Abstract
Objective: MRI is currently the imaging modality of choice for the detection, characterization, and staging of rectal cancer. A variety of examinations have been used for preoperative staging of rectal cancer, including digital rectal examination, endorectal (endoscopic) ultrasound, CT, and MRI. Endoscopic ultrasound is the imaging modality of choice for small and small superficial tumors. MRI is superior to CT for assessing invasion to adjacent organs and structures, especially low tumors that carry a high risk of recurrence. Background: Colorectal cancer (CRC) is the third most common cancer in both sexes combined worldwide, after prostate and breast cancer with an incidence of 40 in 100,000. Rectal carcinoma accounts for more than one-third of colorectal tumors and is associated with significant morbidity and mortality. Currently, MRI using diffusion weighted sequence is the most sensitive and specific modality in staging rectal cancer as it is able to depict the mesorectal fascia and its relation to the tumor margins precisely. Methods: This study included 50 patients, (32 male and 18 female) previously diagnosed as cancer rectum based on proctoscope and histopathological biopsy. The age range of the patients was from 18 years to 78 years. All patients will be subjected to the following: detailed history, clinical examination, proctoscopic assessment and histopathological data. All patients underwent MRI of the pelvis specifically cancer rectum protocol. Results: The most frequently encountered clinical presentation among cancer rectum patients was bleeding per rectum (14), constipation (26), incidentally discovered liver metastasis (6) and intestinal obstruction (4). MRI evaluation of T staging in correlation to the histopathological examination showed sensitivity (80%), specificity (93%), accuracy (94%). Lymph node (LN) metastatic spread was evaluated by MRI and showed sensitivity (87%), specificity (92%), accuracy (92.6%), PPV (84.8%) and NPV (96.7%). Regarding circumferential resection margin (CRM) MRI assessment revealed; sensitivity (96%), specificity (94%), accuracy (96%), PPV (95%) and NPV (94.3%). Conclusions: MRI is an accurate and sensitive imaging method delineating tumoral margins, mesorectal fascia involvement, lymph nodes, and distant metastasis. MRI can accurately delineate the mesorectal fascia involvement, which is one of the main decision points in planning treatment.
Highlights
Colorectal carcinoma is the third most common cancer among both sexes combined worldwide, after prostate and breast cancer with an incidence of 40 per 100,000 [1]
To identify and stage rectal cancers with MRI, high resolution T2-weighted image with thin-sections is the primary approach used to differentiate between the tumor, mucosal, submucosal layers, muscular layer, perirectal fat and mesorectal fascia (MRF) [5, 6]
The fifty patients included in this study showed different pathological types of cancer rectum, 23 patients were diagnosed as adenocarcinoma, 22 as mucinous carcinoma while the tumor was undifferentiated in 5 patients
Summary
Colorectal carcinoma is the third most common cancer among both sexes combined worldwide, after prostate and breast cancer with an incidence of 40 per 100,000 [1]. MRI is the most sensitive and specific modality in staging rectal cancer as it is able to precisely depict the mesorectal fascia relation to the tumor margins due to its superior spatial and tissue contrast resolution [4]. To identify and stage rectal cancers with MRI, high resolution T2-weighted image with thin-sections is the primary approach used to differentiate between the tumor, mucosal, submucosal layers, muscular layer, perirectal fat and mesorectal fascia (MRF) [5, 6]. The second is to allow prognostic stage grouping. Prognostic stratification includes assessment of depth of spread, nodal status, extramural vascular invasion (EMVi), CRM and peritoneal invasion [8].
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