Magnetic resonance imaging of fistula-in-ano: STIR or SPIR?

Can Short Tau Inversion Recovery (STIR) Imaging Be Used as a Stand-Alone Sequence To Assess a Perianal Fistulous Tract on MRI? A Retrospective Cohort Study Comparing STIR and T1-Post Contrast Imaging

INTRODUCTION

Perianal fistulas demand precise preoperative assessment for optimal surgical outcomes. MRI, using Short Tau Inversion Recovery (STIR) and T1-post contrast sequences, plays a crucial role in this evaluation.This retrospective cohort study compared STIR imaging's diagnostic efficacy with T1-post contrast sequences in identifying perianal fistulous tracts. The study investigated whether STIR imaging could serve as the sole diagnostic sequence, simplifying clinical practice.

METHODS

In a tertiary care hospital, 100 patients underwent pelvic MRI for suspected perianal fistulas. Radiologists independently evaluated STIR and T1-post contrast sequences for internal openings, tract extent, distinction, abscess presence, and tract type. Sensitivity, specificity, area under the curve (AUC), and Cohen's kappa analysis were used for diagnostic assessment.

RESULTS

STIR imaging showed notable sensitivity (79.8-97.9%) and specificity (100%) for identifying internal openings and tracts. Combined with T1-post contrast, diagnostic accuracy improved significantly, with near-perfect AUC values. Kappa values indicated moderate to substantial agreement between radiological assessments and clinical diagnosis. The combined sequences achieved 100% sensitivity and specificity for tract visualization.

CONCLUSION

STIR imaging presents promise as a singular diagnostic tool for perianal fistulas, especially when combined with T1-post contrast sequences. While offering potential clinical diagnosis simplifications, further studies are warranted to validate its utility and ensure comprehensive diagnostic accuracy.

Diagnostic Accuracy of Short Tau Inversion Recovery as a Limited Protocol for Diagnosing Perianal Fistula

Introduction

Perianal fistula refers to abnormal communication between perianal skin and anal canal. Magnetic resonance imaging (MRI) and endoanal ultrasound have been used in the evaluation of perianal fistula. Endoanal ultrasound is a cost-effective but operator-dependent technique. MRI provides accurate details regarding anal canal anatomy and effectively identifies the fistulae. For evidence-based care, a cost-effective and an accurate imaging modality is required in a developing country. Therefore, the aim of this study was to determine the diagnostic accuracy of short tau inversion recovery (STIR) as a limited protocol MRI pelvis in diagnosing perianal fistula taking surgical findings as the gold standard.

Materials and methods

A retrospective review of MRI pelvis from 1^st February 2018 to 1^st July 2018 was undertaken. Patients of any age or gender suspected to have perianal fistula were included. One radiologist interpreted the complete MRI pelvis and the other radiologist only viewed axial and coronal STIR sequences as a limited protocol. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy of axial and coronal STIR sequence were calculated taking surgical findings as the gold standard.

Results

In total, 150 patients were included in this study. The mean age of the patients was 43.20 ± 13.75 years. In total, 122 (81.3%) were males and 28 (18.7%) were females. Using STIR as a limited protocol, fistulae were found in 125 (83.3%) patients, whereas on surgery, the fistulae were found in 119 (79.3%) patients. Sensitivity, specificity, PPV, NPV, and diagnostic accuracy of STIR as limited protocol MRI pelvis in diagnosing perianal fistulae was found to be 96.6%, 67.7%, 92.0%, 84.0%, and 90.6%, respectively, taking surgical findings as the gold standard.

Conclusion

STIR has high sensitivity and diagnostic accuracy in diagnosing in the perianal fistula. Using STIR as a limited protocol in a developing country can help improving patient care by accurately diagnosing perianal fistulae. Moreover, it is recommended that further studies for identifying internal opening on STIR should also be carried out to improve patient care.

The treatment of anal fistula: second ACPGBI Position Statement - 2018

It is over 10 years since the first ACPGBI Position Statement on the management of anal fistula was published in 2007. This second edition is the result of scrutiny of the literature published during this time; it updates the original Position Statement and reviews the published evidence surrounding treatments for anal fistula that have been developed since the original publication.

The comparison of CT fistulography and MR imaging of perianal fistulae with surgical findings: a case-control study

PURPOSE

The purpose of this study was to evaluate the diagnostic efficacies of CT fistulography and MRI, in the diagnostic work-up of perianal fistula patients.

MATERIALS AND METHODS

All 41 patients who were included in the study (36 males and 5 females, with an average age of 41 years) underwent CT fistulography and MRI examinations prior to surgery. The fistula characteristics obtained from these examinations were compared with the surgical findings. The comparative results were evaluated by means of the Kappa analysis method.

RESULTS

CT fistulography predicted the correct perianal fistula classification in 30 (73.1%) of the 41 patients, whereas MRI correctly defined fistula classification in 38 (92.7%) of these patients (the K values were 0.621 and 0.896, respectively; with p < 0.001). CT fistulography depicted 29 secondary extensions in 16 patients, whereas MR imaging revealed 28 secondary extensions in 15 patients. A substantial agreement was found between surgical findings and two modalities (K value was 0.789 and 0.793 for CT fistulography and MRI, respectively, with a p value < 0.001). In terms of locations of internal openings, CT fistulography was able to detect the locations in 28 patients (68.2%), whereas MRI was more successful in this aspect, with a number of 35 patients (85.3%). Granulation tissues, inflammation and edema around the fistula, abscesses, and fistular wall fibrosis were also evaluated.

CONCLUSION

CT fistulography and MRI have different advantages in the diagnosis of perianal fistulas. A good command of knowledge concerning the issue may be a key factor in modality decision.

MR imaging of perianal fistulas in Crohn's disease: sensitivity and specificity of STIR sequences

INTRODUCTION

Although some studies proved the role of STIR sequences in the evaluation of perianal fistulas in Crohn's Disease (CD), contrast medium is still injected in many institutions since there is not a validated reference MR protocol. Our purpose was to evaluate the role of the STIR sequence in the detection and characterization of perianal fistulae comparing it to the post-contrast T1 sequence and correlating it with rectal examination under anesthesia.

MATERIALS AND METHODS

We retrospectively reviewed all clinical records of 31 CD patients, suspected of having perianal fistulas, who had been submitted to an MR study before and after contrast medium injection and surgical exploration under anesthesia within the same month. Perianal fistulas were classified according to the Parks' criteria. Finally, comparison between STIR and post-contrast T1-weighted fat saturated sequences was done.

RESULTS

29 fistulas were detected in 25 patients who underwent an MR study. There was no significant difference between MR imaging and exploration under anesthesia. For the detection of perianal fistulas of any type, there was a perfect statistical agreement between gadolinium-enhanced and STIR sequences (kappa value = 1).

CONCLUSION

STIR sequences represent a valid alternative to the T1-weighted sequences acquired after the injection of contrast medium, allowing the identification of the primary fistula, any secondary ramification, and complications of the disease.

MRI of perianal fistulas: bridging the radiological-surgical divide

Perianal fistula is a clinical entity with multiple surgical treatment options. Recently, magnetic resonance imaging (MRI) has emerged as an important imaging modality in the management of perianal fistulas. It provides accurate description of the fistula within the anal canal in relation to the sphincter complex and other pelvic floor structures as well as the associated complications such as abscess. By understanding the surgical viewpoint, the appearance of perianal fistulas, associated complications, and post-treatment findings of commonly used surgical interventions can more accurately be interpreted to aid clinicians. The objective of the article is to review MRI indications and findings, radiological versus surgical classification schemes, and surgical treatment options for perianal fistulas.

Whole-heart coronary magnetic resonance angiography at 3.0T using short-TR steady-state free precession, vastly undersampled isotropic projection reconstruction

PURPOSE

To evaluate the feasibility of improving 3.0T steady-state free precession (SSFP) whole-heart coronary magnetic resonance angiography (MRA) using short-TR (repetition time) VIPR (vastly undersampled isotropic projection reconstruction).

MATERIALS AND METHODS

SSFP is highly sensitive to field inhomogeneity. VIPR imaging uses nonselective radiofrequency pulses, allowing short TR and reduced banding artifacts, while achieving isotropic 3D resolution. Coronary artery imaging was performed in nine healthy volunteers using SSFP VIPR. TR was reduced to 3.0 msec with an isotropic spatial resolution of 1.3 x 1.3 x 1.3 mm(3). Image quality, vessel sharpness, and lengths of major coronary arteries were measured. Comparison between SSFP using Cartesian trajectory and SSFP using VIPR trajectory was performed in all volunteers.

RESULTS

Short-TR SSFP VIPR resulted in whole-heart images without any banding artifacts, leading to excellent coronary artery visualization. The average image quality score for VIPR-SSFP was 3.12 +/- 0.42 out of four while that for Cartesian SSFP was 0.92 +/- 0.61. A significant improvement (P < 0.05) in image quality was shown by Wilcoxon comparison. The visualized coronary artery lengths for VIPR-SSFP were: 10.13 +/- 0.79 cm for the left anterior descending artery (LAD), 7.90 +/- 0.91 cm for the left circumflex artery (LCX), 7.50 +/- 1.65 cm for the right coronary artery (RCA), and 1.84 +/- 0.23 cm for the left main artery (LM). The lengths statistics for Cartesian SSFP were 1.57 +/- 2.02 cm, 1.54 +/- 1.93 cm, 0.94 +/- 1.17 cm, 0.46 +/- 0.53 cm, respectively. The image sharpness was also increased from 0.61 +/- 0.13 (mm(-1)) in Cartesian-SSFP to 0.81 +/- 0.11 (mm(-1)) in VIPR-SSFP.

CONCLUSION

With VIPR trajectory the TR is substantially decreased, reducing the sensitivity of SSFP to field inhomogeneity and resulting in whole-heart images without banding artifacts at 3.0T. Image quality improved significantly over Cartesian sampling.

MRI for assessment of anal fistula

Magnetic resonance imaging (MRI) is the best imaging modality for preoperative assessment of patients with anal fistula. MRI helps to accurately demonstrate disease extension and predict prognosis. This in turn helps make therapy decisions and monitor therapy. The pertinent anatomy, fistula classification and MRI findings will be discussed.

Imaging of fistula in ano

Fistula in ano is a common condition that often recurs despite seemingly adequate surgery, usually because of infection that was missed at surgery. It is now increasingly recognized that preoperative imaging can help identify infection that would have otherwise gone unidentified. In particular, magnetic resonance (MR) imaging findings have been shown to influence surgery and markedly diminish the chance of recurrence; thus, preoperative imaging will become increasingly routine in the future. In this article, the authors describe the pathogenesis, classification, and imaging of fistula in ano, with an emphasis on MR imaging. Most important, the authors describe how the radiologist is well placed to answer the surgical riddles that must be solved for treatment to be effective.

Diagnostic accuracy of body coil MRI in describing the characteristics of perianal fistulas

OBJECTIVE

The purpose of this study was to determine the accuracy of synergic body coil MRI using SPIR technique without contrast, in the determination of fistula characteristics in patients with clinically positive signs.

METHOD AND SUBJECTS

This was a case-series prospective study including 29 consecutive patients with clinically suspected fistulas-in-ano. The standard synergic body coil was used and all patients had T2-weighted SPIR sequences. One radiologist, without prior knowledge of the clinical examination, analysed images and noted the presence of the fistula, its classification and the presence and number of any collections or extensions. The surgeon noted the MRI findings and looked for lesions suggested on MRI. The results of the MRI and surgical assessments were then compared. Results of surgical exploration while the surgeon was aware of MRI results were considered as the gold standard of surgical anatomy.

RESULTS

Twenty-three (79.31%) of 29 fistula tracks were seen on MRI which correctly determined the type of all fistulas. In the six cases where the fistula was not seen on MRI, five were low trans-sphincteric and one was rectovaginal. MRI identified 8 of 10 collections.

CONCLUSION

The synergic body coil MRI with SPIR sequencing without endoanal coils had a high accuracy in the diagnosis of high fistulas collections, complex fistulas and extensions.

Fat suppression strategies in enhanced MR imaging of the breast: comparison of SPIR and water excitation sequences

PURPOSE

To compare two fat suppression techniques of spectrally-selective inversion pulse (spectral presaturation with inversion recovery-SPIR) and spectral-spatial excitation pulse of water excitation (WE) for contrast-enhanced MR imaging of the breast.

MATERIALS AND METHODS

Forty women with histologically-proven breast cancer were examined. Both pulse types were applied to postcontrast, axial, three-dimensional field echo sequence. Contrast noise ratios (CNR) of lesion-to-breast parenchyma, lesion-to-fat, and parenchyma-to-fat were determined. Qualitative image analysis using a four-point scale was also performed by two observers.

RESULTS

All the CNR values of obtained with WE techniques were significantly higher than those with SPIR. Qualitative analysis indicated that the WE images were statistically superior for the lesion-to-breast parenchyma contrast while being slightly inferior to the SPIR images for fat suppression homogeneity without statistical significance.

CONCLUSION

Compared to SPIR, the WE technique suppressed the subcutaneous fat signal more potently and improved the contrast of the enhanced breast lesion against the parenchyma and the subcutaneous fat. WE will be a powerful fat suppression strategy for enhanced MR imaging of the breast.

Imaging anal fistula

The management of fistula-in-ano has been based on digital examination and operative findings. MR imaging has shown significant limitations to this approach, particularly in the management of recurrent fistula. The most cost-effective approach may be using a combination of endosonography and MR imaging. Preoperative confirmation of fistula complexity facilitates surgery planning of sphincter saving techniques and prevents sepsis being missed, which has been shown to reduce recurrence. Imaging has a significant role to play in this condition to improve patient outcome.

Unusual sonographic finding in a patient with late recurrence of a perianal fistula

We describe a case of late recurrence of a perianal fistula in a 51-year-old man with a 4.5-year history of recurrent perianal fistulas and abscesses. This was the fourth recurrence he had experienced; at each occurrence, he had undergone various examinations, including sigmoidoscopy, anoscopy, barium enema, fistulography, probe exploration, instillation of hydrogen peroxide, and/or sonography, and he had also undergone surgery. At our examination, transperineal sonography with a portable ultrasound scanner revealed an echogenic linear structure within the fistulous tract. Under endoanal sonographic guidance, surgery was performed, and a tan solid cylindrical structure longer than 2 cm was removed. Histopathologic examination revealed stratified squamous epithelium and soft tissue with substantial fibrosis and mild chronic inflammation, findings consistent with the characteristics of a remnant cast from a previous fistulous tract. Our findings suggest that some patients may benefit from relatively inexpensive sonographic examination with appropriate transducers.

[Comparison of MR-sequence in the diagnosis of anal fistula--the clinical value of 3D flash]

To elevate the clinical value of 3D-FLASH in the diagnosis of anal fistula and compare it with convertioned MR sequence, MR sequences, consisting of spin echo T1WI, turbo invertion recovery magnitude (TIRM), fast low-angle shot image (FLASH), mon-enhancement and enhancement substraction and coronary reconstructing, was conducted in 15 cases suspected of anal fistula. Comparison was made among the three sequences in display rate of internal fistula, external fistula, the branch of fistule connulas. Our results showed that 1 patient had perianal abscess. 24 different anal fistulas were identified in 14 patients, and 10 of them was complicated with perianal abscess and 8 of them with complex multi-branch fistula. The display rate of 3D-FLASH sequence was much higher than those of T1WI and TIRM in all cases. It is concluded that 3D-FLASH sequence is an senstive and time-efficient technique for the diagnosis of anal fistula.

Preoperative MR imaging of anal fistulas: Does it really help the surgeon?

PURPOSE

To evaluate the accuracy of magnetic resonance (MR) imaging with a quadrature phased-array coil for the detection of anal fistulas and to evaluate the additional clinical value of preoperative MR imaging, as compared with surgery alone.

MATERIALS AND METHODS

Fifty-six patients with anal fistulas underwent high-spatial-resolution MR imaging. Twenty-four had a primary fistula; 17, a recurrent fistula; and 15, a fistula associated with Crohn disease. MR imaging findings were withheld from the surgeon until surgery ended and verified, and surgery continued when required.

RESULTS

MR imaging provided important additional information in 12 (21%) of 56 patients. In patients with Crohn disease, the benefit was 40% (six of 15); in patients with recurrent fistulas, 24% (four of 17); and in patients with primary fistulas, 8% (two of 24). The difference between patients with or without Crohn disease and between patients with a simple fistula versus the rest was significant (P <.05). The sensitivity and specificity for detecting fistula tracks were 100% and 86%, respectively; abscesses, 96% and 97%, respectively; horseshoe fistulas, 100% and 100%, respectively; and internal openings, 96% and 90%, respectively.

CONCLUSION

High-spatial-resolution MR imaging is accurate for detecting anal fistulas. It provides important additional information in patients with Crohn disease-related and recurrent anal fistulas and is recommended in their preoperative work-up.

Magnetic resonance imaging of lipoma and liposarcoma: potential of short tau inversion recovery as a technique of fat suppression

The present limited retrospective study was performed to assess MR imaging of lipomatous tumours of the musculoskeletal system and to evaluate the potential of the T2 short tau inversion-recovery (STIR) technique for differentiating lipomas from liposarcomas. Magnetic resonance imaging of 12 patients with lipomatous tumours of the musculoskeletal system (eight benign lipomas, three well-differentiated liposarcomas and one myxoid liposarcoma) were reviewed. Benign lipomas were usually superficial and showed homogeneity on T1- and T2-weighted spin echo sequences. Full suppression at T2 STIR was readily demonstrated. In contrast, the liposarcomas in the present series were all deep-seated. Two well-differentiated liposaromas showed homogeneity at long and short relaxation time (TR) but failed to show complete suppression at T2 STIR. One case of well-differentiated liposarcoma (dedifferentiated liposarcoma) and one of myxoid liposarcoma showed mild and moderate heterogeneity at T1 and T2, respectively, and posed no difficulty in being diagnosed correctly. In conclusion, short and long TR in combination with T2 STIR show promise in differentiating benign from malignant lipomatous tumours of the musculoskeletal system, when taken in combination with the position of the tumour.

How can the assessment of fistula-inano be improved?

PURPOSE

Fistula-in-ano anatomy and its relationship with anal sphincters are important factors influencing the results of surgical management. Preoperative definition of fistulous track(s) and the internal opening play a primary role in minimizing iatrogenic damage to the sphincters and recurrence of the fistula.

METHODS

Physical examination and endoanal ultrasound (performed with a 10 MHz endoprobe), either conventionally or with an injection of hydrogen peroxide, were performed in 26 consecutive patients. Results were matched with surgical features to establish their accuracy in preoperative fistula-in-ano assessment.

RESULTS

Accuracy rates of clinical examination endoanal ultrasound, and hydrogen peroxide-enhanced ultrasound were 65.4, 50, and 76.9 percent for primary tracks, 73.1, 65.4, and 88.5 percent for secondary tracks, and 80.8, 80.8, and 92.3 percent for horseshoe extensions, respectively. Compared with physical examination and endoanal ultrasound, accuracy of hydrogen peroxide-enhanced ultrasound was higher for transsphincteric and intersphincteric primary tracks and horseshoe extensions. Both endoanal ultrasound and hydrogen peroxide-enhanced ultrasound displayed a significantly higher accuracy in detecting the internal openings (53.8 and 53.8 percent, respectively) compared with clinical evaluation (23.1 percent; P = 0.027).

CONCLUSIONS

Our data suggest that hydrogen peroxide-enhanced ultrasound can be very reliable and useful in the definition of fistula anatomy, its relationship with anal sphincters, and, hence, surgical strategy. It also improves identification of secondary extensions, particularly horseshoe tracks. This method, besides being safe, economic and reputable, both preoperatively and postoperatively, could be helpful in checking operative results and recurrence.

Crohn's disease: new imaging techniques

This chapter reviews the current state of imaging in Crohn's disease. Imaging plays an important role in the diagnosis and management of Crohn's disease. Imaging is complementary to the clinical assessment of the patient and other investigations including endoscopy. The choice of imaging modality depends on the clinical circumstances and local availability of resources and skills. Close co-operation between clinicians and radiologists is important. Barium radiology remains important. Magnetic resonance imaging (MRI) and ultrasound (US) should get special consideration because of the lack of ionizing radiation. MRI is particularly good at demonstrating the perianal complication of Crohn's disease. Computer tomography (CT) and US can be used for image-guided drainage of abscesses.