Presentation
Recurrent right loin pain.
Patient Data
right renal upper pole cystic lesion with a central branching stone and a few other dependent stones
thinned parenchyma of the right renal upper pole around the cystic lesion, reflecting partial atrophy
right renal middle calyceal stone with no related backpressure changes
Excretory phase of CT urography confirms the presence of the right upper hydrocalyx, demonstrating contrast excretion in the calyceal cavity. It is obstructed by a branching irregular stone with a few dependent stones distributed at the dilated minor calyces and thinned surrounding renal parenchyma. The middle calyceal stone is also noted.
Case Discussion
The patient had recurrent attacks of right loin pain due to recurrent pyelonephritis; the last one was for one month. Excretory CT urography revealed the right renal upper pole cystic lesion to be an obstructed hydrocalyx by a stone, which also contains a few stones.
Hydrocalyx can be due to infundibular stenosis (congenital or acquired), extrinsic compression of the calyceal infundibulum by a crossing artery (Fraley's syndrome), or a chronically impacted stone, as in this case. It can lead to recurrent pyelonephritis or partial renal atrophy.
On imaging, hydrocalyx can mimic a renal sinus cyst. Differentiation would be based on the excretory phase of a contrast study such as CT urography or intravenous pyelography, in which a hydrocalyx will show internal excretion of contrast.
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