Overview
A fistula is an unusual link between two lined surfaces in the body. These links can happen between any two cavities, including blood vessels, intestines, vagina, bladder and skin. There are three ways to identify a fistula: its location, function, and cause.
In terms of location, fistulas can be internal, connecting two internal parts of the body, or external, connecting an internal part to an external part. For example, an internal fistula could exist between different parts of the intestine, while an external fistula could exist between the intestine and the skin.
From a functional perspective, we can classify fistulas based on how much fluid they drain. ‘Low-output’ fistulas drain less than 200 milliliters per day, ‘high-output’ ones drain over 500 milliliters, and ‘medium-output’ ones fall in between.
Last but not least, fistulas can also be categorized by cause. They can occur due to trauma, surgical complications, or in relation to certain conditions like Crohn’s disease. This summary specifically covers fistulas that connect the intestine with the skin, known as enterocutaneous fistulas.
Causes
It’s estimated that about 80% of enterocutaneous fistulas, which are abnormal connections between the intestine and the skin, are caused by surgeries, and are thus labeled as being ‘iatrogenic’ in origin. Surgical complications like unintended openings in the intestine or failed joining of intestinal sections can lead to the formation of these fistulas. Situations that increase the risk for fistula creation after surgery include trauma, cancer, and inflammatory bowel diseases.
The remaining 20% of fistulas which aren’t related to surgeries are often the result of certain body-wide conditions like Crohn’s disease, radiation-induced inflammation of the intestine, malignancies, trauma, or reduced blood supply to the intestine.
Risk Factors and Frequency
Enterocutaneous fistula, a medical condition, has a death rate that fluctuates significantly, ranging from 6% to 33%. What causes the illness has a big impact on how often it occurs. It’s seen in 50% of cases involving infected pancreatic necrosis, a very intensive condition. With trauma patients, the rate is between 2% and 25%, whereas people with abdominal sepsis, a serious infection, have a 20% to 25% occurrence rate.
Signs and Symptoms
An enterocutaneous fistula is often caused by postoperative complications. This means a fistula or abnormal connection can occur between the intestines and the skin after a surgery. Patients with a history of injuries, inflammatory bowel disease, or cancer surgery have higher chances of developing a fistula.
Consider this example: A patient who recently had surgery develops a fever, high white blood cell count, intestinal obstruction, and abdominal tenderness, and is diagnosed with a wound infection. Doctors try to treat this by draining the abscess, or pocket of infection. However, contents from the intestine begin to leak into the wound one or two days later. Continual leaking of such contents into the wound confirms the presence of an enterocutaneous fistula.
You can remember the factors that increase the likelihood of a fistula developing and not healing naturally with the REMEMBERED acronym “FRIEND.” This stands for:
- F – Foreign body
- R – Radiation
- I – Inflammation or infection
- E – Epithelialization of the fistula tract
- N – Neoplasm
- D – Distal obstruction
These are the factors that may contribute to a fistula developing and make it unlikely to close up on its own.
Testing
Once a patient is stable, the next step is to examine the fistula, which is an abnormal connection between two parts of the body. There are several imaging methods that can be used to analyze a fistula, including an ultrasound, CT scan, and a procedure known as fistulography. Other helpful tests could include a small bowel follow-through, which is a type of X-ray, and endoscopy studies that use a tiny camera to examine the inside of the body.
Imaging is crucial in understanding where the fluid in the fistula is going. Sometimes, this fluid may not just come out from the external opening of the fistula, but could also be partially leaking into the abdomen, which could form an abscess–a painful, swollen, pus-filled area caused by an infection.
The best imaging test to use is usually the CT scan with oral contrast. This is because it can identify the fistula tract, any leaks in the abdomen, abscesses within the abdomen, obstructions at the end of the fistula, and any foreign bodies that shouldn’t be there.
The less commonly used fistulography can be useful if a CT scan or ultrasound isn’t available, or if these tests don’t provide clear results. Fistulography works by injecting a contrast dye into the external opening of the fistula and then taking X-rays of the area.
Treatment
The first step in the medical care of a patient with a gastrointestinal fistula is to stabilize them. These patients often face a high risk of electrolyte imbalances, sepsis (a life-threatening infection), and malnutrition. It is critical to monitor and regulate these factors for the patient’s survival. Special attention is given to keeping the patient’s fluid levels balanced and correcting any abnormalities in their electrolyte levels because the patient’s condition can severely decline quickly. The precise nature of these electrolyte losses depends on where the fistula is located in the digestive tract and how much it is discharging. Replacing any deficiencies the patient has is important.
In patients suffering from sepsis, identifying the source is crucial and must be treated appropriately. This is because two-thirds of deaths in these patients are attributed to sepsis. Intra-abdominal abscesses (pus-filled pockets in the abdominal cavity) are common in these patients and should be considered as a possible source of the sepsis. Guidelines from the Surviving Sepsis Campaign should be followed while treating such patients.
Most of these patients will require parenteral nutrition (nutrition delivered into a vein), but a set of patients with fistulas in the lower part of the digestive tract may be able to tolerate an elemental diet (a simple, easy-to-digest diet) if the fistula’s output doesn’t increase due to the introduction of food. Adequate nutrition is a key part of the patient’s overall treatment.
Alongside this, the discharge from the fistula should be handled carefully to prevent skin damage and encourage healing. Healthcare providers can employ a variety of wound care strategies for this purpose, similar to using ostomy bag attachments.
The medical team must then decide on the best way to treat the fistula. In some cases, immediate surgery may be necessary, but most fistulas are treated non-surgically since 90% of them typically close by themselves within 5 weeks with medical management. Generally, healthcare professionals may try non-surgical methods for 2 to 3 months before considering surgery. This time allows the fistula to heal on its own and also lowers the risks associated with surgery.
The medical management of a fistula aims to decrease its output and promote spontaneous healing. In cases of high output fistulas, stomach-acid reducing medications and anti-diarrheal drugs may be used. A medication called octreotide, which has been thoroughly studied, can also be used to regulate the fistula’s output. It has shown to decrease output and hospital stays, and increase healing chances. If a fistula is discharging over one liter per day, an octreotide trial can be attempted.
If the fistula doesn’t improve with medical management, surgery becomes a consideration. However, operating on fistulas can be challenging due to the high risk of recurrence and difficulties posed by previous surgeries and adhesions. During surgery, great care must be taken to avoid any accidental injuries while freeing up the bowel and moving organs. In most cases, the best course of action is to remove the fistula tract and a small portion of the adjacent bowel followed by a surgical connection to restore the bowel’s function. As long as the patient is managed properly, given the right nutrition, and given enough time before surgery, a gastrointestinal fistula can be permanently resolved in 80% to 95% of cases.
Related Conditions
When it comes to abdominal symptoms or issues, doctors have to consider different diseases which can cause similar signs. Such conditions might include:
- Abdominal Abscess – a pocket of pus in the abdomen
- Abdominal Aortic Aneurysm – a bulge or swelling in a large blood vessel in the abdomen
- Aortitis – inflammation of the aorta
- Colocutaneous fistula – an abnormal passage between the colon and skin
- Colon Cancer – cancer of the colon
- Enterovesical Fistula – a communication between the intestine and bladder
- Inflammatory Bowel Disease – chronic inflammation of the digestive tract
- Large-Bowel Obstruction – blockage of the large intestine
- Penetrating Abdominal Trauma – injuries that break the abdominal skin or organs
- Peptic Ulcer Disease – sores that develop on the lining of the stomach
- Small Intestinal Diverticulosis – small pouches that form in the small intestine
- Urinary Tract Infection (UTI) and Bladder Infection in women
- Urinary Tract Infection (UTI) in men
- Vascular Surgery for Arteriovenous Malformations – surgery to treat abnormal blood vessels
- Wound Infection – infection in a wound
All these conditions could display similar signs, so doctors need to conduct the right tests to work out what’s really causing the problem.