24. Fistulas

1. Definition

• Fistula → abnormal communication between two epithelial-lined surfaces (hollow organs, or an organ and the skin)
• Sinus → blind-ending track from an epithelial surface into the tissues, lined by granulation tissue
• Stoma → surgically created opening (therapeutic fistula)

2. Aetiology

Congenital

• Branchial fistula, thyroglossal (usually a sinus or cyst)
• Tracheo-oesophageal fistula
• Umbilical → patent urachus, vitello-intestinal duct
• Anorectal malformations → rectovesical, rectovaginal
• Preauricular sinus

Acquired

• Postoperative → anastomotic leak (most common enterocutaneous fistula, 75–85%)
• Trauma
• Inflammation and infection → Crohn's disease, diverticulitis, tuberculosis, actinomycosis, anorectal abscess
• Malignancy → colorectal, cervical, bladder cancer
• Radiotherapy
• Foreign body, mesh erosion
• Ischaemia

Artificial (therapeutic)

• Gastrostomy, colostomy, ileostomy, cystostomy
• Arteriovenous fistula for haemodialysis

3. Pathological characteristics

• Track lined by granulation tissue or epithelium
• Internal opening → in the organ of origin
• External opening → on the skin, often with granulation tissue
• Track → simple, complex, with abscess cavities

4. Classification

By origin

• Congenital, acquired, artificial

By opening

• External → organ to skin (enterocutaneous, biliary, pancreatic)
• Internal → organ to organ (colovesical, enteroenteric, cholecystoduodenal, rectovaginal)

By output (enterocutaneous)

• Low output → < 200 mL/24 h
• Moderate → 200–500 mL/24 h
• High output → > 500 mL/24 h

By anatomy

• Proximal (stomach, duodenum, jejunum) → high output, high losses
• Distal (ileum, colon) → low output

By shape of the opening

• Tubular → long track, granulation-lined; may close spontaneously
• Labial (lip-shaped) → mucosa fused with skin; never closes spontaneously

By content

• Purulent, salivary, biliary, pancreatic, intestinal (faecal), urinary

5. Clinical manifestations

• External opening with discharge of pus, bowel content, bile, urine
• Skin excoriation → digestive enzymes (small bowel, pancreatic)
• Fluid and electrolyte loss → dehydration, hypokalaemia, metabolic acidosis (pancreatic, small bowel)
• Malnutrition → protein loss
• Sepsis → undrained collections
• Internal fistulas:
  • Colovesical → pneumaturia, faecaluria, recurrent urinary infections
  • Rectovaginal → faeces or gas per vagina
  • Cholecystoduodenal → gallstone ileus, pneumobilia
  • Gastrocolic → faeculent vomiting, diarrhoea

6. Diagnosis

• Analysis of discharge → amylase, bilirubin, creatinine
• Oral dye or charcoal → confirms bowel origin
• Fistulography → contrast through the external opening
• CT with contrast → collections, anatomy, cause
• MRI → perianal fistulas
• Endoscopy, cystoscopy
• Biopsy → exclude malignancy, Crohn's disease, tuberculosis

7. Factors preventing spontaneous closure (FRIENDS)

1. Foreign body (mesh, suture)
2. Radiation
3. Infection, inflammatory bowel disease
4. Epithelialisation of the track
5. Neoplasm
6. Distal obstruction
7. Steroids, short track (< 2 cm), sepsis
8. Also → high output, large defect (> 1 cm), malnutrition

8. Principles of treatment

Conservative: SNAP

1. Sepsis control → drain collections (percutaneous or surgical), antibiotics
2. Nutrition → parenteral or enteral nutrition; correct fluids and electrolytes
3. Anatomy → define the fistula with imaging
4. Protection of skin and plan for surgery → stoma bags, barrier creams, wound managers
5. Reduce output → nil by mouth, proton pump inhibitors, octreotide, loperamide
6. Spontaneous closure → most low-output tubular fistulas close in 4–6 weeks

Surgical

• Indications:
  • No closure after 6–12 weeks of conservative care
  • FRIENDS factors present
  • Labial fistula
• Delay elective surgery → 3–6 months, when inflammation and adhesions settle
• Operations:
  • Resection of the fistula with the affected bowel and primary anastomosis
  • Excision of the track (fistulectomy)
  • Repair of the defect, abdominal wall reconstruction
  • Proximal diversion (stoma) when needed
• Internal fistulas → resection of the diseased segment (sigmoid colectomy for colovesical fistula), repair of the other organ

9. Complications

• Dehydration, electrolyte imbalance
• Malnutrition
• Sepsis
• Skin excoriation
• Death → 5–20% in enterocutaneous fistulas