What is the best investigation for a male patient presenting with one-month diarrhea, colicky abdominal pain, and an anal fistula with an internal opening above the dentate line?

From the Guidelines

The best investigation for this patient is MRI Fistulogram. Given the presentation of one-month diarrhea, colicky abdominal pain, and anal fistula with an internal opening above the dentate line, MRI Fistulogram is the most appropriate diagnostic test. This patient's symptoms strongly suggest anorectal disease, and MRI Fistulogram has been shown to have high sensitivity and specificity for the evaluation of perianal fistula, with a sensitivity ranging from 81% to 100% and specificity from 67% to 100% 1. The use of IV contrast material and diffusion-weighted sequences can further increase the conspicuity of fistulae and discriminate between inflammatory mass and abscess 1.

Some key points to consider when performing an MRI Fistulogram include:

• The use of a 3T or 1.5T magnet, with a 3T magnet providing improved signal-to-noise ratio and spatial resolution 1
• The use of an endoanal coil or multi-channel external phased array body coil, with the phased array body coil providing better visualization of the extent of fistulae and those located in the supralevator space and ischiorectal fossa 1
• The administration of gadolinium-based IV contrast material to enhance the detection of fistula and abscesses 1
• The addition of diffusion-weighted sequences to increase the conspicuity of fistulae and discriminate between inflammatory mass and abscess 1

While other investigations such as CT, Colonoscopy, Barium enema, and CT enteroclysis may provide some information, MRI Fistulogram is the most appropriate test for evaluating perianal fistula. The high sensitivity and specificity of MRI Fistulogram, combined with its ability to provide detailed information about fistula anatomy and extent, make it the best choice for diagnosing and planning treatment for this patient's condition 1.

From the Research

Diagnostic Options for Perianal Fistulas

The patient's symptoms, including one-month diarrhoea, colicky abdominal pain, anal fistula with the internal opening above the dentate line, suggest a complex perianal condition. The best investigation for this condition can be determined by considering the following options:

• MRI Fistulogram: This is a highly effective diagnostic tool for evaluating perianal fistulas, as it provides detailed images of the fistula tract and surrounding tissues 2, 3, 4, 5.
• CT: While CT scans can be used to diagnose perianal fistulas, they are not as effective as MRI in evaluating the complexity of the fistula and surrounding tissues 4.
• Colonoscopy: This procedure is useful for evaluating the colon and rectum, but it may not provide detailed information about the fistula tract or surrounding tissues.
• Barium Enema: This test is not typically used to diagnose perianal fistulas, as it does not provide detailed images of the fistula tract or surrounding tissues.
• CT Enteroclysis: This test is used to evaluate the small intestine, but it is not typically used to diagnose perianal fistulas.

Advantages of MRI Fistulogram

The MRI fistulogram has several advantages over other diagnostic options, including:

• High accuracy: MRI fistulogram has been shown to be highly accurate in diagnosing perianal fistulas and evaluating their complexity 2, 3, 4.
• Detailed images: MRI provides detailed images of the fistula tract and surrounding tissues, which can help guide surgical treatment 3, 5.
• Non-invasive: MRI is a non-invasive procedure, which reduces the risk of complications and makes it a safer option for patients.

Conclusion is not allowed, so the response will be ended here with the last point.

• Clinical indications: MRI fistulogram is indicated for patients with suspected perianal fistulas, particularly those with complex or recurrent fistulas, and for patients who require surgical treatment 3, 5.