Endoluminal MR imaging of diseases of the anus and rectum

Endoluminal MRI of the rectum and anus was introduced in the first half of this decade to overcome the limitations of endoluminal sonography and body coil MRI. Endoluminal MRI is the imaging method of choice for fecal incontinence and anal tumors, whereas it is a competitive imaging method to phased array coil MRI in patients with perianal fistulas or rectal tumor. The purpose of this article is to describe the technique and major indications of endoluminal MR imaging of the anus and rectum.     

复杂性肛瘘手术采用核磁共振技术诊断对于临床效果的价值

目的：探究并分析核磁共振技术诊断复杂性肛瘘手术的临床效果。材料与方法：回顾性分析自2010年1月～2013年3月我院肛肠科收治的经手术探查确诊为复杂性肛瘘的50例患者,所有患者术前均进行核磁共振技术（MRI）扫描及一般检查,以手术结果为标准。将MRI检查及术前一般检查结果进行比较。结果：术前MRI检测结果为4例为单纯性肛瘘且均为肛管括约肌间瘘,46例为复杂性肛瘘（其中37例为经肛管括约肌瘘,7例高位肛瘘,2例肛瘘术后改变且合并骶前脓肿及合并盆腔内多发脓肿）。与手术探查的结果相比,MRI诊断对复杂性肛瘘的诊断准确率为92．00％,术前一般检查的诊断准确率为56．00％,术前MRI诊断准确率与手术探查较为接近,而术前一般检查的诊断准确则较术前MRI扫描低,P〈0．05,具有统计学意义;术前MRI扫描在肛瘘内口、肛瘘主管、肛瘘支管及脓腔方面的诊断准确率分别为72．00％、100．00％、92．00％,术前一般检查的诊断准确率分别为64．00％、60．00％、58．00％,术前一般检查及MRI扫描在肛瘘内口位置的诊断准确率较为相近,无明显差异（P〉0．05）;而在肛瘘主管、肛瘘支管及脓腔诊断准确率方面,术前MRI扫描的诊断准确率明显高于术前一般检查,P〈0．05,具有统计学意义。结论：对提高手术的成功率及避免过多的肛门括约肌损伤具有重要指导意义,值得在临床上广泛应用。     

Clinical applications of 3D T2-weighted MRI in pelvic imaging

Objective

The purpose of this article is to illustrate clinical applications of 3D T2-weighted MRI in pelvic imaging. We review technical considerations of 3D T2-weighted MRI with clinical examples.

Conclusion

3D T2-weighted MRI has been increasingly utilized for pelvic applications, including imaging of rectal cancer, prostate cancer, anorectal fistulas and the female pelvis. This relatively rapid technique offers good soft-tissue contrast of the pelvic organs, with potential for more widespread clinical use.     

High resolution MRI of anorectal malformation in the newborn: case reports of Currarino syndrome and anocutaneous fistula

To show the accuracy of a high-resolution magnetic resonance imaging (MRI) technique with a phased array coil in diagnosing anorectal malformation, we present two neonates with Currarino syndrome and anocutaneous fistula, respectively. Anatomy was visualized correctly with this technique, but conventional MRI did not show the complete extent of the disease. The reported high-resolution MRI findings concerning these conditions are scanty. Received: 26 March 2001/Accepted: 2 May 2001     

Value of endorectal coil versus body coil MRI for diagnosis of recurrent pelvic malignancies

Background: To compare endorectal coil magnetic resonance imaging (MRI) with body coil MRI in detecting local recurrence of gynecologic tumors and prostate and rectal cancers. Methods: Forty-six patients with suspected recurrent pelvic malignancies (13 gynecologic, 15 prostatic, and 18 anorectal primaries) were enrolled in the study. Axial T1- and T2-weighted body coil images and T2- and contrast-enhanced T1-weighted axial endorectal coil images were obtained on a 1.5 T system. Results of the MR examinations were compared with histogical findings and follow-up examinations with respect to the diagnostic accuracy and diagnostic confidence for assessment or exclusion of local recurrence. Results: Recurrent disease was histologically confirmed in eight patients with primary gynecologic malignancies, seven with suspected prostatic recurrence, and seven with suspected anorectal recurrence. Overall, accuracy of body coil MRI was 67% for gynecologic tumors, 36% for prostatic recurrences, and 59% for rectal recurrences. T2- and contrast-enhanced T1-weighted endorectal sequences yielded similar results, with an accuracy of 73% for depiction of gynecologic recurrence, 77% for prostatic recurrence, and 77% for rectal recurrence. The difference in accuracy between body coil and endorectal coil examinations was statistically significant (p < 0.05) only for prostatic cancer. Diagnostic confidence was, however, significantly improved (p < 0.05) in all tumors (T2-weighted endorectal coil examination was superior to T2-weighted body coil images in 71% of cases). Conclusion: Although the results of endorectal coil MRI are only slightly superior to those of body coil MRI for the detection of recurrent gynecologic and anorectal tumors, diagnosis can be made with greater diagnostic confidence in many cases. For detection of prostatic recurrence, endorectal MRI is highly recommended. Received: 27 April 1995/Accepted: 17 June 1995     

Endosonographic imaging of anorectal diseases.

OBJECTIVE: The normal sonographic anatomy of the anorectum, sonographic findings of anorectal diseases, and indications and limitations of endosonography compared with magnetic resonance imaging are reviewed. Methods. Endosonographic imaging was performed with a Siemens (Erlangen, Germany) FI 400 ultrasound scanner with an end-fire 7.5-MHz biplane endorectal probe and a B-K Medical (Sandhoften, Denmark) scanner with an 1850 axial-type side-fire 5.0- to 10.0-MHz rotating endoscopic probe. RESULTS: Rectal carcinoma appears on endorectal sonography as a low-echogenicity lesion that abruptly interrupts the normal sequence of layers. The internal anal sphincter is seen very clearly on endoanal sonography, and it is easy to appreciate atrophy and small tears of this sphincter. Endoanal sonography cannot accurately show thinning of the external anal sphincter. Peroxide-enhanced endoanal sonography is especially useful for patients with recurrent perianal fistulas in whom scarring should be distinguished from recurrent fistulas and detection of the internal opening. However, sonography does not provide an adequate deep and global display of all adjacent pelvic and perineal spaces. CONCLUSIONS: Endosonography can accurately stage primary rectal tumors and assess the internal anal sphincter. Peroxide-enhanced 3-dimensional imaging can increase the utility of endoanal sonography in detection and characterization of perianal fistulas and planning of optimal therapy. However, magnetic resonance imaging can be used a complementary modality to endosonography, especially for evaluation of external anal sphincter atrophy and deep pelvic inflammation.     

Three-dimensional transperineal sonographic characteristics of the anal sphincter complex in nulliparous women.

OBJECTIVE: To explore the morphological characteristics and normal biometry of the anal sphincter complex in nulliparous Chinese women using three-dimensional (3D) transperineal ultrasound. METHODS: 3D sonographic data from 55 nulliparous Chinese women (aged 19-38 years) who had no pelvic organ prolapse and no symptoms of pelvic floor dysfunction were retrieved from an image dataset and analyzed by offline post-processing. The morphological characteristics of the external and internal anal sphincters, puborectalis muscle and perineal body were assessed in the sagittal, coronal and axial views. RESULTS: The external anal sphincter had three sonographic components: the circular main body, a subcutaneous part and an extension portion. It was significantly thinner at 12 o'clock than at the 3, 6 and 9 o'clock positions. The internal anal sphincter was seen as dark echolucent strips of equal thickness. In the mid-sagittal view, it started from the anal verge and ended at the anorectal junction. The perineal body was an ovoid structure covering the upper margin of the external sphincter, while the puborectalis muscle was banana-shaped in the sagittal view and was located behind the anorectal junction, extending downward along the inferior margin of the posterior external sphincter extension. Sonographic characteristics of the anal sphincter complex did not vary with age, weight, height or body mass index. CONCLUSIONS: 3D transperineal ultrasound clearly demonstrates the spatial relationships of each component of the anal sphincter complex. This should allow standardized measurement of the complex for investigations of its function.     

Three-dimensional imaging of the anal sphincter: a new approach to anorectal manometry

Anorectal dysfunction can be an extreme embarrassment and inconvenience to persons afflicted with the condition, disrupting their lifestyle. Evaluation of the anal sphincter and the distinction between muscular and neural etiology is essential. Three-dimensional imaging of the anal sphincter by use of anorectal manometry with an eight-port perfused catheter combined with computer analysis aids in defining anal sphincter function. The use of three-dimensional imaging is valuable to the physician in the determination of the presence of a muscular defect, the location of the defect and the appropriateness of surgical intervention to resolve the anal dysfunction.     

Prospective assessment of interobserver agreement for endoanal MRI in fecal incontinence

BACKGROUND: Endoanal magnetic resonance (MR) imaging is a new technique for the assessment of anal sphincter integrity in fecal incontinence and an alternative to anal endosonography. The present study aimed to determine interobserver variation for assessment of anal sphincter integrity using endoanal MR imaging. METHODS: Fifty-two consecutive anally incontinent patients underwent MR imaging by using a purpose-built endoanal receiver coil and static 1.0-T magnet. T2-weighted axial, coronal, and sagittal scans were independently assessed by two radiologists who noted external and internal sphincter integrity. Findings were compared and agreement was assessed with the kappa statistic. RESULTS: There was disagreement in 18 of 49 technically adequate studies (37%; kappa = 0.46), indicating "moderate" agreement. Agreement was strongest if the sphincters were either both intact or both disrupted. Observers agreed in only one diagnosis of an isolated internal sphincter defect and in no diagnosis of an isolated external sphincter defect. CONCLUSION: The overall interobserver agreement for assessment of sphincter integrity using endoanal MR imaging is "moderate." Interobserver agreement using endoanal MR imaging is less than that reported for anal endosonography.     

Diagnosis of anal sphincter defects by three-dimensional transperineal ultrasound in women with anal incontinence

Purpose

To assess the utility of transperineal three-dimensional (3D) ultrasound for diagnosing anal sphincter defects and evaluating the function of the anal canal in women with anal incontinence.

Methods

The study subjects were 13 women with anal incontinence. Symptoms of fecal incontinence were assessed by Wexner score. The anal canal of each woman was examined ultrasonically with both a convex transperineal 3D scanner and a radial transanal scanner to compare the accuracy of the two approaches for diagnosis of anal sphincter defects. The anorectal angle and the length of the anal canal were also measured by utilizing the functionality of the transperineal 3D ultrasound.

Results

The mean age was 58.9?±?14.9?years (±SD), and the mean Wexner score was 8.4?±?5.6. In terms of ultrasound diagnosis of anal sphincter defects, the two methods showed consistent results in each woman. The length of the portion where both the internal and external anal sphincters were intact was significantly correlated with the Wexner score, whereas the total length of the anal canal was not.

Conclusions

Less invasive transperineal 3D ultrasound provides accurate evaluation of the internal and external anal sphincters in women with anal incontinence, and the method is potentially useful for detection of anal sphincter abnormalities.     

正常女性盆底解剖、形态的动态MRI研究

目的　采用静息与最大盆腔用力时盆腔动态MRI评价正常盆腔器官的位置、运动和盆底形态 ,为动态MRI在盆底功能性疾病诊断上的临床应用建立盆腔器官运动程度和盆底形态学的正常标准。方法　对 3 0例健康女性志愿者进行静息与最大盆腔用力时盆腔动态MRI检查。采集的MR影像用于观测盆腔器官的位置、运动和盆底形态。结果　最大盆腔用力时正常盆底在形态上变化不明显 ,盆腔器官的平均下降值是膀胱颈 ( 15 .3± 4.3 )mm ,子宫颈 ( 10 .7± 3 .4)mm ,肛直肠连接 ( 19.2± 6.8)mm ,盆隔裂孔的平均增大百分比是 ( 12 .2± 6.4) %。盆腔器官运动的范围是膀胱颈不超过耻尾线下1cm ,子宫颈不超过耻尾线以下 ,肛直肠连接不超过耻尾线以下 2 .5cm。结论　MRI是研究活体盆底解剖与形态学的有效方法。正常妇女盆腔动态MR影像上 ,最大盆腔用力时盆腔器官有一定程度的运动 ,但无脱垂 ,盆底形态上变化不明显。     

MRI of anal cancer: assessing response to definitive chemoradiotherapy

Anal cancer is an uncommon malignancy of the gastrointestinal tract but has a relatively good prognosis with an 80% 5-year overall survival. In this article, we review the role of MRI for assessing treatment response in anal cancer after completion of definitive chemoradiotherapy. New generation MRI scanners with optimal-phased array body coils, resulting in better signal to noise and improved contrast and spatial resolution, have contributed to high-resolution imaging in clinical practice enabling visualization of relevant anatomy including the sphincter complex, adjacent structures, mesorectal and pelvic lymph nodes with a diameter down to 2 mm. Multiplanar, high-resolution T2-weighted and diffusion-weighted sequences have a role in initial locoregional staging of anal SCC, assisting radiotherapy planning, as well as in assessing response to treatment and treatment-related complications.     

Diagnosis and conservative therapy of anal fecal incontinence

The main diagnostic tool for patients with anal incontinence is the anorectal physiology. The anorectal sphincter can be reliably tested. Due to the fact that an obstetric damage is the most common cause of anal incontinence, the transanal endosonography is the imaging method of choice for detecting a muscle defect. With high frequency ultrasound probes (preferable 10 Mhz) the pathomorphology of the sphincter can be studied in details. If conservative treatment is failing, the neurophysiology testing is helpful in deciding which surgical method (sphincter repair in case of an intact nervus pudendus, artificial sphincter or sacral stimulation in case of neuropathy). The conservative treatment includes increasing the internal sphincter muscle tonus by applying Phenylephrine locally or Loperamid per os. The biofeedback is basically a physical muscle training of the external sphincter with a visual or acoustic feedback of the muscle function to the patient. However, newer studies show that by this method the sensory function and the coordination of the anal sphincter are improving as well. With these conservative treatment options most of the patients suffering from anal incontinence can be treated satisfactorily.     

Video-assisted anal fistula treatment combined with anal fistula plug for treatment of horseshoe anal fistula

ObjectiveHorseshoe anal fistula is a common anorectal disease, and there is no standard procedure for its treatment. In this study, we performed a modified surgical procedure for the treatment of horseshoe anal fistula and investigated its efficacy and adverse effects.MethodsWe retrospectively analyzed the outcomes of video-assisted anal fistula treatment combined with an anal fistula plug (VAAFT-Plug) in 26 patients with a horseshoe anal fistula. The follow-up period ranged from 6 to 18 months. Preoperative and postoperative data were collected to analyze the cure rate, anal sphincter function, and incidence of complications.ResultsThe surgeries were successfully performed in all patients, 23 of whom were cured (effective cure rate of 88.46%). Three patients developed recurrence and were cured after traditional surgery. No patients developed severe complications or postoperative anal incontinence. The VAAFT-Plug protocol was performed with a small incision in the fistula that subsequently promoted fistula healing and preserved sphincter function.ConclusionAlthough randomized controlled trials will be needed to fully validate these findings, our results suggest that VAAFT-Plug represents a promising treatment strategy for horseshoe anal fistulas. This technique preserves normal anal function and achieves satisfactory outcomes in most patients.     

Does defecography help in diagnosis and clinical decision-making in defecation disorders?

Defecography is used to investigate patients with defecation disorders, especially obstructed defecation and anal incontinence. We studied 73 consecutive patients who complained of difficult defecation, anal incontinence, or idiopathic anorectal pain. The following defecographic parameters were recorded and compared in different patient groups: anorectal angulation, pelvic floor descent, formation of rectocele, and rectal invagination. Increasing number of childbirths correlated with pelvic floor descent in defecograms (r= 0.319, p< 0.05). There were no significant differences in defecographic parameters in patients with obstructed defecation, anal incontinence, or idiopathic anorectal pain. Thus, we conclude that defecography may be useful as an investigative tool in clinical research of defecation disorders, but it is of minor value in clinical diagnosis and decision-making.     

Local transdermal delivery of phenylephrine to the anal sphincter muscle using microneedles

We propose pretreatment using microneedles to increase perianal skin permeability for locally targeted delivery of phenylephrine (PE), a drug that increases resting anal sphincter pressure to treat fecal incontinence. Microneedle patches were fabricated by micromolding poly-lactic-acid. Pre-treatment of human cadaver skin with microneedles increased PE delivery across the skin by up to 10-fold in vitro. In vivo delivery was assessed in rats receiving treatment with or without use of microneedles and with or without PE. Resting anal sphincter pressure was then measured over time using water-perfused anorectal manometry. For rats pretreated with microneedles, topical application of 30% PE gel rapidly increased the mean resting anal sphincter pressure from 7 ± 2 cmH₂O to a peak value of 43 ± 17 cmH₂O after 1 h, which was significantly greater than rats receiving PE gel without microneedle pretreatment. Additional safety studies showed that topically applied green fluorescent protein—expressing E. coli penetrated skin pierced with 23- and 26-gauge hypodermic needles, but E. coli was not detected in skin pretreated with microneedles, which suggests that microneedle-treated skin may not be especially susceptible to infection. In conclusion, this study demonstrates local transdermal delivery of PE to the anal sphincter muscle using microneedles, which may provide a novel treatment for fecal incontinence.     

CT排便造影评价肛门外括约肌的功能

目的 采用CT排便造影显示肛门外括约肌(EAS)的形态及变化,评价其功能。方法 分静息、缩肛、排便3期采集60名健康志愿者的坐位CT排便造影图像,重建标准的肛管冠状位及正中矢状位图像,对耻骨直肠肌(Pr)和EAS进行形态学测量。结果 Pr、EAS的深部和浅部分别在肛门直肠结合部、肛管上部和中下部水平压缩肛管,EAS皮下部位于肛管下方,内翻呈圆锥状,与肛周皮肤共同自下而上封堵肛管。静息期,EAS深部间距(31.50±4.10)mm,浅部间距(28.36±4.14)mm,肛管-EAS皮下部夹角(60.95±19.20)°;缩肛期,EAS作向心运动,更紧地闭合肛管,深部间距(30.85±4.10)mm,浅部间距(26.04±3.48)mm,皮下部内翻程度加大,肛管-EAS皮下部夹角(56.87±16.18)°;排便期,EAS作离心运动,肛管开放,深部间距(37.51±5.17)mm;浅部间距(31.68±5.10)mm,皮下部自内上向外下翻转,肛管-EAS皮下部夹角(112.23±22.48)°。结论 EAS主要通过压缩、悬吊、绞索和套塞方式维持肛门自制。EAS的深部、浅部和皮下部在排便时依次开放,其皮下部作翻转运动参与排便。     

Abnormal findings on multiparametric prostate magnetic resonance imaging predict subsequent biopsy upgrade in patients with low risk prostate cancer managed with active surveillance

Purpose

To determine the ability of multiparametric MR imaging to predict disease progression in patients with prostate cancer managed by active surveillance.

Methods

Sixty-four men with biopsy-proven prostate cancer managed by active surveillance were included in this HIPPA compliant, IRB approved study. We reviewed baseline MR imaging scans for the presence of a suspicious findings on T2-weighted imaging, MR spectroscopic imaging (MRSI), and diffusion-weighted MR imaging (DWI). The Gleason grades at subsequent biopsy were recorded. A Cox proportional hazard model was used to determine the predictive value of MR imaging for Gleason grades, and the model performance was described using Harrell’s C concordance statistic and 95% confidence intervals (CIs).

Results

The Cox model that incorporated T2-weighted MR imaging, DWI, and MRSI showed that only T2-weighted MR imaging and DWI are independent predictors of biopsy upgrade (T2; HR = 2.46; 95% CI 1.36–4.46; P = 0.003—diffusion; HR = 2.76; 95% CI 1.13–6.71; P = 0.03; c statistic = 67.7%; 95% CI 61.1–74.3). There was an increasing rate of Gleason score upgrade with a greater number of concordant findings on multiple MR sequences (HR = 2.49; 95% CI 1.72–3.62; P < 0.001).

Conclusions

Abnormal results on multiparametric prostate MRI confer an increased risk for Gleason score upgrade at subsequent biopsy in men with localized prostate cancer managed by active surveillance. These results may be of help in appropriately selecting candidates for active surveillance.     

鞍旁脑膜瘤的MRI诊断

目的探讨磁共振成像在鞍旁脑膜瘤的MR表现特征及诊断价值。方法收集30例经临床、影像及手术病理证实的鞍旁脑膜瘤病例的MR常规平扫及增强扫描图像资料,分析鞍旁脑膜瘤病灶部位、形态及信号特征。结果MR平扫、增强发现30例鞍旁脑膜瘤,发生部位单发于一侧鞍旁海绵窦26例(累及同侧眼眶4例,累及翼腭窝3例),发生于双侧鞍旁海绵窦1例,颅内多发脑膜瘤合并一侧海绵窦脑膜瘤3例。结论应用合适的扫描技术,尤其是增强冠状位MR能很好的显示鞍旁脑膜瘤的发生部位、病灶大小、范围、信号特征,对周围邻近结构的累及状况,为临床手术和放疗定位提供准确的诊断依据。