Unilateral Renal Cystic Disease: A Rare and Benign Renal Pathology

doi:10.21203/rs.3.rs-3178723/v1

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Case Report

Unilateral Renal Cystic Disease: A Rare and Benign Renal Pathology

https://doi.org/10.21203/rs.3.rs-3178723/v1

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Unilateral renal cystic disease (URCD) is an infrequent condition that differs from the more common polycystic kidney disease in terms of patient demographics, clinical presentation, genetic background, and prognosis. This article presents a case of URCD in a young male patient who underwent imaging evaluation for nonspecific loin pain. The imaging findings, including ultrasound and contrast-enhanced computed tomography (CECT), confirmed the diagnosis and ruled out the involvement of other solid organs. With normal renal function and no family history of renal cystic disease, the patient's prognosis was favourable. This case report emphasizes the importance of imaging in distinguishing URCD from other renal pathologies and highlights the need for further studies and guidelines on the management of URCD.

Urology & Nephrology

Unilateral renal cystic disease

ultrasound

computed tomography

loin pain

A wide variety of renal cystic pathologies exist, ranging from the most benign at one end of the spectrum to the more aggressive at the other end [1]. URCD is a rare but recognized category among the batch. Typically, it is manifested by multiple cysts replacing the renal parenchyma in the same fashion as the well-known ADPKD, morphologically and radiologically except for unilaterality [2, 3], as it exclusively affects one kidney.

On occasion, unilateral renal cystic disease is mistakenly diagnosed as a deleterious adult form of polycystic kidney disease. Unlike ADPCKD, URCD is “benign, nonfamilial, nonprogressive, nonencapsulated, and not associated with cysts in other organs’’ [2, 4].

Generally, ADPCKD is bilaterally symmetrical, but in rare instances, it can be unilateral when associated with agenesis of the contralateral kidney in which case it is classified as a separate entity called atypical polycystic kidney disease [5].

In URCD, systemic manifestations such as pancreatic, liver, or splenic cysts, colonic disarticulations, and even cerebral berry aneurysms are lacking, [6].

Patients with APKD present with haematuria, renal failure, and hypertension, while patients with URCD are often asymptomatic or mildly symptomatic and diagnosed incidentally upon radiological investigation [7, 8].

An additional differential diagnosis of URCD worth mentioning is multicystic dysplastic kidney (MCDK) in which case no residual functioning renal tissue is seen between cysts, and the calyces do not opacify with contras. In URCD, the collecting system is continuous with the ureter, in contrast to MCDK, where the ureter is atretic [9].

A 35-year-old male presented with gradual onset mild right loin pain and heaviness. Ultrasound and contrast-enhanced computed tomography (CECT), revealed multiple cysts of various sizes and locations enlarging the right kidney, while the left kidney appeared normal. Further investigations, including laboratory tests and family history assessment, confirmed normal renal function and ruled out any familial or genetic associations with renal cystic disease. The patient remained asymptomatic and showed no progression of cyst size or disease extent over a one-year follow-up period.

Imaging with CECT scan of the abdomen and pelvis demonstrated a markedly enlarged RT kidney approaching 25 cm in the bipolar and 15 cm in side-to-side diameter due to numerous cystic lesions, ranging from a few millimetres to 5 cm in size. The cysts exhibited clear fluid content. No calcification, stone, or solid mass lesion was associated, and no high-density content was detected in the cysts to suggest protein or blood product. The cysts did not enhance in the nephrographic phase, but the remaining enhanced renal tissue between the cysts appeared compressed and displaced peripherally. In the excretory scan, the collecting system was opacified and both kidneys had a simultaneous symmetrical excretory function; calyxes were compressed and stretched around the cysts apart from the focal hydrocalyx due to obstruction of the infundibulum. The patent right ureter was stretched and medially displaced at its upper third by the bulky kidney. No cysts or significant abnormalities were depicted in other abdominal solid organs. A complimentary ultrasound examination of the abdomen confirmed the exact CT findings [Fig. 1–4].

The constellation of the imaging appearance, normal renal function, and negative family history all supported the diagnosis of URCD.

URCD was first described in 1964 as unilateral polycystic kidney disease [10]. Subsequently, the topic was revised over and over until, in 1989, Levine et al. first named the condition unilateral renal cystic disease (URCD), as it has been famed for the time being [1].

Imaging with ultrasound (US) and contrast-enhanced computed tomography (CECT) plays a crucial role in diagnosing and evaluating URCD. They can effectively demonstrate the morphological changes in the affected kidney, including numerous cysts of different sizes and locations replacing the renal parenchyma focally or diffusely. The cysts are typically Bosniak type I and contain clear, low-attenuation fluid (less than 10 HU) []. However, they might have dense and even haemorrhagic contents with superimposed complications. In the long term, cysts might undergo calcification. The affected kidney maintains normal excretory function; thus, the residual renal tissue is compressed and displaced peripherally. The calyxes are stretched and moulded around the cysts, giving a characteristic spider-leg appearance. Often, no further cysts are seen within the confinement of other abdominal solid organs, particularly the liver and biliary system [5].

It is important to note that URCD can be diagnosed at any age, and although most reported cases are in the 3rd and 4th decades of life, URCD has been described in 72 elderly individuals. Paediatric URCD requires careful evaluation to differentiate it from ADPKD, as the latter can initially present as unilateral disease in children and progress to asymmetric bilateral disease over time [3].

Scarce cases of URCD are mentioned in the literature. Salupo et al. [8] reported the youngest typical case of URCD in a 22-year-old female.

Serial US, MRI, and/or CT scans should be recommended, at an appropriate time interval, before a final diagnosis can be made. Alternatively, ADPKD can be excluded clinically with the aid of genetic screening, monitoring of renal function, and/or phenotype screening of family members using US [9].

In terms of treatment and therapeutic options for URCD, there are currently no specific robust, society-based guidelines mentioned in the literature for dealing with URCD. Since URCD is considered an originally nongenetic disorder with a satisfactory prognosis, unlike ADPKD, the management approach is typically conservative. Moreover, an ominous cystic renal neoplasm has been once reported with URCD, which might even be coincidental! [10].

Long-term surveillance is recommended to monitor for any potential malignant transformation of the cysts [8, 10].

Conclusively, URCD should be addressed as a unique disease. Familiarity with such a condition can aid in arriving at an accurate diagnosis and negate the need for undue testing. It also plays a role in reassuring the patient and family. Further research and guidelines are needed to establish standardized approaches for the surveillance and treatment of URCD patients.

ACKNOWLEDGEMENTS

Not applicable

CONFLICT OF INTEREST

None declared.

FUNDING

There are no sources of funding.

ETHICAL APPROVAL

No approval was required.

CONSENT

Written consent was obtained by the patient for his publication.

GUARANTOR

Dr Trefa Salih Hasan, Consultant Radiologist, Department of Radiology, Erbil Teaching Hospital, Erbil, Iraq, Kurdistan, Khanzad Road, code: 44001

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Unilateral Renal Cystic Disease: A Rare and Benign Renal Pathology

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INTRODUCTION

CASE REPORT

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