Acute appendicitis is the most common abdominal emergency, with a lifetime risk of around 8%. Appendicitis can present as uncomplicated or complicated (gangrene or perforation with or without an abscess). Perforation is found in 13-20% of patients.
For many decades, open appendectomy was the standard treatment for appendicitis. The advent of laparoscopic surgery changed the approach, but appendectomy continued to be the standard treatment. However, in recent decades, several studies have suggested that antibiotic treatment could be feasible to treat uncomplicated appendicitis.
Rationale for NOM
Treating appendicitis with antibiotics alone is not a new concept, as it was shown to be feasible in trials in the 1950s (Coldrey E, Br Med J, 1956) and in reports in a military setting. Gurin reported an 84% success of antibiotic treatment in 252 ship passengers with suspected appendicitis (Gurin et al., Vestn Khir Im II Grek, 1992)
Principles of NOM
Most treatment regimes include an initial course of intravenous antibiotics for 1-3 days followed by oral antibiotics for 7 days. The antibiotics used vary depending on the protocol, and include cephalosporins, ertapenem, amoxicillin with beta-lactam inhibitor, etc.
The first days of treatment usually take place in hospital to monitor the patient and perform a rescue appendectomy in case of clinical deterioration.
The length of the antibiotic treatment may be reduced over the next few years, with cessation of the therapy 1-2 days after clinical improvement.
A systematic review of the literature (Poon et al. World Journal of Emergency Surgery 2017) demonstrated the higher efficacy of appendectomy compared to NOM in terms of treatment efficacy at the 1-year follow-up and total hospital stay upon first admission. On the other hand, NOM is comparable to appendectomy in terms of complications. Sick leave was significantly shorter in the NOM group compared to appendectomy with a mean difference of 3.37 days.
The Consensus Statement of the 3rd World Congress of the World Society of Emergency Surgery (Jerusalem, Israel, 2015) stated that NOM could be successful in selected patients with uncomplicated appendicitis who accept a 38% risk of recurrence.
The NOTA study (Saverio SD et al, Ann Surg, 2014) suggested an efficacy of 83% at the two-year follow-up. The initial results of the APPAC RCT showed that 5.8% of patients in the NOM group underwent appendectomy during the initial hospitalization, and there was a global 27.3% of failure. The five-year follow-up of the APPAC RCT (Antibiotic Therapy for Uncomplicated Acute Appendicitis) showed that 39.1% of NOM patients ultimately underwent an appendectomy after the 5-year follow-up, with 70% of them having recurrent appendicitis within the first year from the initial presentation. (Salminen P et al, JAMA, 2018).
As regards the cost-effectiveness of NOM vs laparoscopic surgery, a paper by We et al. (Surgery 2015) reported a decrease by $1865 in favor of NOM.
Risk factors for failure
Fever at initial presentation, high serum C reactive protein levels and intraluminal fecalith are reported by several authors as risk factors for failure of NOM.
Cons of NOM
The main criticism for NOM is the risk of recurrent disease (as high as 39.1%). Other reported cons are the lack of a definitive histology when appendiceal tumors have been reported in less than 1% of the appendectomy specimens. However, it should be considered in patients older than 40: in these cases, a colonoscopy is recommended.
Another disadvantage of NOM may be the rise in the use of antibiotics, which might increase antibiotic resistance and lead to a higher burden of Clostridium difficile infections.
NOM may be useful in the treatment of uncomplicated acute appendicitis in selected patients who accept the high risk of recurrence.