Gastrointestinal (GI) symptoms, including vomiting, pain and diarrhea, are common reasons pediatric patients visit the emergency department. Because the clinical picture can be confusing in children, imaging often plays a key role in establishing a list of differential diagnoses. It is the responsibility of the radiologist to assist in defining the clinical picture and guide the physician to the most appropriate imaging modality. In this article, we address some of the more important pediatric GI pathologies that usually result in patients presenting to the emergency department, with a review of the typical clinical presentations and associated imaging findings. Entities discussed include foreign body ingestion, hypertrophic pyloric stenosis, malrotation and midgut volvulus, duodenal and pancreatic trauma, intussusception, appendicitis, mesenteric adenitis, Meckel diverticulum, and inflammatory bowel disease.
Foreign body ingestion is common in the pediatric population, with most cases occurring in patients ages 6 months to 3 years.1 Children present with nonspecific symptoms related to the GI or respiratory tract, such as vomiting, gagging, choking, throat pain, or foreign body sensation.2 Most foreign bodies (80% to 90%) pass spontaneously, but approximately 10% to 20% require endoscopic removal, and approximately 1% necessitate surgical removal.1
The first-line imaging study used in the evaluation for foreign body is the conventional radiograph, including frontal and lateral radiographs of the neck, chest and/or abdomen.3 The location, size, shape and number of foreign bodies should be noted in the radiology report, as this information will help the referring physician to make informed decisions about management. Common ingested radiopaque foreign bodies include coins, magnets and batteries. The lack of visualization of a radiopaque foreign body, however, does not exclude the diagnosis; in such cases with a high clinical suspicion or a witnessed ingestion, subspecialty consultation should be obtained.1,2
When evaluating for magnet ingestion, it is important to note the number of magnets, as well as their location within the GI tract.1 Magnets in different parts of the bowel may be attracted to each other, leading to bowel entrapment. Magnification of images or fluoroscopy may aid problem-solving. If the magnets are static on multiple images or demonstrate an intervening gap, the possibility of entrapment should be raised.1,3
A button battery is another radiopaque foreign body that can cause significant adverse effects. The double edge of the button battery or halo helps to distinguish this entity from a coin on the anteroposterior (AP) view (Figure 1).4 Ingested batteries may cause significant injury due to electrical discharge, necrosis due to pressure, and/or caustic injury from leakage. Complications of button battery ingestion include fistula formation, burns and perforations, which can be life-threatening and require immediate communication to the referring provider.1,3
Infantile hypertrophic pyloric stenosis is a relatively common condition characterized by abnormal thickening of the muscular layer of the pyloric channel secondary to hyperplasia and hypertrophy of the pyloric circular muscle fibers. This leads to failure of the pylorus to relax, which subsequently causes gastric outlet obstruction. Clinically, hypertrophic pyloric stenosis should be considered when a previously healthy patient aged 2 weeks to 3 months presents with projectile nonbilious vomiting.5 Hypertrophic pyloric stenosis is most likely to occur in Caucasian first-born males (male:female predilection of 4:1).6 Children of mothers with a history of hypertrophic pyloric stenosis have between a 7% (for male) and 20% (for female) risk of developing the condition.7 Patients with this condition may present with dehydration from repeated vomiting and decreased feeding. On physical examination, the experienced clinician can palpate an olive-sized mass in the right upper quadrant.
Ultrasound is the imaging modality of choice in this setting and demonstrates a hypertrophied muscle, manifested as a thickened hypoechoic layer, with one wall measuring > 3 mm in thickness, from the linear echogenic mucosal line to the outer edge of the hypoechoic muscle, and longer than 15 to 17 mm in length8 (Figure 2). The abnormally thickened appearance of the pylorus on ultrasound is often described as the cervix sign on sagittal images and target sign on transverse images. Additionally, the antral nipple sign can be seen at the gastric outlet portion. The patient should be placed right side down so that fluid passing through the pylorus can be observed, and gas from the stomach does not obscure visualization. After initial images are obtained, the patient may be given sugar water or formula while lying on his/her right side to demonstrate the passage of material through the pyloric channel while not over-distending the stomach.
Potential pitfalls in the imaging of pyloric stenosis include pylorospasm, which causes transient pseudo-thickening of the pylorus, and inadvertent imaging of the gastroesophageal junction. To avoid these problems, it is important to reimage the patient in 10 minutes to determine whether the pyloric muscle has changed. Additionally, attention must be paid to key anatomic landmarks to ensure that the pylorus is being imaged.9
If the pylorus consistently appears borderline in measurement (2-3 mm) and does not relax, follow-up ultrasound examination should be considered, especially in younger infants (aged < 1 month) and premature infants, as studies have shown a correlation between dimension of the pylorus and patient weight. These findings may represent pyloric stenosis in evolution; therefore, continued follow-up is recommended.10-12
On an upper GI series, pyloric stenosis will present as delayed gastric emptying along with vigorous contractions of the stomach (caterpillar sign). The pylorus appears abnormally elongated with a narrow lumen, resulting in the string sign (Figure 3); this sign may appear duplicated because of puckering of the mucosa (double-track sign). The thickened pylorus also indents the contrast-filled antrum or the base of the duodenal bulb, referred to as the shoulder sign and mushroom sign, and the pyloric entrance may be beak-shaped (beak sign).13
The treatment for hypertrophic pyloric stenosis consists of pyloromyotomy. Repeat ultrasound examinations may be performed if the patient persistently vomits; however, the pyloric muscle may remain thickened after successful surgical intervention and may not resolve to normal thickness for up to 5 months.14
Malrotation refers to abnormal fixation of the gut during embryogenesis, leading to a shortened mesenteric pedicle. This abnormality occurs in an estimated 1/500 live births.13,15 Malrotation may result in midgut volvulus, which is a surgical emergency that classically presents in the newborn period with bilious emesis. A missed or delayed diagnosis of midgut volvulus can lead to bowel ischemia, necrosis, and even death.
Although conventional radiographs may be obtained to evaluate for obstruction, these studies do not exclude the diagnosis of malrotation and midgut volvulus, which are most commonly identified on an upper GI series performed after the patient ingests oral contrast media (nonionic water soluble or barium).16 On an upper GI series, signs of normal rotation include the second and third portion of the duodenum positioned posteriorly into the retroperitoneum on the lateral view, nearly superimposed on one another, and the duodenal-jejunal junction to the left of the spine at the level of the pylorus/duodenal bulb on the anteroposterior (AP) view (Figure 4B).15 Malrotation is diagnosed when the second portion of the duodenum is not seen in the posterior location on the lateral view, the duodenum does not cross the midline, and/or the duodenal-jejunal junction is not at the height of the duodenal bulb. Classic findings of malrotation with midgut volvulus include the corkscrew sign, dilation and beaking of the proximal duodenum, or an abrupt termination of contrast (Figure 4A). Emergent surgical intervention with a laparoscopic Ladd’s procedure is indicated when malrotation is diagnosed; delay in diagnosis or treatment may lead to bowel ischemia and/or necrosis.15
Ultrasound has been described in the literature as another method for diagnosing malrotation through evaluation of the orientation of the superior mesenteric vessels and the retroperitoneal duodenum.13,17 The normal anatomic relationship demonstrates the superior mesenteric vein to the right of the superior mesenteric artery (Figure 5). However, there are variations in anatomy and, although a normal relationship is seen in 91% of patients, the presence of a normal relationship does not exclude malrotation. Likewise, an abnormal orientation does not confirm the diagnosis of malrotation; rather, it warrants further investigation with an upper GI exam.16,18,19 The upper GI series remains the current standard because of its ability to provide a timely and accurate diagnosis.
Duodenal and pancreatic traumas are rare injuries that can occur in the setting of blunt abdominal trauma. Common and important causes include child abuse, bleeding disorders, and seatbelt or handlebar injuries. The duodenum and pancreas are prone to injury due to their anatomic position anterior to the spine.20 Clinical signs are nonspecific initially and can often be overshadowed by concurrent solid organ injuries; therefore, the radiologist must be mindful of the mechanism of injury when evaluating trauma patients.21
Although the evaluation of duodenal trauma can be made using a variety of imaging modalities, CT is the mainstay of diagnosis.20 A mixed-attenuation mass at the second or third portion of the duodenum is highly suggestive of duodenal hematoma on CT. The presence of retroperitoneal free gas should alert the radiologist to the possibility of an associated duodenal perforation.21 Secondary signs may include adjacent retroperitoneal free fluid or hemorrhage. Upper GI exam may indirectly identify extraluminal mass effect or an intraluminal filling defect in the affected portion of the duodenum, and ultrasound may demonstrate a hypoechoic, heterogeneous, avascular mass in this location (Figure 6). MRI often demonstrates a mass of variable signal intensity due to evolving blood products in the region of the duodenum and is generally reserved for problem solving, such as in cases of smaller duodenal hematomas or for evaluating secondary injuries associated with the biliary ducts (Figure 7).
CT is also the preferred modality for evaluating pancreatic trauma, despite its limitations in enhancement pattern for such cases. Trauma CT scans are typically performed in the portal venous phase, whereas optimal pancreatic enhancement occurs approximately 35 to 40 seconds after intravenous contrast administration. Nonetheless, given the lack of sufficient data and the need to evaluate concurrent solid organ injuries, CT in the portal venous phase is still considered the best initial examination for these patients. If the CT scan is suggestive of pancreatic trauma, a follow-up MR/MR cholangiopancreatography examination can be performed to obtain further information.21 On CT, pancreatic hematomas present as heterogeneous collections between the pancreas and splenic vein with or without peri-pancreatic inflammatory changes. Altered pancreatic parenchymal enhancement may be present and may represent pancreatic contusion. Pancreatic hemorrhage may be identified by active contrast extravasation on CT. Additionally, there may be pancreatic laceration or transection. In these cases, it is important to assess the integrity of the pancreatic duct, as this is paramount in determining prognosis and the need for emergent endoscopic retrograde cholangiopancreatography or surgery.22
Pancreatic and duodenal hematomas are most often graded according to the American Association for the Surgery of Trauma scoring system, with hematomas graded from I to V based on the location and the extent of contusion or laceration. This grading system is useful for determining which cases are appropriate for surgical intervention and which can be managed conservatively.21.23 (Tables 1 and 2).
Intussusception refers to telescoping of one segment of bowel into another, leading to edema and venous congestion within the bowel wall.24,25 Ileocolic intussusception is a common pediatric emergency, usually occurring between ages 6 months and 2 years.24 In this age group, approximately 95% of cases have no pathological lead point, regardless of recurrence.25,26 The classic clinical presentation is episodic abdominal pain, currant-jelly stools, and a palpable abdominal mass; however, less typical symptoms can often be confused for more benign etiologies (such as gastroenteritis), delaying diagnosis.27
Conventional radiographs in these patients may reveal a small bowel obstruction and/or a paucity of bowel gas in the right hemiabdomen. Occasionally, a soft-tissue mass may be seen within the colon.26 However, abdominal ultrasound is the diagnostic examination of choice in this setting with a specificity of 100%. On abdominal ultrasound, intussusception has a classic “target” appearance of multiple concentric rings and central mesenteric fat in the transverse plane (Figure 8A) with a typical size of 2.5 to 5 cm.25-27 On longitudinal images, intussusception often shows peripheral hypoechoic bowel with central increased echoes, referred to as the “pseudo-kidney” appearance (Figure 8B). The measurement of the intussusception can assist in differentiating between ileocolic and small bowel-small bowel intussusception; this is an important distinction, as a small bowel-small bowel intussusception is smaller, typically self-limiting, and typically does not require intervention. Some ultrasound findings such as intussuscepted lymph nodes (Figure 8A) and interloop fluid may indicate increased difficulty in an attempt at reduction, although these features are not considered contraindications to reduction.25
Once ileocolic intussusception has been diagnosed, the patient should undergo prompt reduction via air or contrast enema to prevent complications such as bowel wall ischemia and/or necrosis, perforation, and shock.25 Nonoperative management is the treatment of choice, with surgery reserved for patients in whom reduction is unsuccessful or for those with contraindications to fluoroscopic reduction (eg, free air, peritonitis, or signs of shock). Intussusception reduction is not without risk, such as is tension pneumoperitoneum secondary to perforation during pneumatic reduction. Therefore, close monitoring by nursing staff and notification of the surgical department are of the utmost importance in this setting.28 An intravenous line should be placed for immediate access in case of an emergency and for the administration of fluids before the procedure. Additionally, the radiologist should have access to a needle for emergent decompression should pneumoperitoneum occur.28
Pneumatic or hydrostatic reduction may be performed to put pressure on the intussusceptum and push it back into its proper anatomic position.25,26 In both procedures, an enema tube is placed and sealed in the patient’s rectum with tape. In pneumatic reduction, air is pumped manually through the tube into the colon, pushing the intussusceptum through the ileocecal valve. A pressure of 120 mm Hg or less should be maintained; if the patient engages in a Valsalva maneuver, the pressure may intermittently increase. When the mass is no longer seen and air enters the distal small bowel, the reduction is considered successful. A postreduction image showing the lack of pneumoperitoneum at the end of the procedure is recommended.29 In hydrostatic reduction, water-soluble near-isotonic or iso-osmolar contrast is hung 3 feet above the table and allowed to flow freely into the colon.29 When the intussusceptum reduces, contrast is seen in distal small bowel loops. Advantages of the pneumatic technique include faster reduction, decreased radiation, and air rather than contrast entering the peritoneal cavity in cases of perforation.26,30 Delayed attempts at air enema may be performed when initial attempts are unsuccessful, as long as the patient’s condition remains stable and initial attempts demonstrated improvement or partial reduction in the intussusception.
Appendicitis is one of the most common causes of acute abdominal pain in children and represents up to 80% of pediatric surgical emergencies in the United States.31 The appendix is a blind-ending tube at the caput cecum. Acute appendicitis usually occurs as a result of appendiceal luminal obstruction, followed by fluid accumulation, luminal distention, inflammation, and eventually perforation.32 Classic symptoms include periumbilical pain (initially), right lower quadrant pain localizing to McBurney’s point, and flank pain (in a retrocecal appendix). There may be associated fever, nausea, and vomiting; however, this progression is seen in only a minority of cases. Children often present with vague and nonspecific signs and symptoms.
Abdominal radiographs are frequently normal in cases of appendicitis, apart from occasional findings such as a calcified appendicolith (< 10% of cases), obliteration of the right psoas margin, splinting leading to lumbar dextroscoliosis, and right lower quadrant air-fluid levels that are nonspecific.13 Hence, initial imaging of appendicitis typically involves ultrasound or CT and occasionally MRI. There is significant debate regarding which imaging modality is preferred in the pediatric population. Advantages of ultrasound include lack of ionizing radiation, low cost, lack of intravenous contrast, and the ability to manually compress the appendix. Studies have shown that with carefully regimented techniques, ultrasound can achieve > 98% specificity and sensitivity, as well as positive and negative predictive values in pediatric patients with appendicitis.33 Sonographic findings of appendicitis include a dilated appendix measuring at least 6 mm in the maximal outer diameter, a lack of compressibility, adjacent inflammatory changes (increased peri-appendiceal echogenicity of the mesenteric fat), and hyperemia on Doppler imaging (Figure 9). Additionally, a fluid-filled appendix may appear targetoid. Appendicoliths, peri-cecal or peri-appendiceal fluid, or enlarged mesenteric lymph nodes may also be present.
Advantages of CT over ultrasound include reduced operator dependence, enhanced visualization of tissues and surrounding phlegmon/abscess, and superior imaging of obese patients. CT scans are optimal when the study is performed with intravenous contrast. Findings of appendicitis on CT include a dilated fluid-filled appendix > 6 mm, appendiceal wall thickening and enhancement, and peri-appendiceal inflammatory changes and/or fluid. Appendicoliths, phlegmon, abscess, and/or mesenteric adenopathy may also be seen. CT scans should be used judiciously in children with care taken to use the lowest possible dose appropriate for the patient’s size and to use only a single phase.31
MRI of the appendix has recently become a topic of interest in the pediatric literature because of increased awareness of radiation exposure from CT. MRI for acute appendicitis has been shown to have a high sensitivity and specificity without negative effect on clinical outcomes.34 MR findings for acute appendicitis mimic those of CT, including a dilated tubular structure, peri-appendiceal fluid/inflammation, wall thickening, and phlegmon or abscess formation (Figure 10).
When acute appendicitis is diagnosed, the patient should be admitted to the hospital for surgical consultation. Depending on whether the imaging findings suggest the presence of an uncomplicated appendicitis, without abscess, or complicated, with intra-abdominal or intra-pelvic abscess, patients should undergo either surgical intervention or, less often, treatment with minimally invasive techniques/antibiotic therapy.35
Mesenteric adenitis typically presents in young adolescents with nondescript right lower abdominal pain, with or without fever, nausea, vomiting, and elevated white blood cell count. This condition is a common mimic of appendicitis clinically and can also mimic other conditions, such as colitis or pelvic inflammatory disease.36 Mesenteric adenitis is self-limiting, generally requiring only conservative management with resolution within approximately 2 weeks.
Mesenteric adenitis is characterized by a cluster of more than 3 lymph nodes in the right lower quadrant, often > 5 to 8 mm in the short axis.36,37 Ultrasound and CT can both be used to diagnose this condition. Ultrasound with graded compression demonstrates enlarged lymph nodes in the right lower quadrant; the appendix is normal, and there is no bowel inflammation. Benefits of ultrasound include the lack of radiation and low cost; however, the examination is operator-dependent, and without definitive visualization of the appendix, the etiology for enlarged lymph nodes is unclear.37 CT remains the most sensitive modality to evaluate right lower quadrant pain, with its most significant limitation being radiation exposure.
Meckel diverticulum is the most common congenital abnormality of the GI tract. This true diverticulum results from the incomplete obliteration of the omphalomesenteric duct during embryologic development. Most cases of Meckel diverticulum are asymptomatic and found incidentally.38 In younger children who are symptomatic, the most common presentation is painless brick-red rectal bleeding, whereas older children tend to present with intestinal obstruction.38,39 Approximately 59% of Meckel diverticula contain heterotopic tissue, most commonly gastric tissue, followed by pancreatic tissue. Meckel diverticulum can lead to intestinal obstruction, act as a lead point for intussusception, result in volvulus, or become incarcerated within an inguinal hernia (Littre hernia).29
Meckel diverticulum can be identified on multiple imaging modalities; however, in a pediatric patient with rectal bleeding, technetium-99 (Tc-99) pertechnetate is the most sensitive modality available (sensitivity, 85%; specificity, 95%).29,38 The radiotracer accumulates in the parietal cells of the ectopic gastric mucosa within the right lower quadrant Meckel diverticulum (Figure 11A). False negatives may be seen in the setting of no or minimal ectopic gastric tissue or impaired blood supply to the bowel, whereas false positives may be seen in the setting of inflammatory bowel disease (IBD).38,39
Alternate imaging may be performed when the clinical picture is confusing. On ultrasound and CT, a blind-ending tubular structure may be identified near the cecum with adjacent inflammatory changes, similar in appearance to an inflamed appendix but in a more proximal location. Small bowel follow-through may show a blind-ending tubular structure originating from the distal ileum on the anti-mesenteric side (Figure 11B).
Surgical management of symptomatic Meckel diverticulum always results in excision. However, controversy exists regarding how to manage asymptomatic cases, with some authors suggesting removal regardless of symptomatology and others claiming that the complications of surgical excision outweigh the benefit of removal if asymptomatic.38
Inflammatory bowel disease (IBD) is a complex chronic disease that is often difficult to diagnose in adolescents because of vague and intermittent symptoms, such as abdominal pain, diarrhea, and weight loss. IBD is thought to be caused by immune dysregulation leading to granulomatous bowel inflammation and ulceration. It is classified as either Crohn disease or ulcerative colitis (UC).40 Imaging plays a key role not only in the diagnosis but also in the management and monitoring of patients with IBD.
Crohn disease typically involves the small bowel, most commonly the terminal ileum, although it can affect the entirety of the bowel. Frequent complications include the formation of fistulas and sinus tracts. Although the imaging findings of Crohn disease can be seen on a variety of modalities, fluoroscopy can only show the bowel complications, whereas cross-sectional imaging can demonstrate the extra-intestinal manifestations of disease. CT and MR enterography have a higher sensitivity for detecting these specific findings and can better assess bowel wall thickening, hyperemia, lymphadenopathy, perforation, and abscess. MRI is also useful in assessing perianal disease, including fistula formation, and in distinguishing between active bowel inflammation and bowel fibrosis.41 Active inflammation demonstrates mucosal enhancement on postcontrast T1 images, increased T2 signal on fat-saturated images, wall thickening > 3 mm, and restricted diffusion (Figure 12). In contrast, chronic changes such as bowel fibrosis are characterized by the lack of enhancement on postcontrast imaging and fibrofatty proliferation.42
Ulcerative colitis primarily involves the colon and rectum and is associated with a nearly 30-fold increased risk of colorectal cancer. Fluoroscopic findings of ulcerative colitis include edematous, thickened haustra; symmetric colonic narrowing; punctate collections of contrast leading to mucosal stippling; and postinflammatory polyps. As with Crohn disease, ulcerative colitis imaging findings are better delineated on CT and MR compared to fluoroscopy. A specific CT finding of UC includes the halo sign, which appears as a low attenuation ring around the bowel mucosa resulting from submucosal fat deposition. Additionally, the bowel contour appears smooth in ulcerative colitis, whereas the bowel in Crohn disease tends to be more irregular. Similar findings can be seen on MRI;43 additionally, MRI can be used to evaluate associated extra-intestinal findings such as sclerosing cholangitis, cirrhosis, and hepatitis.
Although CT and MRI are the preferred and most commonly used methods for evaluating the bowel, ultrasound also may be useful for screening given its low cost and lack of ionizing radiation.42 On color Doppler ultrasound, ulcerative colitis appears as thickened, inflamed bowel loops with hyperemia.
Pediatric GI complaints are among the most common and confusing clinical scenarios seen in the emergency department. Radiologists can help clarify the clinical picture in such cases by employing the most appropriate and useful imaging modalities and having a detailed understanding of the imaging appearances of various emergent GI pathologies. When choosing imaging modalities in children, radiologists must remain vigilant of the risks of radiation exposure in this patient population and be judicious in selecting the best modality to establish a diagnosis.
Lampl BS, Gupta A, Park E. Imaging of Pediatric Gastrointestinal Emergencies. J Am Osteopath Coll Radiol. 2017;6(1):5-14.