MR IMAGING IN PERIANAL FISTULAS: A COMPARATIVE STUDY OF 25 PATIENTS

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1 wjpmr, 2016,2(5), SJIF Impact Factor: Research Article Joshi et al. WORLD JOURNAL OF PHARMACEUTICAL ISSN AND MEDICAL RESEARCH WJPMR MR IMAGING IN PERIANAL FISTULAS: A COMPARATIVE STUDY OF 25 PATIENTS Dr. Anagha Joshi, Dr. Maunil Bhuta, Dr. Sukhada Kulkarni*, Dr. Sukhvinder Singh, Dr. Tanvi Modi Lokmanya Tilak Municipal Hospital and Medical College, Sion, Mumbai *Corresponding Author: Dr. Sukhada Kulkarni Lokmanya Tilak Municipal Hospital and Medical College, Sion, Mumbai Article Received on 05/08/2016 Article Revised on 26/08/2016 Article Accepted on 15/09/2016 ABSTRACT Perianal fistulas are prevalent in % [1] of the population and are commonly associated with discomfort and morbidity to the patient. Surgical treatment is the only modality of management of fistulas with the pitfall of high rate of recurrence. MR fistulography has been demonstrated to be superior to conventional methods such as endoanal USG and fistulography in delineating the tracts and identifying complications such as branching or collections, thus helping surgical management of these patients thereby reducing rate of recurrence. KEYWORDS: Fistula, MR Fistulography, recurrence. INTRODUCTION Reed, pipe or flute in latin called as Fistula. In simple terms, a fistula can be described as a chronic granulating track connecting two epithelium lined surfaces, either cutaneous or mucosal. The course of perianal fistula is from the anal canal to the perianal skin or perineum. The disease although appears to be a simple medical condition, the disease itself as well as its improper surgical management can cause significant morbidity. That is why it is of very much importance to gather as much information available about the disease as possible before the surgery, otherwise treatment failure or recurrences are certain. In the past, prior to radiological imaging, the management of the patient included clinical examination of the perianal region and the per-rectal examination inan attempt to find the internal opening. Simply laying open the fistulous tract i.e fistulotomy was used as treatment modality. Seton technique [2], described in the Ayurveda by Sushruta (termed as Ksharsutra ) was another method used. However there was significant number of recurrences. Few of the causes for the recurrence were incomplete removal of the fistulous tract, persistent infection / inflammation and associated inflammatory disease of the rectum and colon. The review of the diagnostic methods and treatment planning was very important with the increasing knowledge of treatment failure in most patients. Hence considering the treatment failure, radiological imaging was introduced in the management of perianal fistulas. In the initial stages of use of imaging for the diagnosis and management of fistulas, fistulography [3] and at times barium enemas were used. In most cases, these modalities could not provide all the information that was required and there were recurrences. The advent of MRI, with its superior soft-tissue contrast resolution and multiplanar imaging capabilities, brought a dramatic change in imaging of perianal fistulas in terms of identifying exact size, site of fistulous tracts, branching patterns and associated soft tissue changes. Surgical procedures after MRI have showed significantly better results. Aims and Objectives To evaluate the accuracy of magnetic resonance (MR) imaging for detecting simple perianal fistulas by using a quadrature phased-array coil. To know the additional clinical value of preoperative MR imaging in case of the complicated perianal fistulas. MATERIALS AND METHODS A prospective study was done of 25 patients with clinical diagnosis of perianal fistula between November 2010 and August Patients who presented to the surgery OPD complaining of pain/perianal pus discharge and were clinically suspected / diagnosed to have perianal fistulas were referred to our department and enrolled for study with MRI examination. Patient was examined prior to the MRI for number and location of external openings and the findings were recorded. Patients having general contraindications for MRI were excluded from the study. 253

2 The studies were performed on 3.0 Tesla Philips Achieva system (32 Channel) MRI scanner using a quadrature phased array coil (body coil). The study included- 1. Survey or localizer sequence- for planning. 2. T1 TSE Axial 3. T2 TSE Axial 4. T2 SPAIR Axial 5. T2 SPAIR Sagittal 6. T2 SPAIR Coronal Thin section T2 SPAIR Axial sequence was used in some cases for better visualisation of the fistulous tract or the internal opening in doubtful cases. STIR and VISTA (3D T2 TSE sequence) were used in some patients for comparison. Gadolinium enhanced MRI was not performed. The evaluation with the unenhanced T2 fat saturated images was satisfactory and the need Gadolinium-enhanced MRI was not felt in any case. OBSERVATIONS AND RESULTS Out of the 25 patients, MRI correctly identified the fistulous tract in all 25 patients, including the secondary tracts. The most common presenting complaint in our cases was pain and perianal pus discharge with duration of symptoms varying from 3 months- 2 years. 15 patients presented for the first time while 10 presented with recurrent fistulas. 24 out of the 25 patients in our study, i.e. 95% of the patients were males. Most common age group years i.e. middle aged population. Most common type of fistula in our study was transsphincteric type, which was found in 19 of the 25 patients, constituting 76% of the total cases. Types of Fistulas in our study. Type Number of patients Intersphincteric 2 Transsphincteric 19 Suprasphincteric 1 Extrasphincteric 2 Others(Low type) 1 MRI showed additional findings such as a branching tract or an inflammatory collection or both were noted in 17 out of the 25 cases in our study (68%). Only 8 out of 25 patients (32%) had simple nonbranching tracts, either single or multiple, without associated secondary or branching tracts or inflammatory collections. The most common site of internal opening in our study was midline posteriorly i.e at 6 o clock, seen in 14 (56 %) patients. We found the Goodsall s rule to be true in all the cases(most fistulous openings were located posterior to midline) As 68 % patients had associated complications, MRI was very important in management of these patients in our study; as without a MRI these findings would have been easily missed causing persistent disease and recurrence. Figures. Figure 1. Diagrammatic representation demonstrating the various types of perianal fistulas as described in the Parks classification. A- Intersphincteric. B- Trans-sphincteric. C- Suprasphincteric. D- Extrasphincteric. The external sphincter is the keystone of the Parks classification. 254

3 Figure 2. Axial T2 SPAIR image demonstrating transsphincteric fistula (arrow) with the fistulous tract seen traversing through both the internal and external sphincters to open at 6 o clock position. Figure 3. Axial T2 SPAIR image demonstrating an intersphincteric fistulous tract (arrow). 255

4 Figure 4. Axial T2 SPAIR image showing a collection (arrow) in right gluteal region tracking along the gluteus maximus muscle. It is impossible with conventional imaging to identify findings such as these. Figure 5. Axial T2 SPAIR image showing small collections (arrows) intersphincteric plane and extrasphincteric plane posteriorly. 256

5 Figure 6. Sagittal T2 SPAIR image showing a posterior transsphincteric fistula (arrow) which continues as another tract till just below the levator ani muscles. Figure 7. Coronal T2 SPAIR image showing a transphincteric fistula (arrow) coursing just lateral to the external anal sphincter. 257

6 Figure 8. Sagittal T2 SPAIR image showing an Extrasphincteric fistula (arrow). DISCUSSION The predominant classification system is that described by Parks et al in 1976 [4], which classifies the fistula according to the primary tract s relation to the external and internal sphincters and the levator ani muscle. There are the following four categories. Parks Classification. I. Intersphincteric II. Trans-sphincteric III. Suprasphincteric IV. Extrasphincteric Intersphincteric fistulas are in the intersphincteric space only and do not cross the external sphincter. The track runs along the longitudinal muscle layer between the internal and external sphincters and may reach the perianal skin through or medial to the subcutaneous external sphincter. In Transsphincteric fistulas, the track passes from the intersphincteric space through the external sphincter into the ischiorectal fossa. In Suprasphincteric fistulas, the track progresses upward into the intersphincteric space, passes over the top of the puborectalis muscle, then descends through the levator plate to the ischiorectal fossa and finally to the skin. In Extrasphincteric fistulas, the track passes from the perineal skin through the ischiorectal fossa and levator muscles then into the rectum. The St. James University Hospital Classification [5] is another widely used classification system which classifies the perianal fistulas as follows. Grade 1- Simple linear intersphincteric fistula Grade 2- Intersphincteric with abscess or secondary track Grade 3- Trans-sphincteric Grade 4-Transsphincteric with abscess or secondary track in ischiorectal or ischioanal fossa Grade 5- Supralevator and Translevator. High and low type fistulas are classified on the basis of the level where the primary tract transverses the external sphincter or levator muscle and it determines how much of the sphincter mechanism is encompassed by the fistula: in high type this level is above the level of the dentate line. The internal opening of an anal fistula is usually situated at the level of the dentate line. As per Goodsall s rule when the external opening(s) is situated in the posterior half of the perianal area, the internal opening is usually located in the posterior midline, but when the external opening is anterior, the internal opening is usually situated radially in the same direction. Pain and perianal discharging sinus was the most common presenting complaint in our group of patients. This was found to correlate with epidemiological studies conducted elsewhere. [6] 3 month to approximately 2 years was the symptom duration in our study, with 60% patients presenting for the first time. Middle aged individuals were mainly found to have perianal fistulas with the most common age group of patients in our study was years, followed by 11 to 30 years. [7] 258

7 The most common type of fistula in our study was found to be trans-sphincteric fistula in 19 cases (76 %), followed by intersphincteric type in 2 cases (8 %). High types of fistulas i.e Suprasphincteric and extrasphincteric were present in 3 cases each (12%). However as per most of the published studies so far intersphincteric type of the fistula is the commonest type of fistula, trans-sphincteric type [4] is the next one. A branching tract or an inflammatory collection or both were additional findings seen in 17 out of the 25 patients in our study (68%) with the help of MRI. Of the 25 patients, MRI correctly identified the fistulous tract in all 25 patients. All the secondary tracts were also correctly identified. This is better than the previously reported [8, 9, 10] sensitivity. For visualizing normal anatomy of the internal and external anal sphincters we found the non-fat-suppressed T1 and T2 weighted TSE sequences, either STIR or SPAIR to be better. The fluid containing fistulous tracts, granulation tissue, and inflammatory collections are better demonstrated by the fat suppressed sequences. We found no need to perform a contrast enhanced MRI. The excellent resolution of T2 weighted fat suppressed images (T2-SPAIR) was adequate for demonstrating all the relevant details. The internal opening of the fistulas and the exact location of tract is most easily visualised on axial images. Coronal images are better for depicting the levator ani plane, thereby allowing the differentiation of supra-levator from infra-levator disease. A combination of axial and either coronal or sagittal series provides all the necessary information in most patients. However in complex fistulas all three planes need to be carefully evaluated with addition of thinner section images of selected regions if required. In general, the study protocol for optimal imaging on a 3T MRI scanner can be fairly short and time saving without any compromise on the usefulness of the study. The time required for the scan using these sequences was approximately min. It demonstrated the pathology quite well and consumed very less time, therefore had improved patient cooperation as well as patient throughput in as busy department. CONCLUSION MRI is very accurate in diagnosing the fistulous tract, its course, branches and associated inflammatory collections if any. A significant amount of relevant information regarding exact disease burden, deep seated and occult inflammation, tract ramifications can only be accurately demonstrated by MRI. No other imaging modality has been found to be as accurate as an MRI examination, with additional advantage of being non-invasive investigation without any radiation hazard. Failure to identify secondary tracts, branching pattern, collections is the most important cause of complications and persistence of disease and recurrence. [11] To summarize, MRI is the imaging modality of choice due to its excellent soft tissue depiction in perianal region which creates a virtual image for surgeons regarding the tracts and ramifications for effective surgery and minimizing chances of recurrence. REFERENCES 1. Kim SY, Kim MJ, Chung JJ, Lee JT, Yoo HS. Abdominal tuberculous lymphadenopathy: MR imaging findings. Abdominal imaging., 2000 Nov- Dec; 25(6): Kuijpers JH, Schulpen T, Buyck B. [The seton method for the treatment of perianal fistula located outside of the sphincter]. Nederlands tijdschrift voor geneeskunde., 1985 May 18; 129(20): Weisman RI, Orsay CP, Pearl RK, Abcarian H. The role of fistulography in fistula-in-ano. Report of five cases. Diseases of the colon and rectum., 1991 Feb; 34(2): Andronikou S, Welman CJ, Kader E. 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