This study aims to evaluate if the amount of time a person experiences symptoms of an anal fistula before having surgery affects their surgical outcomes and recovery.

An anal fistula is a chronic condition that typically requires surgery to heal properly. In routine clinical practice, many patients experience a significant delay before getting surgery due to a variety of reasons, such as under-reporting symptoms, misdiagnosis, or prolonged conservative treatments. Doctors want to understand if this delay in surgical intervention allows ongoing infection and scarring to complicate the surgery and worsen the patient's recovery.

To investigate this, researchers will observe 90 adult patients who are undergoing definitive surgery for a primary anal fistula. The participants will be divided into three groups based on how long they had symptoms before their operation:

3 months or less Between 3 and 6 months More than 6 months

The main goal of the study is to compare these groups to see how many patients achieve complete clinical healing and how many experience a recurrence (the fistula returning) within 12 months after the surgery. Additionally, the study will track secondary outcomes, including how long it takes the wound to heal completely, any postoperative complications, changes in bowel control (fecal incontinence), pain resolution, and the patient's overall postoperative quality of life. The findings will help inform both doctors and patients on the optimal timing for anal fistula surgery.

This prospective cohort study evaluates whether the duration from symptom onset to surgical intervention influences key clinical outcomes in anal fistula.

The estimated required sample size is 90 patients, distributed evenly with 30 patients in each of the three groups. This sample was calculated using G*power software, assuming an alpha of 0.05, a power of 0.80, and a hypothesized medium effect size difference (0.3) between the groups using a one-way ANOVA test.

Study Procedures and Data Collection:

• Temporal Measurement: The primary exposure variable is the precise interval in days calculated by subtracting the documented symptom onset date from the surgery date. This onset date is captured from initial outpatient clinic notes, emergency department records, or primary care referrals.
• Preoperative Assessment: Magnetic Resonance Imaging (MRI) will be used to classify the fistula's complexity using Park's classification extended by St. James University Hospital, and the external opening location will be documented using Goodsall's rule.
• Intraoperative Protocol: Following an examination under anesthesia (EUA) with tract probing, the surgical intervention will be performed. Researchers will document the procedure type, operative time, estimated blood loss, extent of sphincterotomy, and any intraoperative findings.
• Postoperative Monitoring: Pain will be assessed using a 10 cm Visual Analog Scale (VAS) at 6 hours, 12 hours, 24 hours, 1 week, 2 weeks, and at clinic visits at 1, 3, 6, and 12 months. Fecal incontinence will be evaluated using the Wexner Cleveland Clinic Fecal Incontinence Score, with a clinically significant deterioration defined as a 2-point or greater increase. Clinical healing will be verified by digital rectal exam and proctoscopy.

Inclusion Criteria:

• Patients aged 18 years or older diagnosed with primary cryptoglandular anal fistula confirmed by clinical examination and preoperative imaging (MRI).
• Patients who will be undergoing definitive surgical intervention for anal fistula at Assiut University Hospital between 2026 and 2028.
• Complete medical records available, including documented symptom onset date (defined as first reported perianal pain, swelling, or discharge) and surgery date.
• Minimum postoperative follow-up of 12 months, with clinical assessment data on healing and recurrence.

Exclusion Criteria:

• Fistulas due to Crohn's disease, tuberculosis, malignancy, trauma, radiation, or obstetrical injury.
• Pregnant women.
• Recurrent anal fistulas or those with prior surgical intervention for the same fistula.
• Incomplete records or loss to follow-up before 6 months postoperatively.
• Patients with comorbidities precluding surgery (e.g., uncontrolled coagulopathy or active systemic infection).

The study population consists of adult patients (aged 18 years or older) who are diagnosed with primary cryptoglandular anal fistula. Diagnosis must be confirmed by clinical examination and preoperative MRI. These patients will be undergoing definitive surgical intervention at the Department of Surgery in Assiut University Hospital between 2026 and 2028. The population excludes pregnant women, individuals with recurrent fistulas or prior surgical intervention for the same fistula, and those whose fistulas are due to specific conditions like Crohn's disease, tuberculosis, malignancy, trauma, radiation, or obstetrical injury.