Pre-appendectomy hyponatremia is associated with increased rates of complicated appendicitis.

Background: Acute appendicitis is one of the most common surgical emergencies worldwide. Preoperative assessment of the risk of complicated appendicitis may aid in treatment planning. We sought to investigate the association between pre-appendectomy hyponatremia and diagnosis of complicated appendicitis. Methods: The TriNetX platform, a federated health research network that aggregates de-identified electronic health record data of over 90 million patients across the United States, was queried for patients who underwent appendectomy starting January 2019 and who had at least one sodium value from the preoperative period. The study population was stratified into three age groups: pediatric (age < 18), adult (age 18-64), and older adult (age ≥ 65). These groups were subdivided into patients with preoperative hyponatremia (<135 mmol/L) and normonatremia (135-145 mmol/L). Results: Among the 61,245 patients who met inclusion criteria, 17,546 were included for analysis following propensity score matching. The odds of complicated appendicitis were highest in pediatric patients (age < 18) with pre-appendectomy hyponatremia (odds ratio OR = 2.91, 95 % CI 2.53, 3.35). Patients age 18-64 and aged ≥ 65 with preoperative hyponatremia also demonstrated increased odds of a complicated appendicitis diagnosis, but to a lesser extent (OR = 2.11, 95 % CI 1.92, 2.32 (OR = 1.49, 95 % CI 1.25, 1.77, respectively). Conclusions: In a large analysis of matched patients with acute appendicitis, we found an association between immediate preoperative hyponatremia and complicated appendicitis. Future studies are indicated to further evaluate the role of hyponatremia as a potential diagnostic marker for complicated appendicitis in all age groups. Key message: This study suggests a role of hyponatremia as one of multiple variables to incorporate into future clinical decision tools for complicated acute appendicitis.