Hi Mseth, the test for bile acid malabsorption is called a Sehcat test.
http://en.wikipedia.org/wiki/SeHCAT
I have heard it is not available in the US, I don't know if this is still the case.
BAM particularly affects the fat soluble vitamins (A,D,E,K) and possibly others but K is apparently particularly vulnerable as it is usually not as abundant in the diet.
The treatment for BAM is bile acid sequestrants, drugs that bind to the bile acids and slow digestive transit. This can stop the diarhoea but does not treat the vitamin deficiency as it binds the vitamins also. I have since read that Psyllium and slippery elm do a similar job. Nobody seems to know what the root cause is, but my problems started after a stomach bug about 20 years ago.
I moved from the Thorne drops to the capsules as it was cheaper!