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What Is the Sensitivity of Ultrasound for Detecting Volvulus in Infants When Compared to An Upper GI Study?

Most of us do not work in a location that has ready access to obtain an upper GI study in infants to evaluate for malrotation with midgut volvulus. While surgical evaluation is the true gold standard for identifying midgut volvulus, the diagnostic study of choice for many surgeons tends to be the upper GI study. But what about ultrasound? In cases where the clinical suspicion is lower for a midgut volvulus, but you feel it still needs to be explored, can ultrasound help?

Interestingly, upper GI studies have a wide range of sensitivities and specificities for diagnosing malrotation with midgut volvulus. The sensitivity for the diagnosis of malrotation, alone, ranges from 40-100 percent.^1,2 The diagnosis of malrotation with midgut volvulus is lower.²

Regarding ultrasound’s ability to diagnose malrotation, a prospective study by Zhou et al included 70 children with suspected malrotation with ages ranging from 2 days to 13 years (median 31 days).¹ These children with suspected malrotation were included based upon their clinical exams and had symptoms of bilious vomiting, repeated upper abdominal pain with vomiting, or upper abdominal distention. Of these 70 children, 23 were confirmed to have malrotation by surgery. Regarding these 23 patients with malrotation, all 23 patients were found to have inversion of the superior mesenteric artery (SMA) and superior mesenteric vein (SMV) and 22 had the ultrasound “whirlpool” sign. Thirteen of the 23 children were noted to have a transverse duodenum in front of the mesenteric artery. The transverse duodenum should be behind the superior mesenteric artery and the “whirlpool” sign—which is indicative of volvulus—occurs when bowel rotates around its mesentery leading to whirls of mesenteric vessels. All cases of malrotation demonstrated inversion of the SMA and SMV and there was a single false positive, yielding a sensitivity and specificity of 100 percent and 97.6 percent, respectively. For the whirlpool sign, the sensitivity was 95.6 percent and specificity was 95.7 percent, respectively. These findings suggest that ultrasound is an excellent tool to evaluate for malrotation with volvulus.

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.

Dr. Cantor is the emeritus medical director for the Central New York Poison Control Center and professor of emergency medicine and pediatrics in Syracuse, New York.

References

1. Zhou L, Li S, Wang W, et al. Usefulness of sonography in evaluating children suspected of malrotation: comparison with an upper gastrointestinal contrast study. J Ultrasound Med. 2015;34(10):1825-1832.
2. Mohamad Burhan MS, Hamid HA, Zaki FM, et al. The performance of ultrasound and upper gastrointestinal study in diagnosing malrotation in children, with or without volvulus. Emerg Radiol. 2024;31(2):151-165.
3. Nguyen HN, Kulkarni M, Jose J, et al. Ultrasound for the diagnosis of malrotation and volvulus in children and adolescents: a systematic review and meta-analysis. Arch Dis Child. 2021;106(12):1171-1178.
4. Enyuma COA, Adam A, Aigbodion SJ, et al. Role of the ultrasonographic “whirlpool sign” in intestinal volvulus: a systematic review and meta-analysis. ANZ J Surg. 2018; 88(11):1108-1116.