| Meckel's diverticulum | |
|---|---|
 | |
| Schematic drawing of a Meckel's diverticulum with a part of the small intestine. | |
| Specialty | Medical genetics  |
| Named after | Johann Friedrich Meckel |
AMeckel's diverticulum, a truecongenitaldiverticulum, is a slight bulge in thesmall intestine present at birth and avestigial remnant of thevitelline duct. It is the most common malformation of thegastrointestinal tract and is present in approximately 2% of the population,[1] with males more frequently experiencing symptoms.
Meckel's diverticulum was first explained byFabricius Hildanus in the sixteenth century and later named afterJohann Friedrich Meckel, who described the embryological origin of this type of diverticulum in 1809.[2][3]
The majority of people with a Meckel's diverticulum areasymptomatic. An asymptomatic Meckel's diverticulum is called asilent Meckel's diverticulum.[4] If symptoms do occur, they typically appear before the age of two years.[5] The most common presenting symptom is painlessrectal bleeding such asmelaena-like black offensive stools, followed byintestinal obstruction,volvulus andintussusception. Occasionally, Meckel's diverticulitis may present with all the features ofacute appendicitis.[6] Also, severe pain in theepigastric region is experienced by the person along with bloating in the epigastric and umbilical regions. At times, the symptoms are so painful that they may cause sleepless nights with acute pain felt in the foregut region, specifically in theepigastric andumbilical regions.[citation needed] In some cases, bleeding occurs without warning and may stop spontaneously. The symptoms can be extremely painful, often mistaken as just stomach pain resulting from not eating or constipation.[citation needed] Rarely, a Meckel's diverticulum containing ectopic pancreatic tissue can present with abdominal pain and increased serum amylase levels, mimicking acute pancreatitis.[7]
The lifetime risk for a person with Meckel's diverticulum to develop certaincomplications is about 4–6%. Gastrointestinal bleeding,peritonitis orintestinal obstruction may occur in 15–30% of symptomatic people (Table 1). On rare occasions the diverticulum can herniate through the abdominal wall also known as aLittre hernia. Only 6.4% of all complications require surgical treatment, and untreated Meckel's diverticulum has amortality rate of 2.5–15%.[8]
Table 1 – Complications of Meckel's Diverticulum:[9]
| Complications | Percentage of symptomatic Meckel's Diverticulum (%) |
|---|---|
| Haemorrhage | 20–30 |
| Intestinal obstruction | 20–25 |
| Diverticulitis | 10–20 |
| Umbilical anomalies | ≤10 |
| Neoplasm | 0.5-2 |
Bleeding of the diverticulum is most common in young children, especially in males who are less than 2 years of age.[10] Symptoms may include bright red blood in stools (hematochezia), weakness, abdominal tenderness or pain, and evenanaemia in some cases.[11]
Bleeding may be caused by:
The appearance of stools may indicate the nature of the bleeding:
Inflammation of the diverticulum can mimic symptoms of appendicitis, i.e., periumbilical tenderness and intermittent crampy abdominal pain. Perforation of the inflamed diverticulum can result in peritonitis. Diverticulitis can also causeadhesions, leading to intestinal obstruction.[14]
Diverticulitis may result from:
Symptoms: Vomiting, abdominal pain and severe or completeconstipation.[18]
Anomalies between the diverticulum and umbilicus may include the presence of a fibrous cord,cyst, fistula, or sinus, leading to:[14]
Neoplasms (tumors) in Meckel's diverticulum may cause bleeding, acute abdominal pain, gastrointestinal obstruction, perforation or intussusception. They may bebenign ormalignant.[14]
The omphalomesenteric duct (omphaloenteric duct, vitelline duct, or yolk stalk) normally connects the embryonic midgut to the yolk sac ventrally, providing nutrients to the midgut during embryonic development. The vitelline duct narrows progressively and disappears between the 5th and 8th weeks of gestation.[citation needed]
In Meckel's diverticulum, the proximal part of vitelline duct fails to regress and involute, which remains as a remnant of variable length and location.[16] The solitary diverticulum lies on the antimesenteric border of the ileum (opposite to themesenteric attachment) and extends into the umbilical cord of the embryo.[8] The left and right vitelline arteries originate from the primitivedorsal aorta, and travel with the vitelline duct. The right becomes thesuperior mesenteric artery that supplies a terminal branch to the diverticulum, while the left involutes.[17] Having its own blood supply, Meckel's diverticulum is susceptible to obstruction or infection.
Meckel's diverticulum is located in thedistalileum, usually within 60–100 cm (2 feet) of theileocecal valve. Thisblind segment or small pouch is about 3–6 cm (2 inch) long and may have a greaterlumen diameter than that of theileum.[20] It runs antimesenterically and has its own blood supply. It is a remnant of the connection from theyolk sac to the small intestine present duringembryonic development. It is atrue diverticulum, consisting of all three layers of thebowel wall:mucosa,submucosa andmuscularis propria.[17]
As the vitelline duct is made up ofpluripotent cell lining, Meckel's diverticulum may harbor abnormal tissues, containing embryonic remnants of other tissue types.Jejunal,duodenal mucosa orBrunner's tissue were each found in 2% ofectopic cases.Heterotopic rests ofgastric mucosa andpancreatic tissue are seen in 60% and 6% of cases respectively. Heterotopic means the displacement of an organ from its normal anatomic location.[21] Inflammation of this Meckel's diverticulum may mimic appendicitis. Therefore, during appendectomy, ileum should be checked for the presence of Meckel's diverticulum, if it is found to be present it should be removed along with appendix.[citation needed]
Amemory aid is the rule of 2s:[22]
However, the exact values for the above criteria range from 0.2–5 (for example, prevalence is probably 0.2–4%).[citation needed]
It can also be present as an indirecthernia, typically on the right side, where it is known as a "Hernia ofLittré". A case report of strangulatedumbilical hernia with Meckel's diverticulum has also been published in the literature.[23] Furthermore, it can be attached to the umbilical region by the vitelline ligament, with the possibility of vitelline cysts, or even a patent vitelline canal forming a vitellinefistula when the umbilical cord is cut. Torsions of intestine around the intestinal stalk may also occur, leading to obstruction,ischemia, andnecrosis.
Atechnetium-99m (99mTc)pertechnetate scan, also called Meckel scan or nuclear scintigraphy scan, is the investigation of choice to diagnose Meckel's diverticula in children. This scan detectsgastric mucosa; since approximately 50% of symptomatic Meckel's diverticula have ectopic gastric or pancreatic cells contained within them,[24] this is displayed as a spot on the scan distant from the stomach itself. In children, this scan is highly accurate andnoninvasive, with 95% specificity and 85% sensitivity;[17] however, in adults the test is only 9% specific and 62% sensitive.[25] This scan is more accurate in children because gastric mucosa is found in 90% of bleeding diverticula; which is the most common symptom in children, not adults.[26]
Patients with these misplaced gastric cells may experiencepeptic ulcers as a consequence. Therefore, other tests such ascolonoscopy and screenings forbleeding disorders should be performed, andangiography can assist in determining the location and severity of bleeding. Colonoscopy might be helpful to rule out other sources of bleeding but it is not used as an identification tool.[citation needed]
Angiography might identify brisk bleeding in patients with Meckel's diverticulum.[17]
Ultrasonography could demonstrate omphaloenteric duct remnants or cysts.[27]Computed tomography (CT scan) might be a useful tool to demonstrate a blind ended and inflamed structure in the mid-abdominal cavity, which is not an appendix.[17]
In asymptomatic patients, Meckel's diverticulum is often diagnosed as an incidental finding duringlaparoscopy orlaparotomy.[citation needed]
Treatment is surgical, potentially with a laparoscopicresection.[17] In patients with bleeding, strangulation of bowel, bowel perforation orbowel obstruction, treatment involves surgical resection of both the Meckel's diverticulum itself along with the adjacent bowel segment, and this procedure is called a "small bowel resection".[17] In patients without any of the aforementioned complications, treatment involves surgical resection of the Meckel's diverticulum only, and this procedure is called a simplediverticulectomy.[17]
With regards to asymptomatic Meckel's diverticulum, some recommend that a search for Meckel's diverticulum should be conducted in every case ofappendectomy/laparotomy done foracute abdomen, and if found, Meckel's diverticulectomy or resection should be performed to avoid secondary complications arising from it.[28]
Meckel's diverticulum occurs in about 2% of the population.[21] Prevalence in males is 3–5 times higher than in females.[20] Only 2% of cases are symptomatic, which usually presents among children at the age of 2.[8]
Most cases of Meckel's diverticulum are diagnosed when complications manifest or incidentally in unrelated conditions such as laparotomy, laparoscopy or contrast study of the small intestine. Classic presentation in adults includes intestinal obstruction and inflammation of the diverticulum (diverticulitis). Painless rectal bleeding most commonly occurs in toddlers.[5]
Inflammation in the ileal diverticulum has symptoms that mimic appendicitis, therefore its diagnosis is of clinical importance. Detailed knowledge of the pathophysiological properties is essential in dealing with the life-threatening complications of Meckel's diverticulum.[17]
