Predicting outcomes in equine peritonitis: Multivariable analysis of admission and post-admission data from a UK hospital population.

Overview

• This study analyzed outcomes of horses with peritonitis admitted to a UK hospital to identify factors that predict survival.
• The research found that heart rate and certain clinical signs were key predictors of short-term survival, with better outcomes for primary peritonitis compared to secondary peritonitis.

Background and Objective

• Peritonitis is a severe and potentially fatal inflammation of the abdominal lining in horses.
• There has been limited data on survival outcomes and predictors of survival in equine peritonitis cases.
• The study aimed to report both short- and long-term survival and to identify clinical factors associated with outcomes in affected horses.

Methods

• Retrospective observational study using data from horses diagnosed with peritonitis at a UK referral hospital from 2010 to 2024.
• Diagnosis required a peritoneal fluid nucleated cell count over 10 × 10⁹/L.
• Short- and long-term morbidity and mortality were collected and analyzed.
• Multivariable logistic regression identified predictors of short-term survival using two models:
  • Model 1 used data available at admission.
  • Model 2 used data available at the time of a second abdominal fluid sample (abdominocentesis).

Results

• 123 horses diagnosed with peritonitis were included in the analysis.
• Overall short-term survival rate was 74% (91 out of 123 horses survived to hospital discharge).
• Survival was substantially better in primary peritonitis cases (90%) compared to secondary peritonitis (50%).
• 31 horses underwent surgery, with only 48% short-term survival post-operation.
• Model 1 predictors of decreased survival at admission:
  • Higher heart rates (Odds Ratio (OR) 0.90): each increased beat per minute decreases survival odds.
  • Sanguineous (bloody) peritoneal fluid (OR 0.16) indicated worse prognosis.
• Model 1 predictors of better survival:
  • Ponies had significantly better survival odds than horses (OR 8.30).
  • Normal rectal examination findings correlated with improved survival (OR 8.25).
• Model 2 results (at second abdominocentesis) reaffirmed increased heart rate as the strongest predictor of poor survival (OR 0.89).
• Long-term survival rates post-discharge were high:
  • 98% survival at 30 days.
  • 93% survival at 90 days.
  • 88% survival at 1 year (365 days).
• About one-third of horses developed complications after hospital discharge, mainly colic and fever, typically within 90 days of admission.
• Peritonitis recurrence was rare, occurring in 6 horses.

Conclusions and Clinical Implications

• The prognosis for primary peritonitis is substantially better than for secondary peritonitis.
• Heart rate is a reliable and easily measured clinical indicator for predicting short-term survival at both admission and after initial treatment.
• Clinical findings such as rectal exam results and the nature of abdominal fluid also contribute important prognostic information.
• Despite a life-threatening illness, most horses that survive to hospital discharge have favorable long-term outcomes.
• Monitoring for complications is important within the first 3 months post-discharge to manage and mitigate risks effectively.
• The findings can help veterinarians triage cases, inform owners, and guide treatment decisions in equine peritonitis management.
• Limitations include the retrospective design and data from a single referral center, which may impact generalizability.