Localized renal cystic disease.

Localized renal cystic disease (LRCD) is a rare benign non-hereditary, non-progressive condition which must be differentiated from other renal cystic diseases. Familiarity with this condition and its characteristic imaging features avoids unnecessary surgical intervention. We report a case of LRCD in a 40-year-old male who presented with left loin pain. Computed tomography demonstrated a cluster of simple cysts in the lower pole of the left kidney with normal right kidney and other organs. Diagnosis of LRCD was made on typical imaging characteristics and absence of family history of cystic renal disease.

INTRODUCTION

Localized renal cystic disease (LRCD) is a rare non-hereditary, non-progressive benign condition where multiple cysts involve part or whole of one kidney with no cysts in the contralateral kidney or other organs. It is usually asymptomatic and may be discovered incidentally on imaging. The main significance of this condition is that it must be differentiated from other cystic diseases of kidney like autosomal dominant polycystic kidney disease, multicystic dysplastic kidney and multilocular cystic nephroma, which may need surgical intervention; whereas LRCD maybe followed up under imaging.

CASE REPORT

A 40-year-old male patient presented with pain in the left loin. A screening ultrasound revealed a complex cystic mass in the lower pole of the left kidney. Contrast-enhanced computed tomography (CECT) showed a cluster of variable-sized simple renal cysts involving the lower pole of the left kidney, separated by normally enhancing intervening renal parenchyma and no definitive capsule. The left renal vessels were normal [Figures 1]. One of the cysts appeared hyperdense on plain study [Figure 2a], suggesting hemorrhage within. The left renal pelvicalyceal system was normal [Figure 2b]. No cysts were seen in the contralateral kidney and in the other solid organs in the abdomen. The patient had no family history of renal cystic disease.

Figure 1

Axial (a) and coronal (b) contrast-enhanced computed tomography showing a cluster of variable-sized simple renal cysts (white arrow), separated by normally enhancing intervening renal parenchyma (black asterisk) involving the lower pole of the left kidney with no definite capsule

Figure 2

Axial plain computed tomography (a) showing a solitary hyperdense cyst (white arrow) among the cluster, suggesting hemorrhage. Axial contrast-enhanced computed tomography (b) in the delayed phase showing the normally opacified pelvicalyceal system on both sides

Based on these characteristic imaging findings and clinical history, the diagnosis of localized renal cystic disease (LRCD) with a solitary hemorrhagic cyst was made. Pain in the left loin was attributed to the hemorrhagic cyst. A follow-up using CECT at 6 months was suggested to confirm the non-progressive nature of the condition.

DISCUSSION

LRCD is also known as segmental renal cystic disease or unilateral renal cystic disease.[1] It is a rare, non-hereditary benign condition, characterized by with multiple cysts in part or whole of one kidney with no cysts in the contralateral kidney or other organs.[12] It is a non-progressive and non-surgical condition.[2] Follow-up imaging is suggested at 3–6 months and then annually to document its non-progressive nature.[3]

Computed tomographic findings of this condition are characteristic, demonstrating multiple simple cysts of varying sizes forming a conglomerate mass with no definitive capsule and normally enhancing intervening renal parenchyma.[1]

On imaging, the differentials to be considered are the autosomal dominant polycystic kidney disease, in which cysts are often bilateral and may be seen in other organs,[1] multicystic dysplastic kidney that is characterized by an atretic pelvicalyceal system and ureter[2] and multilocular cystic nephroma where the cystic mass shows discrete encapsulation.[2]