|ECR 2018 / C-2902|
|Ultrasonographic Assessment of Gastrointestinal Tract Disorders in a Pediatric Emergency: Iconografhic Essay and Literature Review|
Findings and procedure details
The Gastrointestinal tract including the stomach, small bowels and colon should be evaluated in all patients with acute abdomen.
The stomach has a normal wall thickness around 4 to 6 mm and it is better evaluated in the antrum full filled with water . Whereas the pylorus has a normal transverse diameter between 0.7-1.1cm , the length of pyloric canal is 1.0-1.3 cm and the thickness of the circular muscle is too thin to measure .
Normal bowel loops have a stratified pattern on high- resolution ultrasound with the following 5 layers: Mucosal interface with lumen (hyperechoic), mucosa (hypoechoic), submucosa (hyperechoic), muscularis (hypoechoic) and serosa (hyperechoic) (Fig.1). The small bowel loop has a thickness lower than 2.5mm; they are compressible and poorly vascularized. The jejunum is commonly located in the upper left quadrant of the abdomen and has more conniving valves. Whereas the Ileum is located in the inferior right quadrant of the abdomen and has less conniving valves. The colon contains more air, haustrações, and wall thickness is < 2 mm (Fig.2) [3-5].
We recommend a systematic examination of the small intestines and colon in all patients with acute abdominal complaints (Fig. 3). The examination of the small intestine is performed by passing the transducer across the abdomen, starting from the right flank and moving in vertical and parallel lines to the left flank. In order to examine the colon, the cecum should first be identified in the right iliac fossa, followed by the other segments towards the hepatic flexure, splenic flexure, moving from the left flank to the sigmoid. The rectum can be assessed using the full bladder as an acoustic window .
INFLAMMATORY BOWEL DISEASES
Inflammatory bowel diseases (IBD) primarily affect young adults, but in 15%–25% of cases, the initial disease starts in childhood.  The subtypes of IBD comprise crohn disease (CD), ulcerative colitis (UC), and IBD-unclassified (IBD-U).
The most common symptoms of CD displayed are abdominal pain, weight loss, and diarrhea; and for UC and IBD-U diarrhea, bleeding, and abdominal pain. 
Imaging findings: [9,10]
- Bowel wall thickness (> 3 mm) (Fig.4);
- Loss of the normally visible stratification;
- Increased Color-Doppler signal denoting hyperemia (Fig. 5);
- Relative decrease or lack in peristalsis indicating some degree of stiffness;
- Changes involving the surrounding mesentery, that appears thickened and hyperechoic;
- Enlarged mesenteric lymph-nodes;
- Intra abdominal complications: abscesses, fistulae (Fig. 6) and strictures.
Acute appendicitis is a common condition that requires emergency abdominal surgery in the pediatric population. It may occur at any age, with highest incidence among people between 10 to 20 years of age. .
Clinical features of appendicitis include abdominal pain that later is located in the iliac fossa, nausea or vomiting, anorexia, rebound tenderness, pyrexia and elevated white cell count .
Imaging findings :
- Appendiceal maximal outer diameter enlargement beyond 6 mm (most specific sign) (Fig. 7);
- peri-appendiceal hypoechoic halo associated with wall edema (Fig. 8);
- Appendiceal wall thickness ≥3 mm;
- Wall hyperemia in color Doppler exam;
- Echogenic edematous mesenteric fat stranding (Fig. 8);
- Presence of an appendicolith (Fig. 9);
The external iliac artery and vein, cecum and psoas muscle are good landmarks to find the appendix. But sometimes the appendix tip is located in a atypical position, including small pelvis, retrocaecal and near the liver (Fig. 10).
Appendicitis may complicate with perforation and abscess formation (Fig. 11 e 12).
Necrotizing enterocolitis (NEC) affects 1-5 % of the newborn admitted to the ICU. Its incidence is inversely proportional to the gestational age, being more frequent in patients with less than 28 weeks of gestation and weighing less than 1000grams .
The NEC etiology is multifactorial and involves damage to the immature intestinal mucosa, evolving to inflammation ischemia and necrosis.
The symptoms usually appear between the first and second week after birth and are really similar to those of the sepsis. They include lethargy, temperature and blood pressure instability, and apnea. The most specific symptoms related to the gastrointestinal tract are feeding intolerance, vomiting, diarrhea, and blood in the stool..
Imaging findings 
- Bowel echogenicity abnormality with loss of the hypoechoic muscle layer and overall increase in wall echogenicity (wall edema, inflammation or hemorrhage);
- Bowel wall thickening (> 2,7 mm);
- Bowel wall thinning (<1 mm );
- Punctate or granular increased echogenicities within the bowel wall (intramural gas) (Fig. 13);
- Increased color flow signal (Color Doppler signal with more than nine dots per square centimeter)
- Punctate or linear echogenicities within the main portal vein or its intrahepatic branches (portal venous gas) (Fig 13.);
- Echogenic lines or foci with posterior ring-down or comet-tail artifacts evident outside the bowel and posterior to the abdominal wall (free gas);
- Free intraperitoneal fluid;
- Focal fluid collections.
The vast majority of inguinal hernias in children is indirect  and it is ultimately the result of the failure of embryonic closure of the processus vaginalis (PV). Indirect hernia originates at the deep inguinal ring then passing inferiorly and medially through the inguinal canal. The inferior epigastric vessels are used as a landmark to locate the indirect hernia which is commonly located laterally to then.
The inguinal hernias can be classified as reducible, incarcerated or strangulated. In the reducible hernia, the herniated content may return to the interior of the abdominal cavity spontaneously or through the application of maneuver, whereas the incarcerated is stuck in the hernia bag mainly because of the intestinal edema. If not treated, the incarcerated hernia may evolve to a strangulated hernia resulted from the interruption of blood supply to the bowel loop, with a great risk of necrosis. .
Emergency surgery is indicated in cases of strangulated hernia and intestinal obstruction. While the strangulated hernia must be treated with emergency surgery.
Imaging findings :
- Inguinal canal width of 4 mm or more;
- Presence of fluid, bowel loops or omentum in the inguinal canal (Fig. 14);
- Extension of bowel loops or omentum into the scrotum (Fig. 14);
- Color Doppler US helps in the differential diagnosis between incarcerated and strangulated hernia (Fig 15).
HIPERTROPHIC PYLORIC STENOSIS
Pyloric stenosis is an acquired condition and occurs when the pyloric portion of the stomach becomes abnormally thickened, resulting in obstruction to gastric emptying.
Typically develops between 2–12 weeks of postnatal life. The main symptom is non-bilious vomiting. 
Imaging findings [20-22]
- Pyloric muscle thickness greater than 3 mm (the main parameter to be evaluated) (Fig. 16);
- Transverse diameter of the pylorus greater than 11 mm: cross section, measured between the external opposing pylorus margins. It is considered the least reliable parameter;
- Longitudinal diameter of the pylorus greater than 15 mm: longitudinal section, measured from the base of the duodenal bulb to the gastric antrum, accompanying the central echogenic line of the mucosa to determine it (Fig. 16);
- Mucus nipple sign: the redundant pyloric mucosa protrudes into the distended gastric antrum;
- Target or “doughnut" sign: cross section shows a hypoechoic ring of the hypertrophied pyloric muscle with the echogenic mucosa at the center;
- Gastric hyperdistension, increased peristaltic waves and retrograde peristalsis. Gastric peristaltic activity is not able to distend the pre-duodenal portion of the stomach.
Intussusception occurs when a portion of the digestive tract becomes telescoped into the adjacent bowel segment. The ileocolic intussusception is the most common type.
This condition usually occurs in children between 6 months and 2 years of age and is idiopathic in the majority of cases .
The classic clinical triad of abdominal pain, red currant jelly stool and palpable abdominal mass is not always present. In doubtful cases the U.S is an important tool to assess the need of surgical intervention .
Imaging findings [23,25]:
- Mass of 3–5 cm in diameter just deep to the abdominal wall;
- Doughnt or pseudo kidney sign: hypoechoic outer ring and a hyperechoic center (Fig. 17 e 18);
- Crescent-in- doughnut sign : transverse scans shows a eccentric semilunar, hyperechoic mesenteric fat that is pulled with vessels and lymph nodes into the telescoped bowel (Fig 19);
Ultrasonography also plays a role in documenting the presence or absence of pathologic lead points, including polyps, as in the Peutz Jeghrs syndrome (Fig. 20).
Malrotation represents an incomplete rotation of the intestine during fetal development. It’s related to increased risks of bowel obstruction, volvulus and bowel necrosis.
The clinical manifestations of the disease may vary. Some may be asymptomatic, some may present recurrent episodes of abdominal pain or vomiting, others with failure to thrive or even with acute obstruction secondary to volvulus.
- Dilated duodenum ;
- Dilated thick-walled bowel loops, mainly on the right of the spine ;
- “whirlpool" sign: clockwise wrapping of the uperior mesentery vein vein (SMV) and the mesentery around the superior mesentery artery (SMA), with is confirmed by color Doppler (Fig. 21) .
Ascariasis is the most common helminthic disease and affect mostly children in developing country
The larvae of Ascaris lumbricoides first penetrate the wall of the upper part of the intestines and migrate up through the vennules, lymphatics and portal circulation to the liver, the right side of the heart and the lungs. Then they reach the glottis and pass down through the esophagus and stomach to the intestine where they mature to adult worms and produce eggs. Ascaris can also migrate to the biliary system .
Intestinal obstruction may develop as a complication of intestinal ascariasis when a mass of worms obstructs the lumen of the small bowel.
- ‘bull’s eye’, ‘target mass’ or ‘doughnut-like mass’: a single ascaris at transverse section(Fig. 22) ;
- Triple line or four line sign: the worm at the longitudinal axis is seen as parallel echogenic lines separated by an anechoic area representing the fluid-filled alimentary tube of the worm. If the alimentary tract is empty the worn is seen as tree lines (Fig. 23)[31,32];
- Spaghetti like appearance or ‘worm mass’ : when more than one worm accumulate at the bowel .
Trichobezoar is a condition caused by the ingestion of hair. It’s well recognized but uncommon cause of upper abdominal pain with a mass.
- mass with a highly echogenic contours and with very intense sonic shadow (Fig 24 e 25) .
Thematically related posters
ECR 2018 / C-2121
Inflammatory Bowel Disease in Paediatrics- A review of relevant gastro-intestinal imaging modalities