Abstract
Objective—To determine how survival rates in geriatric horses (≥ 20 years old) undergoing abdominal exploratory surgery for colic compare with survival rates for younger (nongeriatric) horses.
Design—Retrospective case-control study.
Animals—56 geriatric horses and 487 nongeriatric horses undergoing exploratory celiotomy for colic.
Procedures—Medical records of all horses undergoing emergency abdominal exploratory surgery for primary gastrointestinal tract lesions over a 10-year period were reviewed. Data retrieved included signalment, primary gastrointestinal tract lesion, whether the horse was discharged from the hospital alive, and reason (if applicable) for euthanasia or death either during surgery or prior to hospital discharge. Survival rates were calculated and compared between the geriatric and nongeriatric populations for strangulating and nonstrangulating small intestinal, cecal, large colon, and small colon lesions. Information on long-term outcome was obtained via telephone contact with owners or referring veterinarians.
Results—Survival rate at the time of hospital discharge was 50% (28/56) for geriatric horses and 72% (352/487) for nongeriatric horses. Of horses that survived surgery and anesthetic recovery, 82% (28/34) of geriatric horses and 89% (352/396) of nongeriatric horses were discharged from the hospital alive. Seventy percent (14/20) of geriatric horses and 84% (108/129) of nongeriatric horses with long-term follow-up information survived > 1 year after surgery.
Conclusions and Clinical Relevance—Survival rate at the time of hospital discharge was significantly lower for geriatric horses, compared with that for nongeriatric horses. The primary reason for this difference in survival rates between the 2 groups appeared to be related to the significantly higher number of geriatric horses euthanized during surgery.
Although the survival rate for horses undergoing colic surgery has improved dramatically over the past several decades, emergency abdominal exploratory surgeries are still viewed with trepidation, especially by horse owners. Survival rates for exploratory celiotomy were 72% to 87.2% in 2 recent large retrospective studies1,2 and were dependent on many factors, including the lesion location and the presence of devitalized intestine. Horse age can be a major factor considered by owners in determining whether the patient is a suitable candidate for exploratory celiotomy. The purpose of the study reported here was to determine whether survival rates of geriatric horses undergoing colic surgery were comparable to survival rates for the remainder of our hospitalized population undergoing a similar procedure. Our hypothesis was that the geriatric population would have survival rates comparable to the nongeriatric population.
Materials and Methods
Case and control selection—Medical records of all horses undergoing emergency abdominal exploratory surgery for primary gastrointestinal lesions from January 1, 1997, to September 1, 2007, were reviewed. Geriatric (case) horses were ≥ 20 years old at the time of abdominal surgery; nongeriatric (control) horses were < 20 years old at the time of abdominal surgery.
Medical records review—Information obtained from the medical records included signalment, primary type of gastrointestinal lesion, and whether the horse was discharged from the hospital alive. Also obtained from the medical records were reasons for euthanasia or death during surgery or prior to hospital discharge. Information on long-term outcome was obtained by contacting owners or referring veterinarians via telephone and was classified as < 1 year or > 1 year.
Statistical analysis—Most survival rates between groups were compared by use of the χ2 test. The Fisher exact test was used for analysis when either of the 2 groups being compared contained ≤ 5 horses. A software program3,a was used for statistical analysis. For all analyses, a value of P < 0.05 was considered significant.
Results
Signalment and survival rate of horses—During the study period (10 years and 9 months), 56 geriatric horses underwent exploratory celiotomies for colic. During the same study period, 487 nongeriatric horses underwent exploratory celiotomies for colic. Of the 56 geriatric horses, 22 (39%) were mares, 31 (55%) were geldings, and 3 (5%) were stallions. Of the 487 nongeriatric horses, 215 (44%) were mares, 241 (49%) were geldings, and 31 (6%) were stallions. There was a similar sex distribution between the 2 groups. The geriatric group contained Quarter Horses (16/56 [29%]), Arabians (7/56 [13%]), and Thoroughbreds (4/56 [7%]) as well as many other breeds in smaller numbers. The nongeriatric group contained Quarter Horses (135/487 [28%]), Thoroughbreds (80/487 [16%]), and Paint Horses (66/487 [14%]) as well as a wide variety of other breeds. Age at time of surgery ranged from 20 to 37 years in geriatric horses, with a median age of 23 years and a mean age of 23.4 years (38, 14, and 4 geriatric horses were 20 to 24, 25 to 29, and ≥ 30 years old, respectively). In nongeriatric horses, age ranged from 1 day to 19 years, with a median age of 8 years and a mean age of 8.2 years (119, 196, 108, and 64 nongeriatric horses were < 1 to 4, 5 to 9, 10 to 14, and 15 to 19 years old, respectively).
Twenty-eight of 56 (50%) geriatric horses were discharged from the hospital alive. In nongeriatric horses, 352 of 487 (72%) horses were discharged from the hospital alive. The decreased survival rate in geriatric horses, compared with that in nongeriatric horses, was significant (P < 0.001). Eighty-two percent (28/34) of geriatric horses surviving surgery and anesthetic recovery were discharged from the hospital alive, whereas 89% (352/396) of the nongeriatric horses surviving surgery and anesthetic recovery were discharged from the hospital alive (P = 0.254).
Intraoperative death or euthanasia—Of the 56 geriatric horses, 22 (39%) were euthanized during surgery. Of the 487 nongeriatric horses, 86 (18%) were euthanized during surgery, 3 (0.6%) died during surgery, 6 (1%) died in anesthetic recovery, and 2 (0.4%) were euthanized in anesthetic recovery; in total, 97 horses (20%) did not survive through surgery and anesthetic recovery. The higher percentage of geriatric versus nongeriatric horses that did not survive surgery and anesthetic recovery was significant (P < 0.001). Of the 22 geriatric horses that underwent euthanasia during surgery, 17 (77%) did so because of the presence of a strangulating lesion. Other causes for euthanasia during surgery in geriatric horses included rupture of a portion of the gastrointestinal tract (n = 3) and presence of an inoperable intra-abdominal mass (2). Financial constraints were frequently noted in the records of geriatric horses as a contributing factor to performing euthanasia during surgery. Of the 97 nongeriatric horses that underwent euthanasia during surgery, 55 (57%) did so because of the presence of a strangulating lesion. Other causes for euthanasia or death either during surgery or anesthetic recovery in nongeriatric horses included the presence of a nonstrangulating lesion with a poor prognosis (n = 23), systemic complications while under general anesthesia (10), rupture of a portion of the gastrointestinal tract (8), and a fractured femur (1). The difference in the proportion of geriatric versus nongeriatric horses euthanized because of strangulating lesions was considerable (ie, 77% vs 57%) but not significant (P = 0.075).
Small intestinal lesions—In the geriatric population, 34 of 56 (61%) horses had primary small intestinal lesions. In the nongeriatric population, 142 of 487 (29%) horses had primary small intestinal lesions. The higher percentage of geriatric versus nongeriatric horses that had primary small intestinal lesions was significant (P < 0.001). Of horses with small intestinal lesions, significantly (P = 0.047) fewer geriatric horses (12/34 [35%]), compared with nongeriatric horses (77/142 [54%]), were discharged from the hospital alive. Twenty-six of 34 (76%) geriatric horses with primary small intestinal lesions had strangulating lesions, whereas 73 of 142 (54%) nongeriatric horses with primary small intestinal lesions had strangulating lesions. The higher percentage of geriatric versus nongeriatric horses that had primary small intestinal lesions that were strangulating was significant (P = 0.008). Strangulating lipomas were the predominant lesion in geriatric horses. Seven of the 26 (27%) geriatric horses with strangulating lesions were discharged from the hospital alive, compared with 24 of the 73 (33%) nongeriatric horses with strangulating lesions (P = 0.574). Eight of the 34 (24%) geriatric horses with primary small intestinal lesions had nonstrangulating lesions, whereas 69 of the 142 (49%) nongeriatric horses with primary small intestinal lesions had nonstrangulating lesions. The lower percentage of geriatric versus nongeriatric horses that had primary small intestinal lesions that were nonstrangulating was significant (P = 0.008). Five of 8 geriatric horses with nonstrangulating lesions were discharged from the hospital alive, compared with 53 of 69 (77%) nongeriatric horses with nonstrangulating lesions (P = 0.400).
Cecal lesions—In the geriatric population, 2 of 56 (4%) horses had primary cecal lesions; in the nongeriatric population, 24 of 487 (5%) horses had primary cecal lesions. One of 2 geriatric horses with primary cecal lesions was discharged from the hospital alive, compared with 15 of 24 (63%) nongeriatric horses with primary cecal lesions. No geriatric horses had strangulating cecal lesions, compared with 2 of 24 (8%) nongeriatric horses. Neither of the 2 nongeriatric horses with strangulating cecal lesions was discharged from the hospital alive. Both geriatric horses with primary cecal lesions had nonstrangulating cecal lesions, whereas 22 of 24 (92%) nongeriatric horses with primary cecal lesions had nonstrangulating cecal lesions. One of 2 geriatric horses with nonstrangulating cecal lesions was discharged from the hospital alive, compared with 15 of 22 (68%) nongeriatric horses with nonstrangulating cecal lesions. None of the comparisons between groups for cecal lesions were significant (all values of P = 1.000).
Large colon lesions—In the geriatric population, 13 of 56 (23%) horses had primary large colon lesions; in the nongeriatric population, 283 of 487 (58%) horses had primary large colon lesions. The lower percentage of geriatric versus nongeriatric horses that had primary large colon lesions was significant (P < 0.001). Twelve of 13 geriatric horses with large colon lesions were discharged from the hospital alive, compared with 232 of 283 (82%) nongeriatric horses with large colon lesions (P = 0.339). One of 13 geriatric horses with primary large colon lesions had a strangulating lesion, whereas 40 of 283 (14%) nongeriatric horses with primary large colon lesions had strangulating lesions (P = 1.000). The single geriatric horse with a strangulating large colon lesion was discharged from the hospital alive, compared with 7 of 40 (18%) nongeriatric horses with strangulating large colon lesions (P = 0.195). Twelve of 13 geriatric horses with primary large colon lesions had nonstrangulating lesions, whereas 243 of 283 (86%) nongeriatric horses with primary large colon lesions had nonstrangulating lesions (P = 0.511). Eleven of 12 geriatric horses with nonstrangulating large colon lesions were discharged from the hospital alive, compared with 225 of 243 (93%) nongeriatric horses with nonstrangulating large colon lesions (P = 0.905).
Small colon lesions—In the geriatric population, 5 of 56 (9%) horses had primary small colon lesions; in the nongeriatric population, 38 of 487 (8%) horses had primary small colon lesions. In geriatric horses with primary small colon lesions, 3 of 5 horses were discharged from the hospital alive, compared with 28 of 38 (74%) nongeriatric horses with primary small colon lesions. No geriatric horses had strangulating small colon lesions, whereas 1 of 38 (3%) nongeriatric horses had a strangulating small colon lesion. The single nongeriatric horse with a strangulating small colon lesion did not survive to discharge. All 5 geriatric horses with primary small colon lesions had nonstrangulating lesions; 37 of 38 (97%) nongeriatric horses with primary small colon lesions had nonstrangulating lesions. Three of the 5 geriatric horses with nonstrangulating small colon lesions were discharged from the hospital alive, compared with 28 of 37 (76%) nongeriatric horses with nonstrangulating lesions. None of the comparisons between groups for small colon lesions were significant (all values of P ≥ 0.593).
Other lesions—In the geriatric population, 2 of 56 (4%) horses had intra-abdominal masses associated with their gastrointestinal tracts. In both of these horses, the masses were inoperable and the horses were euthanized during surgery.
Death or euthanasia prior to hospital discharge—In geriatric horses, 7 of 56 (13%) were euthanized prior to discharge after surviving anesthetic recovery. Four of these 7 horses were euthanized because of recurrent colic. One horse each of the 7 was euthanized because of colitis, laminitis, or metabolic decompensation. In nongeriatric horses, 41 of 487 (8%) were euthanized prior to discharge after surviving anesthetic recovery. Twenty-two of these 41 (54%) horses were euthanized because of recurring colic. Of the 41 nongeriatric horses, 5 (12%) were euthanized because of laminitis, 3 (7%) because of endotoxemia, and 3 (7%) because of peritonitis. Two of the 41 (5%) horses died or were euthanized prior to discharge because of rupture of a portion of the gastrointestinal tract. One horse each of the 41 (2%) horses was euthanized or died prior to discharge because of complete incisional dehiscence, colitis, hind end paralysis, signs of a progressive neurologic disorder, renal insufficiency, or respiratory distress. There was no significant (P = 0.308) difference found between the proportion of geriatric versus nongeriatric horses that were euthanized or died after surviving anesthetic recovery from surgery but before hospital discharge.
Follow-up—An attempt to obtain long-term follow-up information for all horses was made in October 2007. Long-term follow-up information was obtained for 20 of the 27 (74%) geriatric horses that were discharged from the hospital alive, with 8 of the 20 having small intestinal lesions and 12 of the 20 having large intestinal lesions. Long-term follow-up information was obtained for 129 of the 349 (37%) nongeriatric horses that were discharged from the hospital alive, with 28 having small intestinal lesions and 101 having large intestinal lesions. Six of the 20 (30%) geriatric horses had survived < 1 year following surgery, whereas 21 of the 129 (16%) nongeriatric horses had survived < 1 year following surgery. Fourteen of the 20 (70%) geriatric horses had survived > 1 year following surgery, whereas 108 of the 129 (84%) nongeriatric horses had survived > 1 year following surgery. The median survival duration for both groups of horses (geriatric and nongeriatric) surviving > 1 year after surgery was 2 years.
Eight of the 20 (40%) geriatric horses for which follow-up information was obtained were still alive at the time of follow-up; 12 (60%) horses had been euthanized or died. Reasons for euthanasia or death included laminitis (n = 6), colic (4), arthritis (1), and a broken limb (1). One hundred five of the 129 (81%) nongeriatric horses for which follow-up information was obtained were still alive at the time of follow-up; 24 (19%) horses had been euthanized or died. Reasons for euthanasia or death included colic (n = 16), laminitis (3), bacterial infection (1), fractured tarsus (1), neurologic problems (1), lightning strike (1), and unknown cause of death (1).
Discussion
In the present study, survival rate at the time of hospital discharge following a single exploratory celiotomy to treat colic was significantly lower in geriatric horses, compared with nongeriatric horses. Although the survival rate for the nongeriatric horses (72%) was comparable to that in another retrospective study,1 the survival rate in the geriatric horses (50%) of our study was much lower. Two factors likely contributing to this lower survival rate were the increased prevalence of strangulating small intestinal lesions in the geriatric horses, compared with the nongeriatric horses, and the increased prevalence of financial constraints associated with surgical treatment of the geriatric horses.
The percentage of horses that died or underwent euthanasia during surgery or in anesthetic recovery was significantly greater in the geriatric versus the nongeriatric population. Most geriatric horses were euthanized during surgery because of the presence of strangulating gastrointestinal lesions. Resolution of these lesions may have necessitated further surgical procedures, increased expense, and a more guarded prognosis, so it stands to reason that these lesions would have provided the most substantial contribution to decreasing the number of geriatric horses surviving surgery and anesthetic recovery.
Financial constraints regarding surgery were subjectively found more frequently in the records of the geriatric horses versus the records of the nongeriatric horses. Financial limitations can certainly confound the interpretation of the present study, as they introduce bias toward owners who are able to spend more money on their horses, often without regard to the gastrointestinal lesion present. It is also possible that horse owners may be more likely to pursue a procedure with more possible complications, such as a resection and anastomosis, in a horse that has more productive years left in its career versus a horse that is retired and is closer to the end of its life.
Several significant differences were found in terms of small intestinal lesions between the geriatric and nongeriatric horses. Significantly more geriatric horses had small intestinal lesions as well as strangulating small intestinal lesions than nongeriatric horses, which contributed to a significantly lower proportion of geriatric horses discharged from the hospital alive. These significant differences in survival rates can be explained by the increased prevalence of strangulating lipomas in the geriatric population, compared with the nongeriatric population. These findings are consistent with those of Freeman and Schaeffer,4 who found that the proportion of horses with strangulating lipomas increased significantly with increasing age.
Significantly more primary large colon lesions were found in nongeriatric horses, compared with geriatric horses. This finding further supports the fact that small intestinal lesions should be high on the differential diagnosis list when examining a geriatric horse with colic. Additionally, it helps to explain why the survival rate for the nongeriatric population in the present study was significantly higher than that of the geriatric population. Short-term survival rates for horses with small intestinal lesions is lower than that of horses with large intestinal lesions.2 Most large colon lesions in the nongeriatric horses were nonstrangulating; these lesions have a significantly better prognosis for survival than strangulating lesions.1
In both the geriatric and nongeriatric horses in the present study, recurring colic was the most prevalent postoperative complication leading to euthanasia or death prior to hospital discharge. This finding is comparable to that of a previous study5 on postoperative complications. It is logical that the primary gastrointestinal lesion along with performance of various procedures and manipulation of the gastrointestinal tract during surgery could commonly result in recurring colic after surgery.
With regard to long-term follow-up, most geriatric and nongeriatric horses for which information was obtained survived > 1 year after surgery. This finding has potentially important implications for owners of horses of any age choosing to pursue an exploratory celiotomy, as it demonstrates that a favorable long-term outcome is often achieved after this procedure is performed.
Little work has been done evaluating survival rates of geriatric horses following exploratory celiotomy. As a result of conducting the present study, our hypothesis was disproved, as the survival rate at the time of hospital discharge in the geriatric population was significantly lower then that of the nongeriatric population. The primary reason for the difference in survival rate between the geriatric and nongeriatric horses appeared to be related to the significantly higher number of geriatric horses euthanized during surgery. It was interesting to find, however, that the difference in survival rate at the time of hospital discharge between geriatric and nongeriatric horses that survived surgery and anesthetic recovery was not significant. The information obtained from this study may serve as an important reference for veterinarians to share with the owners of geriatric horses as they are trying to make difficult decisions about whether to pursue surgery as treatment for persistent or severe colic.
JMP, SAS Institute Inc, Cary, NC.
References
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Mair TS, Smith LJ. Survival and complication rates in 300 horses undergoing surgical treatment of colic. Part 2: short-term complications. Equine Vet J 2005;37:303–309.
