Prognostic value of 24-hour cultivation of peritoneal fluid to distinguish complicated from uncomplicated acute appendicitis: a prospective cohort study.

BACKGROUND

The distinction between complicated and uncomplicated acute appendicitis (AA) is important as it guides postoperative antibiotic treatment. A diagnosis based on intraoperative findings is imprecise and standard cultivation of peritoneal fluid is generally time-consuming with little clinical benefit. The aim of this study was to examine if cultivation of peritoneal fluid in acute appendicitis could reliably detect bacteria within 24 h.

METHODS

Patients older than 18 years undergoing laparoscopic appendectomy were prospectively enrolled at two surgical departments after informed consent was obtained. Periappendicular fluid was collected prior to appendectomy and sent for cultivation. Sensitivity, specificity and positive and negative predictive values were calculated with 95% confidence intervals (CIs) using 72-hour cultivation results as the gold standard. Patients with complicated AA as determined by the surgeon, received a three-day course of oral antibiotics. Postoperative infectious complications within 30 days after surgery were registered.

RESULTS

From July 2020 to January 2021, 101 patients were included. The intraoperative diagnosis was complicated AA in 34 cases. Of these patients, six (17.6%) had bacteria cultured within 24 h after surgery, leading to a sensitivity of 60% and a specificity of 100%. The positive and negative predictive values were 1.00 and 0.96, respectively. Seven patients developed a postoperative infection (five superficial wound infections and two intra-abdominal abscess). In all cases with a positive cultivation result, the intraoperative diagnosis was complicated appendicitis and a postoperative course of antibiotics prescribed.

CONCLUSION

Twenty-four-hour cultivation of the peritoneal fluid in acute appendicitis is a valid indicator for peritoneal bacterial contamination. Randomized studies are necessary to determine if this approach is suitable for targeting postoperative antibiotic treatment as a means to prevent overtreatment without increasing the risk of infectious complications.