Peripelvic cysts

Case contributed by Ammar Ashraf

Presentation

Stone former with off and on left flank pain. No dysuria, hematuria or fever.

Patient Data

Age: 55 years
Gender: Female

Tc-99m MAG3

Nuclear medicine
  • 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). 
ultrasound
  • 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.
ct

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). 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); however, unfortunately, it was misinterpreted as hydronephrosis on the initial ultrasound examination which is the most common differential diagnosis of this entity. Just like this case, renal function is usually preserved in this condition.  

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