Is this study suggestive of midgut malrotation with volvulus?
No. Although all the images are not provided from the study, the single spot image here demonstrates that contrast cannot pass beyond the pylorus.
What is the best next step in managment?
HPS is not a surgical emergency and medical stabilization takes precedence. Admission to an inpatient floor for intravenous rehydration and correction of electrolyte abnormalities. Commonly, these patients will have hypochloremic, hypokalemic metabolic alkalosis from copious vomiting.
Contrast administered through the NG tube pools in the distal stomach.
Small streak of contrast passes through a narrowed pyloric channel. This is the so-called "string sign."