MR imaging of fistula in ano: indications and contribution to surgical assessment

Puborectalis Muscle Involvement on Magnetic Resonance Imaging in Complex Fistula: A New Perspective on Diagnosis and Treatment

PURPOSE

According to recent studies, magnetic resonance imaging (MRI) assessment of complex fistulas provides a significant benefit compared to fistulography, computed tomography, and ultrasonography. The aim of this study was to describe the accuracy of MRI and the importance of identifying puborectalis muscle involvement on MRI in patients with complex fistula.

METHODS

All patients who were clinically diagnosed with 'complex' or showed multiple fistula tracts underwent fistula MRI. Eligible patients were consecutive patients who underwent fistula MRI between September 2018 and September 2019 at our hospital.

RESULTS

A total of 83 patients (74 males, 9 females; 116 tracts) were included in this study. The sensitivity and specificity of MRI in diagnosing fistula tracts were 94.8% and 98.2%, respectively. The sensitivity and specificity in identifying internal opening were 93.9% and 97.3%, respectively. Of the 35 patients with puborectalis muscle involvement in the MRI, 31 images of suprasphincteric-type patients on the Park's classification were classified. The patients of puborectalis involvement were divided into 2 groups according to the surgical procedure that was performed. There were 12 sphincter-saving procedures and 19 sphincter division procedures performed. Recurrence was seen in 2 patients in the sphincter-saving procedure group, while no case was seen in the sphincter division procedure group. Five complications were found in the sphincter division procedure group, of which 2 reported incontinence.

CONCLUSION

Fistula MRI is a highly accurate examination for evaluating complex fistulas, and the puborectalis muscle involvement findings are very important for diagnosis and treatment.

The contribution of preoperative MRI to the surgical management of anal fistulas

PURPOSE

Anal fistula is an abnormal tract or cavity between the anal canal and perianal skin. Surgical treatment of anal fistulas requires the identification of the course of the primary and secondary tracts and their relation with the sphincter musculature in order to appropriately manage them and drain any abscess. Physical examination alone is not as accurate as imaging modalities in detecting these features of the fistula, and recurrences are usually due to missed or inadequately managed infective components. Magnetic resonance imaging (MRI) is the preferred imaging modality for detecting anal fistulas, but which patient group should undergo preoperative MRI is a matter of debate. The aim of this study was to determine the contribution of MRI in the surgical management of anal fistulas.

METHODS

Medical records of patients who underwent surgery for primary anal fistula and preoperative MRI in our University Hospitals from January 1, 2008 to April 15, 2018 were collected anonymously and retrospectively. Any discrepancies between operative findings and MRI reports were noted. Two study groups were formed as per the contribution of preoperative MRI: significant and nonsignificant contribution groups. The significant contribution group included patients with secondary (blind) tracts, horseshoe fistulas, or abscesses undiagnosed at physical examination and examination under anesthesia; those with the location of the internal orifice different from that identified by physical examination; or those with the grade of the fistula assessed to be more advanced after preoperative MRI.

RESULTS

The total number of surgeries was 136. Mean patient age was 43±13 years. There were 106 males. In total, 47 patients suffered from recurrent fistulas. MRI contribution to clinical evaluation was significant in 33.8% of the patients. MRI more frequently provided significant information for complex fistulas than for simple fistulas. Significant preoperative MRI contribution was more frequent if the external opening was more than 2 cm away from the anal canal or when a horseshoe fistula was present.

CONCLUSION

Our study is valuable in linking physical examination findings with preoperative MRI findings. The distance of the external opening from the anal canal was not studied in the literature; our findings support the use of MRI for fistulas with external opening located more than 2 cm from the anus. These fistulas also tend to be complex and have a higher grade. In recurrent cases, MRI contributes not only by establishing the fistula anatomy but also by identifying possible sphincter damage.

Imaging for Inflammatory Bowel Disease

Multiple imaging modalities exist for inflammatory bowel disease. This article explores the use of plain radiographs, contrast radiologic imaging, computed tomography, MRI, ultrasound, and capsule endoscopy. History, technique, indications for use, limitations, and future directions are discussed for each modality.

Fistula-in-ano: when to cut, tie, plug, or sew

INTRODUCTION

Management of fistula-in-ano requires understanding of both perianal and rectal anatomy, as well as the surgical approaches available to ensure the highest possible postoperative continence and wound healing. Further, high rates of recurrence with medical management commonly bring these patients under the care of the colorectal surgeon after variable periods of failed conservative management. Novel techniques provide surgeons with tools to treat increasingly complex fistulas with a focus on maintaining sphincteric functionality and limiting recurrence.

METHOD

This manuscript presents our practice, including perioperative decision making regarding surgical approach, in managing patients with fistula-in-ano.

CONCLUSION

Familiarity with these techniques prepares the general surgeon and colorectal surgeon to improve wound healing and functional outcomes in these patients, especially with complex disease involving the external and internal anal sphincters.