Non-operative management of small post-appendicectomy intra-abdominal abscess is safe and effective

Background: Intra-abdominal abscess (IAA) post-appendicectomy occurs in 1.4–4.4% of cases. Non-operative management of small (<4 cm) post-appendicectomy IAA in children is well established, but minimal evidence exists in adults. Percutaneous catheter drainage is considered standard treatment for IAA, yet outcome data for post-appendicectomy IAA are sparse. The aims of this study were to assess the effectiveness of non-operative management of small (<4 cm diameter) IAA and the outcomes of percutaneous drainage for larger (>4 cm) IAA post-appendicectomy. Methods: A retrospective case note review of a series of patients with a post-appendicectomy IAA between 2006 and 2017 was conducted. IAAs were treated selectively; small (<4 cm) IAAs were managed non-operatively and larger IAAs were managed with percutaneous drainage. Results: A total of 4901 patients had an appendicectomy. Forty-two (0.9%) developed a post-operative IAA. Sixteen (38%) had a percutaneous drainage and 26 (62%) had non-operative management. The percutaneous drainage group had a higher proportion of complicated appendicitis (75%) compared to the non-operative group (42%, P = 0.04). The percutaneous drainage group had a significantly higher leucocytosis (P = 0.01) and C-reactive protein (P = 0.02). All patients managed non-operatively resolved without the need for invasive procedures. In the percutaneous drainage group, six had aspiration alone, nine had a percutaneous drain and one was abandoned. Three required repeat percutaneous drainage and four (25%) required operative drainage. Seven patients (34%) of the percutaneous drainage group had grade II or III complications. Conclusion: This case series study provides support that small (<4 cm) IAA post-appendicectomy can be safely and effectively managed non-operatively.