Abdominal US in Pediatric Inflammatory Multisystem Syndrome Associated with SARS-CoV-2 (PIMS-TS)

Abstract

Background Children with pediatric inflammatory syndrome temporally associated with SARS-CoV-2 (PIMS-TS), also known as multisystem inflammatory syndrome in children, present with abdominal pain among other nonspecific symptoms. Although initial imaging features of PIMS-TS have been reported, the duration of sonographic features remains unknown. Purpose To describe the abdominal US features of PIMS-TS at initial presentation and follow-up. Materials and Methods A retrospective review of children and young adults presenting with clinical features suspicious for PIMS-TS between April 2020 and June 2021 was carried out. US features were documented and reviewed at initial presentation and follow-up. Descriptive statistics were used and interobserver variability was calculated. Results Of 140 children and young adults presenting with suspected PIMS-TS, 120 had confirmed PIMS-TS (median age, 9 years; interquartile range, 7-12 years; 65 male patients) and 102 underwent abdominal US at presentation. PIMS-TS was present as a single abnormality in 109 of the 120 patients (91%) and abdominal symptoms were present in 104 of the 109 (95%). US examinations were abnormal in 86 of 102 patients (84%), with ascites being the most common abnormality in 65 (64%; 95% CI: 54, 73). Bowel wall thickening was present at US in 14 of the 102 patients (14%; 95% CI: 7, 20) and mesenteric inflammation was present in 16 (16%; 95% CI: 9, 23); all of these patients presented with abdominal symptoms. Among the patients with bowel wall thickening, the distal and terminal ileum were most involved (eight of 14 patients, 57%). Abdominal symptoms decreased to seven of 56 patients (13%) in those followed up at 6 months. Thirty-eight patients underwent follow-up US, and the presence of bowel inflammation had decreased to three of 27 patients (11%; 95% CI: -1, 23) in those followed up for less than 2 months and 0 of 17 (0%) in those followed up for more than 2 months. Conclusion Of 102 patients with pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 who underwent US at presentation, 14 (14%) had abdominal US findings of bowel inflammation and 16 (16%) had mesenteric edema. All US abnormalities resolved after 2 months. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by van Rijn and Pajkrt in this issue.

Graphical abstract

Figure 1:

Flowchart shows study case definition with symptoms, biochemical markers, and US findings at presentation and early (<2 months) and late (>2 months) follow-up. CRP = C-reactive protein, EPR = electronic patient record, FCP = fecal calprotectin, F/Up = follow-up, PIMS-TS = pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2, Sympt = symptoms.

Figure 2:

Graph compares monthly number of patients with suspected pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2 (PIMS-TS) referred to our tertiary hospital with the reported cases of COVID-19 in the United Kingdom. COVID-19 case data are from a publicly available database at https://coronavirus.data.gov.uk.

Figure 3:

Noncontrast US scan (transverse plane) of the right iliac fossa in a 7-month-old boy with pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2. Image shows extensive inflammatory change with abnormal lymph nodes in the right iliac fossa (arrow).

Figure 4:

Noncontrast US scan (transverse plane) of the right iliac fossa in a 10-year-old boy with pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2. Image shows distal ileal thickening (measured between “+” markers and labeled “1”) and ascites (arrow).

Figure 5:

Noncontrast US scan (longitudinal plane) in an 18-year-old man with pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2. Image shows an extensive thrombus in the inferior vena cava (arrow).

Figure 6:

Diagram shows sites of bowel inflammation detected on presentation US scans in 14 patients with pediatric inflammatory multisystem syndrome temporally associated with SARS-CoV-2. Nine patients had single-site involvement and five patients had more than one site involved. Numbers are instances of bowel inflammation at various sites in the 14 patients.