Peritonitis: What the Research Says
Evidence from 21 peer-reviewed studies
What Professionals Should Know
- •NGAL measurement in peritoneal fluid may help differentiate non-strangulating intestinal infarction from other types of peritonitis, potentially enabling faster surgical decision-making in cases that are clinically difficult to distinguish
- •NGAL is useful as an inflammatory marker in abdominal disease but does not reliably discriminate between obstructive colic types; clinical findings and other diagnostics remain essential
- •Peritoneal fluid NGAL shows greater discriminatory value than serum NGAL for identifying NSII, suggesting abdominocentesis analysis should be prioritized when this condition is suspected
- •Peritoneal fluid analysis is a useful diagnostic tool in post-partum mares presenting with emergency colic-like signs; interpret results in the context of clinical presentation as no single finding is pathognomonic
- •Higher peritoneal PCV with lower cell counts and non-degenerate neutrophils suggests haemorrhage rather than septic peritonitis, guiding urgency and type of intervention
- •Plan for aggressive fluid resuscitation and close monitoring in post-partum emergencies, as overall survival is approximately 55% even at referral centres
- •Implement fecal egg count testing and specific S. vulgaris diagnostics (PCR and serology) as standard practice rather than routine deworming; high seropositivity suggests widespread exposure that needs targeted management
- •Consider S. vulgaris as a differential diagnosis in horses with peritonitis, particularly given rising concerns about this parasite in Sweden since prescription-only anthelmintics were implemented
- •Educate clients on pasture management strategies to reduce parasitic burden, as this appears to be a significant knowledge gap; rotation systems and fecal monitoring should be prioritized over blanket deworming protocols
- •For horses requiring peritonitis treatment, intraperitoneal ceftriaxone administration delivers higher drug concentrations directly to the infection site for longer duration than IV administration, potentially improving clinical outcomes
- •The IP route is safe with no adverse effects observed, making it a viable alternative to IV administration when treating peritoneal infections
- •Consider intraperitoneal ceftriaxone dosing at 25 mg/kg diluted in 1L saline solution once daily for equine peritonitis prophylaxis and treatment protocols
- •SAA and fibrinogen testing can help rule out non-inflammatory colics (e.g., obstruction) in suspected EGS cases, but cannot definitively diagnose EGS or differentiate it from other inflammatory abdominal conditions
- •Elevated acute phase proteins in a colic case should prompt investigation for inflammatory causes including EGS, peritonitis, and enteritis rather than assuming simple obstruction
- •Activin A elevation in clinically normal co-grazing horses warrants monitoring, as it may indicate subclinical EGS exposure and risk of disease development
- •Peritoneal TGF-beta(1) levels may serve as a biomarker for severe gastrointestinal disease (ischaemia, peritonitis) and prognosis in colicky horses, helping clinicians identify high-risk cases
- •Elevated peritoneal TGF-beta reflects an anti-inflammatory response to severe disease; horses with markedly elevated levels warrant aggressive intervention and careful monitoring for poor outcomes
- •Peritoneal fluid analysis type (exudate vs transudate) correlates with TGF-beta elevation and disease severity, supporting the use of fluid classification in risk stratification
- •Peritoneal D-dimer testing can help clinicians assess fibrinolytic activity and severity of peritoneal involvement in colic cases, potentially aiding prognosis
- •Elevated peritoneal D-dimer combined with altered peritoneal fluid analysis suggests more severe GI disease (peritonitis, enteritis, ischemia) requiring aggressive intervention
- •D-dimer measurement may help identify high-risk cases with poor outcomes, allowing for early discussion of treatment options and prognosis with owners
- •Most horses with peritonitis can be successfully treated and discharged (86%), making aggressive medical management a reasonable approach in referral cases
- •Long-term prognosis is generally good with 84% surviving beyond 12 months, but monitor discharged horses closely as one-third develop post-peritonitis complications including recurrent colic
- •Identify the underlying cause of peritonitis when possible, as secondary causes (urinary/mass-related) carry poorer prognosis than idiopathic peritonitis
- •Severe gastrointestinal conditions with poor prognosis (ischemia, enteritis, peritonitis) commonly trigger DIC with fibrin deposition in vital organs; recognize these as indicators of systemic involvement beyond the gut.
- •Simple obstructive colic cases do not show similar fibrin deposition patterns, supporting the prognostic distinction between mechanical obstruction and ischemic/inflammatory disease.
- •Postmortem fibrin detection may help explain multiorgan failure and sudden deterioration in severe colic cases, informing differential diagnosis and prognostic counseling.
- •When counselling owners before colic surgery, advise that approximately 1 in 10 horses may require urgent re-surgery, with poor long-term prognosis (22% survival)
- •Relaparotomy should be considered for persistent post-operative pain, ileus, peritonitis, or wound breakdown, but owners must understand high complication and recurrence rates
- •Horses surviving relaparotomy require intensive post-operative monitoring and management, as nearly 40% will need further surgical intervention for recurrent colic
- •Include actinobacillosis in differential diagnoses for chronic weight loss in adult horses, even without fever or acute clinical signs
- •Use ultrasonography to identify and sample peritoneal and pleural effusions when investigating unexplained weight loss; fluid analysis is essential for diagnosis
- •Prompt drainage of infected fluid combined with appropriate antimicrobial therapy can result in complete recovery even in advanced cases
- •Peritoneal fluid analysis is essential for diagnosing peritonitis and predicting prognosis—perform abdominocentesis promptly in colic cases with concerning clinical signs
- •Most horses with peritonitis have a reasonably good prognosis (83% short-term survival, 88% long-term survival), which should inform owner counselling during acute cases
- •Consider infectious causes as most likely, but recognize that 39% of cases remain idiopathic even after investigation—supportive medical management remains critical
- •In regions with endemic S. vulgaris, suspect nonstrangulating intestinal infarction in horses presenting with mild colic lasting >24 hours and concurrent peritonitis—early recognition is critical as medical treatment alone does not succeed
- •Surgical intervention with intestinal resection offers the only realistic chance of survival (33%), so consider laparotomy in suitable candidates rather than medical management alone
- •Test for S. vulgaris-specific antibodies and monitor peritoneal fluid WBC and SAA concentrations to support diagnosis and guide treatment decisions
- •Medical treatment can be considered as a reasonable alternative to surgery for postpartum uterine tears, achieving similar survival rates—however, the severity threshold for successful medical vs. surgical management remains unclear
- •Monitor for prognostic indicators of poor outcome: gastric reflux, elevated heart rate, metabolic derangements (high anion gap, low CO2), and low leukocyte counts may identify mares requiring more aggressive intervention
- •Be aware that right uterine horn tears occur significantly more frequently postpartum; this location-specific risk may guide clinical assessment and surveillance
- •Grade IV rectal tears in post-parturient mares can be surgically repaired in standing animals using a two-layer closure technique (stapled and oversewn), with reasonable expectations of survival and return to breeding
- •The standing approach with perineal access and temporary sphincterotomy avoids general anesthesia risks and allows better visualization of the tear margins
- •Close post-operative monitoring is essential as peritonitis can develop even with an intact repair; consider prophylactic standing abdominal lavage and broad-spectrum antibiotics
- •Add C. sordellii to your differential diagnosis when investigating perinatal foal deaths with omphalitis or internal umbilical remnant infection, rather than assuming only E. coli or Streptococcus
- •Request specific bacterial culture and identification of umbilical remnant tissues in necropsy investigations to ensure appropriate organism detection
- •Implement strict foaling hygiene and umbilical cord management protocols to minimize risk of pathogenic bacterial colonization of umbilical structures
- •Closed-suction abdominal drains are a practical and effective tool for managing peritonitis and preventing adhesions post-colic surgery, but expect minor complications in roughly half your cases.
- •Plan for frequent lavage protocols (every 4-12 hours) and monitor closely for drain obstruction, fluid leakage, and subcutaneous fluid pockets—these are common and manageable issues.
- •Be aware that incisional infection occurs in about 1 in 3 horses and hernia in 1 in 10, so proper post-operative care and client communication about these risks are essential.
- •Use abdominal ultrasound as a primary diagnostic tool when evaluating equine colic—it reliably identifies which cases need surgery versus medical management
- •Watch for moderate-to-severe pain signs, recurring pain after initial treatment, and loss of gut sounds as red flags indicating surgical colic requiring emergency referral
- •Recognize that late diagnosis significantly reduces recovery outcomes; implement diagnostic imaging early in colic evaluation to improve prognosis
- •Review your perioperative antimicrobial protocol for exploratory celiotomy against current evidence-based guidelines, as this survey reveals significant variation among specialists that may not reflect best practices
- •Consider whether intraoperative re-dosing of gentamicin is appropriate for your cases, particularly for prolonged procedures, as most respondents did not re-dose despite pharmacokinetic support for doing so
- •Evaluate your postoperative treatment duration decisions against documented complications (fever, resection, incisional issues) rather than relying solely on diagnosis, as these factors significantly influenced practitioners' choices
- •Hydrops carries a good prognosis for both survival and future fertility when diagnosed early and managed with transcervical gradual fluid drainage, with no observed recurrence in this series
- •Hydrallantois responds better to treatment than hydramnios; prioritize transcervical drainage to avoid serious complications like hypovolemic shock and hemorrhage that compromise both survival and breeding potential
- •Expect approximately 71% of mares to foal the following year after hydrops treatment, allowing informed breeding and management decisions for affected broodmares
- •Dual cannulation procedures carry significant postoperative risk; practitioners should implement robust complication management protocols including close monitoring for herniation, peritonitis, and dehydration
- •The 63% survival rate indicates this is a high-risk surgical procedure; careful patient selection and owner consent regarding complications are essential before undertaking dual cannulation
- •Postoperative management recommendations from this study should guide perioperative protocols to improve outcomes in future dual cannulation cases
Key Research Findings
Healthy horses had low NGAL concentrations in serum (21.0 μg/L) and peritoneal fluid (9.5 μg/L)
Horses with NSII had markedly elevated peritoneal fluid NGAL (2163.0 μg/L) compared to all other groups (p < 0.001)
Horses with inflammatory abdominal disease also showed increased serum (171.1 μg/L) and peritoneal fluid (314.1 μg/L) NGAL, but lower than NSII
Simple and strangulating intestinal obstructions did not show significantly elevated NGAL compared to healthy controls
Of 110 post-partum mares, 50% presented with urogenital trauma, 30% with GIT disease, and 20% with post-partum haemorrhage
Peritoneal fluid PCV, WBCC, and cytology (presence/absence of degenerate neutrophils) differed significantly between diagnostic categories
Higher peritoneal fluid PCV, absence of degenerate neutrophils, and lower WBCC were associated with increased likelihood of PPH diagnosis
Overall survival to discharge was 55%, with peritoneal fluid analysis aiding diagnosis but no single factor being uniformly diagnostic
S. vulgaris PCR prevalence was 5.5%, but 62% of horses tested positive on ELISA serology, indicating high exposure despite low active infection rates
Horses presenting with peritonitis showed significantly higher S. vulgaris antibody levels compared to other diagnoses and control horses
Only 36% of horse owners used fecal egg counts alone for parasite management, while 29% dewormed routinely without prior diagnostics
Effective pasture management methods to reduce parasitic burden were rare among surveyed horse owners
Intraperitoneal ceftriaxone administration achieved therapeutic concentrations (>1 μg/mL MIC) in peritoneal fluid for 24 hours versus only 12 hours with intravenous administration
Intraperitoneal administration provided greater cephalosporin availability in peritoneal fluid with higher peak concentrations and longer duration above MIC compared to intravenous route
No adverse effects were observed with either administration route over the 5-day treatment period
Evidence Base
Concentrations of neutrophil gelatinase-associated lipocalin are increased in serum and peritoneal fluid from horses with inflammatory abdominal disease and non-strangulating intestinal infarctions.
Winther Malou F, Haugaard Simon L, Pihl Tina H et al. (2023) — Equine veterinary journal
Peritoneal fluid analysis in equine post-partum emergencies admitted to a referral hospital: A retrospective study of 110 cases.
Offer Katie S, Russell Catherine M, Carrick Joan B et al. (2022) — Equine veterinary journal
Parasite Occurrence and Parasite Management in Swedish Horses Presenting with Gastrointestinal Disease-A Case-Control Study.
Hedberg-Alm Ylva, Penell Johanna, Riihimäki Miia et al. (2020) — Animals : an open access journal from MDPI
Plasma and peritoneal fluid concentrations of ceftriaxone after intravenous and intraperitoneal administration in horses.
Alonso J M, Peccinini R G, Campos M L et al. (2018) — Veterinary journal (London, England : 1997)
In equine grass sickness, serum amyloid A and fibrinogen are elevated, and can aid differential diagnosis from non-inflammatory causes of colic.
Copas V E N, Durham A E, Stratford C H et al. (2013) — The Veterinary record
Peritoneal concentrations of transforming growth factor beta in horses with colic.
Argüelles D, Casteljins G, Carmona J U et al. (2010) — Equine veterinary journal
Peritoneal D-dimer concentration for assessing peritoneal fibrinolytic activity in horses with colic.
Delgado M A, Monreal L, Armengou L et al. (2009) — Journal of veterinary internal medicine
Study of the short- and long-term outcomes of 65 horses with peritonitis.
Henderson I S F, Mair T S, Keen J A et al. (2008) — The Veterinary record
Detection of fibrin deposits in tissues from horses with severe gastrointestinal disorders.
Cotovio Mário, Monreal Luis, Navarro Marga et al. (2007) — Journal of veterinary internal medicine
Survival and complication rates in 300 horses undergoing surgical treatment of colic. Part 4: Early (acute) relaparotomy.
Mair T S, Smith L J (2005) — Equine veterinary journal
Multicavitary septic effusions associated with actinobacillosis in an adult Tennessee Walking Horse with weight loss
Means K., Townsend K., Johnson P. (2022) — Equine Veterinary Education
Clinical and diagnostic findings, treatment, and short- and long-term survival in horses with peritonitis: 72 cases (2007-2017).
Arndt Stefanie, Kilcoyne Isabelle, Vaughan Betsy et al. (2021) — Veterinary surgery : VS
Nonstrangulating intestinal infarctions associated with Strongylus vulgaris: Clinical presentation and treatment outcomes of 30 horses (2008-2016).
Pihl T H, Nielsen M K, Olsen S N et al. (2018) — Equine veterinary journal
Comparison of surgical and medical treatment of 49 postpartum mares with presumptive or confirmed uterine tears.
Javsicas Laura H, Giguère Steeve, Freeman David E et al. (2010) — Veterinary surgery : VS
Surgical technique to repair grade IV rectal tears in post-parturient mares.
Kay Alastair T, Spirito Michael A, Rodgerson Dwayne H et al. (2008) — Veterinary surgery : VS
Infection of internal umbilical remnant in foals by Clostridium sordellii.
Ortega J, Daft B, Assis R A et al. (2007) — Veterinary pathology
Use of an active intra-abdominal drain in 67 horses.
Nieto Jorge E, Snyder Jack R, Vatistas Nicholas J et al. (2003) — Veterinary surgery : VS
Equine colic: A comprehensive overview of the sonographic evaluation, diagnostic criteria, and management of different categories
M. Tharwat, F. Al-Sobayil (2025) — Open Veterinary Journal
Current Antimicrobial Use in Horses Undergoing Exploratory Celiotomy: A Survey of Board-Certified Equine Specialists.
Rockow Meagan, Griffenhagen Gregg, Landolt Gabriele et al. (2023) — Animals : an open access journal from MDPI
Factors Affecting Survival and Future Foaling Rates in Thoroughbred Mares with Hydrops.
Lemonnier Louise C, Wolfsdorf Karen E, Kreutzfeldt Nicole et al. (2022) — Journal of equine veterinary science