BACKGROUND: The usefulness of currently available colon imaging tests, including air contrast barium enema (ACBE), computed tomographic colonography (CTC), and colonoscopy, to detect colon polyps and cancers is uncertain. We aimed to assess the sensitivity of these three imaging tests. METHODS: Patients with faecal occult blood, haematochezia, iron-deficiency anaemia, or a family history of colon cancer underwent three separate colon-imaging studies--ACBE, followed 7-14 days later by CTC and colonoscopy on the same day. The primary outcome was detection of colonic polyps and cancers. Outcomes were assessed by building an aggregate view of the colon, taking into account results of all three tests. FINDINGS: 614 patients completed all three imaging tests. When analysed on a per-patient basis, for lesions 10 mm or larger in size (n=63), the sensitivity of ACBE was 48% (95% CI 35-61), CTC 59% (46-71, p=0.1083 for CTC vs ACBE), and colonoscopy 98% (91-100, p<0.0001 for colonoscopy vs CTC). For lesions 6-9 mm in size (n=116), sensitivity was 35% for ACBE (27-45), 51% for CTC (41-60, p=0.0080 for CTC vs ACBE), and 99% for colonoscopy (95-100, p<0.0001 for colonoscopy vs CTC). For lesions of 10 mm or larger in size, the specificity was greater for colonoscopy (0.996) than for either ACBE (0.90) or CTC (0.96) and declined for ACBE and CTC when smaller lesions were considered. INTERPRETATION: Colonoscopy was more sensitive than other tests, as currently undertaken, for detection of colonic polyps and cancers. These data have important implications for diagnostic use of colon imaging tests.

Barium Sulfate↗

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Transcatheter electrocoagulation: a therapeutic angiographic technique for vessel occlusion.

Previous work has shown that localized electrocoagulation of blood vessels using direct current applied by catheter placed electrodes is feasible. In vitro and in vivo experiments showed that clot size and thrombosis of vessels are directly related to the product of the amount and duration of the current. Surgically created splenic hemorrhage was well controlled in 9 of 10 animals. The vessels remained permanently occluded after electrocoagulation in 8 of 9 animals. Pathological studies of all the vessels showed intimal damage at the sites of occlusion. These experiments indicate that clot formation may be a product of both intimal damage and platelet attraction to the positive electrode. The technique has advantages over embolization since no foreign material is injected and a localized clot is produced at the tip of the guidewire. There are certain disadvantages and further refinements must be developed to establish transcatheter electrocoagulation as a useful clinical technique for vessel occlusion.

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Effect of iopanoate on the biliary and urinary excretion of iodipamide.

The effect of sodium iopanoate and iopanoic acid on the biliary excretion of iodipamide in dogs was studied. Enteric administration of sodium iopanoate within one hour of iodipamide infusion reduced biliary iodipamide excretion and increased urinary iodipamide output. The biliary and urinary excretion of iodipamide was not influenced by iopanoic acid administered 40 and then again 16 hrs before iodipamide. These results suggest that iodipamide cholangiography can be employed 16-18 hrs after a standard two-day iopanoic acid oral cholecystogram without decreasing the ability to visualize the biliary ductal system or increasing the urinary iodipamide excretion.

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Transcatheter electrocoagulation: experimental evaluation of the anode.

Transcatheter electrocoagulation using direct current has been shown to be an effective method for vessel occlusion. To date, the stainless steel anode has not been entirely satisfactory. Thus, an evaluation of bipolar platinum electrodes and a comparison of monopolar platinum and stainless steel electrodes have been performed. Experimental results have shown that both monopolar and bipolar platinum electrodes caused perforation in most cases. At the present time, we have not found a satisfactory replacement for the unipolar stainless steel anode.

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Effect of B-15,000 (Iopamidol), a new nonionic contrast agent, on cardiac function of the isolated rat heart.

The isolated rat heart model was used to examine the effect of a new nonionic contrast agent, B-15,000 (Iopamidol), on cardiac function. Comparative studies were performed with Amipaque, Renografin 60, Renografin 76, and Vascoray. The three ionic contrast agents had significantly greater detrimental effects on cardiac function than either nonionic agent. The results support the continued evaluation of the nonionic agents for use in coronary angiography.

Angiography↗

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Factors in the intestinal absorption of oral cholecystopaques.

Interest in the pharmacokinetics of cholecystopaques initially centered on transport from blood to bile. The data obtained in this effort have been valuable and have shown that the maximal iodine concentration achievable in the bile is quite similar for all of the currently available compounds. This concentration is, of course, dose dependent. the transport of contrast material from the bowel to the blood has been shown to be quite variable. Considerable progress was made in understanding this. The tremendous differences in absorption of iopanoic acid depending upon the pH of the administered solution was an initial revelation. The development of the concept that there is a water layer through which the cholecystopaque must pass before reaching the lipid membrane of the intestinal cell has added clarity to understanding the difference in absorption between water-soluble and water-insoluble cholecystopaques. A complete knowledge of what might enhance or inhibit absorption is not known. There is beginning to be an understanding of how intestinal dose relates to plasma levels. This should lead to an optimal dose-timing scheme for each cholecystopaque. The basic assumption is that the highest iodine concentration in the gallbladder leads to the most accurate cholecystography. If this is true, the gallbladder needs to be offered bile at the maximum concentrations during the period preceding filming. To accomplish this, the appropriate plasma level necessary for maximum excretion is needed. Experimental data suggest that our current clinical methods in regard to dose and dose timing need revision to optimize cholecystography. This revision needs to take place with a careful look at toxicity. Accepting the present premise that oral cholecystography can be improved, perhaps without a significant increase in morbidity, a fundamental question to be asked is: is it worth it?

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Transcatheter electrocoagulation of the pulmonary artery: an experimental model in dogs for studying pulmonary thrombosis.

Transcatheter electrocoagulation (TCEC) has been shown to produce permanent arterial occlusion. This study was performed to evaluate the potential of using TCEC of the pulmonary artery as an experimental model of pulmonary thromboembolism. Fourteen lobar or first-order pulmonary arteries were occluded in ten dogs in the acute studies. Eight pulmonary arteries were occluded in eight dogs that were sacrificed 25 to 85 days after TCEC. There were permanent occlusions in seven, and all seven evidence of pulmonary infarction. The animals tolerated the procedure well. The technique may have merit as an experimental model for studying pulmonary thrombosis and infarction.

Animals↗

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Effect of increasing current and decreasing blood flow for transcatheter electrocoagulation (TCEC).

Arterial occlusion by direct-current transcatheter electrocoagulation (TCEC) has been developed experimentally and used successfully in clinical situations. The major shortcoming of the technique has been the lengthy time necessary for occlusion of larger arteries. In the present study we attempted to decrease the time necessary for TCEC occlusion of the renal and femoral arteries of heparinized mongrel dogs. The results showed that the occlusion time could be significantly decreased, either by increasing the TCEC current from 15 ma to 30 or 60 ma, or by using a Meditech balloon catheter to occlude the artery during TCEC. The combination of higher current and simultaneous balloon occlusion consistently produced permanent occlusion of arteries up to 7 mm in diameter in 15 minutes or less. Balloon occlusion with TCEC is significantly faster than without this modification and makes the technique of TCEC more applicable for human use and for continued experimental study than any previous refinements.

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