Unilateral renal cystic disease in adults
Dae Yeon Hwang1,
Curie Ahn1,
Jung Geon Lee1,
Seung Hyup Kim2,
Ha Young Oh3,
Yong Yim Kim1,
E. S. Lee4,
Jin Suk Han1,
Suhnggwon Kim1 and
Jung Sang Lee1
1 Divisions of Nephrology,
2 Radiology and
4 Urology, College of Medicine, Seoul National University Hospital and
3 Division of Nephrology, College of Medicine, Sungkyunkwan University, Seoul, Korea
Correspondence and offprint requests to:
Curie Ahn MD, PhD, Division of Nephrology, Seoul National University Hospital, 28-Yunkun-dong, Chongro-ku, Seoul, 110-744, Korea.
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Abstract
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Unilateral renal cystic disease (URCD) is morphologically indistinguishable from autosomal dominant polycystic kidney disease (ADPKD) except for its unilaterality. Unlike ADPKD, URCD patients show neither a genetic background nor progressive deterioration in renal function; thus, the differential diagnosis of URCD from ADPKD is important. Only a few cases of URCD have been reported. This study reports two cases of URCD in adults together with a literature review. We identified these two cases using abdominal computerized tomography and family screening with renal ultrasonography.
Keywords: autosomal dominant polycystic kidney disease; unilateral renal cystic disease
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Introduction
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Unilateral renal cystic disease (URCD) is a multicystic disease, characterized by cysts of varying sizes localized in a diffusely enlarged kidney without forming a distinct encapsulated mass. Except for its unilateral localization, the gross and histological findings of URCD are indistinguishable from those of autosomal dominant polycystic kidney disease (ADPKD) [1]. However, unlike ADPKD, URCD patients show neither a genetic background nor progressive deterioration in renal function.
Even though the differential diagnosis of URCD from ADPKD is important, especially from the genetic and prognosis standpoint, only a few cases of URCD have been reported. Since an ADPKD clinic was opened at Seoul National University Hospital, Seoul, Korea, 83 ADPKD probands have visited the clinic; among these, two patients (2.4%) with URCD were identified by computerized tomography (CT) and family screening studies. This study reports two cases of URCD in adults, together with literature reviews.
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Cases
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Case 1
A 31-year-old man visited the ADPKD clinic with pain in the right flank. He had been experiencing a mild, lancinating pain in the right flank area for several years. He experienced a single episode of gross haematuria 1 year prior to visiting the clinic; otherwise, no other gastrointestinal, respiratory, cardiovascular or urological symptoms were observed.
Upon physical examination, blood pressure was measured as 120/80 mmHg. A 15x8 cm hard mass with a nodular surface was palpated at the right upper and middle abdomen. No other abnormalities were found. No family illnesses including renal diseases were reported.
The urinalysis was normal with SG 1.015. Other laboratory findings were also within normal limits, including serum creatinine (1.0 mg/dl). Abdominal CT revealed an enlarged right kidney (~18x16x10 cm) filled with variable sized round, well-marginated multiple cysts with no capsule formation (Figure 1
). The cysts were separated by parenchymal bands, which were enhanced with contrast media. Two very small cortical cysts were found in the left kidney. No cysts were detected in other intra-abdominal organs. The echocardiography and colon examination were normal. Renal ultrasound was performed on both of the patients, the parents and his siblings and none of them was observed to have cystic renal disease.

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Fig. 1. Case no. 1.Abdominal CT shows an enlarged right kidney filled with variable sized round, well-marginated multiple cysts with no capsule formation. The cysts were separated with parenchymal bands, which were enhanced with contrast media.
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During the follow-up period of 18 months, the subject maintained a good renal function.
Case 2
A 44-year-old man with mild to moderate left flank pain for 5 months was seen at the clinic. Upon examination, blood pressure was measured as 135/100 mmHg. A 13x8 cm sized mass was palpated at the left flank area. Except for the mass, no other abnormalities were noted. Serum creatinine was 1.1 mg/dl, and urinalysis was normal. An excretory urogram (IVP) showed a normal right kidney and a markedly enlarged left kidney with stretched appearance of the left pelvocaliceal system (Figure 2
). Abdominal CT showed multiple variable sized cysts separated by contrast-enhanced band-like septa in the markedly enlarged (18x11x15 cm) left kidney. Some residual renal parenchyma was seen in the upper and lower pole. The right kidney was entirely normal. Other intra-abdominal organs appeared to be normal except for a very small simple cyst in the liver. The echocardiography and colon examination were normal. His parents were both dead; his father died of liver cirrhosis at the age of 45 years and his mother had died at age 75 years. None of the other family members had a history of any renal diseases including cysts or genetic syndromes. None of his three siblings screened with abdominal USG showed any cysts.

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Fig. 2. Case no. 2.An excretory urogram depicted a markedly enlarged left kidney with stretched appearance of the left pelvocaliceal system. Note that abdominal CT findings are the same as those of case no. 1 except affected side. The right kidney was entirely normal.
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During the course of the follow-up of 15 months, the subject's renal function was well maintained.
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Discussion
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In the late 1970s, several studies reported that URCD might be different from ADPKD [13]. Levine et al. [4] proposed the term `unilateral renal cystic disease (URCD)' as a distinct disease entity in 1989. The clinical importance of URCD is to make a differential diagnosis from ADPKD. As this study shows, URCD has at least three aspects different from ADPKD (i) unilateral localization, (ii) negative family history and (iii) no progression to chronic renal failure.
The pathological findings of URCD are not different from those of ADPKD [2], showing numerous epithelial cell-lined cysts interposed among patches of non-cystic renal parenchyma. However, grossly, those cysts were localized exclusively in one kidney. In earlier studies, the unilaterality was confirmed by examining nephrectomized specimens or autopsy tissues [6,7]. As more imaging techniques improve, it will become easier to confirm the unilateral localization of lesions of URCD. Since CT became popular, the surgical confirmation of URCD is no longer needed if patients have characteristic CT findings in combination with genetic and clinical manifestations [4,5]. The frequency of 2.4% in our patients is higher than that of western countries. This estimation of the frequency might be higher than the actual prevalence of URCD in general Korean populations, as our hospital is a third referral hospital in Korea.
Usually, URCD patients have no cysts in the unaffected kidney or in other intra-abdominal organs. However, two small cortical cysts of 0.7 and 0.5 cm in the unaffected kidney in case 1 and a small liver cyst of 0.7 cm in case 2 were observed. These cysts were very likely to be the simple cysts that are commonly present in many adults. The co-existence of simple renal cysts in the unaffected kidney in URCD has been reported in another study [5]. However, the presence of simple cysts in other organs may be ominous, especially in children. In children, ADPKD may manifest as URCD [8,9]. In some children, careful family history taking and radiological studies of their parents have revealed their parents as having ADPKD [10,11,13]. In others, the initial unilateral disease evolved into an asymmetric bilateral disease in a long-term follow-up period [10,12,13]. Therefore, asymmetric evolution of ADPKD should be excluded either by phenotype screening of family members or by a long period of follow-up.
Besides CT, family screening is an important tool for the diagnosis of URCD. However, most of the previous reported cases took family history only (Table 1
). Phenotypic analysis of family members using renal ultrasound was performed in our study. Both parents and siblings of case 1 showed no cystic diseases. Therefore, it is concluded that URDC is not a hereditary trait. In case 2, although family screening was not complete due to the parents' death, no evidence of familial disease was found either by an intensive history taking or by renal ultrasound of his siblings. Long-term follow-up is necessary because the development of ADPKD by a new mutation might be observed.
This study was limited due to the short duration of the follow-up period to prove non-progressive renal function or new cyst formations in the contralateral kidney. However, the study was expanded to seek extrarenal manifestations: no mitral valve prolapse or colonic diverticulum were found, which are known to be associated with ADPKD [14].
Only a few cases of URCD have been reported. Recently, Curry et al. [5] summarized seven adult URCD cases including one of their patients. Thirteen URCD cases from the present study and previous studies are summarized in Table 1
. None of the family members of these 13 patients were documented as having renal disease. The initial clinical profiles of URCD patients were not very different from those of ADPKD. Ten out of 13 patients were males who were diagnosed between the ages of 3 and 79 years. Among them, hypertension was found in six, flank or abdominal pain in seven, abdominal mass in seven, and gross haematuria in three cases. A renal stone was found in one case and UTI in one case [15,16]. The clinical manifestations of our two cases such as abdominal mass, flank pain and gross haematuria were consistent with other reported cases.
In the literature, several patients who had both possible URCD and neoplastic disease have been reported. Posso et al. [18] and Heyward [19] reported patients with unilateral polycystic kidney and renal cell carcinoma. Cole et al. [20] reported a case of URCD associated with dual adenocarcinomas; Wells et al. [21] reported a case with intra-cystic papillomas. Regrettably, except for the case of Cole et al., no study reported the description of family history; the study by Cole et al. reported a suspicious hereditary renal disease. It might be worthwhile to note that the case reported by Posso et al. might have had multiloculated cystic renal neoplasm; and that by Cole, ADPKD. Although the possibility of misdiagnosis of other cystic renal diseases exists in these cases, the possibility of co-existing renal cell carcinoma in URCD should also be considered.
Besides ADPKD, multilocular cystic renal neoplasms, cystic dysplasia and multiple simple cysts are other categories of cystic diseases. These cystic diseases must also be differentiated from URCD. Multilocular cystic renal neoplasms usually form discrete, encapsulated masses that are well demarcated from the adjacent renal parenchyma [22]. Also, a cystic neoplasm grows slowly and expands to displace normal renal parenchyma and does not contain the islands of enhancing parenchyma on CT, which are found in URCD. A multicystic dysplastic kidney is usually diffusely cystic, severely dysplastic and non-functioning due to ureteropelvic occlusion. It is usually easily distinguished from URCD with sonography, CT and radionuclide studies. The collecting system draining the dysplastic segment is atretic or obstructed and, therefore, is not usually opacified on contrast-enhanced CT, whereas the collecting system in URCD shows only the displacement [23]. Multiple simple cysts may be difficult to distinguish from URCD when confined to one kidney. However, they are not as numerous as in URCD.
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Acknowledgments
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We thank Ms Bina Choi for her excellent secretarial service.
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Received for publication: 13. 1.99
Accepted in revised form: 26. 3.99