MRI of rectal disorders

Watch and wait approach in rectal cancer: Current controversies and future directions

According to the main international clinical guidelines, the recommended treatment for locally-advanced rectal cancer is neoadjuvant chemoradiotherapy followed by surgery. However, doubts have been raised about the appropriate definition of clinical complete response (cCR) after neoadjuvant therapy and the role of surgery in patients who achieve a cCR. Surgical resection is associated with significant morbidity and decreased quality of life (QoL), which is especially relevant given the favourable prognosis in this patient subset. Accordingly, there has been a growing interest in alternative approaches with less morbidity, including the organ-preserving watch and wait strategy, in which surgery is omitted in patients who have achieved a cCR. These patients are managed with a specific follow-up protocol to ensure adequate cancer control, including the early identification of recurrent disease. However, there are several open questions about this strategy, including patient selection, the clinical and radiological criteria to accurately determine cCR, the duration of neoadjuvant treatment, the role of dose intensification (chemotherapy and/or radiotherapy), optimal follow-up protocols, and the future perspectives of this approach. In the present review, we summarize the available evidence on the watch and wait strategy in this clinical scenario, including ongoing clinical trials, QoL in these patients, and the controversies surrounding this treatment approach.

Multimodality Imaging Review of Anorectal and Perirectal Diseases With Histological, Endoscopic, and Operative Correlation, Part I: Anatomy and Neoplasms

A broad spectrum of pathology affects the rectum, anus, and perineum and understanding of its relevant anatomy is important in accurate reporting, particularly in rectal cancer. In this pictorial essay, correlative imaging, endoscopic, pathologic, and operative images are presented to illustrate normal anorectal anatomy and neoplastic conditions that affect the anus and rectum. A particular case-based focus is given to rectal adenocarcinoma with pelvic MR and surgical histopathology. Additionally, carcinoid tumor, gastrointestinal stromal tumor, condylomata acuminata, squamous cell carcinoma, melanoma, and metastatic disease about the rectum and anus are reviewed.

The bottom line: MRI and CT findings of unusual rectal and perirectal pathology

Although common nonspecific symptoms (i.e., rectal bleeding, pelvic pressure, and change in bowel habits) are associated with rectal cancer, occasionally these are related to a different underlying disease. Over the past few years, considerable progress has been made in imaging of the rectum. Specifically, new magnetic resonance techniques and capabilities provide impressive high-resolution assessment of the rectal wall and enable evaluation and characterization of the perirectal tissues. This paper reviews imaging findings of uncommon causes of rectal and perirectal pathology that may be clinically confounded with rectal cancer. Radiologists need to be aware of uncommon pathologies in this region in order to facilitate optimal management decisions.

What is hiding in the hindgut sac? Looking beyond rectal carcinoma

Objectives

Although rectal cancer is by far and large the most common pathology involving the rectum that needs imaging, there are many other important but less common pathological conditions affecting anorectal region. The objective of this pictorial review is to discuss the cross-sectional imaging features of less common anorectal and perirectal diseases.

Results

Although a specific histological diagnosis cannot usually be made due to considerable overlap in the imaging appearances of anorectal diseases, this review illustrates the cross-sectional imaging findings with emphasis on magnetic resonance imaging (MRI) that can help in narrowing down the differentials to a reasonable extent.

Teaching points

• Variety of pathology exists in the anorectum apart from common rectal carcinoma

• Anorectal diseases present as non-specific wall thickening indistinguishable from rectal carcinoma

• Computed tomography (CT) and MRI can help in narrowing down the differentials, although often biopsy is warranted.

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.

MR imaging features of nongynaecologic cystic lesions of the pelvis

OBJECTIVE

The purpose of our article is to review the magnetic resonance imaging (MRI) features of nongynaecologic cystic lesions of the pelvis.

CONCLUSION

The rising use of MRI for pelvic exploration will result in an increase in incidental detection of pelvic cystic cysts. Pelvic cysts of non gynecologic origin are less frequent than gynecologic cysts. However, they account for a wide range of abnormalities, and radiologists must be aware of their features and characteristics.

Anorectal opportunistic diseases in human immunodeficiency virus/acquired immunodeficiency syndrome patients: spectrum of cross-sectional imaging findings

Patients infected with the human immunodeficiency virus, particularly male homosexuals, are prone to develop disorders involving the anorectal and perineal structures. Cross-sectional imaging techniques, such as multidetector computed tomography with multiplanar reformations and magnetic resonance imaging performed with phased-array coils, are increasingly adopted to detect and stage infectious and neoplastic diseases, and to assess posttreatment modifications. Pyogenic perianal sepsis may be usefully investigated with imaging, particularly to assess the presence and topography of abscess collections to allow a correct surgical choice. Rectal inflammatory involvement is frequently detected during intestinal opportunistic infections, such as cytomegalovirus, pseudomembranous, and amebic colitides, including primary and secondary imaging signs consistent with proctocolitis. Anal carcinoma and intestinal lymphoma are increasingly diagnosed; therefore, special attention should be paid to the identification of solid tissue consistent with tumor; furthermore, MRI provides optimal staging and posttreatment follow-up of neoplastic lesions. Knowledge of this varied spectrum of anorectal and perineal opportunistic abnormalities and their imaging appearances should help radiologists to propose appropriate differential diagnoses, suggest correlation with laboratory and microbiological assays or biopsy, and reliably assess therapeutic response.

MRI and CT of anal carcinoma: a pictorial review

BACKGROUND

Squamocellular anal carcinoma is increasingly diagnosed in patients with risk factors.

METHODS

State-of-the-art imaging with magnetic resonance imaging (MRI) using phased-array coils and volumetric multidetector computed tomography (CT) provides detailed visualisation of anal disorders, identification and extent assessment of neoplastic tissue, detection and characterisation of nodal and visceral metastases. MRI has been recommended by the European Society for Medical Oncology (ESMO) as the preferred modality of choice to stage anal cancer, taking into account the maximum tumour diameter, invasion of adjacent structures and regional lymph node involvement.

RESULTS

Cross-sectional imaging techniques allow the identification of coexisting complications, and differentiation from other perineal abnormalities.

CONCLUSION

Cross-sectional imaging is useful for planning radiotherapy, surgical drainage or salvage abdomino-perineal resection. After chemo-radiotherapy, MRI follow-up provides confident reassessment of therapeutic response, persistent or recurrent disease. TEACHING POINTS : • Anal carcinoma is increasingly diagnosed in patients with human immunodeficiency virus (HIV), anoreceptive intercourse, chronic inflammatory bowel disease. • An established association exists with human papillomavirus (HPV) infection and premalignant intra-epithelial dysplasia. • Phased-array MRI is recommended as the preferred imaging modality for regional staging. • Imaging allows detection of infectious complications, planning of radiotherapy or salvage surgery. • Follow-up MRI allows reliable assessment of therapeutic response after chemo-radiotherapy.

[3.0T MRI with a high resolution protocol for the study of benign disease of the anus and rectum. Part 2: Anorectal inflammatory disease. Postsurgical anatomy and complications after treatment]

Benign anorectal disease comprises a broad group of processes with very diverse origins; these processes may be congenital or acquired as well as inflammatory or tumor related. However, benign anorectal disease has received less attention in the scientific literature than malignant disease. In this second part of this image-based review of benign anorectal disease, we describe the most common inflammatory and fistulous diseases, the postsurgical anatomy, and complications that can occur after surgical treatment or radiotherapy for anorectal disease.

[3.0 T MRI with a high resolution protocol for the study of benign disease of the anus and rectum. Part one: High resolution protocol for 3.0 T MRI, anatomic review, benign tumors, and congenital or acquired alterations of the sphincter complex]

Benign anorectal disease comprises a broad group of processes with very diverse origins; these processes may be congenital or acquired as well as inflammatory or tumor related. However, benign anorectal disease has received less attention in the scientific literature than malignant disease. We present an image-based review of the most common benign diseases of the anus and rectum. In this first part, we review the anatomy of the region and provide a brief description of the peculiarities of the high resolution protocol that we use with 3.0 T MRI. We go on to describe the most common benign anorectal tumors and developmental cystic lesions, together with their differential diagnoses, as well as congenital and acquired anomalies of the anorectal sphincter complex.

Diffusion-weighted imaging of the rectosigmoid colon: preliminary findings

OBJECTIVES

The aims of this study were to determine and evaluate the apparent diffusion coefficient (ADC) values of the rectal wall for identifying inflammatory bowel disease (IBD) and rectosigmoid (rectum and sigmoid colon) malignancies.

METHODS

Diffusion-weighted magnetic resonance imaging (DWI) findings of 23 patients (mean age, 57 years) consisting of 14 patients with rectosigmoid adenocarcinomas and 9 patients with IBD (6 with ulcerative colitis and 3 with Crohn disease) were retrospectively reviewed. In addition, 30 healthy controls (mean age, 45 years) were enrolled in the study. Diffusion-weighted imaging was performed with b factors of 0, 500, and 1000 s/mm2.

RESULTS

The mean (SD) ADC values of the control, IBD, and rectosigmoid adenocarcinoma groups were 1.47 (0.19) x 10(-3) mm2/s, 1.37 (0.12) x 10(-3) mm2/s, and 0.97 (0.14) x 10(-3) mm2/s, respectively. Among the patients with IBD, 2 were in the active, and the rest were in the inactive period, with mean (SD) ADC values of 1.21 (0.08) x 10(-3) and 1.42 (0.09) x 10(-3), respectively. The ADC values of the normal rectum and rectosigmoid malignancy group and rectosigmoid carcinoma and IBD groups were significantly different (P < 0.01). A cutoff value for carcinomas of 1.14 x 10(-3) mm2/s yielded a sensitivity and specificity of 93.3% and 93.3%, respectively.

CONCLUSIONS

Our preliminary findings show that quantitative DWI may be able to differentiate the normal rectum from neoplastic involvement, in addition to distinguishing between inflammatory and neoplastic involvements. However, radiologists should be aware of possible overlaps that may lead to misdiagnoses when DWI is used alone.