A 2021 systematic review and meta-analysis also explored the diagnosis of malrotation and midgut volvulus via ultrasound.³ Inclusion criteria were ages 0-21 years who had suspected malrotation with/without volvulus, the presence of a reference standard for comparison, and reported results. Reference standards did vary by study and included surgical identification, upper GI study, CT, MRI, clinical follow up, or any combination of these as a composite reference. Seventeen studies were identified and included in the systematic review. Included studies evaluated the relationship between the SMA/SMV, whirlpool sign, or duodenal position in relationship to the SMA. Not all studies included all of these ultrasound signs. The pooled data (n=2,257 patients) for malrotation with or without midgut volvulus yielded a sensitivity of 94 percent (95 percent CI 89-97 percent) and specificity of 100 percent (95 percent CI 97-100 percent). This demonstrated a positive likelihood ratio of 317 and a negative likelihood ratio of 0.06, which are both excellent tests for malrotation and suggest that ultrasound can be used to effectively evaluate for malrotation with or without volvulus.

A separate systematic review and meta-analysis looked at the role of the whirlpool sign, alone, in diagnosing midgut volvulus.⁴ So not just malrotation, but malrotation with midgut volvulus. The authors included 16 studies with 1,640 patients and found a pooled sensitivity and specificity of 87.42 percent (95 percent CI 81.05-92.25 percent) and 98.63 percent (95 percent CI 97.88-99.18 percent), respectively. While the whirlpool sign itself is not as sensitive for midgut volvulus, its overall ability to diagnose malrotation with midgut volvulus is very good and it appears to be a reasonable diagnostic option, especially when working in a setting without the ability to obtain an upper GI study. Furthermore, the ability to evaluate for the correct SMA/SMV orientation adds a significant amount of value to the study.

Summary

If you work in a setting with the ability to evaluate potential malrotation with or without volvulus via ultrasound, it appears to be a very good diagnostic tool to help with clinical decision-making. It is important to evaluate for both the position of the SMA in relationship to the SMV as well as for the “whirlpool” sign. With the ability to evaluate these two parameters, the sensitivity and specificity approximate 95 percent and 100 percent, respectively.

Dr. Jones is associate professor at the department of emergency medicine & pediatrics and the program director of pediatric emergency medicine fellowship at the University of Kentucky in Lexington, Kentucky.