Clinical application of magnetic resonance imaging in the diagnosis of perianal abscess

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Clinical application of magnetic resonance imaging in the diagnosis of perianal abscessZhang Dan, Wang Yanhua, Zhu Xin Chen * *Jiangsu Jiang


Clinical application of magnetic resonance imaging in the diagnosis of perianal abscess

Zhang Dan, Wang Yanhua, Zhu Xin Chen * *

Jiangsu Jiangsu Province Traditional Chinese Medicine Hospital, Nanjing 210029, China

Abstract: Objective To explore the application of MRI technique in the diagnosis and treatment of perianal abscess by MRI guided by intraluminal water sac. Methods a total of 22 patients with perianal abscess were examined by magnetic resonance phased array coil. The operation results for the standard comparison of preoperative local examination, radiologists and specialists of MRI reading results. Results in 22 cases (16 cases, 6 cases of high and low) preoperative diagnosis of perianal abscess in patients by MRI examination showed: the abscess involved in clearance of the judgment accuracy rate of intraoperative diagnosis of anaphora is 50%, the radiologist preoperative MRI reading accuracy 90.9%, specialist MRI reading accuracy rate of 95.4% the two groups had statistical significance, MRI read operation results and follow-up results of different Anaphora (p< 0.05); for the diagnosis of abscess in the mouth of the operation before the detection rate was 86.3%. The Department of Radiology specialist MRI positive rate was 27.2%, MRI positive rate was 31.8%, two groups of MRI reading results and operation results are differences in diagnosis of anaphora statistical significance (p< 0.05). In the high group of anaphoric abscess diagnosis of abscess cavity relates to accurate rate of clearance is 43.7%, in the mouth of the detection rate was 87.5%, the radiology reading gap relates to the accuracy rate was 81.2%, in the detection rate of 37.5%, college reading clearance accuracy rate is 87.5%, the detection rate was 43.7% in group MRI, high abscess reading results operation and diagnosis of anaphora showed statistically significant differences (p< 0.05). Conclusion MRI provides a good guiding value for the judgment of abscess involving gap, and makes up for the deficiency of rectal palpation. For in the mouth of correctly judging the preoperative anal rectal examination more positive, imaging still cannot replace the anal rectal examination; but for high perianal abscess, prompt and validation of MRI examination in the abscess in the mouth also play a positive significance.

Magnetic resonance imaging; perianal abscess; diagnosis;

Perianal abscess preoperative accurate diagnosis and evaluation to ensure the success of the operation and the anal function protection is currently mainly based on a detailed examination of the local clinicians. Experienced specialists can judge accurately in the mouth, but for the clearance of lesions involving easily missed, especially high complexity or perianal abscess misdiagnosis rate is high, it can not accurately determine the relationship between the abscess cavity and sphincter. With the development of imaging technology, scholars abroad have confirmed that MRI can provide accurate anatomical structure, anal sphincter and anal sphincter pus cavity the imaging image, provide anatomical and pathological data of [1-3] surgery required. We use the technique of MRI, and we know the clinical treatment effectively:

1 materials and methods

1.1 general information

22 patients were hospitalized in the Department of anus & intestine surgery of Jiangsu Province Traditional Chinese Medicine Hospital, all cases included in the diagnosis of perianal abscess, including high in 16 cases, low in 6 cases. There were 20 males and females, aged 19~71 years, with an average age of 36.5 years. All of the patients had a history of perianal abscess in all of the 4 patients. All of the patients had symptoms or signs of acute infection.

1.2 method

All the cases were performed immediately after digital rectal examination, followed by MRI with anorectal examination, examination and surgical treatment of lesions inside the mouth and scope under anesthesia. Rectal palpation and surgical exploration were performed by a senior physician in the Department of anus & intestine surgery. The MR imaging report was read by an independent imaging physician.

Partial inspection

The patient was admitted to the hospital immediately after the appointment of a local system and clinical evaluation. Preliminary to determine the relationship between abscess in the mouth lesions, anal lesions and anal sphincter and clearance.

MRI imaging examination

MRI examination and reading by the Jiangsu Province Traditional Chinese Medicine Hospital MR room senior physician. 2 hours before the routine enema, emptying the rectum. Before MRI examination in patients with rectal cavity placed modified after the three cavity tube (removal of the stomach, left esophageal sac, distal ligation), 80~100ml saline was injected into catheter esophageal balloon, the balloon in order to make the full expansion of anorectal expansion, helps increase the lesion and surrounding tissue contrast. Using 1.5T Avanto superconduct scanner, body coil. Patients were taken supine position for MRI scan. Respectively for axial, coronal and sagittal scanning, including T1 weighted image (T1W1) application since the cyclotron wave sequence, T2 weighted images (T2WI) application of short time inversion recovery (STIR) sequence, T2 weighted and fat suppression, thickness 3mm, interval. All patients underwent plain scan, axial and vertical sections of the anal canal, coronal and sagittal sections of the anal canal parallel to the axis. The MR imaging report was provided by independent imaging specialists (before the film was not informed of the clinical findings).

Specialist reading

All cases were examined by MRI before the operation, and the patients were re examined by the specialist before and after the operation, to further understand the rules of the image, and to improve the value of MRI examination.

The intraoperative exploration

MR after surgery. After caudal anesthesia, involving MRI results from the understanding of senior physicians in the detailed exploration of lesions in perianorectal, lesion clearance, lesions and anal sphincter.

The statistical analysis method

Using SPSS 11.5 statistical software. For comparison of the data analysis, qualitative data by chi square test, quantitative data with normal distribution with t test, does not meet the normal distribution with Wilcoxon rank sum test; unified hypothesis testing using two-sided test, given test statistic and its corresponding P value in P is less than or equal to 0.05 as statistically significant, P = 0.01 as a highly statistically significant.

The results of intraoperative exploration were compared with the results of MR, and the results were compared with the results of rectal palpation. All abscess data were analyzed statistically.

2 Results

22 patients were scanned successfully and got good image:

All the cases (including high and low) of anaphora diagnosis, preoperative MRI reading and export clearance results and compares the MRI Reading Specialist

Internal (correct)

Gap (correct number)

Before the diagnosis operation



Preoperative MRI



Specialist reading



* compared with P value of 0.05 < before the examination;

High abscess diagnosis, preoperative MRI anaphoric reading and reading specialist MRI port and the gap results in the abscess comparison

Internal (correct)

Gap (correct number)

Before the diagnosis operation



Preoperative MRI



Specialist reading



* compared with P value of 0.05 < before the examination;

From the analysis on the table, the gap relates to judgment of the abscess, MRI provides good guidance value for rectal examination is insufficient, but on the inside the mouth of the correct judgment of preoperative anal rectal examination is more meaningful, imaging still cannot replace the anal rectal examination. Check from MRI in terms of its accuracy in the high abscess group has reached 43.7%, while all the MRI check in the mouth of abscess group to determine the accuracy rate of only 31.8%, indicating that MRI examination for high abscess in the mouth tip, verify the effect may be relatively more valuable. In the high abscess group MRI examination, not only can fully reflect the abscess involved in the gap, the accurate rate of internal mouth is also improved, showing high abscess in the application of MRI technology is more significant.

3 discussion

Now that the main reason of perianal abscess formation after anal fistula or recurrent abscess: failed to correctly identify the lesion of the mouth; abscess involves understanding is not enough, there were local potential fistula or die cavity, cause local drainage is not sufficient; the basic disease potential, such as Crohn's disease, tuberculosis immunodeficiency disease or [4]. Therefore the correct preoperative evaluation in the position of the mouth, abscess range of right in the mouth and the existing branch and dead space is to ensure that the key to cure. At the same time, to accurately determine the relationship with the surrounding tissue of the sphincter of the abscess cavity, is conducive to the scientific design of the main incision, to avoid damage to the muscle tissue, effectively maintain normal anal function..

MRI from the sagittal, coronal and transverse position to obtain the ideal image, which can fully display all the muscles around the anus. With the application of the rectal coil, more detailed imaging data are provided. Desouza said MRI endorectal coil can display the anorectal muscle and peripheral fat, the accurate rate of diagnosis of anal fistula and rectal abscess 100%[1]. Mamyama et al. 24 cases of high abscess were examined by MRI body coil, and the accuracy of the diagnosis of high abscess was 95%[5]. The study results show that the MRI of perianal abscess gap relates to the accuracy rate was 95.4%, and Mamyama reported similar results, but the perianal abscess in the mouth of the detection rate is only 27.2%, that in the mouth of the judge should rely more on preoperative rectal examination, should not exaggerate the role of MRI. The significance of MRI in the judgment of the perianal abscess is more likely to be reflected in the preoperative and intraoperative findings.

Due to the normal lower rectum in the closed or semi closed state, it is difficult to show that the relationship between the anal canal and surrounding tissue structure. Some scholars advocate the direct injection of gas or water through the anus, but directly from the anus water injection can not make the middle and lower rectal expansion. For elderly patients, there are different degrees of anal sphincter relaxation, transanal direct injection or gas injection to be tolerated by patients, and often have obvious reflection in the rectum levator ani, shrinkage, thickening, but not up to the expansion of the lower rectum to even bring adverse effect to the diagnosis. Based on the above reasons, the hospital with the air bag three cavity tube made modified [6], the catheter in the air bag in the appropriate amount of water. Some of the cases in this study by using this method, three cavity tube placed in the rectum cavity improved after intracapsular injection, the dilated bowel, not only can be fully displayed, but also to determine the muscles around the lesions and anorectal contrast.

During the course of clinical observation, we found that the specialist in reading and also reflects the stronger pertinence, has the radiology reading role can not be replaced, although both through statistical analysis differences are not obvious, but due to the combination of the local college examination before operation, the reading process is still found in radiology reading no clear branches and inside the mouth cavity. We think the anorectal specialist reading is also valuable in intraoperative edge exploration, while reading, while MRI surgery; accurate diagnosis and clearance of abscess abscess clearance and surrounding tissues, especially the muscles clearly show the relationship, for the accurate positioning operation and full protection of sphincter tissue provides an objective basis for.


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[2] Beet s Tan RG, Morren GL, Beet s GL, et al Measurement of anal. Sphincter muscles: endoanal U S, endoanal MR imaging, or phased array MR imaging A study with healthy volunteer? S [J]. Radiology, 2001; 220 (1): 81-89.

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[4] Michael Keighley RB, Norman Williams. Surgery the anus, rectum and colon. 2003, first edition, Science Press,,

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