Any lesion that will not resolve with medical treatment alone. ref. medicine notes and see site specific lesions below.

generally ventral midline laparotomy incision under GA

The equine stomach capacity approx. 15L, not possible to exteriorise the stomach at surgery, but impactions can occasionally be surgically treated.

1. pyloric stensosis

2. Gastric impaction/dilatation  

Foals up to 4 months; congenital (rare) or acquired (secondary to gastroduodenal ulceration healing by fibrosisstricture formation). Diagnosis: contrast radiography shows delayed outflow. Treatment = pyloromyotomy or bypass the pylorus with a gastrojejunostomy. 

Aetiology unclear - ?due to ingestion of unsuitable feed (coarse, dry), primary motility problem or secondary to liver disease. Diagnosis very difficult – often made at surgery. Surgical evacuation may be attempted but the risk of abdominal contamination is high because the stomach cannot be isolated outside the abdomen. Spontaneous rupture may occur. 

1. Ileal/ jejunal impaction 

May occur in association with certain diets (e.g. Bermuda grass hay in the US) or with severe Ascarid infestation in young horses or possibly related to tapeworm burden. Treatment = decompression (via enterotomy if required). Prognosis = good. 

2. Intestinal neoplasia 

Tumours of the GIT  thickening of the intestinal wall  complete/partial obstruction. Lymphosarcoma = most common. Weight loss often also present. If focal can resect affected portion of gut. Often multifocal  resection not possible. Long-term prognosis usually poor. 

3. Anterior enteritis

Aetiology unknown - ?salmonella/clostridia/diet?  marked distension of proximal SI and stomach, may resemble a surgical colic . Treatment: medical = repeated nasogastric intubation or surgical = manual decompression of SI. Prognosis: 50-70% survival. 

Strangulating obstructions of the small intestine 

Once cause ascertained treatment usually involves reduction of the strangulation + resection of ischaemic gut followed by anastomosis of proximal and distal portions of gut
i.e. end to end or side to side: jejuno-jejunostomy, jejuno-ileolstomy, jejuno-caecostomy. Prognosis depends on length of gut affected, duration of obstruction and consequent cardiovascular/endotoxaemic status of horse and lesion type but around 60-85% survival. 

Duodenum (1m) attached to right dorsal body wall by a short mesoduodenum preventing exteriorisation. Jejunum=15-30mlong,long(50cm)mesojejunumcanexteriorise. Ileum(70- 80cm) has slightly thicker wall (more muscle) and a distinctive antimesenteric band (ileocaecal fold  dorsal taenia of caecum) and although short, is commonly involved in surgical colics. The distal ileum and ileocaecal junction cannot be exteriorised. 

Most common cause of SI strangulation, especially in mature/obese animals. Lipoma is often suspended on a single fibrous band attached to the mesentery  encircles a bowel segment  strangulates intestinal vasculature. 

 Small intestinal volvulus 

Rotation of some/all of jejunum about its attachment in the dorsal abdomen at the cranial mesenteric arterial root. Often severe pain and poor prognosis due to amount of gut affected. Volvulus may be secondary to other lesions causing SI distension. 

3. Intussusceptions 

Invagination of the proximal intussusceptum into the distal intussuscipiens initially  simple obstruction, then  strangulating as more gut entrapped and arterial supply is drawn in. May involve any segment of bowel but jejuno-jejunal intussusceptions more common in foals. Ileo-caecal intussuceptions associated with tapeworm infestation (Anoplocephala perfoliata) – may require bypass of the ileo-caecal junction. 

4. Thromboembolic colic 

Mesenteric vascular thrombi = result of the migration of Strongylus vulgaris larvae  vascular infarction of a segment of SI which can be extensive. These lesions, formerly the most common cause of SI colics have become rarer since the widespread use of avermectin parasiticides. 

SI Entrapment: 

• Epiploic foramen entrapment: boundaries = caudal vena cava, caudate lobe liver, pancreas,

  (hepatic portal vein). Often hard to diagnose because entrapped gut is cranial to the liver 

  may be no abnormal rectal findings and normal peritoneal tap

• 
  

    Inguinal/scrotal hernia: usually breeding stallions. Swollen inguinal region. Palpate SI

  entering inguinal ring per rectum.

• 
  

    Herniation through a mesenteric rent: ?spontaneous rent or broodmare after parturition

  (foetal foot)

• 
  

    Gastro-splenic ligament: rare

• 
  

    Umbilical hernia: up to 15% of umbilical hernias may  SI strangulation

•   Diaphragmatic hernia: rare – ?congenital or after major traumatic episode. 

0. Surgery specific Caecal Anatomy:
   Only apex and part of body exteriorisable at laparotomy. Often used as ‘starting point’ for exploring abdomen. Dorsal bandileo-caecal fold. Lateral bandventral colon. 

0. Primary impaction or secondary to motility disorder, common in hospitalised patients e.g. after GA or repeated sedation. Diagnosis + medical treatment  see medicine notes. Surgery indicated if no response to medical treatment because the caecum is prone to spontaneously rupture ( death).

   Surgery = evacuation via an apical typholotomy often recurs if primary motility problem.

   Caecocaecal and caecocolic intussusception +/- caecal bypass (ileocolostomy) because condition 

Caecocaecal and caecocolic intussusception 

Caecocaecal intussusception (usually starts at apex) does not cause a total obstruction unless it progresses to obstruct the caecocolic area, at which point it is a simple obstruction. Further progression  caecum can pass through into the RVC + draws in the caecocolic artery  strangulating lesion. A firm mass may be palpable per rectum in the caecal base in some cases. Often initially present with mild to moderate pain, and progress slowly until complete obstruction occurs; at which point  more rapid deterioration. Treatment of caeco-caecal = simple reduction if little damage, partial typhylectomy. Treatment of caeco-colic = enterotomy in the RVC and resecting the inverted caecal ischaemic stump from within the lumen (v.messy!) + jejunocolic anastamosis. 

CaecumRVCLVCLDCRDCtransverse colonsmall colon
Origin of RVC firmly attached proximally to the fixed caecal base, and RDC to the dorsal body wall i.e. these portions not exteriorisable at surgery. Left colons = highly mobile displacements and torsions occur commonly.

N.B. Distension/secondary impaction of the large colon occurs secondary to most colonic disorders and evacuation of the colon is commonly indicated to ease manipulation of the colon and may improve post-operative motility. This is usually performed via an enterotomy at the pelvic flexure. 

Large colon displacements N.B. see medicine notes on these conditions 

Causes: gaseous distention, transient motility disorders, sudden dietary changes, parturition, idiopathic. 

• Left dorsal displacement (aka nephrosplenic entrapment):  

• Colon becomes entrapped between dorsal aspect of spleen and nephrosplenic ligament adjacent to the left kidney. Total or partial (simple) obstruction and variable pain. Diagnosis + medical treatment: see medicine notes. Severe cases with secondary impactions which do not respond to medical tx need surgery to reduce displacement. The prognosis is generally good. 

• Right dorsal displacement  

• The left colons migrate around the body of caecum (clockwise or anticlockwise). Diagnosis and medical treatment: see medicine notes. Indication for surgery = unremitting pain, increasing distension, deteriorating CV status (some cases progress to colonic volvulus). If no volvulus, good (70-80%) prognosis of success. Colopexy to the abdominal wall can be performed if colon displacement recurrs (breeding mares) but has high rate of complications (wt loss, chronic colic, colon rupture). 

0. Colon volvulus/torsion 

0. Torson often around caecolic junction  whole colon involved. Can be 180 degrees (possibly non strangulating) to 360 degrees (strangulating) Extremely painful, rapidly deteriorating patient due to massive endotoxaemia. Treatment = surgical correction +/- colonic resection (if neccessary). If survive surgery, prone to acute colitis + systemic effects of endotoxaemia postoperatively. The prognosis is guarded unless surgically treated early 

0. Enterolithiasis 

0. rare in the UK. Mineralised enteroliths tend to obstruct narrow transverse colon. Tx = Surgical removal of the enteroliths via an enterotomy carries a good prognosis. 

Atresia coli 

A heritable congenital condition of foals, which results in atresia of a segment of colon and/or atresia ani. Diagnosis = contrast radiography, surgical correction possible if segment missing is not too long. 

Small colon impaction 

Focal enterolith (US) or primary motility dysfunction, ? assoc. with Salmonellae?. Tx=manual decompression or enterotomy at surgery. 

Rectal prolapse 

Graded 1-4 in increasing severity, grades 3 and 4  guarded prognosis because mesorectum tears. Tx: Mild = clean, resect affected mucosa + replacement, provided the seromuscular layer is intact. Prolapse > 25-30 cm  probable mesocolon rupture,  more aggressive surgery - refer. 

Rectal tears 

Usually occur during rectal palpation. Graded 1-4, depending on the depth: grade one = mucosa only, grade 2 = muscularis only, grade-3 = mucosa and muscularis and grade 4 tears involve all layers, and result in abdominal contamination with faeces = life threatening. Most important step is to realise and identify the lesion early, report it to the owner, institute appropriate first aid + refer if necessary. It is very unadvisable to attempt to cover it up.

First aid = sedate, give epidural or large volume of local anaesthetic per rectum, careful evacuation and packing of the rectum to prevent further contamination, broad-spectrum antibiotics non steroidal anti- inflammatories, then referral/surgery in the case of severe lesions. Grade 3 and 4 lesions carry a guarded but not hopeless prognosis. Surgical management of severe lesions = temporary colostomy, temporary rectal liners or attempted primary surgical repair of the tear. 

Repeat episodes of colic:

Common, especially in first year post surgery. Severity varies markedly. May require repeat laparotomy. 

Ileus:

Prevalence = 20%. Ileus (lack of peristalsis) may result from inflammation (peritonitis, handling at surgery, systemic effects of endotoxaemia), distension (obstructive problem e.g. at anatomosis site) or denervation (grass sickness). Ileus  further distension and pain + dehydration if SI or impaction if LI affected. Diagnosis: rectal or abdominal ultrasound  distended loops of SI with little movement, nasogastric intubationreflux. Treatment = reflux as necessary, supportive therapy, motility stimulants (e.g. lignocaine, cisapride, metaclopramide). Stomach may rupture if not refluxed regularly. 

Incisional drainage/infections/herniation: 

Prevalence = 10-40%. Predisposes horses to incisional herniation at later date. Tx: early recognition, bacterial culture, establish drainage, lavage wound if necessary, ? belly bandage. 

Adhesions: 

Usually weeks after surgery – fibrinous then fibrous adhesions may cause intestinal obstruction, strangulation etc  recurrence of colic. Prevention = careful tissue handling, use of anti-adhesion therapy e.g. carboxymethylcellulose, heparin, seprafilm, peritoneal lavage. Tx = laparoscopic or open adhesiolysis if possible.