|ECR 2019 / C-1157|
|Role of ultrasound in acute abdomen in children|
Findings and procedure details
Role of ultrasound:
Sonography has become an extraordinarily useful modality in the evaluation of children. It is preferable over CT due to: lack of radiation exposure, noninvasiveness and painlessness. Inordinate preparation is not required, and sedation is rarely necessary. The apparent safety of this nonionizing procedure permits repetitive scanning as necessary during an examination and for follow-up studies. Scanning can be accomplished in multiple planes and with the patient in virtually any position.
Ultrasonography can provide assessment of areas and organs that cannot be adequately examined by conventional radiography. In contrast to the technique of computed tomography, the imaging produced is not adversely affected when the patient has a paucity of body fat. The potentially rapid diagnostic yield of ultrasonography is a factor that also merits consideration when diagnostic imaging of the acutely ill patient is required.
Sonogrophic findings of different diagnoses:
Imaging studies are not generally indicated for diagnosis of infectious diarrhea. However, symptoms may sometimes mimic abdominal conditions, such as appendicitis.
Real time US usually shows multiple dilated fluid filled bowel loops that are otherwise normal. It may reveal transient small-bowel intussusception during periods of hyperperistalsis. The terminal ileum and the cecum are often involved in bacterial enteritis, such as with Yersinia; this may be termed infectious ileocecitis. Right lower quadrant lymphadenopathy may be seen.
Classically, appendicitis has been considered a clinical diagnosis with acceptable negative appendectomy rates between 12% and 20%.
The US examination is performed with a high-frequency linear transducer that ranges from 9 to 15 MHz. Graded compression is essential, because it displaces overlying bowel gas and also helps to decrease the distance between the transducer and the appendix. Additionally, compression helps differentiate normal bowel from an inflamed appendix.
The single most important US sign of an inflamed appendix is a non-compressible, blind-ending tubular structure with a transverse diameter measuring greater than 6 mm. Additional sonographic signs include appendicular wall thickness greater than 3 mm, wall hyperemia on color Doppler, perpendicular hypoechoic halo that reflects appendicular wall edema, perpendicular hyper echogenicity that reflects perpendicular edema, and the presence of an appendicolith. Early uncomplicated appendicitis will demonstrate a target-like appearance with hypo echogenicity centrally as a result of luminal distension with pus or fluid, increased echogenicity of the inflamed submucosa, hypoechoic edematous serosa, and increased perpendicular echogenicity.
Malrotation with Midgut Volvulus:
Ultrasound exam can show an inverted relationship between the superior mesenteric artery (SMA) and superior mesenteric vein (SMV) and the whirlpool sign in patients with volvulus.
Intussusception is an acquired invagination of the bowel into itself.
Ultrasound is highly sensitive in the detection of intussusception. Although the diagnosis can be confirmed when the enema procedure is performed, ultrasound is the primary imaging modality for the initial diagnosis.
Ultrasound signs include:
-Target sign (also known as the doughnut sign)
-Pseudo kidney sign
-Crescent in a doughnut sign.
However, findings that indicate the presence of a transient intussusception include short length (< 3 cm), thin diameter (< 2.5 cm), and location within the small bowel.
The main role of imaging in patients with Crohn disease is to detect the areas of involvement and further segregate disease into inflammatory, obstructive, and fistulizing disease and to assess response to therapy. Upper GI examinations with SBFT have been frequently used to evaluate jejunoileal manifestations of Crohn disease.
US is an excellent modality in the evaluation of patients with Crohn disease. The involved bowel segment shows a thickened wall with visible transition to uninvolved bowel. Often bowel loops are separated by intervening mesenteric fat, and small lymph nodes are seen. Bowel wall hyperemia has been noted to correlate with disease activity. Small abscesses may be missed on US, and it is possible that remote areas of disease may be missed because of overlying bowel gas.
Most Meckel diverticula remain asymptomatic, with complication rates estimated at 4% to 6%,
decreasing with age.
In patients with inflamed diverticula, by ultrasound, inflamed diverticulum appears as blind-ending structure, surrounded by inflammation. On cross-sectional imaging the findings may be very difficult to distinguish from appendicitis in some cases; however, in other cases, a much larger size and periumbilical location may suggest the correct diagnosis preoperatively.
Presentation is similar to acute appendicitis, hence is a differential diagnosis for right iliac fossa (RIF) pain.
Features on us include:
-Enlarged lymph nodes, 3 or more nodes with a short-axis diameter of at least 5 mm clustered in the right lower quadrant. Enlarged lymph nodes are located anterior to the right psoas in the majority of cases, or in the small bowel mesentery 6.
-Ileal or ileocecal wall thickening may be present
-A normal appendix (if seen)
The most common cause of pancreatitis is idiopathic or posttraumatic.
On ultrasound, a more reliable diagnostic feature of acute pancreatitis is dilatation of the pancreatic duct. Poorly defined glandular borders and peri-pancreatic fluid or localized fluid collections can be seen. Ultrasound is also useful in the characterization of the margins and contents (low-level echoes, septations, debris) of collections complicating pancreatitis, which determine the amenability of the collections to drainage
Cholelithiasis and Choledocholithiasis:
Although in the past cholelithiasis was believed to be rare in children without hemolytic anemia, it is being diagnosed more frequently as a result of increased utilization of sonography.
Four general sonographic patterns are described. (1) Simple echogenic, shadowing, mobile stone (single or multiple). (2) Collections of very tiny, sand-like stones, termed milk of calcium, which may mimic gallbladder sludge; acoustic shadowing may be seen only in the aggregate. (3) If bile within the gallbladder is of high density, the stones may seem to float on the surface, giving an apparent fluid-fluid level. (4) Relates to stones within a contracted gallbladder, in which case the stones produce an echogenic double arc known as the wall echo shadow (WES) complex. This pattern may be seen in patients with a chronically contracted gallbladder
or those who have not fasted sufficiently.
It is uncommon in infants and children. However, the mortality rate is at least 30% because of concomitant disease and the potential for rapid progression, to gallbladder gangrene or perforation.
The sonographic findings of calculous and non-calculous cholecystitis are identical except for the lack of gallstones in the latter condition. Sonographic findings of cholecystitis are nonspecific, but when combined they may indicate a specific diagnosis. The best indicators of acute cholecystitis include cholelithiasis, a sonographic Murphy sign, and striated gallbladder wall edema with wall thickening greater than 3.5mm.
Other findings include gallbladder distention, pericholecystic fluid, adjacent rim of hypo-echogenicity or hyper-vascularity in the liver, biliary sludge.
It is caused by partial or complete rotation of the ovary on its pedicle, compromising first lymphatic, then venous, and finally arterial flow, and leading to hemorrhagic infarction. It is most often seen in peri-pubertal or older girls.
Ovaries involved in torsion have a variable appearance related to the degree of internal hemorrhage, stromal edema, and infarction that has occurred by the time they are imaged. The ovaries may appear cystic, cystic with septations, cystic with a debris layer, complex with mixed solid and cystic components, or solid. One relatively specific ultrasound image is a unilaterally enlarged solid ovary with multiple peripheral follicles. An acute ovary that has sustained torsion is larger than a normal ovary.
Color Doppler imaging in the analysis of cases of ovarian torsion is confusing with regard to its reliability. Doppler imaging may have a role in assessing the recovery of an ovary that has undergone torsion in follow-up studies after surgical treatment.
Thematically related posters
ECR 2019 / C-0579
Emergency radiology in full color: radio-surgical correlation in urgent abdominal pathology