Acute abdominal pain in children: SAQ

This boy has acute appendicitis. The migration of pain from the periumbilical region to the right iliac fossa over a day, the anorexia and vomiting after the pain began, the low-grade fever, and the right iliac fossa tenderness with peritoneal signs of guarding and pain on coughing and hopping, together with the leukocytosis and neutrophilia, make appendicitis the leading diagnosis and demand active confirmation rather than discharge. ^[1]

Question 1 (10 marks)

Explain the pathophysiology behind the migration of pain, calculate and interpret his Pediatric Appendicitis Score, and describe the imaging you would arrange. (5 marks for the pain pathway; 3 marks for the score; 2 marks for imaging.) ^[1]

The migration of pain in appendicitis reflects the progression from visceral to somatic pain. Early obstruction and inflammation of the appendix irritate the midgut visceral afferents, which enter the spinal cord at around the tenth thoracic segment, where the abdominal wall around the umbilicus is also represented, so the pain is felt as a vague central periumbilical ache. As the inflamed appendix reaches the parietal peritoneum of the right lower quadrant, somatic pain from the segmentally innervated parietal peritoneum sharpens and localises to the right iliac fossa and is worsened by movement. This migration from central to right lower quadrant pain is the most discriminating historical feature for appendicitis. ^[1]

His Pediatric Appendicitis Score is ten out of ten. The score combines eight variables into a maximum of ten points: right lower quadrant tenderness scores two, and pain on coughing, hopping or percussion scores two, while migration of pain, anorexia, nausea or vomiting, fever, leukocytosis and neutrophilia each score one. He has right lower quadrant tenderness, pain on coughing and hopping, migration, anorexia, vomiting, fever, leukocytosis and neutrophilia, so he scores the maximum. A high score places him in the high-risk band and prompts urgent surgical referral. ^[1]

Ultrasound is the first-line imaging modality in suspected appendicitis in children and is preferred because it avoids the ionising radiation of computed tomography. A systematic review has confirmed acceptable diagnostic accuracy for ultrasound even when performed by non-radiologists. Computed tomography is reserved for the case where ultrasound is equivocal and the child remains a diagnostic concern, and magnetic resonance imaging is an alternative in some centres. A pregnancy test is mandatory in any adolescent girl before imaging, though it is not relevant here. ^[2]