Acquired diverticula of the jejunum and ileum
Acquired diverticula in the small intestine are quite rare. In the ileum, they are usually few in number, small in size, and, unlike congenital anomalies, form exclusively on the mesenteric border (mesenteric border) of the terminal segment. Complications are atypical for them, although cases of perforation, bleeding, and fistula formation have been described.
When jejunitis due to diverticular disease develops, contrast-enhanced computed tomography (CECT) serves as the primary diagnostic tool. The scans clearly reveal a sac-like pocket containing gas and fluid. Surrounding it is a zone of acute inflammation with characteristic fat stranding in the adjacent adipose tissue. Neighboring loops of the jejunum respond to the inflammation with marked edema and wall thickening.
Meckel diverticulum: origin and risks
Meckel diverticulum (Meckel diverticulum) is a congenital malformation resulting from the intrauterine failure of the vitelline duct (yolk sac) to obliterate. The condition is detected in 0.5–3% of the population, with approximately 20–40% of these cases manifesting clinically.
The size of the formation ranges from 0.5 to 13 cm. It is localized strictly on the antimesenteric border (antimesenteric border) of the ileum, 30–90 cm proximal to the ileocecal valve.
The danger of the pathology lies in a wide spectrum of potential complications. These include mechanical problems (internal hernia, volvulus, adhesions), as well as ulceration and perforation. The pouch may invert into the intestinal lumen, creating the picture of a polypoid filling defect, which frequently leads to intussusception. Additionally, ectopic gastric mucosa is frequently present within the diverticulum—detected in 20% of adults and 95% of children presenting with gastrointestinal bleeding.
Imaging diagnostics of Meckel diverticulum
Preoperative diagnosis of uncomplicated Meckel diverticulum presents significant difficulties; however, several effective modalities are available to clinicians:
- Scintigraphy: Examination with $^{99m}$Tc-pertechnetate is the method of choice in pediatric practice. The radiopharmaceutical physiologically accumulates in the stomach, and its pathological pooling indicates the presence of ectopic mucosa within the diverticulum.
- Enteroclysis: Allows visualization of the blind pouch. Occasionally, a specific triradiate mucosal fold pattern is identified at its base.
- Computed tomography (CT): Plays a key role in acute diverticulitis. Scans demonstrate a blind pouch with thickened walls that show homogeneous contrast enhancement. Surrounding fat inflammation and free fluid may be visible. An intraluminal enterolith is rare. The primary goal of CT is to exclude other causes with a similar clinical presentation (especially acute appendicitis) and to evaluate for the presence of abscesses or intestinal obstruction.
- Ultrasound: Transverse cross-section reveals an inflamed formation with transmural wall thickening.
- Angiography: Used in patients with chronic bleeding to locate a persistent vitelline artery.
Blind loop syndrome
Conceptually adjacent to the problem of intestinal sac-like formations is blind loop syndrome (Blind Loops). This pathology develops against the background of intestinal strictures or as a consequence of surgical interventions, such as side-to-side intestinal anastomosis (side-to-side).
The blind pouch represents a segment of the proximal intestine extending beyond the stoma. Over time, it is capable of significantly increasing in volume, disrupting normal chyme transit. Content stasis leads to the development of a characteristic symptom complex: abdominal pain, marked bloating, weight loss, steatorrhea, and the appearance of megaloblastic anemia.
Briefly: answers to topical questions
What types of ectopic tissue can be found in the wall of a Meckel diverticulum?
In the wall of a Meckel Diverticulum, islands of ectopic gastric mucosa and/or pancreatic tissue may be present.
- Ectopic gastric mucosa — present in the diverticulum in 20% of adults and 95% of children presenting with gastrointestinal bleeding.
- Ectopic pancreatic tissue — may also be found in the wall of a Meckel diverticulum.
Which abdominal conditions must be differentiated from Meckel diverticulitis?
In Meckel Diverticulitis, other causes with a similar presentation, such as acute appendicitis, must be ruled out.
It is also important during examination to rule out potential complications of Meckel diverticulitis: intestinal obstruction, abscesses, and perforation.
Topographical tip: to avoid confusing the types of sac-like formations, remember their localization. Acquired ileal diverticula "hide" on the mesenteric border of the terminal segment, whereas the congenital Meckel diverticulum is always located on the ANTIMESENTERIC border.
Class and exam questions
What CT signs indicate the development of jejunal diverticulitis?
The tomogram reveals a diverticulum filled with air and fluid. Key signs of inflammation include stranding of the surrounding adipose tissue, as well as marked edema and thickening of the adjacent jejunal loops.
What is the advantage of radioisotope examination in Meckel diverticulum?
Technetium-99m pertechnetate scintigraphy allows the detection of ectopic gastric mucosa, which frequently ulcerates and serves as a source of bleeding. This method is particularly accurate and in demand in pediatric practice.
What condition is Meckel diverticulitis most easily confused with on CT?
Clinically and radiologically, the picture of inflamed Meckel diverticulum is extremely similar to acute appendicitis. The radiologist must confidently identify a normal vermiform appendix to rule out its inflammation.
What is blind loop syndrome?
This is a pathological condition in which a blind intestinal pouch (often forming after side-to-side anastomoses) significantly dilates. Stasis in this area leads to steatorrhea, weight loss, and the development of megaloblastic anemia.
What else to study on this topic
- Eosinophilic gastroenteritis: dependence of the imaging appearance on the affected layer of the intestinal wall.
- Neuromuscular diseases of the gastrointestinal tract: the pseudo-obstruction phenomenon and formation of sacculations.
- Radiological signs of mastocytosis and angioedema of the small intestine («target» sign).
- Specifics of intestinal tract involvement in acute graft-versus-host disease (GVHD).
- NSAID enteropathy and the formation of circular strictures of the small intestine associated with drug use.
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