Surgical Disorders of the GI tract

Question 1

Describe the approach to exploration of the equine abdomen

Answer 1

-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

Question 2

What are the main areas for simple obstructions?

Answer 2

-stomach
-ascarid impaction
-cecal impaction
-small colon impaction
-large colon impaction
-meconium impaction

*in areas where there are changes in diameter

Question 3

What are the main causes of gastric impactions? How can you diagnose and treat these?

Answer 3

-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

Question 4

What age range are ascarid impactions most commonly seen?

Answer 4

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

Question 5

How can you treat parascarid equorum impactions?

Answer 5

-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

Question 6

What is the concern with using open fingers when running the bowel?

Answer 6

Can push through the messentery and cause rents (prediposes to bowel herniation)
- also predisposes to inflammation and adhesions

Question 7

T/F: as an equine vet you should never guarantee an outcome in a colic case

Answer 7

True

Question 7

Why should you take small bites when closing an enterotomy?

Answer 7

Dont want to cut down the lumen size

Question 7

What is the most common non-strangulating lesion of the equine small intestine?

Answer 7

Ileal impactions
- usually a primary condition in an apparently normmal ileum

Question 8

What factor predispose to ileal impactions?

Answer 8

-feeding of bermuda grass- most cases in southeast

Question 9

What percentage of impacted ileums can be felt on rectal palpation?

Answer 9

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

Question 10

What is the treatment for ileal impactions?

Answer 10

-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

Question 11

What is something you can use during surgery to decrease the chance of adhesions?

Answer 11

Coating arms and hands with carboxymethylcellulose

Question 12

What is the function of the ileum?

Answer 12

Muscular contraction to move materials into cecum (much thicker than other parts of the small intestine)

Question 13

What are the 2 types of cecal impactions?

Answer 13

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

Question 14

What are the treatment options for cecal impactions?

Answer 14

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

Question 15

Why are cecal impactions known as silent killers?

Answer 15

Cecum will fill from base to apex
- wont show signs of pain until cecum is full and distended- close to rupture

Question 16

What is the most humane option when frank ingesta is found in abdomen?

Answer 16

Euthanasia
-less than 5% chance of survival with surgery

Question 17

What is large colon tympany?

Answer 17

Gas colic or spasmotic colic
-this is the most common type of colic
-there is excessive gas production
-usually self limiting

Question 18

What are the treatment options for gas colic?

Answer 18

Pain management (banamine), withholding feed, buscupan (antisposmadic)

Question 19

Where do large colon impactions most often occur?

Answer 19

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

Question 20

What are some predisposing factors for large colon impactions?

Answer 20

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

Question 21

What signs are often seen with large colon impactions?

Answer 21

-mild to severe signs with decreased fecal output
-usually diagnosed on rectal palpation
-if chronic there is a risk of rupture from pressure necrosis

Question 22

What is the treatment for large colon impactions?

Answer 22

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)

Question 23

Why should you not lift with your hands when lifting an impacted colon out of the abdomen?

Answer 23

Often areas of impaction are thin and friable -should lift with forearms -can also lift up with adding fluids to the abdomen

Question 24

What suture is ideal for closing the abdomen?

Answer 24

2-0 monofilament absorbable suture - PDS or monocryl - dont use multifilament as you can seed bacteria into the abdomen

Question 25

Describe right dorsal displacements

Answer 25

-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

Question 26

How can you diagnose and treat right dorsal displacements?

Answer 26

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)

Question 27

What is left dorsal displacement?

Answer 27

-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

Question 28

What is the goal of therapy with phenylephrine in cases of nephrosplenic entrapment?

Answer 28

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

Question 29

What is the issues with colon resection for prevention of future colic?

Answer 29

Colon has ability to expand back to the place it looks like a normal colon

Question 30

Where does sand impaction usually occur?

Answer 30

In the left ventral colon, but can accumulate anywhere along the GI tract

Question 31

What horses are at the highest risk of sand impaction?

Answer 31

Horses that are lower in the herds social order or those who are greedy eaters -living in area with sandy soil, poor husbandry

Question 32

What clinical signs are associated with sand impaction?

Answer 32

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)

Question 33

How do you diagnose and treat sand colics?

Answer 33

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)

Question 34

What is the common history of horses that experience enterolithiasis?

Answer 34

-history of being fed alfalfa -usually have chronic colic signs

Question 35

What is the diagnosis and treatment of enterolithiasis?

Answer 35

Diagnosis: radiographs - most seen in right dorsal colon, transverse colon and small colon. large ones are always found in right dorsal colon Trt: most can be removed surgically via pelvic flexure enterotomy

Question 36

What are the risk factors for small colon impactions?

Answer 36

-poor dentition, decreased water intake, poor quality hay, parasite damage, motility issues -horses with small colon impactions are 10X more likely to have diarrhea on presentation

Question 37

How can you diagnose and treat small colon impactions?

Answer 37

Diagnosis: clinical signs of decreased fecal production and straining to defecate + rectal palpation (broad tenae on antimessenteric border) - abdominal fluid usually within normal range Treatment: medical management with IV and oral fluids if tolerated, oral laxatives, NSAIDs, anti-endotoxic trt - if this fails surgery is indicated: manual massage of impaction + small colon enema, cannot evacuate - can consider pelvic flexure enterotomy to rest the small colon - prognosis is gaurded to excellent

Question 38

Describe meconium impactions

Answer 38

-most common cause of colic in newborn foals -normal evacuation should occur 3-24 hours post foaling -clinical signs: tenesmus, pain, distension -treatment: enema (fleet- not more than twice), soapy water, acetylcysteine. Also can use laxatives, IV fluids or surgery but only as last result (very friable intestines, high anesthetic risk)

Question 39

What are some common causes of foreign bodies in horses?

Answer 39

lead ropes/blankets, trash bags

Question 40

What are some common masses that can cause obstructions in the GI tract?

Answer 40

-intramural hematoma -ileal hypertrophy -neoplasia (lymphosarcoma/lymphoma most common- can occur anywhere)

Question 41

What are some causes of ileus in horses?

Answer 41

-Peritonitis -post operative -atropine use -after intense exercise

Question 42

What are some surgical options for enteritis or peritonitis leading to physiological obstructions?

Answer 42

-enteritis- abdominal explore to be sure you arent missing anything -peritonitis- find cause

Question 43

When should you refer obstruction cases?

Answer 43

-if nursing care is inadequate -if there is moderate to severe dehydration -physical exam findings deteriorate -pain increases -duration is longer than expected *simple obstructions still may be surgical- consider abdominocentesis, CBC chem findings and imaging to guide decision

Question 44

How common is thromboembolic colic?

Answer 44

Rare - this is vascular compromise without strangulation

Question 45

What are the common etiologies responsible for thromboembolic colic?

Answer 45

Strongylus vulgaris (likes to live in cranial mesenteric arteries which are the main blood supply to the small intestines), severe colitis (salmonellosis), coagulopathies -cannot do resection & anastomosis in these cases as blood supply to large amounts of the small intestine is necrotic

Question 46

What percentage of the small intestine can be removed without compromising function?

Answer 46

Can take 75% - if you take more than this they will not be able to absorb enough nutrients

Question 47

What is mesocolic rupture of the small colon?

Answer 47

A rent in the mesocolon -most often occurs post foaling (dystocia), but can also occur from straining with diarrhea, intestinal parasitism, colic, proctitis, rectal tumor, cystic calculi and rectal foreign body -results in damage to mesenteric vessels leading to ischemia of the small colon -clinical signs include fever, anorexia, mild colic and scant feces Treatment? R & A- need to be sure to rest adequately post surgery

Question 48

T/F: the small colon has a large amount of collateral blood supply

Answer 48

False -why widespread ischemia is common with damage to the mesentery

Question 49

How long does an R & A rely on the presence of sutures?

Answer 49

3-4 days -wait this amount of time before feeding a large amount of feed material

Question 50

What is often seen in addition to the other clinical signs with mesocolic rupture?

Answer 50

Prolapse of the rectum - if small colon is involved, resection is needed (often done externally (standing) through prolapsed tissue) - if small colon is not involved, reduce prolapse and treat primary problem

Question 51

What is the prognosis associated with mesocolic rupture?

Answer 51

Good when the small colon is not involved, gaurded when R and A is performed (there is a chance that compromised bowel is still in the abdomen)

Question 52

What are the signs of septicemia in the horse?

Answer 52

Shock line on the gums, tachycardia, fever, and hemoconcentration - third spacing - will dump fluid into abdomen and it will be hard to keep up with their hydration

Question 53

What is the normal PCV in horses?

Answer 53

35-40% -for managing horses post op- ok to keep at 45% to prevent excess abdominal edema and to prevent overhydration -try to prevent TP from going below 4.5

Question 54

What are the fluids that you would use to help a colicy horse maintain its oncotic pressure?

Answer 54

Colloids or plasma -colloids will change oncotic pressure, but will not affect total protein

Question 55

What are some subjective measures that can help you to determine prognosis during surgery of strangulating obstructions?

Answer 55

Return to normal color of tissue after untwisting the strangulation -can also flick with finger to stimulate peristalsis- if doesnt move this is a bad sign

Question 56

For ischemia to develop, how much does the bowel have to rotate?

Answer 56

360 degrees

Question 57

What is the maximum amount of time that colic surgeries should last?

Answer 57

3 hours - after this point prognosis goes down

Question 58

How do you manage a horse with endotoxemia?

Answer 58

Polymixin B- binds LPS - binds the toxins that gram negative bacteria produce that cause endotoxemia - other drugs that may help are banamine and lidocaine CRIs

Question 59

What is the most common cause of strangulating lesion in horses?

Answer 59

Strangulating lipomas - one of the most common cause of colic in older horse (14-19) - they are benign smooth wall fat tumors suspended on a thin mesenteric stalk of variable length - all portions of the GI tract can be affected- most often the jejunum and ileum are affected (89% found in small intestines, 10% in small colon)

Question 60

What are the clinical signs associated with strangulating lipomas?

Answer 60

-severe colic in the acute stage -often there is a serosanguinous abdominal tap -distended loops of small intestine +/- reflux. Early referral improves chance of survival

Question 61

T/F: most of the horses that get strangulating lipomas are overweight?

Answer 61

False

Question 62

Describe the treatment for strangulating lipomas

Answer 62

-often you must break the stalk of the lipoma blindly because you are unable to exteriorize the affected area

Question 63

What is the survival rates expected for strangulating lipomas?

Answer 63

range from 48-84%

Question 64

What is the challenge with performing an ileojejunal anastomosis with a strangulating lipoma?

Answer 64

There is a significant difference between the thickness of the wall of the jejunum and ileum

Question 65

What is the issue with joining the jejunum to the cecum in cases of strangulating lipoma?

Answer 65

The ileum functions to contract and squeeze things into the cecum - without the ileum functioning, ileus often results - lower prognosis for survival

Question 66

Describe epiploic foramen entrapments

Answer 66

-most cases are from left to right in the epiploic foramen (4 cm wide) -horses of any age can be affected, care is needed in reducing the entrapment -upward tension can cause damage to the portal vein resulting in death -the ileum is involved in most cases (81% of the time) -changes in the peritoneal fluid does not always reflect the damage to the entrapped bowel -can reoccur- can place explandable mesh to obliterate the space (but creates potential nidus of infection)

Question 67

What are the borders of the epiploic foramen?

Answer 67

The portal vein, the pancreas, the caudal vena cava, and caudate lobe of the liver

Question 68

Describe the surgical treatment for epiploic foramen entrapment?

Answer 68

Need to feed normal bowel into the space while pulling edematous tissue out - or pull everything through foramen, do R and A and then pull everything back through

Question 69

What is the most important rule when doing surgery to correct epiploic foramen entrapment?

Answer 69

Never pull upwards- can lead to tearing of the portal vein -need to pull caudally to stretch the epiploic foramen (very horizontally)

Question 70

What is volvulus?

Answer 70

Its a rotation of the jejunum and ileum around its mesentery resulting in ischemia to the bowel -most are 360 degrees or more, can be segmental or at the root of the mesentery -can affect horses of any age but most are >3

Question 71

What is the most common indication for abdominal surgery in foals especially 2-4 months of age?

Answer 71

Volvulus

Question 72

What is the treatment for volvulus?

Answer 72

correction of the volvulus +/- resection and anastomosis

Question 73

What type of horse is most affected by inguinal hernias?

Answer 73

Stallions (96% of cases), but can also occur in geldings -incidence is higher in standardbreds, tennessee walking horses and american saddlebreds

Question 74

What is the type of bowel that is most commonly implicated in inguinal hernias?

Answer 74

Jejunum and ileum -most are indirect herniations (within the vaginal tunic)

Question 75

What is the recommended treatment for inguinal hernias?

Answer 75

Hemi castration and closure of the external inguinal ring

Question 76

What is the common presentation associated with large colon volvulus?

Answer 76

-usually present with unrelenting pain -can display signs of hypovolemic shock and cardiovascular instability -early referral is imperative to improve survival -any horse can be affected but mares post foaling are at an increased risk -horses are usually very painful and non-repsonsive to pain control, have distened abdomen

Question 77

What is large colon volvulus?

Answer 77

-twisting of the colon around its mesentery -volvulus past 360 degrees is considered a strangulating lesion -usually occurs at the base of the cecum in a counterclockwise fashion, but can also occur at the sternal or diaphragmatic flexures

Question 78

Describe the surgical approach to large colon volvulus?

Answer 78

- simple correction +/- enterotomy -can infuse biosponge prior to closing pelvic flexure enterotomy -colon resection should be considered if the colon distal to the volvulus is no longer viable, then a colon resection should be considered -need extensive supportive care post op -prognosis is considered guarded to favorable (50-70% survive to discharge)

Question 79

What is the concern with using detomidine to manage a painful colic?

Answer 79

It can mask severe pain - you could be dealing with a surgical lesion

Question 80

What is the purpose of using biosponge in cases of large colon volvulus?

Answer 80

Binds endotoxins in the colon -prevents profound endotoxemia post op -also consider polymyxin B intraoperatively

Question 81

What predisposes to intussusceptions?

Answer 81

Anything that alters motility; enteritis, parasites (ascarids or tapeworms), abrupt dietary changes

Question 82

How can you diagnose intussusception?

Answer 82

Diagnosis is challenging, but it is supported by small intestine distension and abnormal abdominocentesis -definitive diagnosis often at surgery -can sometimes see bullseye lesion on ultrasound -most often occurs in horses less than 1 year

Question 83

Describe the different types of intussusceptions

Answer 83

-Can involve either the small or the large intestines -short intussusceptions: incomplete obstructions that cause chronic or intermittent colic (ileocecal most common), horse may be unthrifty -long intussusception: strangulating lesion

Question 84

Describe diaphragmatic hernias

Answer 84

-they are very difficult to diagnose pre-op -may see abdominal viscera in the thorax on US or radiographs -always a surgical lesion -not always repairable (use hernia needle to avoid large vessels)

Question 85

How do you close the abdomen after a colic surgery?

Answer 85

-close linea with large absorbable suture (2 or 3) in a simple continuous or interupted pattern with bits 1.5 cm away from wound margin -to reduce the incidence of infection the linea should be lavaged with sterile saline prior to and after closure of the linea -some surgeons will bathe the linea with an antibiotic after closure of the linea -the subQ tissue is usually closed with a 2-0 monofilament absorbable suture in a simple continuous pattern -skin is usually closed with skin staples, or some surgeons use subcuticular suture with a 2-0 or 3-0 monofilament absorbable suture

Question 86

What is the tool used to hold the intestines in when closing the abdomen?

Answer 86

The FISH aka the visceral retainer

Question 87

Describe the anesthetic recovery and aftercare in surgical colic cases

Answer 87

-can have free recovery, head and tail ropes, inflatable pillows, or sling recovery (not advised with colic) -aftercare: antibiotics, fluids, lidocaine CRI, NSAIDs, ice boots, belly band, polymyxin B, controlled refeeding, belly band with sterile padding against incision (kerlix), stall rest for 50-60 days with hand walking (linea takes this amount of time to get up to maximum strength which is between 80-85% of original strength)

Question 88

T/F: strangulating lesions are always surgical

Answer 88

True