Human intestinal water absorption: direct vs. indirect measurements

Area of Science:

• Gastroenterology
• Human Physiology
• Intestinal Transport

Background:

• Understanding intestinal fluid and electrolyte absorption is crucial for managing dehydration and nutritional support.
• Carbohydrate-electrolyte (CE) solutions are commonly used for rehydration, but their precise effects on human duodenojejunal transport require detailed investigation.

Purpose of the Study:

• To quantify net water and electrolyte absorption/secretion in the human duodenojejunum perfused with distilled water, a CE solution, or a 10% glucose solution.
• To compare the transport characteristics of different perfusates using non-absorbed indicators.

Main Methods:

• Infusion of distilled water, CE solution (sucrose, glucose, NaCl, KCl), or 10% glucose solution into the duodenojejunum of seven men using the triple lumen technique.
• Measurement of net water absorption via polyethylene glycol (PEG) concentration changes and deuterium oxide (D2O) plasma accumulation.
• Analysis of intestinal fluid and blood for D2O, electrolytes (Na+, K+), osmolality, and glucose.

Main Results:

• Net fluid absorption occurred with distilled water (-9.40 ml/h/cm) and the CE solution (-13.30 ml/h/cm).
• A 10% glucose solution induced net fluid secretion (4.40 ml/h/cm).
• CE solution perfusion resulted in net Na+ and K+ absorption, while 10% glucose caused electrolyte secretion.

Conclusions:

• Carbohydrate-electrolyte solutions effectively promote net fluid and electrolyte absorption in the human duodenojejunum.
• High glucose concentrations (10%) can impair net absorption, leading to fluid and electrolyte secretion.
• Deuterium oxide is a reliable indicator for assessing fluid absorption rates independently of the perfusate composition.