My sister's perianal fistula - surgery or leave alone

The MRI report is as follows. Our cousin who is a doctor recommends no surgery at this time, especially since it has a "possible" internal opening. However another doctor (a general surgeon) is recommending it. I would love to know this community's opinion please:

"A thin linear T2/STIR hyperintense tract noted in the right perianal region in paramedian location. it shows an approximate external opening at 10 o'clock position in right perianal region. The tract is seen to traverse superiorly and anteriorly and run into the intersphincteric plane with a possible internal opening in the mucosa of anal canal at approximately 5-6 o'clock position. Approximate length of the tract is 1.9 cm"