland disease (2 controls), malabsorption-hypoproteinemia (3 controls), peritonitis (1 control and 3 cases), esophageal obstruction (10 cases), and abdominal neoplasia (1 case).

Two hundred three of 690 (29%) horses were admitted for evaluation of musculoskeletal conditions. Of these, 129 (63%) were controls and 74 (36%) were cases; the smaller number of cases was significant (OR, 0.44; 95% CI, 0.31 to 0.62; P < 0.001). Diagnostic categories were defined as fractures, osteoarthritis and synovitis, navicular disease, soft tissue degenerative disorders (including desmitis and tendonitis), foot disorders excluding laminitis, nonspecific lameness, and laminitis. There was no significant difference between groups regarding the number of specific disorders (Table 3).

Table 3—

Distribution (number [%]) and ORs of horses with (yes) or without (no [referent category]) specific musculoskeletal system diagnoses; horses were > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases).

DiagnosisControlCasesOR (95% CI)P value
Fracture   0.633
 No337 (98)335 (97)1 
 Yes8 (2)10 (3)1.25 (0.49–3.22) 
Osteoarthritis-synovitis   0.076
 No323 (94)333 (97)1 
 Yes22 (6)12 (3)0.53 (0.26–1.09) 
Navicular syndrome   0.203
 No338 (98)342 (99)1 
 Yes7 (2)3 (1)0.42 (0.11–1.65) 
Desmitis-tendonitis   0.126
 No321 (93)331 (96)1 
 Yes23 (7)14 (4)0.59 (0.29–1.17) 
Foot lameness   0.311
 No335 (97)339 (98)1 
 Yes10 (3)6 (2)0.59 (0.21–1.64) 
Laminitis   0.999
 No339 (98)339 (98)1 
 Yes6 (2)6 (2)1.00 (0.32–3.13) 
Nonspecific lameness   < 0.001
 No317 (92)341 (99)1 
 Yes28 (8)4 (1)0.13 (0.04–0.05) 

Disease of the respiratory system was diagnosed in 9% (31/345) of controls and 5% (19/345) of cases. This difference was not significant (OR, 0.55; 95% CI, 0.31 to 1.00; P = 0.477). Specific diagnoses in cases included disease of the lower portion of the airway (n = 7), dorsal displacement of the soft palate (1), arytenoid chondritis–granuloma (2), exercise-induced epistaxis (1), ethmoid hematoma (2), interstitial pneumonia (1), neoplasia of a lung (1) neoplasia of a nostril (1), and sinus disease (3). Specific diagnoses in controls included disease of the lower portion of the airway (n = 5), laryngeal malformations and hemiplegia (6), nonspecific suppurative discharge (3), dorsal displacement of the soft palate (2), arytenoid chondritis–granuloma (4), ethmoid hematoma (3), pneumonia-pleuritis (6), and sinus disease (2). Because of the small number in each diagnostic category, specific ORs were not calculated for each diagnosis. Notably, however, laryngeal disease, including malformations and hemiplegia, was diagnosed only in the controls, and neoplasia associated with the respiratory system was observed only in the cases.

Among the cases, the 6 most common specific diagnoses included neoplasia (n = 33 [10%]), strangulating lipoma of the small intestine (27 [8%]), arthritis (12 [4%]), corneal ulcer (11 [3%]), esophageal obstruction (10 [3%]), and gastric ulcers (10 [3%]). Neoplasia, excluding lipoma, was diagnosed in 1% of the controls (3/345) and 9% (33/345) of the cases, resulting in an OR of 12.06 (95% CI, 3.66 to 39.68; P < 0.001). The probability of a diagnosis of neoplasia increased 1.14/y of increasing age. Specific diagnoses of neoplasia in cases included melanoma (n = 11), squamous cell carcinoma (11), lymphoma (2), adenocarcinoma (2), osteosarcoma (1), and unknown types (6). In the control group, 2 horses had squamous cell carcinoma of the cornea, and 1 had skin melanomas. Specific ORs were not calculated for each diagnosis because of the small numbers in each category.

Serum biochemical values for each group across all diagnoses (Table 4) and CBCs for each group (Table 5) were determined. Among horses with colic, blood lactate concentration was significantly (P = 0.024) higher in cases than controls (1.58 vs 4.09 mmol/L) in the idiopathic colic category only. In addition, Hct was higher in cases with idiopathic colic (36.5 vs 41.9%; P = 0.013), as was the band neutrophil count (60.7 vs 195.2 cells/μL; P = 0.021). In cases with impactions, total protein concentration was lower (6.45 vs 7.25 mg/dL; P = 0.041) than that of controls with impactions, and among horses with enteritis, the total WBC count was higher (9,958.6 vs 6,382.4 cells/μL; P = 0.032) in cases.

Table 4—

Serum biochemical variables for horses (No. = number of horses) > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases).

 ControlsCases 
VariableNo.Mean ± SDRangeNo.Mean ± SDRangeP value
Sodium (mmol/L)136135.1 ± 3.9121–144193136.0 ± 0.5125–1540.030
Potassium (mmol/L)1353.6 ± 0.52.4–5.11913.7 ± 0.51.9–5.70.724
Chloride (mmol/L)136102.2 ± 4.689–114193102.5 ± 4.489–1150.543
Glucose (mg/dL)135139.7 ± 56.276–386190152.5 ± 67.743–4860.072
BUN (mg/dL)13219.6 ± 11.94–10419220.6 ± 11.51.2–1000.448
Creatinine (mg/dL)1351.8 ± 3.30.7–381921.8 ± 1.10.7–9.60.831
Total protein (g/dL)1746.7 ± 0.93–11.32037.0 ± 1.21.9–12.50.001
Albumin (g/dL)673 ± 0.51–3.8953.0 ± 0.50.1–40.644
Globulin (g/dL)673.4 ± 1.11.6–9.5953.9 ± 0.21.8–11.10.004
Calcium (mg/dL)6610.1 ± 17.3–129810.5 ± 0.96.5–13.60.009
Phosphorus (mg/dL)672.9 ± 1.40.4–7.4952.6 ± 1.10.7–7.10.128
Magnesium (mg/dL)1341.4 ± 1.20.7–14.71771.3 ± 0.30.6–2.70.158
Total bilirubin (mg/dL)673.1 ± 3.10.4–24.1962.6 ± 1.50.3–9.70.196
LDH (U/L)67281.5 ± 169101–1,09695356.9 ± 5293.9–4,9300.262
Alkaline phosphatase (U/L)67168.8 ± 13561–83796175.8 ± 120.769–8590.737
Aspartate aminotransferase (U/L)67323.9 ± 463.6124–3,95095265.5 ± 145.762–1,1900.252
Creatine kinase (U/L)68561.2 + 1,338.90–9,36095636.7 ± 977.752–5,2490.678
γ-Glutamyltransferase (U/L)6618.8 ± 19.34–149525.8 ± 53.45–466.00.308
Triglycerides (mg/dL)6660.1 ± 7314–3449593.2 ± 131.97–8550.066
Lactate (mmol/L)982.8 ± 3.90.3–231403.7 ± 4.50.4–29.80.118

LDH = Lactate dehydrogenase.

Table 5—

Comparison of CBC values for horses > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases).

 ControlsCases 
VariableNo.Mean ± SDRangeNo.Mean ± SDRangeP value
WBCs (cells/μL)1768,679.5 ± 3,814.21,200–30,1002139,266.7 ± 4,937.3500.0–46,900.00.197
RBCs (×106 cells /μL)1758.3 ± 1.84.0–16.421113.1 ± 751–10970.356
Hemoglobin (g/dL)17513.6 ± 3.16.4–29.621114.2 ± 4.14.1–45.70.175
Hct (%)17637.7 ± 8.74–68.121739.0 ± 9.411.6–740.153
MCV (fL)17545.3 ± 3.635–5321148.3 ± 4.75.3–81< 0.001
MCH (pg/cell)17516.6 ± 2.813.1–4921117.5 ± 1.513.8–28.1< 0.001
MCHC (g/dL)17537.9 ± 24.817.5–36321137.6 ± 22.233.6–3580.869
Platelets (platelets/μL)93208,656.3 ± 83,886.635.8–741,000134195,522.4 ± 47,329.660,000–402,0000.135
Neutrophils (cells/μL)1735,954.3 ± 3,533.3288–28,5952126,952.9 ± 6,336.8161–80,3360.065
Band neutrophils (cells/μL)176126.6 ± 345.60–1,892213180.6 ± 428.50–28400.178
Lymphocytes (cells/μL)1742,299.1 ± 1,243.6448–9,4002122,186.3 ± 3,005.998–41,2720.643
Monocytes (cells/μL)176360.2 ± 292.50–1807213324.3 ± 265.30–16640.205
Eosinophils (cells/μL)17680.1 ± 1090–66021388.9 ± 138.10–9380.494
Fibrinogen (mg/dL)174296 ± 151100–1,300211312.3 ± 165100–1,0000.316

MCV = Mean corpuscular volume. MCH = Mean corpuscular hemoglobin. MCHC = Mean corpuscular hemoglobin concentration.

Among the controls, 4 horses were excluded from analysis because they were euthanized solely on financial grounds, leaving 341 horses for outcome analysis. Of these horses, 314 (92%) horses survived and 27 (8%) died or were euthanized. Among the cases, 10 were removed from analysis because they were euthanized solely on financial grounds. Of the 335 horses remaining, 271 (81%) survived and 64 (19%) did not survive. Overall, cases were significantly (P < 0.001) more likely to be nonsurvivors, compared with controls (OR, 2.74; 95% CI, 1.71 to 4.43). Regarding outcome for horses with colic, cases were significantly (P = 0.016) more likely to be nonsurvivors than were controls (OR, 3.37; 95% CI, 1.22 to 9.30). However, a significant difference between groups was found only for those with a diagnosis of idiopathic colic (Table 6).

Table 6—

Outcome (survival to hospital discharge [number {%} of horses]) and ORs by specific colic diagnoses among 213 horses > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases).

DiagnosisNonsurvivorsSurvivorsOR (95% CI)P value
Idiopathic colic   0.022
 Controls6 (21)34 (48)1 
 Cases22 (79)37 (52)3.37 (1.22–9.30) 
Enteritis   0.682
 Controls4 (57)10 (45)1 
 Cases3 (43)12 (55)0.62 (0.11–3.47) 
Impaction   0.999
 Controls1(33)9 (50)1 
 Cases2 (67)9 (50)2.00 (0.15–26.17) 
SI strangulating lesion   0.999
 Controls4 (27)6 (25)1 
 Cases11 (73)18 (75)1.09 (0.25–4.74) 
LI strangulating displacement   0.999
 Controls3 (75)8 (67)1 
 Cases1 (25)4 (33)0.67 (0.05–8.65) 
LI nonstrangulating displacement   NA
 Controls0 (0)3 (33)NA 
 Cases0 (0)6 (67)NA 

See Tables 1 and 2 for key.

On the assumption that there may have been selective treatment and euthanasia of horses with colic on the basis of age, the number of horses treated in each colic diagnosis group was evaluated and compared. Of 92 controls with colic, 77 (83%) were treated, and 15 (17%) were considered to have been euthanized without treatment. Among 131 cases with colic, 101 (77%) were treated, and 30 (23%) were considered to have been euthanized without treatment. Although the proportion of untreated horses was slightly greater among the cases, this did not achieve significance (OR, 1.52; 95% CI, 0.76 to 3.03; P = 0.227). When cases that had not received treatment prior to euthanasia were removed from the analysis, short-term outcome by diagnosis category did not change appreciably (Table 7). The OR for the risk of death among cases with idiopathic colic or large intestine strangulating displacement became somewhat larger, however. These results suggested that in this cohort of horses, there did not appear to be bias favoring outcome in the controls.

Table 7—

Outcome (survival to hospital discharge [number {%}]) and ORs by specific colic diagnoses among 180 horses > 1 to < 20 years of age (controls) or ≥ 20 years of age (cases) when nontreated horses were removed from the analysis.

DiagnosisNonsurvivorsSurvivorsOR (95% CI)P value
Idiopathic colic   0.037
 Controls1 (10)34 (48)1 
 Cases9 (90)37 (52)8.27 (0.99–68.96) 
Enteritis   0.682
 Controls4 (57)10 (45)1 
 Cases3 (43)12 (55)0.63 (0.11–3.48) 
Impaction   NA
 Controls09 (50)NA 
 Cases09 (50)NA 
SI strangulating lesion   0.645
 Controls2 (33)6 (25)1 
 Cases4 (67)18 (75)1.50 (0.22–10.36) 
LI strangulating displacement   0.385
 Controls08 (67)1 
 Cases1 (100)4 (33)1.25 (0.81–1.94) 
LI nonstrangulating displacement   NA
 Controls03 (33)NA 
 Cases06 (67)NA 

See Tables 1 and 2 for key.

Discussion

The medical care of geriatric horses has become a subject of increasing interest in recent years because the number of geriatric horses for which medical care is sought appears to be increasing.11 The definition of the term geriatric as it applies to horses has not been established, and different authors have used different ages, most commonly either > 15 or > 20 years of age. In the present study, geriatric was defined as ≥ 20 years of age. Ponies and Arabians or Arabian types were overrepresented in the geriatric group. On the basis of the authors’ clinical experience, this was not surprising, and it was consistent with findings in other reports.11,14 The OR for disease of the digestive system was substantially higher in geriatric horses, compared with controls. In this body system, colic was the major diagnosis.

Our findings were similar to other reports of digestive system disease, specifically colic, in geriatric horses. In horses >15 years of age, colic was reported in 8.7% and was responsible for 21% of the deaths.2 Our finding that geriatric horses had increased odds for colic was in agreement with results of a study11 in which colic was the most common health problem in horses ≥ 20 years of age, although another study4 reported no association between colic risk and increasing age. This disparity may be attributable to population and study design differences; we evaluated records of horses > 1 year of age admitted to a referral hospital, whereas in the latter study,4 a prospective cross-sectional survey was used to gather owner-reported information on horses > 15 years of age. Therefore, the prevalence of colic in our population was much higher than that of the general population, and there was a defined nongeriatric population included for comparison. It is possible that geriatric horses with colic were not referred because the owners did not wish to treat such aged horses. Selective treatment based on age is commonly observed in practice, and this observation is supported by the report of Southwood et al.10 If selective referral had occurred, however, our findings would have underestimated the risk for colic in the geriatric horses. Another potential bias in the study population was the possibility that owners of older horses might have had greater willingness to treat because of emotional attachment. This is purely speculative, however, and the data from this and other studies do not provide any insight into this possibility.

The effect of age on outcome from colic is difficult to determine because it is highly confounded by economic factors, considerations of future use, potential delayed referral of older horses, and the perception of both clients and veterinarians that old horses may not tolerate the procedures well. A recent study19 on the short-term outcome of equine emergency admissions found that horses ≥ 16 years were 2 to 3 times as likely to die or be euthanized as were adult nongeriatric horses. Survival in geriatric horses treated for colic has been reported to be lower than that for nongeriatric horses.10,15 In the present study, the survival rate of geriatric horses with idiopathic colic was less than that of mature nongeriatric horses; however, there was no difference in survival rate for other categories of colic. This was similar to the study of Southwood et al10 that also found no difference in survival rate of aged horses with small or large intestinal strangulating lesions. Although there was lower survival rate in geriatric horses, the authors indicated a potential for bias caused by the small number of horses that died in either category. The authors also indicated that there appeared to be a definite bias for not treating geriatric horses,10 which was similar to the findings of Krista et al.15 To evaluate that potential bias in the present study, the proportion of horses euthanized without receiving recommended treatment (including intraoperative euthanasia for anything other than gastrointestinal tract rupture) was examined, and there was no difference in the prevalence of elective euthanasia between geriatric and adult nongeriatric horses. It seems, therefore, that in this cohort of horses, the survival rate of geriatric horses with certain conditions was poorer than that of their nongeriatric counterparts. One explanation for this could be that the degree of illness in the geriatric and nongeriatric horses could have been different by the time they were evaluated for definitive treatment. In the present study, geriatric horses had higher blood lactate concentration, higher Hct, and more band neutrophils than did nongeriatric horses in the idiopathic colic category only. This finding suggested a greater severity of illness among the geriatric horses that might explain the poorer prognosis in the idiopathic colic category. It is unknown whether this resulted from delayed referral or differences in the individual horses’ physiologic responses to the illness.

In a study of horses examined in a hospital setting, respiratory tract disease was the third most common cause for examination11; this was also observed in the present study, in which there was a lower OR (0.55) for respiratory tract disease in geriatric than adult nongeriatric horses, although this difference was not significant. In addition, the nature of the specific diagnoses associated with the respiratory tract was not noticeably different between geriatric and nongeriatric horses, although small numbers precluded formal analysis.

In the present study, musculoskeletal disease was less commonly reported in the geriatric horses. This was unexpected because previous studies have found musculoskeletal disease to be more common in geriatric horses, which is consistent with our clinical experience. Lameness was the most common cause of euthanasia of geriatric horses in 1 study.2 However, although previous studies found a fairly high prevalence of musculoskeletal disease, they did not compare this directly with adult nongeriatric horses.2,11 The most likely explanation for the lower OR for musculoskeletal disease in the present study is that OR analysis was performed on data from horses admitted to a tertiary care referral hospital, with a high proportion of emergency and critical care cases; horses may not have been referred because of chronic degenerative disease. Among horses with musculoskeletal disease, there was no difference in prevalence among the different diagnostic categories.

Another somewhat unexpected finding of this study was that endocrine disease was not more common among older horses. The small number of horses with endocrine disease probably reflected the fact that the study horses were examined in a critical care hospital, and horses were not often referred for evaluation of this problem; evaluation of endocrine diseases most commonly takes place on the farm. Hence, we believe that this was likely a spurious finding reflecting the nature of the study population and hospital setting.

Substantial differences in clinical serum biochemical values between geriatric and younger adult horses were not observed in this study. Slightly higher values for serum globulin and calcium concentrations were found in the geriatric horses, but the values were within reference ranges for adult horses, so the importance of this finding is questionable. In addition, mean corpuscular volume and mean corpuscular hemoglobin concentration were significantly greater in the geriatric population, but these differences were modest, and values were within reference ranges for adult horses. These results were similar to those in other reports20,21 of hematologic variables in geriatric horses.

Advanced age is associated with altered immune function, including immunosenescence and enhanced inflammatory responses.16 Infectious diseases such as pneumonia and enteritis were not found more commonly in geriatric horses, and the short-term survival rate of horses with enteritis was not different between groups. In addition, WBC counts were not different between groups. Hence, it is likely that other factors have a more prominent role than immunosenescence in short-term survival rate associated with illness.

Weaknesses of the present study should be considered when interpreting the results. The most prominent shortcoming was that this was a retrospective study using examination of clinical records. Such studies are inherently limited by the completeness and accuracy of the data recorded. In a critical care hospital setting such as the one in which this study was conducted, the medical records are dominated by concerns associated with the primary problem that resulted in hospitalization. Secondary or chronic problems that were not the reason for the referral are often not well described or even noted in the clinical record. Second, this study reflected disease conditions in a group of horses referred for advanced care, which likely induced considerable bias for some conditions; some findings cannot be extrapolated to horses in other settings. Large-scale, multicenter prospective studies are necessary to further elucidate the associations between age and disease prevalence, treatment, and prognosis of older horses; however, it appears that age alone should not be a prominent factor in determining prognosis or directing treatment decisions in older horses.

ABBREVIATION

CI

Confidence interval

a.

SAS, version 9.2, SAS Institute Inc, Cary, NC.

References

  • 1. Adams AA, Madhu PK, Katepalli MP, et al. Effect of body condition, body weight and adiposity on inflammatory cytokine responses in old horses. Vet Immunol Immunopathol 2009; 127:286294.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Ireland JL, Clegg PD, McGowan CM, et al. Factors associated with mortality of geriatric horses in the United Kingdom. Prev Vet Med 2011; 101:204218.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Ireland JL, Clegg PD, McGowan CM, et al. A cross-sectional study of geriatric horses in the United Kingdom. Part 1: demographics and management practices. Equine Vet J 2011; 43:3036.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Ireland JL, Clegg PD, McGowan CM, et al. A cross-sectional study of geriatric horses in the United Kingdom. Part 2: health care and disease. Equine Vet J 2011; 43:3744.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. McGowan TW, Pinchbeck G, Phillips CJC, et al. A survey of aged horses in Queensland, Australia. Part 1: management and preventative health care. Aust Vet J 2010; 88:420427.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. McGowan TW, Pinchbeck G, Phillips CJC, et al. A survey of aged horses in Queensland, Australia. Part 2: clinical signs and owner's perceptions of health and welfare. Aust Vet J 2010; 88:465471.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. Ireland JL, Clegg PD, McGowan CM, et al. Disease prevalence in geriatric horses in the United Kingdom: veterinary clinical assessment of 200 cases. Equine Vet J 2012; 44:101106.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Ireland JL, McGowan CM, Clegg PD, et al. A survey of health care and disease in geriatric horses aged 30 years or older. Vet J 2012; 192:5764.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9. 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; 42:621627.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10. 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; 42:628635.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. Brosnahan MM, Paradis MR. Demographic and clinical characteristics of geriatric horses: 467 cases (1989–1999). J Am Vet Med Assoc 2003; 223:9398.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. McFarlane D, Sellon DC, Gibbs SA. Age-related quantitative alterations in lymphocyte subsets and immunoglobulin isotypes in healthy horses. Am J Vet Res 2001; 62:14131417.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13. Traub-Dargatz JL, Long RE, Bertone JL. What is an old horse and its recent impact? In: Bertone J, ed. Equine geriatric medicine and surgery. Philadelphia: WB Saunders Co, 2006; 14.

    • Search Google Scholar
    • Export Citation
  • 14. Williams N. Disease conditions in geriatric horses. Equine Pract 2000; 22(4):32.

  • 15. Krista KM, Kuebelbeck KL. Comparison of survival rates for geriatric horses versus nongeriatric horses following exploratory celiotomy for colic. J Am Vet Med Assoc 2009; 235:10691072.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16. Horohov DW, Adams AA, Chambers TM. Immunosenescence of the equine immune system. J Comp Pathol 2010; 142: S78S84.

  • 17. Adams AA, Breathnach CC, Katepalli MP, et al. Advanced age in horses affects divisional history of T-cells and inflammatory cytokine production. Mech Ageing Dev 2008; 129:656664.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. McFarlane D, Holbrook TC. Cytokine dysregulation in aged horses and horses with pituitary pars intermedia dysfunction. J Vet Intern Med 2008; 22:436442.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Southwood LL, Dolente BA, Lindborg S, et al. Short-term outcome of equine emergency admissions at a university referral hospital. Equine Vet J 2009; 41:459464.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. McFarlane D, Sellon DC, Gaffney D, et al. Hematologic and serum biochemical variables and plasma corticotropin concentration in healthy aged horses. Am J Vet Res 1998; 59:12471251.

    • Search Google Scholar
    • Export Citation
  • 21. Ralston SL, Nockels CF, Squires EL. Differences in diagnostic test results and hematologic data between aged and young horses. Am J Vet Res 1988; 49:13871392.

    • Search Google Scholar
    • Export Citation
  • 1. Adams AA, Madhu PK, Katepalli MP, et al. Effect of body condition, body weight and adiposity on inflammatory cytokine responses in old horses. Vet Immunol Immunopathol 2009; 127:286294.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 2. Ireland JL, Clegg PD, McGowan CM, et al. Factors associated with mortality of geriatric horses in the United Kingdom. Prev Vet Med 2011; 101:204218.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3. Ireland JL, Clegg PD, McGowan CM, et al. A cross-sectional study of geriatric horses in the United Kingdom. Part 1: demographics and management practices. Equine Vet J 2011; 43:3036.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 4. Ireland JL, Clegg PD, McGowan CM, et al. A cross-sectional study of geriatric horses in the United Kingdom. Part 2: health care and disease. Equine Vet J 2011; 43:3744.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 5. McGowan TW, Pinchbeck G, Phillips CJC, et al. A survey of aged horses in Queensland, Australia. Part 1: management and preventative health care. Aust Vet J 2010; 88:420427.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 6. McGowan TW, Pinchbeck G, Phillips CJC, et al. A survey of aged horses in Queensland, Australia. Part 2: clinical signs and owner's perceptions of health and welfare. Aust Vet J 2010; 88:465471.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 7. Ireland JL, Clegg PD, McGowan CM, et al. Disease prevalence in geriatric horses in the United Kingdom: veterinary clinical assessment of 200 cases. Equine Vet J 2012; 44:101106.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 8. Ireland JL, McGowan CM, Clegg PD, et al. A survey of health care and disease in geriatric horses aged 30 years or older. Vet J 2012; 192:5764.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 9. 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; 42:621627.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 10. 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; 42:628635.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 11. Brosnahan MM, Paradis MR. Demographic and clinical characteristics of geriatric horses: 467 cases (1989–1999). J Am Vet Med Assoc 2003; 223:9398.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 12. McFarlane D, Sellon DC, Gibbs SA. Age-related quantitative alterations in lymphocyte subsets and immunoglobulin isotypes in healthy horses. Am J Vet Res 2001; 62:14131417.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 13. Traub-Dargatz JL, Long RE, Bertone JL. What is an old horse and its recent impact? In: Bertone J, ed. Equine geriatric medicine and surgery. Philadelphia: WB Saunders Co, 2006; 14.

    • Search Google Scholar
    • Export Citation
  • 14. Williams N. Disease conditions in geriatric horses. Equine Pract 2000; 22(4):32.

  • 15. Krista KM, Kuebelbeck KL. Comparison of survival rates for geriatric horses versus nongeriatric horses following exploratory celiotomy for colic. J Am Vet Med Assoc 2009; 235:10691072.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 16. Horohov DW, Adams AA, Chambers TM. Immunosenescence of the equine immune system. J Comp Pathol 2010; 142: S78S84.

  • 17. Adams AA, Breathnach CC, Katepalli MP, et al. Advanced age in horses affects divisional history of T-cells and inflammatory cytokine production. Mech Ageing Dev 2008; 129:656664.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 18. McFarlane D, Holbrook TC. Cytokine dysregulation in aged horses and horses with pituitary pars intermedia dysfunction. J Vet Intern Med 2008; 22:436442.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 19. Southwood LL, Dolente BA, Lindborg S, et al. Short-term outcome of equine emergency admissions at a university referral hospital. Equine Vet J 2009; 41:459464.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 20. McFarlane D, Sellon DC, Gaffney D, et al. Hematologic and serum biochemical variables and plasma corticotropin concentration in healthy aged horses. Am J Vet Res 1998; 59:12471251.

    • Search Google Scholar
    • Export Citation
  • 21. Ralston SL, Nockels CF, Squires EL. Differences in diagnostic test results and hematologic data between aged and young horses. Am J Vet Res 1988; 49:13871392.

    • Search Google Scholar
    • Export Citation

Advertisement