What type of MRI should I order for a patient with rectal pressure after proctectomy (surgical removal of the rectum) 20 years ago?

MRI Protocol for Rectal Pressure After Proctectomy

For a patient with rectal pressure after proctectomy 20 years ago, an MRI pelvis without and with IV contrast is the most appropriate imaging study to evaluate potential complications and identify the cause of symptoms.1

Rationale for MRI Selection

MRI offers several advantages for post-proctectomy evaluation:

• Superior soft-tissue contrast resolution compared to CT, making it ideal for evaluating clinically suspected complications such as anastomotic issues, fistulas, or sinus tracts 1
• Ability to visualize structural changes after surgery and implanted synthetic materials 1
• Can detect complications that may cause rectal pressure, including:
  • Fistulas (88% sensitivity, 100% specificity) 1
  • Small-bowel and inlet strictures 1
  • Sinus tracts
  • Abscesses
  • Recurrent disease

Recommended MRI Protocol

Essential Components:

1. MRI pelvis without and with IV gadolinium contrast

   • IV contrast significantly enhances diagnostic confidence for post-surgical complications 1
   • Active inflammation in fistulous tracts will enhance avidly with contrast
   • Abscesses will show characteristic rim-like enhancement 1

2. Technical Considerations:

   • Field of view should be appropriately sized to visualize the entire pelvis 1
   • Planes of imaging should be orthogonal to the area of interest 1
   • Include diffusion-weighted sequences to increase conspicuity of fistulae and discriminate between inflammatory mass and abscess (100% sensitivity, 90% specificity) 1

Additional Considerations

When to Consider Dynamic Imaging

If there are concerns about pelvic floor dysfunction in addition to rectal pressure:

• MR defecography may be appropriate if there is suspicion of persistent or recurrent prolapse 1
• Dynamic pelvic floor MRI with maneuvers can help evaluate functional abnormalities 1

Potential Pitfalls

• Scar tissue may appear similar to implanted materials and can confound evaluation 1
• Collapsed tracts without fluid may be difficult to see on T2-weighted sequences alone, highlighting the importance of IV contrast 1
• Standard MRI without dynamic components may miss functional abnormalities if pelvic floor dysfunction is present 1

Alternative Imaging Options

• CT pelvis with IV contrast could be considered as an alternative if MRI is contraindicated 1
• However, CT has inferior soft tissue contrast compared to MRI for this indication 1

Conclusion

MRI pelvis without and with IV contrast provides the most comprehensive evaluation for a patient with rectal pressure after proctectomy, offering superior soft tissue contrast and the ability to detect various potential complications that may be causing the patient's symptoms.