Abdominal US in Pediatric Inflammatory Multisystem Syndrome Associated with COVID-19.

Introduction Children with Pediatric Inflammatory Multisystem Syndrome Temporally associated with SARS-CoV-2 (PIMS-TS), also known as Multisystem Inflammatory Syndrome in Children (MIS-C), present with abdominal pain amongst other non-specific symptoms. Whilst initial imaging features of PIMS-TS have been reported, the duration of sonographic features remain unknown. Purpose To describe the abdominal ultrasound features of PIMS-TS at initial presentation and follow-up. Materials and Methods A retrospective review of children presenting with clinical features suspicious for PIMS-TS between April 2020 and June 2021 was carried out. Ultrasound features were documented and reviewed on initial presentation and follow up. Descriptive statistics were used and interobserver variability calculated. Results Of 140 children presenting with suspected PIMS-TS, 120 had confirmed PIMS-TS (median 9 years, interquartile range 7-12 years, 65 male) and 102 underwent abdominal ultrasound (US) at presentation. PIMS-TS was present as a single pathology in 109/120 (91%) and abdominal symptoms were present in 104/109 (95%). US examinations were abnormal in 86/102 (84%), with ascites being the most common abnormality in 65/102 children (64%, 95% CI: 54, 73%). Bowel wall thickening was present in 14/102 (14%, 95% CI: 7, 20%) children and mesenteric inflammation in 16/102 (16%, 95% CI: 9, 23%), all of whom presented with abdominal symptoms. Of these, the distal and terminal ileum were most involved (8/14, 57%). Abdominal symptoms decreased to 7/56 (13%) in children followed up at 6 months. Thirty-eight children had follow-up ultrasound and the presence of bowel inflammation had decreased to 3/27 (11%, 95% CI: -1, 23%) in the less than 2 months group and 0/17 (0%) in the greater than 2-month follow-up group. Conclusion 14% of children with Pediatric Inflammatory Multisystem Syndrome temporally associated with COVID-19 (PIMS-TS) had abdominal ultrasound findings of bowel inflammation and 16% had mesenteric oedema. All ultrasound abnormalities resolved after 2 months.