The superior mesenteric artery angle in diagnosis of nutcracker syndrome: a systematic review and meta-analysis

PurposeNutcracker syndrome (NCS) can be caused by narrowness of the superior mesenteric artery (SMA) angle. Nevertheless, the cut-off value of the SMA angle is controversial and variable. Therefore, the present study evaluated the optimal SMA angle to maximize diagnostic performance for NCS diagnosis by conducting a meta-analysis.MethodsWe comprehensively searched the English literature related to the diagnosis of NCS from the perspective of SMA (from the date of database inception to June 2022). The accuracy of an SMA angle less than 41 degrees in the diagnosis of NCS was evaluated by calculating the pooled sensitivity (SEN), pooled specificity (SPE), positive likelihood ratio (LR+), negative likelihood ratio (LR-), summary receiver operating characteristic (SROC) curve and area under the curve (AUC) value. The I2 test and meta-regression analysis were used to assess heterogeneity and sources of heterogeneity, respectively. Publication bias was assessed using Deeks' funnel plot asymmetry test.ResultsSix studies (526 patients) met the inclusion criteria. SEN and SPE were 0.94 (95% confidence interval (CI) 0.80-0.99) and 0.85 (95% CI 0.65-0.94), respectively. The LR + value was 6.0, and the LR- value was 0.07, revealing that SMA angles less than 41 degrees exhibited an excellent ability to help confirm or exclude NCS. Additionally, SROC curves showed that the AUC of SMA angles less than 41 degrees for the diagnosis of NCS was 0.96, indicating that SMA angles less than 41 degrees have good efficacy for helping to diagnose NCS.ConclusionThis study explored the diagnostic efficacy of the cut-off value of the SMA angle by meta-analysis. According to the high SPE and SEN results, SMA angles less than 41 degrees have good efficacy in facilitating NCS diagnosis.