Intestinal failure

Section: Small bowel Curriculum: Curriculum, page 61

Definition

• A reduction of gut function below the minimum necessary for absorption of macronutrients or fluid and electrolytes so intravenous administration is necessary to maintain function and growth
• Short-bowel syndrome
  • Total small bowel length that is inadequate to support nutritional requirements on a standard conventional diet
  • For adults, an anatomic definition of ЅΒS is residual small bowel length <200 cm, measured from the duodenojejunal flexure, with or without colon. For ϲhildrеո (<18 years), the corresponding definition is small intestinal length <25 percent

Classifications

• Functional classification
  • Type 1
    • Acute short term intestinal failure which is self limiting i.e. post-operative ileus.
  • Type 2
    • Prolonged intestinal failure, life-sustaining parenteral nutrition is needed for longer than 20 days i.e. mesenteric ischaemia, abdominal trauma.
  • Type 3
    • Long-term intestinal failure in patients who are metabolically stable.
    • Usually stable people who are able to be managed at home with home-based parenteral nutrition i.e. Crohn’s disease, chronic intestinal pseudo-obstructions.
• ESPEN classification
  • Loss of intestinal length – short bowel syndrome
  • Loss of intestinal functional length – fistula
  • Loss of intestinal function – intestinal dysmotility
  • Loss of intestinal absorptive capacity – extensive small bowel mucosal disease
  • Intestinal obstruction - mechanical obstruction.

Aetiology

• 75% due to resection
  • Inflammatory
    • 25% - Multiple sequential resections – usually Crohn’s
  • Iatrogenic
  • Vascular
  • Ischaemia
  • Internal Hernia
    • Mid-gut Volvulus, SMA Occlusion
  • Traumatic injury to SMA
• Neonatal short bowel is usually due to necrotizing enterocolitis

Intestinal dysmotility

• Most common cause is a post-operative ileus.
• Other causes include Parkinson’s disease, chronic pseudo-obstruction, Chagas disease, medication associated endocrine disorders (hypothyroidism), systemic sclerosis.
• Mechanism is that patients reduce there oral intake due to feeding related symptoms or due to episodes of non-mechanical obstruction.
• Can lead to bacterial overgrowth
• Vomiting, diarrhoea, and intestinal secretion contributes to increased fluid and electrolyte losses.

Mechanical obstruction

• Bowel obstruction restricts oral intake.
• Also get increased intestinal secretion of fluid and electrolytes in the obstructed segments.
• Causes
  • Intra-luminal – polypoid tumours, intussusception, gallstone ileus
  • Intra-mural – strictures (could be neoplastic, inflammatory, fibrotic)
  • Extra-mural – neoplastic, hernias, volvulus, band adhesions.

Extensive small bowel mucosal disease

• Any condition which reduces the function of enterocytes which reduces the absorptive ability.
• Vomiting, diarrhoea, and restricted oral intake also contributes to intestinal failure.
• Causes include Crohn’s, scleroderma, Radiation enteritis, coeliac disease, food allergies, intestinal epithelial dysplasia, chemotherapy related enteritis

Length

• Colon/ICV preserved
  • Can resect up to 70% of the small bowel if ICV and terminal ileum retained
  • If patients have 200cm of jejunum and an intact colon, then they should be able to tolerate enteral feeds without TPN supplementation
  • Healthy patients with healthy bowel may tolerate down to 100cm with intact ICV and colon however unlikely to tolerate less than 150cm without ICV
    • Ileum has better adaptive ability then jejunum
    • Proximal resection is tolerated better than distal
    • TI also important for B12 absorption and Bile Salt recirculation
• Ileum
  • Resection > 60 cm of ileum is associated with malabsorption of vitamin B12
  • Resection > 100 cm of ileum is associated with insufficient bile salt concentrations in the duodenum for optimal fat absorption
    • Leading to fat and fat soluble vitamin malabsorption
• ICV valve
  • Loss of the ICV reduces small intestinal transit time, which may impair nutrient absorption
  • Ileocecal valve serves as a barrier to the translocation of colonic bacteria into TI
    • Bacterial overgrowth following ICV resection may be associated with malabsorption of fats, B12 and bile salts
• What lengths do you need?
  • Adults with residual small intestine of less than 180 cm are at risk for developing ЅΒS
  • Half colon is equivalent to 50cm
    • End jejunostomy – long term IF most likely if <180cm of small bowel.
    • Jejunocolic anastomosis – long term IF likely if < 130cm of small bowel.
    • Jejuno-ileal anastomosis – long term IF likely if <80cm of small bowel.
• In the short term – if you leave less than 180cm of small bowel then you will get at least short term intestinal failure.

Pathology

• Adaptive hyperplasia has a remarkable ability to compensate for significant resections however will be overwhelmed after a certain point
• Intestinal fistula
  • Large area of absorptive capacity is being bypassed.
  • Large losses of fluids and electrolytes
  • Disruption of the bile salt entero-hepatic cycle
  • Restriction of oral nutrition in order to reduce fistula output.
  • Increased metabolic demands due to sepsis associated with the fistula.

Absorption

• Small bowel absorption
  • Duodenum
    • Minerals - calcium, Iron absorption
  • Jejunum
    • Primary site for most macro and micro nutrients
    • Amino acids, monosaccharides, fatty acids, fat soluble vitamin (ADEK), water soluble vitamins, Zinc
  • Ileum
    • Bile salts
    • Vitamin B 12, water soluble vitamins, Zinc
    • Notes
      • The ileum has better absorptive ability and adaptation than the jejunum
      • If you lose the distal 60cm then you will get B12 deficiency
      • If you lose all the ileum you will lose the ability to absorb bile acids which will lead to bile acid malabsorption
  • Colon
    • Primarily sodium, water and potassium.
    • Can also absorb digested carbohydrates and short chain fatty acids.
    • Notes
      • The whole colon is equivalent to an extra 150cm of small intestine (which is lots!!)
      • For patients with short gut but an intact colon, you would put them on a high carbohydrate diet (as the colon can absorb this).
      • The colon is also really efficient at absorbing fluid – can absorb up to 6L of intestinal fluid per day – thus it is really important to restore continuity.

Bile acid malabsorption

• Resection of >100 cm of terminal ileum leads to disruption of the enterohepatic circulation
• Eventually resulting in bile acid deficiency
  • because bile acid losses exceed the compensatory increase in hepatic bile acid production
• Causes
  • Malabsorption
    • Fat
    • Fat soluble vitamin
  • Secreto-motor diarrhoea (the colon doesn’t like being exposed to bile acids)
  • Kidney stones (increased oxalate absorption)

Stages

• 3 stages of intestinal failure
  • Phase 1 – acute intestinal failure/hypersecretory phase.
  • Phase 2 – adaptation phase
  • Phase 3 – chronic failure/stabilization phase

Phase 1 – acute intestinal failure phase

• Occurs in the first 4 weeks post-operatively
• Patients loose large volumes of fluid, electrolytes, and have significant malabsorption.
• Up to 7L per day is secreted by the pancreas, liver, stomach and SI – this is normally all re-absorbed so in this phase there will be large intestinal loses.

Initial management

• Resuscitation and IV correction of fluids and electrolytes
• Identify reversible factors – intra-abdominal sepsis, anastomotic leak.
• Sepsis needs to be source controlled – either re-operation or percutaneous drainage and IVAbx.
• Patients should be put on acid suppression with a PPI to treat there hypergastrinemia and excess acid secretion – this lowers the small bowel pH and reduces the efficacy of digestive enzymes.
• Patients should have there nutrition optimised.
• May need TPN
• Enteral feeding should be started early to maximise the guts ability to adapt
• Anatomy should be defined – length and integrity
• Rule out a reason why a fistula won’t heal – i.e. obstruction, malignancy.
• Wound care and fistula care needs to be addressed.

Stage 2 – adaptation phase

• 1-24 Months

What is adaptation?

• Is a combination of both functional and structural changes
• Combination of both macroscopic and microscopic changes.
• More adaptation occurs in the ileum than jejunum.
• The bowel dilates and elongates
• Gastro-intestinal transit slow down.
• Villi get longer to increase the absorptive area.
• Epithelial hyperplasia occurs – increasing the number of enterocytes.
• Upregulation of the brush-border membrane permeability and transporters occur.
• Early intestinal feeding increases the rate at which adaptation occurs.

Management principles in stage 2

• Establish oral feeding in a stepwise manner over weeks to months
• Type of diet will depend on the presence or absence of a colon
• Colon present
  • Higher carbohydrate diet
  • Moderate restriction in fat consumption
  • Restrictive oxalate diet
    • Malabsorbed fat binds to calcium increasing colonic oxalate absorption which increases the risk of neprolithiasis
  • Oral rehydration solutions can be used.
    • Hypotonic solutions can be given. Avoid hypertonic solutions (i.e. fruit juice) as this will cause diarrhoea.
    • Isotonic solution may be helpful
  • Soluble fiber supplements can be useful – this decreases fluid losses, and slows gastric emptying.
• If the colon is not present
  • More even balance between carbohydrates and fats.
  • Should avoid both hypo and hypertonic solutions.
    • Should use Saint Marks Solution (is an isotonic solution).
      • Hypertonic - induce secretion to dilute → diarrhoea
      • Hypotonic - lack sugar required to be absorbed → diarrhoea
• Drugs should be introduced to increase with GI intestinal absorptive capacity.

Drugs

• PPI
  • Should be continued for 6 months then stopped to avoid SB bacterial overgrowth.
• Loperamide
  • Can use very high doses i.e. 48mg per day
• Codiene
  • Can also be used – 60mg per day.
• Octreotide
  • Can be trialled – is expensive, patients can get tachyphylaxis, it can cause gallstones. If not improving after 2 weeks should be stopped.
• Antibiotics
  • Can be used to Small intestinal bacterial overgrowth
• GLP2 analogue – Teduglutide – SC injection
  • Is a growth hormone which encourages GI tract adaptation.
• Cholestyramine and Colestipol
  • May help reduce diarrhoea by binding to bile acids and making them insoluble so they are not stimulating colonocytes to secrete chloride/fluid into the colon
  • Not useful for patients who do not have a colon
  • May make steatorrhea worse (as binding bile salts)

Monitor vitmains and mineral

Phase 3 – chronic failure/stabilization phase

Stabilisation phase/Chronic intestinal failure.

• Maximal adaptation of the GI tract can take up to 2 years.
• After that time – you need to figure out how you can get that patient living as normal a lifestyle as possible at home.

Irreversible chronic intestinal failure

• Survival rate is 65% at 5 years.
• Long term complications include catheter associated infections, loss of venous access, and development of TPN induced liver failure.

Intestinal transplantation

• Is reserved for patients who have a risk of death due to complications of TPN or underlying GI disease
• 5 year survival post intestinal transplantation is 50%.
• Indications for intestinal transplantation
  • Recurrent catheter associated infections
  • TPN associated liver disease
  • Complications of venous thrombosis
  • Frequent episodes of dehydration where fluid losses exceed the maximum infusion rates.
  • Can be combined with a liver transplant if required.

Surgical options for long term intestinal failure

• This can be considered after 6 months.
  • Patient needs to be nutritionally replete before any surgery is considered. There is minimal evidence of efficacy for these treatments.
• Options
  • Reversing small bowel segments – slows down transit thus increasing intestinal absorption
  • Bianchi technique – bowel is divided along its long access, re-tuberalised and then re-anastomosed.