Sonographic Evaluation of Right Lower Quadrant Non-Gynecologic Pain - HD

Introduction

My name is Dr. Caitlin McGregor. I'm from the University of Toronto and Sunnybrook Health Sciences Center where I'm an abdominal imager.

Today I'm gonna be talking about ultrasound of non gynecologic right lower quadrant pain, the ACR appropriateness criteria for acute pelvic pain. State that transvaginal ultrasound should be used as the initial test in reproductive age women when obstructive or gynecologic disease is suspected.

However, it's important to recognize that clinical diagnosis is a challenge and that there is considerable overlap between gynecologic and gastrointestinal disease.

Whenever I complete a transvaginal ultrasound and a female who has been referred for gynecologic disease and I find normal uterus and ovaries, the next step I always perform is a systematic search of the bowel.

In this talk, we'll be discussing the ultrasound appearances of appendicitis, diverticulitis, ileitis and colitis. Essentially this talk is about ultrasound of the gut.

Traditionally, the role of ultrasound in the evaluation of bowel has been underappreciated and underutilized. People fear that bowel gas will hinder evaluation. However, in most diseased bowel there is decreased peristalsis and decreased air and both of these things will considerably aid in visualization on ultrasound.

In addition, ultrasound is the only modality to resolve all five of the bowel wall layers. In addition, careful analysis of the wall layers as they're depicted on ultrasound and of the surrounding structures can give very important clues and allow us to arrive at a specific diagnosis.

Bowel Wall Layers on Ultrasound

So we will begin by discussing the bowel wall layers and how they're visualized on ultrasound beginning at the center, the first layer is in fact the interface between the echogenic mucosa and the lumen of the bowel, and this is seen as the innermost echogenic line moving outwards.

The next layer is the muscularis mucosa, which is hypoechoic and depicted here. The next layer is often the most pronounced on ultrasound, and this is the echogenic submucosal layer and followed finally by the outer hypoechoic layer, which is the muscularis externa or muscularis propria.

Finally, the fifth bowel wall layer is the serosa, which is a very thin echogenic line, and this line often blends into the adjacent surrounding fat so that it is not well visualized on ultrasound.

I'd like to draw your attention to these images of the rectum on MRI we are able to resolve two layers of the bowel wall. We see the hypoechoic muscularis externa on T two weighted imaging and internal to that the isointense muscularis or sorry submucosal layer.

I'd like you now to look at the rectum on CT where really we are not resolving any of the bowel wall layers. And this is in contrast to ultrasound, which can produce exquisite images again resolving all five of the bowel wall layers.

Normal Bowel Appearance

The appearance of ultrasound of the bowel when it is normal is that it's compressible and peristalsing. It has a layered appearance and the wall is thin measuring less than four millimeters.

The compressibility and peristalsis are two features which are well evaluated on ultrasound but are not well evaluated in either CT or MRI.

And this is a normal appearance of the terminal ileum where we see a very thin bowel wall layer with preservation of stratification.

And this is in contrast to this picture of the colon. In a patient with pseudomembranous colitis which demonstrates marked bowel wall thickening, particularly the echogenic submucosal layer in the abnormal situation on ultrasound, the bowel is focally or diffusely thickened.

In the abnormal situation, the layers can be preserved or completely lost and we will be discussing that more later. The thickening can be circumferential or eccentric. We need to evaluate the distribution of the abnormality. Is this segmental over a short or long segment? Is it multifocal And also doppler can be useful.

Scanning Technique

The technique for scanning the bowel can be labor intensive and somewhat time consuming To begin with, I always start with the curvilinear probe in order to get an overall picture of the bowel, a more global view of the abdomen and pelvis, but often multiple probes will be required and in addition, multiple linear probes including as high as the 12 megahertz linear probe, which can produce exquisite images of the bowel.

In addition, multiple patient positions are also required in an effort to move bowel gas out of the way or to move bowel wall segments into the field of view. Multiple approaches may also be required.

Transvaginal imaging can produce beautiful pictures of the rectum, sigmoid and pelvic small bowel. The anal canal and sphincter complex can be assessed with either a transvaginal approach or a transperineal approach. And of course transabdominal scanning will be required for the remainder of the bowel.

The graded compression technique that we are all familiar with in the setting of appendicitis is also used throughout the bowel and often we have bowel presets on our machines. Most often these presets will include compound imaging harmonics and multiple focal zones.

Appendicitis

So let's begin with appendicitis, which is the most common cause of right lower quadrant pain.

This recent meta-analysis looking at the performance of ultrasound versus CT scan demonstrated a sensitivity of 78% and a specificity of 83% for ultrasound in comparison to 91% and 90% for ct. So ultrasound performs very well, perhaps not quite as well as CT scan, but is still an excellent modality.

Evaluating the Appendix

In order to evaluate the appendix, one of the biggest criticisms of ultrasound in the setting of appendicitis has been non visualization of the appendix. The rate of visualization of the normal appendix on ultrasound is varied in the literature and ranges from as low as two to three percent to a high of 82%. And this is in a paper from France in 1992.

In my own experience, the more you work at it, the more you are able to find the normal appendix and I certainly hope that we achieve this more often than 4%. I'm not sure that we're reaching a rate of 82%.

So let's just review the techniques for visualization of the appendix. The graded compression technique was first described in 1986 and I think we're all familiar with that starting in the right upper quadrant at the edge of the liver and moving down the right colon in order to identify the terminal ileum and cecum.

Additional maneuvers can also be used including posterior manual compression in which the second hand of the ultrasound operator is placed underneath the patient and the appendix is compressed between the transducer and the posterior hand. And this will aid in compressing the structure of interest between the anterior abdominal wall and the psoas muscle posteriorly. And in this case the appendix.

The low frequency convex transducer is of great use because it will offer a greater field of view and a more global picture of the appendix and the surrounding structures. It can be very useful in larger patients.

Upward graded compression is a technique that can be used in an effort to displace the appendix out of the pelvis. This is most often used in male patients. The pelvic appendix in a female patient should always be evaluated with a transvaginal examination.

The left lateral oblique position of the patient I think is mandatory in all patients in whom the appendix is not seen in the supine position. And this will hopefully displace the cecum out of the way so that a retrocecal appendix will come into view.

Identifying and Assessing the Appendix

So how do we evaluate for appendicitis? The first thing we need to do is find the appendix and ensure that we are in fact scanning the appendix and not another loop of bowel. And in order to do this, we must demonstrate that we are finding a blind ending structure which is arising from the base of the cecum and this will prevent pitfalls such as a Meckel's diverticulum arising from small bowel.

In addition, we must demonstrate that it is tubular with gut signature. The gut signature will help us to differentiate between other pitfalls including dilated fallopian tubes, dilated ureters and vessels.

In order to correctly identify the appendix on ultrasound, we must understand the anatomy of the right lower quadrant and in particular the relationship of the ileocecal valve to the origin of the appendix. This relationship is constant regardless of the position of the cecum within the abdomen.

The ileocecal valve is characterized by this classic fish mouth appearance and if we travel posterior, medial and inferior along the axis of the cecum, we will come to the origin of the appendix.

And here's a patient with appendicitis. We used the graded compression technique beginning in the right upper quadrant. We traveled down the right colon until we found the ileocecal valve and here it is seen as a beautiful invagination into the lumen of the cecum with a classic fish mouth appearance.

By identifying this anatomic landmark, we are now sure that we are not only imaging the cecum but that we are imaging the terminal ileum. We will not mistake the appendix for the terminal ileum or vice versa.

Once we identify the ileocecal valve, we move posterior medial and inferior along the cecum until we come to the origin of the appendix, which we see here lacks that valve much different appearance than the origin of the terminal ileum.

Once we're at the base of the appendix, we travel along its entire length to ensure that we are ending with a blind ending structure. And by obeying all of these rules and being rigorous about applying them, we will correctly identify the appendix and not misidentify another loop of bowel as the appendix.

So once we have identified the appendix, the next task is to decide if the appendix is normal or abnormal. In the abnormal situation, the appendix should be aperistaltic, non-compressible and measure more than six millimeters.

An ovoid transverse shape in the cross section over the entire length of the appendix will reliably exclude acute appendicitis. In addition, if we can demonstrate that the appendix measures less than six millimeters under compression throughout its length, this is the most accurate finding with a very high negative predictive value.

What this means is that the six millimeter rule is far more useful in excluding appendicitis than it is in ruling it in. And we will be revisiting this thought in a moment.

This is an ultrasound of a normal appendix. We see the origin of the appendix here lacking the ileocecal valve. We follow it along. It's clearly a blind ending tubular structure with gut signature. So we know that this is the appendix.

It measures less than six millimeters under direct compression and it's ovoid throughout its length. So we have reliably excluded appendicitis.

In contrast to this patient here we have the tip of the cecum. We have on a separate image identified the ileocecal valve, the origin of the appendix lacking that classic valve structure. The proximal appendix is normal, however, the mid in distal appendix measures more than six millimeters in this case nine millimeters.

And if we were to scan this appendix in cross section, it would be completely round.

The presence of an appendicolith is not that useful. You can have appendicitis with an appendicolith or without. In addition, they can be very subtle on ultrasound and are much more readily identified on ct.

However, the presence of inflamed fat on ultrasound is an extremely useful sign. It helps us to localize the site of inflammation and key in on what the underlying cause is. It has a classic appearance being echogenic mass-like non-compressible. It may have increased doppler vascularity.

And here's a patient with appendicitis with typical surrounding inflammatory fat. In contrast to this patient with a normal appendix in which the periappendiceal fat is normal.

It's important to note however that the presence of inflamed fat helps us to rule in appendicitis. However, it does not need to be present. That means that in early appendicitis the periappendiceal structures may be normal and we need to rely on the findings within the appendix itself.

Here's another patient with pelvic appendicitis. On a transvaginal examination, as I've stated before, every female patient in whom the appendix is not seen from a transabdominal approach must have a transvaginal examination.

We see beautiful inflamed echogenic fat. This tells us where the problem is and that this is an inflammatory condition. It's echogenic mass-like non-compressible. It's very tender to probe pressure and when we look very carefully in this location, we find embedded in the fat a very rounded structure.

In contrast to the ovoid appendix I showed you before measuring more than six millimeters and this is pelvic appendicitis.

Finally, the presence of doppler flow is supportive evidence of inflammation or appendicitis. And this is true for any other loop of bowel in the abdomen or pelvis. This is a specific finding, meaning the presence of doppler vascularity, which is traceable in the appendiceal wall rules in appendicitis.

The converse of this however, is that absent flow does not rule out appendicitis.

Now I'd like to show you this case of the cecum in a patient with appendicitis. And I think if you really carefully look at the bowel wall layers and critically analyze them, you can appreciate that the anterior wall of this cecum is much different than the posterior wall.

There's far more thickening posteriorly than there is anteriorly. In addition, when you carefully analyze each layer independently, I think you will agree that the inflammation here is centered on the outer layers rather than the inner layers.

And if we compare this muscularis externa to the very thin one anteriorly, there is clearly a difference. This is a classic pattern of what we call reactive inflammation or secondary inflammation, meaning that the inflammation is secondary to an adjacent inflammatory process. In this case appendicitis.

Here is the CT correlate in the same patient we see a beautiful normal contralateral wall and on this side of the cecum we see focal thickening that is on the side of the inflamed appendix.

This is much different than this patient that has Campylobacter colitis in the right colon. So her cecum is inflamed because of infection, not because of appendicitis. And now the pattern of bowel wall thickening is much different.

The thickening is circumferential involving all walls equally and the thickening is centered more on the inner layers than the outer layers. The outer hypoechoic muscularis externa is relatively thin compared to the marked thickening of the echogenic submucosal layer.

In addition, it's not only on the side of the appendix which is over here and normal.

Excluding and Ruling In Appendicitis

So to summarize, the features that we use to exclude appendicitis on ultrasound are an appendix that measures less than six millimeters under direct compression. It's completely compressible throughout its length. It's ovoid in cross-section throughout its length and there are no periappendiceal inflammatory changes.

The pitfall to this, although a relatively rare situation is when the perforated appendix completely deflates and can measure less than six millimeters. However, the marked periappendiceal changes in these cases should avoid confusion.

How about ruling in appendicitis? Well, here we would like to see the wall thickening of the appendix i.e. single wall measuring greater than three millimeters. We would like to see that those individual layers are thickened.

We should evaluate the content of the appendix. A fluid-filled appendix is more concerning than one that is filled with debris. It should be non-compressible. Doppler flow is supportive evidence helping us to rule it in look at each individual layer and make sure that they are regular.

In the case of appendicitis, you may see focal irregularities of the submucosal layer look for periappendiceal changes including inflammatory fat, focal fluid or focal collections and evaluate for focal tenderness, ensuring that the patient's point of maximum tenderness is in fact over the appendix.

Pitfalls in Appendicitis Diagnosis

So when will we run into trouble on ultrasound with appendicitis? False negative ultrasounds meaning we miss appendicitis, usually occurs in unusual positions of the appendices, including most commonly retrocecal or pelvic appendices.

I think we've discussed both of these and ways to avoid these, in the case of the retrocecal appendix, we must do the left lateral decubitus position for the patient or scan in the coronal plane. And for pelvic appendices in females, all patients in whom the appendix is not seen from above, they must receive a transvaginal examination.

And this is such a case, this is a supine patient. We see some mildly enlarged nodes in the mesentery, but essentially it was a negative scan. The cecum is seen here and it is completely obscuring the retrocecal location because of the bowel gas within the cecum, the appendix was not seen.

However, when you turn this patient into the left lateral decubitus position, suddenly the abnormal appendix becomes uncovered. And here we have a dilated non-compressible thick walled appendix with surrounding inflammatory fat.

And this would be missed if the left lateral decubitus position or not used.

Well what about false positives on ultrasound? This typically arises in two different situations. And the first is mistaking the terminal ileum for the appendix. And because it is a bigger structure, the terminal ileum in the normal state can mimic an abnormal appendix.

And we have discussed how to avoid this by rigorously applying the anatomic rules that we discussed before in terms of identifying the ileocecal valve first and then traveling to the appendix.

The second situation mistaking a normal appendix for abnormal I'm going to discuss next. Typically this is an appendix that measures more than six millimeters and is non-compressible throughout.

However, this is a normal appendix and that is because it is filled with inspissated debris that is distending the lumen of the appendix and causing it to be non-compressible.

And here is such a case. On this side of the screen we have an appendix that measures more than six millimeters. It's completely incompressible, it measures just above six millimeters and it's rounded in cross-section.

You'll notice that the periappendiceal fat is normal. Now if you look very carefully at the appendiceal wall in this case, you'll notice how thin it is and how beautifully preserved the bowel wall layers are.

And that's in contrast to this abnormal appendix where you can clearly appreciate that the individual walls of this appendix are thickened and particularly the submucosal layer. In addition, this appendix has periappendiceal changes that help us rule it in another appendix to compare.

This appendix has complete loss of the bowel wall layers, which is in contrast to our normal appendix here, which demonstrates preservation. This is transmural inflammation and gangrenous appendicitis.

In addition, this is a fluid filled appendix which is clearly different than the content we have in our normal false positive appendix. So that fluid-filled appendix is measuring more than six millimeters are far more worrisome.

And finally, another abnormal appendix for comparison. Again, fluid-filled, much more concerning. We do have a liftoff in the lumen which doesn't help us out too much.

However, when you look at the individual walls, they are thickened more so than our normal appendix. And in addition, the submucosal layer, when you really look at it carefully and analyze it carefully, you'll see multifocal irregularities of the submucosal layer that is very concerning for appendicitis.

Now the other thing for this patient, six millimeters measuring a little bit more than six millimeters noncompressive and rounded in cross-section that in fact we found another cause for her right lower quadrant pain, which makes us even more confident that this is a false positive.

On ultrasound, she had a right lower quadrant ovarian hemorrhagic cyst and when we probed with the probe, although she was somewhat tender here, she was exquisitely tender over her hemorrhagic cyst.

Terminal Ileum and Ileitis

We'll move on now to the terminal ileum, which is the most common gastrointestinal cause of misdiagnosis of appendicitis clinically so that we can expect to make this diagnosis on ultrasound. In patients who are referred for right lower quadrant pain, terminal ileitis is caused by infectious agents, particularly yersinia, campylobacter and e coli.

It's characterized by enlarged mesenteric nodes in the adjacent fat by an abnormal and thickened terminal ileum, which will often demonstrate increased doppler flow.

Differentiating Abnormal Terminal Ileum from Appendix

Now how do we differentiate the abnormal terminal ileum from the abnormal appendix? Well, we've discussed this earlier in reference to the appendix and that is the best way to do it by applying the anatomic rules.

However, there are some additional ways in which we can reassure ourselves that we are in fact dealing with an abnormal terminal ileum and not the appendix, the abnormal terminal ileum, even when thickened will maintain a somewhat ovoid cross-section.

And that's in contrast to the rounded appendices that I've showed you that have been abnormal. When abnormal, the terminal ileum will still maintain some degree of compressibility. It may not be completely compressible but it will be slightly deformable to probe pressure.

The diameter of the abnormal ileum is larger than the abnormal appendix. It's not a blind ending structure. We must use the ileocecal valve to ensure that we're scanning the terminal ileum even when it's abnormal.

There will almost always be some preservation of peristalsis, even if markedly diminished, the amount of air will be decreased but there will be some air present and that is unlike appendicitis, which usually does not contain air and the tenderness of terminal ileitis tends to be more diffuse than appendicitis.

This is a patient with yersinia. The first thing that we recognized was abnormally enlarged nodes and they were more numerous than we would've expected in the mesenteric fat.

Once we identified the terminal ileum, it was easy to appreciate that the wall was thickened. This single wall thickness is more than four millimeters in this case seven millimeters.

I want you to appreciate that the bowel wall stratification is completely preserved and this is a sign that allows us to confidently exclude a malignant cause for this bowel wall thickening In cross-section.

This abnormal terminal ileum is ovoid in contrast to the abnormal appendices that I showed you earlier. And when we apply doppler, there is increased flow within the wall which supports the diagnosis of inflammation and this patient grew yersinia on culture.

Patterns of Thickening and Ancillary Features

Now whenever I find the abnormal bowel wall thickening, I always keep in mind whether the bowel wall thickening has an intrinsic or an extrinsic pattern. And I just would like to remind you once again about the cecum I showed you earlier with the typical reactive thickening or secondary thickening to appendicitis.

And contrast it to this patient with intrinsic thickening in which we have circumferential thickening centered more on the inner than the outer layers.

Whenever I find a thickened terminal ileum, particularly when the bowel wall layers are intact, the next thing I always do is look for ancillary features of Crohn's disease to see if I can come up with a more specific diagnosis.

Terminal ileum thickening on its own is a relatively non-specific finding. The most common cause is, as we said, infectious terminal ileitis. Other causes, such as hemorrhage, vasculitis et cetera can also be possible.

If we find these ancillary findings of Crohn's disease, we can arrive at a more specific diagnosis. And in particular the things I look for are fistulas and intramural linear transmural ulcers.

So here's a patient that presented to the emergency department with right lower quadrant pain. The terminal ileum was correctly identified by the presence of the valve. The appendix was clearly normal but the terminal ileum was markedly thickened.

There was echogenic fat, there was increased doppler flow in the terminal ileum supporting inflammation. In addition, the bowel wall layers were preserved, ruling out malignancy.

When we looked closer, however, we were able to demonstrate a linear hypoechoic tract extending from the abnormal terminal ileum towards the retroperitoneum and psoas muscle consistent with a fistula, a relatively specific finding for Crohn's disease.

You will not see these fistulas unless you look for them specifically. They can be quite easy to overlook and in addition, they often require opening up the field of view with the curvilinear probe because they can be quite deep structures and they can be missed if you stick to scanning with only the linear probe.

Another patient with right lower quadrant pain and terminal ileal thickening preservation of bowel wall layers and again a hypoechoic tract with doppler flow consistent with inflammation of the tract.

These fistulas tracts can blind end in the mesentery. They can communicate with the skin, they can communicate with other loops of bowel or they can communicate with the retroperitoneum. And when you see these tracts, the next thing you should do is rule out the presence of associated abscess as they can lead to mesenteric abscesses.

This is another patient with Crohn's disease that beautifully demonstrates the transmural linear ulcerations that these patients can have. And this is again, another relatively specific finding for Crohn's disease and will help you to narrow your differential in the cases of terminal ileitis.

Before we leave the terminal ileum, I would just like to show you these two cases which look relatively similar. On this side we have a patient with Crohn's disease and on this side we have a patient with lymphoma.

Crohn's disease is one of the inflammatory conditions of the bowel that can be a transmural process. It leads to fibrosis and it can over time lead to complete loss of stratification of the bowel so that loss of stratification of the bowel can be inflammatory or malignant in etiology, whereas preservation of bowel wall stratification is specific for a benign process.

And this is just to contrast with our initial patient who had yersinia terminal ileitis where those bowel wall layers were so beautifully preserved, the hypoechoic muscularis mucosa, the echogenic submucosa and the hypoechoic muscularis externa.

Diverticulitis

We're gonna move on now to diverticulitis. In general, diverticulitis is a causes left lower quadrant pain, which is not the title of this talk. However, there are certain situations in which this disease can cause right-sided pain.

The first one is when the sigmoid colon is redundant and extends over into the right pelvis so that these patients can present with sigmoid diverticulitis causing right-sided pain.

The ultrasound features of diverticulitis are bowel wall thickening with preservation of the bowel wall layers and particularly it's the outer muscular layer, the muscularis externa that is thickened, which helps us to differentiate it from some other processes that involve the colon.

In addition, we must find the offending or inflamed diverticulum and we would like to find that diverticulum at the epicenter of maximum wall thickening and maximum inflammation, which is nicely demonstrated in this schematic.

The diverticulum is embedded in the site of maximum wall thickening and inflammation. Once we've diagnosed diverticulitis, we must continue and look for the complications particularly abscess fistula and perforation.

Diverticulitis in Pelvic Pain

Now the second scenario in which knowing the ultrasound appearance of left-sided sigmoid diverticulitis is extremely important is in women who come in with vague pelvic pain. This may be right-sided or left-sided.

However, these are women that are referred to rule out gynecologic disease and I'm amazed at how many times these women have normal uterus and ovaries and what they actually have is subclinical or not appreciated diverticulitis.

And so as I've said before, when a patient is referred for gynecologic disease and the uterus and ovaries are normal, the next step should always be on ultrasound to evaluate the bowel.

And here we have a beautiful picture of the sigmoid colon on a transverse scan. I'll draw your attention to the outer muscular layer, which is more thickened than normal, a good sign for diverticular disease.

We find the diverticulum at the epicenter of maximum wall thickening and maximum inflammatory fat embedded in this echogenic mass-like non-compressible fat. And this is the location of the patient's maximum tenderness.

The other thing I'd like to draw your attention here to is the fact that often the bowel wall layers at the neck of the diverticulum are disrupted and that is not a worrisome finding.

The pitfalls in terms of diverticulitis on ultrasound are missing small abscesses, particularly when they're air-filled or when they're interloop in location. So we must be extremely vigilant about these patients when we're scanning them on ultrasound. Keeping in mind that this may be one of the pitfalls.

In addition, the other thing we must always keep in mind when scanning patients with diverticular disease is, are we missing an underlying malignancy and how do we tell the difference between these two?

Well, diverticulitis generally is a left-sided disease and really we must find the inflamed diverticulum, like I mentioned at the epicenter of inflammation before. We are confidently calling diverticulitis.

The perigut findings are helpful. Inflamed fat fluid collections, et cetera are more likely due to diverticulitis. The caveat to that of course is a perforated malignancy.

Malignancy on the other hand has greater wall thickness. It's often asymmetrically involved. So even circumferential tumors will often cause thickening more so on one side of the bowel than the other. And the bowel wall layers are lost.

And this is a point that I've emphasized before that when the bowel wall layers are lost, the possibility of malignancy needs to go through our minds.

In general, colon cancer will have absence of perigut findings and the involvement will be over a relatively short segment, usually less than five centimeters.

And here's a classic right-sided adenocarcinoma on ultrasound. We see that there is certainly bowel wall thickening the bowel wall stratification is completely lost. Although this side of the bowel is certainly abnormal, it is very eccentric being much more thickened On this side there is vascularity, there's no perigut findings and this is classic for adenocarcinoma

and that's in contrast to this patient with right-sided pseudomembranous colitis in which the bowel wall layers are preserved, allowing us to confidently exclude a diagnosis of malignancy.

Right-Sided Diverticulitis

Now the second situation in which diverticular disease can cause, right, so right lower quadrant pain is right-sided diverticulitis. So diverticulitis involving the right colon and cecum, this is usually considered a separate entity.

These diverticula are felt to be congenital in nature and they are true diverticula, meaning that they contain all of the bowel wall layers. And this probably explains why right-sided diverticulitis often has far fewer complications than left-sided disease, meaning less abscesses, less fistulas and less perforation.

These are younger patients usually in their forties. It's very common in the Asian population. And a key point here is that this is a conservatively managed disease.

Another very important point to stress is that right-sided diverticulitis clinically presents identically to appendicitis and therefore it is up to us as radiologists or ultrasonographers to make this diagnosis on ultrasound.

In addition, if these patients erroneously go to the operating room with a diagnosis of appendicitis, the surgeon's impression at the OR is often that of a mass and the inflammation is usually so severe that the diverticulum is obscured.

And so these patients go on to have an oncologic operation, namely a right hemicolectomy for what is otherwise a conservatively treated disease. So this really is the domain of radiology.

We must make this diagnosis because it's very difficult to make clinically and surgically even in the operating room. It is a very difficult diagnosis. We must demonstrate a normal appendix and a normal terminal ileum.

So what are the features? They're the same as left-sided disease. We wanna demonstrate that the bowel wall layers are preserved and we wanna identify the inflamed diverticulum at the level of maximum wall thickening and inflammation.

And again, just to emphasize this point, in these cases we must demonstrate a normal appendix.

Here's a patient who presented with right lower quadrant pain to emergency. We have segmental thickening of the right colon. There is some mild peri colic inflammatory change, but this is a relatively non-specific appearance.

When we take this patient to ultrasound, however it becomes much more clear. We identified the diverticulum as an outpouching extending beyond the confines of the bowel wall. It's embedded in inflammatory fat.

This is right-sided diverticulitis that was much more apparent on ultrasound than it was on ct. The diverticulum in retrospect is embedded in this inflammation and very difficult to appreciate.

In addition on ultrasound, we were able to demonstrate that the bowel wall layers of this right colon not well demonstrated on this picture, were entirely preserved, excluding a malignancy.

So two more patients who also presented with right lower quadrant pain and I think have a relatively similar CT appearance in that they have relatively short segment focal thickening of the right colon.

This upper quadrant patient here, with normal peri colic fat, this patient may be with some mild peri colic fluid and inflammation.

When we take this first patient to ultrasound, we see that the lesion corresponds to marked asymmetric thickening of the right colon, which with complete loss of bowel wall layers. We have no perigut inflammatory changes. We have no diverticulum and this is a classic appearance of an adenocarcinoma.

Take the second patient to ultrasound and the appearance is much, much different now the bowel wall layers are completely preserved. We have a beautiful external muscular layer, a beautiful submucosa and a muscularis mucosa. And this excludes now a diagnosis of malignancy.

And in addition, we're able to demonstrate the diverticulum at the epicenter of maximum wall thickening and inflammatory change.

Colitis

Finally, we're gonna discuss colitis in general on ultrasound. The appearance of the various etiologies of the colon are similar, ulcerative colitis, ischemic colitis, infectious colitis, et cetera.

However, there are few features that can help us in arriving at a relatively specific diagnosis. And the first of these is pseudomembranous colitis.

This colitis is heralded by striking bowel wall thickening, which is centered on the submucosal layer. There's gross submucosal edema. So this echogenic layer is markedly thickened. It's thrown up into a gyral or folding pattern, which is the ultrasound equivalent of the thumb printing that we so often see on plain film.

In addition, that outer hypoechoic muscular layer is often extremely narrow in contrast to patients with diverticular disease. The lumen will often be effaced in these patients. They may have ascites, but otherwise the pericolic inflammatory change is relatively minimal. Despite the quite marked bowel wall thickening.

This disease does not have to be pancolitis. It can certainly be segmental and it can certainly be confined to the right colon.

And here's a classic appearance of pseudomembranous colitis. Again, this thick gyral pattern of the echogenic submucosal layer, which is circumferential and an intrinsic pattern to this loop of bowel.

It's folded up it's thumbprint in the longitudinal plane. You really appreciate how thickened that submucosal layer is. But you also appreciate how very thin the external muscularis externa layer is in contrast to diverticulitis in which due to muscular hypertrophy, the muscularis externa becomes quite thickened.

In addition, despite this marked bowel wall thickening, you can appreciate how relatively minimal the pericolonic inflammatory changes are.

Ischemic Colitis

Now the second, colitis that sometimes we can suggest on ultrasound is ischemic colitis. Usually these are in elderly patients. They have symmetric bowel wall thickening. It's involves usually the inner layers more than the outer layers.

It's usually over a long segment in contrast to malignancy. Greater than 10 centimeters can be seen on the left side but also on the right side. And the hallmark feature really is barely visible or absent doppler flow and in particular absent arterial signal.

Now I'm not by any means suggesting that ultrasound is the modality of choice for diagnosing ischemic bowel that really is ct. However, there are two scenarios which arise in which is very useful to have this diagnosis in your back pocket on ultrasound.

And this is the first scenario, these are the patients that, are in hospital. They often have elevated creatinine so that the referring clinician does not want to order a CT scan. Their abdominal pain is nondescript. They really don't have a clinical suspicion of any particular entity and their lactate is normal.

And this was an elderly man post total knee replacement. When we came to ultrasound, he was able to localize his pain for us and we recognized that his right colon was extremely thickened. In addition, when we put doppler on despite the marked bowel wall thickening, we were unable to obtain any doppler flow despite maximizing our flow for sensitivity.

So we were able to suggest the diagnosis of ischemia. We weren't obviously, completely confident in ultrasound and I'm not suggesting that we would be however we were suspicious enough to send this patient to a CT scan to optimize his creatinine and to give him contrast.

And he did indeed have right-sided ischemic colitis and was sent to the operating room. And this was path proven.

The second scenario in which ischemic colitis sometimes arises on ultrasound is far less common. However, I think it also, demonstrates the usefulness of ultrasound of the bowel.

This is an elderly patient again, who is unable to receive contrast because of an elevated creatinine. And on the non-contrast study, we appreciated that the right colon was maybe a bit thickened. There was certainly pericolic inflammatory change and we were wondering if this was, pneumatosis or not. It was a little bit difficult.

So we thought well, we'll bring this patient to ultrasound and sure enough, on ultrasound we were able to confirm the presence of pneumatosis. Now pneumatosis is certainly not, an ultrasound diagnosis, but in addition to this, we were unable to get any arterial flow in this loop of bowel.

And so between these two studies, our suspicion of ischemia was increased and this patient did go to the operating room, for ischemic right-sided disease.

Summary

So in summary, ultrasound is sensitive and specific for the diagnosis of appendicitis and diverticulitis. Preservation of bowel wall layers virtually exclude the diagnosis of malignancy.

Inflamed fat is a very useful sign on ultrasound and we must look for it specifically. It allows us to localize the problem and find the underlying disease process.

And I hope that I've demonstrated that a careful analysis of the bowel wall layers can be extremely useful in arriving at a specific diagnosis. Thank you.