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EQUINE VETERINARY EDUCATION / AE / OCTOBER 2014
Clinical Commentary Congenital body wall defects in horses
J. F. Hawkins Large Animal Surgery, Purdue University, West Lafayette, Indiana, USA. Corresponding author email:
hawkinsj@purdue.edu
Keywords: horse; congenital; hernia; mesh; herniorrhaphy
Introduction In this issue, Hill and Story (2014) describe a surgical repair of a congenital lateral abdominal wall hernia in a neonatal foal. The most common congenital body wall defect in the foal is the umbilical hernia (Markel et al. 1987; Freeman et al. 1988; Riley et al. 1996; Kummer and Stick 2012). Other sites for congenital body wall defects include caudal to the umbilicus, inguinal and paracostal. All congenital body wall defects consist of a smooth hernial ring, a hernial sac and excess skin. In the majority of cases the hernial contents are nonstrangulating and are readily reducible with manual manipulation of the hernia. The most common clinical sign of a congenital body wall defect is a soft, nonpainful reducible swelling. Most hernias can be readily diagnosed with physical examination, although ultrasonography or abdominal radiography can be useful.
Evaluation
All foals presenting with a soft, nonpainful fluctuate swelling compatible with a hernia should be manually palpated. Manual palpation allows the surgeon to determine whether or not the contents are fully reducible. A nonstrangulating routine hernia should be fully reducible with manual palpation. However, small hernias can incarcerate intestine and be painful to palpation and may or may not be reducible (Markel et al. 1987; Freeman et al. 1988). Next, the edges of the hernia should be evaluated. If surgical repair is planned a fibrous hernial ring should be palpable. Thin hernial rings or muscle defects without a hernial ring may require mesh herniorrhaphy. If the contents of the hernia are not fully reducible adhesions or infection within the hernial sac should be suspected. Ultrasonography can be useful in cases suspected of adhesions or infection to further evaluate the contents of the hernial sac and the abdominal cavity (Reef and Collatos 1988; Reef et al. 1989). If ultrasonography is not available, abdominal radiography can be useful in determining what abdominal viscus may be located within the hernia sac. In most situations, the author generally does not pursue abdominal radiography for the evaluation of congenital body wall defects as ultrasonography is the most useful diagnostic tool in combination with manual palpation. Following the aforementioned diagnostics, a surgical plan
should be discussed with the owner. In nearly all instances, surgical repair is recommended to the owner. The biggest decision the surgeon needs to make prior to definitive repair is whether or not prosthetic mesh will be required to close the hernia defect (Tulleners and Fretz 1983; Whitfield-Cargile et al. 2011; Kummer and Stick 2012). The decision for prosthetic herniorrhaphy depends on 2 things: hernial size and quality of the hernial ring. The reason mesh herniorrhaphy should be discussed with the owner is because of the additional
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cost of mesh compared to routine suture closure and increased risk for infection post operatively. If mesh herniorrhaphy is a possibility, the mesh should be procured prior to surgical correction.
Management
The author is not aware of a conservative method of correction for congenital body wall defects. However, there are anecdotal reports of repeated manual reduction of hernias and successful closure of small defects. In addition, there are veterinary surgeons who are proponents of clamping umbilical hernias and recommend their use for routine umbilical hernias (Riley et al. 1996). The author does not recommend hernial clamps for management of umbilical or other congenital body wall defects and does not offer it to owners, the primary reason being that the author would rather depend on modern surgical techniques, secure closure of the defect and not depend on granulation tissue formation to hold the body wall together (Brown and Meagher 1978). The author has also observed enterocutaneous fistula formation secondary to nonsurgical management of umbilical hernias (Bristol 1994). Therefore, the author’s preferred method of management
of congenital body wall defects is suture or mesh herniorrhaphy. The main surgical principles related to repair of congenital body wall defects are excision of the hernial sac, tension free closure of the body wall and elimination of dead space. Unlike mature horses, foals are not withheld from food for more than 12 h prior to surgery. Feed withdrawal can lead to hypoglycaemia, if the foal is still nursing, and abdominal size is not ‘bulked’ up with hay or other roughage. Surgery begins with the foal being anaesthetised and
positioned in dorsal recumbency. Regardless of the location of the body wall defect, an elliptical incision is made around the hernial sac. In most instances with positioning in dorsal recumbency, the contents of the hernia reduce into the abdominal cavity. If the contents of the hernial sac do not reduce into the abdominal cavity, then adhesions or infection within the hernia are suspected. Once the skin surrounding the hernial sac has been incised, the subcutaneous tissue surrounding the hernial sac is bluntly and sharply dissected from its connective tissue attachments until only the attachment to the body wall remains. Next, an incision is made cranial to the hernia sac through the full thickness of the body wall so that a finger can be inserted into the abdominal cavity. The finger is used to digitally palpate for adhesions or infected umbilical remnants within the hernial sac. In most instances no adhesions within the hernial sac are present. The most common structure to be adhered in the hernial sac is omentum and less commonly is intestine (e.g. ileum, small intestine, large colon, or caecum).
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