Introduction

• A hernia can be defined as a protrusion of an organ through the wall of a cavity which normally contains that organ.
• An abdominal hernia is where one or more abdominal organ protrudes to some degree through a congenital or acquired opening in the abdominal wall.
• Congenital hernias are present at birth. The most common of these are umbilical hernias and their diagnosis and treatment is covered elsewhere Umbilicus: hernia.
• Acquired hernias of the abdomen most commonly occur in the midline following breakdown of a ventral midline laparotomy. Lateral abdominal hernias are usually post trauma such as kicks, falls, or collisions with fences, vehicles or other solid objects.
• Complete breakdown of all of the layers of a ventral midline laparotomy (celiotomy) Abdomen: laparotomy leads to eventration of the abdominal contents. Total dehiscence of the abdominal wound either occurs acutely during recovery from the anesthesia for the abdominal surgery or as a delayed post-operative complication.
• Partial breakdown of only the repaired linea alba occurs post-operatively as a complication of healing of the celiotomy. This is the most common cause of a ventral midline incisional hernia Abdomen: hernia - incisional.
• The incidence of ventral midline herniation ranges from 8.1-16% in various studies. Risk factors include post-operative drainage and/or sepsis of the surgical wound, poor surgical technique during the celiotomy, and repeat celiotomy.
• Midline incisional hernias often do not appear immediately and commonly are identified several months after the surgery.
• Not all incisional ventral midline hernias require surgical repair. Usually it is repaired either for cosmetic reasons or where the animal is to undertake athletic work or breeding (pregnancy).
• Incarceration within the hernia is rare.

Uses

• Repair of midline ventral midline incisional hernias Abdomen: hernia - incisional.

Advantages

• Returns the abdominal wall to normal strength.
• Improves the cosmetic appearance.

Disadvantages

• Cost.
• Requires a general anesthetic Anesthesia: general - overview and considerable aftercare.

Requirements

Preparation

Procedure

Aftercare

Outcomes

Prognosis

• Primary closure without the use of a prosthetic mesh:
  • Used successfully to repair hernias up to 28 cm long or 18 cm wide.
  • Short-term complications in 4 of 38 horses undergoing this repair and included partial failure of the repair.
  • Long-term complications were only 4 %.
• Prosthetic mesh onlay with primary closure:
  • Results of this technique vary in the literature with one author describing good results and minimal complications in over 75 horses where this technique was used. In another study, a high incidence of complications was reported (4 of 9 cases), including colic and implant infection (post-discharge from hospital).
  • Two of the horses required subsequent implant removal to resolve the infection.
  • This technique has the advantage of simplicity, limited dissection and good cosmesis. Rarely does the mesh become infected and it is easily removed if it does.
• Prosthetic mesh inlay (interposition):
  • This technique is not popular in human medicine because of high recurrence levels of the hernia post repair.
  • It is rarely used in horses, but one report discussed its use in 3 cases of incisional hernia after ventral midline celiotomy.
  • All 3 cases experienced no complications.
• Prosthetic mesh sublay with primary closure or with fascial overlay:
  • A retrospective study of incisional hernia repair in 13 horses (> 450 kg bodyweight) which underwent preperitoneal sublay mesh implantation revealed that all the horses exhibited signs of mild to moderate abdominal pain Abdomen: pain - adult in the first 24 h post-operatively.
  • Seroma/hematoma Hematoma formation at the site of surgery was present in all cases, with 8 developing incisional drainage.
  • All complications were managed in all but one of the cases by local and/or systemic antimicrobial drugs Therapeutics: antimicrobials, and drainage of the seroma/hematoma by stab incisions.
  • Three horses had disruption of the internal abdominal oblique muscle near the mesh-tissue interface leading to a painful swelling.
  • Long-term follow-up revealed 6 of 12 horses were euthanized post-operatively for recurrent abdominal pain Abdomen: pain - adult (4), laminitis (1) or hernia recurrence (1) post parturition.
  • A better outcome was reported in another study of 15 horses where incisional hernias were repaired using preperitoneal sublay of a folded polypropylene mesh.
  • Complication over a 6 month period in the 14 surviving cases included recurrent colic (1), failure in the repair after a fall (1), abscess formation which resolved with drainage (1), and moderate-severe incisional edema which resolved with time (3).
  • One horse was euthanized due to an unrelated problem.
  • Recently, a preperitoneal sublay placement of a novel absorbable silk mesh was reported in a 600 kg horse with good results.
• Laparoscopic repair with intraperitoneal mesh underlay:
  • Post-operative complications noted in 5 horses that underwent this surgery, included signs of parietal pain when the site of the repair was palpated at 24-72 h after surgery (5), and drainage from one of the stab incisions which required 5 days of antimicrobial treatment Therapeutics: antimicrobials to resolve (1).
  • All 5 horses had a good functional and cosmetic outcome.

Further Reading

Publications

Refereed Papers

• Recent references from PubMed and VetMedResource.
• Whitfield-Cargile C M et al (2011) Comparison of primary closure of incisional hernias in horses with and without the use of prosthetic mesh support. Equine Vet J Suppl (39), 69-75 PubMed.
• Caron J P & Mehler S J (2009) Laparoscopic mesh incisional hernioplasty in five horses. Vet Surg 38 (3), 318-325 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.
• Freeman D E (2005) Management of ventral incisional hernias in large horses: a surgical challenge. Equine Vet Educ 17, 247-251 WileyOnline.

Other sources of information

• Toth F & Schumacher J (2018) Abdominal Hernias. In: Equine Surgery. 5th edn. Eds: Auer J A & Stick J A. Elsevier Saunders, USA.