MR cystography provides excellent anatomic detail of the urinary system and is a potential screening examination for vesicoureteral reflux (VUR), according to a new study by researchers from Changi General Hospital in Singapore and the University of California, San Francisco.
In a healthy person, urine is excreted by the kidney and flows down the ureter into the bladder. In patients with VUR, there is an abnormal reverse passage of urine from the bladder back up into the kidney. According to the researchers, this may cause urinary tract infections and kidney damage, often in young children. "The incidence of VUR is under 1% in healthy children, but is 20-50% in children with urinary tract infections," said Hui-Seong Teh, MD, lead author of the study.
For the study, five patients who had VUR detected by conventional X-ray cystography underwent MR cystography. For both conventional and MR cystography, contrast material is put into the bladder using a small tube and the ureters are imaged repeatedly using X-rays or MRI, respectively, to look for reverse flow of contrast into the ureters. The researchers found that the two methods were concordant for 80% of the ureters in these patients. The other 20% was split, with MR cystography detecting VUR in one ureter and X-ray cystography detecting it in the other. The researchers also found that MRI could show scarring of the kidneys and loss of kidney tissue, which is related to the extent of kidney damage from VUR, better than conventional X-ray cystography.
The current radiological tests for assessing VUR involve significant radiation to the patients, say the researchers. Patients with this condition often require repeated examinations to monitor disease progression and assess treatment effectiveness. "Minimizing radiation exposure to the patient is a great concern, particularly for children. For a child 5 to ten years of age, it has been estimated that the radiation exposure from a single conventional X-ray cystogram is equivalent to that of 20 chest radiographs or six months of natural background radiation," said Dr. Teh. "MR cystography is accurate and perhaps more importantly, doesn't expose patients to ionizing radiation," he added.
The full results of the were presented during the American Roentgen Ray Society Annual Meeting in Vancouver, BC.