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Acute renal allograft rejection: difficulty in diagnosis of histologically mild cases by MR imaging
Abstract:
To determine the ability of magnetic resonance (MR) imaging to diagnose various degrees of acute allograft rejection (AR), 33 MR examinations in 28 patients were obtained. Surface coils were used in 21 examinations. Seventeen examinations were correlated with biopsy results, which were graded as absent (n = 7), mild (n = 6), or severe (n = 4) AR. Corticomedullary differentiation (CMD) on T1 weighted images was graded as absent/poor versus distinct, and images were also evaluated for visibility of intrarenal vessels. For serial examinations, renal volume was measured and compared. The MR results were correlated with radionuclide interpretations in 22 cases. Diminished CMD was most common with AR (7 of 12) but was also seen with acute tubular necrosis (2 of 6) and cyclosporin toxicity (2 of 3). All four cases of severe AR had diminished CMD. In contrast, only one of six cases of mild AR had diminished CMD (p less than 0.05). Four of five cases of mild AR by radionuclide scan were correctly diagnosed. Visualization of intrarenal vessels was best with surface coils, but this did not contribute to differential diagnosis. Renal volume was increased in rejecting allografts. Magnetic resonance is a promising modality for investigation of renal allografts but is not a sensitive or specific modality for the diagnosis of mild AR.
Insights
Magnetic resonance (MR) imaging shows promise for diagnosing renal allograft rejection. However, it lacks sensitivity and specificity for detecting mild acute rejection, though it can identify severe cases.
Area of Science:
- Radiology
- Nephrology
- Transplantation
Background:
- Acute rejection (AR) is a significant complication following renal transplantation.
- Accurate and timely diagnosis of AR is crucial for graft survival.
- Magnetic resonance (MR) imaging offers non-invasive assessment capabilities.
Purpose of the Study:
- To evaluate the diagnostic performance of MR imaging in detecting varying degrees of acute allograft rejection.
- To correlate MR findings with biopsy-proven rejection and radionuclide interpretations.
Main Methods:
- 33 MR examinations in 28 patients with renal allografts were analyzed.
- MR images were assessed for corticomedullary differentiation (CMD) and intrarenal vessel visibility.
- Renal volume changes were measured in serial examinations.
- MR findings were compared with biopsy results (absent, mild, severe AR) and radionuclide scans.
Main Results:
- Diminished CMD was observed in 7/12 cases of AR, including all 4 severe AR cases.
- Mild AR showed diminished CMD in only 1/6 cases (p < 0.05).
- Increased renal volume was associated with rejecting allografts.
- MR correctly diagnosed 4/5 cases of mild AR identified by radionuclide scan.
Conclusions:
- MR imaging is a promising tool for evaluating renal allografts.
- MR is not sufficiently sensitive or specific for diagnosing mild acute rejection.
- Severe AR can be identified by diminished corticomedullary differentiation on MR imaging.