The traditional duodenal switch (DS), like the gastric bypass (RYGB) and the ModDS, is both a malabsorptive and restrictive surgery.
Risks of traditional duodenal switch surgery
Further, this second connection, like the gastric bypass, increases the risk for life-threatening small bowel obstructions from internal hernias.
This is almost never encountered with the ModDS procedure. Although the traditional DS provides for excellent weight loss, it does come with increased risk.