Rectal Mass Research Articles

Prioritising primary care patients with unexpected weight loss for cancer investigation: diagnostic accuracy study (update)

ObjectiveTo quantify the predictive value of unexpected weight loss for cancer according to patient’s age, sex, smoking status, and concurrent clinical features (symptoms, signs, and abnormal blood test results).DesignDiagnostic accuracy...

Discordant Microsatellite Instability Status in Metachronous Primary Rectal Cancer Detected During IdyllaTM Microsatellite Instability Test Validation: A Case Report

Abstract Introduction/Objective Defects in DNA mismatch repair (MMR) can be identified by immunohistochemistry (IHC) MMR, Microsatellite Instability (MSI) status testing by PCR or by MSI testing by NGS. Discrepancies may occur between the different test methods. We describe a case of a discrepancy discovered during validation of an in-house IdyllaTM MSI test (PCR method), in which repeat testing by the external reference lab led to a definitive deficient MMR/MSI-High (MSI-H) status. Methods/Case Report A 67-year-old male presented with a new rectal mass on a follow-up colonoscopy. His past surgical history included a colorectal anastomosis secondary to a low anterior resection for pT3N0 upper rectal cancer ten years ago. He had a strong family history of colorectal cancer with his father, 3 brothers, 3 paternal uncles and 2 cousins affected. Colonoscopy revealed an adenocarcinoma 3 cm distal to the anastomosis. MRI showed a plaque-like mucosal thickening along the remaining rectum below the anastomosis. He underwent a complicated redo low anterior resection. Histopathology revealed a pT1N0 invasive moderately differentiated midrectal adenocarcinoma. Test results for an external PCR-based MSI test were microsatellite stable (MSS). However, repeat testing (requested after MSI-H status was detected by the in-house IdyllaTM MSI assay) revealed a deficient MMR status (loss of expression of MSH2 and MSH6 proteins) and MSI-H by PCR analysis. These discrepant results may have been due to low tumor cellularity and tumor heterogeneity (ie, heterogeneous pattern of MSH2/MSH6 loss on IHC). Results (if a Case Study enter NA) NA Conclusion Discrepancies in deficient MMR/MSI status between and within different test methods may be attributable to intratumoral heterogeneity and low tumor cellularity. In discordant cases, pathologists must not hesitate to perform a repeat analysis using alternate methods, as a deficient MMR/MSI-H diagnosis has crucial diagnostic, prognostic and predictive implications.

Rectal mass: cancer or endometriosis?

Rectal mass: cancer or endometriosis?

S2737 An Unusual Case of Rectal Mass Investigation Leading to Diagnosis of Syphilitic Proctitis

S2737 An Unusual Case of Rectal Mass Investigation Leading to Diagnosis of Syphilitic Proctitis

Endoscopic features of rectal mucosal prolapse syndrome (RMPS): differentiation with malignant rectal tumor

Background: Rectal mucosal prolapse syndrome (RMPS) usually manifests as rectal bleeding, and tenesmus. Endoscopically it could be easily misdiagnosed with malignant rectal tumor (MRT). This study aims to investigate factors to distinguish RMPS and MRT, and explore endoscopic features of RMPS. Methods: Patients endoscopically diagnosed as rectal lesions, mass, or tumors, were retrospectively collected. Clinical information, endoscopic images, histologic reports were reviewed. Patients endoscopically and histologically diagnosed as RMPS were included for phenotype classification. Results: 826 patients were enrolled, among them 755 (91.4%), 22 (2.7%), 10 (1.2%) and 39 (4.7%) were respectively diagnosed with MRT, RMPS, endometriosis, and neuroendocrine tumor. Compared with MRT, patients with RMPS were significantly younger (33.5 vs. 62, P< 0.001), and lesions were significantly smaller (2cm vs. 3cm, P=0.007). Moreover, clinical course of patients with RMPS would be significantly longer than those with MRT (12 months vs. 3 months, P<0.001). Morphologically, we classified lesions of RMPS into five phenotypes, that is, lesions with circumferential stenosis (19.4%), protrusions (41.7%), both ulcers and protrusions (11.1%), ulcers (11.1%), flat manifestations (16.7%). Protruding lesions were more frequently observed in females (P=0.039), while ulcerative lesions were found involving a smaller proportion of the rectal circumference (P=0.028). Lesions with only ulcers were found with a shorter distance compared with those with only protrusions (5cm vs. 10cm, P=0.034). Conclusions: Age, clinical course, and size of the lesion, could be applied to distinguish MRT and RMPS. Five phenotypes are introduced and features of ulcers/protrusions are further explored.

Using Remotely Operated Suction Irrigation System in da Vinci SP Submucosal Dissection.

Submucosal dissection using the da Vinci SP® system (Intuitive Surgical, Sunnyvale, CA, USA) is an emerging approach for treating premalignant lesions in the colon and rectum. The endoluminal space is tight and small, and during the procedure, this tight space is accessed by the 40 mm GelPOINT® Path transanal platform (Applied Medical, Rancho Santa Margarita, CA, USA). Most of the trocar space is occupied by the 25 mm port of the da Vinci SP® system. There is limited space for an additional trocar, and the full mobility of this trocar is restricted; hence there is a need for an effective suction irrigator during these procedures. Although the da Vinci SP® system has four instrument capabilities, it does not have a suction irrigation instrument. To address this issue, we tested a Remotely Operated Suction Irrigation System (ROSI™) (VTI, Nashua, NH, USA) in three patients undergoing da Vinci SP® submucosal dissection. The impact of innovation is the evaluation of a flexible suction irrigator during endorobotic submucosal dissection (ERSD), addressing space constraints and enhancing surgical precision. This was a single-center retrospective observational study involving three patients who underwent ERSD, between February 2023 and May 2023. ROSI™ was used selectively for rectal lesions. The first patient was a 67-year-old male with a 30 mm tubulovillous adenoma found in the rectum at 4 cm. The second patient was a 49-year-old female, referred after a screening colonoscopy, with a 40 mm rectal mass 12 cm from the anal verge. A biopsy revealed a tubular adenoma without dysplasia. The last patient was a 66-year-old male with a 25 mm tubulovillous adenoma with a focal high-grade dysplasia at 10 cm. There was no evidence of invasive carcinoma or lymph node metastasis on MRI in any of the patients. The patients were placed in a modified lithotomy position, and the GelPOINT® Path was inserted. A silk suture was attached at the proximal end of ROSI™ to facilitate tubing manipulation. ROSI™ was freely passed into the endoluminal space through the gel using a surgical clamp. Any bleeding during the operation was aspirated and irrigated using ROSI™ with the assistance of bipolar forceps. All surgeries were completed without complications and the patients were discharged on the same day. ROSI™ is a flexible foot pedal-controlled suction irrigator that can facilitate da Vinci SP® submucosal dissection. The flexibility and controllability of ROSI in the surgeon's hand may qualify it as an essential tool for performing ERSD and possibly other TAMIS procedures.

EP392 - Different modalities used in the investigation of anorectal lesions: a case report and discussion

Abstract Introduction Endoanal ultrasound scan (EAUS) /MRI rectum followed by early open/endoscopic, resection/biopsy for histology are important to plan management of all anorectal lesions. Here, we report an incidentally found inter-sphincteric lesion investigated with both EAUS and MRI scans, followed by excision. Case report A 55-year-old patient presented with post-menopausal bleeding and was investigated with an MRI pelvis which confirmed the causative subserosal fibroid. An incidental 15x12 mm focal soft tissue lesion at 2 o’clock between the internal and external anal canal sphincters was also picked up by the consultant GI radiologist. Her colonoscopy was normal but her digital rectal examination revealed a palpable submucosal elongated pea shaped lump at 2 o’clock. A lower GI specialist nurse performed an EAUS which suggested the lesion to be at 10 o’clock. At examination under anaesthetic (EUA), the mass in the inter-sphincter anal canal was confirmed at 2 o’clock, and excised after careful dissection from its intersphincteric location; histology confirmed a leiomyoma. The patient recovered well from the procedure. Discussion MRI and endoanal ultrasound are key imaging modalities in the diagnosis of rectal masses. EAUS provides more accurate assessment of depth of tumour invasion compared to MRI, and its relation to the anal sphincters; however, the scans are highly operator-dependent, as we found, and need to be interpreted with the benefit of clinical examination. Conclusion MRI and EAUS are complimentary in investigating rectal masses; however clinical examination, (especially under anaesthetic), as well as histology, gives the best information to plan subsequent management of common and unusual lesions (such as this) in the anorectum.

Early Symptom Patterns by Tumor Laterality, Age at Onset, Stage, and Symptom-to-Treatment Initiation in Patients with Colorectal Cancer.

In Indonesia incidence of colorectal cancer (CRC) remains high. Information about early symptoms that can offer clinicians insights for timely diagnosis, prompt referral and quick treatment decisions is very limited. This study aims to examine the pattern of CRC early symptoms and its association with tumor laterality, age at onset, metastatic status, and symptom-to-treatment initiation (STI) duration and delay. This cross-sectional study recruits 258 patients diagnosed with CRC between November 2022 and October 2023 from two distinct study databases. Patient baseline characteristics were also obtained from medical records and through interviews at baseline. Symptom-to-treatment initiation (STI) duration was defined as the number of days between the date of the symptom's onset and the date of the first treatment's initiation. Relative risk estimation for metastatic disease and the STI delay, based on tumor laterality and the age at onset group, were estimated using a log-binomial regression for each early symptom. Experiencing abdominal mass as an early symptom is significantly associated with metastatic disease, specifically in right-sided CRC cases (relative risk/RR=2.08, 95% confidence interval/CI 1.29-3.37, p=0.003). In all study subjects, the median STI duration was 182 days (2-5,082 days), with more than half of the subjects experiencing an STI delay of >180 days. Experiencing rectal mass as an early symptom is significantly associated with a higher risk of STI delay >180 days in early onset CRC (RR=1.97, 95% CI 1.27-3.06, p=0.003) and left sided-CRC cases (RR=1.54, 95% CI 1.13-2.08, p=0.005). The non-specific early symptom of weight loss is associated with a higher risk of STI delay >180 days in right-sided CRC cases (RR=1.73, 95% CI 1.06-2.84, p=0.029). The findings underlined the importance of maintaining a high clinical suspicion, particularly in patients with rectal masses and unexplained weight loss, as they might experience STI delay.

Pyrites: A Rectal Mass.

Pyrites: A Rectal Mass.

Can Puborectalis Muscle and Abdominal Subcutaneous Adipose Tissue Thickness Indicate Dyssynergic Defecation?

Introduction: Chronic constipation (CC) is a common issue in primary care and gastroenterology. Defined variably by patients and clinicians, CC per Rome III criteria requires symptoms for six months, present three or more days per month for three months. Dyssynergic defecation (DD), a functional constipation type, involves the failure of pelvic floor muscles to relax during defecation. This study examines the relationship between DD, puborectalis muscle thickness, and subcutaneous adipose tissue thickness via MR defecography. Material and Method: After ethical approval, MR defecography images of 110 patients from Ankara Bilkent City Hospital were analyzed retrospectively. Exclusions included pelvic floor descensus, rectal mass, cystocele, rectocele, or movement artifacts. The study comprised 52 DD patients and 52 matched controls. Measurements of subcutaneous adipose tissue at L5-S1 and puborectalis muscle thickness were performed on T2-weighted images. Results: DD patients had significantly higher abdominal subcutaneous adipose tissue and puborectalis muscle thickness than controls (p=0.021, p=0.001). No significant gender differences were noted. ROC analysis revealed cut-off values of 23 mm for adipose tissue and 4.8 mm for puborectalis muscle thickness. Positive predictive values for DD were 62% for adipose tissue >23 mm, 74% for puborectalis muscle thickness >4.8 mm, and 90% for both criteria. Discussion: MR defecography is essential for diagnosing DD. This study is the first to investigate the link between DD and puborectalis muscle thickness. Increased abdominal subcutaneous adipose tissue suggests a connection between DD and obesity, possibly due to increased intra-abdominal pressure leading to higher puborectalis muscle tone. Conclusion: Puborectalis muscle thickness >4.8 mm and abdominal subcutaneous adipose tissue thickness >23 mm are key parameters for diagnosing DD in MR defecography. These findings underscore the importance of MR defecography in diagnosing and understanding DD, leading to more precise and individualized treatments.

Risk factors and molecular epidemiology of intestinal colonization by carbapenem-resistant Gram-negative bacteria in patients with hematological diseases: a multicenter case‒control study.

Patients with hematological diseases are considered to be at high risk for intestinal colonization by carbapenem-resistant Gram-negative bacteria (CR-GNB). However, the epidemiological data regarding risk factors and molecular characteristics of intestinal colonized CR-GNB isolates in this population are insufficient in China. A multicenter case‒control study involving 4,641 adult patients with hematological diseases from 92 hospitals across China was conducted. Following culture of collected rectal swabs, mass spectrometry and antimicrobial susceptibility tests were performed to identify GNB species and CR phenotype. Risk factors were assessed through retrospective clinical information. Whole-genome sequencing was used to analyze the molecular characteristics of CR-GNB isolates. This trial is registered with ClinicalTrials.gov as NCT05002582. Our results demonstrated that among 4,641 adult patients, 10.8% had intestinal colonization by CR-GNB. Of these, 8.1% were colonized by carbapenem-resistant Enterobacterales (CRE), 2.6% were colonized by carbapenem-resistant Pseudomonas aeruginosa (CRPA), and 0.3% were colonized by carbapenem-resistant Acinetobacter baumannii (CRAB). The risk factors for CR-GNB colonization include male gender, acute leukemia, hematopoietic stem cell transplantation, β-lactam antibiotic usage, and the presence of non-perianal infections within 1 week. Compared with CRPA-colonized patients, patients using carbapenems were more likely to be colonized with CRE. NDM was the predominant carbapenemase in colonized CRE. This study revealed a high CR-GNB intestinal colonization rate among adult patients with hematological diseases in China, with CRE being the predominant one. Notably, a significant proportion of CRE exhibited metallo-β-lactamase production, indicating a concerning trend. These findings emphasize the importance of active screening for CR-GNB colonization in patients with hematological diseases.IMPORTANCECarbapenem-resistant Gram-negative bacteria (CR-GNB) has emerged as a significant threat to public health. Patients with hematological diseases are at high risk of CR-GNB infections due to their immunosuppressed state. CR-GNB colonization is an independent risk factor for subsequent infection. Understanding the risk factors and molecular characteristics of CR-GNB associated with intestinal colonization in patients with hematological diseases is crucial for empirical treatment, particularly in patients with febrile neutropenia. However, the epidemiology data are still insufficient, and our study aims to determine the intestinal colonization rate of CR-GNB, identify colonization risk factors, and analyze the molecular characteristics of colonized CR-GNB isolates.

An unusual case of rectal schwannoma: A case report

Rectal schwannomas, although exceedingly rare, represent an intriguing and often perplexing diagnostic challenge in the field of gastroenterology. Here, we are presenting an interesting case of rectal mass in a 66-years-old Bahraini male who has a known case of irritable bowel and presented with symptoms of fullness in the right iliac fossa region accompanied by recurrent episodes of constipation. A large upper rectal mass was identified in imaging studies; however, obtaining a biopsy was difficult using sigmoidoscopy three times; hence, the patient eventually underwent an exploratory laparoscopy with colectomy. Pathologist confirmed the diagnosis of schwannoma. This captivating case study unravels the enigma surrounding a unique encounter with rectal schwannoma. In addition, we represent an enlightening case that widens our differential diagnosis in investigating mesenchymal tumors of the gastrointestinal tract with emphasis on its clinical presentation, diagnostic nuances, and therapeutic consideration.

Diagnostic Ability of Ultrasonography Compared with Computed Tomography for Assessing Rectal Feces.

Chronic constipation is a common gastrointestinal disorder, and management is crucial. Computed tomography (CT) is useful for evaluating rectal fecal mass but limited owing to radiation exposure, cost, and inaccessibility at certain facilities. Ultrasonography (US) avoids these pitfalls, but it is unknown whether it accurately assesses rectal feces. In this study, we evaluated the diagnostic performance of US compared with CT as the gold standard for assessing rectal feces. We prospectively evaluated rectal fecal mass retention using US performed within 1 h of CT to assess the degree of agreement between methodologies. Rectal stool findings were evaluated on three levels: no stool (R1), presence of stool (R2), and hard stool filling (R3). The sample included 100 patients (55 men, 45 women), of whom 47 were constipated. The kappa coefficients for rectal content detection were excellent between US and CT (p <0.001). Eighty-two cases (R1: 46 cases; R2: 28 cases; R3: 8 cases) were matched with CT and US findings, and 18 were not. Cases that did not match had low urine or high gas volumes. CT and US findings showed high agreement in constipation (kappa coefficient 0.674, p <0.001) and non-constipation groups (kappa coefficient 0.677, p <0.001). All cases with R3 on CT were found in the constipation group, while more than half of the cases with R1 on CT were in the non-constipation group. CT and US showed high agreement in evaluating rectal fecal mass retention, indicating that US can substitute CT.

Laser Hemorrhoidoplasty Using Reusable Bare Fiber Combined Mucopexy on Grade IV Internal Hemorrhoid: A Case Report

Background: Hemorrhoids are the most common anorectal disease, affecting millions worldwide. Hemorrhoids are categorized as "internal" or "external" based on their proximity to the pectinate line, which separates the upper 2/3 and lower 1/3 of the anus. The hemorrhoidal disease can be treated in various ways, from non-invasive methods like rubber band ligation, cryotherapy, sclerotherapy, laser photocoagulation, and phototherapy to invasive methods like surgical excision for patients with severe symptoms, grade III or IV hemorrhoids, or persistent bleeding. This study described the results of Laser Hemorrhoidoplasty (LHP) using reusable bare fiber combined mucopexy, a diode laser with wavelengths of 980 nm and 1470 nm, specifically gallium aluminum arsenide (GaAIAs). Methods: a case of a 28-year-old male with complaints of rectal prolapse mass one day ago and could not be reinserted with a finger, bleeding while passing stool, and rectal pain with a Visual analog scale was 7. The patient had experienced similar symptoms and had a sclerobanding procedure four years ago. However, it has reappeared in the past year. The patient was diagnosed with grade 4 internal hemorrhoids and underwent Conclusion: Laser hemorrhoidoplasty using reusable bare fiber with combined mucopexy. After the laser hemorrhoidoplasty procedure on day 4, the patient felt no pain, rectal bleeding, rectal lumps, or soiling.

Rectal malakoplakia simulating a locally advanced rectal cancer: a case report

Malakoplakia is a rare and chronic granulomatous disease, resulting from the accumulation of large granular macrophages containing basophilic inclusion bodies in the cytoplasm named Michaelis-Gutmann bodies. The gastrointestinal tract is the second most common site after the urinary tract, though malakoplakia has the potential to manifest in multiple organs. Rectal malakoplakia is difficult to diagnose due to its unspecific clinical and radiological presentation, usually mimicking a malignancy. Most report cases are associated with immunosuppressive diseases or chronic prolonged illness. We present the case of a 64-year-old male with a history of anal pain. A pelvic magnetic resonance imaging showed a rectal mass with 38 mm invading the mesorectum. Colonoscopy was performed confirming a mass-like lesion and biopsies were taken. Histopathological examination revealed features consistent with malakoplakia. The patient underwent long-term oral antibiotic treatment and during follow-up there was a regression of the lesion and resolution of symptoms.

Syphilitic proctitis: review of the literature.

Syphilitic proctitis is a rare sexually transmitted disease caused by spirochete pallidum infecting the rectal mucosa. It usually has no specific clinical manifestations and is easily misdiagnosed with other rectal and anal diseases such as rectal cancer, malignant lymphoma, inflammatory bowel disease, etc.. Therefore, diagnosis of the disease is difficult and treatment options are often unreasonable. A case of syphilitic proctitis in our hospital with "rectal mass" as the main manifestation is reported as follows and relevant literature is reviewed. At the same time, we studied and analyzed the clinical and histological characteristics and differential diagnosis of syphilitic proctitis to further deepen the understanding of this disease.

Endometriosis with colonic mucosal colonisation: a diagnostic confounder.

Secondary mucosal colonisation by a carcinoma originating from a distant site is a pattern of metastasis to the intestines and hepatobiliary tract and a mimic of primary neoplasia. Although endometriosis is considered benign, its ability to spread widely underscores its quasi-neoplastic nature. After noting that endometriotic glands can colonise the colonic mucosa along the basement membrane, mimicking metastatic disease, we conducted an intradepartmental review of intestinal specimens showing endometriosis obtained from 2016 to 2023 to characterise and quantify the incidence of this phenomenon. Material from 38 lower gastrointestinal specimens with a primary or ancillary diagnosis of endometriosis was identified from our surgical pathology database. Slides were reviewed, documenting the extent and micro-anatomic location affected by endometriosis, with a focus on identifying examples showing mucosal colonisation. The most common site of involvement was the distal colon (23 cases; 11 of rectum, 9 of sigmoid colon and 3 of rectosigmoid) followed by the appendix (N=10), cecum (N=2), small intestine (N=2) and 'colon not otherwise specified' (N=1). Mucosal involvement was identified in eight cases (21%), half of which demonstrated seamless colonisation of the epithelium by endometriotic glands. In two of these, the procedure was prompted by the presence of a rectal mass or stricture with concern for malignancy. Endometriosis occasionally (4/38; 10.5%) colonises colonic epithelium, potentially mimicking a metastasis or intraepithelial neoplasia/dysplasia. Although unusual, this phenomenon was observed in half of specimens from patients with mucosal involvement in whom a mass or stricture suggested malignancy, a potentially misleading pattern of endometriosis.

HIV Associated Kaposi’s Sarcoma with Visceral Involvement and Rectal Bleeding

Abstract Introduction/Objective Kaposi’s sarcoma (KS) is one of the complications of advanced HIV disease and human herpes virus 8 (HHV-8) is the etiological agent. Most cases of KS are cutaneous and resolved with HIV treatment, few cases of KS present with visceral involvement and have a poor prognosis. Any part of the gastrointestinal tract (GIT) may be affected by KS, however visceral involvement without cutaneous lesions is extremely rare. KS has metastatic potential and can be fatal if treatment is not initiated immediately. Methods/Case Report A 29 years old homosexual man with a history of multiple sexually transmitted diseases and HIV infection (CD4: 331 cell/μL, CD4/CD8: 0.2, HIV RNA: 10542 copies/mL) presented to the emergency department in a hypovolemic state with hemoglobin of 6 g/dl. He received HAART 3 years ago but discontinued it due to the COVID pandemic. He had a history of recurrent and intermittent rectal bleeding which was exacerbated during the past 3 months. On physical examination, a bleeding rectal mass and bilateral inguinal adenopathy were noted. An imaging study was performed and showed a 14 cm anorectal mass extruding through the anal canal, with bilateral axillary, inguinal, pelvic side walls, iliac chains, and periaortic lymphadenopathy. Flow cytometry of the fresh biopsy tissue revealed a T cell-predominant lymphoid population with reversed CD4/CD8 ratio, compatible with the patient's known history of HIV, with no immunophenotypic evidence of lymphoma. Histopathologic examination of an excisional biopsy of the rectal mass showed mild to moderate atypical spindle cells arranged in vague fascicles and separated by slit-like vessels and extravasated red blood cells. Immunohistochemical (IHC) stain revealed the atypical spindle cells were positive for HHV-8, CD31, CD34, D2-40, BCL2, Vimentin, and Ki-67 (35%-highly proliferative) whereas these cells were negative for AE1/AE3, CK5/6, P40, CD45, Desmin, and S100. A diagnosis of KS was made. Results (if a Case Study enter NA) NA Conclusion We present a case of visceral KS without cutaneous involvement, which may pose a difficulty in diagnosis. The GIT, lungs, and lymph nodes are the relatively common sites that are affected by visceral KS. KS manifests various histopathological and clinical pictures, and a delay in diagnosis can cause a worse prognosis. The treatment options for KS are depending on the clinical presentation and the extension of the lesions. A combination of HAART, chemotherapy, and radiotherapy could be an effective treatment in the early stage of the disease.

Low Rectal Cancers at Initial Staging MRI.

Low rectal cancers, which are associated with increased risk of local recurrent disease and poorer prognosis, have unique anatomic considerations and issues for staging and treatment that do not apply to mid and high rectal cancers. Although tumor histology help drive the staging and treatment of all rectal cancers, it is of particular importance in low rectal cancers, which may involve the anal canal, to help establish whether a low rectal mass should be staged and treated as a rectal cancer (ie, adenocarcinoma) or an anal cancer (ie, squamous cell carcinoma). Optimal staging and treatment of rectal cancer are contingent on tumor location and local extent, which help guide management decisions including neoadjuvant therapy and curative surgical treatment strategies. Tumor location in the low rectum and local involvement of the anal canal, sphincter, and pelvic floor help determine whether a patient can undergo sphincter-preserving resection such as a low anterior resection versus abdominoperineal resection to achieve negative surgical margins. Issues exist related to the anatomy and patterns of disease spread that are unique to the low rectum and include how to determine and stage anal sphincter involvement, mesorectal fascia status at the pelvic floor, and nodal status of extramesorectal nodes such as the external iliac and inguinal lymph nodes. For these reasons, it is imperative that radiologists who interpret rectal cancer staging MRI examinations feel comfortable with the unique anatomy of the low rectum and anal canal, nuances of low rectal cancer local disease spread, and treatment paradigms for low rectal cancer. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Gollub in this issue.

Iatrogenic Rectal Mass After Prostate Cancer Treatment

Iatrogenic Rectal Mass After Prostate Cancer Treatment