What are causes of luminal obstruction? (7)
- physiologic- ileus from inflammation/ infection, drugs, or idiopathic ileus
- mechanical- FB, intussusception, neoplasia, abscess, granuloma, stricture
What are the local effects of obstruction? (5)
motility altered, blood flow, fluid accumulation, gas accumulation, bacterial overgrowth
Describe how motility is affected by obstruction.
- Acute: increased oral to FB, decreased aboral to FB (decreased intestinal content)
- Chronic: ileus d/t decreased motor activity
Describe how blood flow is affected with obstruction.
- increasing intraluminal pressure leads to edema d/t lymphatic stasis, capillary stasis, and venous drainage
- the FB itself causes local ischemia, ulceration, necrosis, perforation
Describe fluid accumulation with obstruction. (3)
- retention of swallowed fluid
- increased secretions (d/t stimulation by enteric bacterial toxins and increased secretion of biliary and pancreas systems )
- decreased absorption d/t lymphatic and venous congestion and decreased enterocyte turnover
Describe gas accumulation with obstruction. (5)
- acute: retention of aerophagia, carbon dioxide formation, bacterial fermentation
- chronic: failure to pass, failure of absorption
What is the cause of bacterial overgrowth with obstruction?
- bacterial translocation d/t impaired enteric mucosal barrier and increased permeability and translocation
What are the systemic effects of obstruction? (4)
- dehydration- vomiting, diarrhea, fluid sequestration
- acid-base abnormalities
- bacterial sepsis
- septic peritonitis
What types of acid-base abnormalities might you see with different types of obstructions?
- Distal obstruction: metabolic acidosis- loss of alkaline duodenal, pancreatic, and biliary secretions, loss of sodium and water
- Proximal obstruction: metabolic alkalosis- loss of gastric hydrochloric acid, loss of Cl, Na, K from gastric fluids
What are potential sequelae to septic peritonitis from obstruction? (4)
- proinflammatory mediators-->
What are clinical signs of obstruction? (5)
- [vary with location, chronicity, and completeness]
- vomiting: proximal--> projectile, complete--> frequent vomiting, distal or partial--> intermittent vomiting
- abdominal pain
- diarrhea (less common)
How is obstruction diagnosed?
- 3 views of rads: right and left lateral, VD, +/- FB, gas dilated loops of small bowel. pneumoperitoneum (if perforated)
- +/- contrast radiographs
- +/- U/S: distention, fluid filled intestines, hyper or hypomotility, FB
- Bloodwork: nonspecific, dehydration, electrolyte abnormalities, leukocytosis
How do you identify dilated loops of small bowel on radiographs?
- intestinal diameter should be the same height as the body of L5
- >2x is likely to have obstruction
On exploratory, how do you evaluate bowel for ischemic necrosis? (5)
- arterial pulsations
How do you make you incision for enterotomy?
- if bowel is healthy: incise aboral to the obstruction (in healthy, non-dilated intestine- better healing and closure)
- if bowel is ischemic or perforated: resection and anastomosis
You are surgically treating an obstruction that is secondary to a GI tumor, you...
must do resection and anastomosis!!! with wide margins
What is the prognosis in general for GI obstruction?
- GI FB- usually good
- dehiscence rate 3-27%, increases with hypoalbuminemia, peritonitis, high band neutrophils
- septic peritonitis- 50% mortality rate
- neoplasia- variable
Describe the pathophysiology of linear FBs.
- FB anchors around the base of the tongue or pylorus
- peristaltic waves move the remainder of the FB aborally--> intestines gather or plicate along the object
- over time, object becomes taut and embeds in mesenteric side of lumen
What are clinical signs of linear FB?
- obstruction tends to be partial
How do you diagnose a linear FB?
- oral exam- look under tongue
- plain radiographs- intestines clumped or plicated
- abdominal U/S
- bloodwork- dehydration, leukocytosis
Describe the surgical approach to a linear FB.
- free FB from where it is lodged
- multiple enterotomies (DO NOT PULL IT, you'll saw through the intestines)
- may require R&A, short bowel syndrome
What are potential causes of incarceration and strangulation of bowel? (3 general, 8 specific)
- entrapment: body wall hernia, omental tear, congenital hernia, mesenteric rents, duodenocolic ligament rupture
- mechanical obstruction
- ischemia: mucosal degeneration, bacterial and endotoxin translocation, perforation
How do you surgically treat incarceration and strangulation of bowel?
- stabilize patient first
- ligate blood vessels and resect dead bowel- avoid reperfusion injury
- repair cause of incarceration
What are causes of intussusception? (6)
- young animals: enteritis (parasites (whips), parvovirus, linear FB, recent sx), idiopathic
- old animals: neoplasia
What are common locations for intussusception? (5)
- enterocolic- most common
What are sequelae of intussusception? (3)
- intestinal ischemia d/t occlusion of arterial and venous blood flow
- necrosis and ulceration
How is intussusception diagnosed?
- palpable cylindrical mass
- looks like mechanical obstruction on plain radiographs
- U/S- concentric rings (classic target lesion)
What is the treatment for intussusception?
- surgical reduction- only if the enteric vessels are visible and viable, no ischemia
- R&A- if lesions cannot be reduced, ischemic bowel, neoplasia
- treat underlying condition
- +/- enteroplication (to prevent from happening again)
Describe the pathophysiology of mesenteric volvulus.
- small intestine twists around mesenteric axis
- strangulating obstruction-->venous obstruction--> edema and vascular congestion
- loss of peristalsis
- luminal distention--> fluid and gas accumulation
- mucosal sloughing and hemorrhage
- bacterial proliferation
- usually fatal
What is the most common signalment for mesenteric volvulus?
young male GSD
Describe the treatment of mesenteric volvulus.
- surgical emergency- stabilize patient
- de-rotate intestines (likely to cause reperfusion injury)
- assess for viability
- R&A (short bowel syndrome)
- usually fatal
What are the anatomic locations of the stomach? (4)
- Cardia: gastroesophageal junction
- Fundus: dorsal to cardia, left of midline
- Body: middle third of stomach, left of midline
- Pylorus: pyloric antrum, pyloric canal, and pyloric sphnicter
Describe how to omentum attaches to the stomach.
- greater curvature: superficial leaf of greater omentum
- lesser curvature: lesser omentum
What is the blood supply of the stomach and location of each? (3)
- left and right gastric arteries: on lesser curvature
- left and right gastroepiploic arteries: on greater curvature
- short gastric arteries: from spleen
What is the venous drainage of the stomach?
What are the attachments of the stomach? (2)
- cardia attached to esophagus
- hepatogastric ligament- part of lesser omentum- tethers pylorus and duodenum to the liver
What is the holding layer of the stomach?
submucosa (separates easily from mucosa)
What are the histologic layers of the stomach? (4)
- submucosa- holding layer
- muscularis (3 muscle layers)
- serosa (outside)
What types of cells make up the gastric mucosa, and what is their purpose?
- parietal cells- acid
- chief cells- pepsin
- goblet cells- mucus
Vagal stimulation of the stomach induces...
release of acid
The ____________ is important in grinding food particles and decreasing their size for passage to the duodenum.
What are common indications for gastric surgery? (5)
- gastric FB
- gastric ulceration and erosion
- benign gastric outflow obstruction
What are common electrolyte abnormalities that ideally need to be corrected before gastric surgery?
- loss of Na, Cl, K (d/t vomiting)
- metabolic alkalosis (loss of stomach cid with vomiting)
Describe the use of perioperative antibiotics.
- usually given pre-operatively and continued no more than 24 hours post-operatively
- cephalosporin is a common choice (cefazolin)
Why must you take care when handling the stomach or other GI organs?
excessive inflammation can predispose to adhesions and impaired motility
What surgical principals do you employ to decrease the risk of contamination and peritonitis with gastric surgery? (4)
- stay sutures
- lap sponges
- intraperitoneal irrigation
- clean versus dirty instrument packs
What are indications for gastrotomy? (4)
gastric FB, distal esophageal FB, biopsy, neoplasia
Where do you make a gastrotomy incision?
- least vascularized area, b/w the lesser curvature and greater curvature on ventral aspect
- AVOID pyloric region (avoid stricture)
Describe gastrotomy closure.
- two-layer inverting pattern- cushing or lembert
- simple continuous in mucosa and inverting pattern in remaining layers
What are indications for partial or total gastrectomy? (3)
- devitalized tissue (such as with GDV)
- lesions must involve greater curvature or middle portion of stomach
How do you asses gastric viability when performing gastrectomy? (4)
- gastric mucosal color
- serosal color
- wall texture, vascular patency
- bleeding incision
What are indications for pyloric surgery? (4)
obstruction d/t FB, hypertrophy (chronic hypertrophic pyloric gastropathy or CHPG), ulcerations, neoplasia
What are the types of pyloric surgery?
- Billroth I: gastroduodenostomy
- Billroth II: gastrojejunostomy
What is a pyloromyotomy, and when is it used?
- Fredet- Ramstedt
- correction of gastric outflow obstruction
- increase diameter of pylorus
Describe a pyloromyotomy.
- incise all layers of pylorus except mucosa, let mucosa be only holding layer
- disadvantages- mucosa inspection or biopsy not possible, healing may reduce lumen diameter over time
Describe pyloroplasty and when it is used.
- used for gastric outflow obstruction
- Y-U plasty: Y shaped incision made into pylorus and antrum, antral flap is sutured starting at distal point of duodenal incision
What are the components of GDV? (5)
- increased intragastric pressure
- caudal vena cava compression
- systemic hypotension
- portal hypertension
- CARDIOGENIC SHOCK
Describe the orientation of the stomach with GDV.
- right is normal orientation of pylorus
- pylorus goes from right to ventral to left (180 degree rotation)
- cardia is rotated upon itself
- outflow blocked in both directions (cardia and pylorus obstructed)
Describe the local effects of GDV. (5)
- venous stasis
- gastric wall necrosis
- mucosa death (full thickness necrosis possible)
- short gastric a. rupture
Describe the systemic effects of GDV. (5)
- reduced venous return- direct compression to caudal vena cava
- portal hypertension- direct compression of portal vein
- increased bacterial translocation
- decreased oxygenation- direct pressure on diaphragm
- poor coronary blood flow d/t lack of venous return- arrhythmias
What are clinical signs of GDV? (6)
- distended abdomen
- bradycardia +/- arrhythmia
- Reverse C or compartmentalized stomach on radiographs
What are pre-operative considerations for GDV? (6)
- stabilize patient first!
- fluids!!!! lots of them
- pass orogastric tube and try to decompress
- broad spectrum antibiotics
- correct acid-base and electrolytes abnormalities
- treat arrhythmias if present (IV lidocaine)
How do you achieve gastric decompression with GDV?
- orogastric intubation ideal
- if not, over the needle catheter or trocar- percutaneous, clipped and aseptically prepped
What are goals of GDV surgery?
- reposition stomach
- remove devitalized tissue
- gastropexy (permanent adhesion)
Describe how you reposition the stomach in GDV surgery.
pylorus should gently be retracted ventrally and to the right side, while simultaneously pushing body and fundus dorsally and left
What are the most common problem areas with regard to tissue viability with GDV?
- greater curvature
- fundus and body
What additional procedure is sometimes necessary with gastropexy with GDV? (2)
- resection of devitalized stomach
- splenectomy if evidence of vascular thrombosis or necrosis
permanent adhesion b/w pyloric antrum and right abdominal body wall
Describe incisional gatropexy.
- 4-5cm incision on gastric antrum through serosa, muscularis, and submcosa (NOT MUCOSA)
- 4-5cm incision through the peritoneum and transversus abdominis (2-3cm caudal to last rib)
- suture these together with 2 simple continuous lines with 2-0 PDS
Describe a belt-loop gastropexy.
- flap elevated from antrum, incorporating gastroepiploic artery
- passing through a tunnel in abdominal body wall
Describe the circumcostal gastropexy.
- flap similar to belt loop on greater curvature
- palpate 11th or 12th rib costocondral junction
- stay suture on flap to facilitate passage around rib
When can laparoscopy be used to pexy?
- prophylactic pexy only
- common with spay-pexy procedures
Describe post-op care after GDV repair.
- IV fluids, electrolytes
- usually liquids and soft foods in 12-24 hours
- if extensive gastrectomy, delay food intake for 35-48 hours (consider jejunostomy or TPN)
- gastric atony, vomiting, and peritonitis are most common complications