 The talk is MRI fissiography. So I'll try to simplify this topic as much as I can. And the essence of reporting MRI fissiogram is knowing the pelvic anatomy in great detail and knowing the pathophysiology and how the perianal fissulas may behave. Why we need to do MRI? Why not CT fissiogram and other stuffs? All we know is it's non-invasive, no radiation involved, multi-planar capabilities are there. But the best thing why we do MRI is because it gives very good soft tissue contrast and spatial resolution. And with this we get a detailed knowledge of relevant pelvic anatomy. We can see sphincters and fissulas directly and thereby we can classify the fissulas accurately and we can know where the fissula is, where the tract is, what is the exact length, where all it is extending, where is the internal opening, whether it is active or not, what are the branches, whether any ramifications are there or associated abscesses there or not. So coming to perianal anatomy, the anal canal is the structure between internal sphincters, external sphincters on either side. And it is extending from the level of the levator NI to the level of the anal verge. Internal sphincter is nothing but extension of the inner circular muscle of the rectum. It extends down below the levator NI and then forms the internal sphincter. External sphincter is nothing, but it is like condensation of levator NI. It condenses to form purectilis somewhere here and extends down as the external sphincter. And in between these two sphincters is the inter-sphincteric space, which is, I would say, the fulcrum of reporting of MRI physiography. And by the sides, there are ischial anal and ischurectal spaces. So this is the drawing which I will be using to just simplify things further and having a better visual impact. So how do the sphincters look like? This is a T1-wetted image. This is a T2-wetted image. So the internal sphincters are gray, are hypo-intense on T1-wetted images and a bit hyper-intense on T2-FS sequence. Howsoever, external sphincters, they remain hypo-intense on both T1 and T2-wetted fat saturated sequence. And as we can see, this is the internal sphincter and external sphincter. And as we can see, the hyper-intensity in between these two sphincters is the inter-sphincteric space, which consists of fat, areola tissue, by and large we need to understand this space is formed by fat. So if you identify the fat, then you can identify what you are dealing with and where the tract is. So why I call inter-sphincteric space as the fulcrum of reporting? At times the lesions are large and we don't know what we are dealing with. So come back to the inter-sphincteric space, identify on T1 non-fat-sat sequences and then maybe it will direct you better. And as we can see that this fat is getting suppressed on a T2-FS sequence between the internal and external sphincters. This is by the side is the issue NL fat. And there is a differential pattern of enhancement between internal sphincter and external sphincter. So external sphincter since it is condensation of levator Ni and then puborectalis and then forming the external sphincter. So it's basically a muscular structure. So it does not have that much of blood supply to enhance intensely on contrast. However, we see that this is the internal sphincter and it shows relatively more enhancement as compared to the external sphincter on contrast. And this is a coronal image and coronal images are equally important as actual images. And we can see that the internal sphincter is enhancing throughout from the rectum. We go down down and then entire internal sphincter is enhancing. However, external sphincter is condensation of the levator Ni extends down and there is not much of enhancement in the external sphincter. So again, this diagram depicts the condensation of the levator Ni to puborectalis. And as we go down, we see that this is getting condensed and forming the external sphincter. So levator Ni is an important muscle and it should be seen best, should be assessed on coronal or a sagittal vetted images because of the extension of the tract, whether it is extending into supra-levated area or not is important for the surgeons to know. What is a perianal fistula? Perianal fistula is an abnormal connection between the epithelialized surface of the anal canal and then towards the skin. If we do not see any of these opening clearly, then it may be a sinus also, but at times we don't see internal or external opening. So primary cause of perianal fistula is basically 90% of the times. It's a primary cause of perianal fistula which consists of infection of the anal gland. It gets into some sort of obstruction. There is impairment of the drainage, leads to an abscess and then it ruptures and it will traverse into whichever space it finds. And usually the space which is in proximity is the inter-swing trick space. It goes to the inter-swing trick space and then again it can traverse into various directions. Or it may not go into inter-swing trick space, it may traverse in like a trans-swing trick and go into a extra-swing trick course. 10% of the causes of perianal fistula may be a Crohn's disease like how Dr. Mitusha was talking about. Maveticulitis, pelvic infection, tuberculosis, trauma say like a birth trauma, anorectal cancer or a radiation therapy involved. The usually perianal fistulas are more commonly affecting male population of 20 to 60 years of age group. Inter-swing trick tracks are more common in occurrence compared to extra-swing trick and which are more common as compared to trans-swing trick tracks. Usually tracks are unilateral but we see all the combinations. Bilaterality is also seen and association with side branches and abscess is also very common and various permutations and combinations can occur. I'll show you some of the examples. So how do we do MRI officiography? So try to keep a marker, even hyper-intense marker at the site of the discharge. If patient is saying that I had discharged from here, then try to keep a marker over there because it will guide you in knowing the track properly. Then axial oblique and coronal oblique images are taken orthogonal and parallel to the anal canal. So first of all, we'll take a sagittal view of the patient and then along perpendicular to the anal canal and oblique coronal to the anal canal, the images are taken. Sequences taken are axial T1, axial T2. See, if we see here, we have included two of the sequences without fat saturation. Although the fistulas are best seen on fat saturated images, we do not start just acquiring fat set sequences and out. No, because we have to understand what is happening in the fat and we need to know the intrasfintric fat very well, where it is. So axial T1, axial T2, axial T2 fat saturated sequence, coronal stir. So sometimes the fistula is best seen on a stir. So we are including one stir, which is a coronal stir and then a post-contrast weighted image. So we acquire actually a 3D post-contrast so that the image can be reconstructed in the desired plane and a coronal T2 if required and diffusion weighted images is optional. So basically initially the classification which was given by the surgeons was a Park's classification, which did not had the radiological inputs into it. So after MRI coming into picture, St. James classification was given by actually radiologists. So basically all these gradings are designed based on the location of the fistula, what is the location, the extent and associated complication. The highest grading is like grade five in which the classification is based on supra-levator extent. So a supra-levator extent, even if it is not present, you have to write down as a pertinent negative finding in your report, no supra-levator extension noted, no ramifications noted, no obvious abscess noted in the present scan. So these three things, because these are there, which surgeons are looking for should be included in a report. Don't describe the tract and out. No, you have to write these things. Many times we see like a permutation in combination. So giving a grading does not suffice to the questions of the clinician. So we have to follow this anal clock and where the anterior is like 12 o'clock position, posterior is six o'clock position, three o'clock is on the left and nine o'clock is on the right side. We all know, but the report has to go with this o'clock position, like where the tract is, what all o'clock position it is traversing, where is the internal opening and how high and below it is from the anal words and what is happening to the supra-levator compartment. So how do fishelars look? So fishelars usually they are hypo or iso intense on T1, basically not seen, not appreciated well on T1, but sometimes if they have blood, like because of postoperative status or something, they may appear bright on T1. So they are best seen on T2 weighted images and stir images and basically like a T2 fact saturated images. So wherein we are suppressing the fat and highlighting the fluid. So best seen on T2 weighted sequence or a T2 weighted FS or a stir sequence. They show peripheral enhancement on contrast administration, usually most of them because by the, usually when we are doing a scan, the tract is like a active tract and the shapes are like, it may be linear curve linear horseshoe and abscess also are seen at times and which may show peripheral enhancement and then a diffusion restricted weighted restriction on a diffusion weighted sequence. So from the simpler ones to the complex when I have few examples. So here we see that it's, there's a bright spot in the six o'clock position and we see that it is in the inter-sphinctric space. There's some enhancement on contrast and then it is seen in the inter-sphinctric space and extending down. So it's like a simple inter-sphinctric fistula. There's no associated ramification, no abscess whatsoever. So again, here we see that there are two T2 hyper intense and enhancing tracts but again they are inter-sphinctric space. So how do we know it is inter-sphinctric space because internal sphincter is enhancing, external is not enhancing and it is lying between the two. If you want to confirm, we can see here that it is lying in the fact which is suppressed on fat side sequence or we can again go back to our T2 weighted sequences and confirm or T1 where the region is located. So bilateral inter-sphinctric fistulas. So this diagram is basically that green ring is the internal sphincter and the pink ring outside is the external sphincter and this is the location where it is located. Here we see a complex appearing image but we have bilateral internal inter-sphinctric fistulas and sort of peripheral enhancing area in the inter-sphinctric space itself and again it is trying to extend down but this is an example to show you inter-sphinctric fistula within inter-sphinctric abscess. So it's kind of a grade two as per the St. James classification. Again enlarged or dilated inter-sphinctric space or I would say inter-sphinctric tracks with peripheral enhancement and it's bilateral. You can see that it is like extending from kind of the levator and I to the anal verge. Posteriorly they are merging together and then trying to extend out. So basically inter-sphinctric fistulas are biologically with abscesses. So here this example is basically to emphasize on the fat content of the inter-sphinctric space. We see the T1 hypo intensity abutting the internal sphincter, external sphincter and but then obliterating the fat at this location. The fat on the opposite side is nice and bright. So it's a inter-sphinctric fistula and abscess but in association with that sometimes you can see a perianal abscess and there may be no communication with the two. So here we see that there's a extra sphincter tract. This is the internal sphincter, external sphincter and then this is the extra sphincter tract coming trying to come down with peripheral enhancement. And we can see that there are two internal bright spots. At times you may not see them to be like communicating throughout. It may be only like a bright spot which may enhance, which may not enhance and it can be like a presumed internal opening at six o'clock position and 12 o'clock position. So there are various other fistula. So right side we have inter-sphinctric fistula tracking outside into the extra sphincter space and on the opposite side also we have another tract like a extra sphincter fistula. So these are like another examples of only extra sphincter tract. Here you see this is the internal sphincter, external sphincter like we see this is the anal canal and there are the diseases outside the anal canal. So basically these are all extra sphincter tracts. These may be extra sphincter perianal sinuses. We can't demonstrate the internal opening but then this question will remain whether there is internal opening or not. So we have to see carefully and we may not be able to demonstrate all the time. Here we see that there are multiple tracts in extra sphincter location again and with a lot of ramifications it's like difficult to show in one picture where all they are like arising from an extending. So extra sphincter into multiple ramifications. So here in this example, we can show that there's a perianal abscess, peripheral enhancing, a lot of perianal fat stranding but here we can appreciate that there is a suspicious opening, internal opening in this location. And so it becomes a extra sphincter tract again with internal opening. So this is actually a very common picture which we see extra sphincter tract. Then ramification it can go anywhere cranially and there is also some sort of abscess formation. So again, an example of that. So here we see that the extra sphincter abscess has called actually causing significant involvement of the internal and external sphincters both and there is restriction on diffusion with images. So extra sphincter abscess. With sphincter destruction. Here we see that there is a hyper intense tract from one o'clock position extending anteriorly, traversing through both the sphincters, enhancing on contrast. So this is a example of a trans sphincter tract, only trans sphincter tract perianal fistula. But here we see that there is a trans sphincter tract here which is enhancing hyper intense on T2 with pedifural enhancement. So it's a trans sphincter tract with an abscess formation. Another example, a trans sphincter tract with a extra sphincter, trans extra sphincter tract like both are there. So this is also to show the complexity of this situation and at times we find it difficult how to describe. But then we have to describe like whatever we see combining two, three things together and then what you cannot combine then describing them separately. So this is an example to show that perianal like extra sphincter abscess has extending up. This is the levator Ni which shows on the opposite side bright signal on T2 weighted images and then it is inflamed and the abscess is seen extending into the supra levator space indenting the base of the bladder. So trans sphincter extra like on the right side it is trans sphincter extra sphincter the left side it is extra sphincter extending into the pelvic space. Sometimes we see that there is a abscess or a tract in the pelvic region and there is a supra levator collection also. So here we see this is the rectum lower rectum and there's a large collection in the perirectal space but how so ever we could not demonstrate the communication with the two. So this invariably is a part of the perianal abscess which has extended cranially but then we can't demonstrate so it has to be described to different paragraphs and the communication could not be demonstrated in the present scan. It would be additional information which we can give and a follow up maybe on follow up you can demonstrate because in this case we could demonstrate on a follow up. So what is important to know is in perianal fish or whether it is communicating to the other structures like here we see that there's a ill-defined tract extending from the anal vertebrae extending anteriorly and it is enhancing on contrast. So basically it is a small transferring trig tract which has got communication with the vaginal cavity and this is a case or case of Crohn's. All we could appreciate was this thin tract like few millimeters tract with peripheral enhancement only appreciated on a contrast scan and that also with like a mip images when we performed. So here we see that there's a transferring trig tract which is extending anteriorly and it is extending into the urethral region. So transferring trig tract with the urethral extension. Sometimes we see only tract in the posterior aspect without any communication with the perianal region. So a perianal sinus and the upper case is only a sinus. The lower case is a sinus with an abscess formation and sometimes the perianal disease can be quite extensive. It can extend even above the levator and I and there may be no communication with the perianal region and which is what they want to know. So here we see that there's a large H2O and L abscess abutting the external center but whatsoever there is no communication. So it's like a extensive perianal or a H2O and L H2O rectal abscess. So here we had a case where in the fistula was very small. It's like a transferring trig fistula which had a kind of a collection in the perianal region but when we went up and like traced the lesion further we saw that there was an abscess which was being formed in the right obturator internus and patient was in septic shock. So basically fistula was very small but then the repercussions were great. Sometimes we just see only an enhancement of the like relatively extra enhancement in the external sphincter or in the internal sphincter. That time you need to understand is there any past history of any surgery? Sometimes post surgical changes also can enhance. So that is what we need to know in detail. And sometimes it may be just an inflammation. It may be like in future it may form an abscess. So a clinical input and a follow-up study. So a reporting checklist basically what type of fistula you are seeing and what are the permutations and combinations? Like basically what all side branches are there or not where they are going at what o'clock position you can actually describe it is going it's like curvilinear horseshoe from this o'clock position to that o'clock position in various other stuff. Then exact shape length width. We can measure the tract like how many millimeters where it is maximum. And we have to give a report with respect to the NL clock and with respect to the distances from the NL watch. And if there is any external opening and then the site of the external opening. So and the condition of the internal and external sphincters. Supra elevator extension is there or not and involvement of any other organ like involvement of vagina and urethra or any other structure. MRI is a valuable tool for enabling us to know these tracks to form a kind of a roadmap and identify associated complications and it will help surgeons for the surgical planning and a favorable outcome. Thank you.