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Perirenal MR high signal--a new and sensitive indicator of acute ureteric obstruction
F Regan1, J Petronis, M Bohlman
1Department of Imaging, Johns Hopkins Bayview Medical Centre, Johns Hopkins University Medical School, Baltimore, MD 21224, USA.
Purpose:
This study was carried out to determine the incidence of perirenal magnetic resonance (MR) high signal in acute ureteric obstruction as demonstrated by half-Fourier acquisition single shot turbo spin-echo (HASTE) MR. In addition, we evaluated the sensitivity of this perirenal MR high signal as a predictor of acute ureteric obstruction.
Materials And Methods:
A prospective evaluation of 55 consecutive patients with suspected ureteric obstruction was carried out using the HASTE MR sequence. Images were compared to concurrent IV urography (IVU) or to computed tomography (CT) where these were available. Acute and chronic ureteric obstruction were differentiated by clinical evaluation.
Results:
Forty-one patients had obstructed kidneys. HASTE MR accurately predicted the presence of acute ureteric obstruction in 20/23 (87%) based on presence of perirenal MR high signal. None of these showed evidence of contrast medium extravasation on the concurrent i.v. urogram. 15/18 (83%) chronically obstructed kidneys demonstrated no perirenal high signal on HASTE MR, and the remaining three showed only a trace of perirenal high signal. CT showed perirenal stranding in only 2/8 patients with acutely obstructed kidneys.
Conclusion:
In acute ureteric obstruction, HASTE MR shows perirenal high signal intensity much more commonly than IVU shows extravasation or CT showing perirenal stranding. The origin of this MR signal is uncertain but may represent oedema, lymphatic distension or free fluid from forniceal rupture. HASTE MR can accurately distinguish between acute and chronic ureteric obstruction based on the degree of perirenal high signal.
Insights
Half-Fourier acquisition single shot turbo spin-echo (HASTE) MR accurately detects perirenal high signal in acute ureteric obstruction. This finding reliably distinguishes acute from chronic obstruction, offering a sensitive imaging biomarker.
Area of Science:
- Radiology
- Urology
- Medical Imaging
Background:
- Ureteric obstruction is a common urological condition.
- Accurate differentiation between acute and chronic obstruction is crucial for timely management.
- Conventional imaging modalities have limitations in detecting early signs of obstruction.
Purpose of the Study:
- To determine the incidence of perirenal high signal on half-Fourier acquisition single shot turbo spin-echo (HASTE) MR in acute ureteric obstruction.
- To evaluate the sensitivity of perirenal MR high signal as a predictor of acute ureteric obstruction.
- To assess the ability of HASTE MR to differentiate between acute and chronic ureteric obstruction.
Main Methods:
- Prospective evaluation of 55 patients with suspected ureteric obstruction using HASTE MR sequence.
- Comparison of HASTE MR images with concurrent intravenous urography (IVU) or computed tomography (CT).
- Clinical evaluation to differentiate between acute and chronic ureteric obstruction.
Main Results:
- HASTE MR accurately predicted acute ureteric obstruction in 87% of cases based on perirenal high signal.
- Chronically obstructed kidneys showed minimal or no perirenal high signal on HASTE MR (83%).
- CT demonstrated perirenal stranding in only 2/8 acutely obstructed kidneys, compared to HASTE MR's higher sensitivity.
Conclusions:
- HASTE MR demonstrates perirenal high signal more frequently than IVU or CT in acute ureteric obstruction.
- The perirenal high signal on HASTE MR is a sensitive indicator for acute ureteric obstruction.
- HASTE MR effectively distinguishes between acute and chronic ureteric obstruction based on the degree of perirenal high signal.