Re: What causes borborygmus to occur?

        The actual gases are fermentation products of the action of
bacteria on the food and discarded bodily products - dead red cells,
intestinal lining cells, fluid secretions ,and the like, as they pass
through. Mostly, these gases are carbon dioxide, methane, some hydrogen
sulphide( hence the smell) and other chemically  "reducing" gases. Many
of these microbes are anaerobes, which means that, like the earliest
inhabitants of Earth, they do not breathe oxygen, but prefer to live in
an oxygen poor or free environment. Solids are moved through the gut by
successive waves of alternating contraction and dilatation, called
peristalsis. This type of action can be observed in earthworms as they
move, or snakes as they swallow whole prey. If the peristaltic waves are
more frequent or intense, relative inco-ordination can result in pockets
of gas under increeased pressure. As these bubbles make their way
through the gut's fluid contents, bubbling sounds like those in a
Turkish pipe occur, which you perceive as borborygmi.
 Certain foods, eg spices , can stimulate the gut to overact, and
produce borborygmi, or again since the peristalsis is caused by muscles
under nervous control, anxiety or stress can produce similar results.
Some people are oversensitive in this area, and have so-called irritable
bowels. Further build up of pressure leads to local
stretching/dilatation of the bowels locally, which can be intensely
painful( stomach cramps, colic etc). Infection by foreign microbes, eg
cholera, typhoid can set up inflammation of the bowel lining which in
turn may increase gas production, and peristaltic activity- so much so
that products miss out on the final water extraction, and appear as
diarrhoea.
 Then again locally inactive gut -  perhaps replaced by polyps or
tumours, might set up irregularities in the peristalsis in turn leading
to borborygmi , but there are usually other features such as bleeding or
weight loss to give the game away.
 For the ordinary borborygmi, not caused by serious pathology, good
advice is a well varied diet, with due time allowed for its enjoyment
and digestion. A good admixture of roughage/fibres, as cereals or bran
or the like, is advised to even out the pressure within the gut by
giving something solid and consistent for the peristalsis to work on,
and should reduce this problem
 Hope this helps,
 Yours sincerely, 
Michael Martin-Smith