Aortoenteric Fistula (AEF)
The aorta is the largest artery in the body. It rises from the heart's left ventricle (the major chamber that pumps blood out of the heart) and is filled with oxygen-rich blood that travels throughout the body. A fistula is an abnormal, tubelike connection between two structures inside the body. When the connection is between the aorta and a loop of bowel that is near the aorta it is known as an aortoenteric fistula (AEF).
There are two different types of AEF:
- Primary: Occurs when a chronic, untreated aortic aneurysm damages or destroys the aortic and bowel tissue.
- Secondary: Occurs due to inflammation of previous aortic graft surgery that is near a section of bowel. This type is more common than primary AEF.
This rare condition is fatal if left untreated.
The main symptoms of AEF are bloody stool and signs of infection (sepsis). These symptoms indicate a serious condition and patients should seek immediate medical attention. Other symptoms of the condition include:
- An abdominal mass
- Abdominal pain
- Low blood pressure (hypotension)
- Vomiting fresh blood
- Increased heart rate
- Decreased hemoglobin levels
- Mild tenderness in the abdomen
Causes and Risk Factors
The condition is rare and is almost exclusively diagnosed in patients who had previous surgery to treat an aortic aneurysm or those who have a chronic aortic aneurysm. When the condition occurs due to a chronic, untreated aortic aneurysm, it can be closely associated with atherosclerosis, the buildup of plaque in the arteries. Other conditions that may cause primary AEF to develop are:
- Mycotic infarction
- Collagen vascular disease
The condition can affect both men and women and typically affects adults.
Diagnosis of AEF generally begins with the physician taking a medical history and performing an emergency physical examination. Abdominal X-rays are also used to make an initial diagnosis if the patient is experiencing blood in their stool.
Other imaging tests include MRI, CT scan or aortic angiogram. Some of the diagnostic imaging tests require a special dye to be injected into the vein so that it shows up more clearly on the images. The CT scan is the most commonly used diagnostic tool because it is minimally invasive and is unlikely to dislodge a clot if one is present.
In some rare cases, the aortic aneurysm is discovered during a diagnostic screening for another condition. Other patients may need exploratory surgery known as a laparotomy to diagnose the condition.
Because AEF is a life-threatening condition, treatment is typically needed immediately and is most often in the form of emergency surgery. Prior to surgery, a series of broad-spectrum antibiotics to help fight off the infection will also be prescribed.
The focus of surgical treatment will be to confirm the diagnosis, control bleeding, repair the damaged area of bowel, and remove the aneurysm or graft that is causing the issue.
During the surgery, if the condition is caused by a previous aortic graft, that graft will be removed. Once the graft is removed, the surgeon may create a bypass around the area or may only replace the graft. The opening of the fistula is then closed, either with a new graft or by stitching together the two sides. The method of closure will depend on the size of the opening and whether a bypass was possible. For patients who are in good health, a bypass around the infected area may be created over a series of surgeries rather than all at once. This allows the patient to heal after each surgery.
The knowledgeable and highly trained staff at the Cedars-Sinai Heart Institute will work with each patient to determine the best treatment option.