Currently, comparisons of the effects between AS and LD in the treatment of renal cysts were lacking, therefore, we first conducted a meta-analysis on this subject. Statistics in Table 1 show that renal pain would be the primary presenting symptom among patients with renal cysts. In addition to this, renal lump, hypertension and hematuria frequently happened to renal cyst patients as well according to Table 1. Besides, Kim et al. investigated 3,249 patients with renal cysts and they also proved that the occurrence of renal cysts was positively related to hypertension, which has the following characteristics: bilateral distribution, number of cysts no less than two and diameter of cysts larger than 1 cm. Although renal cyst is a benign disease in most cases, complicated variations of that still has the connection of renal cell carcinoma, which may urge patients with renal cysts to be more cautious about the importance of regular follow-up.
At present, treatments such as AS and LD are available to renal cyst patients. Relating to AS, it is time-saving, economical, well tolerated and technique-simplifying so that can be performed under local anesthesia and even in the outpatient rooms in most cases. Our meta-analysis also illustrated that treatment time of AS is significantly shorter than LD. As we all know, AS can be conducted under local anesthesia while LD should be operated with general anesthesia. Thus, LD needs more time for therapy. The high heterogeneity of treatment time may be caused by different ways of records about these data. Some of included studies collected the entire time of hospital stay, nevertheless, the rest of studies only recorded the operation time, which also affected the heterogeneity.
Studies reported by Ali et al. and Monville et al. evaluated the efficiency of ultrasound-guided AS treatment among patients with renal cysts, their results showed that the radiological successful rate were up to 98% and 91.6% respectively meanwhile the complication and recurrence leveled off to zero. However, the rates of radiological success reported by Efesoy et al. and Bas et al. were 63.2% and 60% separately, which were also presented in Table 2. Ethanol contacting the cyst wall causes protein degeneration, cell death as well as inflammatory fibrosis so that patients should keep 5 to 10 minutes at least in each position according to the diverse cyst size and volume. Therefore, the difference among the radiological cure rates might be ascribable to the different treatment procedure, which also would be hard to make a standard therapy. Referring to the research of Dell'Atti at al., polidocanol, whose successful outcome ratio was significantly higher (90% vs. 61%) while failure ratio was significantly lower (3% vs. 33%) than traditional sclerosing agent (ethanol), could be a better choice of AS therapy.
In addition to this, although study reported by Zhong et al. shows no recurrence was observed after AS treatment, in the outcome of our meta-analysis, it was remarkably higher in AS group than LD group in the matter of recurrence. The reason why simple fluid aspiration was ineffective and even promoted the recurrence of cyst could be that the renal cyst epithelium was not destroyed by sclerosing agents completely and adhered to each other, thus the remained cyst wall can still secrete fluid.
In terms of LD therapy, it has the advantage in high rate of cure and low rate of recurrence, and it can be thought as a complete treatment of renal cysts. Nasseh et al. collected the data of renal cyst patients treated with LD in their center and 91.3% patients reached symptomatic and radiological success while only one patient got recurrence, which was consistent with our meta-analysis results. As LD operation preferred to excising the complete cyst including all cyst walls, therefore, the left tissues were out of secreting function, which led to high cure rate as well as low recurrence rate. Hence, LD could be the standard in the management of renal cysts, especially suited for patients failed after AS therapy.
To enhance the efficiency of LD treatment, Lai and colleagues studied the impacts of perirenal pedicled fat tissue wadding technique (PPFTWT) on the recurrence rate during this surgery operation, they found that LD using PPFTWT can decrease the rate of cyst recurrence evidently. Inserting fat tissue into the cavity of the cyst and fixing it prevented the cyst wall from adhering to the residuary cyst wall or surrounding tissue, and contributed to the secretion drainage and absorption of the remaining cyst wall, thus declined the risk of cyst recurrence. Therefore, LD with PPFTWT may be a fitful way in the treatment of renal cysts.
When it comes to complications, our statistics showed there was no significant difference between AS group and LD group, both of which can cause post-treated complications such as fever, infectious, pain, hemorrhage. On account of ethanol as the common sclerosing agents in AS treatment, patients might get alcohol intoxication and lose consciousness even injury femoral nerve due to the rupture of cysts treated by AS. As for LD therapy, vessels damage and subcutaneous emphysema might happen to patients during the process of cyst ablation and establishing pneumoperitoneum.
The limited included studies in our meta-analysis and the heterogeneity of some date were two main limitations of this study. Due to the lack of researches on the comparations between AS and LD, we included six articles merely and the patient selection bias, heterogeneity of cyst diameter and follow up time or difference of operator training/experience could also be limitations. Therefore, further studies are expected to confirm our outcomes. As for the heterogeneity, sensitivity analysis was conducted and delineated in Fig3. In the study of Bas et al., the difference of treatment techniques may contribute to the heterogeneity in symptomatic successful rate. Besides, in terms of complication rate, the researches of Agarwal et al. and Shao et al. only recorded some severe complications such as port infections so that they might omit some information about complications after aspiration treatment, which also brought about the heterogeneity.