[Morpho-functional study of the kidney in patients with kidney disease and liver disease with magnetic resonance].

INTRODUCTION

We studied renal function and perfusion after the i.v. injection of Gd-DTPA-BMA, a nonionic paramagnetic contrast agent, to assess renal morphology and function in normal subjects, in renal insufficiency patients and in patients with hepatic failure and normal renal function. The latter were chosen because some patients with advanced hepatic failure may suffer from the hepatorenal syndrome, characterized by severe vasoconstriction in the renal cortical vessels. We investigated if dynamic MRI can detect early renal perfusion abnormalities in the patients who will eventually develop this syndrome.

MATERIAL AND METHODS

Thirty MR examinations were carried out on 30 subjects after the i.v. injection of Gd-DTPA-BMA. Our series consisted of: 10 normal subjects; 10 renal insufficiency patients; 10 patients with hepatic failure and normal renal function. MR examinations were performed on a Philips ACS II scanner operating at 1.5 T. Two sequences were carried out in all cases: T1-weighted SE and T1-weighted TGE sequences after the bolus injection of .1 mmol/kg contrast agent. Renal longitudinal diameter and parenchymal thickness were measured in all cases and signal intensity time curves were always made. The signal intensity of the cortex, corticomedullary junction, medulla and pyelocaliceal system of each kidney was measured using a region of interest (ROI). The signal intensity curves were made considering quantitative parameters, including the area below the curve (ASC), the peak (P) and the time to peak (T-P).

RESULTS

Longitudinal diameter and parenchymal thickness values were significantly lower in renal insufficiency patients than in normal subjects. Four phases were demonstrated after i.v. contrast agent injection in normal subjects, namely A) the cortical phase, B) the corticomedullary junction phase, C) the medullary phase, D) the pyelocaliceal phase. No signal intensity decrease in the medullary and pyelocaliceal curves was observed in renal insufficiency patients. Signal intensity curves values were lower in hepatic failure patients than in those with normal renal function. Hepatic failure patients could be divided into two groups: 5 patients had low P and ASC values and 4 had normal P and ASC values. The patients with lower P and ASC values developed the hepatorenal syndrome within a few months of the MR examination.

DISCUSSION

Signal intensity decreased in the pyelocaliceal system phase in normal subjects because of the high paramagnetic contrast agent concentration. The lack of signal intensity decrease in renal insufficiency patients was caused by the reduced capability of concentrating Gd-DTPA-BMA. Lower signal intensity values in hepatic failure patients may be considered an early sign of the hepatorenal syndrome.