Radionuclide Cystogram (RNC)

Radionuclide cystograms (RNCs) are tests that employ nuclear medicine to study pathologies like vesicoureteral reflux (VUR).

VUR is a medical condition where, instead of flowing in a one-way direction from the kidneys to the ureters, bladder, and urethra, urine flows backward. This can result in serious complications, such as renal scarring and failure.

Image Credit: Katy Flaty /

About the procedure

The radiopharmaceutical technetium-99m is used for RNC diagnostics and is injected into the bladder through the urethra. Simultaneously, gamma cameras are used to take pictures of the bladder as it fills and empties.

The RNC testing is similar to a voiding cystourethrogram (VCUG); however, as opposed to the RNC, the VCUG uses a contrast dye rather than a radiopharmaceutical agent and provides more anatomical detail.  

What to expect

The entire RNC procedure may last up to half an hour and is more or less painless. Children undergoing this procedure may understandably be scared; therefore, it is advisable that a guardian is present to give a sense of security and assurance to the child.

Any allergies to medications or X-ray contrast materials must be communicated to the physician prior to the RNC procedure. Additionally, all jewelry or accessories that might affect the quality of the images must be removed from the body. Prior to the test, unless otherwise indicated by the attending physician, no special preparations are required, thereby indicating that the patient may drink or eat as usual.

At the onset of the procedure, the patient is placed on an imaging table and a catheter is inserted into the urethra under sterile conditions. The catheter is typically coated with a local anesthetic to numb the lining of the urethra.

Through this catheter, saline combined with radiopharmaceutical is infused into the bladder, which will be filled to its capacity. By this point in the procedure, imaging has already begun. Once the bladder is full, the catheter is removed and the patient is asked to urinate into a container placed nearby. Imaging will continue during this process, until the bladder is empty.

After the procedure is done, the radiologist will analyze all of the acquired images prior to making and sending that report to the attending physician. If normal, the bladder and urethra will show typical function and size. Neurogenic bladder, reflux nephropathy, ureterocele (i.e. the ballooning of the distal ureter to form a pouch as it opens into the bladder) and diverticula, are just some of the pathologies that may be identified with an RNC. Patients are managed accordingly.

Risks and complications

There are small risks involved in terms of radiation exposure from the radioisotopes used in RNCs; however, the radiation is mild and leaves the body within a short period of time.

Following the procedure, a patient may experience some perineal discomfort and painful urination, both of which are transient and disappear within a few hours. Urinary tract infections (UTIs) are also possible, which is why sterile conditions are typically required during catheterization. Bladder perforation is another possible but rare complication that may occur following the RNC.


Further Reading

Last Updated: Mar 20, 2021

Dr. Damien Jonas Wilson

Written by

Dr. Damien Jonas Wilson

Dr. Damien Jonas Wilson is a medical doctor from St. Martin in the Caribbean. He was awarded his Medical Degree (MD) from the University of Zagreb Teaching Hospital. His training in general medicine and surgery compliments his degree in biomolecular engineering (BASc.Eng.) from Utrecht, the Netherlands. During this degree, he completed a dissertation in the field of oncology at the Harvard Medical School/ Massachusetts General Hospital. Dr. Wilson currently works in the UK as a medical practitioner.


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