Superior mesenteric artery stenosis... significant or not?
An 82 year old female was referred for a standard abdominal ultrasound to investigate upper abdominal pain after ingestion of food. The patient revealed that the pain was in the middle of the abdomen, severe, that she could not stand the thought of eating and had lost a substantial amount of weight. She was not diabetic or a smoker but had high blood pressure and cholesterol, which were both medicated.
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Superior mesenteric artery stenosis
Maximum peak systolic velocity of 304 cm/s and spectral broadening in the proximal SMA. This velocity exceeds the accepted PSV of 275 cm/s for the grading of a >70% stenosis
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C+ arterial phase
In the reconstruction, narrowing of the lumen (arrow) is clearly shown extending distally from the origin and clear of any calcification
There was ultrasound evidence of a proximal superior mesenteric artery stenosis of >70% based on the published criteria. Velocities were elevated to a maximum of 304 cm/s with spectral broadening and post-stenotic turbulence. CT-angiography confirmed the presence of a stenosis. Maximum volume reduction estimated by CT-A was 50-60% over a very short segment of 4mm. There was some calcification at the SMA origin but the stenotic segment was clearly seen extending distally to this on the reconstruction.
The patient was referred for assessment by a consultant vascular surgeon. After clinical assessment and taking the patient's history, the surgeon concluded that she did not have symptoms of mesenteric angina and he could not hear an abdominal bruit. A repeat ultrasound within his vascular lab did not reveal any elevated velocities within the SMA but a 50 - 70% IMA stenosis was diagnosed based on a maximum velocity of 266 cm/s. No velocity data for the SMA were mentioned in his report.
The surgeon downplayed the CT-A findings stating that calcifications around arterial origins are a "very common finding and make the interpretation of CT angiography very difficult" and that he has found "the estimation of any stenosis is very inaccurate".
I feel that there is clearly a stenosis but that it is of questionable significance. The CT-A is unequivocal as the stenosis extends away from the area of calcification and our in-house ultrasound findings demonstrate parameters that point to luminal narrowing.
I also feel that the assessment of the true significance of any mesenteric arterial pathology must be made in regards to the clinical picture. Is a "haemodynamically significant stenosis" really significant? Probably not if there is adequate collateralisation. We have seen completely occluded and highly stenosed coeliac axes yet, in each case, the patients were alive and functioning due to a large collateral extending from the bowel to the splenic artery.
As for the different results in the ultrasound assessment: different days, different machines, different transducers, different operators. They all make a difference. Recently, I had a male patient in his late 20s for a renal artery ultrasound that was impossible to scan due to excessive gas. I rebooked him 2 days following. On this occasion, there was little gas and both renal arteries were completely assessed in no time at all. It was one of the easiest renal artery ultrasounds I have ever done.
This case study and other cases of mesenteric artery stenosis we have encountered in our practice begs the question: are the published velocity criteria for grading stenoses of the mesenteric arteries relevant anymore? These criteria were determined quite a while ago in terms of "ultrasound years". There has been rapid development of ultrasound technology since this time.
- Aburahma AF, Mousa AY, Stone PA et-al. Duplex velocity criteria for native celiac/superior mesenteric artery stenosis vs in-stent stenosis. J. Vasc. Surg. 2012;55 (3): 730-8. doi:10.1016/j.jvs.2011.10.086 - Pubmed citation
- Lim HK, Lee WJ, Kim SH et-al. Splanchnic arterial stenosis or occlusion: diagnosis at Doppler US. Radiology. 1999;211 (2): 405-10. Radiology (full text) - Pubmed citation
- Mitchell EL, Chang EY, Landry GJ et-al. Duplex criteria for native superior mesenteric artery stenosis overestimate stenosis in stented superior mesenteric arteries. J. Vasc. Surg. 2009;50 (2): 335-40. doi:10.1016/j.jvs.2008.12.071 - Pubmed citation