Accuracy of routine nontargeted CT without colonography technique for the detection of large colorectal polyps and cancer

Expert Panel on Gastrointestinal Imaging, Thomas DE, Horvat N, Fowler KJ, Birkholz JH, Cash BD, Dane B, Dbouk RH, Hanna N, Hurley J, Korngold EK, Pietryga JA, Yeghiayan P, Zell JA, Zreloff J, Kim DH. ACR Appropriateness Criteria® Colorectal Cancer Screening: 2024 Update

This document serves to update the 2018 ACR Appropriateness Criteria® colorectal screening guidance document. In light of new recommendations from the US Preventative Services Task Force (USPSTF), an updated literature review of the imaging procedures for the screening of colorectal cancer was performed. Average-risk, elevated-risk, and high-risk individuals as well as those individuals who had an incomplete colonoscopy or were unable to tolerate colonoscopy were included. CT colonography without contrast was found to be usually appropriate for individuals at average and elevated risk between 45 to 75 years of age at initial screening. Additionally, CT colonography without contrast was found to be usually appropriate in individuals at average risk, elevated risk, and at high risk after incomplete colonoscopy or unable to tolerate colonoscopy. Other imaging procedures such as barium fluoroscopy and CT of the abdomen and pelvis were usually not appropriate. CT colonography without contrast, barium fluoroscopy, and CT of the abdomen and pelvis were usually not appropriate in high-risk individuals who can undergo a complete colonoscopy. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Artificial Intelligence Model for Detection of Colorectal Cancer on Routine Abdominopelvic CT Examinations: A Training and External-Testing Study

BACKGROUND. Radiologists are prone to missing some colorectal cancers (CRCs) on routine abdominopelvic CT examinations that are in fact detectable on the images. OBJECTIVE. The purpose of this study was to develop an artificial intelligence (AI) model to detect CRC on routine abdominopelvic CT examinations performed without bowel preparation. METHODS. This retrospective study included 3945 patients (2275 men, 1670 women; mean age, 62 years): a training set of 2662 patients from Severance Hospital with CRC who underwent routine contrast-enhanced abdominopelvic CT before treatment between January 2010 and December 2014 and internal (841 patients from Severance Hospital) and external (442 patients from Gangnam Severance Hospital) test sets of patients who underwent routine contrast-enhanced abdominopelvic CT for any indication and colonoscopy within a 2-month interval between January 2018 and June 2018. A radiologist, accessing colonoscopy reports, determined which CRCs were visible on CT and placed bounding boxes around lesions on all slices showing CRC, serving as the reference standard. A contemporary transformer-based object detection network was adapted and trained to create an AI model (https://github.com/boktae7/colorectaltumor) to automatically detect CT-visible CRC on unprocessed DICOM slices. AI performance was evaluated using alternative free-response ROC analysis, per-lesion sensitivity, and per-patient specificity; performance in the external test set was compared with that of two radiologist readers. Clinical radiology reports were also reviewed. RESULTS. In the internal (93 CT-visible CRCs in 92 patients) and external (26 CT-visible CRCs in 26 patients) test sets, AI had AUC of 0.867 and 0.808, sensitivity of 79.6% and 80.8%, and specificity of 91.2% and 90.9%, respectively. In the external test set, the two radiologists had sensitivities of 73.1% and 80.8% (p = .74 and p > .99 vs AI) and specificities of 98.3% and 98.6% (both p < .001 vs AI); AI correctly detected five of nine CRCs missed by at least one reader. The clinical radiology reports raised suspicion for 75.9% of CRCs in the external test set. CONCLUSION. The findings show the AI model's utility for automated detection of CRC on routine abdominopelvic CT examinations. CLINICAL IMPACT. The AI model could help reduce the frequency of missed CRCs on routine examinations performed for reasons unrelated to CRC detection.

Straight-to-Test Pathway in Faecal Immunochemical Testing (FIT)-Negative Patients: A Cost-Effective Approach

INTRODUCTION

Colorectal cancer (CRC) is the fourth most common malignancy in the UK and represents a high-volume diagnostic and clinical burden on the National Health Service (NHS). To maximise the use of limited diagnostic resources and increase efficiency, the colorectal services at University Hospitals North Midlands Trust (UHNM) developed the triage-to-test (TTT) service with risk stratification for diagnostic testing in patients with suspected colorectal cancer using faecal immunochemical testing (FIT) result. Our retrospective cohort study looked at the pick-up rate of colorectal cancer (CRC) and non-colorectal cancer (non-CRC) in FIT-negative patients.

METHODS

The study was a retrospective review of all symptomatic patients over 18 years of age who had undergone FIT testing in the community between 1 November 2021 and 11 February 2022 and who were referred directly to the UHNM colorectal pathway from primary care (n=2,374). FIT negativity was set at <9.9 μg/g of faeces, as per the National Institute for Health and Care Excellence (NICE) DG30 guidelines. Patients were investigated and risk stratified in accordance with their FIT result and presenting symptoms.

RESULTS

About 61.5% of patients referred were FIT negative (n=1,459) and 38.5% were FIT positive (n=915). Of those FIT-negative patients, 82 were excluded as their clinical outcomes were pending at the time of analysis. FIT positivity conferred a greater likelihood of colorectal cancer when compared with FIT-negative patients (p<0.0001). FIT-negative patients were most likely to have no significant pathology (32.5%, n=474). Incidence of colorectal cancer in the FIT-negative group was 0.5% (n=7) compared with 9.8% (n=89) in the FIT-positive group (odds ratio: 5.252, 95% CI: 4.012-6.875). Within the FIT-negative cohort, five patients were diagnosed with rectal cancer, one proximal descending colon cancer and one caecal cancer.

CONCLUSION

The use of a FIT-negative TTT pathway ensures that any symptomatic patients presenting with red flag symptoms can be investigated appropriately. It also provides reassurance to clinicians who have an ethical duty to investigate patients in whom they suspect sinister pathology. Moreover, a triage-to-Test pathway reduces outpatient capacity burden on healthcare trusts as they may send patients directly for investigation.

Deep learning for colorectal cancer detection in contrast-enhanced CT without bowel preparation: a retrospective, multicentre study

BACKGROUND

Contrast-enhanced CT scans provide a means to detect unsuspected colorectal cancer. However, colorectal cancers in contrast-enhanced CT without bowel preparation may elude detection by radiologists. We aimed to develop a deep learning (DL) model for accurate detection of colorectal cancer, and evaluate whether it could improve the detection performance of radiologists.

METHODS

We developed a DL model using a manually annotated dataset (1196 cancer vs 1034 normal). The DL model was tested using an internal test set (98 vs 115), two external test sets (202 vs 265 in 1, and 252 vs 481 in 2), and a real-world test set (53 vs 1524). We compared the detection performance of the DL model with radiologists, and evaluated its capacity to enhance radiologists' detection performance.

FINDINGS

In the four test sets, the DL model had the area under the receiver operating characteristic curves (AUCs) ranging between 0.957 and 0.994. In both the internal test set and external test set 1, the DL model yielded higher accuracy than that of radiologists (97.2% vs 86.0%, p < 0.0001; 94.9% vs 85.3%, p < 0.0001), and significantly improved the accuracy of radiologists (93.4% vs 86.0%, p < 0.0001; 93.6% vs 85.3%, p < 0.0001). In the real-world test set, the DL model delivered sensitivity comparable to that of radiologists who had been informed about clinical indications for most cancer cases (94.3% vs 96.2%, p > 0.99), and it detected 2 cases that had been missed by radiologists.

INTERPRETATION

The developed DL model can accurately detect colorectal cancer and improve radiologists' detection performance, showing its potential as an effective computer-aided detection tool.

FUNDING

This study was supported by National Science Fund for Distinguished Young Scholars of China (No. 81925023); Regional Innovation and Development Joint Fund of National Natural Science Foundation of China (No. U22A20345); National Natural Science Foundation of China (No. 82072090 and No. 82371954); Guangdong Provincial Key Laboratory of Artificial Intelligence in Medical Image Analysis and Application (No. 2022B1212010011); High-level Hospital Construction Project (No. DFJHBF202105).

Pictorial essay: improving diagnostic effectiveness of colorectal cancer at CT

As the routine use for CT increases, there is an opportunity to increase the detection rate of unsuspected and asymptomatic colorectal cancers. This pictorial essay provides abundant examples of the typical morphologic appearances of colorectal cancer in the unprepared colorectum. Many examples of lesions that were missed in clinical practice are illustrated with lessons on how to avoid these errors. Atypical appearances of colorectal cancer are also illustrated. The overall aim is to increase the detection rate of colorectal cancer at routine CT.

A multicentre study assessing the role of routine colonoscopy after acute uncomplicated diverticulitis and the incidence of colorectal cancer diagnosis

PURPOSE

The low rates of colonic malignancy detected on interval colonoscopy for patients diagnosed with diverticulitis have led recent studies to question the utility of the practice. The aim of this study was to assess the detection rate of colorectal cancer on colonoscopy for patients with a first episode of acute uncomplicated diverticulitis across three separate centres in Ireland and the UK.

METHODS

A retrospective review was performed of patients with a first episode of acute, uncomplicated diverticulitis who underwent interval colonoscopy at three separate centres in the UK and Ireland between 2007 and 2019. The follow-up period was one year.

RESULTS

A total of 5485 patients were admitted with acute diverticulitis between the three centres. All patients had CT verified diverticulitis. A 90.8% (n = 4982) underwent subsequent colonic evaluation with colonoscopy. Of these, a histologically proven diagnosis of colorectal carcinoma was made in 1.28% (n = 64).

CONCLUSION

Routine colonoscopy following an episode of acute, uncomplicated diverticulitis may not be necessary in every patient. It may be appropriate to reserve this more invasive investigation for those with higher risk factors for malignancy.

Strategies for improving colorectal cancer detection with routine computed tomography

PURPOSE

To report the detection rate of colorectal tumors with computed tomography (CT) performed within 1 year before diagnosis for indications other than colon abnormalities. Strategies to improve cancer detection are reported.

METHODS

Two board-certified, subspecialty-trained abdominal radiologists retrospectively reviewed patient health records and CT images with knowledge of tumor location/size. Patients were classified into 3 groups: prospective (colon abnormality suggesting neoplasm documented in radiologic report), retrospective (not documented in radiologic report but detected in our retrospective review of CT images), and undetected (neither prospectively nor retrospectively detected). Retrospective detection confidence and morphologic characteristics of each tumor were also recorded.

RESULTS

Of 209 included patients, 106 (50.7%) had prospectively detected tumors, 66 (31.6%) had retrospectively detected tumors, and 37 (17.7%) had undetected tumors. Asymmetric bowel wall thickening and polypoid masses were present more often in the retrospective group than in the prospective group (27% vs. 10.5% and 26% vs. 17.1%, respectively). Tumors in the ascending colon were more likely to be detected retrospectively than prospectively (odds ratio, 2.75; 95% CI 1.07-7.08; P = 0.04). Undetected tumors were smaller on average (2.9 cm) than prospective (6.0 cm) and retrospective (4.9 cm) tumors (P = 0.03). Detection confidence was lower for retrospectively detected tumors than for prospectively detected tumors (P = 0.03). Indications other than abdominal pain were most common for retrospectively detected tumors (P = 0.03). Use of intravenous contrast material was lowest in the undetected group (P = 0.003). The prospective group had more pericolonic abnormalities, regional/retroperitoneal lymph node involvement (P < 0.001), and distant metastases than did the retrospective group (P = 0.01).

CONCLUSION

Half of all colorectal tumors were not detected prospectively. Radiologists should perform meticulous colon tracking regardless of the indication for CT. The right colon merits additional examination. Polypoid and asymmetric morphologic characteristics were most often overlooked, but these characteristics can be learned to improve detection.

Outcomes of patients with non-lower gastrointestinal cancer diagnosed via the lower gastrointestinal two-week-wait service

INTRODUCTION

Patients referred via lower gastrointestinal two-week-wait (LGI-2WW) services deemed at 'low risk' of LGI cancer may have delayed or no investigation. However, 20% of patients diagnosed with cancer via the LGI-2WW have non-LGI cancer. This study investigates the outcomes in this under-reported group.

METHODS

A retrospective analysis of patients referred to a UK LGI-2WW service with a non-LGI cancer diagnosis (International Classification of Diseases 10th revision) between 1 January 2015 and 31 December 2018. The primary outcome was all-cause mortality. Statistical analysis was undertaken using Kaplan-Meier survival curves with generalised log-rank test and binomial logistic regression of pre-investigation information to predict death. A p-value of < 0.05 represented statistical significance.

RESULTS

In total, 140 patients were diagnosed with non-LGI cancer (of 10,155 patients referred via the LGI-2WW pathway). Median follow-up was 13 months (range 0-65 months). Thirty-five patients (35/140; 25%) did not meet LGI-2WW referral criteria. Median survival varied by cancer site (upper gastrointestinal: 43/140 patients, median survival 4 months; gynaecological: 25/140, 25 months; haematological: 22/140, < 50% died; urological: 21/140, 47 months; unknown primary: 12/140, 3 months; lung: 10/140, 17 months; breast: 3/140, 5 months; retroperitoneal: 2/140, 9 months; brain: 1/140, 4 months; adrenal: 1/140, 52 months). Binomial logistic regression was statistically significant (chi-squared goodness-of-fit test = 12.334; p = 0.03); but the presence of comorbidity was the only significant predictive factor of death (p = 0.03).

CONCLUSIONS

Patients with non-LGI cancers cannot be easily predicted and have a poor prognosis. Pathways to streamline investigations for LGI cancer should include computed tomography scans for patients at 'low risk' of LGI cancer to ensure that non-LGI cancers are diagnosed.

[Incidental and "leave me alone" findings in the GI tract-part 1 : Intestinal lumen and intestinal wall]

CLINICAL PROBLEM

Due to the widespread use of computed tomography (CT) and magnetic resonance imaging (MRI) asymptomatic incidental findings of the gastrointestinal tract (GI) are increasingly being recognized. Incidental findings are frequently not part of the primary inquiry from referring physicians but it is obligatory to make a diagnosis and to stipulate the need for further clarification.

RADIOLOGICAL STANDARD PROCEDURES

A multitude of incidental findings in the intestinal lumen, in the intestinal wall and in the adjacent mesenterium or subperitoneal space are shown in CT and MRI.

METHODOLOGICAL INNOVATIONS AND ASSESSMENT

The first part of the two-part overview addresses the intestinal incidental findings in the lumen, such as coproliths, invaginations, mucoceles and chronic dilatations. In the intestinal wall, thickenings of neoplastic and nonneoplastic origins are discussed. Many of the findings can be classified as benign and as "leave me alone lesions" do not necessitate any further clarification but in contrast others need a definitive clarification. The most important incidental findings in the GI tract are systematically classified, illustrated and evaluated with respect to the clinical relevance, depending on the localization (e.g. stomach, small and large intestines).

Computed Tomography Colonography (CTC): Is It Really the Non-Invasive Option We Think It Is? A Patient Experience Study

Aims: Computed tomography colonography (CTC) is seen as a more tolerable alternative to colonoscopy, but patients struggle with the steps required for optimal diagnostic imaging. This prospective study aims to understand the experience of patients undergoing CTC. Methods: A survey was completed by a convenience sample of patients before and after CTC over 7 months. The 13-item questionnaire covered pre-test information, overall and specific experience of the test. The responses were tabulated and analyzed using descriptive statistics. Qualitative free-text responses were coded for content and thematic analysis. Results: At a response rate of 51%, surveys were received from 41 patients. Overall, most patients (54%) found the investigation better than expected. However, 18% stated they were not informed of potential side effects. Side effects were experienced by 49% of patients, including diarrhea (34%) and abdominal pain (24%). About 59% experienced discomfort with gas insufflation, and 86% found turning during the investigation difficult. Conclusion: A significant proportion of patients undergoing CTC experience side effects and difficulties completing the investigation. Patient information is important to improve patient experience of CTC.

How to Read an Abdominal CT: Insights from the Visual and Cognitive Sciences Translated for Clinical Practice

When first learning abdominal CT studies, residents are often given little concrete, practical direction. There is, however, a large literature from the visual and cognitive sciences that can provide guidance towards search strategies that maximize efficiency and comprehensiveness. This literature has not penetrated radiology teaching to any great extent. In this article, we will examine the current pedagogy (and why that falls short), why untutored search fails, where misses occur in abdomen/pelvis CT, why these misses occur where they do, how expert radiologists search 3d image stacks, and how novices might expedite the acquisition of expertise.

Will a flexi-sig' do? A retrospective review of colonoscopies indicated by diverticulitis alone

BACKGROUND

The incidence of colonic diverticulitis is increasing. In Australia the majority of diverticulitis occurs in the left colon and patients typically undergo colonoscopy following an attack. At present debate exists regarding the utility of this costly procedure and a flexible sigmoidoscopy has been proposed as a cheaper, less invasive alternative. This paper seeks to examine whether significant pathology is being detected in the right and transverse colon to warrant colonoscopy, as opposed to a flexible sigmoidoscopy.

METHODS

A retrospective review of colonoscopies performed between August 2016 and August 2018, indicated by diverticulitis alone, performed in a single Australian metropolitan hospital.

RESULTS

189 patient colonoscopies were reviewed in combination with the pathology forms. Only 1 primary colonic malignancy was detected, found in the left colon. 110 traditional adenomas and 35 sessile serrated adenomas were detected. 41.8% of patients had a polyp detected with an average of 1.9 polyps per patient. 38.6% of polyps were resected from the left colon while 61.4% were removed from the right and transverse colon. In total 30 polyps > 10 mm or with high-risk histological features were resected, 18 (60%) from the left colon and 12 (40%) from the right and transverse. 20 patients (10.6%) met the criteria for high-risk adenomas and 50% of those had > 40% of their polyps in the right and transverse colon. There was no significant difference in age between patients with polyps and those without.

CONCLUSION

Despite over half the patients having no polyps and only one left sided malignancy. This study demonstrates that the right and transverse colon is responsible for over 50% of the polyps removed and similar proportion of the advanced polyps. Where endoscopic surveillance after acute colonic diverticulitis is performed, this study supports the use of colonoscopy and cautions against flexible sigmoidoscopy alone.

Prioritisation of lower gastrointestinal endoscopy during the COVID-19 pandemic: outcomes of a novel triage pathway

OBJECTIVE

The 2-week-wait (2ww) referral pathway is used in England to fast-track patients with suspected colorectal cancer (CRC). A two-stage triage pathway was used to prioritise lower gastrointestinal (LGI) endoscopy for suspected CRC during the COVID-19 pandemic.

METHOD

All patients referred for an LGI endoscopy via a 2ww referral pathway between March 2020 and July 2020 were assessed. The first stage triaged patients to high, standard or low risk of CRC based on symptoms and faecal immunochemical test (FIT), and offered CT scans to those at high risk. The second stage, endoscopy prioritisation (EP), incorporated the CT results, FIT and symptoms to triage into four groups, EP1-EP4; with EP1 being the most urgent and EP4 the least. The primary outcome measure was CRC detection.

RESULTS

514 patients were included. The risk of CRC was triaged as high in 190/514 patients (37%), standard in 274/514 patients (53%) and low in 50/514 (10%) patients. 422/514 patients (82%) underwent endoscopy with triage to EP1 in 52/422 (12%), EP2 in 105/422 (25%), EP3 in 210/422 (50%) and EP4 in 55/422 (13%). CRC was detected in 23 patients (5.4%). CRC was significantly more frequent in the EP1 group (23.1%, relative risk (RR)=16.2) and EP2 group (6.7%, RR=4.7) compared with EP3 group (1.4%). All CRC lesions were identified by CT imaging when performed prior to LGI endoscopy.

CONCLUSION

This triage pathway designated 83% of patients with CRC to either EP1 or EP2. During a period of limited endoscopy provision, this pathway effectively prioritises endoscopy for those at greatest risk of CRC.

Spectrum and Relevance of Incidental Bowel Findings on Computed Tomography

A wide spectrum of incidental bowel findings can be seen on CT, including but not limited to, pneumatosis intestinalis, diverticular disease, non-obstructive bowel dilatation, transient small bowel intussusception, and submucosal fat. Radiologists should be aware that such findings are almost always benign and of little clinical significance in the absence of associated symptoms. Conversely, vigilance must be maintained when evaluating the bowel, because malignant neoplasms occasionally come to clinical attention as incidental imaging findings. When suspicious incidental bowel wall thickening is detected, the radiologist can alert the clinical team to the finding prior to the patient becoming symptomatic, potentially leading to definitive management at an early, more curable stage.

Predictive value of initial imaging and staging with long-term outcomes in young adults diagnosed with colorectal cancer

PURPOSE

To evaluate how initial abdominopelvic CT findings and staging correlate with outcomes in a cohort of patients aged 18-40 years.

METHODS

We evaluated all young adult patients at a single tertiary center diagnosed with histopathologically confirmed CRC who also had CT of the abdomen and pelvis at the time of initial diagnosis. Demographics, symptoms, CT findings, staging, treatments, and outcomes at 1 year and 5 years were recorded.

RESULTS

Of 91 patients who met initial inclusion criteria, 81.8% had a mass present on CT, with an average size of 4.8 cm ± 2.9. A majority of patients were surgical stage III or IV (64.3%). Advanced AJCC stage was more common with rectal tumors and metastatic disease on initial CT (p < 0.0001). In a subgroup analysis, almost all patients initially staged 4A or higher had progression of disease. At the final follow-up visit, by RECIST 1.1 criteria, 58.8% had progressive disease, 35.3% complete response, and 3.9% stable disease. The overall 5-year survival rate in this subgroup was 40% with lower survival probability with increasing stage (p = 0.0001).

CONCLUSION

Most young adult patients presented with large tumors on imaging, increasing the likelihood of identification on CT. Tumors initially presenting in the rectum with enlarged lymph nodes and/or with distant metastases on CT were more often associated with advanced surgical stage and poorer prognosis. A majority of patients presented at an advanced stage, most commonly stage 4A, and had progression of disease at follow-up.

The Back Alleys and Dark Corners of Abdomen and Pelvis Computed Tomography: The Most Frequent Sites of Missed Findings in the Multiplanar Era

Objectives

Radiologists reading multiplanar abdominal/pelvic computed tomography (CT) are vulnerable to oversight of specific anatomic areas, leading to perceptual errors (misses). The aims of this study are to identify common sites of major perceptual error at our institution and then to put these in context with earlier studies to produce a comprehensive overview.

Material and Methods

We reviewed our quality assurance database over an 8-year period for cases of major perceptual error on CT examinations of the abdomen and pelvis. A major perceptual error was defined as a missed finding that had altered management in a way potentially detrimental to the patient. Record was made of patient age, gender, study indication, study priority (stat/routine), and use of IV and/or oral contrast. Anatomic locations were subdivided as lung bases, liver, pancreas, kidneys, spleen, mesentery, peritoneum, retroperitoneum, small bowel, colon, appendix, vasculature, body wall, and bones.

Results

A total of 216 missed findings were identified in 201 patients. The most common indication for the study was cancer follow-up (71%) followed by infection (11%) and abdominal pain (6%). The most common anatomic regions of error were the liver (15%), peritoneum (10%), body wall (9%), retroperitoneum (8%), and mesentery (6%). Data from other studies were reorganized into congruent categories for comparison.

Conclusion

This study demonstrates that the most common sites of significant missed findings on multiplanar abdominal/pelvic CT included the mesentery, peritoneum, body wall, bowel, vasculature, and the liver in the arterial phase. Data from other similar studies were reorganized into congruent categories to provide a comprehensive overview.

Computed tomography diagnosed first time diverticulitis and colorectal cancer

BACKGROUND

Computed tomography (CT) with intravenous contrast is the gold standard for diagnosing diverticulitis. Published results concerning follow-up colonoscopy after an episode of acute diverticulitis to rule out cancer are conflicting. This study aimed to evaluate the risk of underlying colonic malignancy in patients diagnosed with a first time diverticulitis with a state of the art CT investigation with intravenous contrast.

METHODS

Retrospective analysis of all patients with a first episode of diverticulitis diagnosed with CT at Danderyds Hospital, Stockholm, between January 1, 2015, and November 16, 2016. Data on modified Hinchey classification, age, sex, laboratory parameters, body mass index, and colonoscopy findings were recorded.

RESULTS

The study identified 518 patients with a CT-verified first time diverticulitis. Four hundred twenty-six (82%) of the 518 patients underwent follow-up colonoscopy and constitute our study cohort. CT showed that 402 patients had uncomplicated diverticulitis (modified Hinchey Ia), and 24 patients had complicated diverticulitis (modified Hinchey ≥Ib). Colonoscopy showed cancers in 2 (0.5%) of the 426 patients initially diagnosed as acute diverticulitis. In addition, 13 (3%) patients had advanced adenomas, and 121 (28%) patients had benign adenomas upon follow-up colonoscopy. Patients with CT-verified complicated diverticulitis (modified Hinchey ≥Ib) had a significantly higher risk for colon cancer compared with patients with an uncomplicated first time diverticulitis.

CONCLUSION

Our study supports routine follow-up colonoscopy after a first episode of CT-diagnosed complicated diverticulitis. In contrast, we do not find an increased risk for neoplasia in patients with uncomplicated diverticulitis.

Colon capsule endoscopy: an innovative method for detecting colorectal pathology during the COVID-19 pandemic?

AIM

The coronavirus pandemic has led to significant challenges for healthcare delivery across the globe. Non-emergency endoscopic activity in the UK has been postponed, raising concerns of increased delays in the diagnosis of colorectal cancer and a surge in demand once services resume. Measures to mitigate this risk must be considered.

METHOD

This paper reviews various investigative modalities for colorectal disease which could be deployed during cessation of colonoscopy services. We focus on colon capsule endoscopy (CCE) due to its relevance during the COVID-19 pandemic and its ability to triage patients effectively to further endoscopic investigations.

RESULTS

CT of the abdomen and pelvis has been suggested as a triage tool while access to colonoscopy is limited. However, CT may lead to the spread of COVID-19 as patients attend the hospital, and it exposes them to the risks of radiation. Faecal immunochemistry tests have been demonstrated as a good predictor of colonic pathology and could be safely used to risk stratify patients when prioritizing colonoscopy. CCE is a safe and innovative technology for investigating the colon. Procedures can be carried out in the community and can be conducted safely during the coronavirus pandemic. It has been shown to be an accurate detector of colonic neoplasia and can reduce demand for colonoscopy.

CONCLUSION

As colonoscopy services resume, they will probably experience high demand leading to further delays for patients. CCE could be used to reduce the number of patients requiring colonoscopy and triage those requiring further endoscopic investigations appropriately.

Endometriosis Mimicking a Cecum Mass with Complete Bowel Obstruction: An Infrequent Cause of Acute Abdomen

Endometriosis is a common entity among fertile women which unfortunately manifests through variable symptomatology. Intestinal involvement in endometriosis is quite common and can simulate several diseases such as Crohn's disease, appendicitis, tubo-ovarian abscess, or malignant tumors. Intestinal obstruction due to endometriosis is rare, and preoperative diagnosis is difficult because the signs and symptoms are nonspecific and can be easily confused. In the case of patients without a history of endometriosis, diagnosis is further complicated. We present a case of a 41-year-old female patient. She presented to the emergency room with complete bowel obstruction and a mass in the cecum. Surgery was decided, and the patient underwent full recovery. Endometriosis was the final diagnosis for the observed condition.

Villous Gastrointestinal Tumors: Multimodality Imaging with Histopathologic Correlation

Villous lesions are advanced adenomas that manifest most commonly in the colon; however, they can develop throughout the gastrointestinal tract. The duodenum is the most common small-bowel site of these lesions. Although in most cases these are isolated lesions that occur sporadically, patients with certain specific colorectal cancer syndromes, including familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, may develop multiple advanced adenomas. Villous lesions are important because although they are histologically benign, they may harbor dysplasia and have potential for malignancy. These characteristics make them a primary target for colorectal cancer screening with optical and virtual colonoscopy. However, these lesions can also be symptomatic and detected at diagnostic imaging when patients present for examination. They have characteristic features at a variety of imaging examinations, including barium fluoroscopy, CT, MRI, and endoscopic US. It is important for radiologists to be aware of these lesions, their potential morphologies, and their typical appearances at multimodality imaging. Although villous tumors can be detected at imaging and confirmed with biopsy, owing to limitations in identifying dysplasia and foci of malignancy with the above modalities alone and the potential for malignancy, referral for surgical resection of these lesions ultimately is required. ^©RSNA, 2018.

Imaging of colorectal cancer - the clue to individualized treatment

Colorectal cancer (CRC) is the most common gastrointestinal neoplasm and the second most common cause for cancer-related death in Europe. Imaging plays an important role both in the primary diagnosis, treatment evaluation, follow-up, and, to some extent, also in prevention. Like in the clinical setting, colon and rectal cancer have to be distinguished as two quite separate entities with different goals of imaging and, consequently, also different technical requirements. Over the past decade, there have been improvements in both more robust imaging techniques and new data and guidelines that help to use the optimal imaging modality for each scenario. For colon cancer, the continued research on computed tomography (CT) colonography (CTC) has led to high-level evidence that puts this technique on eye height to optical colonoscopy in terms of detection of cancer and polyps ≥10 mm. However, also for smaller polyps and thus for screening purposes, CTC seems to be an optimal tool. In rectal cancer, the technical requirements to perform state-of-the art imaging have recently been defined. Evaluation of T-stage, mesorectal fascia infiltration and extramural vascular invasion are the most important prognostic factors that can be identified on MRI. With this information, risk stratification both for local and distal failure is possible, enabling the clinician to tailor the optimal therapeutic approach in non-metastatic rectal cancer. Imaging of metastatic CRC is also covered, although the complex ramifications of treatment options in the metastatic setting are beyond the scope of this article. In this review, the most important recent developments in the imaging of colon and rectal cancer will be highlighted. If used in an interdisciplinary setting, this can lead to an individualized treatment concept for each patient.

The Accuracy of Colorectal Cancer Detection by Computed Tomography in the Unprepared Large Bowel in a Community-Based Hospital

PURPOSE

This retrospective study examined the performance of general radiologists in a community-based hospital in detecting colorectal cancer (CRC) with computed tomography (CT) in the unprepared large bowel.

METHODS

The pathology database at a community hospital over the past 7 years (2009-2015) was retrospectively analysed for pathologically proven CRC (924 cases). The provincial hospital information profile for these patients was reviewed to determine if they had an abdominal CT for any reason in the year prior to biopsy. Metrics such as age, sex, time between the CT and biopsy or surgery, whether CRC was initially detected by the radiologist, and if this was an emergency presentation was evaluated. In the cases where CRC was not identified, the CT scans were reanalysed to determine if the CRC was identifiable in retrospect. The sensitivity of detecting CRC by CT scan in the unprepared large bowel was calculated.

RESULTS

Of the 924 biopsy proven CRC cases, 22% (207 of 924) of the patients had a CT prior to biopsy. Of these cases, 47% (97 of 207) presented on an emergency basis. Of the cases with imaging in the year prior, about 60% (125 of 207) had cancer prospectively detected by the radiologist. Upon re-examination of the cases in which CRC was not initially detected, 59% were visualized in retrospect.

CONCLUSIONS

Community general radiologists can successfully detect CRC with a high degree of accuracy. Reformatted images, bowel wall thickening when regional nodes are prominent, and minimizing oral contrast were helpful in improving detection.

CT Image-based Decision Support System for Categorization of Liver Metastases Into Primary Cancer Sites: Initial Results

RATIONALE AND OBJECTIVES

This study aimed to provide decision support for the human expert, to categorize liver metastases into their primary cancer sites. Currently, once a liver metastasis is detected, the process of finding the primary site is challenging, time-consuming, and requires multiple examinations. The proposed system can support the human expert in localizing the search for the cancer source by prioritizing the examinations to probable cancer sites.

MATERIALS AND METHODS

The suggested method is a learning-based approach, using computed tomography (CT) data as the input source. Each metastasis is circumscribed by a radiologist in portal phase and in non-contrast CT images. Visual features are computed from these images, combined into feature vectors, and classified using support vector machine classification. A variety of different features were explored and tested. A leave-one-out cross-validation technique was conducted for classification evaluation. The methods were developed on a set of 50 lesion cases taken from 29 patients.

RESULTS

Experiments were conducted on a separate set of 142 lesion cases taken from 71 patients with four different primary sites. Multiclass categorization results (four classes) achieved low accuracy results. However, the proposed system was found to provide promising results of 83% and 99% for top-2 and top-3 classification tasks, respectively. Moreover, when compared to the experts' ability to distinguish the different metastases, the system shows improved results.

CONCLUSIONS

Automated systems, such as the one proposed, show promising new results and demonstrate new capabilities that, in the future, will be able to provide decision and treatment support for radiologists and oncologists, toward more efficient detection and treatment of cancer.

Pitfalls in diagnosing colon cancer on abdominal CT

AIM

To assess the frequency of undetected colon cancer on conventional abdominal CT and to evaluate the imaging features that are characteristic of those cancers.

MATERIALS AND METHODS

The present study included consecutive patients diagnosed with colorectal cancer at colonoscopy (2006-2015) who also underwent abdominal computed tomography (CT) performed for various reasons within a year prior to the colonoscopy. The frequency of undetected lesions was evaluated for the original CT interpretations ("original readers"). Two radiologists ("study readers"), blinded to the tumour location, independently performed interpretations oriented for colon cancer detection. The study readers analysed the imaging features of detected tumours (tumour shape, length, maximal wall thickness, free fluid, fat stranding, vascular engorgement, stenosis, and lymphadenopathy). Imaging features of the cancers undetected by the original readers were evaluated.

RESULTS

The study included 127 patients. The original readers' frequency of undetected cancer was 25/127 (19.7%). Each study reader could not identify the cancer in 8/127 (6.3%) patients. Imaging features associated with undetected cancers by the original readers included the absence of fat stranding (p=0.007, p=0.003), absence of vascular engorgement (p<0.0001, p<0.0001) and absence of lymphadenopathy (p=0.005, p=0.004). Undetected tumours were shorter than those detected (original reader: 33.2±11.9 versus 51.4±18.2 mm; study reader: 32.5±9.6 versus 61.3±23.4 mm; p<0.001).

CONCLUSION

Colon cancer is undetected in 20% of abdominal CT examinations in patients subsequently proven to have colon cancer at colonoscopy. The absence of fat stranding, vascular engorgement, or lymphadenopathy, and an average tumour length of 3.3 cm are contributing factors for failure of detection. Radiologists' training should emphasis these findings as it may improve cancer detection, and clinicians should be aware of the limitations of abdominal CT.

Prediction of synchronous colorectal cancers by computed tomography in subjects receiving an incomplete colonoscopy: A single-center study

AIM: To assess the value of computed tomography (CT) for diagnosis of synchronous colorectal cancers (SCRCs) involving incomplete colonoscopy.

METHODS: A total of 2123 cases of colorectal cancer (CRC) were reviewed and divided into two groups according to whether a complete or incomplete colonoscopy was performed. CT results and final histological findings were compared to calculate the sensitivity and specificity associated with CT for detection of SCRCs following complete vs incomplete colonoscopy. Factors affecting the CT detection were also analyzed.

RESULTS: Three hundred and seventy-four CRC patients underwent incomplete colonoscopy and 1749 received complete colonoscopy. Fifty-six cases of SCRCs were identified by CT, and 36 were missed. In the incomplete colonoscopy group, the sensitivity and specificity of CT were 44.8% and 93.6%, respectively. The positive and negative predictive values were 23.6% and 95.0%, respectively. In contrast, the sensitivity and specificity of CT for the complete colonoscopy group were 68.3% and 97.0%, while the positive and negative predictive values were 22.2% and 98.7%, respectively. In both groups, the mean maximum dimension of the concurrent cancers identified in the CT-negative cases was shorter than in the CT-positive cases (incomplete group: P = 0.02; complete group: P < 0.01) Topographical proximity to synchronous cancers was identified as a risk factor for missed diagnosis (P = 0.03).

CONCLUSION: CT has limited sensitivity in detecting SCRCs in patients receiving incomplete colonoscopy. Patients with risk factors and negative CT results should be closely examined and monitored.

Diagnostic impact of routine colonoscopy following acute diverticulitis: A multicenter study in 808 patients and controls

BACKGROUND

The diagnosis of acute diverticulitis is mainly based on clinical, biological and computed tomography (CT)-scan findings. Elective colonoscopy is recommended after medical treatment, to rule out another diagnosis and to detect associated conditions; however, the relevance of this recommendation has been questioned.

PATIENTS AND METHODS

Between January 2005 and December 2011, we retrospectively identified in three referral centers the consecutive patients whom underwent a colonoscopy after the medical treatment of a CT scan-proven acute diverticulitis episode. We excluded from the analysis patients with haematochezia or recent change in bowel habits. Sex and age-matched asymptomatic patients undergoing a screening colonoscopy were chosen as a control group. We collected and compared the results of colonoscopy and histological findings in both groups.

RESULTS

We matched 404 patients whom underwent a colonoscopy after an episode of acute diverticulitis with 404 control patients. Their mean age was 60.9 years, with 59% being women. Colorectal adenoma, advanced adenoma and cancer detection rates in acute diverticulitis patients were 12.1%, 2.7% and 0.25%, respectively; versus 14.6% (p = 0.35), 6.7% (p = 0.01) and 0.25% respectively, in control patients.

CONCLUSIONS

Diagnosis rates for adenomas and for colorectal cancer during a colonoscopy scheduled after acute diverticulitis were similar than those of control patients undergoing a screening colonoscopy, while the detection rate of advanced adenomas was lower. We suggest that colonoscopy should be indicated only in selected patients, i.e. those presenting with reasonable doubt on initial CT-scan, those with alarm symptoms, and those with identified risk factors for colorectal cancer.

Systematic review and meta-analysis of the role of routine colonic evaluation after radiologically confirmed acute diverticulitis

OBJECTIVE

To determine the yield of colorectal cancer at routine colonic evaluation after radiologically proven acute diverticulitis.

BACKGROUND

Acute diverticulitis accounts for 152,000 hospitalizations in the United States alone. Current guidelines recommend routine colonic evaluation after acute diverticulitis to confirm the diagnosis and exclude malignancy. However, research suggests that the yield of colorectal cancer after computed tomography-proven uncomplicated diverticulitis may be low. In the era of widespread computed tomographic scanning for diverticulitis, routine colonic evaluation after diverticulitis may represent a nonessential burden on health care resources.

METHODS

The PubMed (MEDLINE), EMBASE, BIREME, CINAHL, and the Cochrane Library databases were searched. Original studies of colonic evaluation after proven acute diverticulitis were included. Meta-analysis of data from included studies was performed using a DerSimonian Laird random effect proportion analysis.

RESULTS

Eleven studies from 7 countries were included in the analysis. Out of a pooled population of 1970 patients, cancer was found in 22. The pooled proportional estimate of malignancy was 1.6% (95% confidence interval [CI], 0.9%-2.8%). Of the 1497 patients with uncomplicated diverticulitis, cancer was found in 5 (proportional estimate of risk 0.7%; CI, 0.3%-1.4%). Of the 79 patients with complicated disease, cancer was found in 6 (proportion estimate of risk 10.8%; CI, 5.2%-21.0%).

CONCLUSIONS

The risk of malignancy after a radiologically proven episode of acute uncomplicated diverticulitis is low. In the absence of other indications, routine colonoscopy may not be necessary. Patients with complicated diverticulitis still have a significant risk of colorectal cancer at subsequent colonic evaluation.

The performance of routine computed tomography for the detection of colorectal cancer

INTRODUCTION

Although colonoscopy and computed tomography (CT) colonography in expert hands are the most sensitive investigations for colorectal cancer, some patients may not tolerate the necessary bowel preparation and insufflation of gas into the colon. We assessed the performance of unprepared contrast CT for the detection of colorectal cancer.

METHODS

A retrospective review was undertaken of all patients who had contrast CT of the abdomen and pelvis and then went on to have colonoscopy at our institutions between 2007 and 2010.

RESULTS

Overall, 96 patients were identified as having had CT prior to colonoscopy. The sensitivity of CT in detecting colorectal cancer was 100% (95% confidence interval [CI]: 19.8-100%) and the specificity was 95.7% (95% CI: 88.8-98.6%). The positive predictive value was 33.3% (95% CI: 6.0-75.9%) and the negative predictive value was 100% (95% CI: 94.8-100%).

CONCLUSIONS

Non-targeted CT that is negative for colorectal malignancy is usually reassuring but the decision for further investigations should be made on a case-by-case basis, taking into account of the likelihood of underlying colorectal malignancy and the underlying co-morbidities of the patient. However, video colonoscopy is usually necessary to assess positive CT findings.

Colorectal cancer is reliably excluded in the frail and elderly population by minimal preparation CT

BACKGROUND

This study aimed to retrospectively assess the accuracy of minimal preparation computed tomography (MPCT) in the detection of colorectal cancer (CRC) within the frail and elderly population and to evaluate the relevance of extra-colonic findings (ECF).

METHODS

Radiology reports, clinical notes and follow-up reports from 207 patients who underwent MPCT to investigate for CRC between 2005 and 2009 were analysed. Patients were scanned following the administration of oral contrast for 48 h, without bowel preparation or colonic insufflation. MPCT results were measured against patient outcomes, with a minimum of 2 years of follow-up.

RESULTS

Twelve cases of clinically relevant CRC were confirmed (5.8 %). MPCT correctly identified 11 of these lesions (sensitivity 91.6 %). Thirty-one patients had a possible CRC identified by MPCT, which was not confirmed by further examination (specificity 84.1 %). This results in a positive predictive value of 26.2 % and a negative predictive value of 99.4 %. Five of the patients with colon cancer underwent curative surgery. Sixty-eight clinically relevant ECF were confirmed, including 14 previously undiagnosed extra-colonic malignancies. ECF were considered to account for the presenting complaint in 15.0 % (31/207) of all patients.

CONCLUSIONS

Minimal preparation computed tomography is an effective and reliable investigation for the exclusion of clinically relevant CRC in this population. It provides clinicians with a valuable and pragmatic alternative to colonoscopy and CT colonography when invasive examination or cathartic bowel preparation will be poorly tolerated and small polyps are of limited significance. MPCT has an advantage over purely luminal imaging in the detection of extra-colonic pathology and appears to have an equally important role in the detection of CRC.

The feasibility of colorectal cancer detection using dual-energy computed tomography with iodine mapping

AIM

To assess the feasibility of colorectal cancer detection using dual-energy computed tomography with iodine mapping and without bowel preparation or bowel distension.

MATERIALS AND METHODS

Consecutive patients scheduled for preoperative staging computed tomography (CT) because of diagnosed or high suspicion for colorectal cancer were prospectively included in the study. A single contrast-enhanced abdominal CT acquisition using dual-source mode (100 kV/140 kV) was performed without bowel preparation. Weighted average 120 kV images and iodine maps were created with post-processing. Two observers performed a blinded read for colorectal lesions after being trained on three colorectal cancer patients. One observer performed an unblinded read for lesion detectability and placed a region of interest (ROI) within each lesion.

RESULTS

In total 21 patients were included and 18 had a colorectal cancer at the time of the CT acquisition. Median cancer size was 43 mm [interquartile range (IQR) 27-60 mm] and all 18 colorectal cancers were visible on the 120 kV images and iodine map during the unblinded read. During the blinded read, observers found 90% (27/30) of the cancers with 120 kV images only and 96.7% (29/30) after viewing the iodine map in addition (p = 0.5). Median enhancement of colorectal cancers was 29.9 HU (IQR 23.1-34.6). The largest benign lesions (70 and 25 mm) were visible on the 120 kV images and iodine map, whereas four smaller benign lesions (7-15 mm) were not.

CONCLUSION

Colorectal cancers are visible on the contrast-enhanced dual-energy CT without bowel preparation or insufflation. Because of the patient-friendly nature of this approach, further studies should explore its use for colorectal cancer detection in frail and elderly patients.

Computed tomography colonography: emerging evidence to further support clinical effectiveness

PURPOSE OF REVIEW

Computed tomography colonography (CTC) continues to mature and evolve as a noninvasive imaging test of the large intestine. The aim of this review is to provide an update on the recent and emerging data that further supports the clinical effectiveness of CTC.

RECENT FINDINGS

The diagnostic performance of CTC for detecting colorectal polyps and masses is well established, but its precise clinical role is yet to be determined. Recent data on test performance, patient acceptance, and study technique may help to clarify the role of CTC and accelerate its clinical implementation.

SUMMARY

Recent advances and refinements in CTC should help to clarify and expand its clinical role, both as a screening and diagnostic test. High patient acceptance for CTC could lead to increased adherence rates. Ultimately, the complementary nature of CTC and optical colonoscopy should result in improved patient care.

Role of CT colonography in symptomatic assessment, surveillance and screening

INTRODUCTION

When 'whole colonic imaging' is indicated, clinicians must decide between optical colonoscopy, barium enema and CT colonography (CTC). CTC is a relatively new technique which has become increasingly accessible in the UK over the past 5 years. As radiologists have gained experience and scanning parameters have standardised, there have been substantial improvements in both the accuracy and safety of CTC.

METHODS

We review evidence from observational studies and randomised trials, and draw on expert opinion, to provide a comprehensive discussion of the current role of CTC in both symptomatic and asymptomatic individuals.

CONCLUSIONS

The emergence of CTC could soon entirely obviate the need for barium enema. CTC now has a complementary role alongside colonoscopy in symptomatic patients and a possible future role in colorectal cancer screening in the UK.

Routine colonoscopy following acute uncomplicated diverticulitis

BACKGROUND

The evidence supporting current recommendations that the colon should be evaluated following an initial episode of acute diverticulitis is poor. The aim of this study was to clarify whether acute uncomplicated diverticulitis is a valid indication for subsequent colonoscopy/computed tomography (CT) colonography.

METHODS

This was a retrospective longitudinal study of patients with an initial presentation of acute uncomplicated diverticulitis on the basis of CT criteria, at a single institution between January 2004 and December 2008.

RESULTS

A radiological diagnosis of acute uncomplicated diverticulitis was made in 292 patients. Some 205 patients underwent subsequent colonic evaluation or had undergone colonoscopy/CT colonography within the preceding 2 years. Colorectal polyps were present in 50 patients (24·4 per cent). Twenty patients (9·8 per cent) had hyperplastic polyps and 19 (9·3 per cent) had adenomas. Eleven patients (5·4 per cent) had advanced colonic neoplasia, including one (0·5 per cent) with a colorectal cancer. One patient had inflammatory bowel disease (IBD). The patients with colorectal cancer and IBD had clinical indicators that independently warranted colonoscopy. None of the 87 patients who did not undergo colonic evaluation had a diagnosis of colorectal cancer registered with the New Zealand Cancer Registry.

CONCLUSION

The yield of advanced colonic neoplasia in this cohort was equivalent to, or less than that detected on screening asymptomatic average-risk individuals. In the absence of other indications, subsequent evaluation of the colon may not be required to confirm the diagnosis of diverticulitis.