采用16层螺旋CT诊断直肠癌淋巴结转移的初步研究

目的：评价16层螺旋CT扫描对直肠癌淋巴结转移的诊断价值。方法：回顾性分析64例经手术病理证实的直肠癌CT表现,统计直肠肿瘤周围淋巴结肿大情况并与术后病理结果进行对照分析。结果：以3 mm、6 mm、8 mm、10 mm短径为标准,直肠癌淋巴结转移的转移率分别为31%,37%,54%,75%。以6 mm作为诊断标准时,敏感度及准确度分别为95%、47%,阴性似然比为0.2。淋巴结个数≤4枚,转移率为6.25%;4~9枚组,转移率为52.3%;淋巴结10枚组,转移率为29.6%,淋巴结≤4枚组与4~9枚组、≥10枚组之间比较差别有统计学意义（P〈0.05）;浆膜面浸润组淋巴结转移率（40%）明显高于无浆膜面浸润组（11%）（P〈0.05）。结论：CT扫描有助于发现直肠癌癌肿周围肿大的淋巴结,淋巴结短径≥6 mm提示直肠癌淋巴结转移,直肠周围淋巴结数目大于4枚及肿瘤浆膜层浸润转移率明显提高。     

胆囊癌淋巴结转移的多层螺旋CT分析

目的 探讨胆囊癌淋巴结转移的MSCT表现,以期提高对胆囊癌淋巴结转移的认识.方法 65例经手术病理证实的胆囊癌患者行MSCT三期扫描,分析所有胆囊癌淋巴结转移的CT表现,并与手术病理对照.结果 本组收集65例中,43例共发现淋巴结201枚,其中32例中183枚淋巴结符合MSCT转移的诊断标准;11例发现<1 cm淋巴结18枚,其中阳性3枚,准确性为87%;CT的阳性预测值为91%,阴性预测值为83%.胆囊癌淋巴结转移以肝门和胰头十二指肠旁最为多见,其强化方式与原发肿瘤一致.结论 胆囊癌淋巴结转移是最常见的转移方式,MSCT扫描可以明确胆囊癌的淋巴结转移,有助于术前分期和减少误诊.     

食管癌淋巴结转移的术前MSCT评价

目的:评价食管癌淋巴结转移的术前MSCT表现,探讨其对术中淋巴结清扫的应用价值。方法:回顾性分析126例食管癌的术前MSCT检查资料及术后临床资料,分析淋巴结转移的MSCT表现。结果:将术前MSCT图像中淋巴结短径≥5mm或<5mm,同时伴强化视为异常淋巴结标准。MSCT共检出异常淋巴结282枚,分别为左右气管旁46枚,隆突下45枚,主肺动脉窗64枚,食管旁68枚,左下肺韧带周围13枚,锁骨上及膈下46枚。126例手术共摘除阳性转移淋巴结303枚,MSCT漏诊30枚,误诊9枚。MSCT检出的282枚异常淋巴结中,术后病理证实转移的227枚,检出率为80.5%。其中,短径<5mm的阳性淋巴结7枚,短径5¹0mm淋巴结42枚,短径>10mm淋巴结178枚,阳性转移率分别为22.6%(7/31)、64.6%(42/65)、95.7%(178/186)。阳性转移的227枚淋巴结中,静脉期CT值<60 HU的淋巴结52枚,>60 HU的175枚,分别占阳性转移淋巴结的22.9%、77.1%。结论:食管癌淋巴结转移术前MSCT检查具有很高的应用价值,对临床治疗具有重要的指导意义。     

多层螺旋CT对腹腔镜下全直肠系膜切除术治疗直肠癌的指导意义

目的 探讨腹腔镜下全直肠系膜切除术(LTME) 根治直肠癌术前MSCT TNM分期的应用价值.方法 回顾性分析58例经手术病理证实为直肠癌的术前CT检查的影像资料进行TNM分期,并观察直肠周围淋巴结数目、大小及分布情况,结果与最终病理对照研究.统计方法选用Kappa一致性检验.结果 术前MSCT表现TNM分期中T分期的准确性为75.9%(44/58),N分期准确性为67.2%(39/58),术前T分期结果与病理分期结果具有中度一致性(Kappa值为0. 620),N分期具有中度一致性(Kappa值为0.500).结论 直肠癌术前MSCT TNM分期对腹腔镜下全直肠系膜切除具有指导价值.     

直肠充气CT扫描在直肠癌术前诊断中的临床应用

目的 探讨直肠充气CT扫描在直肠癌术前诊断中的临床应用价值.资料与方法 分析经手术病理证实的67例直肠癌患者直肠充气CT扫描的表现,比较CT分期和病理分期的符合率.结果 67例直肠癌的CT诊断准确率为100%;诊断直肠癌侵犯浆膜外脂肪的阳性预测值、阴性预测值、敏感性、特异性、假阳性率、假阴性率分别为93.2%、75%、96.5%、60%、加%、3.5%;诊断盆腔区域淋巴结转移的阳性预测值、阴性预测值、敏感性、特异性、假阳性率、假阴性率分别为74.2%、69.4%、67.6%、75.8%、24.2%、32.4%;CT分期和病理分期Ⅰ～Ⅲ期的符合率分别为75%、60.7%、74.2%,总符合率为68.7%.结论 直肠充气CT扫描能较准确地检出直肠癌和显示浆膜外脂肪的侵犯;但对直肠癌的分期和淋巴结转移的判定仍有一定的局限性.     

直肠癌N分期相关影像学因素CT与病理对照研究

目的分析直肠癌淋巴结转移的相关CT表现,探讨与N分期相关的影像学规律。方法术前行盆腔CT检查的直肠癌病例59例,男38例,女21例,年龄36～80岁,中位年龄58岁。对切除标本进行淋巴结切片检查,以病理学诊断转移淋巴结阳性数为标准,按照美国癌症联合会(AJCC)N分期定义分为pN0、pN1、pN2组。采用影像工作站电影回放方式对所有病人图像进行复阅,观察盆腔淋巴结数目、大小、分布、原发肿瘤的浆膜表现及是否环周生长等情况,由2位放射医生盲法阅片并达成一致。统计方法选用KruskalWallis秩和检验及χ2检验。结果所有淋巴结转移阳性病例在CT均有淋巴结显示,pN0、pN1及pN2组CT检出的最大淋巴结径线随转移程度进展逐渐增大,分别为(4.13±3.21)mm、(7.43±3.27)mm和(10.27±3.88)mm,差异有统计学意义(χ2=23.842,P<0.01);pN0、pN1及pN2组CT检出淋巴结数目随转移程度进展逐渐增多,平均数目分别为(3.40±2.75)枚、(5.07±3.02)枚、(8.93±2.99)枚,差异有统计学意义(H=21.834,P<0.01);各组检出淋巴结的径线其差异有统计学意义(H=32.037,P<0.001)。单纯直肠旁淋巴结显示、肠旁和直肠上动脉旁同时显示及合并髂血管旁淋巴结显示的淋巴结转移分别为3例(3/12),17例(17/29)和8例(8/11),淋巴结分布方式在pN0、pN1、pN2组差异有统计学意义(χ2=19.517,P<0.05)。直肠癌淋巴结转移组CT表现为浆膜异常及环周生长者均高于非转移组,差异有统计学意义(χ2=8.979,P<0.01;χ2=5.107,P<0.05)。结论直肠癌淋巴结有无转移及转移程度不仅与淋巴结大小有关,还与淋巴结CT检出数目和淋巴结分布方式及癌肿浆膜和(或)外膜、环周生长情况有关。综合分析CT检出淋巴结的大小、数量、分布、癌肿浆膜和(或)外膜及环周生长等相关因素有助于提高CT直肠癌N分期的准确性。     

螺旋CT在直肠癌诊断中应用价值

目的评价螺旋CT在直肠癌诊断中价值。方法回顾性分析50例经手术病理证实的直肠癌的螺旋CT表现,观察肿瘤的生长方式、大小、密度、强化程度、侵犯周围组织及转移等特点,并与病理结果进行对照分析。结果螺旋CT表现为肠壁不规则增厚、肠腔狭窄34例;软组织肿块16例,肿块偏心状生长,呈分叶状或不规则形,表面凹凸不平,并可见溃疡面;17例侵犯浆膜面;增强扫描增厚的肠壁明显强化。螺旋CT表现与手术病理对照结果:CT显示病灶准确性为98.0%(49/50),显示淋巴结转移符合率为89.7%(26/29),假阳性为10.3%(3/29),假阴性为42.9%(9/21)。结论直肠癌的螺旋CT诊断与手术病理分期有较好的一致性,CT是直肠癌术前诊断的重要检查方法。     

多层螺旋CT在结直肠癌诊断中的价值

目的 探讨多层螺旋CT(MSCT)在结直肠癌诊断中的价值.方法 回顾性分析经手术病理证实的42例结直肠癌MSCT资料,所有病例均做多平面重组(MPR),部分病例加做曲面重组(CPR)、表面遮盖法重组(SSD) 、仿真结肠镜成像(CTVC)、透明重建(Raysum),将MSCT表现与手术和病理结果进行比较.结果 MSCT对结直肠癌的检出率为100%,定性准确率100%;对肿瘤向邻近组织侵犯诊断准确率为82.9%(29/35),腹部脏器转移诊断准确率为100%(7/7),淋巴结转移诊断敏感性为71%(22/31)而特异性为100%.结论 MSCT扫描结合多种重建技术能明确结直肠癌的诊断,对临床治疗有指导作用.     

多层螺旋CT扫描在结直肠癌诊断和术前分期中的应用价值

目的:评价多层螺旋CT扫描(MSCT)在结直肠癌诊断和术前分期中的应用价值。方法:回顾性分析经手术或常规结肠镜活检病理证实的40例结直肠癌的多层螺旋CT表现,并与病理结果对照。结果:病理证实结直肠癌40例(其中盲肠癌6例,升结肠癌3例,横结肠癌3例,降结肠癌5例,乙状结肠癌1例,直肠癌22例),多层螺旋CT检出了全部结直肠癌,敏感性为100%,总的分期准确率为80%(32/40),B期分期准确率为83.3%(15/18),C期分期准确率为66.7%(8/12),肿瘤浆膜外侵犯的敏感性和特异性分别为95%(36/34)和50%(2/4),淋巴结转移的敏感性和特异性分别为60%(12/20)和90%(9/10)。结论:多层螺旋CT扫描(MSCT)可以有效地显示结直肠癌的部位、大小和形态、确定中晚期结直肠癌的侵犯范围、远处转移及淋巴结转移等,从而更准确地诊断并进行术前分期,具有较高的临床应用价值。     

多排螺旋CT双体位检查对结直肠癌术前评估的价值再探

目的:探讨多排螺旋CT(MSCT)双体位检查对结直肠癌术前分期的价值.材料和方法:搜集102例经肠镜确诊的直肠癌患者行MSCT仰卧、俯卧位扫描,扫描前清洁肠道,并经肛门注气,扫描范围从膈顶至耻骨联合下缘.102例结直肠癌患者全部经肠镜或手术病理证实,全部病例均有手术、术前MSCT、术后病理等完整资料参与分期研究,将影像诊断结果与手术病理结果进行对照.结果:MSCT总的分期准确率82.4%(84/102),判断T、N、M分期的准确率分别是93.1%(95/102)、83.3%(85/102)、99.0%(101/102),判断淋巴结转移的敏感性和特异性分别为93.9%和88.7%.结论:MSCT双体位扫描对直肠癌的术前分期有重要价值,有助于判断肿瘤浆膜外侵犯及区域淋巴结转移情况.     

胰腺癌胰周淋巴结转移分布特征的螺旋CT表现

目的:胰腺癌胰周淋巴结转移的分布特征及螺旋CT影像表现。方法:搜集经手术病理诊断为原发性胰腺癌45例,所有病例均经手术病理或影像标准诊断有胰周淋巴结转移。根据本组45例病例CT所反映的肿大淋巴结的分布情况,将胰周淋巴结分为8组。设定淋巴结的短径≥1.0cm为淋巴结转移阳性的影像表现。统计阳性淋巴结的出现率,重点观察淋巴结转移的部位、大小、数目、形态、密度、强化情况。结果:本组45例胰腺癌中,共计89个部位观察到淋巴结转移胰周转移淋巴结以腹腔动脉干组46.7%(21例),肠系膜根部组46.7%(21例),腹主动脉周围组35.6%(16例)为最多,胃周11.1%(5例)及脾动脉-脾门组13.3%(6例)最少。结论:胰腺癌转移所致肿大淋巴结主要分布在腹腔干、肠系膜根部以及腹主动脉周围。螺旋CT扫描检查可以较准确显示胰腺癌胰周淋巴结的转移情况。     

High-resolution MR imaging for nodal staging in rectal cancer: are there any criteria in addition to the size?

PURPOSE: MR staging of nodal metastases in patients with rectal cancer using criteria based on size, shape and signal intensity can be difficult, because > or =50% of the nodes are less than 5 mm in size. Therefore new MR criteria were evaluated to see whether it can improve the MR assessment of nodal metastases in rectal cancer patients. MATERIALS AND METHODS: Ninety-nine patients with primary rectal carcinoma underwent 1.5 T high-resolution MRI with a quadrature phased array coil. Among them, 75 patients who had undergone total mesorectal excision were enrolled in this study. An MR radiologist, blinded for the histological results, randomly recorded the characteristics of each detectable node (LN); common criteria such as short-axis diameter, the ratio of long- to short-axis diameter, and signal intensity on each sequence; new criteria such as the margin (smooth, lobulated, spiculated, indistinct), a homogenous or mottled heterogeneous appearance, gross enhancement and its pattern, the venous encasement, and the dirty perirectal fat signal. RESULTS: Among 75 patients, 22 (29%) were node-positive. All patients who did not have detectable LN on MR were node-free (n = 15). Presence of LNs > 4 mm was significantly higher in the node-positive group. Presence of LNs > 8 mm was seen only in the node-positive group. Presence of a spiculated border and an indistinct border shows sensitivities of 45 and 36%, and specificities of 100 and 100%, respectively. Presence of a mottled heterogeneic pattern shows a sensitivity of 50%, a specificity of 95%. The presence of these three features were strongly correlated with LN positivity (P < 0.001, respectively). Presence of a venous encasement (n = 4) and dirty perirectal fat signal (n = 3) were also significantly (P < 0.05, respectively) correlated with LN positivity. CONCLUSION: In addition to size, new criteria such as a spiculated or indistinct border and a mottled heterogeneous appearance could be useful to predict regional lymph node involvement in patients with rectal cancer.     

Morphologic predictors of lymph node status in rectal cancer with use of high-spatial-resolution MR imaging with histopathologic comparison

PURPOSE: To evaluate signal intensity and border characteristics of lymph nodes at high-spatial-resolution magnetic resonance (MR) imaging in patients with rectal cancer and to compare these findings with size in prediction of nodal status. MATERIALS AND METHODS: Forty-two patients who underwent total mesorectal excision of the rectum to determine if they had rectal carcinoma were studied with preoperative thin-section MR imaging. Lymph nodes were harvested from 42 transversely sectioned surgical specimens. The slice of each lymph node was carefully matched with its location on the corresponding MR images. Nodal size, border contour, and signal intensity on MR images were characterized and related to histologic involvement with metastases. Differences in sensitivity and specificity with border or signal intensity were calculated with CIs by using method 10 of Newcombe. RESULTS: Of the 437 nodes harvested, 102 were too small (<3 mm) to be depicted on MR images, and only two of these contained metastases. In 15 (68%) of 22 patients with nodal metastases, the size of normal or reactive nodes was equal to or greater than that of positive nodes in the same specimen. Fifty-one nodes were above the area imaged, and seven of these contained metastases. The diameter of benign and malignant nodes was similar; therefore, size was a poor predictor of nodal status. If a node was defined as suspicious because of an irregular border or mixed signal intensity, a superior accuracy was obtained and resulted in a sensitivity of 51 (85%) of 60 (95% CI: 74%, 92%) and a specificity of 216 (97%) of 221 (95% CI: 95%, 99%). CONCLUSION: Prediction of nodal involvement in rectal cancer with MR imaging is improved by using the border contour and signal intensity characteristics of lymph nodes instead of size criteria.     

螺旋CT增强扫描对食管癌淋巴结转移的诊断价值

目的探讨多层螺旋CT(MSCT)强化扫描评价食管癌淋巴结转移的价值。方法35例食管癌患者行MSCT增强扫描(安射力(320mg/100ml)90ml,注射速度2.5ml/s,延迟55s扫描),扫描范围从舌骨水平至肝下缘,将原始数据重建为层厚1.25mm,层间隔1mm,应用多平面重建(MPR)进行图像后处理。CT扫描以气管食管沟淋巴结短径大于5mm、其余区域淋巴结及腹腔淋巴结短径大于10mm为转移标准统计。淋巴结分组按照Korst提出的食管癌淋巴结简化分组标准进行分组。所有患者均接受手术治疗,切除组织均经病理证实。以病理结果为标准,分析MSCT在诊断食管癌淋巴结转移方面的灵敏度、特异度、准确率。结果35例食管癌患者中鳞癌33例,腺癌1例,鳞腺癌1例,手术共清除淋巴结318枚,病理证实66枚有转移。MSCT共诊断淋巴结转移74枚,正确诊断56枚转移淋巴结,其灵敏度、特异度、准确率分别为84.8%、92.9%、91.2%。结论MSCT强化扫描发现食管癌淋巴结转移有较高的准确性和特异性,可为临床术前确定治疗方案提供重要的帮助。     

CT-pathologic correlation of axillary lymph nodes in breast carcinoma

A prospective study was performed to determine whether thoracic CT yielded useful information regarding the status of axillary lymph nodes (LNs) in patients with breast cancer. Thirty-five consecutive patients with clinically suspected stage II or III breast carcinomas were scanned preoperatively from the supraclavicular regions to the lung bases. Axillary LNs measuring greater than or equal to 1 cm were considered abnormal. The lymph nodes were classified according to their relationship to the pectoralis muscle. Extracapsular lymph node extension was diagnosed when there was irregularity and spiculation of the lymph node margin with surrounding fatty infiltration. Correlation with axillary dissection was obtained in 20 patients, giving a positive predictive value for axillary metastases of 89% with 50% sensitivity, 75% specificity, and 20% negative predictive value. CT was also able to detect the level of axillary involvement accurately when the lymph nodes were enlarged and to evaluate extracapsular LN extension. Although superior to physical examination, CT was not an accurate predictor of axillary LN involvement, primarily because of its low negative predictive value.     

多层螺旋CT扫描在结肠癌术前分期中的应用

目的　评估结肠充气多层螺旋CT扫描(MSCT)在结肠癌术前分期中的应用价值。方法　对36例临床高度怀疑或内镜活检证实的结肠癌患者进行MSCT检查,并利用工作站进行后处理以获取CT仿真内镜(CTVE)、多平面重建(MPR)、表面阴影成像(SSD)和透明显示(Raysum)图像,并结合横断面图像,进行肿瘤原发灶、淋巴结和转移情况分期(TNM分期),然后与术后病理对照。结果　MSCT术前T分期敏感度为96 .97% (32 /33),阳性诊断准确度为87 .88% (29 /33 );N分期灵敏度为73 .91% (17 /23),阳性诊断准确度为69. 57% ( 16 /23 )。转移淋巴结平扫CT值为( 38 .57±5.02)HU, 增强后CT值为(59.51±5 .35)HU,差异有统计学意义(t=3 .963,P<0. 05);未发生转移的淋巴结平扫CT值为(29 .16±3 .66)HU,增强后CT值为(47 30±1 70)HU,差异有统计学意义(t=4 997,P<0 05)。5例肝脏转移的患者均被CT检查发现。结论　MSCT可以有效地显示肿瘤的形态、大小和部位,确定肿瘤的侵犯范围、淋巴结转移和远处转移等,从而更准确地进行术前分期。不受肠管狭窄程度的限制,可以显示气体能够通过的任何部位,从而弥补了肠镜检查的不足。但术前对于早期病变T1 ~T3 分期还有一定限度;N分期较困难,必须综合其大小、形态、密度及其生物学行为进行全面的判断。     

Dual-energy CT can detect malignant lymph nodes in rectal cancer

BackgroundThere is a need for an accurate and operator independent method to assess the lymph node status to provide the most optimal personalized treatment for rectal cancer patients.This study evaluates whether Dual Energy Computed Tomography (DECT) could contribute to the preoperative lymph node assessment, and compared it to Magnetic Resonance Imaging (MRI).The objective of this prospective observational feasibility study was to determine the clinical value of the DECT for the detection of metastases in the pelvic lymph nodes of rectal cancer patients and compare the findings to MRI and histopathology.Materials and methodsThe patients were referred to total mesorectal excision (TME) without any neoadjuvant oncological treatment. After surgery the rectum specimen was scanned, and lymph nodes were matched to the pathology report.Fifty-four histology proven rectal cancer patients received a pelvic DECT scan and a standard MRI.The Dual Energy CT quantitative parameters were analyzed: Water and Iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value, for the benign and malignant lymph node differentiation.ResultsDECT scanning showed statistical difference between malignant and benign lymph nodes in the measurements of iodine concentration, Dual-Energy Ratio, Dual Energy Index, and Effective Z value.Dual energy CT classified 42% of the cases correctly according to N-stage compared to 40% for MRI.ConclusionThis study showed statistical difference in several quantitative parameters between benign and malignant lymph nodes. There were no difference in the accuracy of lymph node staging between DECT and MRI.     

直肠癌术前CT扫描的价值

目的：评估直肠癌术前ＣＴ扫描的价值。材料与方法：１０４例直肠癌（Ｔ２期１１例、Ｔ３期９０例、Ｔ４期３例）的ＣＴ扫描与手术病理这缘改变、浸润周径、淋巴结大小对Ｔ、Ｎ分期的价值。结果：以肿瘤石头居齿状和结节改变作为Ｔ３的诊断指标,其准确率分别为９４．０％、９０．４％、８８．４％;Ｔ分期的准确率是８９．４％,Ｔ３的准确率是９４．０％。将肿瘤侵犯肠管周径〉１／２与≤１／２作为Ｔ３期的诊断指标,有显著统计学     

结肠癌的多层螺旋CT表现与临床病理对照研究

目的：探讨结肠癌的多层螺旋CT（MSCT）表现,并与病理进行对照。方法：回顾分析56例经手术病理证实的结肠癌患者的MSCT表现,并与术后病理对照,分析MSCT术前分期的准确性。结果：①56例患者CT显示肠壁增厚,45例表现为肿块或结节;②25例分化较好的肿瘤呈轻-中度均匀强化,31例分化差的肿瘤呈不均匀强化或分层状强化;③MSCT显示结肠浆膜或/和周围脂肪间隙受侵的敏感度为95.83%,特异度为87.5%,准确度为94.64%,阳性预测值97.87%,阴性预测值77.78%;④MSCT诊断淋巴结转移的敏感度为91.67%,特异度为77.42%,准确度为82.14%,阳性预测值75.86%,阴性预测值88.89%;⑤MSCT术前T分期和N分期与术后病理分期的一致性较好（KT=0.864,P=0.000;KN=0.650,P=0.000）。结论：螺旋CT扫描可有效显示结肠癌的部位、大小和形态,确定肿瘤侵犯范围、有无淋巴结及远处转移等,可以准确进行术前分期,具有较高的临床应用价值。     

Evaluation of the ITV-margin and variables affecting bladder and mesorectal deformation during long course neoadjuvant radiotherapy for rectal cancer

Internal target volume (ITV) margins were estimated by evaluating the movement of mesorectum and bladder during neoadjuvant long-course radiation therapy (RT) for rectal cancer. In this prospective study, 23 patients with rectal cancer had planning CT (pCT) and weekly cone beam CT (CBCT) in supine position during preoperative long-course RT. Mesorectal wall motion was analyzed based on the coordinates of the most anterior, posterior, left and right points on the pCT and CBCT. Overlap volume (OV) between the pCT bladder and CBCT mesorectum was generated. Variables that might affect relative bladder volume (ratio of CBCT to pCT bladder volumes), anterior mesorectal wall position, and OV were studied. ITV margins were also calculated. In females, smaller OV and less movement of the upper anterior mesorectal wall were identified, suggesting smaller ITV margins might be required compared to males. The relative bladder volume did not change significantly over time and was correlated with OV: the larger the relative bladder volume, the less the OV. ITV margin of 0.8 to 1.1 cm in right-left direction is satisfactory. Posteriorly, only 8 to 9 mm margin is required for upper and mid rectal regions but double of this is required for inferior third. Anteriorly, 1.3 cm margin is adequate for lower and mid rectal regions and 2.4 cm is required superiorly. An anisotropic ITV expansion of clinical target volume (CTV) for rectal cancer radiotherapy contouring provides a robust method to encompass the deformation of bladder and mesorectum. The ITV margin should take into account sex and distance from the anal verge.