Abstract: We found four small studies that met the inclusion criteria. These studies enrolled 275 patients with 282 hydroceles. Participants were randomised to aspiration and sclerotherapy (155 patients with 159 hydroceles) and surgery (120 patients with 123 hydroceles). All studies were assessed as having low or unclear risk of bias for selection bias, detection bias, attrition bias and selective reporting bias. Blinding was not possible for participants and investigators based on the type of interventions. Blinding for statisticians was not reported in any of included studies. There were no significant difference in clinical cure between the two groups (3 studies, 215 participants: RR 0.45, 95% CI 0.18 to 1.10), however there was significant heterogeneity (I² = 95%). On further investigation one study contributed all of the heterogeneity. This could be due to the agent used or perhaps due to the fact that this is a much older study than the other two studies included in this analysis. When this study was removed from the analysis the heterogeneity was 0% and the result was significant (in favour of surgery) (2 studies, 136 participants: RR 0.74; 95% CI 0.64 to 0.85).There was a significant increase in recurrence in those who received sclerotherapy compared with surgery (3 studies, 196 participants: RR 9.37, 95% CI 1.83 to 48.4). One study reported a non-significant decrease in fever in the sclerotherapy group (60 participants: RR 0.25, 95% CI 0.06 to 1.08). There was an increased number of infections in the surgery group however this increase was not statistically significant (4 studies, 275 participants): RR 0.31, 95% CI 0.09 to 1.05; I² = 0%). Three studies reported the frequency of pain in the surgery group was higher than aspiration and sclerotherapy group but because of different measurement tools applied in these studies, we could not pool the results. Radiological cure was not reported in any of the included studies. There was no significant difference in haematoma formation between the two groups (3 studies, 189 participants: RR 0.57, 95% CI 0.17 to 1.90; I² = 0%). Only one study reported patient satisfaction at three and six months; there was no significant difference between the two groups. Postoperative complications as well as cost and time to work resumption were less in the aspiration and sclerotherapy group; however the recurrence rate was higher. The cure rate in short-term follow-up was similar between the groups, however there is significant uncertainty in this result due to the high heterogeneity. There is a great need for further methodologically rigorous RCTs that assess the effectiveness of different type of sclerosant agents, sclerosing solution concentration and injection volume for the treatment of hydrocoeles. It is important that the RCTs have sufficiently large sample size and long follow-up period. Studies should evaluate clinical outcomes such as pain, recurrence, satisfaction, complications and cure using validated instruments. The protocols for all studies should be registered in clinical trial registries and the reports of these studies should conform with international guidelines of trial reporting such as CONSORT. Cost-effectiveness studies should also be undertaken.

Plain-language summary: The aim of this review is to compare these two types of treatment. We found four small studies were identified after an extensive literature search. Due to limited information about the design of the studies, and the small number of patients enrolled, the results should be interpreted with caution. Meta-analysis showed lower rates of recurrence in the surgery group, however there was insufficient evidence to draw a strong conclusion. Postoperative complications such as infection and fever, as well as cost and time to work resumption were less in the aspiration and sclerotherapy group; however the recurrence rate was higher. Cure at short-term follow-up was similar between the groups, however there is significant uncertainty in this result which may be as a result of the age of one of the studies and the different agent used compared to the other studies.