ERS3043. Correlation of Imaging and Hemodynamic Findings with Surgical Candidacy in Nutcracker Syndrome
Authors * Denotes Presenting Author
  1. Ece Meram *; University of Wisconsin-Madison
  2. John Swietlik; University of Wisconsin-Madison
  3. Jennifer Philip; University of Wisconsin-Madison
  4. Michael Woods; University of Wisconsin-Madison
  5. David Foley; University of Wisconsin-Madison
  6. Erica Knavel Koepsel; University of Wisconsin-Madison
Nutcracker syndrome (NCS), though rare, can be debilitating with chronic left flank pain and/or hematuria in the setting of left renal vein compression with no other identifiable cause. When medical management is inadequate, surgical correction (eg. renal auto-transplantation), can be an alternative. Accurate diagnosis of NCS can be challenging. Understanding the relationship of catheter-based endovascular (CBE) findings with patient outcomes could help standardize the diagnostic evaluation and improve accuracy. This study aimed to correlate imaging and hemodynamic findings with clinical outcomes for patients with NCS.

Materials and Methods:
This retrospective study included a review of 51 “renal venography” procedures performed from November 2017 to November 2022 at a single institution. Studies with an indication other than NCS or patients with prior NCS treatment were excluded (n=11). The clinical outcomes and CBE findings were recorded in the remaining 40 patients, including venography, pressure measurements, and if available, intravascular ultrasound (n=21). NCS diagnosis was based on the reported final study impression. As secondary endpoints, beak angle (>32°), aortomesenteric angle (AMA<41°), and hilar-to-aortomesenteric ratio (HTAMR>4.9) were measured on the most recent CT/MR imaging prior to the venography. Descriptive statistics and chi-square testing were used for analysis.

Of 40 patients, 95%(38/40) were females (median age 30, range 14-60). 58%(23/40) had a reported diagnosis of NCS on CBE evaluation while 3 studies were deemed equivocal. A trans-stenotic gradient of >=3 mmHg and the presence of collaterals were associated with CBE diagnosis of NCS(p<0.05). All patients with CBE diagnosis of NCS (n=23) were recommended surgical treatment, 78%(18/23) of whom underwent surgery at the time of analysis (17 auto-transplantation, 1 renal vein transposition). The remaining 5 patients were either scheduled for surgery, needed further workup, or refused surgical treatment. 89%(16/18) of patients who underwent surgery reported resolution (n=14) or significant improvement (n=2) of their chronic left flank pain. Only 2 patients had persistent symptoms at 3-month follow-up. There was a statistically significant association between CBE diagnosis of NCS and post-surgical symptom resolution (p<0.05). Of note, 6 other patients were offered surgery for equivocal NCS or loin-pain hematuria syndrome without CBE diagnosis of NCS. When compared with CBE evaluation, AMA was the most sensitive (100%) and the least specific (35%); HTAMR was the most specific (88%) but had the lowest sensitivity (30%). Beak angle with 77% sensitivity and 76% specificity correlated the most with CBE findings (p<0.05).

CBE evaluation of the left renal vein is frequently utilized in the diagnosis of NCS and can have a significant impact on the determination of surgical candidacy. In this study, CBE diagnosis of NCS was highly predictive of post-surgical symptom resolution and had a significant association with the presence of collaterals and/or trans-stenotic gradient >= 3 mmHg (p<0.05).