The utility of pre-procedure renal magnetic resonance ...



The utility of pre-procedure renal magnetic resonance angiography in patients awaiting cardiothoracic procedures: A single centre experienceTalbot B, Kong R1, Hutchinson 1, Trivedi U1, Forsyth A1, Gayfer J1, Kingdon EJSussex Kidney Unit + Sussex Cardiac Centre1, Brighton +Sussex University Hospitals TrustPROBLEM: Post-operative acute kidney injury (AKI) has prognostic significance in patients undergoing cardiothoracic surgery. Risk factors for coronary artery disease are also important in renal artery stenosis and observational studies suggest that the 2 lesions may co-exist in many patients. The benefit of intervention in patients with renal artery stenosis is the subject of large studies but there is controlled data in the sub-group of patients awaiting cardiothoracic surgery.PURPOSE: 1) To describe historical local use of pre-procedure renal magnetic resonance angiography (MRA) in a single centre. 2) To consider changes in practice which could be reviewed in future audit cycles.DESIGN: We retrospectively audited cases where renal MRA was performed in anticipation of cardiothoracic intervention. Cases were ascertained by searching the local radiology database for renal MRA requested by cardiothoracic consultants. The list of cases was reviewed and cases with post-operative MRA were discarded. Co-morbid disease, renal arterial interventions and post-operative AKI were identified by case note review.RESULTS: Between 11/2008 - 5/2013 2704 patients underwent elective cardiothoracic surgery at a single cardiothoracic centre. In this period 46/2704 (1.7%) underwent renal replacement therapy for Acute Kidney Injury Network (AKIN) stage 3 kidney injury. Our methodology identified 40 renal MRAs requested by cardiothoracic consultants during preparation for cardiothoracic procedures. Multiple risk factors for renal artery stenosis were identified in the 40 patients. Renal MRA was abnormal in 10/40 patients (Significant unilateral stenosis in patients with 2 functioning kidneys (n=8), bilateral stenosis in patients with 2 functioning kidneys (n=1), stenosis to a single functioning kidney (n=1)). MR studies also identified other renal abnormalities. Seven patients underwent pre-operative renal angioplasty and stenting (6/7 unilateral stenting).31/40 patients went on to have a cardiothoracic procedure following renal MRA. This was complicated by acute kidney injury in 61% (AKIN 1 n=11, AKIN 2 n=2 AKIN 3 n=6). One out of 19 patients underwent post-operative RRT. Eleven out of 19 (58%) of patients showed complete renal recovery (creatinine returned to baseline level).Five out of 7 patients who had renal artery intervention developed AKI. One of these patients required post-operative RRT and in 4/5 renal function returned to baseline levels. 10% (3/31) of the patients who underwent surgery after MRA died within the first month post-operatively.SUMMARY: A) Patients undergoing renal MRA in this cohort had a significant risk of post-operative AKI and a post-operative mortality of 10%. B) Only a minority of patients undergoing renal MRA had unequivocal indications for pre-operative renal angioplasty. C) Clinicians working without a formal protocol perform pre-operative MRA in <1.5% of patients awaiting cardiothoracic surgery. CONCLUSIONS AND PROPOSALS FOR QUALITY IMPROVEMENT INTERVENTIONS : The place of renal MRA in pre-operative assessment of cardiothoracic surgical patients is uncertain. In this retrospective audit it is not clear whether uniform criteria were used to select patients for pre-operative MRA. Although post operative AKI is a significant problem, the role of renal angioplasty as an enabling procedure is unproven. We are undertaking a prospective audit of the performance of renal MRA in this population with the following triggers for ordering an MRA- eGFR <30 AND renal asymmetry (>1.5 cm), refractory hypertension or AKI following blockade of the renin-angiotensin system. ................
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