while pin worms can be found anywhere from the rectum to the cecum (and appendix actually) does not necesarrily mean that you will be graced with their presence should you actually have them. Most docs do bowel preps to blow you out clean, so whatever few may have been in the lumwen are now gone. In reality; however, most inhabit the lining of the intestine deep to the mucosal lining. Yherefore; its entirely possible for an infection to remain indolent. Also, alot of the parasitic voodoo occurrs in the dark mysterios void of the small intestine. Its here where many different type of cestodes (flatworms), nematodes (hookworms), and trematodes (flukes) lurk.... and obviously we dont scope there typically. If you have these type of issues you could try doing O/p samples for 10 d straight ... it may seem like a lot ... but whatever works. You have to factor in reproductive tendacies of the parasites but also the level of incompitence of the average lab in the USA, currently >70% false neg, but im sure much higher, which ultimately ensures that you may actually get one legitimate result (with luck) out of your ten samples. You may be able ro stir them up some taking herbal mixes or couple shots of vodka (they do NOT like THAT). Best luck. Also ... for specific parasites there may exist serological(blood) tests for them. So you also have that route. If you are purging for the blowell prep, you may wanna submit some of the stool samples then... kill 2 birds with one stone. Best luck!