Surgical Disorders of the GI tract Flashcards
Describe the approach to exploration of the equine abdomen
-mainly use ventral midline incisions with the horse in dorsal recumbency (other approaches are paramedian, inguinal or standing flank)
-systematic gas decompression can help with examination of the GI tract (large colon)
-find the ileocecal fold and follow orally to the duodenocolic ligament
-follow the ascending colon (large colon) from the cecocolic fold to the pelvic flexure- this can be aided by exteriorizing the ascending colon- palpate and examine fully
-for the descending colon, palpate for bands and fecal balls. Exteriorize following orally and caudally (or start at rectum and follow cranially)
-palpate the stomach, duodenum, transverse colon, liver, spleen, diaphragm, kidneys, and GI tract
What are the main areas for simple obstructions?
-stomach
-ascarid impaction
-cecal impaction
-small colon impaction
-large colon impaction
-meconium impaction
*in areas where there are changes in diameter
What are the main causes of gastric impactions? How can you diagnose and treat these?
-typically consist of excessive dry, fibrous ingesta but can also be due to ingestion of material that forms a mass, such as persimmon seeds or mesquite beans
-can also be due to feeds that swell after ingestion, such as what, barley, and beet pulp
-dental disease and inability to properly chew can also predispose
Diagnosis: endoscopy, but usually diagnosed at time of surgery (unfortunately), US can be useful during workup
Treatment: gastric lavage via NG tube, inability to exteriorize stomach during surgery makes it difficult to surgically evacuate (risks of septic abdomen), cannot be corrected in surgery
What age range are ascarid impactions most commonly seen?
Foals and weanlings 4-24 months of age
-foals usually appear parasitized and unthrifty, impactions usually occur after anthelminthic treatment (54-72% of cases)
-can also occur in intestinal stages of the parasite- resistance to anthelminthics puts young horses at increased risk
How can you treat parascarid equorum impactions?
-best case: milk the ascarids into cecum allowing them to pass into the feces (requires a lot of manipulation of bowel which can lead to adhesions)
-in very severe cases you may need to perform enterotomy (try to avoid if possible) or perform R & A if the bowel is devitalized
-prognosis is guarded due to risks of necrotizing enteritis, adhesions, peritonitis and abscess formation
What is the concern with using open fingers when running the bowel?
Can push through the messentery and cause rents (prediposes to bowel herniation)
- also predisposes to inflammation and adhesions
T/F: as an equine vet you should never guarantee an outcome in a colic case
True
Why should you take small bites when closing an enterotomy?
Dont want to cut down the lumen size
What is the most common non-strangulating lesion of the equine small intestine?
Ileal impactions
- usually a primary condition in an apparently normmal ileum
What factor predispose to ileal impactions?
-feeding of bermuda grass- most cases in southeast
What percentage of impacted ileums can be felt on rectal palpation?
10-39%
- can feel distended small intestines in 87% of the cases and small intestine distention can be appreciated on ultrasound in 99% of cases
What is the treatment for ileal impactions?
-can be treated medically with IV fluids and analgesics, take off feed, laxatives (epsom salts-draws fluid into GI tract), lidocaine CRIs, NSAIDs (banamine)
-can also carefully massage the impaction during surgery to help break it down and milk it into the cecum
What is something you can use during surgery to decrease the chance of adhesions?
Coating arms and hands with carboxymethylcellulose
What is the function of the ileum?
Muscular contraction to move materials into cecum (much thicker than other parts of the small intestine)
What are the 2 types of cecal impactions?
Type 1: firm ingesta causes the impaction (more frequent)- often termed “silent killers”. Potential risks include diet, dentition, coastal hay, changes in feed, decreased exercise, decreased water intake, tapeworms, NSAIDs and GA
Type 2: cecal dysfunction preventing cecal outflow into the right ventral colon. The lumen is filled with variable amounts of gas, ingesta and fluid. The wall may be edematous
What are the treatment options for cecal impactions?
Usually medical (fluids, laxatives, NSAIDs, prokinetics like bethanechol) and then surgical if not responding
- 61-81% of horses will respond to medical treatment alone
Surgical options
1. Typhlotomy to evacuate cecal contents
2. Typhlotomy ith partial bypass (jejunocolostomy or ileocolostomy)
3. Typhlotomy with cecocolic anastomosis
*May need to consider typhlectomy of apex if contamination occurs, which is common in these cases. Will function fine
Why are cecal impactions known as silent killers?
Cecum will fill from base to apex
- wont show signs of pain until cecum is full and distended- close to rupture
What is the most humane option when frank ingesta is found in abdomen?
Euthanasia
-less than 5% chance of survival with surgery
What is large colon tympany?
Gas colic or spasmotic colic
-this is the most common type of colic
-there is excessive gas production
-usually self limiting
What are the treatment options for gas colic?
Pain management (banamine), withholding feed, buscupan (antisposmadic)
Where do large colon impactions most often occur?
At the left ventral colon and pelvic flexure, or in the right dorsal colon at the junction of the transverse colon due to changes in diameter
What are some predisposing factors for large colon impactions?
Changes in management and recent or current muscular skeletal injuries
-drug use including atropine (such as for eye trt) and morphine (use very judiciously) can cause
What signs are often seen with large colon impactions?
-mild to severe signs with decreased fecal output
-usually diagnosed on rectal palpation
-if chronic there is a risk of rupture from pressure necrosis
What is the treatment for large colon impactions?
Medical management is usually successful (IV fluids +oral), laxatives, analgesics
-if nonresponsive to medical management, surgical intervention is recommended
-lack of response to pain medication or changes in abdominal fluid are indicative of decline in health of large colon (consider pelvic flexure enterotomy-area of colon you can get farthest from abdomen- and evacuation. cant always access this in every case so can consider other approaches)
Why should you not lift with your hands when lifting an impacted colon out of the abdomen?
Often areas of impaction are thin and friable
-should lift with forearms
-can also lift up with adding fluids to the abdomen
What suture is ideal for closing the abdomen?
2-0 monofilament absorbable suture
- PDS or monocryl
- dont use multifilament as you can seed bacteria into the abdomen
Describe right dorsal displacements
-non-strangulating malposition of the colon resulting in obstruction to passage of digesta and gas without the disruption of blood supply
-clinical signs include mild to moderate pain and abdominal distension
-typically occurs in mature horses and large breeds
How can you diagnose and treat right dorsal displacements?
Diagnosis: confirmed on rectal exam
- the teneae can sometimes be felt to be running horizontally and the pelvic flexure is no longer palpable
Treatment: surgical intervention if medical management fails (easy surgery). Withholding food, IV fluids, analgesics light exercise and CRI lidocaine should be tried first
-can trocarize the colon on right side using 14 ga catheter if surgery is not an option
Prognosis: excellent, chronic displacements can have large colon pexy to decrease chances of other displacements (eliminates athletic performance)
What is left dorsal displacement?
-colon becomes displaced between left body wall and spleen ,and can migrate dorsally to be entrapped in the nephrosplenic space
-diagnosis can be confirmed with rectal and ultrasound (no longer see kidney)
-can be managed medically with rolling, phenylephrine, jogging, before surgery is considered (medical management effective in 75% of cases)
-closure of the nephrosplenic space with laparoscopy standing can be performed for repeat offenders
What is the goal of therapy with phenylephrine in cases of nephrosplenic entrapment?
Causes splenic contraction- as horse is lunged, hopefully can get the colon to slip off of the nephrosplenic space
-causes significant hypertension-risk of aneurisms
What is the issues with colon resection for prevention of future colic?
Colon has ability to expand back to the place it looks like a normal colon
Where does sand impaction usually occur?
In the left ventral colon, but can accumulate anywhere along the GI tract
What horses are at the highest risk of sand impaction?
Horses that are lower in the herds social order or those who are greedy eaters
-living in area with sandy soil, poor husbandry
What clinical signs are associated with sand impaction?
Non-specific: poor performance, weight loss, diarrhea, chronic colic
-horses often febrile and have an inflammatory leukogram (sand causes a lot of inflammation to colon)
How do you diagnose and treat sand colics?
Diagnosis: finding sand in feces (hanging glove test), auscultation of ventral aspect of abdomen close to the xyphoid, radiographs
Treatment: medical via NG tube, surgery if medical unsuccessful (takes a lot to get sand off of abdomen before putting back in- very difficult)
What is the common history of horses that experience enterolithiasis?
-history of being fed alfalfa
-usually have chronic colic signs
