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Anal Fistula

Disease Details

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Description: A chronic, abnormal connection between the epithelialized surface of the anal canal and the perianal skin.
Type: Anal fistula is not generally classified by a type of genetic transmission because it is primarily acquired and not inherited. It usually results from infection, inflammation, or trauma leading to an abnormal connection between the anal canal and the skin. Genetic factors are not typically involved in its development.
Signs And Symptoms: Anal fistulae can present with the following symptoms:
skin maceration
pus, serous fluid and/or (rarely) feces discharge — can be bloody or purulent
pruritus ani — itching
depending on presence and severity of infection:pain
swelling
tenderness
fever
unpleasant odorThick discharge, which keeps the area wet
Prognosis: The prognosis for an anal fistula varies depending on several factors, including the complexity of the fistula, its location, and the patient's overall health. Simple fistulas often have a good prognosis with appropriate surgical treatment, leading to full recovery. However, complex or recurrent fistulas may require multiple surgeries and a more prolonged healing process. Proper management and follow-up care are essential to minimize complications and improve outcomes.
Onset: An anal fistula typically begins with an infection in an anal gland, which can cause an abscess. The abscess may then drain to the skin surface near the anus, creating a fistula. The onset may occur gradually, with symptoms like pain, swelling, and discharge near the anus. If not treated, the fistula can persist or even worsen over time.
Prevalence: The prevalence of anal fistula varies, but it is estimated to affect approximately 1 to 2 people per 10,000 annually. The condition is more common in men than in women and is often associated with underlying conditions such as Crohn's disease.
Epidemiology: A literature review published in 2018 showed an incidence as high as 21 people per 100,000. "Anal fistulas are 2–6 times more prevalent in males than females, with the condition occurring most frequently in patients in their 30s and 40s."
Intractability: An anal fistula can be challenging to treat but is not generally considered intractable. While simple cases can often be resolved with surgical intervention, more complex fistulas or those associated with underlying conditions such as Crohn's disease may require multiple treatments and careful management. It's essential to consult a healthcare professional for a tailored treatment plan.
Disease Severity: Anal fistulas vary in severity. They can range from minor, simple fistulas that may cause mild discomfort and discharge to complex or multiple fistulas that can lead to significant pain, recurrent infections, and complications such as abscesses. The severity often depends on the fistula's location, depth, and whether it involves the sphincter muscles.
Healthcare Professionals: Disease Ontology ID - DOID:0060328
Pathophysiology: An anal fistula is an abnormal connection between the epithelialized surface of the anal canal and the perianal skin.

**Pathophysiology:**
1. **Initial Infection:** It typically begins with an infection in one of the anal glands, which can form an abscess.
2. **Abscess Formation:** The abscess may fail to heal properly and can form a tract.
3. **Tract Formation:** The tract may persist even after the abscess is drained or bursts, forming a chronic fistula.
4. **Chronic Inflammation:** This leads to a cycle of recurring infection and inflammation, perpetuating the fistula.

Key contributing factors include Crohn's disease, trauma, radiation therapy, tuberculosis, and other conditions that cause persistent inflammation or obstruction in the anal glands.
Carrier Status: Anal fistula is a condition where there is an abnormal connection between the lining of the anal canal and the skin near the anus. Carrier status is not applicable to anal fistula as it is not a genetic or inheritable condition.
Mechanism: **Mechanism:**
An anal fistula is an abnormal connection or tunnel between the epithelialized surface of the anal canal and the perianal skin. It usually results from an anorectal abscess that wasn't completely healed and still has a tract leading to the skin. The main mechanism involves chronic infection and subsequent abscess formation within the glands of the anal region, leading to an abnormal passage that connects the anal canal to the skin surface.

**Molecular Mechanisms:**
The exact molecular mechanisms underlying the formation of anal fistulas are not well-defined, but common factors include:
1. **Inflammatory Cytokines:** Chronic inflammation plays a critical role, with cytokines like TNF-α, IL-1β, and IL-6 contributing to the inflammatory response.
2. **Matrix Metalloproteinases (MMPs):** MMPs, particularly MMP-9, are involved in tissue remodeling and degradation of extracellular matrix, which may facilitate the formation of the fistulous tract.
3. **Epithelial-to-Mesenchymal Transition (EMT):** EMT processes can contribute to the abnormal epithelial and mesenchymal characteristics of the fistula tract.
4. **Microbiome Dysbiosis:** Alterations in the local microbiome may exacerbate inflammation and interfere with normal healing processes. Bacterial species involved in ongoing infection can maintain the fistulous tracts through persistent inflammation and secondary infections.
5. **Genetic Factors:** Specific genetic predispositions, though not well-documented, may influence susceptibility to chronic perianal diseases and fistula formation.

Understanding these molecular mechanisms can help in developing targeted therapies to manage and treat anal fistulas more effectively.
Treatment: There are several stages to treating an anal fistula:
Definitive treatment of a fistula aims to stop it recurring. Treatment depends on where the fistula lies, and which parts of the internal and external anal sphincters it crosses. However, treatment is challenging as complete eradication of the anal sphincters may lead to continence impairment, but failure to excise the affected areas results in recurrence. Those already treated for recurring anal fistula are at higher risk to experience re-recurrence of the disease. [1]

Lay-open of fistula-in-ano – this option involves an operation to cut the fistula open. Once the fistula has been laid open it will be packed on a daily basis for a short period of time to ensure that the wound heals from the inside out. This option leaves behind a scar, and depending on the position of the fistula in relation to the sphincter muscle, can cause problems with incontinence. This option is not suitable for fistulae that cross the entire internal and external anal sphincter.
Cutting seton – if the fistula is in a high position and it passes through a significant portion of the sphincter muscle, a cutting seton (from the Latin seta, "bristle") may be used. This involves inserting a thin tube through the fistula tract and tying the ends together outside of the body. The seton is tightened over time, gradually cutting through the sphincter muscle and healing as it goes. This option minimizes scarring but can cause incontinence in a small number of cases, mainly of flatus. Once the fistula tract is in a low enough position it may be laid open to speed up the process, or the seton can remain in place until the fistula is completely cured. This was the traditional modality used by physicians in Ancient Egypt and formally codified by Hippocrates, who used horsehair and linen.
Seton stitch – a length of suture material looped through the fistula which keeps it open and allows pus to drain out. In this situation, the seton is referred to as a draining seton. The stitch is placed close to the ano-rectal ring – which encourages healing and makes further surgery easy.
Fistulotomy – till anorectal ring
Colostomy – to allow healing
Fibrin glue injection is a method explored in recent years, with variable success. It involves injecting the fistula with a biodegradable glue which should, in theory, close the fistula from the inside out, and let it heal naturally. This method is perhaps best tried before all others since, if successful, it avoids the risk of incontinence, and creates minimal stress for the patient.
Fistula plug involves plugging the fistula with a device made from small intestinal submucosa. The fistula plug is positioned from the inside of the anus with suture. According to some sources, the success rate with this method is as high as 80%. As opposed to the staged operations, which may require multiple hospitalizations, the fistula plug procedure requires hospitalization for only about 24 hours. Currently, there are two different anal fistula plugs cleared by the FDA for treating ano-rectal fistulae in the United States. This treatment option does not carry any risk of bowel incontinence. In the systematic review published by Dr Pankaj Garg, the success rate of the fistula plug is 65–75%.
Endorectal advancement flap is a procedure in which the internal opening of the fistula is identified and a flap of mucosal tissue is cut around the opening. The flap is lifted to expose the fistula, which is then cleaned and the internal opening is sewn shut. After cutting the end of the flap on which the internal opening was, the flap is pulled down over the sewn internal opening and sutured in place. The external opening is cleaned and sutured. Success rates are variable and high recurrence rates are directly related to previous attempts to correct the fistula.LIFT Technique is a novel modified approach through the intersphincteric plane for the treatment of fistula-in-ano, known as LIFT (ligation of intersphincteric fistula tract) procedure. LIFT procedure is based on secure closure of the internal opening and removal of infected cryptoglandular tissue through the intersphincteric approach. Essential steps of the procedure include, incision at the intersphincteric groove, identification of the intersphincteric tract, ligation of intersphincteric tract close to the internal opening and removal of intersphincteric tract, scraping out all granulation tissue in the rest of the fistulous tract, and suturing of the defect at the external sphincter muscle. The procedure was developed by Thai colorectal surgeon, Arun Rojanasakul, The first reports of preliminary healing result from the procedure were 94% in 2007. Additional ligation of the intersphincteric fistula tract did not improve the outcome after endorectal advancement flap.
Fistula clip closure (OTSC Proctology) is a recent surgical development, which involves the closure of the internal fistula opening with a superelastic clip made of nitinol (OTSC). During surgery, the fistula tract is debrided with a special fistula brush and the clip is transanally applied with the aid of a preloaded clip applicator. The surgical principle of this technique relies on the dynamic compression and permanent closure of the internal fistula opening by the superelastic clip. Consequently, the fistula tract dries out and heals instead of being kept open by continuous feeding with stool and fecal organisms. This minimally-invasive sphincter-preserving technique has been developed and clinically implemented by the German surgeon Ruediger Prosst. First clinical data of the clip closure technique demonstrate a success rate of 90% for previously untreated fistulae and a success rate of 70% for recurrent fistulae.
VAAFT is a surgical kit for treating anal fistulae. The system comprises:A video telescope (fistuloscope) to allow surgeons to see inside the fistula tract.
A unipolar electrode for diathermy of the internal tract. This is connected to a high frequency generator.
A fistula brush and forceps for cleaning the tract and clearing any granulation tissue.The VAAFT procedure is done in two phases, diagnostic and operative. Before the procedure, the patient is given a spinal or general anaesthetic and is placed in the lithotomy position (legs in stirrups with the perineum at the edge of the table). In the diagnostic phase, the fistuloscope is inserted into the fistula to locate the internal opening in the anus and to identify any secondary tracts or abscess cavities. The anal canal is held open using a speculum and irrigation solution is used to give a clear view of the fistula tract. Light from the fistuloscope can be seen from inside the anal canal at the location of the internal opening of the fistula, which helps to locate the internal opening. In the operative phase of the procedure, the fistula tract is cleaned and the internal opening of the fistula is sealed. To do this, the surgeon uses the unipolar electrode, under video guidance, to cauterise material in the fistula tract. Necrotic material is removed at the same time using the fistula brush and forceps, as well as by continuous irrigation. The surgeon then closes the internal opening from inside the anal canal using stitches and staples.
Compassionate Use Treatment: Anal fistula is an abnormal connection between the epithelialized surface of the anal canal and the perianal skin. For those who do not respond to standard treatments, experimental and off-label options may be considered.

1. **Stem Cell Therapy**: There have been some studies using adipose-derived stem cells or expanded allogeneic bone marrow stem cells to promote healing in complex anal fistulas, especially in patients with Crohn's disease.

2. **Fibrin Glue**: This is often used off-label as a less invasive method to promote healing by sealing the fistula tract.

3. **Platelet-Rich Plasma (PRP)**: PRP injections are sometimes used to enhance healing due to their growth factor content, although this remains experimental.

4. **Biological Agents**: For patients with Crohn's disease, off-label use of biological treatments like infliximab or adalimumab may help in reducing inflammation and promoting fistula closure.

5. **Video-Assisted Anal Fistula Treatment (VAAFT)**: This is a minimally invasive technique that uses an endoscope to visualize and treat the fistula from within.

These treatments are generally considered when conventional therapies have failed, and they might not be widely available or covered by insurance. Consultation with a colorectal specialist is recommended to explore these options and determine the most appropriate treatment based on individual patient circumstances.
Lifestyle Recommendations: For managing an anal fistula, several lifestyle recommendations can help alleviate symptoms and support treatment:

1. **Dietary Adjustments**:
- Increase fiber intake to promote healthy bowel movements and reduce constipation. This can be achieved by consuming fruits, vegetables, whole grains, and legumes.
- Stay hydrated by drinking plenty of water throughout the day.

2. **Hygiene**:
- Maintain good anal hygiene by cleaning the area gently with warm water after bowel movements. Avoid using harsh soaps or wipes that may irritate the skin.

3. **Sitz Baths**:
- Take warm sitz baths several times a day to help keep the area clean and provide relief from discomfort.

4. **Regular Exercise**:
- Engage in regular physical activity to maintain overall health and promote good digestive function.

5. **Avoid Straining**:
- Avoid straining during bowel movements. If needed, use stool softeners or laxatives as recommended by your healthcare provider.

6. **Medical Follow-Up**:
- Keep regular follow-up appointments with your healthcare provider to monitor the condition and ensure appropriate treatment.

7. **Avoid Prolonged Sitting**:
- Try to minimize prolonged periods of sitting, and use a cushion to reduce pressure on the anal area if necessary.

Implementing these lifestyle changes can help manage symptoms and support overall treatment effectiveness for those with anal fistulas.
Medication: Medication is generally not the primary treatment for an anal fistula. Instead, surgery is often required to correct the condition. However, some medications may be prescribed to manage symptoms or treat infections associated with an anal fistula. These may include:

1. **Antibiotics**: To treat or prevent infection.
2. **Pain relievers**: Over-the-counter options like acetaminophen or ibuprofen to manage pain.
3. **Stool softeners**: To reduce strain during bowel movements and promote healing.

Always consult a healthcare provider for advice tailored to your specific condition.
Repurposable Drugs: For anal fistula, there is limited evidence on repurposable drugs. Treatment usually involves surgical intervention. Some studies suggest potential benefits of antibiotic therapy or immunomodulatory agents, but these are not standard treatments. Always consult healthcare providers for personalized advice.
Metabolites: Anal fistula does not directly relate to specific metabolites as it is a condition characterized by an abnormal connection between the epithelialized surface of the anal canal and the perianal skin. Its primary concern is infection and inflammation rather than metabolic imbalances, so specific metabolites are not identified for this condition in typical diagnostic or treatment approaches.
Nutraceuticals: Nutraceuticals are food-derived products that provide health benefits, including prevention and treatment of diseases. However, there is limited scientific evidence supporting the effectiveness of nutraceuticals specifically for anal fistula. Standard treatment for anal fistula typically involves surgical intervention. Nutraceuticals may support general health and recovery but are not recognized as primary treatments for this condition. Always consult with a healthcare professional for appropriate diagnosis and treatment options.
Peptides: Peptides and nanoparticles (nan) are emerging fields of research in the treatment of anal fistula. Peptides, which are short chains of amino acids, may offer therapeutic benefits such as promoting wound healing and reducing inflammation. Studies have explored the use of peptide-based treatments to enhance tissue regeneration in fistula tracts.

Nanoparticles, on the other hand, can serve as targeted drug delivery systems. They have the potential to deliver therapeutic agents directly to the fistula site, improving the efficacy of treatment and minimizing side effects. Research in this area is ongoing, and while promising, these treatments have yet to become standard clinical practice.