Obstructive uropathy is a common clinical problem in which most cases can be corrected; time is a significant predictor of prognosis for patients with obstructive uropathy. A delay in therapy can lead to irreversible renal damage. Therefore, proper diagnosis of obstruction is of quite importance for saving the renal function.
This study was performed in Urology and Nephrology Center, Mansoura University over a period from April 2001 to September 2004 to evaluate the role of MR urography in diagnosis of obstructive uropathy. It was applied on 50 patients (94 Renal units) with urinary tract obstruction as indicated by IVU, US or CT studies.
PUT has been performed for all patients and detected 79% of the renal and ureteric stones. PUT didn't give information about presence of urinary tract dilatation &/or obstruction.
IVU was applied for 36 patients with 72 renal unites and detected 72% of the dilated renal systems, 81% of the level of obstruction and 60% of the cause of obstruction.
US was done for all patients and identified hydronephrosis in 100%, detected the level of obstruction in 29% and the cause of obstruction in 29% of obstructed renal unites.
CT was performed for 34 patients, identified hydronephrosis in 100%, detected the level of obstruction in 82% and the cause of obstruction in 89% of obstructed renal unites.
Antegrade & retrograde urography were performed in 12 renal units, detected the level of obstruction in 93% and the cause of obstruction in 100% of the examined renal unites.
Diuretic renography was performed for 12 patients with 23 renal units, differentiated between obstructed & non obstructed systems in 82% the examined obstructed renal unites.
MRU was performed in all patients, identified hydronephrosis in 98%, detected the level of obstruction in 96% and the cause of obstruction in 81% of obstructed renal unites (71% of the renal and ureteric stones and 90% of non-calcular causes of obstruction).
Breath-hold technique was used for all but 3 young patients, was more effective for the compensation of respiratory motion artifacts.
MRU imaging time was comparable with other imaging modalities.
MRU was superior to:
- IVU in detection of urinary tract dilatation, identification of the level and cause of obstruction in non-calcular obstructive uropathy.
- US regarding detection of the level and cause of obstruction.
- CT in detection of the level of obstruction and non-calcular causes obstruction.
- Antegrade & retrograde urography in detecting the level of obstruction.
- Isotope scanning in detection and grading of urinary tract dilatation and in identifying the cause of obstruction.
MRU was inferior to:
- PUT in diagnosis of calcular disease.
- IVU in grading of urinary tract dilatation.
- US in both detection and grading of urinary tract dilatation.
- CT in detection, grading of urinary tract dilatation and diagnosis of calcular disease.
- Antegrade & retrograde urography in identifying the cause of obstruction.
Conclusion
In conclusion, although IVU is currently likely to remain the standard procedure for imaging the upper urinary tract, MR urography provide a reliable alternative to IVU in cases of renal impairment, when iodinated contrast or the application of X-rays is contraindicated or undesirable, in pregnant women, in children and in those with contrast medium allergy.
MR urography provide a reliable alternative to more invasive modalities, such as retrograde or antegrade urography, when the urinary tract fails to opacify during IVU and US fails to locate the level of obstruction.
It is noninvasive technique, demonstrates high sensitivity and spicificity in diagnosing urinary tract obstruction, capable to provide information on anatomy and function of the whole urinary tract in a single examination, being different from excretion urography by its ability of imaging and evaluating the hypofunctional part of the kidney, not requiring ionizing radiation or iodinated contrast materia, short examination time, impossible allergenization and more sensitivity in diagnosis the cause of obstruction.
MRU is suitable for detecting urinary tract obstruction after renal transplantation. It represents a possibility to significantly reduce present examination which exerts a load upon the patient.
The limitation of MRU was its costs, however, by the time it has the potential to be more economic as it can replace multiple separate diagnostic procedures which in sum are costly. |
