I propose to analyze the method of determining the magnitude of the colon and rectum, published in the article of Huber et al. . I chose this article because it was published recently and reflects the current state of the problem. The condition of the colon is estimated in 4 different patients with the original signature of the authors (Figure).
FIGURE 1: Contrast Enema Findings
A = normal caliber, non-dilated colon; B = global dilation; C = rectosigmoid dilation;
D = rectal dilation.
A. On the radiograph of the infant, described as a norm, the sigmoid colon comes out of the pelvis and its width is wider than the diameter of the descending colon. These symptoms indicate a megacolon. The total picture is consistent with a diagnosis of "functional constipation". Only on the lateral radiograph of the anorectum the width of the rectum can be accurately measured. To judge the presence of megareсtum we need to compare the width of the rectum with the age norm. In order to judge the degree of the megacolon it is important to compare the volume (capacity) of the colon with the age norm [ See the article, which is attached].
B. On the radiograph of the patient at the age of about 3-5 years the megacolon is determined. The volume of the injected contrast material does not correspond with the capacity (volume) of the colon, as the gut contains a large amount of the feces. There is an expansion of the rectum, sigmoid and descending colon. The right half of the colon is not expanded. In healthy patients all the division of the right colon are wider than the left division.
C. On the radiograph of the teenager the expansion of the rectum and the sigmoid colon is determined. The descending colon is empty, and therefore it is in the tonic contraction. In such expansion of the sigmoid colon also the descending colon is inevitably wider than the age norm. This is not visible because the small amount of contrast medium was introduced at low pressure. It cannot overcome the tone of the descending colon.
D. On the radiograph of the adult patient there is a big fecal stone in the rectum and damaged pelvic floor muscles, what is called the descending perineum syndrome. The method of assessing the state of the puborectalis muscles on the lateral radiograph of the rectum is described in the article on my website . The further filling of the colon was not possible due to leakage of the contrast agent as a result of damage to the pelvic floor muscles. In functional constipation and anorectal malformations with narrow ectopic anus megarectum and megacolon always develops with progressive damage of the pelvic floor muscles. The damage of the piborectalis muscles leads to the fecal incontinence. The levator ani muscle damage leads to the exacerbation of the chronic constipation.
Megareсtum and megacolon have the same pathogenesis in response to а disturbance of the anal canal throughput in the functional constipation; in the anorectal malformations as result of the stenosis of the ectopic anus; in the short segment of Hirschsprung disease above not peristaltic segment of the rectum; after operations due to detachment of the levator ani muscle from the internal anal sphincter. Stagnation of the feces in the rectum leads to expansion of the rectum (megarectum). The feces accumulate in the sigmoid colon, which always leads to the expansion and elongation of this gut. The descending colon is expanded in 70% of cases. The right part of the colon is rarely extended.
You have the right to choose the methods of the investigation and assessment of the rectum, colon and anal canal.
Huber J1, Barnhart DC2, Liechty S1, et al. Characteristics of the Contrast Enema Do Not Predict an Effective Bowel Management Regimen for Patients with Constipation or Fecal Incontinence. Cureus. 2016 Aug 23;8(8):e745. doi: 10.7759/cureus.745.
Levin MD. Descending perineum syndrome. http://www.anorectalmalformations.com/