Comparison of routine and unprepped CT colonography augmented by low fiber diet and stool tagging: a pilot study

Assessment of 3 Bowel Preparation Protocols for Computed Tomography Pneumocolonography in Normal Dogs

OBJECTIVE

To investigate the effects of 3 different bowel preparation protocols on interpretation of computed tomography (CT) pneumocolonography images.

STUDY DESIGN

Experimental crossover design.

ANIMALS

Intact male, hound-cross, research colony dogs (n=4).

METHODS

All dogs received the 3 different bowel preparation protocols for CT pneumocolonography in the same order, with a minimum of 2 weeks between protocols. For each segment of large bowel, the subjective adequacy of bowel cleansing was assessed, residual fecal and bowel volumes were calculated, and the density of fecal material in the bowel lumen was measured. Linear mixed effect models that included a random dog effect were used to evaluate mean differences in outcome measures across protocols.

RESULTS

No dogs experienced any clinical problems associated with the protocols or CT pneumocolonography. Bowel cleansing was considered adequate for CT pneumocolonography interpretation for all 3 protocols. There was a significant effect of protocol on residual fecal volumes and the fecal:bowel volume ratio, with the 2 protocols that included an extended fast producing the lowest total residual fecal volumes. There was a significant effect of protocol on maximum measured density of residual fecal material with the 2 protocols including iodinated contrast having the highest density.

CONCLUSIONS

All protocols were sufficient for CT pneumocolonography interpretation and contrast-tagging of residual fecal material was successful with oral iopamidol administration. An at-home bowel cleansing protocol may provide adequate bowel cleansing for CT pneumocolonography image interpretation.

Low-residue and low-fiber diets in gastrointestinal disease management

Recently, low-residue diets were removed from the American Academy of Nutrition and Dietetics' Nutrition Care Manual due to the lack of a scientifically accepted quantitative definition and the unavailability of a method to estimate the amount of food residue produced. This narrative review focuses on defining the similarities and/or discrepancies between low-residue and low-fiber diets and on the diagnostic and therapeutic values of these diets in gastrointestinal disease management. Diagnostically, a low-fiber/low-residue diet is used in bowel preparation. A bowel preparation is a cleansing of the intestines of fecal matter and secretions conducted before a diagnostic procedure. Therapeutically, a low-fiber/low-residue diet is part of the treatment of acute relapses in different bowel diseases. The available evidence on low-residue and low-fiber diets is summarized. The main findings showed that within human disease research, the terms "low residue" and "low fiber" are used interchangeably, and information related to the quantity of residue in the diet usually refers to the amount of fiber. Low-fiber/low-residue diets are further explored in both diagnostic and therapeutic situations. On the basis of this literature review, the authors suggest redefining a low-residue diet as a low-fiber diet and to quantitatively define a low-fiber diet as a diet with a maximum of 10 g fiber/d. A low-fiber diet instead of a low-residue diet is recommended as a diagnostic value or as specific therapy for gastrointestinal conditions.

Evaluation of two minimal-preparation regimes for CT colonography: optimising image quality and patient acceptability

OBJECTIVE

To compare a 2 day bowel preparation regime of barium, iodine and a mild stimulant laxative with a 1 day iodine-only regime for CT colonography (CTC).

METHODS

100 consecutive patients underwent CTC. The first 50 patients (Regime 1) ingested 1 bisacodyl tablet twice a day 3 days before CTC and 1 dose each of 50 ml of barium and 20 ml of iodinated contrast per day starting 2 days before CTC. The second 50 patients (Regime 2) ingested 3 doses of iodinated contrast over 24 h prior to CTC. Volumes of residual stool and fluid, and the effectiveness of stool and fluid tagging, were graded according to methods established by Taylor et al (Taylor S, Slaker A, Burling D, Tam E, Greenhalgh R, Gartner L, et al. CT colonography: optimisation, diagnostic performance and patient acceptability of reduced-laxative regimens using barium-based faecal tagging. Eur Radiol 2008; 18: 32-42). A 3 day low-residue diet was taken by both cohorts. Questionnaires rating the side-effects and burden of the bowel preparation were compared to a control cohort of patients undergoing barium enema.

RESULTS

The proportion of colons producing none/scattered stool (score 1) was 90.3% with Regime 1 and 65.0% with Regime 2 (p<0.005). Any residual stool was significantly better tagged with Regime 1 (score 5), with 91.7% of Regime 1 exhibiting optimum tagging vs 71.3% of Regime 2 (p<0.05). No significant differences in side-effects between the bowel preparation regimes for CTC were elicited. Bowel preparation for barium enema was tolerated significantly worse than both of the CTC bowel preparation regimes.

CONCLUSION

Regime 1, containing a 3 day preparation of a mild laxative, barium and iodine, produced a significantly better prepared colon, with no difference in patient acceptability.

CT colonography without cathartic preparation: positive predictive value and patient experience in clinical practice

OBJECTIVE

To determine the positive predictive value (PPV) for polyps ≥ 6 mm detected at CT colonography (CTC) performed without cathartic preparation, with low-dose iodine faecal tagging regimen and to evaluate patient experience.

METHODS

1920 average-risk patients underwent CTC without cathartic preparation. Faecal tagging was performed by diatrizoate meglumine and diatrizoate sodium at a total dose of 60 ml (22.2 g of iodine).The standard interpretation method was primary 3D with 2D problem solving. We calculated per-patient and per-polyp PPV in relation to size and morphology. All colonic segments were evaluated for image quality (faecal tagging, amount of liquid and solid residual faeces and luminal distension). Patients completed a questionnaire before and after CTC to assess preparation and examination experience.

RESULTS

Per-polyp PPV for detected lesions of ≥ 6 mm, 6-9 mm, ≥ 10 mm and ≥ 30 mm were 94.3%, 93.1%, 94.7% and 98%, respectively. Per-polyp PPV, according to lesion morphology, was 94.6%, 97.3% and 85.1% for sessile, pedunculated and flat polyps, respectively. Per-patient PPV was 92.8%. Preparation without frank cathartics was reported to cause minimal discomfort by 78.9% of patients.

CONCLUSION

CTC without cathartic preparation and low-dose iodine faecal tagging may yield high PPVs for lesions ≥ 6 mm and is well accepted by patients.

KEY POINTS

• Computed tomographic colonography (CTC) without cathartic preparation is well accepted by patients • Cathartic-free faecal tagging CTC yields high positive predictive values • CTC without cathartic preparation could improve uptake of colorectal cancer screening.

National CT colonography trial (ACRIN 6664): comparison of three full-laxative bowel preparations in more than 2500 average-risk patients

OBJECTIVE

The purpose of our study was to compare the effect of three different full-laxative bowel preparations on patient compliance, residual stool and fluid, reader confidence, and polyp detection at CT colonography (CTC).

SUBJECTS AND METHODS

A total of 2531 patients underwent CTC followed by colonoscopy for the American College of Radiology Imaging Network (ACRIN) National CTC Trial. Of this total, 2525 patients used one of three bowel preparations with bisacodyl tablets and stool and fluid tagging: 4 L of polyethylene glycol (PEG); 90 mL of phosphosoda; or 300 mL of magnesium citrate. Patients reported percent compliance with the bowel preparation and radiologists graded each CTC examination for the amount of residual fluid and stool on a scale from 1 (none) to 4 (nondiagnostic). Reader confidence for true-positive findings was reported on a 5-point scale: 1 (low) to 5 (high). Sensitivity and specificity for detecting polyps ≥ 6 mm and ≥ 1 cm compared with colonoscopy were calculated for each preparation.

RESULTS

The most commonly prescribed preparation was phosphosoda (n = 1403) followed by PEG (n = 1020) and magnesium citrate (n = 102). Phosphosoda had the highest patient compliance (p = 0.01), least residual stool (p < 0.001), and highest reader confidence versus PEG for examinations with polyps (p = 0.06). Magnesium citrate had significantly more residual fluid compared with PEG and phosphosoda (p = 0.006). The sensitivity and specificity for detecting colon polyps ≥ 6 mm and ≥ 1 cm did not differ significantly between preparations.

CONCLUSION

Polyp detection was comparable for all three preparations, although phosphosoda had significantly higher patient compliance and the least residual stool.

Impact of low-residue diet on bowel preparation for colonoscopy

BACKGROUND

Few studies have focused on the effect of dietary residue on preparation for colonoscopy.

OBJECTIVE

To determine the impact of a low-residue diet on the quality of bowel preparation.

SETTING

Chang Gung Memorial Hospital, Kaohsiung Medical Center, Taiwan.

PATIENTS

Eight hundred four consecutive patients (50.4 ± 11.6 y (range, 18-88 y), 43.6% female) undergoing colonoscopy between May 2008 and June 2009.

INTERVENTION

Subjects were advised to consume a low-residue diet for 2 days before the procedure, and they recorded food intake by use of diet diaries.

MAIN OUTCOME MEASURES

The quality of bowel cleansing was evaluated using the Ottawa bowel preparation scale. Patient variables and details of each procedure were recorded, and factors that determined the quality of colon cleansing were determined.

LIMITATIONS

Categories of foods consumed were recorded, but not the amount eaten, and diet diaries were completed retrospectively.

RESULTS

Data from 789 patients were analyzed. Only 44.2% of patients adhered to a low-residue diet, and 39.3% of patients were inadequately prepared. On multivariate logistic regression analysis, age (P = .007), body mass index (P = .01), abdominal girth (P = .041), bowel habit tending to constipation (P = .015), and high-residue diet (P < .0001) were independent predictors of inadequate bowel preparation. There was a linear relationship between dietary residue score and bowel cleanliness score (r = -0.475; P < .001).

CONCLUSIONS

A low-residue diet for 2 days of before colonoscopy improves bowel cleansing, but compliance with this advice is poor. The importance of a low-residue diet should be emphasized to patients undergoing preparation for colonoscopy.

Low-fiber diet in limited bowel preparation for CT colonography: Influence on image quality and patient acceptance

OBJECTIVE

The purpose of this study was to determine whether a low-fiber diet is necessary for optimal tagging-only bowel preparation for CT colonography.

SUBJECTS AND METHODS

Fifty consecutively enrolled patients received an iodine bowel preparation: 25 patients used a low-fiber diet and 25 used no special diet. One observer determined the tagging quality per segment on a 5-point scale (1, inhomogeneous tagging; 5, excellent preparation) and the largest size of untagged feces. Semiautomatic measurements of density and homogeneity of residual feces were performed. Patient acceptance was assessed with questionnaires. Per polyp sensitivity for polyps 6 mm in diameter and larger was calculated for two experienced observers.

RESULTS

Tagging quality was scored less than grade 5 in 15 segments (10%) in the low-fiber diet group and in 25 segments (17%) in the unrestricted diet group (p = 0.098). One piece of untagged feces 10 mm in diameter or larger was found in the low-fiber diet group, and 12 were found in the unrestricted diet group (p < 0.001). Automatic measurement of attenuation resulted in a mean value of 594 HU in the low-fiber diet group and 630 HU in the unrestricted diet group (p = 0.297). In the low-fiber diet group, 22% of patients indicated that the bowel preparation was extremely or severely burdensome; 8% of patients in the unrestricted diet group had this response (p = 0.19). Thirty-two polyps 6 mm in diameter or larger were found in the low-fiber diet group and 30 in the unrestricted diet group. Observer 1 had 84% and 77% sensitivity in detecting polyps 6 mm in diameter or larger in the low-fiber diet and unrestricted diet groups, respectively (p = 0.443), and observer 2 had 97% and 83% sensitivity (p = 0.099).

CONCLUSION

Use of a low-fiber diet in bowel preparation for CT colonography results in significantly less untagged feces and shows a trend toward better residue homogeneity.

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

BACKGROUND

To assess the accuracy of routine contrast-enhanced computed tomography for the detection of large colorectal polyps and cancer.

METHODS

The study group consisted of 100 patients who underwent abdominal computed tomography and optical colonoscopy evaluation before any treatment or intervention. Invasive colorectal carcinoma and large polyps (>or=10mm) were found at colonoscopy in 29 and 16 patients, respectively. Computed tomography studies with oral and IV contrast were retrospectively reviewed as 5-mm thick sections in standard soft tissue windows by 3 readers. The readers scored each segment for polyp or cancer utilizing a 5-point scale for receiver operating characteristic analysis.

RESULTS

By-patient sensitivity/specificity for cancer detection for each reader was 69.0%/88.7%, 65.5%/84.5%, and 82.8%/77.5%, respectively. Pooled sensitivity, specificity, and accuracy for cancer was 72.4%, 83.6%, and 80.3%, respectively. The empiric area under the receiver operating characteristic curves for the readers ranged from 0.775 to 0.857. By-patient sensitivity for large polyps was poor with a pooled sensitivity of 14.5%.

CONCLUSIONS

Standard computed tomography not tailored to colorectal investigation was moderately effective for detecting invasive cancers, but insensitive for large polyps. Unsuspected cancer should be a part of the standard search pattern for routine computed tomography interpretation, but more advanced colonography techniques are necessary for detecting large polyps.

Limited-preparation CT colonography in frail elderly patients: a feasibility study

OBJECTIVE

Full colonic preparation can be onerous and may be poorly tolerated in frail elderly patients. The purpose of this study was to prospectively assess the image quality and diagnostic yield of limited-preparation CT colonography (CTC) in elderly patients with suspected colorectal cancer who were deemed medically unfit or unsuitable for colonoscopy.

SUBJECTS AND METHODS

A prospective study was performed of 67 elderly patients with reduced functional status referred for CTC. Participants were prescribed a limited bowel preparation consisting of a low-residue diet for 3 days, 1 L of 2% oral diatrizoate meglumine (Gastrografin) 24 hours before CTC, and 1 L of 2% oral Gastrografin over the 2 hours immediately before CTC. No cathartic preparation was administered. All colonic segments were graded from 1 to 5 for image quality (1, unreadable; 2, poor; 3, equivocal; 4, good; 5, excellent) and reader confidence. Clinical and conventional colonoscopy follow-up findings were documented, and all colonic and extracolonic pathologic findings were documented.

RESULTS

Overall image quality and reader confidence in the evaluation of the colon was rated good or excellent in 84% of the colonic segments. Colonic abnormalities were identified in 12 patients (18%), including four colonic tumors, two polyps, and seven colonic strictures. Incidental extraintestinal findings were detected in 43 patients (64%), including nine patients with lesions radiologically consistent with malignancy.

CONCLUSION

Limited-preparation low-dose CTC is a feasible and useful minimally invasive technique with which to evaluate the colon and exclude gross pathology (mass lesions and polyps > 1 cm) in elderly patients with diminished performance status, yielding good to excellent image quality.

Performance of CT colonography in clinical trials

The amount of data accumulated in trials of CT colonography (CTC) has greatly increased in the past decade. The information from these studies is shaping clinical practice and public health policy regarding screening for colorectal cancer (CRC). This article examines the performance of CTC in clinical trials for individuals at average risk and increased risk for CRC. It also addresses the efficacy of CTC after incomplete colonoscopy, when colon preparations are reduced or eliminated, and in academic versus nonacademic environments. The data suggest that CTC is effective especially for the detection of larger lesions and when more advanced imaging technology is used.

CT colonography with decreased purgation: balancing preparation, performance, and patient acceptance

OBJECTIVE

Reduction or elimination of catharsis with fecal tagging enhances the tolerability of CT colonography (CTC) and may increase compliance with colorectal cancer (CRC) screening recommendations. We systematically reviewed studies that prospectively evaluated performance and patient satisfaction with decreased-purgation CTC and with optical colonoscopy.

CONCLUSION

The nine studies reviewed showed moderate-to-good performance for decreased-purgation CTC; however, data are limited, and study design and data presentation are inconsistent. Further study of decreased-purgation CTC and standardization of terminology are needed.

Comparative evaluation of the fecal-tagging quality in CT colonography: barium vs. iodinated oral contrast agent

RATIONALE AND OBJECTIVES

The purpose of this evaluation was to compare the tagging quality of a barium-based regimen with that of iodine-based regimens for computed tomographic (CT) colonography.

MATERIALS AND METHODS

Tagging quality was assessed retrospectively in three different types of fecal-tagging CT colonographic cases: 24 barium-based cases, 22 nonionic iodine-based cases, and 24 ionic iodine-based cases. For the purpose of evaluation, the large intestine was divided into six segments, and the tagging homogeneity of a total of 420 segments (70 patients) was graded by three blinded readers from 0 (heterogeneous) to 4 (homogeneous).

RESULTS

For barium-based cases, the average score for the three readers was 2.4, whereas it was 3.4 for nonionic iodine and 3.6 for ionic iodine. The percentages of segments that were assigned scores of 4 (excellent tagging [100%]) were 11.6%, 61.9%, and 72.9% for the barium-based, nonionic iodine-based, and ionic iodine-based regimens, respectively. The homogeneity scores of iodine-based fecal-tagging regimens were significantly higher than those of the barium-based fecal-tagging regimen (P < .001). The CT attenuation values of tagging in the cases were also assessed: the minimum and maximum values were significantly higher for the iodine-based regimens than for the barium-based regimen (P < .001).

CONCLUSIONS

The iodine-based fecal-tagging regimens provide significantly greater homogeneity in oral-tagging fecal material than the barium-based fecal-tagging regimen. Iodine-based fecal-tagging regimens can provide an appropriate method for use in nonlaxative or minimum-laxative CT colonography.

CT colonography with minimal bowel preparation: evaluation of tagging quality, patient acceptance and diagnostic accuracy in two iodine-based preparation schemes

Purpose

The aim of this study was to compare a 1-day with a 2-day iodine bowel preparation for CT colonography in a positive faecal occult blood test (FOBT) screening population.

Materials and methods

One hundred consecutive patients underwent CT colonography and colonoscopy with segmental unblinding. The first 50 patients (group 1) ingested 7*50 ml iodinated contrast starting 2 days before CT colonography. The latter 50 patients (group 2) ingested 4*50 ml iodinated contrast starting 1 day before CT colonography. Per colonic segment measurements of residual stool attenuation and homogeneity were performed, and a subjective evaluation of tagging quality (grade 1–5) was done. Independently, two reviewers performed polyp and carcinoma detection.

Results

The tagging density was 638 and 618 HU (p = 0.458) and homogeneity 91 and 86 HU for groups 1 and 2, respectively (p = 0.145). The tagging quality was graded 5 (excellent) in 90% of all segments in group 1 and 91% in group 2 (p = 0.749). Mean per-polyp sensitivity for lesions ≥10 mm was 86% in group 1 and 97% in group 2 (p = 0.355). Patient burden from diarrhoea significantly decreased for patients in group 2.

Conclusions

One-day preparation with meglumine ioxithalamate results in an improved patient acceptability compared with 2-day preparation and has a comparable, excellent image quality and good diagnostic performance.

Efficacy of barium-based fecal tagging for CT colonography: a comparison between the use of high and low density barium suspensions in a Korean population - a preliminary study

OBJECTIVE

This preliminarily study was designed to determine and to compare the efficacy of two commercially available barium-based fecal tagging agents for CT colonography (CTC) (high-density [40% w/v] and low-density [4.6% w/v] barium suspensions) in a population in Korea.

MATERIALS AND METHODS

In a population with an identified with an average-risk for colorectal cancer, 15 adults were administered three doses of 20 ml 40% w/v barium for fecal tagging (group I) and 15 adults were administered three doses of 200 ml 4.6% w/v barium (group II) for fecal tagging. Excluding five patients in group I and one patient in group II that left the study, ten patients in group I and 14 patients in group II were finally included in the analysis. Two experienced readers evaluated the CTC images in consensus regarding the degree of tagging of stool pieces 6 mm or larger. Stool pieces were confirmed with the use of standardized CTC criteria or the absence of matched lesions as seen on colonoscopy. The rates of complete fecal tagging were analyzed on a per-lesion and a per-segment basis and were compared between the patients in the two groups.

RESULTS

Per-lesion rates of complete fecal tagging were 52% (22 of 42; 95% CI, 37.7-66.6%) in group I and 78% (28 of 36; 95% CI, 61.7-88.5%) in group II. The difference between the two groups did not reach statistical significance (p = 0.285). The per-segment rates of complete tagging were 33% (6 of 18; 95% CI, 16.1%-56.4%) in group I and 60% (9 of 15; 95% CI, 35.7%-80.3%) in group II; again, the difference between the two groups did not reach statistical significance (p = 0.171).

CONCLUSION

Barium-based fecal tagging using both the 40% w/v and the 4.6% w/v barium suspensions showed moderate tagging efficacy. The preliminary comparison did not demonstrate a statistically significant difference in the tagging efficacy between the use of the two tagging agents, despite the tendency toward better tagging with the use of the 4.6% w/v barium suspension.

Image quality and patient acceptance of four regimens with different amounts of mild laxatives for CT colonography

OBJECTIVE

The purpose of our study was to prospectively evaluate image quality and patient acceptance of CT colonography (CTC) with fecal tagging using different levels of catharsis.

SUBJECTS AND METHODS

Forty consecutive increased-risk patients were randomized. Group 1 received orally 20 mg of bisacodyl, group 2 received 30 mg of bisacodyl, group 3 received 20 mg of bisacodyl and 8.2 g of magnesium citrate, and group 4 received 30 mg of bisacodyl and 16.4 g of magnesium citrate. All patients used a 2-day low-fiber diet and received diatrizoate meglumine and barium for fecal tagging. One reviewer blindly scored subjective image quality (fecal tagging, amount of residual feces [liquid or solid], luminal distention, and image readability) on a 5- to 6-point scale using a 2D review technique. The mean and SD of attenuation of tagging were measured as well as the relative SD as a measure of homogeneity. Furthermore, patient acceptance (burden related to diarrhea, abdominal pain, flatulence, and overall burden) was evaluated. Ordinal regression, generalized estimating equations, and parametric and nonparametric tests were used for analysis.

RESULTS

Image readability was evaluated as good or excellent in all examinations except one in group 2 (nondiagnostic) and two in group 3 (moderate). Group 2 contained more feces than group 4 (p = 0.04). With regard to mean attenuation and homogeneity of tagging, no significant differences were observed between groups. Group 4 experienced more severe diarrhea than groups 1 and 2 and higher overall burden than groups 1 and 3 (p < 0.042).

CONCLUSION

The mildest preparation with 20 mg of bisacodyl provided good image quality of CTC images. Increasing the amount of laxatives did not improve image quality or tagging characteristics but was associated with a lower patient acceptance.

Colonography by CT, MRI and PET/CT combined with conventional colonoscopy in colorectal cancer screening and staging

Colorectal cancer (CRC) remains a leading cancer killer worldwide. But the disease is both curable and preventable at an early stage. Regular CRC cancer screening has been shown to reduce the risk of dying from CRC. However, the importance of large-scale screening is only now starting to be appreciated. This article reviews a variety of imaging procedures available for detecting ulcerative colitis (UC) and Crohn’s disease (CD), polyps and CRC in their early stage and also presents details on various screening options. Detecting, staging and re-staging of patients with CRC also require multimodality, multistep imaging approaches. Staging and re-staging with conventional colonoscopy (CC), computer tomography colonography (CTC), magnetic resonance colonography (MRC) and positron emission tomography/computer tomography colonography (PET/CTC) are of paramount importance in determining the most appropriate therapeutic method and in predicting the risk of tumor recurrence and overall prognosis. The advantages and limitations of these modalities are also discussed.