Intestinal Fistula

DEFINITION
A fistula is an abnormal collection between two epithelial surfaces, in this case skin and bowel.
- as opposed to a sinus, which is an abnormal connection between an epithelialized surface and a source of infection.

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EPIDEMIOLOGY
As by cause.
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AETIOLOGY

Any chronic inflammatory state or cause of perforation.
Multiple possible causes as per sieve; inflammatory, infectious, tumours, trauma.
Most commonly in crohn's.
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BIOLOGICAL BEHAVIOUR

Classification

1. Anatomical
Entero-cutaneous fistula
Colo-cutaneous fistula
Gastro-cutaneous fistula
Entero-atmospheric fistula, which lies within an open abdomen surrounded by granulation tissues.
- deep if draining into the abdomen causing abdominal peritonitis (bad, septic, hypercatabolic, a big deal)
- superficial if effluent draining onto an open abdominal wound (much better; less sepsis, largely a wound management problem)

2. Aetiological
By cause, eg. crohn's

3. Physiological
Low Output
- <200 ml
Moderate Output
- 200-500 ml
High Output

-  >500 ml

Pathophysiology Issues

1. Classic triad of sepsis, fluid and electrolyte abnormalities and nutrition
- this includes metabolic acidosis from bicarb losses in duodenal / very proximal fistulas
2. The digestive action of certain fistulae (eg pancreatic) can be harmful.
3. Wound care of surrounding skin.

Natural History
1/3 of post-op small bowel fistulas will close spontaneously within 6 weeks.
- provided sepsis, nutrition and wound care adequate

Factors Inhibiting Spontaneous Stoma Closure (FRIEND)
1. Foreign body, including mesh
2. Radiation
3. Infection or inflammatory disease
4. Epithiliazation of a short fistula tract (<2cm)
5. Neoplasia
6. Distal obstruction


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MANIFESTATIONS

Above/below.
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INVESTIGATIONS

As below
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MANAGEMENT

These can pose a major challenge.
- MDT required, involving stoma nurses, surgeons, dietitians, social workers
Resist temptation to primary close the fistula

The Hope Hospital SNAP Protocol

1. S - sepsis

   - search for associated deep and superficial collections
   - drain adequately
   - ?CT guided, ?surgery ?defx of bowel
2. N - nutrition
   - provide adequate, often parenteral
   - fluid and electrolyte balance correction
3. A - anatomy
   - define the fistula anatomy
   - however, not always mandatory to do a fistulogram, only when likely to change operative strategy.
4. P - procedure
   - repair when the pt is well
   - often after six months or so.

Skin Care and Fluid Control
Be concerned with this from moment of first diagnosis.
Secretions can be caustic and abrasive, damaging skin.
Stoma therapist input is required to advise about care of skin around the fistula.
- dressings and bags can be tailored to protect the skin
- and bags to collect the fistula fluid.
May be complex needs for enteroatmospheric fistulae.
Vacuum assisted devices are a cornerstone of modern management.
- especially in enterocutaneous fistulae, where can exclude fistula content from contaminating the abdo wound, even to the point of allowing a skin graft.
Bulk forming agents can help convert a stoma to one with more solid output

Notes on Nutrition
Baseline requirements:
-  20 kcal/kg/day carbs and fat
- 0.8 g/day protein
- can be 50% higher in catabolic state.
Enteral feeding preferrable whenever possible.
- immunological and hormonal benefit
- less complications related to TPN
- cheaper
- mucosal barrier protected
- allows outpatient management.
Trial enteral feeding
- stop if not tolerated or dramatically increases fistula output
- should not convert a low output to high output fistula
Beware malnourished patients
- risk of refeeding syndrome with fluid electroyte derangements and hypophosphataemia
- switch to insluin secretion and change back from fat to carb metabolism, cells take up phosphate actively.
- associated with cardiac, lung, nueromuscular and haematologic complications.

Definitive Treatment

Either Close Spontaneously or Require Surgery


Closing Spontaneously
This is helped by eliminating sepsis, reversing SIRS, optimizing nutrition and blood supply to the wound
If it doesn't close within 4-6 weeks with these sorted, then start thinking definitive surgery will be necessary.

Surgical Notes
Generally wait 3-4 months.
Ideally should have an albumin above 30
Any skin graft on an enterocutaneous fistula should have taken well.

Principles:

1. First case, long case, unrestrained time pressure.
- expect to spend time dividing adhesions and being meticulous about it.
2. Laprotomy and lyse adhesions, define completely the intestinal anatomy.
- know the length of SB, location of fistulae exclude distal obstructions
- if the patient has a frozen abdomen may need to abort; prefer complex controlled situation to a lethal number of challenging enterotomies
3. Decide to resect or repair
- balance risk of short gut with recurrent fistula.
- minimum number of anastomoses is to be preferred
- i prefer to use a hand sewn technique, they have one good shot and I want the best possible anastomosis.
4. Close abdominal wall.
- often complex with a ventral hernia.
- often best to use a prosthetic material rather than a primary closure, helps prevent need for a second procedure.
- need an absorbably mesh like vicryl (dissolve 60-90d) or a biological mesh e.g. porcine dermal produce with cross-linked collagen (clean contaminated at best).

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REFERENCES
Cameron 10th