Appendicitis in the Transplant Patient: A Common Problem in a Less Common Patient Population

Background: Acute appendicitis has not been well-studied in solid organ transplant (SOT) recipients. We hypothesized that SOT patients with appendicitis would exhibit an atypical presentation, characterized by blunted inflammatory responses. Methods: We performed a retrospective cohort study of adult SOT and non-SOT patients diagnosed with appendicitis across multiple hospitals from January 2011 to July 2025. Non-transplant patients were matched 1:1 to SOT recipients using nearest-neighbor propensity score matching on age, gender, and body mass index (BMI). Demographics, vital signs, laboratory values, management, and antibiotic use were assessed in the full and matched cohorts. Results: Among 4,049 SOT recipients, 54 (1.3%) developed appendicitis; median time from transplant to diagnosis was 2.5 y (inter-quartile range 1.1–5.3). In the propensity-matched cohort (54 transplant, 54 matched non-transplant controls), SOT recipients demonstrated a lower mean WBC (10.1 vs. 12.7 × 10 9 /L, p = 0.011) than their non-SOT cohort, while length of stay remained significantly longer (mean difference + 3.96 d, p = 0.013). Rate of complicated appendicitis was not statistically different after matching (20.4% vs. 18.5%, p = 0.81); age was independently associated with complicated appendicitis ( p = 0.023). Among patients undergoing laparoscopic appendectomy, SOT recipients received significantly longer antibiotic courses than matched controls (rate ratio 1.79, p = 0.025). Conclusions: Appendicitis in SOT recipients presents with a blunted inflammatory response, lower leukocytosis, along with longer hospitalization and antibiotic courses after laparoscopic appendectomy. In contrast, the higher rate of complicated appendicitis observed in unmatched comparisons appears attributable to the older age of transplant recipients rather than a transplant-specific effect.