Equis ISSN 2398-2977

Abdomen: hernia - incisional

Synonym(s): Eventration, Abdominal hernia, Wound breakdown, Dehiscence

Contributor(s): Vetstream Ltd, Graham Munroe, Jarred Williams


  • Cause: surgical trauma; incisional infection: one of the most common complications of abdominal laparotomy. Defect in abdominal wall permits eventration of viscera into subcutaneous space.
  • Signs: visible or palpable swelling at incision site, may be associated with wound drainage, infection or dehiscence; abdominal pain or discomfort.
  • Diagnosis: observation, palpation, ultrasound, fine needle aspiration; surgical exploration.
  • Treatment: none → surgical repair with a mesh implant.
  • Prognosis: fair → grave if evisceration occurs.



  • Surgical incision combined with any or all of the following:
    • Excessive tissue trauma → lowers local defense mechanisms.
    • Poor suture technique:
      • Many different types of suture material and suture patterns have been used and investigated in the closure of the linea alba.
      • Many surgeons use a simple continuous suture pattern Surgery: suture patterns - basic patterns which has been found to have a high level of bursting strength.
      • The optimal tissue bit size in adult horses has been determined as 15 mm from the edge of the linea alba.
    • Wound contamination and infection → bacterial numbers overwhelm local defense mechanisms. Incisional infection is common prior to herniation with one paper demonstrating a 62.5 times more likely risk of developing a hernia with incisional infections.
    • Excessive movement at the wound site, eg due to pain or exercise.
    • Drainage from the incision (an indicator of abnormal wound healing).
  • Delayed wound healing Wound: healing - factors → weakened abdominal fascia → herniation of omentum +/- intestine.
  • Flank incisions have a greater likelihood of creating dead space, tissue necrosis and muscle trauma during surgery. One paper reported an 88% incidence of complications in celiotomy incisions versus the ventral midline.

Predisposing factors


  • Abdominal surgery.


  • Repeat abdominal surgery (only 70% of fascial strength returns after 1 year). Various studies have suggested a 2-3 times increase after re-laparotomy.
  • Surgery lasting >2 h.
  • Difficulties associated with anesthetic recovery.
  • Incisional edema may affect local tissue oxygen tension and delay wound healing, suppress local immune function, and provide an optimal environment for bacteria.
  • Incisional drainage - especially if purulent rather than serosanguinous.
  • Post-operative leukopenia Blood: leukocytes.
  • Post-operative pain.
  • Old age.
  • Large size.
  • Uncontrolled post-operative exercise.
  • Inappropriate suture material - type or size Surgery: suture materials - overview. Use of chromic gut suture in the linea alba.
  • The occurrence of incisional complications, including herniation, after closure of equine celiotomies with USP 7 polydioxanone Surgery: suture materials - overview sutures was recently found to be low.
  • Incisional infection (reported in 25% of herniations).
  • Use of near-far-near suture pattern Surgery: suture patterns - basic patterns.
  • Excessive dissection of the linea alba prior to closure.


  • Incisional hernias occur in 5.7-18% of horses following ventral midline celiotomy.

Incisions along the ventral midline generally carry a lower rate of complications than incisions located elsewhere on the abdomen, eg flank. This is not, however, the case for incisional herniation which appear to be more common post-ventral midline celiotomy for colic surgery. Incisional hernias are also more common following other incisional complications, particularly serous or purulent incisional drainage.

  • Enterotomy or enterectomy, in which there is potential contamination from spilled intestinal contents, does not seem to increase the risk of wound complications.
  • Incisional hernia may be classified on a scale for wound breakdown:
    • Superficial dehiscence - separation of the skin and subcutaneous tissue alone.
    • Herniation - palpable or visible defect in the abdominal wall with overlying intact skin.
    • Partial dehiscence - separation of the skin, subcutaneous tissue and body wall along part of the incision line.
    • Complete dehiscence - separation of all layers along the entire incision line → evisceration.
  • Up to 20% of horses that develop incisional hernias do not have a single hernia but often multiple small hernias situated along the incision.


  • May occur up to 2 months following surgery.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kilcoyne I et al (2019) Evaluation of the risk of incisional infection in horses following application of protective dressings after exploratory celiotomy for treatment of colic. JAVMA 254 (12), 1441-1447 PubMed.
  • Darnaud S J et al (2016) Are horse age and incision length associated with surgical site infection following equine colic surgery? Vet J 217, 3-7 PubMed.
  • Anderson S L et al (2015) Occurrence of incisional complications after closure of equine celiotomies with USP 7 polydioxanone. Vet Surg 44 (2), 256-264 PubMed.
  • Kelmer G & Schumacher J (2008) Repair of abdominal wall hernias in horses using primary closure and subcutaneous implantation of mesh. Vet Rec 163 (23), 677–679 PubMed.
  • Smith L J et al (2007) Incisional complications following exploratory celiotomy: does an abdominal bandage reduce the risk? Equine Vet J 39 (3), 277–283 PubMed.

Other sources of information

  • Klohnen A, Lores M & Fischer A (2008) Management of Post Operative Abdominal Incisional Complications with a Hernia Belt: 85 horses (2001–2005). In: Proc 9th International Equine Colic Research Symposium. Liverpool, UK.
  • Donawick W J (1989) Repair of Large Body Wall and Skin Defects Including Hernia - Large Animal. Surgery - Soft Tissue Large and Small Animal. In: Proc 115th Post Graduate Committee in Veterinary Science. University of Sydney. pp 259-266.