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CB - Soft Tissue - Digestive System > 92 - Small Intestine > Flashcards

92 - Small Intestine Flashcards

1
Q

How long is the small intestine?

A

5 x the length of the trunk

Dogs = 2-5m
Cats = 1-1.5m

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2
Q

What does the root of the mesentry contain?

Where is it located?

A

Cranial mesenteric artery
Cranial mesenteric plexus
Lymphatics

Located at level of L2

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3
Q

Describe the arterial blood supply to the small intestine

A

Cranial mesenteric artery
- 2cm from branches => Common trunk => middle and right colic and iliocolic vessels (Caudal mesenteric anastomoses with middle colic via the left colic a.)
- Second branch => Caudal pancreaticoduodenal a. which anastomoses with crainal pancreaticoduodenal from hepatic/gastroduodenal branches of the celiac=> Supply duodenum and pancreas (obvs)
- Reduces in size as brances into 12-15 jejunal branches which anastomose with each other => Supply jejunum with short vasa recta penetrating the intestinal wall.
- Terminus of the cranial mesenteric => Ileal branches => Supply ileum

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4
Q

Venous drainage of the small intestine

A

Caudal mesenteric vein => Portal vein

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5
Q

Innervation of the small intestine?

A

Celiac and cranial mesenteric ganglions

Vagus and Splanchinic nerves

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6
Q

Which lymph nodes does each section of the small intestine drain to?

A

Duodenum = Hepatic LN
Jejunum = Mesenteric LN
Ileum = Colic LN

Lacteals course through the mesentery and lymphoid follicles are present in ~22 Payers patches in the intestine

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7
Q

How much do villi increase the surface area of the intestines in dogs and cats?

A

Dogs = 8 x

Cats = 15 x

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8
Q

What is the rate of villous turnover in the instestine?

A

2-6 days

Epithelium produced in the intestinal crypts, pass up to the villi and shed from apex

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9
Q

What are the two cell types in the villi? & What are their functions?

A

Columnar cells = Absorption
Goblet cells = Secrete mucus

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10
Q

What are the two types of contraction in normal gut motility?

A

Segmental =
- Stimulated by local stretch reflexes and vagus nerve
- Random contraction of small areas
- Slows down forward motion and mixes ingesta
- More effective digestion/absorption

Peristaltic =
- Simulated by local and vagally mesiated reflexes via submucosal and myenteric plexus
- Organised wave propelling food aborally
- 5-15 minutes of rapid contractions from stomach through small intestine. Followed by 60 minute quiesence period with rare contractions
- Cycle every 1.5-2 hours

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11
Q

What happens if segmental or peristaltic contractions are reduced

A

Segmental = Diarrhoea

Peristaltic = Ileus

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12
Q

Briefly describe the processes in intestinal absorption

A

Passive = Via a concentration gradient
- Na & Cl via electrochemical gradient
- Na contransport wiht other molecules
- H2O follows solultes (Jejunum absorbs 50% of its contents and ileum absorbs 75% of its contents)
- Faciliatated diffusion via carrier protein channels for more specific molecules

Active = Via Na:K ATPase pump, requires ATP
- Amino acids
- Monosaccharides

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13
Q

Where are digestive enzymes released from?

What causes this?

A

Enzymes from the pancreas and brush border of the small intestine

Released triggered by cholecystokinin

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14
Q

What prevents the passage of harmful acids from the stomach into the small intestine

A

Secretin

Triggers release of bicarbonate from pancreas to the small intestine to neutralise acids

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15
Q

How are proteins digested and absorbed into the blood stream?

A
  • Proteolytic enzymes (Trypsin, Chymotropsin) cleave proteins to smaller peptides
  • Carboxypeptidase from brush border cleaves one amino acid at a time whilie aminopeptidase and dipeptiase free the end amino acid products
  • Sodium dependent amino acid transporters on enterocytes dump these free amino acids into cells
  • Transportors on the basement membrane of enterocytes export amino acids from cell to blood stream

absorbed by villi

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16
Q

How are carbohydrates digested?

A

Pancreatic amylase breaks down carbs into oligosaccharides

These oligosaccharides are hydrolysed by the brush border enzymes into…

Amylase => Sucrose => Frutose
Lactase => Lactose => Gluocse and galactose
Maltase => Maltose => Glucose

Glucose & Galactose taken up by Na membrane co-transporter SGLUT1
Fructose => Faciliated diffusion through GLUT 2

Absorbed by villi

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17
Q

How are lipids digested

A
  • Pancreatic lipase breaks down triglycerides to free fatty accids and monoglycerides
  • Bile acids required as digestive enzymes are not fat soluble
  • Hydrophobic portions of bile acids intercalate into the lipid and hydrophilic remains on the surface => break down into smaller droplets => Increases surface area of oil-water interface which aids access by lipase
  • Free fatty acids are absorbed in micelles by passive diffusion.
  • Lipids packed into chylomicrons within enterocytes => Exocytosis and transported to lacteals => Lymphatic system => Blood

Absorbed by lacteals

18
Q

Review summary of digestion

A
19
Q

What are the consequences of fluid sequestration within the gut due to intestinal obstruction?

A

Dehydration
Hypovolaemic shock
Hypokalaemia
Hyponatraemia
Hypochloraemia
(Also losses from vomiting = K/Na/HCl)

HYPOKALEMIC, HYPOCHLORAEMIC, METABOLIC ACIDOSIS

20
Q

Give two options for minimally invasive intestinal surgery

A

Lap assisted (Modiffied Hassan technique or SILS port)

Wound retractor device (Alexis)

EXTRACORPOREAL SURGERY - Challenging due for proximal duodenum/duodenal flexure due to fixed mesentery

21
Q

Give two options for assessing intestinal viability

Persitalsis, colour, pulse, thickness etc)

A

Fluoroscein
- 10-15mg/kg IV
- (400mg/kg toxic dose)
- Woodslamp in dark room
- If > 3mm patches, resect

Surface oximetry
- Pulse ox probe
- Can miss pathces of ischemia

22
Q

What is the lag phase of intestinal healing?

A

Bowel wall collagenase activity
Resulting in reduction in collagen around sutures and decreased wound strength

Prolonged by inflammaiton

23
Q

Why is single layer appositional recommended for intestinal closure

A

Submucosal apposition is better in single layer

Double layer may increase avascular necrosis, inflammation and lag phase

Inversion reduces luminal diameter

24
Q

What is a Modified Gambee approximating suture pattern?

A

Minimises eversion by avoiding full thickness bites of the mucosal layer

25
Q

Give 6 points about the perfect intestinal suture…

A

3-5 mm from edge
3-5 mm apart
Full thickness
Extraluminal knot
Knot tying force 1.5 N
Surgeons or square knot

Simple interrupted, simple continuous or modified gambee

26
Q

Describe the perfect leak test

A

Should recreate physiologic peristaltic pressure

10cm section of bowel isolated
Doyens = 12-15 ml
Digital = 16-19 ml

27
Q

Name 3 methods of reinforcing the intestines after surgery

A

Omentalisation
Serosal patching
Gall bladder serosal patch

Cystic duct ligated, cystic artery preserved, gall bladder fundus incised, peritoneal surface of GB applied over incision and sutured with 3/0 Monofilament

(Another option = Matty S’ Transverse abdominis flap)

28
Q

What is the reported intestinal dehiscence rate
(According to Tobias)

Is dehiscence more common in dogs or cats?

A

7-16%
(11% after biopsy)

Dogs > Cats

29
Q

Name 6 risk factors for intestinal dehiscence leading to septic peritonitis

A

Hypoalbuminaemia
Hypotension
Use of blood products
Longer length resected
Delayed enteral feeding
Preoperative peritonitis

30
Q

For how long after surgery can intra and extracellular bacteria be seen on cytology from closed drains in non-septic dogs?

A

Up to 1 week

(Degenerative neuts normal for 3-4 days)

31
Q

What is the survival rate for dogs with septic peritonitis secondary to GI dehiscence?

A

73-85%

(Better Cf 50% mortality for septic peritonitis)

32
Q

What can reduce the rate of adhesion formation postoperatively following abdominal surgery?

A
  • Peritoneal irrigation with dialysis lavage
  • Recominant tissue plasminogen activator

Irrigation with saline prior to closure does not reduce adhesions

33
Q

What is the main concern regarding ileus postoperatively

A

Bacterial translocation

(Also regurgitation and aspiration)

34
Q

How can postoperative ilius be treated?

A

Screen for underlying cause

Treat electrolyte disturbances (Potassium and Magnesium)

Antagonise opioids (Naloxine)

Prokinetics
- Metoclopramide
- Mirtazepine
- Cisapride
- Erythromycin (0.5-1mg/kg)

35
Q

How does metoclopramide work as a prokinetic

A
  • Increases duodenal and jejunal peristalsis
  • Increases the tone and amplitude of gastric contraction
  • Reduces pyloric sphincter tone to increase gastric emptying
36
Q

How much of the small intestine needs to be resected for signs of short bowel sydrome to occur in dogs?

Resection of which region of the SI is tolerated best?

A

> 50%

(Some dogs tolerate up to 85% without signs!)

Proximal resection better tolerated than distal

37
Q

Pathophysiology of short bowel sydrome?

What are the clinical signs of short bowel sydrome?

A

Reduced mucosa surface area =>
* Hypersecretion
* Bacterial overgrowth
* Reduce gut transit time

Results in malabsorption and malnutrition

  • Weight loss
  • Hypocholesterolaemia
  • Hypoalbuminaemia
  • Steatorrhea (loss of ileum)
38
Q

Medical management of short bowel syndrome?

A
  • TPN until tolerates feeding
  • 6-8 meals per day
  • Liquid Monomeric diet
  • Soluble fibre and glutamine
  • 10-15% fibre (stimulates adaptive changes)
  • Fat included (reduces GI emptying, calorific and nutrtion for villi)
  • Loperamide (anti-diarrhoeal)
  • Antibiotics (Treat bacterial overgrowth)
39
Q

Surgical treatment options for short bowel syndrome?

A
  • Interposition of reversed GI segment
  • Colonic interposition
  • Reversed electrical pacing
  • Construction of intestinal valves
40
Q
A

CB - Soft Tissue - Digestive System (6 decks)

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