Localized Cystic Disease of the Kidney

Transcription

1 Chrystia M. Slywotzky 1 Morton A. Bosniak Received August 1, 2000; accepted after revision October 6, Both authors: Department of Radiology, New York University Medical Center, Tisch HW 202, 560 First Ave., New York, NY Address correspondence to C. M. Slywotzky. AJR 2001;176: X/01/ American Roentgen Ray Society Localized Cystic Disease of the Kidney OBJECTIVE. Localized cystic disease of the kidney is a benign nonsurgical condition. Its imaging and clinical features are characterized and differentiated from autosomal dominant polycystic kidney disease, multilocular cystic nephroma, and cystic neoplasm. MATERIALS AND METHODS. Localized cystic disease was diagnosed in 18 patients on the basis of a review of imaging studies, clinical histories, and pathologic proof in four of the 18 patients. Average age at diagnosis was 54 years (age range, years). Fifteen of the patients (83%) were men. CT was performed on 18 patients, sonography on nine, excretory urography on six, arteriography on four, and MR imaging on two. RESULTS. Localized cystic disease was unilateral in all patients and characterized by multiple cysts of various sizes separated by normal (or atrophic) renal tissue in a conglomerate mass suggestive of cystic neoplasm. In some patients, involvement of the entire kidney, which was suggestive of unilateral autosomal dominant polycystic kidney disease, was seen. No cysts were seen in the contralateral kidney in 14 patients, and only one or two scattered small cysts were present in four patients. Clinical presentations included hematuria, flank pain, palpable abdominal mass, and localized oystic disease as an incidental finding. None of the patients had a family history of autosomal dominant polycystic kidney disease. Ten patients underwent follow-up (follow-up range, 1 12 years); nine patients underwent imaging follow-up and one patient underwent clinical follow-up, which showed stability of disease. Four patients underwent nephrectomy for suspected renal neoplasm. CONCLUSION. Familiarity with localized cystic disease of the kidney and its imaging findings is important to avoid unnecessary surgery and to differentiate the disease from autosomal dominant polycystic kidney disease. C ystic diseases of the kidney encompass a wide spectrum of causes, manifestations, and treatments. Localized cystic disease is an uncommon presentation of renal cystic disease and has been confused with unilateral autosomal dominant polycystic kidney disease, multilocular cystic nephroma, or cystic neoplasm. Relatively few case reports of this condition have been described in the literature [1 11]. Localized cystic disease of the kidney has been referred to by a number of different names, including segmental cystic disease of the kidney when it involves just one portion of one kidney, or unilateral cystic disease of the kidney when it involves all of one kidney. It has also been referred to as unilateral polycystic disease [4]. The latter term may be misleading and should be discarded because this lesion bears no relationship to autosomal dominant polycystic kidney disease, which is a familial disease with a variety of associated conditions [12], none of which are seen in localized cystic disease. Materials and Methods Imaging studies and clinical profiles of 18 patients (collected between 1981 and 1999) were available for study. Data on 12 patients were referred to one of the authors from outside institutions for review and opinion. Four of these referred patients had already undergone nephrectomy at outside institutions for suspected renal neoplasm, and pathologic results were available for review. Six patients were evaluated at our institution. A diagnosis of localized cystic disease was made in these 18 patients on the basis of a characteristic pattern of cysts seen on imaging studies, similar case material described in the literature [1 11], and pathologically proven cases. Follow-up imaging studies were available in nine of the 14 patients who did not undergo surgery. Pathologic findings reviewed included descriptions of the appearance of the gross specimen, extent of involvement of the kidney by cysts, cyst contents, AJR:176, April

2 Slywotzky and Bosniak gross appearance and microscopic composition of cyst walls, microscopic composition of tissue between cysts, and gross and microscopic appearance of the uninvolved portions of the kidney. All patients were examined with CT, nine with sonography, six with excretory urography, two with MR imaging, and four underwent arteriography. CT scans were performed using thin-section (5 mm) technique through the kidneys before and after IV contrast medium administration. Eleven patients underwent this dedicated renal protocol CT on initial examination, as did all nine patients who underwent CT follow-up. In seven patients the initial examination was performed only after IV contrast medium administration because no renal abnormality was suspected. In four of these patients, 10-mm sections were used. MR sequences included half-fourier acquisition single-shot turbo spin echo (HASTE) (TR/TE, infinite/ 62; flip angle, 120 ). Axial two-dimensional spoiled gradient-echo images (fast low-angle shot) (TR range/ TE, /4.4; flip angle, ) were obtained before and after injection of 0.1 mmol/kg of body weight of gadopentetate dimeglumine (Magnevist; Berlex Laboratories, Wayne, NJ). Coronal maximumintensity-projection images were obtained from threedimensional fat-suppressed gradient-echo sequences TABLE 1 Patient No. Summary of Clinical and Radiologic Features Sex Age (yr) Follow-Up (yr) (4.2/1.3; flip angle, 12 ) performed in the arterial phase after injection of gadopentetate dimeglumine. Patient clinical profiles included age at presentation, sex, presence or absence of family history of renal disease, presenting symptoms, years of follow-up, and types of intervention performed. Results The clinical and radiographic features of the study patients are summarized in Table 1. Clinical Features Fifteen patients (83%) were men and three were women. The median age at diagnosis was 50 years (age range, years). On the basis of the imaging findings, 12 patients were initially suspected of having a renal neoplasm, three were suspected of having autosomal dominant polycystic kidney disease, and three patients were diagnosed as having localized cystic disease as an incidental finding. A variety of clinical presentations were seen. Five patients presented with hematuria, four with flank pain, and one with a palpable abdominal mass. Localized cystic disease was seen as an incidental Site Normal Kidney Remaining (%) finding in eight patients. There was no family history of autosomal dominant polycystic kidney disease in the 14 patients for whom this data was available. Four patients underwent nephrectomy with pathologic proof at other institutions, which was obtained for review. Nine patients had follow-up imaging findings available from a 1- to 12-year period (average, 7 years). Lesions in five of the nine patients showed complete radiographic stability and lesions in four patients showed an increase in size in the kidney involved by localized cystic disease. Symptoms of discomfort prompted cyst aspiration in two patients and unroofing of a dominant cyst in one patient. One patient without imaging follow-up is clinically stable 6 years after diagnosis. Four patients with characteristic CT findings were lost to follow-up after initial diagnosis. Pathology Four patients underwent nephrectomy at other institutions for suspected renal neoplasm. In three patients, a conglomerate of cysts of various sizes involved the kidney segmentally. Other Kidney Intervention Clinical Presentation 1 Male 24 6 (Nephrectomy) Upper pole/lower pole 50 Normal Nephrectomy Hematuria 2 Male 25 1 Upper pole 70 Normal Cystic aspiration Incidental finding 3 Male 29 0 Entire kidney 10 Normal None Incidental finding 4 Male 30 6 Entire kidney 50 Normal Cystic aspiration Flank pain 5 Female 34 Nephrectomy Upper pole/mid portion 70 Normal Nephrectomy Hematuria 6 Male 38 4 Upper pole/mid portion 60 Normal None Incidental finding 7 Male 43 3 Upper pole/mid portion 30 Normal Cyst unroofing Flank pain 8 Male 46 8 Mid portion / Lower pole 60 Scattered cysts None Hematuria 9 Male Mid portion / Lower pole 50 Normal None Incidental finding 10 Male 50 0 Entire kidney 5 10 Scattered cysts None Flank pain 11 Male 54 0 Upper pole/mid portion 70 Normal None Flank pain 12 Male 60 6 Entire kidney 20 Scattered cysts None Incidental finding 13 Male Entire kidney 20 Scattered cysts None Palpable mass 14 Male 62 Nephrectomy Upper pole/mid portion 50 Normal Nephrectomy Incidental finding 15 Female Upper pole/mid portion 50 Normal None Hematuria 16 Male 66 0 Entire kidney 10 Atrophic None Incidental finding 17 Male 67 6 Mid portion / 60 Normal None Incidental finding Lower pole 18 [24] Female 83 Nephrectomy Upper pole/mid portion 30 Normal Nephrectomy Hematuria 844 AJR:176, April 2001

3 Localized Cystic Disease of the Kidney Cysts showed no encapsulation and pathology showed cysts of various sizes lined by flattened epithelium. On cross-section, cysts contained clear yellow fluid and smooth walls without evidence of tumor or papillary formation with regions of attenuated normal or atrophic renal tissue separating the cysts. The fourth patient, a 24-year-old man, underwent nephrectomy after 6 years of CT imaging surveillance. Increasing cyst size and development of hyperattenuating cysts, which were probably related to trauma, prompted the decision for surgical intervention because of concern about a potential indolent neoplastic process. In this patient, pathologic evaluation showed conglomerate cysts separated by normal (but attenuated) renal tissue involving the upper and lower poles of the kidney. Walls of the numerous cysts were smooth and glistening, but some exuded thick greenish brown fluid containing hemosiderin consistent with prior hemorrhage. No areas of calcification, induration, or papillary formation were seen. Uninvolved portions of the kidney were normal in all patients. In all four patients, the gross and histopathologic appearances of the cystic areas did not differ from changes seen in autosomal dominant polycystic kidney disease. CT Findings CT findings of all patients were believed to be characteristic of localized cystic disease of the kidney on the basis of the pattern of multiple simple cysts of various sizes separated by normal (or atrophic) renal tissue in a conglomerate mass (Figs. 1 4). Localized cystic disease was unilateral in all patients. The extent of involvement of the affected kidney varied considerably (Table 1). Involvement of the entire kidney was A seen in six patients and, in these patients, localized cystic disease was more likely to be confused with autosomal dominant polycystic kidney disease (Fig. 3). In the remaining 12 patients, only part of the kidney was involved, with a polar predilection in most patients (n = 10) that extended to involve the middle portion of the kidney (Figs. 1, 2, and 4). One patient had upper and lower pole involvement with sparing of the mid portion of the kidney. In one patient only the upper pole was involved. Associated imaging findings included scattered calcifications of cyst walls seen in four patients (Figs. 2C and 2D). It should be noted that hyperattenuating cysts were seen in only one patient and were probably associated with trauma. The contralateral kidney was entirely normal with the exception of an atrophic kidney of uncertain etiology in one patient; and in four patients, who Fig year-old man who presented with microscopic hematuria and lower urinary tract symptoms attributed to prostatitis. A, IV contrast enhanced axial CT scan at level of middle portion of right kidney shows involvement by localized cystic disease. Note symmetric excretion of contrast medium. B, CT scan slightly inferior to A shows multiple simple cysts separated by attenuated renal tissue (arrow). C, CT scan inferior to B has more masslike appearance. D, CT scan of lower pole inferior to C that, if viewed in isolation, could be confused with cystic neoplasm with enhancing septations. Arrow denotes attenuated renal tissue. CT at 8-year follow-up examination (not shown) showed no change in appearance or size of cysts. (Courtesy of Gold R, New York, NY) C D B AJR:176, April

4 Slywotzky and Bosniak were all older than 45 years, one or two scattered, small, simple cysts (1 2 cm) were seen (Fig. 3C). Excretory Urographic and Arteriographic Findings Excretory urography performed in six patients showed mass effect causing distortion of the collecting system. Arteriograms in three patients showed avascular masses with some stretched attenuated vessels, but no evidence of neovascularity and normal vasculature in the uninvolved portions of the kidney. Renal Sonographic Findings Renal sonography was nonspecific showing cystic masses, which appeared complex A Fig year-old man who was incidentally found to have left renal abnormality diagnosed as localized cystic disease. A, CT scan obtained in 1992 shows normally enhancing renal tissue (arrow) separated by simple cysts. B, CT scan corresponding to A obtained 6 years later shows radiographic stability. Uninvolved right kidney remained normal. C, Unenhanced axial CT scan of lower pole of left kidney shows scattered calcifications in cyst walls (solid arrows). Regions of interest (circled) measure 1 10 H. Note incidental small duodenal lipoma (open arrow). D, IV contrast enhanced axial CT scan corresponding to C shows no enhancement in corresponding regions of interest (circled), which continue to measure 1 10 H. Note enhancing attenuated renal tissue. Calcification in the cyst walls was not a prominent feature and was seen in only four cases. (Courtesy of Shah H, Little Rock, AR) because of the intervening attenuated normal parenchyma simulating septae. MR Imaging Findings MR imaging was performed with gadolinium enhancement. In one patient with involvement of the entire right kidney by localized cystic disease (Fig. 3), multiple simple cysts were separated by attenuated, enhancing renal parenchyma. Corresponding MR arteriography showed a slightly attenuated right main renal artery with splaying of the intrarenal vessels around multiple cysts (Fig. 3D). MR imaging provided somewhat more facile visualization of the findings, especially when viewed in the coronal plane. In the second patient evaluated C D with MR imaging, involvement of the kidney was less extensive and findings paralleled those of the corresponding CT. No evidence of enhancing tumor tissue was seen. Discussion Imaging studies often guide clinical management and treatment; therefore, radiologists must be familiar with various renal cystic diseases. It is important to recognize the salient imaging features of localized cystic disease of the kidney to avoid unnecessary surgery (Fig. 4). In addition, patients with localized cystic disease should not be labeled as having a hereditable, progressive renal cystic disease such as autosomal domi- B 846 AJR:176, April 2001

5 Localized Cystic Disease of the Kidney A C Fig year-old man admitted for evaluation of syncopal episodes and occasional right-sided flank pain. A, IV contrast enhanced axial CT scan shows characteristic findings of localized cystic disease. B, T2-weighted half-fourier acquistion single-shot turbo spin-echo (HASTE) axial image corresponding to A shows multiple cysts in right kidney. C, T2-weighted HASTE coronal image shows involvement of entire kidney by localized cystic disease and single small cyst in left kidney. D, MR arteriogram shows slightly attenuated right main renal artery (arrow) with splaying of intrarenal vessels around multiple cysts. Although entire kidney is involved with cysts, there is enough remaining functioning parenchyma so that excretion of contrast medium is present (images not shown). nant polycystic kidney disease, which may have ramifications for clinical manifestations, individual insurability, and genetic counseling. We prefer the term localized cystic disease [1, 13], because this condition is not only unilateral but can also be localized to one or more portions of the kidney. Autosomal dominant polycystic kidney disease is one of the most common genetically transmitted diseases [12]. In humans, at least two chromosomal loci have been implicated in the pathogenesis of autosomal dominant polycystic kidney disease: the PKD1 locus mapped on chromosome 16 [14, 15] and PKD2 locus on chromosome 4 [16]. The renal cysts in autosomal dominant polycystic kidney disease are bilateral and involve both the cortex and the medulla, but autosomal dominant polycystic kidney disease can have an asymmetric onset, particularly in children [17 19]. Therefore, in certain cases, unilateral, nonprogressive localized cystic disease and multiple simple cysts may cause difficulty in differential diagnosis. The only way to resolve this diagnostic problem is to perform long-term follow-up and to obtain a family history, including imaging screening of family members. Autosomal dominant polycystic kidney disease is not limited to renal manifestations with development of renal insufficiency, it is also associated with cysts in other organs (e.g., liver, pancreas) and the occurrence of cerebral aneurysms in a small percentage of affected patients [12]. The presence of hepatic cysts, which can be of various sizes, supports the diagnosis of autosomal dominant polycystic kidney disease occuring in approximately 57% of affected patients [20]. None of these extrarenal manifestations were present in our patients, nor was there any evidence of family history of autosomal dominant polycystic kidney disease in the 14 patients from whom this information could be obtained. Hyperattenuating cysts, which are a common finding in autosomal dominant polycystic kidney disease, were seen in only one patient in our series and, in that patient, a history of significant trauma was elicited. Nephrolithiasis is also a common renal manifestation of autosomal dominant polycystic kidney disease but was not observed in our patients. Involvement of an entire kidney in patients with localized cystic disease may raise the possibility of autosomal dominant polycystic kidney disease (Fig. 3). However, no cysts (or occasionally 1 2 small cysts) (Fig. 3C) may be present in the opposite kidney in patients with localized cystic disease without other manifes- D B AJR:176, April

6 Slywotzky and Bosniak Fig year-old man who was incidentally found to have cystic abnormality of right kidney. CT findings were interpreted as possible cystic neoplasm and patient underwent right nephrectomy. Pathologic evaluation showed findings of localized cystic disease. Although interpreted as possible cystic neoplasm, CT scan viewed with adjacent sections is characteristic of localized cystic disease with multiple simple cysts separated by attenuated enhancing renal tissue (arrow). tations of autosomal dominant polycystic kidney disease. In one patient in our study, the cyst in the uninvolved kidney increased in size from 1 to 3 cm over a 12-year period. The patient was 61 years old at initial presentation and growth of simple cysts would not be unusual in this age group. This patient also showed an increase in cyst size in the kidney involved by localized cystic disease, as did three other patients. The pathogenesis of localized cystic disease is unknown but may represent an acquired condition [13]. As with our cohort of patients, there appears to be a male predilection in cases described in the literature and gross and histopathologic similarity to autosomal dominant polycystic kidney disease in the pathologically proven cases [8]. Localized cystic disease is characterized by replacement of various amounts of one kidney by multiple cysts. These cysts may be scattered diffusely throughout the kidney or involve a more localized portion of the kidney. Therefore, the radiographic findings depend on the number and size of the cysts and the amount of normal renal parenchyma between the cysts. In either form, no distinct encapsulated renal mass is formed. It is this finding that is crucial in distinguishing localized cystic disease from a focal cystic mass such as multilocular cystic nephroma or cystic carcinoma (Fig. 5). CT or MR imaging best reveal the salient imaging characteristics of localized cystic disease. However, the entire lesion must be systematically evaluated on multiple contiguous sequential images. Although a select single axial image of localized cystic disease Fig. 5. CT scan of pathologically proven multilocular cystic renal adenocarcinoma in 59-year-old man shows well-encapsulated mass in middle portion of left kidney with multiple enhancing septae (solid arrow). Mass of cystic locules is encompassed in single large encapsulated mass (open arrow). Enhancing tissue seen in lesion represents tumor tissue. may potentially be confused with cystic neoplasm (Fig. 1D), systematic evaluation of multiple sequential axial images should enable differentiation on the basis of the presence of a continuum of adjacent cysts (Fig. 1) rather than a focal encapsulated loculated mass (Fig. 5). These variably sized cysts are separated by normally enhancing renal parenchyma (Figs. 1 4). The parenchyma may become quite attenuated depending on the size and proximity of the neighboring cysts and can be misinterpreted as enhancing septae (Fig. 1D). However, unlike multilocular cystic nephroma or cystic neoplasm (Fig. 5), localized cystic disease shows no discrete encapsulation and, in fact, often shows other cysts nearby that are clearly separate from the main conglomerate mass of cysts. In the two patients examined with MR imaging, the features of localized cystic disease were somewhat easier to delineate given the ability to display the lesion in multiple planes. However, the diagnosis is also made with meticulous examination of sequential axial CT images. Multidetector CT scanners also provide multiplanar capabilities. Whichever modality is used, it is the understanding and appreciation of the underlying features of localized cystic disease of the kidney that will allow accurate interpretation. A thick fibrous capsule typically encapsulates multilocular cystic nephroma and causes compression of adjacent renal parenchyma [21 23]. This thick capsule encases multiple fluid-filled noncommunicating locules separated by septae. The interlocular septae may contain fibrous tissue or embryonic tissue but are devoid of renal parenchyma. Because of the difficulty of differentiating multilocular cystic nephroma from cystic Wilm s tumor and multicystic renal cell carcinoma on the basis of imaging findings, surgery is indicated in all of these conditions. Localized cystic disease is not associated with renal insufficiency [20]. Interestingly enough, even in patients in whom a large portion of the kidney is replaced by cysts (Fig. 3), contrast medium excretion from the affected kidney on CT or MR imaging appears symmetric to that seen in the normal kidney. These features also differentiate localized cystic disease from a multicystic dysplastic kidney, which can be seen in an adult as a unilateral multicystic disorder. The multicystic dysplastic kidney is not functional, is usually associated with ureteral atresia or agenesis, and typically contains a central core of relatively solid dysplastic tissue with peripheral cysts [20]. This dysplastic core of tissue may enhance after IV contrast medium administration but has a different nephrographic appearance from that of normal renal tissue. The tissue between the cysts in localized cystic disease is normal (or atrophic) renal tissue rather than dysplastic. In summary, localized cystic disease of the kidney (also referred to as segmental cystic or unilateral cystic disease) is an entity that needs to be recognized by radiologists as a benign, nonsurgical condition that requires periodic 848 AJR:176, April 2001

7 Localized Cystic Disease of the Kidney imaging follow-up. Greater awareness of this condition may provide more clues into its pathogenesis, and help prevent its confusion with cystic neoplasm, multilocular cystic nephroma, or autosomal dominant polycystic kidney disease, each of which has a different treatment approach and prognosis. References 1. Cho KJ, Thornbury JR, Bernstein J, Heidelberger KP, Walter JF. Localized cystic disease of the kidney: angiographic pathologic correlation. AJR 1979;132: Levine E, Huntrakoon M. Unilateral renal cystic disease: CT findings. J Comput Assist Tomogr 1989;13: Curry NS, Chung CJ, Gordon B. Unilateral renal cystic disease in an adult. Abdom Imaging 1994;19: Lee JKT, McClennann BL, Kissane JM. Unilateral polycystic kidney disease. AJR 1978;130: Kossow AS, Meek JM. Unilateral adult polycystic kidney disease. J Urol 1982;127: Kutcher R, Sprayregen S, Rosenblatt R, Goldman M. The sonographic appearance of segmental polycystic kidney. J Ultrasound Med 1983;2: Hutchins KR, Mulholland SG, Edson M. Segmental polycystic disease. N Y State J Med 1972; 72: Hwang DY, Ahn C, Lee JG, et al. Unilateral renal cystic disease in adults. Nephrol Dial Transplant 1999;14: Sellers AL, Winfield A, Rosen V. Unilateral polycystic kidney disease. J Urol 1972;107: Kohno A, Yunoki M. Unilateral renal cystic disease. Radiat Med 1999;17: Middlebrook PF, Nizalik E, Schillinger JF. Unilateral renal cystic disease: a case presentation. J Urol 1992;148: Martinez JR, Grantham JJ. Polycystic kidney disease: etiology, pathogenesis, and treatment. Dis Mon 1995;41: Bernstein J. A classification of renal cysts. In: Gardner KD Jr., Bernstein J, Eds. The cystic kidney. Dordrecht, The Netherlands: Kluwer, 1990: Reeders ST, Breuning MH, Corney G, et al. Two genetic markers closely linked to adult polycystic kidney disease on chromosome 16. Br Med J 1986;292: Reeders ST, Breuning PL, Davies K, et al. A highly polymorphic DNA marker linked to adult polycystic kidney disease on chromosome 16. Nature 1985;317: Kimberling WJ, Kumar S, Gabow PA, Kenyon JB, Connoly CJ, Somlo S. Autosomal dominant polycystic kidney disease: localization of the second gene to chromosome 4q13-q23. Genomics 1993;18: Porch P, Noe HN, Stapleton FB. Unilateral presentation of adult-type polycystic kidney disease in children. J Urol 1986;135: Fick-Brosnahan G, Johnson AM, Strain JD, Gabow PA. Renal asymmetry in children with autosomal dominant polycystic kidney disease. Am J Kidney Dis 1999;34: Sheu JN, Chen CH, Tsau YK, Wu TT, Chien CT, Shy SW. Autosomal dominant polycystic kidney disease: an unusual presentation as unilateral renal mass in the infant. Am J Nephrol 1991;11: Levine E, Grantham JJ. Radiology of cystic kidneys. In: Gardner KD JR, Bernstein J, eds. The cystic kidney. Dordrecht, The Netherlands: Kluwer Academic Publishers, 1990; Castillo OA, Boyle ET, Kramer SA. Multilocular cysts : a study of 29 patients and review of literature. Urology 1991;37: Madewell JE, Goldman SM, Davis CJ, Hartman DS, Feigin DS, Lichtenstein JE. Multilocular cystic nephroma: a radiographic pathologic correlation of 58 patients. Radiology 1983;146: Austin RS, Castellino RA. Multilocular cysts of kidney. Urology 1973;1: Beneventano TC, Bosniak MA, Dalinka MK, Lukin RR, Friedman PJ, Thompson WM. Film interpretation session RSNA 68th Scientific association and annual meeting November 1982, Summary of discussion and diagnosis. Radiology 1983;146: AJR:176, April

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