What is a fistula?

What is a Fistula?

A fistula is an abnormal connection or communication between two epithelial-lined surfaces, which can occur between two portions of the intestine, between the intestine and another hollow organ, or between an internal organ and the skin. 1, 2, 3

General Definition and Pathophysiology

• Fistulae form due to loss of wall integrity from an underlying insult, leading to penetration of an adjacent organ or epithelialized surface 1
• These abnormal tracts can develop between various anatomical structures throughout the body, including gastrointestinal, genitourinary, and vascular systems 2, 4, 3
• The term "fistula" (plural: fistulae) derives from the Latin word meaning "pipe" or "tube" 5

Context-Specific Definitions

Vascular Access Fistulae

• In the context of hemodialysis, a fistula refers to an autogenous autologous arteriovenous fistula, also called a "native" fistula, which is a surgically created connection between an artery and vein 5
• Common types include the Brescia-Cimino (radiocephalic) fistula between the radial artery and cephalic vein at the wrist 5
• These are distinct from grafts, which use synthetic or biological conduit material rather than native vessels 5

Gastrointestinal and Perianal Fistulae

• In inflammatory bowel disease (particularly Crohn's disease), fistulae are tracts connecting the anus or rectum to the perianal skin or other organs 5
• A simple fistula is a single extra-enteric tract connecting to another bowel segment, organ cavity, or skin surface 5
• A complex fistula consists of multiple extra-enteric tracts involving multiple structures, often showing an asterisk or star configuration, or has one or more of the following: extensions, multiple external openings, abscess complications, urogenital involvement, or anorectal stricture 5
• Fistulae are named based on the structures they connect (e.g., enteroenteric, enterocutaneous, enterovesical, rectovaginal) 5, 1

Important Distinction: Fistula vs. Sinus

• A sinus is a blind-ending tract without either an external or internal opening, distinguishing it from a true fistula which has openings at both ends 5
• Sinus tracts are blind-ending bowel-wall defects arising from the serosal surface, extending into the perienteric mesentery without connecting to another structure 5

Common Etiologies

• Postoperative complications are the most common cause in developed countries, particularly following gastrointestinal surgery 1, 2
• Inflammatory conditions, especially Crohn's disease, which causes transmural inflammation leading to penetrating complications 5
• Infection and abscess formation, where fistulae typically develop after rupture or drainage of a perianal abscess 6
• Other causes include trauma, malignancy, radiation injury, foreign bodies, and congenital abnormalities 1, 2, 4

Clinical Significance

• Fistulae remain a major clinical problem with potential for serious complications including fluid and electrolyte disturbances, sepsis, and mortality rates up to 30% in gastrointestinal fistulae 2
• Enterovesical, enteroureteral, or enterobiliary fistulae carry increased risk of septic complications and may require urgent surgical intervention 5
• Management requires a multidisciplinary approach addressing nutritional status, tract anatomy delineation, skin care, and treatment of underlying disease 1