I am going to get all anal retentive again about the medical information, but what better site to do that on than poopreport.
1. The vast majority of gastric acid is neutralized by bicarbonate secreted in large quantities by the pancreas. The neutralization is extremely rapid (seconds) and would be very difficult to outpace with intestinal peristalsis. The neutralization is essential for the normal function of digestive enzymes which are also secreted by the pancreas.
2. Most diarrhea is caused by an excess of unabsorbed molecules of a substance - (eg sorbitol in gum) that carry water with them in the lower intestine (osmotic diarrhea), or through excess production of intestinal secretions (secretory diarrhea - eg. cholera infection). Excessive gastric acid isn't a cause.
3. Shit is irritating to skin mainly because of the bile salts that are incorporated into it. If it becomes acidic it's mostly because of byproducts of bacterial metabolism. Wiping your starfish raw during a case of bad diarrhea also contributes to this. Skin breakdown and ulceration is due to a combination of these factors as well as the ongoing inflammatory response of skin to these repeated irritants. Ulceration is unlikely to occur with normal hygeine.
I hereby "out" myself and admit to being an MD who never outgrew the ability to laugh at a good shit story. I come for the "Day I Ruined Thanksgiving" type of stuff, but can't help trying to clarify medical information when I think I can.
I have to agree with Dave and Bowel Blogger. There is probably an abnormal autonomic nervous system response to rectal distention, requiring hyperstimulation of the area to initiate peristalsis. Admittedly we are all speculating here, and personally I would advise TPT to be seen by a gastroenterologist. This certainly falls into the spectrum of "motility disorder" and in addition, the pains the author describes extending into the back of the knees could be consistent with injury or irritation of sacral nerve roots.
Here are some abstracts related to the topic of "rectal hyposensitivity". I emphasize again that all of this is speculation and the author should be evaluated by a gastroenterologist.
Am J Gastroenterol. 2006 May;101(5):1140-51.
Rectal hyposensitivity
Gladman MA, Lunniss PJ, Scott SM, Swash M.
Gastrointestinal Physiology Unit, Barts and The London, Queen Mary's School of Medicine and Dentistry, Whitechapel, London, United Kingdom.
Rectal hyposensitivity (RH) relates to a diminished perception of rectal distension that is diagnosed during anorectal physiologic investigation. There have been few direct studies of this physiologic abnormality, and its contribution to the development of functional bowel disorders has been relatively neglected. However, it appears to be common in patients with such disorders, being most prevalent in patients with functional constipation with or without fecal incontinence. Indeed, it may be important in the etiology of symptoms in certain patients, given that it is the only "apparent" identifiable abnormality on physiologic testing. Currently, it is usually diagnosed on the basis of elevated sensory threshold volumes during balloon distension in clinical practice, although such a diagnosis may be susceptible to misinterpretation in the presence of altered rectal wall properties, and thus it is uncertain whether a diagnosis of RH reflects true impairment of afferent nerve function. Furthermore, the etiology of RH is unclear, although there is limited evidence to support the role of pelvic nerve injury and abnormal toilet behavior. The optimum treatment of patients with RH is yet to be established. The majority are managed symptomatically, although "sensory-retraining biofeedback" appears to be the most effective treatment, at least in the short term, and is associated with objective improvement in the rectal sensory function. Currently, fundamental questions relating to the contribution of this physiologic abnormality to the development of functional bowel disorders remain unanswered. Acknowledgment of the potential importance of RH is thus required by clinicians and researchers to determine its relevance.
There seems to be an assumption here that there is a 1 to 1 relationship between the length of the log and the distance it extended into the shitter's descending colon. I don't think this is true. Shit, for the most part, is a fairly malleable pasty substance and it will actually distend the rectum -which is fairly elastic. (The more rectal distention, the greater the sense of urgency regarding taking a dump). When you do finally go, the shit is extruded out of the anus, like toothpaste from a tube (albeit, brown, smelly, diarrhea-omlete breath toothpaste) and the length for the most part depends on how much is extruded in an unbroken segment before being "pinched" or separating for whatever other crapping mechanics related reason.
Defecography is the x-ray imaging of the process of shitting which is typically done done with barium paste (mixed with mashed potato) injected into the rectum through the asshole. It can now also be done with MRI and a gadolinium enhanced pseudo-shit mix injected into the rectum. You can see pictures of it via the links below. They illustrate the shit contained in the rectum in "reservoir" fashion and the extrusion process into formed stools.
(note that "feces" also is contained in the descending colon, but it is still extruded. It does not move in an intact column like fashion out of the anus)
WAR IS PEACE
FREEDOM IS SLAVERY
IGNORANCE IS STRENGTH
CONSTIPATION IS DIARRHEA