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IMAGE INTERPRETATION · RENAL AND GENITOURINARY

Why Post-Void Images on a Radionuclide Cystogram

Direct radionuclide cystogram — post-flow total image and post-voiding views showing the bladder before and after urination
Direct radionuclide cystogram — post-flow total image and post-voiding views showing the bladder before and after urination

Provided clinical image

Question

Looking at the post-voiding images on this direct radionuclide cystogram, what is the PURPOSE of obtaining images AFTER the patient voids?

  1. ATo measure the total amount of radiotracer injected into the bladder and calculate the exact administered activity for dosimetry records
  2. BTo assess kidney function by measuring how quickly the kidneys clear the tracer that refluxed into the renal pelves during bladder filling
  3. CTo detect vesicoureteral reflux that occurs only during the voiding phase when bladder pressure is highest, and to measure post-void residual bladder volume
  4. DTo verify proper catheter placement and confirm that all instilled saline has been voided before the catheter is removed
Show the answer and explanation

C. To detect vesicoureteral reflux that occurs only during the voiding phase when bladder pressure is highest, and to measure post-void residual bladder volume

Post-voiding images serve two purposes: (1) They detect VUR that occurs specifically during voiding, when intravesical pressure peaks and tracer may reflux into the ureters that did not reflux during the lower-pressure filling phase — this is called 'voiding reflux.' (2) They allow calculation of post-void residual (PVR) — the amount of tracer (and therefore urine) remaining in the bladder after voiding, which can indicate bladder outlet obstruction or poor bladder emptying. Together, pre-void and post-void images give a complete picture of bladder filling, voiding mechanics, and reflux at all pressure phases.

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← Vesicoureteral Reflux on Radionuclide CystogramDifferential Renal Function on MAG3 →

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