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Original Research |
1 Department of Interventional Sonography, University Medical Center, Trnovac
bb, Tuzla, TK 75000, Bosnia and Herzegovina.
2 Department of Dialysis, University Medical Center, Tuzla, Bosnia and
Herzegovina.
3 Department of Urology, General Hospital, Mostar, Bosnia and Herzegovina.
Received July 13, 2007;
accepted after revision November 7, 2007.
Address correspondence to E. Zerem
(zerem{at}inet.ba).
Abstract
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SUBJECTS AND METHODS. Eighty-five patients with 92 simple renal cysts were randomly assigned to two groups in a prospective controlled trial. One group was treated with sonographically guided continuous catheter drainage with negative pressure and the other group with single-session alcohol sclerotherapy. Patient demographics, clinical characteristics, treatment outcome, and complications were analyzed.
RESULTS. The initial volume of the cysts did not differ significantly between the groups, but the final volume was significantly smaller in the continuous drainage group (p = 0.026). During the 24-month follow-up period, 37 (40%) of the cysts disappeared completely: 24 (52%) of the 46 cysts in the drainage group and 13 (28%) of the 46 cysts in the sclerotherapy group (p = 0.033). In the sclerotherapy group, the probability of disappearance of the cysts was highly dependent on cyst size, being less for giant cysts (p = 0.01). Cyst size was not a significant factor in probability of disappearance in the drainage group (p = 0.15). The probability of disappearance of giant cysts (volume > 500 mL) differed significantly between the groups (p = 0.009), but there was no difference in probability of disappearance of moderately large cysts (p = 0.16). Three of 14 patients with giant cysts in the drainage group and 10 of 13 such patients in the sclerotherapy group had recurrences that necessitated additional treatment (p = 0.007). They were successfully treated with continuous catheter drainage.
CONCLUSION. Continuous catheter drainage with negative pressure is more efficient than single-session alcohol sclerotherapy in the management of giant cysts. For moderately large cysts, the two methods have similar results.
Keywords: interventional sonography • percutaneous treatment • randomized study • renal cyst
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Management of simple renal cyst is indicated when the cyst causes symptoms or when rapid growth occurs. Before laparoscopy became available, open surgery was the only therapy for symptomatic renal cysts. Although laparoscopic resection of cysts is less invasive than open surgery, the procedure is expensive and must be performed under general anesthesia [1, 3, 4]. Advances in minimally invasive percutaneous treatment have provided an opportunity to manage these cysts by aspiration of cystic fluid and injection of a sclerosing agent. The percutaneous procedure most frequently performed for symptomatic renal cysts is aspiration with alcohol sclerotherapy [2–6] or, rarely, with another sclerosant [7–10]. Because of frequent relapses, several authors [1, 4, 6, 7, 11, 12] do not recommend percutaneous cyst aspiration or drainage without sclerotherapy.
According to currently available data, percutaneous management of simple renal cysts has not been fully evaluated. We conducted this study to evaluate whether continuous catheter drainage with negative pressure yields better results than single-session alcohol sclerotherapy in the management of symptomatic benign renal cyst.
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Setting
All patients with a symptomatic simple renal cyst who were admitted to our
hospital between April 1998 and March 2005 were considered candidates for the
study.
Inclusion Criteria
Patients were enrolled if they had symptoms and signs caused by a simple
renal cyst confirmed with sonographic or CT examination. In the seven patients
who had bilateral cysts, each cyst was separately documented.
Exclusion Criteria
Exclusion criteria were infectious renal cyst, autosomal dominant
polycystic kidney disease, cystic tumor of the kidney, and coagulopathy. When
there was uncertainty about the relation between the cyst and clinical
symptoms, the possibility of a coexisting pathologic condition was excluded.
The evaluation was made 7 days after the procedure to rule out the adverse
effect of the procedure itself on the clinical status of the patient. Symptoms
that disappeared after the procedure were attributed to the cyst. If symptoms
persisted, patients were included as having had a treatment failure.
Eligible patients were randomly assigned to one of two percutaneous intervention groups: continuous catheter drainage with negative pressure or single-session alcohol sclerotherapy. Sealed envelopes containing the treatment names were used to make the assignments. All patients gave written informed consent, and the study was approved by the local ethics committee.
Intervention
Careful localization of the cyst and proper selection of the entry site
were performed with sonography. The percutaneous drainage technique was a
trocar method with an 8-French multipleside-hole pigtail catheter, which was
introduced into the cyst cavity. The procedure was performed with local
anesthesia; the patients were supine or on their side. No conscious sedation
was applied. As much cystic fluid as possible was aspirated through the
catheter, and the volume of aspirated fluid was recorded. A fluid sample was
sent for bacteriologic and cytologic examinations. To ensure that there was no
communication with the pelvicaliceal system and no leakage through the cyst
wall, we injected diluted contrast medium into the cyst (50% of the aspirated
volume). If those compli cations occurred or if aspiration of contrast
material was incomplete, the procedure was discontinued. After aspiration of
the contrast medium, 5 mL of 2% lidocaine was injected into the cyst for pain
relief.
For single-session alcohol sclerotherapy, 95% alcohol was injected after complete contrast evacuation and was left in the cyst cavity for 2 hours. The alcohol then was evacuated and the catheter removed. If a patient experienced severe pain during alcohol instillation, alcohol was aspirated completely and the catheter removed immediately. The amount of 95% alcohol injected was approximately 30–40% of the aspirated volume of the renal cysts but never exceeded 100 mL, irrespective of the size of the cyst. Smaller injection volumes were used when patients experienced intractable pain during alcohol instillation. The patient moved from the prone to the supine and bilateral decubitus positions at 10-minute intervals to increase contact between all surfaces of the cyst epithelium and the alcohol. To ensure patient safety, we checked vital signs every 15 minutes for 2 hours. The alcohol concentration in the blood was not measured routinely. After the procedure, the patient rested in bed for 2 hours. If the patient was without symptoms, discharge from the hospital was allowed the next day.
For patients in the continuous drainage group, the catheter was secured to the skin after complete evacuation of cystic contents and contrast medium and connected with bag pressure (High-Vac 400 mL OP-System, PJ Dahlhausen) for continuous external drainage, and the patient was sent back to the ward. After the procedure, the patient rested in bed for 2 hours. If the patient was without symp toms, discharge from the hospital was allowed the next day. If after 24 hours there was no catheter output and the cyst cavity was collapsed, the cath eter was removed. If a residual cavity was present, residual loculations of a cyst were managed with catheter repositioning and aspiration under sono graphic guidance. The catheter was left in situ until it stopped producing content. Sonography was repeated every day until the catheter was removed.
Measurements and Follow-Up
The following studies were performed at enrollment, after 7 days, and after
1, 3, 6, 9, 12, 18, and 24 months: clinical examination and laboratory tests
that included urinalysis, serum creatinine level, and coagulation profile.
Loin pain, flank mass, hypertension, and hematuria were documented before
treatment. The subjects were considered to have hypertension on the basis of
data obtained from their histories and according to the present definition of
arterial hypertension, that is, the values of systolic/diastolic blood
pressure were 140/90 mm Hg or greater
[13]. The blood pressure
measurement was performed the day before a procedure and immediately before
local anesthesia was applied. The blood pressure was measured every day over
the first 7 days after the procedure and at the examinations during the
follow-up period. The criterion for blood pressure improvement was a value
less than 140/90 mm Hg. Excretory urography was performed before treatment.
The size of the cysts before treatment and during follow-up examinations was
evaluated with sonography. The volume of the cysts was calculated with an
ellipsoid formula whereby the product of the three orthogonal diameters was
multiplied by 0.523 (volume = height x width x length x
0.523). Cysts with an initial volume more than 500 mL were defined as giant
cysts. CT was performed on 12 patients with the sonographic finding of a
suspicious irregular thickened cyst wall. The diagnosis of nonmalignant cyst
was confirmed with CT for these patients.
A simple renal cyst was defined as an anechoic, unilocular fluid-filled space with imperceptible walls exhibiting posterior enhancement on sonography and a well-demarcated water-atten uation lesion with no contrast enhancement on CT. The goal of treatment was disappearance of the cyst. The cyst was considered to have disappeared if it could no longer be visualized on sonography or the area was replaced by an ill-defined echogenic area or a normal echo pattern. Other important measures for documenting the efficacy of treatment included the appearance and size of the cyst over time, need for additional treatment, length of the hospital stay, and occurrence of complications related to the procedure.
Sonography was performed with a sonographic scanner (Logiq 400 CL, GE Healthcare) and a 3.5-MHz probe. The diameter and echo pattern of the cysts were documented. In addition, both kidneys and the abdominal organs were carefully examined for evidence of residual cysts.
Statistical Analysis
Statistical analyses were performed with MedCalc software (version 8.1.0.0
for Windows, MedCalc). To test the differences between the independent groups
with normal and not normal distribution, independent samples Student's
t test and Mann-Whitney tests, respectively, were done, and to test
the differences in qualitative variables, a Fisher's exact test was done.
Wilcoxon's test for paired samples was done for dependent samples as well as a
log-rank test for the comparison of survival curves. A value of p
< 0.05 was considered significant.
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The median volume of all 92 cysts was 226.5 mL (interquartile range, 103–516 mL) before treatment and 10.5 mL (interquartile range, 0–34 mL) at the last follow-up examination (p < 0.001). Volumes of the cysts before and after treatment in the continuous drainage group (46 cysts) and in the single-session alcohol sclerotherapy group (46 cysts) are shown in Figure 1. The initial volumes of the cysts did not differ significantly between the groups, but the final volume was significantly lower in the continuous drainage group (p = 0.026) (Table 2). Three cysts with residual loculations were managed with catheter repositioning.
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During the 24-month follow-up period, 37 (40%) cysts disappeared completely: 24 (52%) cysts in the continuous drainage group and 13 (28%) cysts in the single-session alcohol sclerotherapy group (p = 0.033) (Table 2). None of the cysts recurred after disappearance. The disappearance probability of the cysts depended highly on cyst size in the single-session sclerotherapy group, the probability being lower for giant cysts (p = 0.01), whereas this factor was not significant in the continuous percutaneous catheter drainage group (p = 0.15).
The disappearance probability for all cysts in Kaplan-Meier analysis differed significantly between the groups. The probabilities of cyst disappearance at 3, 6, 9, 12, 18, and 24 months were 24%, 31%, 40%, 44%, 46%, and 53%, respectively, for the subjects treated with percutaneous catheter drainage and 17%, 20%, 22%, 24%, 26%, and 28% for the subjects treated with single-session sclerotherapy (p = 0.026) (Fig. 2A). The disappearance probability of giant cysts differed significantly (p = 0.009) (Fig. 2B) between the two groups, but there was no difference in disappearance probability of moderately large cysts (p = 0.16) (Fig. 2C).
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The percentage of instilled alcohol varied from 6% to 35% of the initial volume of the cyst. The limitations to reaching the optimal amount of sclerosant were intractable pain in eight patients and the presence of a giant cyst with more than 500 mL of aspirated liquid in 13 patients.
Flank pain was present to variable degrees in all patients before treatment. The flank pain subsided in all patients whether resolution of the cyst was complete or partial. During the follow-up period, pain recurred in 13 patients, and they needed additional treatment. In 12 patients with associated hypertension, blood pressure improved soon after the procedure (< 140/90 mm Hg). We did not change their antihypertensive drugs after the improvement. During the follow-up period, hypertension recurred in four patients. Hematuria disappeared in all eight patients after cyst ablation, and urinalysis showed no microscopic hematuria.
During cyst aspiration, pain was moderate in nine cases but did not necessitate termination of the procedure. During ethanol instillation in the sclerotherapy group, pain was severe in eight cases and moderate in 12 cases. Patients with severe pain received limited treatment. None of them had giant cysts, and they did not differ from those who underwent the full treatment protocol. When the patients with severe pain were excluded from the single-session sclerotherapy group, the treatment results were not significantly different (p = 0.23). Patients with moderate pain underwent the full treatment protocol. Eight patients in the sclerotherapy group had fevers the day after the procedure, and the temperature normalized spontaneously. Symptoms and signs of intoxication occurred in eight patients, headache in seven, and nausea in three patients after single-session alcohol sclerotherapy. Blood alcohol concentration was checked hourly for 5 consecutive hours in eight symptomatic patients. The maximal blood alcohol concentration in those patients was 73–120 mg/dL 3 hours after alcohol instillation. All symptoms and signs disappeared during the first 24 hours after the procedure.
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Treatment with alcohol as the sclerosing agent varies significantly among studies with respect to the time of exposure to ethanol, concentration and volume of ethanol, and number of sclerotherapy sessions. Some authors [6, 11, 14, 15] have used a multiple-session technique with a 12-hour to 2-day interval between sessions. Their results suggest that multiple-session sclerotherapy is better than a single injection of sclerosant for reducing the rate of recurrence of simple renal cysts. Multiple injections, however, are associated with risk of infection, and repeated aspiration and injection procedures cause additional discomfort and inconvenience. In other studies [2, 3, 5, 16, 17], single-session alcohol sclerotherapy was performed with good results. Those authors recommend single-session alcohol sclerotherapy as a sufficient and less risky method. The time of exposure to the sclerosant varies widely (10 minutes–4 hours) among reports [5, 15, 18]. The volume of alcohol injected after aspiration varies from 20% to 50% of cyst volume, the maximal dose being 75–200 mL in various reports [1–5, 15, 16]. We combined the two methods, that is, a single session of continuous exposure to alcohol to make the conditions as comparable as possible with the conditions of continuous percutaneous drainage.
Several authors [1, 4, 6, 7, 11, 12] consider percutaneous cyst aspiration or drainage without sclerotherapy ineffective and believe that the recurrence rate is high because secretions of the epithelial cell lining in renal cysts inhibit obliteration of the cyst. Those authors suggest use of a sclerosing agent to produce further coagulation-induced necrosis of the cyst epithelium and definitively obliterate the cyst.
Our initial hypothesis was that continuous drainage with negative pressure would yield better results than single-session sclerotherapy because the content of the cyst would be evacuated rapidly by drainage with negative pressure, resulting in destruction of the cystic epithelium and obliteration of the cyst cavity. With single-session sclerotherapy the collapsed cyst after aspiration of the content might have many folds with pursed areas inaccessible to alcohol. Thus, all cystic epithelium might not be fully destroyed with injected alcohol, and the cavity that remains after removal of the sclerosant might subsequently fill with secretion from the cyst epithelium. This phenomenon pertains especially to extremely large cysts, that is, those with 500 mL of liquid evacuated and less than 20% of alcohol injected.
Taking into account all cysts, we achieved better results for probability of disappearance of cysts in the continuous drainage group (p = 0.026) (Table 2). In patients with giant cysts, taking into account all parameters, we also achieved better results in the continuous drainage group. Significantly more giant renal cysts in the sclerotherapy group necessitated additional treatment than did those in the continuous drainage group (p = 0.007) (Table 2). When we exclude patients with giant cysts, the results for moderately large cysts are similar for the two groups.
Alcohol can cause complications, including pain, fever, and systemic reactions such as intoxication and shock [7]. The complications are of special concern in the management of large cysts, which require more alcohol for sclerosing. In some cases, overdosage leads to alcohol intoxication.
In our series, pain was relieved in all patients whether resolution of the cyst was complete or partial. Pain relief after partial resolution indicated that the residual cyst did not necessarily necessitate further intervention, as long as pain or other significant symptoms or signs did not recur. In all patients with associated hypertension, blood pressure normalized or improved soon after cyst ablation. During the follow-up period, some patients had recurrent hypertension despite disappearance of the cysts. As in other studies [2, 4] in which results of management of renal cysts were analyzed, we did not analyze hypertension in detail, so the relation between therapy for renal cysts and hypertension in our study remains disputable. Hematuria was present in seven patients and eventually resolved in all. Our results are similar to those of others [2–5, 14, 16–19] who have reported that percutaneous treatment has a high rate of success in reduction of cyst volumes and relief of symptoms and signs related to simple renal cysts.
Treatment of simple renal cysts is indicated when the cysts are large, cause signs and symptoms, or are associated with complications. On the basis of the results of our study, we conclude that percutaneous treatment of benign renal cysts can be performed safely and effectively. Continuous percutaneous catheter drainage with negative pressure was more efficient than single-session alcohol sclerotherapy in the management of giant renal cysts. For moderately large cysts, the two methods had similar results.
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