Presentation
Stone former with off and on left flank pain. No dysuria, hematuria or fever.
Patient Data
right kidney shows normal perfusion and radiotracer uptake on the initial dynamic study along with good clearance of the tracer from the collecting system on delayed images
non-visualization of the left kidney (non-functioning kidney)
average size right kidney showing homogeneous parenchymal echogenicity with well-preserved corticomedullary differentiation and renal parenchymal thickness.
mild right hydronephrosis; no obvious hydroureter is seen
small/atrophic echogenic left kidney
Small/atrophic left kidney. A nonobstructive calculus measuring 5 mm is seen in the left distal ureter. Right kidney is normal in site, size, shape and parenchymal density. No radiopaque calculi are seen in the right kidney, right ureter and urinary bladder. Right kidney shows homogeneous parenchymal enhancement on the postcontrast study. Normal contrast excretion is noted from the right kidney on the delayed urographic images. Negligible contrast excretion is seen from the left kidney. Non-enhancing and non-opacifying tubular fluid density structures within the right renal pelvis, suggestive of renal sinus cyst (peripelvic cysts). Mild right hydronephrosis is also noted. Mildly prominent right middle ureter, likely due to peristalsis. Normal caliber long retrocecal appendix with its tip lying in a subhepatic location. Small fat-containing umbilical hernia and small hiatal hernia.
Case Discussion
CT urography features are consistent with right renal peripelvic cysts (a type of renal sinus cyst), which can be easily confused with its most common rival (i.e. hydronephrosis), on an ultrasound examination. Multiphasic contrast-enhanced CT scan (particularly its renal excretory phase), is the best imaging modality for differentiating the renal peripelvic cysts from hydronephrosis. Rarely, these entities can coexist (like this case) and need special attention while interpreting the scan to avoid any error.
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