The definitive treatment for malrotation with volvulus is:

A. IV corticosteroids: Corticosteroids reduce inflammation in certain gastrointestinal or autoimmune conditions, but they do not correct the structural twisting of the bowel caused by volvulus. They have no role in definitive management. B. Gastric decompression via NG tube: NG tube decompression helps relieve gastric distension and vomiting, but it is only a temporary supportive measure. It does not resolve the underlying volvulus or prevent ischemia. C. Laparoscopic or Ladd procedure with possible bowel resection: The Ladd procedure is the definitive treatment for malrotation with volvulus. It corrects the malrotation, untwists the volvulus, and may include bowel resection if necrosis has occurred. D. Barium enema reduction: Barium enema reduction is used in intussusception, not volvulus. It is ineffective in malrotation with volvulus and may delay the urgent surgical intervention needed.