الفهرس 
Introduction and Aim of The WorkOnly 14 pages are availabe for public view
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Abstract
The strategy of management of renal obstruction is based upon precise delineation of the anatomy of the obstructed renal unit as well as accurate estimation of the split renal function. The usual approach for evaluation of renal function is based on radioisotope renal scan. However, the gold standard for evaluation of the renal function is the estimation of chemical creatinine clearance. Renal scintigraphy is routinely used to calculate the split renal function, but the calculation is not without problems, including the positioning of the regions used to measure the activity in the kidneys. Poor resolution of this technique represents its main disadvantage specially in dilated and obstructed renal units where the measurement of split renal function could reflect inaccurate values. Chemical creatinine clearance which is considered as a gold standard method evaluates the total renal function. In patients with solitary or solitary functioning kidneys, the situation will be easier as all urethral output reflects a solitary kidney function. In Clinical studies, many attempts have been studied to use a single modality to provide detailed anatomy with good resolution and precise measurement of the split renal function over the regions of interest without hazards of iodinated contrast materials, ionizing radiation or nephrotoxic effects. No technique other than MRI has the potential for accomplishing all these goals. Dynamic MRI provides excellent anatomical images in addition to functional renographic data. Our study was carried out on 60 patients suffering from acute upper urinary tract obstruction of 70 renal units. These renal units were evaluated before relief of obstruction by radioisotope renal scan and dynamic MRI. Serum creatinine, sodium, potassium, uric acid, blood osmolarity and pH were also evaluated. Those patients were reevaluated on the 3rd, 14th, 90th day after relief of obstruction using the same previously mentioned biochemical and imaging modalities. In addition, chemical creatinine clearance, urinary creatinine, sodium, potassium, phosphate, osmolarity, and pH were evaluated on the same intervals after relief of obstruction. Our results states that MRI clearance was more accurate in assessing the kidney function than radioisotope renography before relief of obstruction. After relief of obstruction and after consideration of the chemical creatinine clearance as a gold standard, MRI clearance was still more useful in assessing the renal function. The statistical correlations between the means of MRI and chemical creatinine clearances were always strong before and after relief of obstruction. However, the correlations between the means of radioisotope and chemical creatinine clearances were weak before relief of obstruction and moderate after relief of obstruction. Our results proved that MRI clearance before relief of obstruction represents 70% of the prospected renal clearance on the 90th day after relief of obstruction. In contrast, radioisotope clearance before relief of obstruction represents only 35% of the prospected renal clearance on the 90th day after relief of obstruction. This difference is due to the high anatomical resolution of the MRI which can separate the renal parenchyma from the background and the dilated collecting system. In addition, MRI contrast material is eliminated totally by glomerular filtration which was not affected in acute obstruction. While MAG3 the radioisotope agent, is predominantly eliminated by tubular secretion which is mainly affected in acute obstruction. Also, the diuretic effect of the gadolinium adds more increase to the MRI clearance values over the radioisotope clearance values. Accordingly, measurement of split MRI clearance before relief of obstruction could predict, with high accuracy, the prospected actual split renal function after relief of obstruction. Also, the results stated that, on the 3rd day after relief of obstruction 81%83% of the 90th day clearance could be achieved. The next improvement of renal clearance occurs between the 14th and 90th day after relief of obstruction. To date, dynamic MRI is used primarily in research. Its routine application in assessment of renal function is limited. This is because few researches can provide dynamic MRI serial imaging that are comparable to those obtained with radionuclide renoghraphy allowing split renal function evaluation. Furthermore, the MRI is the most expensive imaging modality compared to scintigraphy. Moreover, the availability of MRI remains limited when compared with renal scintigraphy. All these reasons prevent renal dynamic MRI from completely replacing the radionuclide studies in the near future. A clear advantage of MRI, relatively to scintigraphy, is its ability to offer simultaneous functional and morphological data without exposure to iodinated materials or ionizing radiation. In addition the MRI clearance measurements are more accurate and could predict the prospected renal function in acute urinary obstruction