[BLANK_AUDIO] So let's talk about the fecal tagging agents, what are some of the different agents that are used. You can add this as a single agent or you can use two agents, which would include barium and Iodinated contrast. Now when you use only barium it's important you use high concentration of barium.
Tagitol or concentration 40% weight by volume barium is very important to use. The bowel is more dry because you'll not use the water-soluble contrast which, as I mentioned earlier, draws in fluid into the lumen of the bowel. Of course, it depends on the laxative that
you use. If patient has GoLYTELY or clean prep electrolyte preparation, of course there'll be a lot of retained fluid in the bowel so that may preclude proper interpretation of the CT colonography. Not all stool particles will get tagged, and I'll show an example of that, it can sometimes
throw in a false positive in some of these patients. Lets now talk about fecal tagging agents using two agents. In the regimen that is used, we use Barium and water-soluble
contrast which can either be Telebrix or Gastografin. The advantages of using two different types of fecal tagging agents is that it will tag both the liquid and the stool particles. The water-soluble contrast will help you to tag the liquid component whereas the barium will help you to tag the stool particles used.
It will go through some of the crevices in the stool to tag it so we can identify the stool particles well. One has to do his/g electronic subtractions, as you can see image on the right, before and after subtraction. And the top image shows contrast in the colon that's tagged properly with the water-soluble contrast, and the image on the
bottom is after subtraction, when the entire fluid has been subtracted out to so you can see the entire colon really well. Now one more important thing to remember is that Telebrix and Gastografin are osmotic agents, so they will draw fluid into the lumen of the bowel, and they will leave the bowel much wet. So if you're using Pico Salax it's not an issue. But if you use electrolyte
preparation, it'll increase the volume of fluid retained in the colon, and therefore make your interpretation a little more difficult than if you use the Pico Salax laxative. Let's go to each one of the water-soluble contrast carefully. So Gastografin is high hyperosmolar
contrast. It contains sodium and meglumine
components. And it is important that you don't use straight Gastografin because it can cause high density within the lumen of the bowel and cause beam hardening effect. And cause artifacts in the colon. So it's important to dilute the contrast when you're giving the instructions to the patients. Telebrix, which is given orally of course, is also hyperosmolar. Again, you have to dilute the contrast
to ensure that you don't get the beam hardening effect if you use straight contrast. The contraindication, both of these agents of course are, severe renal disease and Previous Contrast reactors. There had not been many incidences of Contrast reactions with Telebrix and Gastografin, but one has to be aware that there's some absorption of Gastografin into the colon. And especially in a cleansed colon,
which is quite vascular in some of the patients. There was a study done that was reported in the Canadian Association of Radiologists, in 1991, that compared Gastografin and Telebrix for CT scan. And patients found Telebrix more to palatable than Gastografin. Not much harm if you tasted it but it's not very tasty, especially Gastografin, it's quite bitter, and patients sometimes
throw up. So if you give that agent as one of the fecal tagging agents, patient may have server nausea and vomiting, which will then cause your [INAUDIBLE] profession technique to be difficult for the patient. Sometimes the stool will not get tagged, and as I mentioned earlier, you can
sometimes get beam hardening effect
if there is too dense contrast, especially with barium. And I'll give an example, a patient where we gave barium as the fecal tagging agent, and patient got obstructed, and had to undergo emergency surgery afterwards. These are images from a patient who had fecal tagging agents given. You can see image at the top, are between images on the same patient, one with and one without
subtraction. And the image at the bottom is endoluminal view showing what looks like a pedunculated sessile polyp hanging off the wall of the colon. However, when you see the 2D image you can see this resting in the pool of barium. And on the 2D subtracted image, the lesion is again seen, but if you look very carefully, there actually is air within this lesion. In a endoluminal view, it was
very hard to know whether this is a true polyp or whether it is a fecal matter. So therefore, wherever there is an issue regarding non-tagging of stool particles, it is best to use a 2D imaging to try and assess whether it's real polyp or whether it's stool particles. Incomplete subtraction is another pitfall that I want us to avoid. Here is a case we had
earlier on the practice. Sometimes there is tagging of the mucus
and the fluid in the bowel, but when you use the electronic subtraction software, it may not remove the particular component of the fecal agent. So in this case, you can see the image in the top is a 2D view of a patient who had fecal tagging agent. It's a subtracted view, and yet there's a line of contrast just leering out. Looks
like as though the barium is just hanging in the air. When you look at the subtracted view, you can see that there is contrast fluid hanging in the lumen of the bowel, and we cannot see behind this unsubtracted contrast so that we can list some of the polyps in these patients. So, when you get this, it's best to look at 2D imaging again, to ensure that you're not missing any polyps or any cancers.
Here's another pitfall that we had in a practice earlier on. Inadequate subtraction of the fecal tagging agents. The view on the left is an endoluminal view that shows multiple filling/g defects on top of a horse/g trough/g, whereas on the 2D we can see actually they're just stool particles or dense barium particles that did not
get subtracted during the use of the electronic software. Let's talk about fecal tagging in patients with incomplete colonoscopies.
Most often patients would be sent to you with incomplete colonoscopies because either the patient had difficulty in having the colonoscopy done because of technical difficulties or, patient is in severe pain, or the patient incomplete colonoscopies and there's high suspicion
for neoplasm or any polyps in the colon. The suggested regimen for these patients are using diluted barium and Telebrix. The patient will drink the barium and the telebrix, and then scan two to three hours later. One of the problems that we face in these patients is that, barium which is used to tag the stool particles, sometimes takes few hours, rather than just two to three hours.
May take a whole evening to try and tag the stool particles. So is it necessary to use barium in this patients? Secondly, if you use Telebrix or Gastografin which is hyperosmotal or high osmolarity/g, it can sometimes draw in fluid into the lumen. As you are aware, [UNKNOWN] patients have had no food or no drinks for about 24 hours, and they've
come to the endoscopy suite/g, and then to you after having fasted for so many hours. Patient may become hypertensive, so it's important to remember that if you're going to use fecal tagging
agents, to try and hydrate the patient before you start giving them the Telebrix, or the Gastografin or the barium. One of the issues that we face with patients with incomplete colonoscopies is that they have retained stool or unprepared bowel. So is it necessary to do the CT colonography on the same day as incomplete colonoscopy? I would suggest that patients who have unprepared bowel where you
may miss significant colonic polyps to re-book the patient with the proper two to three day bowel preparation, so you increase the sensitivity of detecting polyps in these patients. I mentioned earlier about impaction of barium in patients who have CT colonography.
This is a young girl who had obstructing
carcinoma of the sigmoid colon and she had a colonoscopy performed which is incomplete. You are asked to perform a CT colonography to look at the rest of the bowel and of course the stage of the cancer. So we gave her some barium to drink, and we did the CT colonography, and you can see in the image, we can see the constricting lesion in the descending colon, which extend into the sigmoid colon, and
there's a large amount of barium that's impacted in the right colon. This patient actually became acutely ill that evening and had to undergo emergency colectomy and an ileostomy because the bowel had perforated around the cecal region. So whenever we have a patient with a constricting lesion, it's important to be aware not to use high volume of barium or high density barium which may
impact the colon and cause complications. What about inflammatory bowel disease and the role of CT colonography. Many patients who
have inflammatory bowel disease, especially Crohn's disease, will have strictures. And in the evaluation of colon for the manage of the inflammatory bowel disease, the endoscopist will do colonoscopy. If there is a stricture or they have trouble getting through, then it
will be hard to see the rest of the colon. Sometimes we would like to see how many strictures there are in the colon which will dictate the manage of the patient. It could either be medical management or certain/g surgical/g management. It will require that we assess the entire colon with a CT colonography. Essentially, we're looking for multiple strictures or if any malignancy
exists in the colon then to stage the cancer at the same time. So let me show and example of patient who had inflammatory bowel disease, and had a CT scan performed first, and then subsequently,
endoscopy performed. This is a patient who had known Crohn's disease, had FLAIR/g of inflammatory bowel's disease, and the CT scan was performed. On the CT scan images that are shown here there are strictures in the
portion of the semicolon. The patient underwent a colonoscopy and the endoscopist did not see any strictures. So you wondered, did he miss something? Was there something around or extraluminally that be causing the stricture that he could not see at endoscopy. So they asked us to perform a CT colonography. What we did was, we used fecal tagging agents, in this patient, to perform a CT colonography.
The image on the right show contrast-enhanced CT scan with fecal tagging agents and distended colon. And I'm just gonna show you close up of the part of the bowel. Distending colon where the CT scan showed a stricture there actually no stricture seen. And their is no extraluminal mass either. But if you look very carefully at the wall of the bowel, there is some thickening there, or on the anterior wall of the ascending colon. But it's
hard to know whether there's any active disease or not. Patient had colonoscopy performed, I'm showing you two images from the same area on the endoluminal view of CT colonography, and the endoscopic view to show comparisons as to what we see and what they see. There was significant changes of active Crohn's disease on CT colonography, whereas on endoscopy we really don't see that many findings. As you
saw on the CT 2D images we could not reassure that there was any active disease. Therefore, it is suggested that try not to use fecal tagging agents in patients who have inflammatory bowel disease. It'll mass on the subtle enhancement that is seen in patients of Crohn's disease. And we rely on some of those findings such as mucosal enhancement,
mural thickening, increased vascularity, and sometimes submucosal fat to distinguish between active Crohn's disease and subacute or chronic Crohn's disease. Here's an example of a patient who had Crohn's disease, and we performed a stagging CT colonography without fecal tagging agents. You can see quite nicely in the transverse colon, there's
mucosal enhancement, marked thickening of the wall of the transverse colon, and also increased vascularity in this patient. And there was actually phlegmon in the mesentery of the transverse colon. So this was quite nicely shown. If you had used fecal tagging agents, we could missed some of the mucosal findings in terms of
assessing whether it's acute or chronic colitis. Now let's talk about some of the preparations that are used by different centers. Essentially, the different bowel preparations
that are used different centers. We use all these fecal tagging agents, and sometimes some place use vigorous bowel preparation. What
I mean by that is that I use the mechanical flush laxative such as GoLYTELY to flush out the colon. Some places use limited bowel preparation. Where you use only Dulcolax/g tablets or just small volume Pico Salax only with the fecal tagging agents. Some places use vigorous bowel preparation and reckless suppository of Dulcolax
to try and cleanse the left colonic fluid so as to increase your confidence/g leveling interpreting the colonic examination. Some centers use only fecal tagging agents, and did no bowel preparation. Again those are very few centers, and we've not had any practice in this as yet. [BLANK_AUDIO] Let's show you some of the different schedules that we have
and to give instructions to the patient. At our center, we use large volume of barium and large volume of Telebrix contrast as a fecal tagging agent. Essentially, the patient starts the preparation day before the examination. They take one package of Pico Salax the morning before the examination. And they drink 250 cc of dilute
barium. So they take a liter of water, and then put barium in it dilute down to less than 1% weigt by volume, and then drink 250 cc in the morning. And then at lunch time, they drink another component of the barium, and of course the second package of Pico Salax . And in the dinner time they take another contrast of barium, and in the evening, before they go to bed, they take the Telebrix to try and coat the
liquid that may be left behind in the colon. So this is a vigorous bowel preparation with large volume of fecal tagging agents. The second regimen that's used by radiologists from Victoria BC is vigorous bowel preparation and reckless suppository to try and cleanse the bowel. What they do is they actually use low volume fecal tagging
agents. Again like us, they use Pico Salax laxative as the first dose in the morning. They drink full pass/g in barium. So they have this one container of 200 ccs of barium, and they drink 100 cc straight without diluting it. And then the patient drinks the second early quart/g of barium in the afternoon. And then they they drink
the Telebrix in the evening, day before the examination. They also ask patients to take reckless suppository in the evening of the examination, sorry, before the examination. This is to try and cleanse the left colon of liquid which then help us to have a relatively dry bowel. In the morning of the examination, again, the patients are asked to take a
reckless suppository to clean as much of the liquid in the left colon as possible. Try and have as clean a bowel as possible. So their regiment dictates that the patient takes low volume barium, low volume Telebrix, and reckless suppository try and get as clean a bowel, as less
wet a bowel as possible to try and increase the confidence in interpreting the studies. So let's look at some of the bowel preparations used by different authors in literature, in the recent years. Pickhardt
used sodium phosphate or Fleet Phospho-Soda, I will talk about it in a second. Iannoccone/g who used no laxative
but used fecal tagging agents only. Judy Yee used Mag Citrate and GoLYTELY as the laxative for her patients. And Macari used Sodium Phosphate and PEG, or the electrolyte preparation as a laxative.
As you're aware Fleet Phospho-Soda has been pulled off the market cause of severe renal failure in some of these patients? So it's no longer used, at least in Canada, in patients. Now let's review the literature in terms of the bowel preparation and what
I'll refer to the article in Radiology, Volume 247, where they use gentle laxative and Dulcolax tablets as the laxative in bowel preparation. The second is a noncathartic CT colonography where they did not use laxative. Again reported in AJR 2008. So let's go through one at a time. The study that used limited bowel
preparation for CT colonography, they used low fiber diet for two days, and patients did not take any oral laxative except for Dulcolax tablets. And they were given two doses. The patients given high density barium over a certain time period, and they were also given Telebrix as the agent to tag the liquid that may be left behind. So this is just to show you a summary of what
they'd done in terms of the fecal tagging agents and the laxative. The results showed the patients who had polyps more than 10 mm or larger, with limited bowel preparation, the sensitivity was very good, 82%. Again, just to show you an image that they showed in the article, they showed large volume of stool in the colon which is tagged with the barium and the water-soluble fecal tagging agents. And this
is a non-subtracted view, so I'm not sure what it looked like when they actually subtracted to see the colon. [BLANK_AUDIO] The next article that I will discuss is one in AJR 2008, performed by Johnson and the team. They looked 114 patients, and they used a very unusual method of giving the fecal tagging
agents. The patient went on a normal diet. They did not get any laxatives. But the fecal tagging agent was given different ways. They did not have the patient drink the barium but take barium tablets or barium capsules which was easy to take for some of these patients. They did give barium one hour before the examination so try and tag the later part of the bowel with the main/g stool. Let's look at the results.
This was a no laxative high risk group where they looked at subtraction, it was a non-subtraction technique in interpreting the CT colonography studies. They only did 2D reading. They suggested the endoluminal reading would sometimes miss or overcall polyps because there's so much stool left behind. They looked at the polyp side between 9, sorry, 6-9MM. The
sensitivity without stool subtraction, so when they just looked at the colon as is, just used the electronic subtraction, the sensitivity for 9 millimeter polyps was about 88%. For 10 milimetre polyps or more there was quite a high sensitivity of picking up these polyps. Now when they brought in the electronic subtraction as the other component of the interpretation tool, they found the sensitivity increased
dramatically for polyps with 6-9 milimetres. And of course, the larger polyps are easily detected cause the electron subtraction removed the fecal tagged stool and liquid in this space/g. So the suggestion was, when interpreting studies with fecal tagging agents, it's important
to remember that there's heterogeneous tagging of stool particles in many patients. And that there could be a variable colonic transit
time which will preclude proper coating of some of the stool particles in some patients. And of course, when there's partial volume effects it can sort of mimic or cause problems interpretation of the study ,especially if the stool particles adhere to the colonic wall. When you're using fecal tagging agents, which we all do now, it's important to remember
that you must use 2D interpretation as a standard technique, and use the 3D as a problem-solving rather than your primary interpretation mode of imaging studying. And also you have to have a very good suppression technique or at least electronic software that'll provide you good suppression technique to remove the stool particles from the
colon. I showed you early on where we had a case with patient who was in incomplete colonoscopy and poor preparation, and we'd tagged the stool really well, with a software that we had, it did not subtract out the stool particles. And therefore, we probably missed the colon lesion that was seen. Here is a nice example of patient who had a small polyp that, I don't have an endoluminal view,
but on the endoluminal view it looked like a thick fold. But on the 2D you can see the polyp quite nicely, which both on supine and prone did not move at all, but is covered with barium. And we can sometimes overcall it as a thick fold on endoluminal view. So beware, and use 2D as a primary mode of interpretation in fecal tagging studies.
One of the most important components of your [INAUDIBLE] colonography
to back, they're not together in sheet. The first component, of course, is actual preparation itself. Day 1, before the day of the examination, bowel cleansing instructions. We give them exact details how to take, what to take. The bottom part of the first page actually
is how to mix the contrast, and detailed instruction. There's phone numbers, which are not included here that we provide for the patient to call us if there's an issue. The section on the right actually is detailed instructions as to what they can eat or drink during the preparation phase, because sometimes patient with a lot of questions, can they drink coffee? Can they drink alcohol? Can they
drink red liquids because endoscopies don't like you using red tinged drinks because it sometimes mars or masks the the colonic lesion, or they may think there's a bleeding point in an area of abnormal bowel. So we don't care about that. We actually can drink any color fluid the patient can get handle of. We give them detailed instructions as to what they can take and what they
can't take. Now, for the severely constipated, again we provide them nice outlay of instructions, how to start. Day 1, day 2, low residue diet, and we have some instructions what low residue diet means. So they have a good understanding of what they can take or can't take. They can see the instructions are given on the pre-colonography day preparation. So to summarize, bowel preparation
is a very important component of CT colonography examination.
It is best to start with one regimen, and when you do plan to change, it's best to first audit your studies and see what is the issue that your dealing with that may want you to change the regimen of the bowel preparation. When you make the changes, it's important to know why you're making
the change. Is it because the patient is uncomfortable? Is it because the bowel is too wet or the fecal tagging agents cause beam hardening effect? Or you've got poor subtraction or poor tagging of stool particles? What can you do to decrease those pitfalls? It's important not to give too large a volume of barium. The Victoria BC perforation actually uses small volume of fecal tagging agents. It's good for
the patients, but they don't wanna drink too much liquid. And also provides better cleansing and less liquid left in your colon for proper interpretation of the CT colonography studies. And of course, you remember that if you increase the fecal tagging agents, wwhether you add Gastografin or add more barium, you will incur more cost to the patient and/or to the department if you're providing
the patient with free fecal tagging agents. So in this presentation, I've given you giving you guidelines on how to start CT colonography program with bowel preparation, and some of the pitfalls, we went through the physiology of bowel preparation. And hopefully, you've understood that when you start a program with bowel preparation that you try and consult with the family physicians. But more importantly, consult with the
guest entrologist who may send you patients after incomplete colonoscopies, or may have different colon kinds/g in the preparation instructions on the patients so that you don't have any trouble preparing the patient. Or they may not be in trouble looking at the colon after CT colonography when the patient has barium in
the colon. Thank you very much. [BLANK_AUDIO]
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