Rapid non-contrast magnetic resonance imaging for post appendectomy intra-abdominal abscess in children

Acute appendicitis, especially if perforated at presentation, is often complicated by postoperative abscess formation. The detection of a postoperative abscess relies primarily on imaging. This has traditionally been done with contrast-enhanced computed tomography. Non-contrast magnetic resonance imaging (MRI) has the potential to accurately detect intra-abdominal abscesses, especially with the use of diffusion-weighted imaging (DWI). To evaluate our single-center experience with a rapid non-contrast MRI protocol evaluating post-appendectomy abscesses in children with persistent postsurgical symptoms. In this retrospective, institutional review board-approved study, all patients underwent a clinically indicated non-contrast 1.5- or 3-Tesla abdomen/pelvis MRI consisting of single-shot fast spin echo, inversion recovery and DWI sequences. All MRI studies were reviewed by two blinded pediatric radiologists to identify the presence of a drainable fluid collection. Each fluid collection was further characterized as accessible or not accessible for percutaneous or transrectal drainage. Imaging findings were compared to clinical outcome. Seven of the 15 patients had a clinically significant fluid collection, and 5 of these patients were treated with percutaneous drain placement or exploratory laparotomy. The other patients had a phlegmon or a clinically insignificant fluid collection and were discharged home within 48 h. Rapid non-contrast MRI utilizing fluid-sensitive and DWI sequences can be used to identify drainable fluid collections in post-appendectomy patients. This protocol can be used to triage patients between conservative management vs. abscess drainage without oral/intravenous contrast or exposure to ionizing radiation. (orig.)