Ultrasound assessment of acute appendicitis in paediatric patients: methodology and pictorial overview of findings seen

Abstract

Acute appendicitis is a common surgical emergency in the paediatric population. Computed tomography (CT) has been shown to have high accuracy and low operator dependence in the diagnosis of appendicitis. However, with increased concerns regarding CT usage in children, ultrasound (US) is the imaging modality of choice in patients where appendicitis is suspected. This review describes and illustrates the step-wise graded-compression technique for the visualisation of the appendix, the normal and pathological appearances of the appendix, as well as the imaging characteristics of the common differentials.

Teaching points: • A step-wise technique improves the chances of visualisation of the appendix. • There are often several causes for the non-visualisation of the appendix in children. • A pathological appendix has characteristic US signs, with several secondary features also identified. • There are multiple common differentials to consider in the paediatric patient.

Figures

Fig. 1

Longitudinal (a) and transverse (b) views using high frequency linear-array probe showing the caecum (small white arrows in b) and ascending colon in a 15-year-old girl

Fig. 2

Longitudinal image showing the caecum and ascending colon, as well as the adjacent psoas muscle posteriorly (small white arrows) in a 15-year-old girl

Fig. 3

A normal appendix is seen draped over the iliac vessels in a 10-year-old girl. This is thin-walled, measuring less than 6 mm in diameter (A width of 3 mm). The caecum can be seen in continuity with the appendix superior to it

Fig. 4

Longitudinal view of a thickened, oedematous appendix measuring 10 mm in diameter with surrounding increased echogenic omentum in an 8-year-old boy with confirmed appendicitis. Absent intraluminal gas is noted

Fig. 5

Transverse view of a thickened, oedematous appendix measuring 10 mm in diameter in an 8-year-old boy with confirmed appendicitis. Again, surrounding omentum of increased echogenicity is noted

Fig. 6

The wall of this oedematous appendix measures 4 mm in an 8-year-old boy with confirmed appendicitis. Increased echogenic omentum is seen adjacent to the appendix

Fig. 7

a A transverse view of an inflamed appendix in a 15-year-girl, showing the target sign appearance. b Similar appearances in an 11-year-old boy. This target sign comprises a hypoechoic fluid-filled centre (white arrow), inner hyperechoic mucosal/submucosal ring (white asterisk), and outer hypoechoic ring (dashed white arrow)

Fig. 8

Appendicoliths (labelled) causing posterior acoustic shadowing in two patients, a 15-year-old girl (a) and a 10-year-old boy (b). The thickened, fluid-filled appendix is labelled in b (small white arrows)

Fig. 9

a Increased Doppler signal in a thickened, oedematous appendix in an 8 year-old-boy. b Similar appearances noted in a 10-year-old girl. The increased Doppler signal indicates hyperaemia

Fig. 10

Small pocket of free fluid in the region of the appendix (white arrow) in a 10-year-old girl with confirmed appendicitis

Fig. 11

Omental fat with increased echogenicity with a mass-like appearance (small white arrows) in a 12-year-old boy with confirmed appendicitis

Fig. 12

Multiple lymph nodes (arrows) in the mesentery of the periappendiceal region in an 8-year-old girl with confirmed appendicitis

Fig. 13

Increased echogenic free fluid in the right iliac fossa (indicating pus) with adjacent thickening of the peritoneum in a 2-year-old girl with confirmed appendicitis

Fig. 14

Loops of dilated, fluid-filled small bowel in a 2-year-old girl with confirmed appendicitis. Echogenic free fluid is seen adjacent to the bowel indicating pus (white arrow)

Fig. 15

Large collection (small white arrows) in a 4-year-old boy with a perforation secondary to appendicitis

Fig. 16

Right iliac fossa inflammatory mass in a 14-year-old boy with proven appendicitis

Fig. 17

Fluid-filled dilated appendix in a retrocaecal position (small white arrows) in a 15-year-old girl. Note is made of an appendicolith within the appendix

Fig. 18

Longitudinal view of the terminal ileum in a 10-year-old boy. The terminal ileum is thickened with luminal narrowing. The patient was subsequently confirmed to have Crohn’s disease

Fig. 19

Transverse view of a thickened terminal ileum in a 10-year-old boy. Again, luminal narrowing is seen with surrounding increased echogenic omentum. The patient was subsequently confirmed to have Crohn’s disease

Fig. 20

a Haemorrhagic cyst in a 12-year-old girl presenting with right iliac fossa pain. A large, thin-walled right adnexal cyst (white arrows) is seen with a lace-like pattern of internal echoes. b Haemorrhagic cyst in a 13-year-old girl presenting with lower abdominal pain. Similar appearances to a are identified (white arrows), with a small amount of adjacent free fluid in the right adnexal (black arrow)

Fig. 21

Mesenteric adenitis. Multiple enlarged lymph nodes in the right iliac fossa of a 7-year-old girl. Adjacent mesenteric increased echogenicity and a small pocket of free fluid (white arrow) are noted. A normal appendix was identified