Comparison of MRI with Surgical Findings in the diagnosis of Fistula-in-Ano

Zafar Nasir, Tariq Mehmood, Armaghan -e-Rehman Mansoor, Nadira Abid, Naveed Ahmed, Humera Nisar, Kausar Illahi Bux, Shumaila Urooj


Introduction: An anal fistula is a connection between two epithelial lined spaces, one of which is the anus or rectum. In recent years, MRI has developed as a tool to diagnose and classify fistula-in-ano. The rationale for using MRI is to find a non-invasive procedure for classifying fistula-in-ano, thus directing proper management of the fistula, including surgical procedure. This can decrease hospital load in terms of patient follow-up.

OBJECTIVE: To determine the diagnostic accuracy of MRI in classifying fistula-in-ano compared with surgical findings.

OUTCOME MEASURE: Diagnostic accuracy of multi-dimensional CT scan

STUDY DESIGN: Cross sectional study

SETTING: Department of Radiology, Jinnah Postgraduate Medical Centre (JPMC), Karachi

SUBJECTS: Patients clinically suspected of having fistula-in-ano due to presence of external opening around the anal region.

METHODS: Patients meeting the inclusion criteria underwent MRI fistula-in-ano after taking consent from patients and maintaining all ethical considerations. The images were evaluated for the presence and site of the fistulous tract according to Parks and colleagues’ Criteria for fistulas. All MRI and surgical findings were recorded on a MRI/Surgery fistula-in-ano form and statistically evaluated using SPS version 10.0.

RESULTS: A total of 173 patients showing 201 fistulous tracts were enrolled in this study. The mean age of enrolled participant was 43.5 ±8 years. The overall sensitivity of MRI in diagnosing fistula in ano was 95 % and specificity 68.2 %.  Positive predictive value for correctly diagnosing fistula in ano was 92.1 % and Negative predictive value, 77.7 %.

CONCLUSION:  MRI is a very sensitive and specific modality for diagnosis and classification of fistula-in-ano.

KEY WORDS: Fistula-in-ano, Sensitivity, Specificity, MRI fistula-in-ano, Histopathology, JPMC  

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