A colovesical fistula is an abnormal connection between the colon and the bladder. This passageway allows contents from the colon to enter the bladder, which can lead to various complications. While not a common condition, it represents a significant health concern.
How Fistulas Develop
Fistulas form when tissues experience prolonged inflammation or infection, often due to injury or disease. This persistent inflammation can gradually erode tissues, creating a channel between two organs not typically connected. For a colovesical fistula, this involves breaching the walls separating the colon and bladder.
Formation often begins with a localized infection or abscess near the colon or bladder. As this infection progresses, it can create a pocket of pus that seeks a path of least resistance to drain. If this abscess ruptures or erodes into an adjacent organ like the bladder, it forms an abnormal connection.
Common Underlying Diseases
Several medical conditions are frequently associated with colovesical fistulas. These conditions typically involve inflammation, infection, or tissue invasion that can bridge the gap between the colon and the bladder.
Diverticulitis is the most frequent cause, accounting for more than two-thirds of cases. This condition involves inflammation of small pouches, called diverticula, that can form in the colon wall, particularly in the sigmoid colon. If a diverticulum becomes inflamed or perforates, it can lead to an abscess. The rupture or erosion of this abscess into the nearby bladder creates the fistula.
Crohn’s disease, a chronic inflammatory bowel disease (IBD), contributes to about 5% to 7% of cases. The persistent, transmural inflammation associated with Crohn’s disease can lead to deep ulcers and tracts that penetrate the full thickness of the bowel wall. These inflammatory processes can extend to adjacent organs, forming fistulas. About one-third of individuals with Crohn’s disease may develop fistulas at some point.
Cancer, particularly colorectal cancer, is responsible for 10% to 20% of colovesical fistulas. Tumors originating in the colon can grow and directly invade the bladder. This invasive growth destroys normal tissue, establishing a pathway between the two organs. Less commonly, bladder cancer can also invade the colon and form a fistula.
Other Significant Causes
Other factors can lead to colovesical fistula formation, though they are less frequent. These causes often involve direct tissue damage or complications from medical interventions.
Radiation therapy for pelvic cancers can damage healthy tissues over time. This damage can lead to chronic inflammation and tissue breakdown, resulting in fistula formation, sometimes years after treatment.
Surgical complications can also contribute. Accidental injury to the colon or bladder during abdominal or pelvic surgery, or issues like an anastomotic leak, can create a pathway for a fistula.
Severe abdominal trauma can directly injure both the colon and the bladder, leading to fistula formation.
Severe localized infections or abscesses in the abdominal or pelvic region can erode into adjacent organs. The inflammatory process can breach the intestinal and bladder walls, resulting in a colovesical fistula.