Enterocutaneous fistula

Fistula: an abnormal communication between two epithelialised surfaces, one of which is a hollow organ.

Enterocutaneous fistula: between the lumen of the GIT and the skin
Enteroatmospheric fistula: between the lumen of the GIT and the wound of an open abdomen.
Can be congenital or acquired but most commonly iatrogenic (75-85% post-op)
- Anastomotic breakdown
- Dehiscence of surgically closed segment of stomach/bowel
- Unrecognised enterotomy
Predispositions:
- Intrinsic intestinal disease (Crohn's)
- Radiation enteritis
- Distal obstruction
- Hostile abdo
- Malnourished
Spontaneous enteric fistula: FRIEND
- Foreign body
- Radiation
- Inflammation/infection (TB, actinoycosis)
- Epithelialisation
- Neoplasia
- Distal obstruction

Presentation

Mostly occur in the post-operative setting
Triad:
- Sepsis
- Fluid/electrolyte imbalance
- Malnutrition
Often not progressing well post-op, with first abdominal symptoms then signs of bowel obstruction, then a wound infection will be seen 7-10 days post-op, which will eventually show enteric contents in the wound.
Enteroatmospheric fistulas will present with an exposed segment of bowel seen through a large fascial defect

Classification

Output
- High output: >500ml/24hrs
  - Commonly coming from the ileum
- Medium: 200-500
- Low <200
Location
- Proximal fistulas generally have higher output, greater fluid and electrolyte losses, and greater loss of digestive capacity
- Distal fistulas have lower output and are therefore easier to manage and more likely to close spontaneously

Considerations:

Hypersecretory gastric state
Intra-hepatic cholestasis - related to loss of bile salts
Malnutrition
- Bypass
- Loss of protein-rich secretions
- Lack of nutrient intake
- Sepsis
Skin and surgical wound complications

Management

Early surgical intervention is ineffective
Three phases:
- Stabilisation
- Staging and supportive care
  - Try and get it to close spontaneously, by reducing output
- Definitive management
Need MDT approach
- Surgeon
- Nutritionist
- Enterostomal therapist
  - Consider VAC
- Interventional radiologist
- Gastroenterologist

Overall approach mnemonic: SNAPS (a bit simplistic - see below for full process)

Sepsis
- Obtain adequate drainage
- May involve defunctioning of the bowel
Nutrition
- Often parenteral nutritional support
Anatomy (define fistula tract)
- Image the site of leak
- CT with contrast
Procedure
- Ultimately aim for reparative procedure
- Delay until patient is well enough that success is likely
Skin care
- Determine what is coming out of the fistula and protect the skin accordingly

Natural history with best management:

54% closed spontaneously, and 18% needed definitive surgery
>90% of fistulas that closed did so within 1 month, <10% of fistulas closed after 2 months, and no fistulas closed spontaneously after 3 months
Uncomplicated proximal fistulas have higher spontaneous closure rates

Stabilisation / initial medical treatment

- Resus + antibiotics - halt catabolism
  - Aggressive fluid therapy
  - Cease antibiotics 5-7 days after source control has been obtained and sepsis has resolved.
  - Antibiotics in non-septic patients with ECF is controversial, and there is no evidence of improved outcomes, so probably shouldn't be done routinely.
- CT. If evidence of free GIT perforation or diffuse peritonitis, need urgent exploration. Focus on infection drainage and exteriorisation of any leaking bowel. Don't redo the anastomosis in the infected field in order to create a stoma, but you could divert the faecal stream higher up.
- Infected wounds, abscesses, etc are opened and drained. Perc drainage of intra-abdo collections (allows changing a complex fistula to a simple one) - generally done through anterior abdominal wall, but can be done transgastric/transrectal etc.
- Fix electrolytes
- Involve MDT - consistent messaging
- Set realistic expectations with patient and family

Staging and supportive care

- Nutrition:
  - Allow 500mL/24 hours clear fluids
  - Low-output fistulas (<200mL/day):
    - In general, aim for enteral feeding, if they are able to absorb enough
    - First, try a short period of bowel rest after the patient has been stabilised to see if fistula will close (?TPN)
    - If fistula continues, start on oral diet
    - If fistula output does not increase substantially with oral diet, can continue; but if output increases >1.5L per day, need to stop oral diet and start TPN
  - Moderate or high-output fistulas
    - May be intolerant to nutrition secondary to sepsis, poor absorption, greater fluid and nutrient loss from fistula, or difficulty with infection/excoriation of skin
  - TPN - trace elements, multivitamins, vitamin K +/- octreotide (reduces GI secretion - yet to be proven, and come with side effects)
    - Indications:
      - Fistula output >1.5L per day
      - <75cm of intestinal length prior to the fistula
      - Intestinal discontinuity
    - Can be given either exclusively or as an adjunct
  - Feeding down distal limb - Starkey says more trouble than it is worth
- Fluid status - needs to be carefully maintained, taking into account the fistula losses. Can use St Mark's Intestinal Failure Unit worksheet to establish necessary electrolyte replacement.
  - Duodenal or pancreatic fistulas may require bicarbonate to prevent metabolic acidosis.
- NGT only if obstructed
- PPI - decreases risk of PUD
- Wound care
  - The real challenge is management of high-output and enteroatmospheric fistulas
  - Most low-output fistulas can be managed with gauze and an ostomy appliance
  - NPWT has become widespread, but is not really proven to improve healing
  - Sometimes can simply put a drain down the tract
  - Skin care - prevent excoriation using a stomahesive product (zinc oxide, aluminium paste, karaya powder)
- Fistula output reduction
  - Anticathartics (loperamide) - give loperamide up to 16mg daily
  - Somatostatin - useful in high-output fistulae
    - Dosage given in most studies seems to be octreotide 100microg subcut q8h
  - Antisecretories - PPI generally given
  - Cholestyramine - for bilioenteric fistulae
- Once initial resus and medical treatment is progressing, define the fistula tract (origin, course, length) with a fistulogram/CT/endoscopy
  - Can check for bilirubin/amylase
  - Methylene blue may be helpful

Definitive management

- Definitive surgery for patients whose fistulae have failed to heal (about 50%)
  - Simple fistula - wait 3/12
  - Complex - wait 6-12 months
  - May also require abdo wall reconstruction
    - Botox or component separation
  - But you don't HAVE to wait more than 6 weeks if all other criteria are optimised
- Optimal criteria for surgery:
  - Clinically stable
  - Psychologically stable and willing
  - Albumin > 25
  - Period of convalescence >6 weeks since insult
  - Output controlled at skin - should look basically like an odd stoma, without sepsis
- Surgery
  - One-stage procedure
  - Incision in a clean area
  - Careful adhesiolysis
  - Fistula tract excision and segmental resection of the involved segment of intestine and reanastomosis
    - Simple closure of fistula tract almost always results in recurrence
  - Bail-out option is exteriorisation of both ends of bowel
  - Resect bowel as necessary, but limit anastomosis to minimum
  - 2 layers permanent suture for anastamosis with omental covering
- Likely need TPN and slow rehab post-op too