Renal cysts are a type of lesion that are easily detected by ultrasound in physical examination. The incidence of this disease increases gradually with age[1], ranging from 10–30% in adults to nearly 40% in people over 70 years old. They vary depending on their etiology, location and characteristics. Follow up is usually sufficient for most small simple renal cysts with insignificant clinical symptoms. Some people with peripelvic or parapelvic renal cysts can present with hydronephrosis when they are larger, whereas some aged people with large renal cysts can suffer from flank pain and hematuria if they have a history of trauma[2, 11]. A definitive therapeutic method should be considered when those symptoms exist[12]. Currently, surgery is not recommended as the first-line choice for elderly patients because of its high risk and unbearable complications. Percutaneous sclerotherapy has been developed as a minimally invasive and efficient treatment with a low recurrence rate for cystic lesions in many different organs, including symptomatic renal cysts and even cysts from ADPKD[3, 4, 13]. Many types of sclerosants are used across different medical centers[3, 4]. Owing to its quick action, ethanol at various concentrations is commonly administered in most studies[5, 6]. Some studies have reported that the complications of ethanol are more obvious than those of a novel sclerosing agent, lauromacrogol[8, 14]. With the leakage of ethanol into the surrounding tissue, minor complications, such as pain due to local tissue corrosion, fever and microscopic hematuria, and major complications, such as drowsiness, may occur[4, 6]. Lauromacrogol, a surfactant sclerosing agent, can have strong antiangiogenic effects in vitro and in vivo[15], produce significant regression of the endometrial foci[16], and cause fibrosis in the thyroid or other connective tissue[17]. Therefore, this sclerosant has been adopted in a variety of organs and clinical conditions, even for off-label use[18]. Our former study confirmed that ultrasound-guided percutaneous lauromacrogol injection is an effective treatment for cystic thyroid nodules[10]. As a nonester local anaesthetic, lauromacrogol is painless upon injection and has a low risk for necrosis with extravasation[9]. Some studies have demonstrated that polidocanol is a safe sclerosing agent in the short and long term, regardless of its use as a liquid or foam[19, 20]. It can even be administered in the treatment of patients with autosomal dominant polycystic renal diseases[13]. Our study showed similar results. We found that a single lauromacrogol injection had equal efficacy and better safety than the combination of a 95% ethanol rinse and lauromacrogol injection. The incidence of transient fever in the lauromacrogol alone group was much lower than that in the combined group. The pain associated with a single lauromacrogol injection is minor and easily resolved.
In our study, a higher success rate and a lower complication rate were found in both groups than in those reported in previous studies. There are several factors that may affect these results. In our clinical experience, accurate insertion is the key factor in therapeutic success. Yongue reported that percutaneous sclerotherapy for upper pole cysts is not as effective as that for middle and lower pole cysts because of difficulty in approach and inadequate aspiration[8]. We initially encountered the same obstacle as Yongue did, but later developed an alternative route to insert the needle into the upper pole cysts accurately via the lateral or posterior back approach. It is much easier to avoid dangerous areas such as the upper poles near the spleen and perihilar region through the anterior-back route. In such cases, people do not need to hold their breath strictly because of a lack of respiratory mobility. Second, adequate aspiration and rinse are neccessary to ensure the concentration of the sclerasants and reach therapeutic efficacy. We often rinse the lumen of the cysts several times with saline until the aspirated fluid is clear. Moreover, a rigid 20-gauge puncture needle less than 1 mm in diameter was used instead of a pig-tail catheter or an 18-gauge needle. Even though it is more difficult to aspirate than the thicker one, injury from the insertion with a 20-gauge puncture needle will be less common than before.
In this study, there were still some cases of anatomical failure defined as < 50% reduction, or partial success defined as 50–90% reduction in cyst volume. In addition to the location of the cyst, the initial volume, characteristics of the cyst and the clinical experience of the operator are impact factors of success. During the preliminary period of the study, 2 cases of upper pole aspiration and 1 case of inadequate aspiration failed because of limitations in operative skills. Later, 3 cases of ADPKD were partially reduced because of compression of the surrounding tissue, and 1 case in which the initial volume was greater than 300 mL partially decreased because of the insufficiency of the sclerosant. Accordingly, complications such as pain and intracystic haematuria often occur in patients with therapeutic failure, especially in the combined group. This occurred because of the leakage of ethanol and accidental insertion into other surrounding tissues. Postoperative minor fever and drowsiness usually occur in large renal cysts resulting from rinses with ethanol. In addition, heavy trauma should be avoided after interventional treatment, especially in elderly patients who receive anticoagulant therapy preoperatively.
Our study has several limitations. This was a retrospective study with a relatively small sample size. Some related factors, such as the form of sclerosants and other native characteristics of the cysts, which can influence the efficacy and safety of sclerotherapy, were not analysed sufficiently. This study was also limited in the clinical experience of large renal cyst cases.