In brief
FESS treats diseases of the nose and sinuses through the nostrils, without external incisions in most cases. The aim is to restore ventilation and drainage and to make local treatments more effective; it is considered when its benefits outweigh those of medical treatment alone.
Endoscopic sinus surgery (ESS, often also called FESS) uses endoscopes passed through the nostrils to treat diseases of the nose and paranasal sinuses, without external incisions in most cases. The aim is not simply to “enlarge the sinuses” but to restore ventilation and drainage, remove disease when necessary and create conditions that make post-operative topical treatment more effective.
When it may be indicated
Surgery is considered when the expected benefits outweigh those of medical treatment alone, and after a correct assessment of the disease. Indications include selected chronic rhinosinusitis, nasal polyps, fungal ball, mucocele, odontogenic sinusitis and other conditions for which endoscopic access is appropriate.
In chronic rhinosinusitis, the SNOT-22 questionnaire helps to estimate the expected benefit: with scores above 30, surgery brings a noticeable improvement in more than 3 out of 4 patients, whereas below 20 the average benefit is small. Details and sources (in Italian).
Planning
Nasal endoscopy and CT of the paranasal sinuses are combined with symptoms, clinical history and response to treatment. In surgical candidates, thin-slice CT is essential for anatomical planning; however, the extent of surgery should not be decided on the amount of radiological opacification alone.
How it is done
Using high-definition scopes and dedicated instruments, the surgeon identifies the natural openings of the sinuses, removes obstructions and treats diseased tissue while preserving healthy mucosa as far as possible. The extent can range from limited procedures to advanced surgery of the ethmoid, sphenoid, frontal or maxillary sinuses.
Advanced ESS and navigation
In complex or revision cases, image-guided surgical navigation may be used, which correlates the position of the instruments with the CT images in real time. It is an aid to anatomical orientation and does not replace knowledge of the anatomy and surgical experience.
After surgery
Surgery is one stage of a pathway. Nasal irrigation, topical treatment, endoscopic follow-up and management of the underlying inflammation are decisive for the long-term result. For practical advice see the guide to before and after FESS (in Italian).
Key references
- Clinical Practice Guideline: Surgical Management of Chronic Rhinosinusitis, 2025. PubMed.
Author: Dr Puya Dehgani-Mobaraki. Last reviewed: October 2026.