Morphological changes in the small intestinal smooth muscle layers of horses suffering from small intestinal strangulation. Is there a basis for predisposition for reduced contractility?

Factors associated with development of post-operative reflux in horses with large colon volvulus and association with complications and outcomes

BACKGROUND

Post-operative reflux (POR) is rare following large colon volvulus (LCV) but does occur despite the absence of a small intestinal lesion. The prevalence, risk factors and association with survival of POR after LCV are currently unknown.

OBJECTIVES

To determine the prevalence of POR in horses with an LCV and its association with survival. A further objective was to assess factors which may predict POR. The hypothesis was that horses with POR following LCV surgery have a worse outcome for survival compared to those without POR.

STUDY DESIGN

A retrospective cross-sectional study.

METHODS

Clinical data of client owned horses which underwent colic surgery at a single UK referral hospital between 2008 and 2021, where LCV was the primary finding, were retrieved from hospital records. Statistical analyses included chi-squared, t-tests and odds ratios (ORs). Horses with concurrent lesions, and those that did not survive past anaesthetic recovery, were excluded from analysis. POR was defined as ≥2 L of gastric reflux on at least one occasion.

RESULTS

A total of 128 horses were included in the study, 23 of which had POR (18%). Overall survival to hospital discharge was 86%, 95% in the non-POR and 44% in the POR group. Horses with POR were less likely to survive to discharge than those without (OR = 26, 95% confidence interval [CI] [7.68-88.0], p < 0.001), and less likely to be alive 3 years after surgery (OR = 13.4, 95% CI [2.78-64.8], p < 0.001).

MAIN LIMITATIONS

Due to the retrospective study design, full data sets were not available for every case because clinical records were incomplete or, at that time, certain tests were not performed or clinical variables were not measured.

CONCLUSIONS

POR in LCV cases is a negative prognostic indicator for survival.

Histological Evaluation of Resected Tissue as a Predictor of Survival in Horses with Strangulating Small Intestinal Disease

Strangulating small intestinal disease (SSID) in horses carries a poor prognosis for survival, especially following resection of ischaemic tissue. The margins of a resection are principally based on visual appraisal of the intestine during surgery. We hypothesized that histological evaluation of resected tissue may identify occult changes indicative of prognosis. Small intestinal samples from 18 horses undergoing resection for SSID and 9 horses euthanised for reasons unrelated to gastrointestinal pathology were utilised. Histological appearance was used to generate a 'total damage score' (TDS) for the control tissue, grossly normal tissue at oral and aboral extremities (sections OR1 and AB1) of the resected intestine, and oral and aboral extremities of visually abnormal tissue (sections OR2 and AB2) from SSID horses. The relationship between TDS and long-term post-operative survival was investigated. TDS was not different between control tissues and OR1 and AB1 sections. Five surgical cases were alive at follow-up, the longest follow-up time being 2561 days. Based on the median scores for SSID cases versus controls, cut-off values were generated to evaluate post-operative survival versus TDS. Only OR2 TDS was significantly associated with survival, with a higher (worse) score indicating longer survival. More severe tissue insult may expedite rapid progression to surgery, improving post-operative outcomes.

Early Identification of Intestinal Strangulation: Why It Is Important and How to Make an Early Diagnosis

Horses with colic caused by intestinal strangulation can have an excellent outcome with early surgical correction of the obstruction. The expense associated with surgery is typically less with early lesion correction. The challenge is making an early diagnosis of intestinal strangulation. Although for some horses with a strangulating obstruction, the need for surgery is made based on severe colic signs or lack of response to analgesia, in other horses, it is less obvious. Signalment, history, and meticulous physical examination, combined with some targeted diagnostic procedures can help with early diagnosis of intestinal strangulation. Improving the outcome of these horses requires diligence and a team-based approach from the owner or caregiver, primary care veterinarian, and specialists.

Adaptive mechanisms in no flow vs. low flow ischemia in equine jejunum epithelium: Different paths to the same destination

Intestinal ischemia reperfusion injury (IRI) is a frequent complication of equine colic. Several mechanisms may be involved in adaptation of the intestinal epithelium to IRI and might infer therapeutic potential, including hypoxia-inducible factor (HIF) 1α, AMP-activated protein kinase (AMPK), nuclear factor-erythroid 2-related factor 2 (NRF2), and induction of autophagy. However, the mechanisms supporting adaptation and thus cellular survival are not completely understood yet. We investigated the activation of specific adaptation mechanisms in both no and low flow ischemia and reperfusion simulated in equine jejunum epithelium in vivo. We found an activation of HIF1α in no and low flow ischemia as indicated by increased levels of HIF1α target genes and phosphorylation of AMPKα tended to increase during ischemia. Furthermore, the protein expression of the autophagy marker LC3B in combination with decreased expression of nuclear-encoded mitochondrial genes indicates an increased rate of mitophagy in equine intestinal IRI, possibly preventing damage by mitochondria-derived reactive oxygen species (ROS). Interestingly, ROS levels were increased only shortly after the onset of low flow ischemia, which may be explained by an increased antioxidative defense, although NFR2 was not activated in this setup. In conclusion, we could demonstrate that a variety of adaptation mechanisms manipulating different aspects of cellular homeostasis are activated in IRI irrespective of the ischemia model, and that mitophagy might be an important factor for epithelial survival following small intestinal ischemia in horses that should be investigated further.

Short-term exposure to urban PM2.5 particles induces histopathological and inflammatory changes in the rat small intestine

Air pollution and exposure to fine airborne particles with aerodynamic diameter <2.5 μm (PM_2.5 ) negatively impacts human health. Airways constitute a primary route of exposure but PM_2.5 -contaminated food, drinks as well as mucociliary and hepatobiliary clearance all constitute potential entry points into the intestine. This study evaluated intestinal histopathological and inflammatory changes as well as enteric neuronal numbers after short- or long-term exposure to urban PM_2.5 . Using a nebulizer, male rats were exposed to a mist with a concentration of 5.3mg PM_2.5 /m³ for 8 h (short term) or 1.8 mg PM_2.5 /m³ for 3 h/day, 5 days/week for 8 weeks (long-term) with controls run in parallel. Samples were taken from three regions of the small intestine as well as the colon. Results showed that short-term exposure to PM_2.5 induces mucosal lesions and reduces IL1β levels in the small intestine but not colon. No significant changes were observed after long-term exposure, suggesting the presence of intestinal adaptation to environmental stressors in the PM_2.5 . To our knowledge, this is the first study to systematically characterize regional effects along the intestine.

Idiopathic Fibrosis of the Tunica Muscularis of the Large Intestine in Five Horses with Colic

Histological evidence of fibrosis affecting the outer layer of the large intestinal tunica muscularis was identified in five of 32 horses affected by colic. In three cases, foci of pale eosinophilia and vacuolation of myocytes were observed. These findings are suggestive of a degenerative and fibrotic abnormality in the outer layer of the tunica muscularis of the large intestinal smooth muscle of some horses with colic.

Prevention of post operative complications following surgical treatment of equine colic: Current evidence

Changes in management of the surgical colic patient over the last 30 years have resulted in considerable improvement in post operative survival rates. However, post operative complications remain common and these impact negatively on horse welfare, probability of survival, return to previous use and the costs of treatment. Multiple studies have investigated risk factors for post operative complications following surgical management of colic and interventions that might be effective in reducing the likelihood of these occurring. The findings from these studies are frequently contradictory and the evidence for many interventions is lacking or inconclusive. This review discusses the current available evidence and identifies areas where further studies are necessary and factors that should be taken into consideration in study design.

Long-term survival in horses with strangulating obstruction of the small intestine managed without resection

REASONS FOR PERFORMING STUDY

Although many studies have described results after small intestinal resection and anastomosis in horses, few have described the outcome in horses with strangulating lesions managed without resection.

OBJECTIVES

To examine short- and long-term recoveries in horses with strangulated small intestine that was judged to be viable during surgery and not resected.

STUDY DESIGN

Retrospective analysis of case records.

METHODS

Data were reviewed from all cases (35 horses) with colic caused by small intestinal strangulation that underwent surgery between 1996 and 2011 at 2 university hospitals and that were managed without resection by 2 surgeons who used a clinical grading system to assess intestinal viability. Kaplan-Meier analyses were used to examine long-term survival.

RESULTS

Survival to discharge from the hospital was 100%, and post operative complications developed in 11 horses (31%). Three horses (8.6%) required repeat coeliotomy because of persistent pain with or without reflux, and they responded favourably to decompression of distended intestine. Ten horses died after discharge, and 12 were still alive at follow-up from 20 to 192 months after surgery. Information was available on 13 horses after discharge, but these were eventually lost to follow-up. Kaplan-Meier analyses yielded a median survival probability of 120 months.

CONCLUSIONS

A subjective method of assessing small intestinal viability in strangulated small intestine in horses, as used in this study, could reduce the need for resection and anastomosis, with the associated complications and costs. Also, the favourable post operative course in these horses provides strong evidence that early referral could avoid the need for resection and improve survival. The numbers of horses with the most severe changes that were not resected were too small to allow a conclusion that such segments should be left in place, and additional criteria might be needed to guide that decision in such cases.