Abstract: We included four studies (152 participants), with a follow-up duration ranging from three months to 12 months. In two studies patients acted as self-controls, i.e. one side of the nose underwent debridement and the other side did not ('split-nose' studies). The risk of bias in all studies was high, mostly due to the inability to blind the patients to the debridement procedure. Primary outcomes Disease-specific health-related quality of life scores Only one study (58 participants) provided data for disease-specific health-related quality of life. At six months follow-up, lower disease-specific health-related quality of life scores, measured using the Sino-Nasal Outcome Test-22 (SNOT-22, range 0 to 110), were noted in the debridement group but the difference was not statistically significant (9.7 in the debridement group versus 10.3 in the control group, P = 0.47) (low-quality evidence). Disease severity (patient-reported symptom score) Only one study (60 participants) provided data for disease severity measured by visual analogue scale (VAS) score. No significant differences in total symptom score were observed between groups postoperatively (low-quality evidence). Significant adverse effects Significant adverse effects related to the debridement procedure were not reported in any of the included studies, however it is not clear whether data regarding adverse effects were not collected or if none were indeed observed in any of the included studies. Secondary outcomes All four studies assessed thepostoperative endoscopic appearance of the sinonasal cavities using the Lund-Kennedy score (range 0 to 10). A pooled analysis of endoscopic scores in the two non 'split-nose' studies revealed better endoscopic scores in the debridement group, however this was not a statistically significant difference (mean difference -0.31, 95% confidence interval (CI) -1.35 to 0.72; I² = 0%; two studies; 118 participants) (low-quality evidence). A sub-analysis of the adhesion formation component of the endoscopic score was available for all four studies and revealed a significantly lower adhesion rate in the debridement group (risk ratio 0.43, 95% CI 0.28 to 0.68; I² = 29%; four studies; 152 participants). Analysis of the number needed to treat to benefit revealed that for every three patients undergoing debridement, the endoscopic score would be decreased by one point in one patient. For every five patients undergoing debridement adhesion formation would be prevented in one patient. Use of postoperative medical treatment was reported in all studies, all of which recommended nasal douching. Steroids (systemic or nasal) were administered in two studies. However, the data were very limited and heterogeneous, therefore we could not analyse the impact of concomitant postoperative medical treatment. The rate of revision surgery was not reported in any of the included studies, however it is not clear whether these data were not recorded or if there were no revision surgeries in any of the included studies. We are uncertain about the effects of postoperative sinonasal debridement due to high risk of bias in the included studies and the low quality of the evidence. Sinonasal debridement may make little or no difference to disease-specific health-related quality of life or disease severity. Low-quality evidence suggests that postoperative debridement is associated with a significantly lower risk of adhesions at three months follow-up. Whether this has any impact on longer-term outcomes is unknown.

Plain-language summary: We included four studies with a total of 152 adult participants. These studies were conducted in several countries (Norway, the United Kingdom and Canada). All of them compared debridement to no debridement after endoscopic sinus surgery. The minimum follow-up time in the studies ranged from 3 to 12 months. Only one study reported health-related quality of life scores and only one reported disease severity scores. However, all four studies reported scores for the appearance of the sinonasal cavities viewed through an endoscope. Adverse effects of this procedure and rates of revision surgery were not reported in any of these studies. Health-related quality of life and disease severity scores were not significantly different between those patients who underwent debridement and those who did not. All four studies demonstrated better post-surgical endoscopic appearance in the debridement group, although the size of improvement was not statistically significant. A lower rate of intranasal scarring was noted in the patient group that underwent debridement. Nonetheless, the overall evidence for all of these outcomes is of low quality. We identified several problems or potential problems in these studies. The most important was that in each study a different protocol was used for the number of debridement interventions performed per patient and the time interval between each such intervention. In addition, the numbers of patients in the study groups were relatively small. We therefore determined the overall quality of the evidence to be low for all outcomes. The evidence in this review is up to date to May 2018.