Acute Abdominal Pain in the Child: Ultrasound Versus CT - SD

Introduction

Hello, my name is Harriet Paul Thiel.

I am from Children's Hospital in Boston, and my topic today is acute abdominal pain in the child ultrasound versus ct.

In the next half hour, I plan to review the imaging evaluation of several common causes of acute abdominal pain in children with an emphasis on the relative roles of ultrasound and CT in the workup of each entity.

I have no commercial interest in the presented material, and I will not discuss investigational devices or pharmaceuticals.

As far as acute abdominal pain in the child is concerned, infectious gastroenteritis is the most common entity. This is often associated with fever, vomiting, and diarrhea, and generally improves rapidly with rehydration. Surgical conditions do not usually present in this manner.

Acute appendicitis is the most frequent indication for emergency abdominal surgery. The clinical diagnosis is often difficult, and many non-surgical conditions may mimic acute appendicitis. And I wanna emphasize that when surgery is contemplated, then imaging plays a key role.

So I plan to discuss the following entities with respect to their imaging evaluation, namely, acute appendicitis, which is the most common and important abdominal trauma, mesenteric adenitis inception, inflammatory bowel disease, and several genital urinary abnormalities including acute pyelonephritis, renal colic, and ovarian cyst, torsion and tumor.

Acute Appendicitis

Let's start first with acute appendicitis. This is generally diagnosed either with ultrasound or ct, and the question has certainly become a very critical one.

Does the greater diagnostic accuracy of CT warrant the associated exposure to ionizing radiation and the higher operating costs compared to ultrasound?

One must remember that children in particular are sensitive to the negative consequences of radiation exposure, and they have potentially a very long period during which radiation induced tumors may develop on the other hand, and so-called negative ultrasound examination does not exclude appendicitis unless the normal appendix is identified.

So here, for example, is an example of a normal appendix very readily visualized with ultrasound. So here on the left, we see a longitudinal view of the appendix. It's very thin, it doesn't contain any stone. There's no associated fluid or mass surrounding the appendix.

Here we see it in transverse section without compression. And then with compression, we see that it is compressible. So this is unequivocally a normal appendix.

Here again, another nice, very well visualized normal appendix. And as you can see in this final slide, CT also can readily identify a nice normal appendix seen here containing small amounts of air.

When the appendix is well visualized, we can also confidently make a diagnosis of acute appendicitis. As you see here, the appendix is well visualized. It contains fluid, it is swollen measuring more than six millimeters from outer to outer edge. We can see here on the left that it is hyperemic with power doppler, non-compressible. And in this particular case, it is associated with a small amount of fluid in the cul-de-sac posterior to the uterus.

Another unequivocal example of acute appendicitis diagnosed sono graphically. We see here where we can readily trace out the entire length of the appendix with a stone at the tip shown in this image with associated distal shadowing.

Here's an example of a perforated appendix. We can see the appendix with some irregular fluid surrounding the tip here. We see it in cross section, and in this last image, we see that there's some hyperemia as documented with color doppler and swollen bulbous termination of this appendix.

Even after perforation, the appendix can up to close to about half patients can still be visualized. Here we see it in cross-section, there's a little stone with distal shadowing, and you'll notice that there's a lot of surrounding inflammation. A lot of fat walled off mesentery very strikingly identified in these images. There's some focal ileus as well. There's mild dilation of the adjacent bowel loops and hyperemia.

Unfortunately, the ultrasound detection rates for acute appendicitis is very widely in the literature reported from anywhere from 22 to 98%, and there have been all kinds of attempts to try to improve the visualization with mixed results.

There have been suggestions of scanning through a full bladder scanning after a saline enema, posterior body wall compression or scanning in the posterolateral position in order to identify a retrocecal appendix.

There have been a number of studies performed. There was one published in a JR in 2000 by Pena, and colleagues from my institution that showed that the confidence of the radiologist in their interpretation of acute appendicitis is very much influenced by the choice of modality, and that radiologists are significantly more confident about their CT interpretations compared to their ultrasound interpretations, regardless of their training level.

So this was true for residents, fellows, and for faculty radiologists.

The bottom line is that an effective imaging protocol should probably include both ultrasound and ct. And certainly at my institution, we will perform an IV contrast in hand CT if the appendix is not visualized by ultrasound or the findings are inconclusive. If there is a high clinical concern for acute appendicitis.

It's also important to consider the body habitus of the patient when deciding whether or not to initially perform an ultrasound or to go straight to a CT scan. As I'm sure you're all aware, the visualization of the appendix is definitely decreased in obese patients, and this is certainly true for children as well as adults.

The ideal protocol is really going to vary from place to place and will be dependent on the particular resources and expertise that are available at a given institution.

So here's an example of a patient where ultrasound was not helpful. There were some secondary signs that certainly made us concerned that there might very well be an acute appendicitis. These are images of the right lower quadrant. Here's the bladder seen at the edge of the image, and then there's a lot of bowel gas in that right lower quadrant, so the appendix just could not be visualized.

However, there was some free fluid in the pelvis at the site of the patient's pain. So this patient did go on to have a CT scan, which unequivocally demonstrated abnormalities consistent with acute appendicitis.

So here we see a retrocecal appendix. It is thick walled. There's some enhancement of its wall. There's a little bit of stranding of the surrounding fat. And here we actually see that there's more than one stone. There's several tiny stones there.

Here's another patient where the appendix could not be definitively identified. This was a girl with pains, highly suggestive acute appendicitis. And here in the pelvis was this abnormal fluid collection butting the ovary. But the appendix was not definitively seen. There was some question as to whether this might possibly be the appendix, but it could never be really well demonstrated.

Here we see with power doppler that there's some increased flow at the edge of this fluid collection. Here we see the ovary adjacent to the fluid collection, but with CT we can very readily see that there is a very large pelvic abscess. And here is an abnormal appendix immediately adjacent to the abscess. So this is a perforated appendicitis.

Here we see some stones in that appendix. There's some air, so it's a localized perforation with abscess. And here we see a indentation on the bladder and displacement of adjacent bowel loops.

As far as outcomes are concerned, the best outcomes will require an ongoing collaboration between experienced clinicians performing the initial patient evaluation and their radiologists until an acceptable level of diagnostic certainty is reached.

Some people have suggested the implementation of a clinical scoring system with stratification of patients into low, intermediate, and high risk categories for the presence of appendicitis. And some approach perhaps along these lines may eventually lead to a more reason consumption of imaging resources and radiation dose reduction.

Abdominal Trauma

I'd like to move on now to a brief discussion of abdominal trauma, which is certainly the leading cause of morbidity and mortality in childhood.

CT is definitely the imaging method of choice after blunt trauma in the hemodynamically stable child, it permits accurate detection and quantification of injury to solid and hollow viscera and associated intra and extra peritoneal fluid. And blood ultrasound is used primarily to detect the presence of a hemoperitoneum.

However, the detection of hemoperitoneum has been shown to have a limited impact on management in children who are hemodynamically stable.

The limitations of ultrasound in the assessment of abdominal trauma include one, provides no diagnostic information regarding the bony pelvis or the lumbar spine. It certainly cannot diagnose hollow viscus injury with any great accuracy, and it misses a significant proportion of solid viscous injuries as well.

On the upside, ultrasound can be very helpful in assessing a hemodynamically unstable patient. It can be performed rapidly at the bedside prior to surgery and serves as a rapid non-invasive replacement for diagnostic peritoneal lavage.

So here is an example of a patient with trauma, a grade four renal injury. You see the large hematoma surrounding the kidney. And at this level you can see that there are extensive lacerations and hematoma, and there's also a splenic contusion and ultrasound would really not be appropriate for the evaluation of this type of injury.

On the other hand here is a patient in the ICU who developed a precipitous fall in hematocrit shortly after liver transplantation associated with rapid abdominal distension. This patient was not in any position to move out of the ICU, and ultrasound was very helpful in demonstrating large collections of blood within the abdomen.

So here we have some views of the liver transverse of the liver. We see that there's some fluid in the chest and also at the tip of the liver. Here's a sagittal view of the right kidney, and we see that there is a collection, an abnormal collection of material in Morrison's pouch between the liver and the upper pole of the kidney, and here on the left side as well, a very large abnormal heterogeneous collection of blood as it turned out.

And here's a sagal view of that left kidney again with a large flu collection anterior to it, and this turned out to be an arterial leak at the level of the hepatic artery anastomosis.

Mesenteric Adenitis

I'd like to move on now to a discussion of mesenteric adenitis, which is an inflammatory condition involving lymph nodes. It can have symptoms that are very similar to acute appendicitis, including abdominal pain, fever and elevation of the white blood cell count.

And it's certainly the most common diagnosis in children who are taken to surgery and found to have a normal appendix. It may be primary or secondary.

Primary mesenteric adenitis is lymphadenopathy without an identifiable, acute inflammatory process or associated with mild mine thickening of the terminal ileum where the thickness is less than five millimeters, and most of these cases are believed to be due to an underlying infectious terminal ileitis.

Enlarged mesenteric nodes are also often identified in association with inflammatory conditions, including appendicitis, Crohn's disease, and celiac disease. And oftentimes these conditions are only diagnosed with CT primary mesenteric.

Adenitis is more common in children than in adults, and ultrasound or CT will depict a cluster of three or more enlarged mesenteric nodes greater than or equal to five millimeters in short axis diameter.

The role of imaging in this entity is really to exclude an associated inflammatory process.

So this is a young boy who had an ultrasound examination because of a clinical concern for appendicitis. The appendix was not identified, but in the right lower quadrant, a note was made of multiple mildly enlarged lymph nodes. As you can see on these two images, the patient did go on to have a CT scan, and the CT shows that there is a normal appendix that you can identify here containing barium.

So here the CT was necessary because the appendix could not be visualized by ultrasound.

Here's another patient also question of acute appendicitis. Again, multiple enlarged lymph nodes are identified sono graphically with color, we see that they are hyperemic. And there's also mild thickening of the distal ileum. As you can see here, the wall is a little thickened. Here we see some loops in sagittal, the section also mildly thickened walls that turned out to be a gastroenteritis.

Intussusception

I'd now like to discuss inception. This, as you know, is a prolapse of one bowel segment, the so-called inus septum into a more coddle segment. The incipients it is most common in the first two years of life, and there is a temporal relationship of intussusception with respiratory infections and gastroenteritis.

The vast majority of intussusceptions occur in the ileocolic region with a much smaller proportion being either ilio ioc, colic, colo colic, or ileal ial. And in the vast majority of these patients, there is no identifiable lead point.

Patients can present in a variety of ways. Classically they present with paroxysmal abdominal pain, a palpable abdominal mass. They may have current so-called current jelly stool. And here's an example of that due to ischemia of the mucosa with bleeding, and they may eventually develop bowel obstruction.

Imaging is generally achieved through the use of plain film. As you can see here. We can identify a mass. There's, if you look carefully, you can see that there's a little fatty density due to the invagination of the mesentery. In the intussusception, ultrasound and contrast enema, here's a typical appearance of an intussusception, a target appearance with multiple layers due to the inus septum and the out outer inus.

Here we see a sagittal view of it. Some people have called this a pseudo kidney sign. They've likened it, its appearance to a kidney. Here you can appreciate in a different patient the invagination of one or a telescoping of one portion of bowel into the other. And again, the swirling appearance of the various bowel layers and the vessels as where as well with color doppler.

And certainly in many places in the United States, probably the majority, air reduction is used and it's generally very successful. Here we see the intussusception outlined by air. We push the air through the rectum and push that into subception back where it belongs. And on this final image, you can see that there's free reflux of air into the distal small bowel.

A successful reduction, a lead point is more common in the very young or in the older patient. The idiopathic intussusception generally occurs from about six months of age to about four years. So younger than that, or older than that, there's usually a lead point, most commonly a melos diverticulum or a polyp or duplication cyst.

Lymphoma and hematoma can also act as lead points. There are less common, and certainly when there is a late lead point, an enema can still be attempted, but there is a much lower success rate in these particular patients.

Where a lead point is suspected, a CT is often very useful in delineating the underlying cause. And these patients are generally going to require surgical exploration because even if they are reduced, they will have a tendency to reins suscept. And obviously if a lead point is identified at the time that they present, then it is incumbent upon their treating physician to surgically explore them and remove that lead point though.

Here's a patient with a meles diverticulum, which I think you can see here. It's this very bright lesion here on a stalk. It's harder to see on the sagittal view. This really does look more like a kidney than that first case that I showed you.

And here is a patient, the patient had a barium re reduction. These are still done in some places. They're they are not certainly in our experience as efficacious as air, but some places people are still using contrast. And this is an older case, so we can see this mass that could not be reduced, and here it is at surgery. Here's the Melo diverticulum.

Here's another patient who was initially evaluated to rule out acute appendicitis, which he did not have. However, he did have a small bowel obstruction. And you can see on these views a very peculiar appearance of this bowel loop. It looks like there's a little mass invaginating into one loop invaginating into the other. This looks like a small bowel ieo ileal into subception, and this did turn out to be a mekel diverticulum.

Inflammatory Bowel Disease

Now like to move on to a discussion of inflammatory bowel disease. Crohn's disease and ulcerative colitis are the most common entities and neither disease usually presents primarily with acute abdominal pain in children plain films. Endoscopy and contrast, radiographic studies are the main imaging tools employed, and acute presentation is usually due to complications that may arise in the patients with chronic disease, including postoperative adhesions, abscess formation due to bowel perforation or fistula tracts.

In patients with Crohn's disease or in patients with ulcerative colitis, a toxic megacolon may develop. That being said, the diagnosis of inflammatory bowel disease may be less obvious in the very young child, especially during a first episode or presenting episode of abdominal pain.

IBD can involve the per appendiceal tissues, thereby mimicking acute appendicitis, both clinically and radiographically.

Ultrasound can be helpful in directly visualizing thickened bowel loops, abscesses and fistulas, although generally speaking, CT is probably better. Although Stephanie Wilson has certainly been a strong advocate for the use of ultrasound, and perhaps we will be doing more ultrasound, especially in children where we are trying to limit radiation exposure.

The affected bowel will have decreased peristalsis and loss of normal compressibility, and some have suggested that vessel density as assessed by color doppler may be inaccurate reflection of disease activity.

So here, I've listed the main imaging modalities that are used in the investigation of inflammatory bowel disease ultrasound, which can show mural thickening and adjacent inflammation. It can depict fibro fatty mesenteric proliferation in Crohn's disease.

However, the concern has always been that it may underestimate bowel involvement. Really takes a dedicated examiner and time to do a comprehensive examination of the abdomen looking for bowel involvement. And there is some controversy as to the correlation between color doppler features and clinical activity.

CT is used for imaging of complications such as abscesses when the ultrasound findings are equivocal and may be used to guide abscess drainage, particularly interloop abscesses that may be hard to visualize sono graphically.

An MR is also frequently used generally for the non-emergent assessment of disease.

So here is a young individual who came to ultrasound because of the new onset of abdominal pain and weight loss. This patient did not have a prior diagnosis of inflammatory bowel disease, however, multiple loops of bowel were noted to be very thickened and hyperemic. As you can appreciate here, there was some prominent mesenteric fat in association with these abnormal loops, and this did turn out to be Crohn's disease.

Here we see this patient's CT scan, very abnormal appearance of the terminal ileum, which is markedly thickened and irregular. We see it here in transverse section with a lot of walled off inflamed mesenteric fat.

And I also wanted to show you this image because you'll notice that the lymph nodes are also enlarged, and this is a so-called secondary mesenteric adenitis.

Here's a patient with known Crohn's disease who developed a flare and complained of severe per rectal pain. And you can see in these sonograms, which were performed with the patient prone. So this is the skin surface. There's gel, we see that there's very prominent inflammatory tissue immediately below the surface of the skin, extremely hyperemic with color doppler, and actually a fistula can be ident identified as well extending to the skin.

With flow through this fistula seen in real time, there is some hyperemia surrounding the tract with color doppler. And here we see a CT scan that shows the rectum with this fluid collection and extending directly into the wall of the rectum and portion of it extending out to the anus into the intergluteal cleft. As you can appreciate here.

Genitourinary Abnormalities

I'd now like to move on to a discussion of genital urinary abnormalities that may be associated with acute abdominal pain, namely poly nephritis, renal colic and ovarian cyst. Torsion and tumor acute poly nephritis frequently presents with fever, vomiting flank pain, and an elevated white blood cell count.

Right sided acute poly nephritis may mimic acute appendicitis and ultrasound has been shown to be an efficient, cost-effective method to assess the anatomy of the upper urinary tract compared to ct and certainly in our place we use ultrasound extensively in the workup of a first UTI in both girls and boys, and also in patients who subsequently develop UTIs with a palpable abdominal mass or in a UTI that is unresponsive to antibiotic therapy.

That being said, it's important to be aware that acutely infected kidneys are often normal sono graphically, and we generally reserve CT evaluation for the imaging of complications. So patients who don't respond to antibiotic therapy or develop other complications that require imaging evaluation.

Acute Pyelonephritis

Here's a patient who had an immune deficiency who presented with fever and abdominal pain. Interestingly did not come in complaining of flank pain. Here is here are a couple of images of that patient's left kidney, we see the kidney, and then there is a subcapsular fluid collection that is heterogeneous and echogenicity, a little bit of hyperemia.

With power doppler, you can see that the kidney is compressed by this collection on ct. We can see that there are multiple pockets of fluid. There is extension into the SOS muscle. There is an enhancing rim, and this was indeed a subcapsular abscess that was drained with ultrasound guidance. As you can see here.

Renal Colic

Stones occur with increased frequency in children who have urinary tract obstruction, which is due either to anatomical causes or neurogenic abnormalities. The stones are usually due to a combination of infection with either proteus or Klebsiella or underlying metabolic disease, which predisposes them to develop stones.

Acute presentation in children is relatively uncommon. Most of the time stones are discovered during the investigation of a non-specific abdominal pain or urinary tract infection, and both ultrasound and CT are used extensively for diagnosis of stones in children.

Ultrasound is generally the first line imaging tool, but CT can be very useful in patients in whom ultrasound is not helpful. And that's generally in obese patients, patients who have very severe scoliosis, which limits the quality of the examination or when patients have a negative renal ultrasound examination and yet a clinical suspicion for a stone remains high.

Non-contrast CT is increasingly being used for the primary diagnosis as opposed to ultrasound because it has a higher sensitivity for stone detection and also can demonstrate a number of secondary signs of obstruction, including perinephric or per ureteral fat fatty stranding edema of the ureteral wall dilation and blurring of the renal sinus fat.

Here's a couple of images of an 8-year-old boy with MRCP, mental retardation and cerebral palsy and scoliosis in whom renal stones were suspected. He had some pain. Ultrasound of the right kidney did not show a stone on the left side. There was some this echogenic focus in the lower pole with a mild degree of distal shadowing suspicious for stone.

The patient did go on to have CT and this showed did indeed show a stone in the lower pole, the kidney, but actually there were several stones that had not been seen with the ultrasound here tiny stones here in the upper pole and the lower pole. And in addition, there were a couple of tiny stones in the right kidney as well that could not be seen by ultrasound.

This is another example of a patient with a lower pole stone. We see an echogenic focus in the lower pole with distal shadowing, which is diagnostic with a stone. The twinkle sign is also very helpful. Here we see an artifact related to the interaction of the stone with the ultrasound beam, and that also increases the accuracy of our diagnosis of stones.

Ovarian Cyst, Torsion, and Tumor

Gynecologic conditions are frequent cause of right lower quadrant pain, including ovarian cyst and torsion. Pelvic inflammatory disease and ectopic pregnancy are also commonly associated with acute abdominal pain, but I'm not going to discuss them further in this lecture.

Ultrasound is the primary imaging modality, including both transabdominal and transvaginal scanning. When we are dealing with a sexually active patient, MRI or ct are employed in the imaging of complex cases also to determine the full extent of a tumor. And also in some cases for definitive diagnosis of teratoma, an ovarian scy may cause abdominal pain if it is significantly enlarged or if it's complicated by hemorrhage, rupture or torsion.

Uncomplicated cysts generally have a thin wall and koic contents by ultrasound and have a variable appearance after hemorrhage. The contents may be echogenic or hypoechoic. The cyst wall may be thin or thick and irregular, and there may be internal septations.

Treatment of ovarian cyst is generally conservative with follow-up recommended in order to exclude an underlying neoplasm.

Ovarian torsion is most common in adolescents and young adults, and it may occur in association with adnexal cysts or neoplasms. An underlying lesion more commonly occurs in the younger patients and is usually associated with the onset of acute lower abdominal pain, nausea, vomiting, and leukocytosis.

The ovary is markedly enlarged and generally has multiple enlarged peripheral follicles.

Here's a 4-year-old girl who developed the acute onset of right pelvic pain. We could not identify a normal right ovary. Here's a large mess with the peripherally associated little cysts, which are the enlarged follicles. Here's her uterus. This abnormal ovaries plastered up against it and there is a flow at the edge of this lesion, but not within the mass itself. In this patient with acute ovarian torsion.

Here's a newborn who presented with a large abdominal mass and tenderness to palpation. A transverse image of the pelvis shows a bladder almost empty. Here's a normal appearing left ovary. The right ovary could not, normal right ovary could not be seen. This is a sagal view of her uterus, which is quite prominent in the newborns due to more maternal hormonal stimulation.

And here was a huge cystic lesion in the right and neck. So that extended all the way up to the liver, as you can see on the sagittal view and with a fluid fluid level, just huge extending from the pelvis all the way up to the liver.

The patient was presumed to have an ovarian torsion. She was followed conservatively at five and a half months of age. The cyst had decreased in size. It's quite irregular. And there's this mural, calcific nodule with very intense distal shadowing and presumably the infarcted now calcified ovarian tissue.

I'll just say a few words about ovarian tumors. These can be benign or malignant. The benign tumors are more common about two thirds, and the vast majority of them are cystic teratomas. The other entity is cystadenoma.

Malignant tumors are less common. They may be primary either germ cells, stromal sex cord, or epithelial in origin or metastatic.

I'm going to limit my remarks to a discussion of cystic teratoma, which comprises more than 90% of all the benign ovarian neoplasms in the pediatric population with the vast majority occurring in the pubertal age group.

These can present either as an asymptomatic mass or maybe associated with acute abdominal or pelvic pain, which is generally due to hemorrhage associated torsion of the ovary or rupture of the tumor.

These tumors contain material elements from all three germ cell layers, and they are generally between five and 10 centimeters in diameter and contain less than 50% soft tissue elements.

The ultrasound features do depend on the relative amounts of various tumor components, namely fat, sebum, fluid, calcium and hair. They can have a wide variety of appearance. They may be koic solid or mixed. Calcification, neural nodules, the so-called tip of the iceberg sign. Fluid fluid levels, CT and mr. Are sometimes helpful for diagnosis.

If the sonographic findings are not definitive, they can readily detect fat and depict fat fat fluid levels and calcification.

Here's an a sonographic example of a cystic teratoma. We see the fluid and a mural nodule. This should not be confused with the bladder. And this patient did go on to have a CAT scan, which readily shows the presence of calcification in the wall, a fat fluid level, numerous septations.

Summary

So in summary, I have reviewed with you the imaging evaluation features of the most common causes of acute abdominal pain in children with an emphasis on the relative roles of ultrasound and CT in the workup of each entity.

I have discussed with you acute appendicitis, abdominal trauma, mesenteric adenitis inception, inflammatory bowel disease, and genital urinary abnormalities, including acute pollen nephritis, renal colic, and ovarian cyst, torsion and tumor.

Thank you for your attention.