This article was originally posted on RealClearScience.
“Defecation is a major activity of daily living.” Thus begins a new paper in the journal Scientific Reports, and truer words have rarely been written.
Most humans who are physically unable to drop a deuce, perhaps from cancer or an anatomical anomaly, must undergo a colostomy. In this medical procedure, the large intestine is diverted via a surgically created opening (called a stoma) to an external bag that collects feces, which must be emptied regularly. Many people who wear such devices suffer from psychological problems and a lower quality of life. An alternative — any alternative — is preferable.
Japanese researchers have turned to anorectal transplants. In their estimation, this has the potential to surprass traditional reconstructive surgical techniques, which do not properly restore anal function. In order to develop the technique, the authors practiced on four healthy beagles, performing the very first successful anorectal autotransplant in dogs. (In an autotransplant, the transplanted tissue comes from the same animal.)
The researchers removed the existing anorectal region, replaced it with a graft formed from other nearby tissues, and reconnected the blood vessels and nerves. The dogs were then fed a liquid diet. The transplant in Dog #1 was unsuccessful, and it was euthanized the next day. Dogs #2 and #3 survived for three and four days, respectively, before being euthanized.
Dog #4 survived nine days, and the researchers injected it with a dye (indocyanine green) in order to monitor and collect data on blood flow to the tissue graft, a procedure known as an angiography. (See figure.)
As shown above, figure (i) depicts the anorectal region, while figures (j) and (k) depict the anorectal region before and after the angiography had begun. The colored dots represent areas in which the authors were interested in collecting blood flow data. (Red = positive control; Blue = negative control; Yellow = anal canal; Green = perianal skin.) Blood flow, as illustrated in figure (l), was considered satisfactory and compared favorably to a dog that never underwent surgery.
Likely because the dogs were only fed a liquid diet, they did not defecate after the surgery. So, the authors cannot definitively determine if the graft functioned properly. However, demonstrating normal blood flow post-surgery is a positive first step.
Now, you might be wondering, Why did they practice this technique in dogs? Good question. Other researchers have successfully attempted similar procedures in rats and pigs. However, the authors claim that these animal models are unsatisfactory because they do not exhibit the same bowel control that dogs and humans do. In other words, man and man’s best friend can poop (or not) on command. Thus, it is best to perfect the technique in dogs.
How about non-human primates? They are problematic because, as the authors write, “they are not usually trained with good lavatory manners.” Indeed.
Source: Jun Araki et al. “Anorectal autotransplantation in a canine model: the first successful report in the short term with the non-laparotomy approach.” Scientific Reports 4, Article number: 6312. Published: 10-Sept-2014. doi:10.1038/srep06312