Where does the fluid come from?

The fluid that accumulates in distended bowel, can only come from the following places;

1. Swallowed fluid
2. Saliva
3. Gastric secretions
4. Hepato-biliary/pancreatic secretions
5. Intestinal secretions
6. Leakage of interstitial fluid into the bowel due to damaged epithelium, leaky capillaries, blocked lymphatic drainage, blocked venous drainage.

Accumulation of fluid in the bowel may be reduced by; getting the patient to swallow less, passage of a nasogastric tube (as above), drugs which reduce gastric secretions (Histamine 2 receptor antagonists Cimetidine, Ranitidine, Proton pump inhibitors Omeprazole, Lanzoprazole) and drugs which reduce pancreatic secretions (Octreotide). Some drugs reduce intestinal secretions too.

The importance of noting the large amount of fluid that accumulates in the bowel is that a lot of this fluid represents loss of fluid from the extracellular fluid compartment. This should be replaced with and extracellular fluid compartment substitute such as 0.9% sodium chloride (normal saline) or Hartman's ¹ solution.

At surgery the fluid may be emptied from the bowel by milking it back towards the nasogastric tube in the stomach where the anaesthetist may aspirate it, or by making an enterotomy and passing a large sucker into the bowel and milking the fluid towards that sucker.