Growth rates and histopathological outcomes of small (6-9 mm) colorectal polyps based on CT colonography surveillance and endoscopic removal.

BACKGROUND AND AIMS: The natural history of small polyps is not well established and rests on limited evidence from barium enema studies decades ago. Patients with one or two small polyps (6-9 mm) at screening CT colonography (CTC) are offered CTC surveillance at 3 years but may elect immediate colonoscopy. This practice allows direct observation of the growth of subcentimetre polyps, with histopathological correlation in patients undergoing subsequent polypectomy. DESIGN: Of 11 165 asymptomatic patients screened by CTC over a period of 16.4 years, 1067 had one or two 6-9 mm polyps detected (with no polyps ≥10 mm). Of these, 314 (mean age, 57.4 years; M:F, 141:173; 375 total polyps) elected immediate colonoscopic polypectomy, and 382 (mean age 57.0 years; M:F, 217:165; 481 total polyps) elected CTC surveillance over a mean of 4.7 years. Volumetric polyp growth was analysed, with histopathological correlation for resected polyps. Polyp growth and regression were defined as volume change of ±20% per year, with rapid growth defined as +100% per year (annual volume doubling). Regression analysis was performed to evaluate predictors of advanced histology, defined as the presence of cancer, high-grade dysplasia (HGD) or villous components. RESULTS: Of the 314 patients who underwent immediate polypectomy, 67.8% (213/314) harboured adenomas, 2.2% (7/314) with advanced histology; no polyps contained cancer or HGD. Of 382 patients who underwent CTC surveillance, 24.9% (95/382) had polyps that grew, while 62.0% (237/382) remained stable and 13.1% (50/382) regressed in size. Of the 58.6% (224/382) CTC surveillance patients who ultimately underwent colonoscopic resection, 87.1% (195/224) harboured adenomas, 12.9% (29/224) with advanced histology. Of CTC surveillance patients with growing polyps who underwent resection, 23.2% (19/82) harboured advanced histology vs 7.0% (10/142) with stable or regressing polyps (OR: 4.0; p<0.001), with even greater risk of advanced histology in those with rapid growth (63.6%, 14/22, OR: 25.4; p<0.001). Polyp growth, but not patient age/sex or polyp morphology/location were significant predictors of advanced histology. CONCLUSION: Small 6-9 mm polyps present overall low risk to patients, with polyp growth strongly associated with higher risk lesions. Most patients (75%) with small 6-9 mm polyps will see polyp stability or regression, with advanced histology seen in only 7%. The minority of patients (25%) with small polyps that do grow have a 3-fold increased risk of advanced histology.

Abdominal CT Body Composition Thresholds Using Automated AI Tools for Predicting 10-year Adverse Outcomes.

Background CT-based body composition measures derived from fully automated artificial intelligence tools are promising for opportunistic screening. However, body composition thresholds associated with adverse clinical outcomes are lacking. Purpose To determine population and sex-specific thresholds for muscle, abdominal fat, and abdominal aortic calcium measures at abdominal CT for predicting risk of death, adverse cardiovascular events, and fragility fractures. Materials and Methods In this retrospective single-center study, fully automated algorithms for quantifying skeletal muscle (L3 level), abdominal fat (L3 level), and abdominal aortic calcium were applied to noncontrast abdominal CT scans from asymptomatic adults screened from 2004 to 2016. Longitudinal follow-up documented subsequent death, adverse cardiovascular events (myocardial infarction, cerebrovascular event, and heart failure), and fragility fractures. Receiver operating characteristic (ROC) curve analysis was performed to derive thresholds for body composition measures to achieve optimal ROC curve performance and high specificity (90%) for 10-year risks. Results A total of 9223 asymptomatic adults (mean age, 57 years ± 7 [SD]; 5152 women and 4071 men) were evaluated (median follow-up, 9 years). Muscle attenuation and aortic calcium had the highest diagnostic performance for predicting death, with areas under the ROC curve of 0.76 for men (95% CI: 0.72, 0.79) and 0.72 for women (95% CI: 0.69, 0.76) for muscle attenuation. Sex-specific thresholds were higher in men than women (P < .001 for muscle attenuation for all outcomes). The highest-performing markers for risk of death were muscle attenuation in men (31 HU; 71% sensitivity [164 of 232 patients]; 72% specificity [1114 of 1543 patients]) and aortic calcium in women (Agatston score, 167; 70% sensitivity [152 of 218 patients]; 70% specificity [1427 of 2034 patients]). Ninety-percent specificity thresholds for muscle attenuation for both risk of death and fragility fractures were 23 HU (men) and 13 HU (women). For aortic calcium and risk of death and adverse cardiovascular events, 90% specificity Agatston score thresholds were 1475 (men) and 735 (women). Conclusion Sex-specific thresholds for automated abdominal CT-based body composition measures can be used to predict risk of death, adverse cardiovascular events, and fragility fractures. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Ohliger in this issue.

Improved CT-based Osteoporosis Assessment with a Fully Automated Deep Learning Tool.

Purpose: To develop, test, and validate a deep learning (DL) tool that improves upon a previous feature-based CT image processing bone mineral density (BMD) algorithm and compare it against the manual reference standard. Materials and Methods: This single-center, retrospective, Health Insurance Portability and Accountability Act-compliant study included manual L1 trabecular Hounsfield unit measurements from abdominal CT scans in 11 035 patients (mean age, 58 years ± 12 [SD]; 6311 women) as the reference standard. Automated level selection and L1 trabecular region of interest (ROI) placement were then performed in this CT cohort with both a previously validated feature-based image processing tool and a new DL tool. Overall technical success rates and agreement with the manual reference standard were assessed. Results: The overall success rate of the DL tool in this heterogeneous patient cohort was significantly higher than that of the older image processing BMD algorithm (99.3% vs 89.4%, P < .001). Using this DL tool, the closest median Hounsfield unit values for single-, three-, and seven-slice vertebral ROIs were within 5% of the manual reference standard Hounsfield unit values in 35.1%, 56.9%, and 85.8% of scans; within 10% in 56.6%, 75.6%, and 92.9% of scans; and within 25% in 76.5%, 89.3%, and 97.1% of scans, respectively. Trade-offs in sensitivity and specificity for osteoporosis assessment were observed from the single-slice approach (sensitivity, 39.4%; specificity, 98.3%) to the minimum value of the multislice approach (for seven contiguous slices; sensitivity, 71.3% and specificity, 94.6%). Conclusion: The new DL BMD tool demonstrated a higher success rate than the older feature-based image processing tool, and its outputs can be targeted for higher specificity or sensitivity for osteoporosis assessment.Keywords: CT, CT-Quantitative, Abdomen/GI, Skeletal-Axial, Spine, Deep Learning, Machine Learning Supplemental material is available for this article. © RSNA, 2022.

Hepatic hemangioendothelioma: CT, MR, and FDG-PET-CT in 67 patients-a bi-institutional comprehensive cancer center review.

OBJECTIVE: To evaluate the imaging features of hepatic epithelioid hemangioendothelioma (HEH) on multiphasic CT, MR, and FDG-PET-CT. METHODS: Bi-institutional review identified 67 adults (mean age, 47 years; 23 M/44 F) with pathologically proven HEH and pretreatment multiphasic CT (n = 67) and/or MR (n = 30) and/or FDG-PET-CT (n = 13). RESULTS: HEHs were multifocal in 88% (59/67). Mean size of the dominant mass was 4.1 cm (range, 1.4-19 cm). The tumors were located in the peripheral, subcapsular regions of the liver in 96% (64/67). Capsular retraction was present in 81% (54/67 cases) and tumors were coalescent in 61% (41/67). HEH demonstrated peripheral ring enhancement on arterial phase imaging in 33% (21/64) and target appearance on the portal venous phase in 69% (46/67). Persistent peripheral enhancement on the delayed phase was seen in 49% (31/63). On MR, multilayered target appearance was seen on the T2-weighted sequences in 67% (20/30) and on the diffusion-weighted sequences in 61% (11/18). Target appearance on hepatobiliary phase of MRI was seen in 57% (4/7). On pre-therapy FDG-PET-CT, increased FDG uptake above the background liver parenchyma was seen in 62% (8/13). CONCLUSION: HEHs typically manifest as multifocal, coalescent hepatic nodules in peripheral subcapsular location, with associated capsular retraction. Peripheral arterial ring enhancement and target appearance on portal venous phase are commonly seen on CT. Similarly, multilayered target appearance correlating with its histopathological composition is typically seen on multiple sequences of MR including T2-weighted, diffusion-weighted, and dynamic contrast-enhanced multiphasic MR. KEY POINTS: • Hepatic epithelioid hemangioendotheliomas manifest on CT and MR as multifocal, coalescent hepatic nodules in peripheral subcapsular location, with associated capsular retraction. • Enhancement pattern on contrast-enhanced CT and MR can vary but peripheral ring enhancement on arterial phase and target appearance on portal venous phase are commonly seen. • Retrospective two-center study showed that cross-sectional imaging may help in the diagnosis.

Opportunistic Osteoporosis Screening at Routine Abdominal and Thoracic CT: Normative L1 Trabecular Attenuation Values in More than 20 000 Adults.

Background Abdominal and thoracic CT provide a valuable opportunity for osteoporosis screening regardless of the clinical indication for imaging. Purpose To establish reference normative ranges for first lumbar vertebra (L1) trabecular attenuation values across all adult ages to measure bone mineral density (BMD) at routine CT. Materials and Methods Reference data were constructed from 20 374 abdominal and/or thoracic CT examinations performed at 120 kV. Data were derived from adults (mean age, 60 years ± 12 [standard deviation]; 56.1% [11 428 of 20 374] women). CT examinations were performed with (n = 4263) or without (n = 16 111) intravenous contrast agent administration for a variety of unrelated clinical indications between 2000 and 2018. L1 Hounsfield unit measurement was obtained either with a customized automated tool (n = 11 270) or manually by individual readers (n = 9104). The effects of patient age, sex, contrast agent, and manual region-of-interest versus fully automated L1 Hounsfield unit measurement were assessed using multivariable logistic regression analysis. Results Mean L1 attenuation decreased linearly with age at a rate of 2.5 HU per year, averaging 226 HU ± 44 for patients younger than 30 years and 89 HU ± 38 for patients 90 years or older. Women had a higher mean L1 attenuation compared with men (P < .008) until menopause, after which both groups had similar values. Administration of intravenous contrast agent resulted in negligible differences in mean L1 attenuation values except in patients younger than 40 years. The fully automated method resulted in measurements that were average 21 HU higher compared with manual measurement (P < .004); at intrapatient subanalysis, this difference was related to the level of transverse measurement used (midvertebra vs off-midline level). Conclusion Normative ranges of L1 vertebra trabecular attenuation were established across all adult ages, and these can serve as a quick reference at routine CT to identify adults with low bone mineral density who are at risk for osteoporosis. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Smith in this issue.

Adherence to postresection colorectal cancer surveillance at National Cancer Institute-designated Comprehensive Cancer Centers.

Guidelines recommend surveillance after resection of colorectal cancer (CRC), but rates of adherence to surveillance are variable and have not been studied at National Cancer Institute (NCI)-designated Comprehensive Cancer Centers. The aim of this study was to determine rates of adherence to standard postresection CRC surveillance recommendations including physician visits, carcinoembryonic antigen (CEA), computed tomography (CT), and colonoscopy after CRC resection at three NCI-designated centers. Data on patients with resected CRC from 2010 to 2017 were reviewed. Adherence to physician visits was defined as having at least two visits within 14 months after surgical resection. CEA adherence was defined as having at least four CEA levels drawn within 14 months. CT and colonoscopy adherence were defined as completing each between 10 and 14 months from surgical resection. Chi-square test and logistic regression analyses were performed for overall adherence and adherence to individual components. A total of 241 CRC patients were included. Overall adherence was 23%. While adherence to physician visits was over 98%, adherence to CEA levels, CT, and colonoscopy were each less than 50%. Center was an independent predictor of adherence to CEA, CT, and/or colonoscopy. Stage III disease predicted CT adherence, while distance traveled of 40 miles or less predicted colonoscopy adherence. Overall adherence to postresection CRC guideline-recommended care is low at NCI-designated centers. Adherence rates to surveillance vary by center, stage, and distance traveled for care. Understanding factors associated with adherence is critical to ensure CRC patients benefit from postresection surveillance.

Pulmonary Intraparenchymal Blood Patching Decreases the Rate of Pneumothorax-Related Complications following Percutaneous CT-Guided Needle Biopsy.

PURPOSE: To investigate whether an autologous intraparenchymal blood patch (IPB) reduces the rate of pneumothorax-related complications associated with computed tomography (CT)-guided lung biopsies. MATERIALS AND METHODS: This study included 834 patients: 482 who received an IPB and 352 who did not. Retrospective review was performed of all CT-guided lung biopsies performed at a single institution between August 2006 and September 2013. Patients were excluded if no aerated lung was crossed. The rate of pneumothorax, any associated intervention (eg, catheter placement, aspiration), chest tube placement, and chest tube replacement requiring hospital admission were compared by linear and multiple regression analysis. RESULTS: Patients who received an IPB had a significantly lower rate of pneumothorax (145 of 482 [30%] vs 154 of 352 [44%]; P < .0001), pneumothorax-related intervention (eg, catheter aspiration, pleural blood patch, chest tube placement; 43 of 482 [8.9%] vs 85 of 352 [24.1%]; P < .0001), and chest tube placement along with other determinants requiring hospital admission (18 of 482 [3.7%] vs 27 of 352 [7.7%]; P < .0001). No complications related to the IPB were noted in the study group. CONCLUSIONS: Autologous IPB placement is associated with a decreased rate of pneumothorax and associated interventions, including chest tube placement and hospital admission, after CT-guided lung biopsies, with no evidence of any adverse effects. These results suggest that an IPB is safe and effective and should be considered when aerated lung is traversed while performing a CT-guided lung biopsy.

Primary hepatic angiosarcoma: multi-institutional comprehensive cancer centre review of multiphasic CT and MR imaging in 35 patients.

OBJECTIVE: To assess the imaging features of primary hepatic angiosarcoma on multiphasic CT and MR. METHODS: Multi-institutional review identified 35 adults (mean age, 57.1 years; 22M/13F) with pathologically proven hepatic angiosarcoma and pretreatment multiphasic CT (n = 33) and/or MR (n = 7). RESULTS: Multifocal hepatic involvement was seen in all 35 cases, with at least 10 lesions in 74.3% (26/35). Mean size of the dominant mass was 8.9 ± 4.7 cm (range, 2.6-20 cm). Individual nodules were typically circumscribed. Arterial-phase foci of hypervascular enhancement without washout were seen in 89.7% (26/29). Heterogeneously expanding foci of enhancement generally followed blood pool in 88.6% (31/35). Progressive centripetal (n = 16) or diffuse "flash-fill" (n = 4) enhancement pattern resembling cavernous haemangiomas predominated in 20 cases, whereas a "reverse haemangioma" centrifugal pattern predominated in 11 cases. Rapid interval growth was seen in 24 (96.0%) of 25 cases with serial imaging. Vascular invasion was not seen in any case. Underlying cirrhotic morphology was seen in 42.3% (15/35). CONCLUSION: Primary hepatic angiosarcomas typically manifest as aggressive multifocal tumors containing small heterogeneous hypervascular foci that progressively expand and follow blood pool. The appearance can mimic cavernous haemangiomas, but distinction is generally possible. In the setting of cirrhosis, lack of tumour washout and vascular invasion argue against multifocal hepatocellular carcinoma. KEY POINTS: • Hepatic angiosarcoma manifests on CT and MR as rapidly progressive multifocal tumours • Multiphasic imaging demonstrates hypervascular foci that progressively expand and follow blood pool • Enhancement pattern can resemble cavernous haemangiomas or show a "reverse" centrifugal pattern • Lack of tumour washout of hypervascular lesions argues against multifocal hepatocellular carcinoma • Careful assessment of the cross-sectional imaging findings may suggest the diagnosis.

The peroral pneumocolon revisited: a valuable fluoroscopic and CT technique for ileocecal evaluation.

The peroral pneumocolon represents a time-honored but somewhat forgotten and underutilized technique for improved ileocecal evaluation at small bowel fluoroscopy. The peroral pneumocolon entails fluoroscopically guided gaseous insufflation per rectum following the arrival of barium at the cecum at conventional small bowel follow-through examination. In most cases, high-quality double contrast evaluation of the terminal ileum can be achieved, often superior to enteroclysis examination for this critical location. The peroral pneumocolon improves diagnostic confidence, including assessment of disease activity, and may result in a reversal of the diagnostic impression. This simple procedure will be discussed and a spectrum of fluoroscopic findings with CT and endoscopic correlation will be provided to demonstrate the added yield of this technique in the evaluation of known or suspected Crohn's disease. Application of the pneumocolon technique to CT for combined small and large bowel evaluation ("CT coloenterography") will also be discussed, which represents an attractive new option for investigating inflammatory bowel disease and other bowel-related conditions. Through the use of automated low-pressure carbon dioxide delivery per rectum, supplemented by IV glucagon for relaxation of the ileocecal valve, a CT-based pneumocolon examination may prove to be a useful hybrid technique for bowel evaluation in the future.

CT-guided lung biopsies: pleural blood patching reduces the rate of chest tube placement for postbiopsy pneumothorax.

OBJECTIVE: The objective of our study was to determine whether pleural blood patching reduces the need for chest tube placement and hospital admission for pneumothorax complicating CT-guided percutaneous lung biopsy. MATERIALS AND METHODS: We reviewed 463 CT-guided lung biopsies performed between August 2006 and March 2010 to determine whether intervention for pneumothorax was required and patient outcome. Intervention was categorized as simple aspiration, aspiration and intrapleural blood patching, or chest tube placement and hospital admission. The technique for pleural blood patching consisted of complete pneumothorax aspiration, immediate placement of up to 15 mL of peripheral autologous blood into the pleural space, and positioning the patient in the ipsilateral decubitus position for 1 hour after the procedure. RESULTS: Intervention for pneumothorax was necessary in 45 of 463 patients (9.7%) and 19 of 463 patients (4.1%) required chest tube placement. Pleural blood patching as a method to treat a postbiopsy pneumothorax and avoid further intervention was associated with a significantly higher success rate than simple aspiration: 19 of 22 (86.4%) vs seven of 15 (46.7%) (odds ratio = 7.2, p = 0.03), respectively. CONCLUSION: Aspiration with intrapleural blood patching is superior to simple aspiration to treat pneumothorax associated with CT-guided lung biopsy. Pleural blood patching reduces the need for chest tube placement and hospital admission in this patient population.

Low-volume hybrid bowel preparation combining saline laxatives with oral contrast agents versus standard polyethylene glycol lavage for colonoscopy.

PURPOSE: The aim of this study was to compare the quality of low-volume hybrid computed tomography colonography bowel preparation, using both laxatives and oral contrast, with standard polyethylene glycol lavage. METHODS: The study group consisted of 300 consecutive adults (mean age, 58.3 years) who underwent colonoscopy immediately after positive computed tomography colonography. Hybrid bowel preparation for study group was <1 L in total volume, consisting of osmotic cathartic (sodium phosphate or magnesium citrate) in conjunction with oral contrast (2% barium and diatrizoate). A control group of 300 adults (mean age, 58.3 years) underwent primary colonoscopy after standard 4-liter polyethylene glycol lavage without oral contrast. The prospective preparation quality rating by the endoscopist served as the reference standard. A rating of poor/marginal was considered inadequate and adequate/good/excellent was considered diagnostic. RESULTS: The frequency of inadequate bowel preparation was 4.3% (13/300) in the study group vs 12.3% (37/300) for the control group (P < .001). Specifically, preparation was poor or marginal in 10 and 3 cases in the hybrid cohort, respectively, and in 29 and 8 cases in the polyethylene glycol cohort, respectively. Preparation quality was scored as excellent in 32% (96/300) in the hybrid cohort and 23.3% (70/300) in the polyethylene glycol cohort (P < .05). CONCLUSIONS: At colonoscopy, low-volume laxative-oral contrast hybrid preparations are effective for bowel cleansing, perhaps even more so than polyethylene glycol lavage. Beyond improvements in quality, the low-volume preparation may improve patient compliance and would allow for immediate computed tomography colonography if colonoscopy is incomplete, without the need for additional oral contrast tagging.

Noninvasive radiologic imaging of the large intestine: a valuable complement to optical colonoscopy.

PURPOSE OF REVIEW: Radiologic imaging of the large intestine continues to evolve and expand the potential for noninvasive diagnosis. The aim of this review is to provide an update on current and emerging clinical capabilities for a variety of radiologic diagnostic imaging tools for evaluating the colon and rectum. RECENT FINDINGS: The utility of computed tomography for the evaluation of symptomatic inflammatory and neoplastic conditions of the colon is well established, but the clinical role of computed tomography colonography is rapidly evolving. In addition to a number of diagnostic indications, computed tomography colonography is emerging as a potential frontline colorectal screening test for cancer prevention. MRI has become increasingly valuable for rectal cancer staging and inflammatory bowel disease but has yet to gain momentum for polyp evaluation. PET imaging has been primarily utilized for oncologic indications, but also holds considerable potential for inflammatory conditions. Other imaging modalities, such as the barium enema, conventional radiography, and ultrasound, play a much more limited role. SUMMARY: Advances in radiologic imaging of the colorectum will continue to expand the capabilities and clinical indications for noninvasive diagnosis, allowing for a greater emphasis on the complementary roles of tissue sampling and therapy with optical colonoscopy.

Value-of-information analysis to guide future research in colorectal cancer screening.

PURPOSE: To identify the most useful areas for research in colorectal cancer (CRC) screening by using a value-of-information analysis. MATERIALS AND METHODS: Cost-effectiveness of screening strategies, including colonoscopy, computed tomographic (CT) colonography, flexible sigmoidoscopy, and barium enema examination, were compared by using a Markov model. Monetary net benefit (NB), a measure of cost-effectiveness, was calculated by multiplying effect (life-years gained) by willingness to pay (100,000 dollars per life-year gained) and subtracting cost. A value-of-information analysis was used to estimate the expected benefit of future research that would eliminate the decision uncertainty. RESULTS: In the reference-case analysis, colonoscopy was the optimal test with the highest NB (1945 dollars per subject invited for screening compared with 1862 dollars, 1717 dollars, and 1653 dollars for CT colonography, flexible sigmoidoscopy, and barium enema examination, respectively). Results of probabilistic sensitivity analysis indicated that colonoscopy was the optimal choice in only 45% of the simulated scenarios, whereas CT colonography, flexible sigmoidoscopy, and barium enema examination were the optimal strategies in 23%, 16%, and 15% of the scenarios, respectively. Only two parameters were responsible for most of this uncertainty about the optimal test for CRC screening: the increase in adherence with less invasive tests and CRC natural history. The expected societal monetary benefit of further research in these areas was estimated to be more than 15 billion dollars. CONCLUSION: Results of value-of-information analysis show that future research on the optimal test for CRC screening has a large societal impact. Priority should be given to research on the increase in adherence with screening by using less invasive tests and to better understanding of the natural history of CRC.

Evaluation of submucosal lesions of the large intestine: part 2. Nonneoplastic causes.

Various nonneoplastic entities may manifest as submucosal abnormalities at colorectal evaluation, and it may be difficult to distinguish between those with an intramural origin and those with an extramural origin on the basis of optical colonoscopy alone. Cross-sectional radiologic imaging, which allows evaluation of the entire bowel wall and the surrounding tissues, plays an important role in the localization and characterization of these abnormalities. However, some superficial submucosal lesions that are initially detected at computed tomographic colonography or barium enema studies may be better characterized with colonoscopy; thus, it is important to recognize the complementary uses of these diagnostic tests. In addition, modalities such as transrectal ultrasonography and magnetic resonance imaging may be useful for the identification and characterization of some abnormalities. For timely and effective management, it is especially important that submucosal neoplasms of the large intestine be accurately distinguished from nonneoplastic entities such as lymphoid polyps, vascular lesions, and cystic lesions, as well as from extracolonic abnormalities (eg, endometriosis, uterine fibroids) and normal extracolonic structures (eg, uterus, vasculature).

Prospective blinded trial comparing 45-mL and 90-mL doses of oral sodium phosphate for bowel preparation before computed tomographic colonography.

OBJECTIVE: To compare the efficacy of computed tomographic colonography (CTC) bowel preparation using single- (45 mL) versus double-dose sodium phosphate. MATERIALS AND METHODS: A hundred consecutive patients undergoing screening CTC were randomly assigned with either single (45 mL) or double dose of sodium phosphate. Stool/fluid tagging remained constant. Two radiologists with extensive CTC experience, blinded to the groups, prospectively scored the colon for residual stool and fluid by using a 4-point scale. RESULTS: There was an excellent cleansing in both groups characterized by low stool/fluid scores. A stool score of 1 or 2 (indicating a stool-free segment or only minimal particles <5 mm) was seen in 90.3% (271/300) of segments in the single-dose group and 87% (261/300) in the double-dose group. Similarly, there was minimal residual fluid with a score of 1 or 2 (indicating <25% of lumen occupied by fluid) in 82% (488/600) of segments in the single-dose group and 87% (522/600) in the double-dose group. Overall, no significant associations were noted between the sodium phosphate regimens and residual stool/fluid in most colonic segments. In addition, no significant differences were seen in the stool or fluid tagging. CONCLUSIONS: Both single- and double-dose sodium phosphate resulted in excellent colonic cleansing without any significant differences. Tagging of residual stool and fluid was equally excellent for both groups. These findings indicate that a single 45-mL dose of oral sodium phosphate, in conjunction with stool and fluid tagging, results in high-quality CTC bowel preparation that is comparable to the clinically proven double-dose regimen.