Clinical and Imaging Correlates of Pediatric Mucosal Appendicitis

Background: Mucosal appendicitis is a controversial entity that is histologically distinct from transmural appendicitis. There is mixed opinion regarding mucosal inflammation as a spectrum of appendicitis versus a negative appendectomy. The ability to distinguish these diagnoses preoperatively is of importance to prevent unnecessary surgery. We hypothesize that patients with mucosal appendicitis can be discriminated from those with transmural disease based on specific preoperative clinical and imaging findings. Materials and methods: After IRB approval, all patients who underwent laparoscopic appendectomy at our institution during 2015 were reviewed in the electronic medical record. Patients with mucosal appendicitis were identified and matched 2:1 to a random cohort of nonperforated transmural appendicitis cases. Demographic and clinical data were collected, including history, examination, laboratory, and imaging findings. Preoperative factors associated with mucosal appendicitis were modeled using binomial logistic regression analysis. Results: Of 1153 appendectomies performed during 2015, 103 patients had pathologic diagnosis of mucosal appendicitis. When compared with patients with mucosal infection, leukocytosis >10,000 per microliter led to 5.9 times higher likelihood of transmural pathology (P = 0.000). Noncompressibility on ultrasound was associated with 7.3 times higher likelihood of transmural disease (P = 0.015). Echogenic changes were predictive of transmural appendicitis, conferring 3.9 times the risk (P = 0.007). Presence of free fluid led to 2.3 times the rate of transmural pathology (P = 0.007). Finally, for every millimeter decrease in appendiceal diameter, patients were half as likely to exhibit transmural disease (P = 0.000). Together, these variables can successfully predict presence of mucosal appendicitis on final pathology report at a rate of 82.1%, and explain 60% of the variance in diagnosis of mucosal versus transmural appendicitis (P = 0.000). Conclusions: Mucosal appendicitis remains a controversial pathologic entity, but is not associated with greater complications compared with transmural appendicitis when treated with laparoscopic appendectomy. Transmural disease can be predicted by leukocytosis, noncompressible appendix, presence of free fluid, larger appendiceal diameter and echogenicity.