Serial postoperative peritoneal fluid analyses in horses with naturally-occurring strangulating and non-strangulating gastrointestinal lesions.

Overview

• This study examined changes in peritoneal fluid characteristics after surgery in horses with different types of naturally occurring gastrointestinal lesions to improve understanding of postoperative monitoring.

Background and Objective

• Gastrointestinal lesions in horses can be classified as strangulating (where blood supply is compromised) or non-strangulating.
• Exploratory laparotomy is a common surgical procedure used to diagnose and treat these lesions.
• Postoperative monitoring often includes analyzing peritoneal fluid (fluid in the abdominal cavity) for markers such as lactate, total protein (TP), and total nucleated cell count (TNCC), which can indicate tissue health and inflammation.
• The objective was to describe the postoperative peritoneal fluid characteristics and observe differences between horses with strangulating versus non-strangulating lesions over time.

Study Design and Methods

• The research was a prospective, observational cohort study involving 26 client-owned horses undergoing exploratory laparotomy for naturally-occurring gastrointestinal issues.
• Horses were divided into two groups based on their lesion diagnosis:
  • 14 with strangulating lesions
  • 12 with non-strangulating lesions
• Peritoneal fluid samples were collected at four time points:
  • Pre- or intra-operatively (before/during surgery)
  • Postoperatively at 24 hours, 72 hours, and 168 hours (1 week)
• Assessed parameters included:
  • Peritoneal lactate levels
  • Total protein (TP)
  • Total nucleated cell count (TNCC)
  • Cytology (cell morphology examination)
  • Systemic (blood) lactate levels to compare with peritoneal lactate.
• Statistical analysis used linear mixed models to account for repeated measures over time and comparisons between lesion types.

Key Findings

• Preoperative differences:
  • Horses with strangulating lesions had significantly higher peritoneal lactate and total protein levels than those with non-strangulating lesions (p < .001 for lactate, p = .02 for TP).
  • This reflects the more severe tissue damage and compromised blood supply in strangulating lesions.
• Postoperative results:
  • After surgery, no significant differences were observed between the two lesion groups for any fluid parameter at any postoperative time point.
  • Both groups showed elevated peritoneal lactate and total protein levels that remained above normal for the entire postoperative week, indicating ongoing tissue repair or inflammation.
  • Systemic lactate levels normalized by 24 hours postoperatively in both groups, significantly decreasing from preoperative values (p = .02), suggesting systemic recovery.
  • Peritoneal TNCC increased at 24 hours postoperatively in both groups compared to preoperative levels (p = .001 for strangulating; p < .001 for non-strangulating), indicating an inflammatory response in the peritoneal cavity after surgery.

Conclusions and Clinical Implications

• Peritoneal fluid lactate and total protein remain elevated for at least one week post-surgery, regardless of lesion type.
• Systemic lactate normalizes relatively quickly within 24 hours, making it less useful for extended postoperative monitoring.
• Elevated TNCC at 24 hours points to a typical postoperative inflammatory response but is not different between lesion types.
• Clinically, standard reference values for peritoneal fluid obtained preoperatively should not be used to interpret postoperative fluid analyses since values remain persistently elevated after surgery.
• This information helps veterinarians better understand normal postoperative changes and avoid misinterpreting elevated fluid parameters as complications or persistent disease post-surgery.