P26
The utility of pre-procedure renal magnetic resonance angiography in patients awaiting
cardiothoracic procedures: A single centre experience
Talbot B, Kong R1, Hutchinson 1, Trivedi U1, Forsyth A1, Gayfer J1, Kingdon EJ
Sussex Kidney Unit + Sussex Cardiac Centre1, Brighton +Sussex University Hospitals Trust
PROBLEM: 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 postoperative 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.