Percutaneous Drainage with Injection of Ethanol as the Sclerosing Agent for Treatment of Simple Kidney Cysts: A New Modification

Introduction

Simple kidney cysts are common findings in routine medical evaluations, with acquired origin. This type of cyst usually arises from the kidney parenchyma and rarely from transitional urothelium. ¹ Simple kidney cysts are mostly seen in normal kidneys and their prevalence increases with aging, occurring in 29% of >40 and 37% of >60-year-old individuals. ^2,3 Other studies reported the occurrence rate of 50% in adults. ⁴

The Bosniak classification according to CT scan criteria is used for differentiating benign cysts (type I–II) from malignant ones (type III–IV). ⁵

Most of these simple cysts are asymptomatic, but flank pain, hematuria, infection, pyelocaliceal junction obstruction, and hypertension can occur in some patients. ⁶ Diagnosis of a simple cyst by ultrasonography has an accuracy rate of 95%–98%. In this modality, simple cysts are fluid-filled sacs with thin walls and no internal echogenic particles. ⁷

One of the treatment methods is percutaneous aspiration with or without injection of a sclerosing agent. In comparison with the other options, several advantages have been shown with percutaneous treatment such as minimal adverse events and possibility of outpatient management without the need for anesthesia, as well as minor postprocedure pain and symptoms. Risk of recurrence, sepsis, anaphylactic shock, and in some cases, arteriovenous fistula have been reported as possible side effects of percutaneous aspiration. ^{6 –8}

Based on a currently common approach, after drainage and volume calculation, the sclerosing agent is drained 20 minutes after instillation and then the catheter is removed.

Considering the high prevalence of simple kidney cysts and effectiveness of injecting sclerosing agents, in addition to the fact that no previous study has been conducted on our proposed modification, we performed a study using percutaneous aspiration, insertion of a drainage catheter, injection of 95% ethanol as the sclerosing agent, and immediate removal of the catheter, keeping the sclerosing agent in the cysts. We altered the conventional method by keeping the ethanol in the cysts for a longer time to increase the exposure of cyst epithelium to the sclerosing agent. Long-term follow-up was conducted to assess sonographic findings.

Materials and Methods

This study had a cross-sectional retrospective design. Twenty-eight patients with symptomatic (painful) Bosniak type I kidney cysts larger than 6 cm in biggest diameter were enrolled in this study with informed consent and followed for a minimum of 1 year. Preoperative imaging evaluation was done using CT scanning. Parapelvic cysts were not included. Exclusion criteria were as follows: active urinary tract infection, unresolved impaired coagulation, history of allergic reaction to sclerosing agents, pre-existing malignancy alongside the kidney cyst, and cysts diagnosed as Bosniak class II or more.

Information on age, gender, cyst's location and volume, creatinine (Cr) level, and cytology of aspirated fluid from the cyst and patients' follow-up data regarding recurrence, clinical manifestation, and radiological findings were recorded. The long-term success rate follow-up was conducted using ultrasound.

Patient's data on treatment were extracted from admission forms and following control sonography in subsequent visits. All the patients had recorded complete blood count, blood urea nitrogen, and Cr results from their admission time.

In this method, patients were injected with 2% lidocaine as the local anesthetic in the prone position, and none of the patients were under general anesthesia. After sterilizing the insertion area, the precise location of the cyst was determined using ultrasound guidance. An 18-gauge surgical needle was inserted into the cyst and a guidewire was placed into the cyst. After removal of the needle, an 8F single J drainage catheter was inserted into the cyst. It was fixed in place after confirming the proper location. The cyst fluid was aspirated and a sample was taken for urine cytology and analyzing the Cr level.

After the first aspiration, the catheter was left open in place and the patient was transferred to the ward. After 24 hours, during which we expected some additional drainage by positional changes, the second aspiration of fluid was performed and then 95% ethanol was injected. The volume of injected alcohol was equivalent to one-quarter of the total evacuated fluid volume from the cyst. Finally, the catheter was taken out immediately after ethanol injection. Patients were visited at least once during the first 7–10 days and evaluated for possible adverse events if they had related clinical manifestations. Then, they were followed in two sessions after the procedure by ultrasonography (at the end of the 6th month and 12th month) regarding recurrence of the cyst and probable adverse effects of operation. One of three academic radiologists did the ultrasound follow-up evaluations. We did not apply randomization or blindness among them. The data of this follow-up were extracted from clinical documentation.

No serious intraoperative complications were observed. The only postoperative complication was more or less burning flank pain during the first days, which was rendered tolerable by opioid analgesics. No excessive bleeding or infection was recorded.

Results

In this study, 28 patients with symptomatic simple kidney cysts (Bosniak type I) were enrolled.

The mean age of the population was 56.82 ± 14.80 years with a median of 61. Minimum and maximum age was 27 and 80 years, respectively. In 15 patients (53.6%), the cyst was located in the right kidney and, in 13 patients (46.4%), in the left kidney. In 9 patients (32.1), the upper pole, in 7 patients the central region, and in 12 patients, the lower pole of the kidney was involved.

The estimated cyst volume before aspiration was 389.64 ± 341.46 mL and volume of the aspirated cyst was 411.07 ± 287.99 mL. Mean Cr level of patient's blood sample was 1.07 ± 0.20 mg/dL and aspirated fluid was 1.13 ± 0.62 mg/dL. In all 28 patients, only one case (3.6%) had positive urine cytology, which was evaluated and followed accordingly. Mortality occurred only in one case (3.6%) due to myocardial infarction 7 months after treatment for the cyst. Recurrence after the follow-up period was observed only in five patients (17.9%).

Patients were completely relieved of pain in all cases, although many patients complained of early postinjection increase in pain severity. This pain increase took a few days to subside.

Patients were followed for 14.25 ± 7.55 months with a median of 12 months. The effectiveness of this method was defined as a minimum shrinkage of 3 cm compared with the primary dimension and the absence of pain.

Discussion

The main cornerstone of simple cyst treatment is based on controlling the clinical symptoms and preventing further complications, including hemorrhage, infection, and compressing effects of the cyst on the adjacent parenchyma and collecting system.

In 1989, Holmberg and Hietala introduced a novel method, which included insertion of a needle from the flank skin into the cyst under regional anesthesia, aspiration of cyst content, and then injection of bismuth phosphate as the sclerosing agent. ⁹ Numerous substances have been tried as sclerosing agents for the purpose of degrading kidney cysts, including glucose, phenol, bleomycin, lipidol, povidone–iodine, minocycline, tetracycline, or acetic acid. ^{10 –13}

Despite the short-term success of this approach, its main obstacle is a high recurrence rate (around 54%). In addition, injecting the sclerosing agent may increase the risk of obstruction and narrowing of the adjacent collecting system, which results in limited usage of this method for parapelvic cysts. ¹⁴ However, in many centers, one treatment option for symptomatic simple kidney cysts remains—aspiration with or without injection of a sclerosing agent. In addition, some researchers have tried to reduce the risk of recurrence by increased contact of sclerosing agents with inner cyst walls.

Paananen and colleagues performed one-time sclerotherapy on 32 patients. In 22 of them, the cyst disappeared completely, and in 81%, symptoms were decreased. ¹⁵

Fontana and colleagues applied the aforementioned technique in 72 patients and injected 95% ethanol three times after the initial aspiration. Patients were followed for 48 months; 68 patients showed no signs of recurrence on ultrasound imaging. ¹⁰ The rationale supporting repeated injections in their study is the same that made us leave the injected amount of alcohol inside the cyst, giving further chance for the entire epithelium to be exposed to the agent to achieve further efficacy and nonviability of more epithelial cells.

In the study by Gasparini and colleagues, 14 patients with symptomatic kidney cysts underwent multiple sclerotherapy sessions, 8 times in 5 days. These patients were asymptomatic for at least a year. ¹⁶ Özgür and colleagues suggested that after injecting ethanol into the cyst, aspiration can be performed 20 minutes later. ¹⁷

The most similar study to this study was conducted by Falci-Júnior and colleagues, which was performed on 30 patients with symptomatic simple renal cysts. Their method included puncturing the cysts under ultrasound guidance and then injecting 99.5% ethanol for 6 hours. The main differences between their method and the one used in this study were the duration of keeping the sclerosing agent in the cyst and the volume of the sclerosing agent (one-third of the aspirated fluid from the cyst in Falci-Júnior's study and one-quarter in this study). Patients were followed for a 6-month period, and all patients showed a reduction in the size of the cyst (17 patients showed total remission, 10 patients 90% decrease, and 1 patient 50% decrease), supporting single-session percutaneous sclerotherapy for the treatment of simple kidney cysts. ¹⁸

In our study, we tended to keep a draining catheter in the cysts after initial drainage of the cyst fluid for 24 hours to drain as much fluid as possible. Then, we inserted 95% ethanol and immediately removed the catheter, leaving ethanol inside. Therefore, longer exposure of cyst epithelium to the sclerosing agent can potentially reduce the risk of cyst recurrence.

Logically, longer exposure to the sclerosing agent seems to be related to better results in a given time frame. The origin of the fluid inside the cyst is known to be from the intracystic epithelium itself. Therefore, on a theoretical basis, the recurrence rate of cysts is directly associated with the residual epithelium in the cysts.

Percutaneous resection is a rather new approach to symptomatic simple kidney cysts. Gelet and colleagues reported treating six cases of simple kidney cysts using percutaneous resection. Further follow-up showed no signs of cyst recurrence. ¹⁹

Plas and Hübner used this method in treatment of 10 simple kidney cysts. In a 46-month follow-up, all the patients were asymptomatic. Relapse did not occur in half of the patients, 20% had residual cysts, and 30% showed signs of cysts in other parts of the kidney. ²⁰ This seems to be a potentially good technique and necessitates further evaluations for a better concept of efficacy, availability, and complications.

In the present study, to achieve maximum exposure, the injected sclerosing agent was as much as a quarter of the fluid removed from the cyst. Ethanol remained in the cyst, destroying the cyst's epithelium with no penetration into the kidney's parenchyma.

We admitted all of the patients for 24 hours and discharged them in at least 3 hours after ethanol injection and catheter removal. Patient hospitalization can be limited for many—if not all—of the patients to decrease total cost and increase patient satisfaction and ease.

Short hospitalization, easy recovery after the procedure, and few complications are among the beneficial aspects of this method. In addition, unlike laparoscopy, this procedure does not require multiple incisions to insert trocars. This can avoid extensive tissue dissection. Finally, this method does not have the technical difficulties of laparoscopy as the urologist is fully familiar with the tools used during the procedure.

Conclusions

Further increase in exposure time of the cyst epithelium to the sclerosing agent was the basic idea of this study to achieve better results in terms of kidney cyst treatment and recurrence. According to our findings, this procedure is an effective, safe, and minimally invasive approach to treat simple kidney cysts. Hospital admission may be adjusted to the patient's condition and omitted for many of the patients, although we admitted all of our patients.