Purpose or Case Report: Conventional Doppler US is known to have low sensitivity for the diagnosis of renal artery stenosis (RAS), in particular segmental renovascular disease. This study aims to determine if contrast-enhanced US (CEUS) can quantitatively provide assessment of renal arterial and parenchymal perfusion pre- and post- renal artery angioplasty in children and potentially be used as a follow-up imaging tool.
Methods & Materials: This is a pilot study for pre-, immediate post-angioplasty and 24h post- CEUS exams during quiet breathing to include main renal artery at the hilum and all renal poles in one imaging plane for 2 minutes to assess parenchymal wash-in and peak intensity. Regions-of-interest were placed in upper, mid and lower pole and main renal artery in each study. Average contrast intensity over the total duration of imaging time was used to generate a time-to-peak (TTP) enhancement.
Results: Five consecutive children were identified as meeting inclusion criteria. All cases involved the use of a cutting balloon, a novel technique for resistant renal artery angioplasty. Mean degree of stenosis pre-angioplasty improved from 64.2% (60-74) to 20% (10-31) post-angioplasty. Mean pressure gradient pre-angioplasty was 15.2 mmHg (5-31), post-angioplasty was 11.5 mmHg (3-19).
Mean TTP main renal artery: pre-angioplasty 7.8 secs (6.3-8.7); immediate post-angioplasty 4.4 secs (3.8-5.5); 24h post- 5.4 secs (4.2-6.7).
Mean TTP parenchyma: pre-angioplasty 10.7 secs (8.6-13.7); immediate post-angioplasty 7.2 secs (5.3-8.8); 24h post- 6.8 secs (5.7-10.1).
There was significant improvement of TTPs in renal artery and parenchyma both immediate post-angioplasty and at 24h post- compared to pre-angioplasty (p<0.05).
The mean improvement of TTP in the immediate post-angioplasty and 24h post- follow-up compared to pre-angioplasty in the main renal artery were 3.0 secs (0.8-4.4) and 2.2 secs (1.2-3.4), and in the parenchyma were 3.4 secs (0.2-7.8) and 3.8 secs (1.9-6.8). There was no difference in TTP improvement between immediate post-angioplasty and 24-hour follow up compared to TTP pre-angioplasty in both renal artery and parenchyma (p = 0.29 and 0.32, respectively).
Conclusions: This pilot study suggests that CEUS imaging with standardized protocol may be a useful quantitative adjunctive technique to evaluate pre- and post- angioplasty renal perfusion. It may have the potential to be used as a follow-up tool to monitor the success of the angioplasty and potentially in follow-up studies serve as an early indicator.