Nutcracker syndrome (a Delphi consensus)

Nutcracker syndrome (NCS) describes the symptomatic compression of the left renal vein between the aorta and superior mesenteric artery. Whereas asymptomatic compression is a common radiological finding, patients with NCS can report a range of symptoms. There are no specific diagnostic criteria and interventions include a range of open surgical and endovascular procedures. Therefore, we wished to develop an international consensus document covering aspects of diagnosis, management, and follow-up for patients with NCS.

A three-stage modified Delphi consensus was performed. A steering committee developed 37 statements covering 3 categories for patients with NCS: diagnosis, management, and follow-up. These statements were reported individually by 20 international experts in the management of venous disease, using a 5-point Likert scale. Consensus was defined if ≥70% of respondents rated the statement between 1 and 2 (agreement) and between 4 and 5 (disagreement). Those statements without consensus were recirculated in a second round of voting. A third round of the questionnaire was performed with 14 additional statements to clarify diagnostic values of NCS.

Responses were returned by 20 of 20 experts (100%) in round one and 17 of 20 (85%) in round two. Initial consensus was reached in 24 of 37 statements (65%) spread over all categories. Round two achieved a further consensus on 5 out of 10 statements (50%). No categories reported consensus on all statements. In round two consensus was reached in the category of follow-up (4/5 statements [80%]). The final round reached consensus on 5 out of 14 statements (36%). Experts agreed that imaging is obligated to confirm NCS. Experts did not agree on specific diagnostic cut-off values. There was a consensus that the first choice of operative treatment is left renal vein transposition and that the risk of stent migration outweighs the advantages of a percutaneous procedure.

Consensus was achieved on most statements concerning the assessment and management of NCS. This Delphi consensus identified those areas in which further research is needed, such as antiplatelet therapy, endovascular treatment, and renal autotransplantation. A rare disease registry to improve data and reports of patient outcomes is warranted.