Chapter 92 Small Intestine Flashcards
where does the root of the mesentery attach?
Using same anatomic resference, at what level does cranial mesenteric artery originate?
Root of mesentery ventral to L2
Cranial mesenteric artery ventral to L1
Label the diagram:
Name two vessels that the cranial mesenteric artery anastomoses with
- Caudal pancreaticoduodenal artery (from cranial mesenteric a.) anastomoses with cranial pancreaticoduodenal atery (from celiac a.)
- Middle colic (from cranial mesenteric a.) anastomoses with left colic artery (from caudal mesenteric a.)
Label the diagram:
Where is the cranial mesenteric ganglion located?
On the sides of and caudal to cranial mesenteric artery
How much do the villi increase SI area in dogs?
And in cats?
Dogs x8 surface area
Cats x15 surface area
What are the two types of cell in Si mucosa?
- Epithelial cells
- Goblet cells
- (c.f. in colon 3rd cell type is enterochromaffin cell)
How long does it take for total villous epithelail replacement?
2-6 days
What are the Si lymphoid aggregates called
Peyer’s patches
What are the two types of motility in normal SI?
Define each
Segmentation: Random contraction of small area
Peristalsis: Organized wave of contraction
What 2 compounds are absorbed in the ilium?
- Cobalamin (B12)
- Bile salts
(Folate absorbed in jejunum)
How do enterocytes change as they migrate from base of crypt to tip of villus?
- At base they are dividing, undifferentiated epithelial cells, primarilty for fluid secretion
- Differentiate into immature enterocytes and function to digest and absorb
What proportion of ‘fluid presented’ does jejunum absorb?
And ilium
Jejunum 50%
Ileum 75%
What hormone is responsible for pancreatic digestive enzyme and bile secretion?
What hormone causes bicarb release (from pancreas)?
- Cholecystekinin (produced in duodenal mucosal cells) in response to nutrients
- Secretin
Name the enzyme(s) responsible for breakdown of the following:
Proteins
Carbs
Lipid
Proteins:
- Trypsin
- Chymotrypsin
- Carboxypeptidases
- Aminopeptidase
Carbs:
- Amylase (carbs –> oligosaccharides)
- Sucrase (sucrose –> glucose + fructose)
- Lactase (lactose –> glucose + galactose)
- Maltase (maltose –> glucose)
Lipid:
- Lipase
How do bile acids work to enhance lipid breakdown/absorbtion?
- Digestive enzymes not fat soluble.
- Bile acids have hydrophilic + hydrophobic parts. Hydrophobic parts embed in lipid –> lipid breakdown into smaller parts.
- Increase surface area of oil-water interface –> improved access for pancreatic lipase
How are absorbed fatty acids/glycerides packaged within enterocytes?
As chylomicrons
(then into lymph (not portal vein!) into cava)
What blood gas/electrolyes combo is usually seen with upper gi obstruction?
Hypochloraemic, hypokalaemic metabolic alkalosis
(V –> loss of gastric fluid i..e high concentration of HCl, K and Na in gastric fluid)
List 6 ways to assess intestinal viability
- Bleeding/vessel pulsation
- Colour
- Thickness
- Peristalsis
- Surface oximetry
- IV fluoroscein + UV light
What dose of fluoroscein is given to asses Si integrity?
What finding is consistent with non-viability?
10-15 ml/kg iv.
Use UV lamp. Areas of non-fluorescence >3mm (n.b. more liekly asesses mucosal integrity, not full thickness SI)
Why is two layer Si closure not recommended/
Results in avascular necrosis of inverted tissue –> prolonged lag phase of healing and increased intraluminal protrusion of tisue i.e more prone to obstruction
What 3 suture patterns are suitable for SI closure
Simple interrupted, simple continuous, modified Gambee
List 2 methods to re-inforce SI suture line
- Omental wrap (angiogenic, immunogenic and adhesive properties)
- Serosal patch
- (Gall bladder serosal patch reported experimentally)
What volume of saline is instilled to assess 10cm length of bowel?
Approx 15 ml
(slightly more with digital occlusion vs slightly less w Doyen occlusion)
List 5 techniques to deal with luminal disparity
- Side-to-side stapling (GIA)
- Slightly divergent sutures from smaller to larger lumen side
- Slanted cut along smaller side
- Spatulate
- Partially close larger lumen
list 4 stapling techniques for SI anastomisis
- Side to side GIA
- EEA stapler
- Triangulating (everting) end-to-end anastomisis using x3 TA30 staple cartriges
- Skin staples (place a stay at each 120º, tension between two stays while staples applied)
List 2 techniques to reduce risk of leakage from transverse (TA) staple line of anastomosis
- Offset longitudinal staple lines
- Oversew
What is closed height of 3.5mm staple (blue)?
And 4.8mm (green)?
- 5 mm –> 1.5 mm
- 8 mm –> 2 mm
(TAV3 = 2.5 mm –> 1 mm and three rather than two staple rows)
What surgical step is employed to prevent tension + separation of ‘inner corner’ of GIA staple line?
Crotch suture (ensure to engage submucosa)
Where do side-to-side stapled anastomoses leak from?
TA staple line!
(particularly where GIA and TA staples overlap)
How did anastomosis with skin staples compare with hand-sutures simple interrupted sutures?
- Same bursting strength
- Same lumen diameter
- Significantly faster
What is risk of 360º omental wrap?
Intestinal obstruction
What skin biopsy punch size for GI biopsies?
6mm
Why is enteroplication not typically recommended?
rate of complication due to enteroplication > rate of intussusception recurrence
List 5 potential complications of enteroplication
- Obstruction
- Ileus
- Strangulation
- Perforation
- Segmental volvulus
In what 4 instances can enteroplication be considered
- Recurrent intussusception
- Not possible to remedy underlying cause for intussusception
- Pre-disposing cause not identified
- Generalised hypermotility/enteritis
Where do recurrent intussusceptions usually occur?
Orad to previous intussusception
List 4 potential complications after SI surgery
- Septic peritionitis
- Adhesions
- Short bowel syndrome
- Ileus
What is dehisence rate of enterotomy/enterectomy?
And of biopsy?
<15%
11% for biopsy
List 5 factors that have been associated with higer risk of dehisence
- Pre-op septic peritonitis (40% vs 6%!)
- Hypoalbuminaemia
- Intra-op hypotension
- Use of blood products
- Delayed enteral nutrition
What is risk for breakdown with presence of pre-op septic peritonitis?
40%
What heamatology change can be seen with septic peritonitis?
Increased band neutrophils
List 3 techniques for post septic peritonitis abdo drainage
- Closed suction drain
- Open drain
- Vacuum assisted peritoneal drainage
List 4 benefits of vacuum assisted peritoneal drainage over open peritoneal drainage
- Quantification of fluid
- Lower risk of nosocomial infection and evisceration
- Reduced frequency of dressing changes
- Faster time to closure
What % BW fluid can the peritoneal membrane + omentum absorb?
3-5% bodyweight per hour!
List 4 factors known to encourage adhesion formation
List 3 techniques to minimise adhesion formation
Name a preventative measure
Factors leading to adhesion:
- Ischaemia
- Haemorrhage
- FB
- Infection
To minimise adhesion:
- Atraumatic tissue handling
- Moisten tissues
- Aseptic technique
Perioneal lavage with dialysis solution or tissue plasminogen activator reduced adhesions experimentally.
Is proximal or distal SI excision better tolerated?
Proximal better tolerated as preserves ileum.
Removal of ileum –> steatorrhea
What % bowel excision can –> short bowel syndrome.
50%
(but some dogs tolerate 85% resection without any need for special management so v variable)
List 4 pathophysiological effect that –> short bowel syndrome
- Reduced mucosal surface area
- Reduced intestinal transit time
- Bacterial overgrowth
- Gastric + intestinal hypersecretion
What are the 2 most consistent signs of short bowel syndrome?
Persistent diarrhoea
Weight loss
What are typical radiographic signs of intestinal obstruction?
- Multiple, gas-dilated loops
- Dual SI population
- Turgid, stacked loops
In patients with short bowel syndrome, how long did it take for orally administered contrast to reach colon
10 minutes
List 5 steps in medical management of short bowel syndrome
What surgical options have been reported in humans
- IV electrolye supplementation
- Small, frequent, highly digestible meals (monomeric containing soluble fibre + glutamine. Some fat to slow gastric emptying and –> enterocyte growth)
- Injectable fat soluble vitamins
- Anti-diarrhoea drugs if persistent diarrhoea (loperamide (=Imodium) 0.08 mg/kg tid)
- Abx if bacterial overgrowth
Surgical options reported (but high mornbidity! Not reported in small animals))
- Intestinal valve construction
- Reversed SI segment interposition
- Reversed colonic segment interposition
- Reversed electrical intestinal pacing
What is outcome in animals with short bowel syndrome
Dependent on a lot of individual patient factor factors, but 80% owners felt ‘good’ outcome
List 4 steps in managing post-op ileus
- Correct underlying disorders
- Early, frequent ambulation
- Early feeding
- Prokinetics
- Cisapride
- Metoclopramide
- Mirtazepine
- Erythromycin
- (reverse opioids if possible)
What dose of erythromycin is used to stimulate gastric emptying?
0.5 - 1.0 mg/kg po or iv tid
Similar effects to hormone motilin
What measurement is typically used to assess for Si dilation in dogs?
And cats?
What value is suggestive of obstruction?
Dogs: Intestinal diameter vs height of L5 body
Cats: Intestinal diameter vs height of cranial endplate of L2
Obstruction likely if ratio >2 in dogs, >3 in cats
What three values combined resulted in >95% sensitivity for presence of intestinal obstruction?
And what three values for >95% specificty?
N.B the sens values are wrong- should be LESS THAN
List 3 radiographic signs compatible with linear FB
- SI bunched in cranial-mid ventral bdomen
- Plication
- Gas in small eccentrically located bubbles
What is preferred modality for GI Fb detection
US
List an alternative methdon to multiple enterotomies for linear FB removal (described in cats only)
Single enterotomy catheter technique (tubing attaced to proximal linear FB via enterotomy then tubing milked distally)
(conservative management also reported in cats presented stable, successful in 50% but of others, 40% developed peritonitis - surgery recommended)
What is a management option if intestinal viability is equivocal
Repeat coeliotomy 24 hours later
What dimension of skin staples are used for enterotomy/enterectomy?
Regular size (4.8 x 3.4mm)
How does prognosis differ in dogs vs cats with linear FB
Prognosis better in cats
In dogs, 30% of dogs have septic peritonitis at surgery and >40% need R+A
What diagnosis is made if ileus is unreponsive to medical management and ex-lap negative (+ taken biopsies!)?
Intestinal pseudo-obstruction
What is the prognosis for intestinal pseudo-obstruction?
Grave
usually because of progressive emaciation
What is ideal diagnositc test for mesenteric infarction?
What is most commonly performed
Mesenteric angiography.
Sequential US over 48 hrs reveals dramatic changes suggestive of thrombus:
- Focal bowel dilation
- Initially normal bowel layering –> complete loss of normal layering within 24 hours
Which part is intussusceptum and which is intussuscipiens?
Intussusceptum = invaginated, inner portion
Intussuscipiens = outer portion
How does presentation of iliocolic intussusception differ from more proximal one.
Iliocolic intussusception more likely to present with tenesmus and haematochezia rather than vomiting
Aside from US name a method to diagnose iliocolic intussusception (not CT)
Barium enema
What is US appearance of intussusception?
- Concentric SI rings in transverse
- Parallel lines in longitudinal
What US finding is suggestive of an intussusception that is able to be reduced (and therefor ?at risk of spontaneous reduction?)
What additional step should be performed in these cases?
Absence fo vascular collapse in intussusceptum
Repeat US after GA, before sx (incase spontaneously reduced)
What is reported recurrence rate of intussusception
Within what timeframe does it usually occur?
5-25%
Usually within 3 days (up to 3 weeks)
What conditions has mesenteric volulus been associated with?
- EPI
- Enteritis
- Ileocolic carcinoma
- GI FB
- GI surgery
- Abdo trauma
- GDV
What are 2 most frequent presenting signs of mesenteric volvulus
- Haematochezia
- Abdominal distention
What features distinguish mesenteric volvulus from mechanical obstruction or GDV
- Uniform and extensive SI distension
- Normal position of stomach
List 2 surgical option sfor mesenteric volvulus
De-rotation
R+A without de-rotation (duodenoilial anastomosis reported)
What technique can be used to ‘close’ duodenal defects when R+A ideally avoided
Serosal patching
Vascularised jejunal patch graft also reported
How are feline alimentary lymphomas classified?
Large cell: intermediate/high grade, often focal lesion
Small cell: low grade, usually diffuse
List 4 non-neoplastic differential for Si mass
- Haematoma
- Granuloma
- Abcess
- Sclerosis (FGESF)
- (cyst)
- (intestinal (duodenal) duplication or diverticulum)
What paraneoplastic syndrome has been reported with canine and feline T-cell lymphoma?
Hypereosinophilia
What paraneoplastic syndrome has been reported with smooth muscle tumours
- Hypoglycaemia
- Nephrogenic diabetes insipidus
What are minimum recommeded margins for SI neoplasia?
3 cm
What is typical chemo protocol for feline large cell lymphoma?
And small cell?
Large cell = CHOP
Small cell = pred + chlorambucil
CHOP: Cyclophosphamide, Hydroxydaunomycin [doxorubicin], Oncovin [vincristine],and Prednisolone)
What is another name for c-kit.
In what tumours is c-kit expressed?
C-kit = CD 117
GIST
What is MST for small cell intestinal lymphoma?
And large cell
Small cell 2 years
Large cell 6 months
What % of FGESF cases had intralesional bacteria?
What is treatment
Bacteria in 70%
Tx = pred +- surgery
Name two congenital malformations of the SI
Name a life threatening presentation
Tx?
Intestinal duplication and diverticulum
Can present with profuse GI haemorrhage
Tx: R+A
