Differential Diagnosis for MRI Findings
The MRI findings of an abscess within the levator plate with a descending track till the midline at 6 o'clock position, without any external or internal opening, suggest a complex anorectal condition. Here's a categorized differential diagnosis:
Single most likely diagnosis
- Pelvirectal fistula: This is the most likely diagnosis given the location of the abscess within the levator plate and the descending track. A pelvirectal fistula is a type of fistula that connects the rectum to the pelvic cavity, which can present with such findings on MRI.
Other Likely diagnoses
- Submucous fistula: Although less likely than a pelvirectal fistula, a submucous fistula could potentially present with similar MRI findings, especially if the fistula track is complex and not fully visualized.
- Low perianal fistula: This could be considered if the track's descent to the midline at the 6 o'clock position is interpreted as potentially connecting to the perianal skin, although the absence of an external opening makes this less likely.
Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Rectal or sigmoid cancer with fistula formation: Although rare and less likely, a malignant process could potentially cause similar findings, especially if there's a complex fistula formation. Missing this diagnosis could have severe consequences.
- Inflammatory bowel disease (IBD) with fistula: Conditions like Crohn's disease can cause complex fistulas, including those that might not have obvious external or internal openings on initial evaluation.
Rare diagnoses
- Subcutaneous fistula: This would be an unusual presentation given the location of the abscess and the track's description, making it less likely.
- Congenital conditions (e.g., rectovaginal or rectourethral fistula): These are rare and typically present early in life, but could be considered in the differential diagnosis of complex anorectal fistulas, especially if other signs or symptoms suggest a congenital anomaly.