Principles of GI Surgery 1 + 2 Flashcards
For what 2 reasons would GI surgery be performed?
- DIsease of the wall of the GI tract
- Partial/complete obstruction of the GI tract
Of what clinical significance are the GI lesions wrt surgery?
Dependent on location may compromise fitness for aneasthesia
- Gastric disease may -> gastric vomiting
- SI complete obstruction may -> acute vomiting
- SI partial obstruction may -> chronic VD and weight loss
- GI bleeding may -> heamatemesis, meleana
How may gastric disease and vomiting comproise the animal pre-surgery?
- Loss of HCl -> metabolic alkalosis and hypochlorinaemia
- Dehydration -> poor perfusion and metabolic acidoisis
- insufficient food intake -> hypokalaemia
How may complications from gastric vomiting be corrected prior to surgery?
IV isotonic crystalloids, IV K+ supplement (sometimes)
How may SI complete obstruction and vomiting compromise the animal pre-surgery? What is this dependent on?
Dependent on location of obstruction
- high = mimics gastric vomiting
- low = loss of pancreatic Na+, HCO3- -> metabolic acidosis and hyponatraemia
> dehydration -> poor perfusion and metabolic acidosis
> Insufficient food intake and absorption -> hypokalaemia
How may complications from complete SI blockage be corrected prior to surgery?
IV isotonic crystalloids, IV K+ supplements
How may SI partial obstruction (VD and weightloss) compromise an animal pre-surgery?
- Vomiting -> electrolyte loss and dehydration
- Bacterial proliferation and nutrient metabolism -> malassimilation and mucosal damage -> diarrhoea, weight loss, hypoalbumenaemia
How may complications from partial SI blockage be corrected prior to surgery?
IV isotonic crystalloids, IV K+ supplementation, hypoalbumenaemia cannot be corrected but normotensive state should be maintained
How may GI bleeding (-> heamatemesis and meleana) compromise an animal prior to surgery?
-> anaemia and hypoalbumenaemia
How may GI bleeding be corrected prior to surgery?
Blood transfusion, Fe supplements
What should especially be noted on the physical exam prior to anaesthesia and surgery?
Dehydration status - if in doubt, IV fluid therapy!
What should be checked to determine that the animal is fit enough for surgery?
- complete history
- physcial exam
- heamatocrit and TP
- electrolytes esp K+ Na+
- acid base status
- complete biochem/heamatology IF CLINICALLY INDICATED ONLY
How does the distribution of GI bacteria differ along the GI tract?
- V in stomach (acid kills majority of bacteria)
- SI: 10^2 - 10^6 CFU/ml, 50% anaerobes
- Colon: 10^9 - 10^11 CFU/ml, 80% anaerobes
Which organism is responsible for the majority of post-surgical infection? What type of organism is this?
E coli - Gram -ve rod
For what reasons are use of prophylactic antibiotics encouraged for GI surgery?
- immune defences may be compromised (debilitated animals eg. VD+, GI injury, extensive resections, >90min surgeries)
- septic peritonitis fatal in 50% cases
> indicated for use in ALL SI and Colon surgeries
For what reasons may prophylactic antibiotics be discouraged?
- animals have an immune system
- although contamination is inevitable, will not definitely progress to an infection
- antibiotics may NOT v risk of infection
> not indicated for use in stomach surgery if no prior pathology is present (eg. FB removal)
What classes of antibiotics would be indicated for use in gastric surgery (IF indicated)? eg.?
Single broad spec with anaerobic coverage
eg. 2nd generation cephalosporin OR amoxycillin clavulanate
What classes of antibiotics would be indicated for use in SI surgery (IF indicated)? eg.?
Single broad spec with anaerobic coverage
eg. 2nd generation cephalosporin OR amoxycillin clavulanate
What classes of antibiotics would be indicated for use in colon surgery (IF indicated)? eg.?
Combination of 2 antibiotics, including an anaerobe specific drug
eg. Metronidazole PLUS 2nd gen cephalosporin or amoxycillin clavulanate
Other than ABs, how may bacterial contamination be minimised (5 ways)?
- Isolate site of GI entry
- Use separate instruments for contaminate surgery
- Lavage abdomen with sterile saline (dilutes conc of bacteria)
- Change gloves
- Lavage wound after closure
How may the colon be prepared for surgery? How does this differ to human medicine?
- Humans routinely enema-ed prior to surgery
- No evidence to support this in vet (liquid ^ likelihood of leaking through incision site)
- Low residue diet and 12-24hr starvation recommended only
Outline the layers of the intestinal wall. Which is strongest and why?
Adluminal: Mucosa - submucosa - muscularis (circular) - muscularis (longitudinal) - serosa(sub) - serosa :Outside edge
> Submucosa strongest due to collagen so MUST BE SUTURED
What stages of wound healing are solely active during days 1-3? How long do these continue?
Heamostasis (formation of platelet-fibrin clot) and inflammation (microbial killing and wound debridement)
- will continue until day 5
What stage of wound healing begins on day 3?
Proliferation of granulation tissue (fibroblast^, collagen synthesis, angiogenesis -> ^ wound strength)
At what stage post-surgery is the “danger zone” for wound failure? Why?
Day 3-5
> overlap of inflammatory and granulation processes
How does the rate of wound healing differ along the GI tract?
> Stomach - rapid healing due to ^ blood supply, rarely complicated
SI - by day 14, regained 75-80% normal tensile strength
LI - by day 14, regained 50% normal tensile strength (Poss ^ collagenase production? risk of wound breakdown greatest)
Is colonic surgery often indicated?
NO! Only perform colonic surgery if there is a definite indication to do so.. even biopsies should be avoided if possible
What surgical factors impact -vely on wound healing? How may these be overcome?
Compromise to blood supply and traumatic surgical technique (avoid electrocautery, use atraumatic debakey forceps, atraumatic bowel clamps and stay sutures in lieu of handling stomach/intestines)
Which commonly used instrument should NOT be used in GI surgery?
Rat-tooth forceps
What physiological factors impact -vely on wound healing? How may these be overcome?
> Hypoproteinaemia (rarely correctable prior to surgery)
Chemotherapy and radiotherapy (delay for 3 weeks post surgery)
Steroids (discontinue use if possible)
What type of suture should be used to repair gut lining and why?
Full thickness appositional to allow separate layers to repair individually
Which suture patterns may be used in the SI?
Simple interrupted or simple continuous
Which type of suture material should be used for GI surgery? eg.?
Monofilament as is resistant to infection (cf. multifilament)
Material that maintains strength long enough to permit healing (>5d) but is absorbable
eg.PDS II (or Monocryl though this is too weak really, loses strength ~7 days)
What are staples made from?
Titanium - inert and unreactive so can be left in the abdomen
How does the reconstruction of gut wall with staples differ from sutures? Are staples advocated?
Appositional not possible - lining must be everted or inverted.
> may be less likely to break down/burst cf. suturing, so is advocated
When is ex lap indicated?
- to diagnose the cause of intra-abdominal disease if all other diagnostics have been unsuccesful
- to correct the cause of intra-abdominal disease
> eg. to remove FB, investigate chronic vomiting, liver biopsy
If no discrete lesion is found on ex lap what next steps should be taken?
BIOPSY - stomach - SI - +- liver - +- pancreas -+- LNs >NB: NOT colon unless indicated
Where should the incision for an ex lap be made? What may get in the way and how should this be dealt with?
- From xiphersternum to pubis midline (linea alba, should not cut abdo muscles)
- Preputial muscle will be on the midline in males - cut this and stitch at end of surgery - No problem!
What 2 types of retractors can be used for GI surgery?
Balfour - have an extra scoop for diaphragm and bowed side arms
Gossett - straight side arms
What should be the first step in an ex lap?
- Protect wall from drying with moist swabs
- Palpate entire GI tract - run through hands in a logical manner
What is an incision into the stomach referred to as? Where should this ideally be made?
Gastrotomy - on side between lesser and greater curvature, away from blood supply etc.!
How should the stomach be repaired following a gastrotomy?
2 layers
- first mucosa and submucosa (simple continuous suture; appositional)
- then serosa and muscularis (simple continous suture, appositional or inverting lembert)
Outline 4 steps of SI biopsy
- isolate intestine
- milk contents away and close intestine with atraumatic clamps/fingers
- incise ANTImesenteric border
- Ellipse shaped biopsy - cut with metzenbaum scissors
- Trim excess mucosa to ensure sutures placed through SUBmucosa.
- Suture 3-5mm apart, 3-5mm from cut edge
How does the blood supply to the SI and LI differ?
SI: radiating supply from root of mesentry
LI: parallel supply
How may SI and LI be differentiated grossly?
LI paler, longitudinal striations, blood supply
Which side of the liver does the caudal vena cava pass?
Right
How should the liver be manipulated?
Carefully - very friable and easily damaged
Use palms of hands
When would liver biopsy be indicated?
Clinical signs and bloods indicative of liver disease
Generalised abdo appearance - ultrasound or surgery
Presence of liver nodules/masses
What alternative procedure to an open biopsy of the liver should be considered?
FNA (fine needle aspirate) or Trucut biopsy under ultrasound guidance
What are the clamps that are used to crush tissue and initiate haemostasis referred to as?
Heamostats
When would a peripheral biopsy of any liver lobe be indicated?
Generalised liver disease
When may skin punch biospy tools be used for liver biopsy?
Specific nodule or local disease process (skin biopsy good as prevents going too deep)
What may be used to encourage heamostasis other than clamps?
Collagen sponges initiate platelet clotting
Where can gastric resections be performed?
Fundic region - cardia cannot be detroyed neither can pylorus - biliary and pancreatic ducts would have to be rerouted.
What does the pancreas share its blood supply with?
Descending duodenum
How are pancreatic biopsies performed?
Tie ligature round section before cutting
Do not remove form near pancreatic ducts
Where does the left limb of the pancreas lie?
Stomach wall
What history and clinical signs are associated with gastric FBs?
- Young
- Previous FB ingestion
- Vomiting -> dehydration
- Lethary
- Abdo pain and gastric distension
- Depression
- Anorexia (sometimes)
- Mealeana or heamatemesis
- Dyspnoea if 2ndry aspiration pnumonia
How may gastric FBs be treated?
Endoscopic removal or gastrotomy
What postop care is required following gastrotomy? What is the prognosis?
Feed straight away, antacids if ulcers present and gastric protectants anyway
Prog: excellent
When investigating gastric neoplasia, what other diagnostics should be investigated first?
- Radiograph esp thorax to check for metastases
- Position of gastric neoplasia: a large part of the stomach can be resected (fundic region) BUT cardia must be preserved and common bile and pancreatic duct must be preserved or rerouted.
What treatment is required if the pancreas is removed?
Pancreatic supplements for life
Give two types of gastric neoplasia
Leiomyoma (benign smooth muscle/connective tissue tumour)
Adenocarcinoma (Malignant)
What is the prognosis for gastric neoplasia?
Complete resection of benign leiomyoma : good
Adenocarcinoma: poor, clinical signs often recurring after weeks
What closure method is recommended for partial gastrectomy?
Staples (staple gun with inbuilt knife secures in 6 places, eversion of tissue)
When is intestinal resection and anastomosis indicated?
> Ischeamic necrosis - ^ intralumenal pressure - disrupted blood supply Would -> breakdown of gut, spillage of contents -> peritoneal cavity -> septic peritonitis > Neoplasia
How can you distinguish viable intestine form necrotic?
- pulse in arterial blood vessels
- peristalsis
- normal colour
- normal wall thickness
How do you carry out an intestinal resection?
- Milk out intestinal contents
- isolate intestine with atraumatic clamps
- Ligate mesenteric vessels
- Incise mesentry
- Incise intestine close to clamps
Why may ligating blood vessels be difficult?
Hidden by fat
How may luminal disparity following resection and anastamosis be overcome? How should the two section be rejoined?
- Space sutures further apart on large side (leaky)
- Transect small side at an angle to match diameter of large side
- Reduce small side with sutures (leaky)
- Spatulate small side (advocated)
> suture mesenteric border first
> 2nd in anti-mesenteric border
> repair mesentry to prevent further strangulation of intestine
How may GIT wound healing be improved?
- Omentalisation: Wrap omentum round incision site.
- Serosal patch: Tack healthy intestine over wound (only advocated when wound has failed and is being sutured for the second time
What history and clinical signs would be associated with intestinal FBs?
History: Persistent vomiting, frequently projectile - anorexia - depression - no defeacation Exam: dehydration - abdo pain - intrabdominal mass - string etc. stuck in mouth esp cats
When performing an enterotomy where should the incision be made?
As close to healthy tissue as possible.
How may intestinal string FB be diagnosed and treated?
Radiograph: intestines “stacked”
Tx: multiple enterotomies, cut string and remove in sections
What types of intestinal neoplasia are possible?
> Adenoma/adenocarcinoma (->local LN and liver) 12m
Lymphoma (esp cats)
Leiomyoma/leiomyosarcoma (->local LN and liver) 20-21m
Mast cell
Duodenal polyps
Which breed are predisposed to intestinal adenocarcinom? What is the median survival time?
Siamese
- 12m
What margin should be left when removing a growth?
3cm
How may intestinal neoplasia be noted in the history/clinical signs?
Partial obstruction while growing
-> chronic intermittent VD+, weight loss
> radiograph:
-dilated intestine and ingesta backed up behind obstruction
-“gravel sign” where mineralised fragments and large food pieces are stuck behind the obstruction
> ultrasound shows loss of 5 layers of normal intestine wall
Give 4 common causes of intessuception
Intestinal growth, parasites, bacteria, IBD
What are the two portions of intestine either side of an intussuception referred to as?
Intussusceptum invaginates into Intussescipiens
Which blood flow is affected first by gut problems?
Venous, then arterial
How may intussesceptions be diagnosed?
- dehydration, depression abdominal pain, palpable tubular mass
- potential protrusion form the anus (distinguish from anal prolapse by passing thermometer to the side of the protrusion)
- Ultrasound: parallel lines or concentric rings - double thickness (ie. 10 rings instead of 5)
What are the 3 surgical treatments for intussception? What is the prognosis?
Reduction: push rather than pull
Resection: if irreducible, ischeamic, or if a mass is present
Enteroplication: suture all intestine to each other! - treat underlying disease as well (check feacal bacteria and parasites, deworm if in doubt) [minimal evidence base, causes cramps and VD in humans, still performed]
Prognosis: good in young, 6-27% recurrence between 3 days - 3 weeks
How soon after surgery should enterotomy/enterectomy patients be given food?
Straight away ASAP
What are potential complications of enterotomy and enterectomy?
- persistent ileus (VD, pain, diarrhoea, abdo distension)
- Stricture at anastomosis site (presents as partial obstruction)
- Short-bowel syndrome if >70% resected -> Malassimilation
- Intestinal incision dehiscence (7-16% cases for biopsy)
How does septic peritonitis occour?
Bacteria and inflamatory cells enter peritoneal cavity-> cytokines, endotoxin release - vaodilation, ^ capillary permeability, diaphragmatic lymphatics bloacked with fibrin - ^fluid and protein in peritoneal cavity - Hypovoleamia and decreased vascular oncotic pressure-> hypovoleamic shock = Systemic Inflammatory Response Syndrome - DIC - Death
What is the prognosis for septic peritonitis?
50% mortality
What are the clinical signs for septic peritonitis?
- VD+
- anorexia and depression
- abdo pain and enlargement
- hypovolaemic shock (^HR, vBP)
- pyrexia
- discharge from abdo wound
- Heamatohezia, meleana, haematemesis
How is septic peritonitis treated?
Surgery
How is septic peritonitis diagnosed?
Abdominocentesis - look for neutrophils containing bacteria
