Benign Renal Cysts Research Articles

Recurrence after percutaneous ethanol ablation of simple hepatic, renal, and splenic cysts: is it true recurrence requiring an additional treatment?

Recurrence after percutaneous ethanol ablation (PEA) of benign hepatic and renal cysts has been common, resulting in re-treatment or additional surgery. However, in recent years, a few cases of spontaneous regression of recurrent cysts following PEA have been experienced, which led to the design of this study to evaluate cyst recurrence after PEA and the necessity of additional treatment. To evaluate whether the initial recurrence after PEA of benign hepatic, renal, and splenic cysts is true recurrence, and to decide whether additional treatment is needed. Thirty-nine benign cysts (21 hepatic, 17 renal, and one splenic) were treated with PEA. PEA was performed with injection of 13-900 ml (40-50% of the volume of aspirated fluid) of absolute ethanol into the cysts. For cysts larger than 100 ml, two or more PEAs were given in one session. Ultrasonography was then performed during a period of 12 months with 1-2-month intervals. Two months after PEA, eight cysts (20.5%) regressed completely; another 31 cysts recurred with decreased size. After 6 months, 10 of the recurrent cysts had regressed spontaneously. Another four recurrent cysts regressed after 8 months, and three regressed after 12 months. Hence, 25 out of 39 (64.1%) cysts regressed within 12 months after PEA. The mean regression time of the 25 recurrent cysts was 6.3 months. All recurrent cysts, including the 14 that were lost to complete follow-up, showed gradual decrease overtime. There were no major complications associated with PEA. Initial relapse of a cyst following PEA does not signify true recurrence, but transient, reactive, or inflammatory fluid collections which eventually disappear within several months, and thus does not necessitate additional treatment.

Simple Renal Cyst Sclerotherapy with Acetic Acid: Our 10-Year Experience

The combination of percutaneous aspiration and sclerotherapy is an effective method for managing benign renal cysts. Many substances have been used as sclerosing agents. Here, we report the long-term outcome after simple renal cyst sclerotherapy with acetic acid. We retrospectively reviewed medical records and identified 60 cases of renal cysts that were managed with percutaneous sclerotherapy from June 1998 to December 2007. All patients were followed up with ultrasonography. We divided the treatment results into three groups: Complete regression (<10%), partial regression (11%-50%), and no response (>51%). The mean volume of the renal cysts on presclerotherapy images was 244 mL (range 12-1216 mL), the mean volume of the aspirate was 233 mL (range 10-1450 mL), and the mean volume of acetic acid administered was 34.6 mL (range 4-100 mL). The median follow-up period was 10 months (range 3-84 months); 46 cases exhibited complete regression (76.7%); 12, partial regression (20.0%); and 2, no response (3.3%). The complications were local pain (nine cases, 15.0%) and nausea and/or vomiting (three cases, 5.0%). The results reveal that acetic acid as a sclerosing agent exhibits a high long-term success rate even at a low dose and produces few complications during the procedure. Thus, we suggest that sclerotherapy with acetic acid offers a more effective management option.

The 10-Year Natural History of Simple Renal Cysts

We previously reported the natural history of renal cysts, with a mean follow-up of 6 years. Here, we extended the follow-up period to 10 years. From January 1993 to August 2006, 61 patients diagnosed with renal cysts were followed for up to 14 years (mean 9.9 years). The sequential changes in renal cyst size were plotted against patient age, and the rate of increase in cyst size per year was calculated for each individual. Those cyst characteristics known to predict aggressiveness were analyzed. The majority of the cysts increased in size and number. The average size increase and the average rate of enlargement in all cysts were 1.6 mm and 3.9% per year, respectively. Several cysts, especially multiloculated cysts, increased rapidly during the first 2 to 3 years, but then the rate of growth tended to decelerate with time. By using univariate analyses, age, laterality and cyst shape were revealed to be significant predictors of aggressiveness. The multivariate analysis revealed that age was the most significant predictor. Renal neoplasms originating from the renal cysts appeared in 2 patients during the follow-up period. The rate of size increase of the neoplasm-bearing cysts was similar to that of the other benign renal cysts in the same age category. The simple renal cysts continued to increase in size over 10 years, and sometimes increased rapidly, especially in younger patients. However, their growth rates appeared to decrease with age. There seems to be no specific pattern observed in the neoplasm-bearing renal cysts.

Hyperattenuating Renal Masses: Etiologies, Pathogenesis, and Imaging Evaluation

Some renal masses have higher attenuation than the surrounding renal parenchyma at computed tomography (CT). Their hyperattenuation is usually the result of proteinaceous fluid or densely packed cells. Most hyperattenuating renal masses are benign hemorrhagic or proteinaceous cysts. However, solid enhancing hyperattenuating renal masses may have malignant as well as benign causes. Possible malignant causes include renal cell carcinoma and lymphoma; benign causes include angiomyolipoma with minimal fat. It is important to identify the cause of a hyperattenuating renal mass so as to avoid unnecessary surgical resection or ablation. CT may be useful for diagnosing benign hyperattenuating renal cysts, hematomas, and vascular anomalies that appear masslike. However, some solid, enhancing, hyperattenuating masses cannot be diagnosed confidently with CT alone: Small (< or = 3-cm-diameter), homogeneously enhancing, hyperattenuating renal masses depicted on CT images may be either benign angiomyolipomas with minimal fat or renal cell carcinomas. Magnetic resonance (MR) imaging may be helpful for differentiating between angiomyolipomas with minimal fat and clear cell renal cell carcinomas; however, differentiation between angiomyolipomas with minimal fat and papillary renal cell carcinomas often is not possible on the basis of MR imaging. In such cases, a percutaneous biopsy may be useful for diagnosis. If the results of MR imaging and percutaneous biopsy are not definitive, surgery is warranted.

Illustrations of abdominal abnormalities on 99mTc tetrofosmin gated cardiac SPECT

99mTc tetrofosmin is predominantly cleared by the hepatobiliary system and its scan is analogous to a cholescintigraphy. The radiopharmaceutical may be localized in the bone marrow. During cardiac acquisition, when the area being viewed includes the lower thorax and abdomen, abnormalities of the liver, gallbladder and kidneys, and the radioactivity in the oesophagus, stomach and bowel, as well as bone marrow uptake, can be depicted by routine raw data cine images. Excluding the intrathoracic abnormalities, these abdominal abnormalities are illustrated in this paper. Retrospectively, we reviewed the raw data cine images from 566 patients. These images were 180 degrees or 360 degrees rotation and showed the abdominal organs and thoracic cage, including the ribs, sternum and spine. We found 234 abnormalities, which were correlated with radiography, laboratory and clinical findings. Intra-abdominal abnormalities included bone marrow visualization, 93 occurrences (39.7%); duodeno-gastric (DG) and entero-gastric (EG) reflux, 47 (20.1%); non-visualization of the gallbladder, including possible causes of cholelithiasis, acute cholecystitis, or cholecystectomy, 31 (13.2%); elevation of the right diaphragm and depression of diaphragm, 30 (12.8%); renal abnormalities, including absent kidney, renal atrophy and cyst, 12 (5.1%); splenomegaly, 10 (4.3%); liver, including hepatomegaly and cirrhosis of the liver, eight (3.4%); and breast attenuation resulting in photopenia in the liver, three (1.2%). (1) The bone marrow uptake of the vertebrae accounts for almost 40% of the abdominal abnormalities, and is usually concordant with anaemia; (2) DG and EG refluxes represent 20% of abdominal abnormalities; they may have a clinical impact and may or may not interfere with SPECT processes and result in artifacts of the inferior wall of the left ventricle; (3) non-visualization of the gallbladder should prompt a search for cholelithiasis; and (4) benign renal cyst or cirrhosis of the liver could also be demonstrated. These coincidental findings may be included in routine cardiac SPECT reports that may have clinical impact because they give the referring physician the chance to pursue further clinical investigation.

Percutaneous Sclerotherapy of Giant Benign Renal Cyst

We report a case of giant benign renal cyst that was treated with percutaneous aspiration and sclerotherapy using 95% alcohol. A 8F catheter was inserted into the cyst under ultrasonographic (US) guidance, and was then left in place to drain the cyst contents (approximately 4 L). A gravity sinogram showed no connections between the cyst and the collecting system. The alcohol treatment involved repeated injections of decreasing amounts of alcohol according with US measurement of cystic volume. The patient's symptoms resolved and cyst drainage stopped after 3 successive days of therapy. Follow-up ultrasound studies showed a 3.5 cm residual cystic wall only.

Advanced Laparoscopy

Laparoscopy will play a significant role in urologic practice in the 21st century. In addition to the standardised procedures of benign nephrectomy, nephroureterectomy, cryptorchidism, adrenalectomy, renal cysts, lymphocele and varicocele, indications and techniques now include laparoscopic radical prostatectomy, pyeloplasty, living donor nephrectomy and retroperitoneal lymph node dissection. Endoscopic suturing and laparoscopic dissection techniques are central to all procedures, together with the management of intra-operative complications. As is the case with open surgery, a variety of technical approaches are emerging from which the individual laparoscopist may choose.

Computed tomography of the kidney

Computed tomography is an extremely accurate method of obtaining more definitive diagnostic information about a renal mass discovered on a urogram. Benign renal cysts are readily distinguished from solid renal neoplasms, and CT is often valuable in characterizing possible juxtarenal masses. The cause of a nonfunctioning kidney(s) on a urogram can often be discerned, and hydronephrosis is easily detected.

Computed Tomography of the Kidney 1

Computed tomography is an extremely accurate method of obtaining more definitive diagnostic information about a renal mass discovered on a urogram. Benign renal cysts are readily distinguished from solid renal neoplasms, and CT is often valuable in characterizing possible juxtarenal masses. The cause of a nonfunctioning kidney(s) on a urogram can often be discerned, and hydronephrosis is easily detected.

Percutaneous sclerotherapy of a giant benign renal cyst with alcohol

We report a case of giant, benign renal cyst that was treated with percutaneous aspiration and sclerotherapy using 95% alcohol. A seven French catheter was inserted into the cyst under ultrasonographic and fluoroscopic guidance, and was then left in place to drain the cyst contents. Approximately 4 l of fluid was drained the first day. The following day, a gravity sinogram was obtained, which showed there were no connections between the cyst and the collecting system. The alcohol treatment involved repeated injections of decreasing amounts of alcohol, with volumes selected in accordance with follow-up sinograms. The patient's symptoms resolved and cyst drainage stopped after 3 successive days of therapy. Totally 600 ml alcohol has given. Follow-up ultrasound (US) and computed tomography (CT) studies showed no recurrent disease; with only a small remnant of the cyst wall. We encountered no major complications during follow-up.

Future Developments and Perspectives in Laparoscopy

Introduction: As urologists head into the new millennium, it has become clear that laparoscopy will play a significant role in successful urologic practice. Issues that are addressed in this article include: (1) What are the new limits? (2) Technological advances. (3) Adequate training. (4) How to technically simplify the laparoscopic procedures? Materials and Methods: To answer the stated questions a review of the literature has been undertaken together with interviews of the leading experts and laparoscopic working groups in urologic laparoscopy. The gathered information has been sumarized and focussed with the aim of presenting the perspectives of laparoscopy in urology. Results and Discussion: Standardized indications for laparoscopic urological surgery are benign nephrectomy, nephroureterectomy, cryptorchidism, adrenalectomy, renal cysts, lymphocele and bilateral or relapsing varicocele. Future indications might include living donor nephrectomy, partial nephrectomy and cyst decortication for adult polycystic kidney disease. Controversy exists about the laparoscopic treatment of malignancies in the urinary tract. Whereas pelvic lymph node dissection – even if performed with drecreasing frequency – is accepted worldwide, retroperitoneal lymphadenectomy for low–stage testis cancer is currently performed only at few centers. The recent breakthrough in uro–oncological laparoscopic surgery has been laparoscopic radical prostatectomy changing our views on the limits of laparoscopic urology. Endoscopic suturing devices (i.e. Endostitch) are further being developed, and a prototype reapproximating micro–clips (VCS stapler) has been used to perform a uretero–ureterostomy laparoscopically in a porcine model. Nevertheless, the ability of endoscopic suturing using the standard equipment has still to be considered as a ‘conditio sine qua non’. Improvements for tissue division and dissection include an electrosurgical snare to perform a partial nephrectomy, the development of a pneumodissector and hydrodissector. Robotics, including the AESOP 3000 and ZEUS represent a glimpse of the future. By positioning the optique in a voice–controlled full range motion mechanic arm, the image on the screen is very steady and the ergonomics of the surgeons is increased significantly. The da Vinci–System, however, is the first system that has translated all visions of telepresence surgery into clinical reality, recently also for laparoscopic radical prostatectomy. Conclusions: The future of laparoscopic urology is a two–tiered approach. On the first tier, the advancement of complex reconstructive and ablative surgery such as laparoscopic prostatectomy or, laparoscopic retroperitoneal node dissection, will be undertaken by referral centers of expertise. It is from these individuals that we will look to in order to separate what is feasible and what is reasonable. The second tier will be focusing on simplifying the procedure for the average urologist. As such, developments such as the pneumodissector, hydrodissection, and hand assistance will bring exstirpative laparoscopy into the realm of more urologists. What is critical is that the urologic community supports both groups of laparoscopists.

CT and MR of Atypical Cystic Renal Masses: Revisiting the Bosniak Classification

Advances in cross-sectional imaging techniques, especially ultrasound, CT, and MRI, have allowed the frequent detection and more detailed characterization of renal cystic masses. Benign renal cortical cysts, the most common renal masses, usually demonstrate classic features on cross-sectional studie

An evaluation of Bosniak's radiological classification of cystic renal masses.

To determine the clinical usefulness of Bosniak's classification of cystic renal masses, the differentiation of which remains difficult despite significant advances in diagnostic imaging. The computed tomography (CT) findings of all histopathologically examined cystic renal masses diagnosed at our institution were analysed retrospectively; 35 patients with cystic renal masses were treated between 1986 and 1998. Tissues surgically removed were examined pathologically and the final diagnosis compared with the preoperative CT category of Bosniak's classification. The histopathological examined showed cystic renal cell carcinoma in 21 patients, a benign renal cyst in 12, haemangiosarcoma in one and transitional cell carcinoma in one. Most of the 35 masses (26, 74%) were found incidentally during evaluation for an unrelated disease or a routine health check. All 11 masses of Bosniak category I were benign and one category II mass was malignant. All 10 masses of category III and 12 of category IV were malignant. Bosniak's classification is useful for differentiating category I, III and IV cystic renal masses. There were too few samples to allow meaningful conclusions to be drawn for category II renal masses. It is critical to differentiate between complicated cysts of category II and III because of the major implications for prognosis and clinical management.

IDIOPATHIC RETROPERITONEAL HEMATOMA MIMICKING CYSTIC TUMOR ASSOCIATED WITH HEMORRHAGIC RENAL CYST

A 54-year-old woman was admitted to the hospital for evaluation of a retroperitoneal cystic mass detected incidentally during a complete followup physical examination for hypertension. CT revealed a 3 3 3 cm. cystic tumor between the inferior vena cava and abdominal aorta, and a 1 3 1 cm. enhanced mass in the left kidney (fig. 1). Magnetic resonance imaging showed that the inferior vena cava and abdominal aorta were deviated laterally by the mass in front of the vertebra, and a high density tumor in the left kidney was found (fig. 2). Angiography demonstrated no feeding arteries to the retroperitoneal mass or ruptured vessels. Preoperative diagnosis was cystic retroperitoneal and left renal tumors. To rule out lymphocele and retroperitoneal hematoma resection of the retroperitoneal mass and left partial nephrectomy were performed. The retroperitoneal mass was adherent to the inferior vena cava, abdominal aorta and vertebra, and had more capsular vessels than expected. Fluid collection of the retroperitoneal mass and left renal mass revealed an old hematoma and hematoma clot, respectively. Histologically, there were features of fibrous scar with fibrin and monocyte infiltration, while the left renal mass had no evidence of malignancy. Final diagnosis was idiopathic retroperitoneal hematoma and benign hemorrhagic renal cyst. No history of gastrointestinal upset, surgery or trauma was noted, and the cause of retroperitoneal hematoma and origin of the bleeding could not be identified. Convalescence was uneventful, although hypertension did not subside. The patient was well without evidence of disease recurrence at 1-year followup.

Urinary NMP22 and renal cell carcinoma

Objectives. To demonstrate the incidence of positive urinary nuclear matrix protein 22 (NMP22) values associated with renal cell carcinoma (RCC) of the kidney. Currently, urinary NMP22 is used to detect recurrent transitional cell carcinoma of the bladder. Methods. From May 1997 to March 1998, urinary NMP22 values were obtained from 65 patients who had undergone either computed tomography scanning of the abdomen or renal ultrasound. Of the 65, 32 presented with solid renal masses. These patients underwent radical or partial nephrectomy; subsequent pathologic examination revealed that 30 had RCC. Two patients had oncocytomas. The remaining 33 patients presented with blunt abdominal trauma or abdominal pain or for follow-up for a urologic problem (a kidney stone or benign renal cyst). These patients had no evidence of renal malignancy on imaging and were used as controls. Results. The urinary NMP22 values of patients with RCC were significantly higher than the values found in the control group (13.69 ± 8.40 U/mL versus 3.03 ± 2.70 U/mL, P <0.0078). Of the 30 patients with RCC, 12 (40%) had positive urinary NMP22 values of 10 U/mL or above. Chi-square analysis revealed a significant difference between the NMP22 values of the two groups ( P <0.005). There were two false-positive NMP22 values in the 35 control patients. Conclusions. Urinary NMP22 values used to detect transitional cell carcinoma in individuals with previously diagnosed bladder cancer should be more broadly evaluated, since elevations have also been found to occur in RCC of the kidney. This finding may result in an increase in the incidental discovery of RCC. Future, more specific, NMP assays may hold promise for the detection of RCC.

Neuroendocrine Differentiation in Renal Cell Carcinoma: Evaluation of Chromogranin A and Neuron-Specific Enolase

Chromogranin A and neuron-specific enolase (NSE) as neuroendocrine markers were evaluated in 200 patients with renal cell carcinoma, and 15 patients with benign renal cysts. Immunoassays of serum levels and immunohistochemical staining of tumour tissue were performed. Serum chromogranin A was elevated in 28 (14%) patients with renal cell carcinoma, but the levels did not differ from those for patients with benign cysts. Serum NSE was elevated in 54 (27%) patients, significantly higher compared with controls (p=0.0002). Serum chromogranin A level was positively correlated to serum creatinine and age, but not to tumour stage or grade. Serum NSE level was positively correlated to tumour stage and grade, but not to serum creatinine or age. Immunohistochemical staining for chromogranin A was positive in 1 of 24 (4%), and for NSE in all 18 (100%) tumours analysed. In a multivariate analysis, tumour stage, grade, and serum NSE, but not chromogranin A, were significant predictors of prognosis.

Identification of the MN/CA9 Protein as a Reliable Diagnostic Biomarker of Clear Cell Carcinoma of the Kidney

The MN/CA9 protein is a tumor-associated antigen that has been shown to have diagnostic utility in identifying cervical dysplasia and carcinoma. MN/CA9 expression is limited to very few normal tissues. We have now extended those observations to further investigate expression of the MN/CA9 protein in histological sections and fine-needle aspiration biopsy smears of normal kidney, benign renal cell lesions, all categories of renal cell carcinomas (clear/granular/spindle cell, chromophilic cell, chromophobic cell, and collecting duct cell RCCs), metastatic RCCs, and non-renal cell clear cell adenocarcinomas. We have found that high levels of MN/CA9 expression is seen in all primary RCCs, cystic RCCs, and metastatic RCCs, with the exception of two cases of the chromophobe cell type, which were MN/CA9 negative. Identical MN/CA9 immunostaining was also observed in the aspiration cytological smears. In contrast, all benign lesions, including pyelonephritis, renal cysts, adenomas, oncocytomas, and normal kidney, did not express the MN/CA9 protein. Thus, we conclude that MN/CA9 protein expression could serve as a valuable adjunct to the cytological and histological diagnosis of benign renal cysts versus cystic RCC, adenoma versus RCC, and oncocytoma versus granular cell RCC. Diffuse membraneous staining of all RCCs (with the exception of chromophobic cell RCC) suggests that MN/CA9 protein expression might have an important clinical utility in the early detection and treatment of RCC. Absence of MN/CA9 expression in non-renal cell clear cell adenocarcinoma also indicates that MN/CA9 protein expression may be used as a differential diagnostic biomarker of metastatic clear cell RCC.

Comparison of the morphology of renal cysts and cystic renal tumors.

Renal tumors appear uncommonly with cystic changes. They may develop due to necrosis though well-formed real cysts are also known. Such lesions may present problems in distinguishing them from benign renal cysts. Conditions leading to cyst formation are not known, however cell proliferation, altered extracellular matrix production and oncoprotein expression have been reported in cystic renal disorders. In the present study, we analysed the morphological features of 23 cystic renal tumors in comparison with 16 benign cysts using immunohistochemical and lectin binding methods. By our knowledge there has not been any piblication on such studies. The cystic renal tumors were represented predominantly in males and the size of the cysts was slightly larger than that of benign cysts. Tumorous cysts shared similar morphological appearance to solitary and multilocular cysts. They all showed strong epithelial membrane antigen reactivity on the luminal surface of the cells indicating distal tubular origin. Cell proliferation and p53 expression proved to be low excluding their role in the formation of the cysts. The amount of extracellular matrix and basement membrane was increased with an elevated type IV collagen and reduced fibronectin content. Polycystic kidney disease is different from tumorous cysts as cell proliferation, p53 oncoprotein expression and the composiition of extracellular matrix proved to be the opposite. As renal cell tumors arise from proximal tubules, neoplastic or metaplastic differentiation toward distal tubular direction seems to be the key even in cyst formation. Altered cell-matrix or cell-cell contact can modulate this transformation providing a basis for further results.

A Rare Case of Bilateral Multilocular Renal Cysts

Several names have been used to describe a rare multiloculated cystic lesion in the kidney, including benign multilocular cyst, multilocular cystic nephroma, cystic nephroma and others. The abundance of names is partially attributable to an incomplete understanding of the etiology and natural history of this condition. Most authorities believe that this lesion is part of a spectrum of renal cystic disorders with multilocular cyst and cystic Wilms tumor representing the 2 extremes. Whatever the etiology, multilocular cysts have a typical radiographic appearance, are almost uniformly unilateral and are treated with curative nephrectomy. We report a unique case of bilateral multilocular renal cysts treated with bilateral partial nephrectomy. CASE REPORT A 15-month-old Hispanic boy presented with a 3-month history of progressively enlarging bilateral flank masses, and nausea, vomiting and anorexia 1 week in duration. There was no other significant medical history. Physical examination revealed blood pressure of 100/60 mm. Hg and abdominal examination demonstrated bilateral 12 to 14 cm., nontender, nonfixed, firm flank masses. Serum electrolytes, urea nitrogen, creatinine, hemoglobin and urinalysis were normal. Abdominal ultrasound and computerized tomography showed 10 X 12 cm. cystic renal masses with multiple septa (fig. 1). A rim of normal appearing renal parenchyma (right side greater than left side) was displaced inferiorly and medially. 3-Mercaptoacetyltriglycine nuclear renal scan revealed that 80% of renal function was by the right kidney. Abdominal exploration was planned but moderate hypertension developed, which was controlled with oral calcium channel blockers. Subsequently exploration was performed through a transperitoneal midline incision. The left renal mass was approached first, revealing a firm mobile cystic renal mass contiguous with the inferior pole of normal appearing renal tissue. Because of the benign appearance of this mass and bilateral involvement, a nephron sparing procedure was performed involving partial nephrectomy with renal reconstruction. The mass was completely excised en bloc (fig. 2). However, the dilated renal pelvis was opened to extrude the inferior aspect of the mass, which had herniated into the collecting system. Frozen section was consistent with a multilocular renal cyst without evidence of malignancy. Exploration of the right side revealed similar fmdings and an identical procedure was performed. Postoperatively the patient recovered well. He is currently asymptomatic and thriving, and hypertension has completely resolved. Followup renal scan and ultrasound 6 months postoperatively demonstrated excellent function of both remaining renal units with no evidence of any recurrent cystic lesions. The final pathological diagnosis was consistent with bilateral benign multilocular renal cysts.

Usefulness of color Doppler flow imaging in differential diagnosis of multilocular cystic lesions of the kidney.

Color Doppler flow imaging was carried out in 10 multilocular cystic lesions of the kidney. These consisted of three renal cell carcinomas, three hemorrhagic renal cysts, one benign multilocular cystic nephroma, two infected renal cysts, and one benign multilocular renal cyst secondary to von Hippel-Lindau disease. In the patients with renal cell carcinoma, color signals were obtained at the septum and in the solid component within the lesions. A pulsatile wave with a large maximum flow velocity and a high PI value was obtained in two of them. In one of the patients with hemorrhagic renal cysts, color signals were obtained at the region of the septum. In the other benign lesions, however, color signals were obtained only at the peripheral margin, and the flow waveform in these cases was identical to the waveforms found in the interlobar arteries. This study suggested that color display in the lesion well reflects its vascularity in patients with multilocular cystic renal diseases and that measurement of the systolic maximum flow velocity by fast Fourier transform analysis is useful for the differential diagnosis of malignant versus benign lesions.