Page 887 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

862 CHAPTER 4

VetBooks.ir administration and reproductive complications such cellulitis or rectal-wall necrosis that can eventually
result in abdominal faecal contamination. Grade 4
as dystocia and breeding injury. Spontaneous tears
are rare, but they have been described and, presum-
the abdominal cavity, which leads to septic peritonitis,
ably, result from thromboembolism of the caudal tears usually result in massive faecal contamination of
mesenteric artery. septic shock and ultimately death (Fig. 4.176).
Pathophysiology varies with the location and
the degree of severity of the tears. The rectum is Clinical presentation
approximately 30 cm long in a 450 kg horse, with its The presence of whole fresh blood on the rectal
oral half being in the peritoneal cavity and the aboral examination sleeve or sudden relaxation of the rec-
portion retroperitoneal. Most tears are located tum during examination is suggestive of a serious
20–30 cm from the anus and therefore are within the rectal injury. Clinical signs may not be present in
peritoneal cavity. A classification reflecting degree of the short term even after serious tears. Tenesmus,
severity has been established: abdominal pain, tachycardia, pyrexia and ileus may
develop within hours after the injury. Horses with
• Grade 1 tears: only the rectal mucosa and grade 4 rectal tears develop septic shock and perito-
submucosa are torn. nitis very shortly after the injury.
• Grade 2 tears: the rectal muscularis layer is torn,
causing the mucosa and submucosa to form a Diagnosis
diverticulum as they protrude through the defect. The aim of evaluating horses with rectal tears is to
• Grade 3 tears: in grade 3a tears, all the layers are determine immediately the location, size and depth
affected except the serosa; in grade 3b tears all of the tear. This is performed after the horse is well
the layers are affected except the mesorectum. sedated and epidural anaesthesia has been admin-
• Grade 4 tears: these are complete tears involving istered. The rectum should be carefully evacuated.
all the rectal wall layers. Digital palpation with bare hands is the most valu-
able procedure for assessing the location, size and
Grade 1 tears are usually not associated with compli- depth of the tear. Endoscopic evaluation of the rec-
cations. In grade 2 and 3 tears, faecal material becomes tum is useful for assessment of the tear (Fig. 4.177).
impacted in the defect, leading to the development Care should be used to prevent excessive insuffla-
of a perirectal or retroperitoneal abscess, dissecting tion of the rectum during the procedure in order

4.176 4.177

Fig. 4.176 Typical post-mortem appearance of an Fig. 4.177 Endoscopic image of a mare with a grade
iatrogenic grade 4 rectal tear. Note the obvious faecal 4 rectal tear that occurred following palpation for
contamination of the peritoneal cavity. routine reproductive evaluation.