Obesity has emerged as one of the most important global health challenges of the 21st century. The prevalence of obesity continues to increase worldwide and is strongly associated with metabolic disorders such as type 2 diabetes, hypertension, dyslipidemia, and cardiovascular disease.

Bariatric and metabolic surgery currently represents the most effective treatment for severe obesity and metabolic disease.

However, traditional surgical models were originally designed based on two main principles:

• gastric restriction
• intestinal malabsorption

Advances in gastrointestinal physiology have demonstrated that many of the metabolic benefits of bariatric surgery are mediated by neuroendocrine mechanisms rather than restriction or malabsorption alone.

This paradigm shift led to the development of procedures based on intestinal metabolic stimulation.

Among these approaches, Duodenal Transit Bipartition (DTB) has emerged as a surgical concept aimed at stimulating the distal intestine while preserving gastrointestinal physiology.

This concept has evolved over the last decades and includes several technical variations:

• isolated duodenal transit bipartition
• sleeve gastrectomy with duodenal transit bipartition
• hybrid duodenal bipartition combining endoscopy and laparoscopy

PHYSIOLOGICAL BASIS OF DUODENAL TRANSIT BIPARTITION

Duodenal Transit Bipartition is based on the concept of dual intestinal food pathways.

In this model, ingested nutrients may follow two parallel routes:

1 the physiological pathway through the duodenum and jejunum
2 an accelerated pathway toward the distal intestine

This configuration promotes early stimulation of the distal ileum.

The distal intestine plays a central role in metabolic regulation due to its high density of enteroendocrine cells.

When nutrients arrive rapidly in the ileum, several hormones are released, including:

GLP-1
PYY
oxyntomodulin

These hormones participate in multiple metabolic mechanisms including:

improvement of insulin secretion
reduction of appetite
enhancement of insulin sensitivity

The metabolic effect of bariatric surgery has been closely associated with this phenomenon, known as the incretin effect.

ISOLATED DUODENAL TRANSIT BIPARTITION

One of the most intriguing developments in metabolic surgery is the concept of isolated intestinal bipartition without gastric resection.

This model was initially proposed in situations where completion of classical bariatric procedures was not feasible.

For example, severe hepatomegaly may prevent safe access to the esophagogastric junction during surgery.

In such cases, performing only the intestinal component may represent a safe alternative.

According to long-term follow-up data reported in clinical literature, a duodeno-ileal anastomosis can be created approximately 250 cm from the ileocecal valve, preserving duodenal continuity and avoiding gastrointestinal exclusion.

This configuration allows:

• preservation of the stomach
• maintenance of duodenal passage
• stimulation of distal intestine

Importantly, the preservation of duodenal continuity maintains:

micronutrient absorption
physiological digestion
endoscopic access to the biliary tree

SLEEVE GASTRECTOMY WITH DUODENAL TRANSIT BIPARTITION

A second evolution of the concept combines bipartition with sleeve gastrectomy.

This technique involves two main components:

1 sleeve gastrectomy
2 duodeno-ileal or duodeno-jejunal anastomosis

Unlike the classical duodenal switch, this technique does not exclude the duodenum.

The preservation of duodenal continuity is a key difference compared with classical malabsorptive procedures.

In this model:

• food continues to pass through the pylorus
• duodenal function is maintained
• intestinal stimulation is enhanced

The anastomosis may be performed:

300 cm from the ileocecal valve in duodenoileal configuration
or through duodenojejunal reconstruction.

Technical descriptions indicate that the anastomosis typically measures 4–4.5 cm and is performed in the first portion of the duodenum.

This configuration creates a metabolic intestinal component while preserving physiological digestion.

HYBRID DUODENAL TRANSIT BIPARTITION

More recently, the concept evolved further through the integration of endoscopic and laparoscopic techniques.

Hybrid Duodenal Bipartition combines:

Endoscopic Sleeve Gastroplasty (ESG)
Laparoscopic duodenoileal or duodenojejunal anastomosis.

This hybrid model introduces the concept of endobariatric metabolic surgery.

The endoscopic component reduces gastric volume while the intestinal component enhances metabolic signaling.

Importantly, the procedure preserves the entire digestive tract without gastrointestinal exclusion.

This approach maintains:

gastric function
duodenal function
jejunal and ileal physiology

and allows full endoscopic access to the digestive system.

ROLE OF DISTAL INTESTINE IN METABOLIC SURGERY

The distal intestine is now recognized as a major endocrine organ.

The ileum contains a high concentration of L cells, responsible for the secretion of incretin hormones.

Early arrival of nutrients in the distal intestine results in increased secretion of:

GLP-1
PYY
FGF-19

These hormones influence metabolic pathways including:

insulin secretion
hepatic glucose production
energy expenditure

This mechanism represents the cornerstone of modern metabolic surgery.

NEUROENDOCRINE MECHANISMS

Several neuroendocrine mechanisms explain the metabolic benefits observed after intestinal bipartition.

These include:

incretin stimulation
bile acid signaling
intestinal gluconeogenesis
microbiota modulation

The interaction between these mechanisms forms a complex gut-brain-liver metabolic axis.

LONG-TERM FOLLOW-UP

Long-term follow-up studies demonstrate the feasibility of intestinal bipartition approaches.

Reports have documented cases of isolated duodeno-ileal bipartition followed for up to 19 years, demonstrating sustained metabolic benefits and long-term weight control.

These findings support the concept that intestinal stimulation itself may represent a key therapeutic mechanism.

FUTURE DIRECTIONS

The evolution of metabolic surgery is moving toward procedures that:

preserve gastrointestinal physiology
avoid extensive malabsorption
maximize metabolic signaling

Duodenal Transit Bipartition represents one of the most promising models within this new paradigm.

CONCLUSION

Duodenal Transit Bipartition represents an important evolution in metabolic surgery.

The concept is based on:

early stimulation of the distal intestine
preservation of gastrointestinal physiology
enhancement of incretin response

Over time, several technical variations have emerged, including:

isolated intestinal bipartition
sleeve gastrectomy with bipartition
hybrid endobariatric bipartition

These approaches demonstrate how advances in gastrointestinal physiology are shaping the next generation of metabolic surgery.