There is little reported information on the clinicopathology features of a horse with left dorsal large colon volvulus. We attempted to derive this information, based on a retrospective analysis of 1 horse admitted to Veterinary Teaching Hospital (VTH) of the Tehran Regional College of Veterinary Medicine, Karaj Campus, Iran.
The outcome and prognosis for horses after surgery for colic can be difficult to predict and is highly dependent on the nature and severity of the lesion
. To our knowledge, few studies report outcome in horses with left dorsal large colon volvulus (defined as volvulus unrelated to other apparent causes like incarceration, lipoma, mesenteric rent, etc.
). Thus, our purpose was to investigate historical data, signalment, clinical signs, physical examination findings, results of laboratory analysis, surgical, necropsy and histopathological examinations of horse with a diagnosis of left dorsal large colon volvulus at surgery or necropsy, in relation to outcome (survival or non-survival). Our goal was to determine clinical and clinicopathologic factors associated with hospital mortality for large colon volvulus.
The prognosis for horses with large colon volvulus has been reported to be 30% to 60%
. A recent study reported a survival rate of 83%; however, this study was performed in a region of the UK with early referral and surgery
. A recent study reported that horses with large colon volvulus and plasma lactate less than 6.0 mmol/L can be predicted to survive based on a sensitivity and specificity of 84% and 83%
. Complete volvulus of the large colon is a serious condition causing severe unrelenting abdominal pain. It is most common in post partum broodmares and is not commonly reported in yearlings
. The condition has been associated with a poor prognosis although survival rates have improved with advances in gastrointestinal surgery and prompt surgical intervention
. Volvulus may occur predominately in dorsomedial rotations
. Volvulus may also occur anywhere along the length of the colon although it is reported most commonly at the level of the caeco-colic fold. The clinical effects of the volvulus and prognosis depend on the degree of rotation and resulting ischaemia. Partial rotation (<270°) may cause milder or even no clinical signs
. Colic is one of the most difficult diseases to study with epidemiologic methods due to the large number of diseases, cause colic (abdominal pain) as a clinical sign. Historically, there has been concern that analgesics administered before referral might mask signs of surgical colic on admission to referral hospitals
. We were unable to find evidence to support this. The increased frequency of severe pain on admission associated with previous butorphanol administration may reflect the fact that the most painful horses were administered butorphanol, and by admission, this failed in effectively control of their pain. Two factors should be considered when trying to prevent colic; farm factors and horse factors
. Farm factors include management, use, feeding, and environment. The associated risks on farms with high rates of colic include poor parasite control, high concentrated levels in the diet, multiple sources of concentrates (including supplements which contain higher than suspected amounts of soluble carbohydrates), chronic deficiency in water, excessive use of NSAIDS, acute changes in hay or grain, and horses in training that are confined and fed large amounts of soluble carbohydrates and lesser amounts of roughage. Altering these risks with management has decreased the incidence of colic on farms with a annual colic rate higher than average. On farms with a high incidence of colic (>10 colic cases per 100 horses per year) careful monitoring of the daily management and measurement of the energy, protein and fiber in the diet should be the first steps in assessing the farm for colic risk. Colic has been identified by veterinarians and a national survey as a leading health concern and a major cause of death in horses
. Strangulating large-colon volvulus can account for 11% to 27% of surgical cases of colic
, and fatality of affected horses can approach 34% to 65.3% without resection
. Even resection does not remove all nonviable colon, and integrity of the remaining mucosa can determine the outcome
. Probability of survival can be influenced by loss of the epithelial barrier, which allows transmucosal leakage of endotoxin, bacterial chemotactic peptides, and bacteria
. Rapid repair of the epithelium is important for recovery and involves 2 processes that are usually completed within hours: mucosal restitution and tightening of paracellular pathways between remaining cells
. Restitution involves sealing the mucosal defect with remaining viable cells before final repair through cell division and proliferation
. Anatomically, the ascending colon is of relatively large size and has minimal dorsal attachments, thereby predisposing it to strangulating and non-strangulating displacements. Horses with strangulating large colon volvulus have been reported to have a relatively low rate of survival
. However, another study reported a survival rate of 83%, which is likely due to early recognition and surgical correction of the strangulating volvulus
. This earlier identification and resolution of the problem was probably facilitated by more frequent monitoring and closer observation of the expensive horses on the farms located in this geographic region and the proximity of the farms to the referral hospital. Despite these encouraging results, morbidity and mortality of horses with strangulating large colon volvulus generally remains high. Hypoxemia and ischemia caused by strangulating volvulus causes transmural colonic damage, especially causing disruption of the mucosal barrier. This mucosal damage occurs subsequent to ischemia and secondary to reperfusion injury. Reperfusion injury is initiated by the production of oxygen free radicals and perpetuated by neutrophils and phospholipid-derived inflammatory mediators
. Our study had several limitations. Incomplete data was a particular problem, and some assumptions were made. Where a specific historical factor, physical finding, or treatment was not recorded. In this horse, the variable may have been measured, but not recorded. Similarly, there was more detail in surgical reports compared with other studies. The case reported here was assumed to be the most common form of volvulus where the mesentery twists the intestine into distinct spirals. Another weakness of retrospective studies is that the circumstances surrounding clinical decisions are not always evident from the record. Therefore economic decisions regarding euthanasia, treatments administered, and the length of postoperative hospitalization are not always apparent and can influence the data. The horse in our study that did not survive was euthanatized. Although there was good clinical evidence in some cases other studies that survival was unlikely (e.g.
, ruptured intestine), the historical data recorded may be less accurate than the data directly recorded at the clinic as it relies on information reported by third parties, and additionally, in the case of duration of pain, owner observation of the horse. The major weakness of our study was the lack of longterm outcome data. We believe that this data demonstrates that information on hospital outcome is still very relevant to clinicians and owners, making decisions at the time surgery is recommended. These findings can be used to make a scientific assessment of prognosis in the pre-operative, operative, and post-operative management of horses with colon volvulus.