We reviewed the clinical history and imaging tests of patients with ultrasound findings suggesting complicated Meckel’s diverticulum in our tertiary pediatric hospital from 2012 to 2017.
Only those cases with surgical and pathological specimen confirmation were included in our revision.
Our pictorial review illustrates the spectrum of Meckel’s diverticulum complications and the imaging findings,
with emphasis on ultrasound.
NORMAL MECKEL DIVERTICULUM
Meckel diverticulum is a blind-ending structure that arises at the antimesenteric border of the distal ileum.
Its length and diameter are variable,
usually about 2 cm up to 5 cm.
It contains all layers of intestinal wall (gut signature): an outermost thin echogenic serosa,
an outer hypoechoic ring corresponding to the muscular layer,
an inner echogenic submucosa and an innermost hipoechogenic thin mucosa,
usually not clearly depicted.
Some authors have described the mucosa submucosa complex as more irregular in Meckel’s diverticulum than in enteric duplication cyst.
Although potentially visible in US when uncomplicated,
it is normally mistaken for bowel loops: demonstration of a blind ending peristaltic structure with “gut signature” connected with an ileal loop is the clue for diagnosis.
Diagnosis though is challenging even when a dedicated technique of graded compression is applied.
The multiplanar capability of CT has increased the diagnosis of non-complicated Meckel’s diverticulum.
HAEMORRHAGE
Haemorrhage due to peptic disease does not depict any characteristic features at ultrasound and diagnosis relies on clinical features and NM studies.
The presence of heterotopic gastric mucosa tends to decline with age,
making bleeding most probable in children.
When a bleeding Meckel’s diverticulum is depicted at ultrasound,
findings are related to accompanying inflammation or perforation (Fig 1-2),
and the US imaging characteristics of those complications will be described below.
MECKEL’S DIVERTICULITIS
US findings in Meckel’s diverticulitis rely on the presence on an aperistatic blind ending structure located periumbilical or at the right iliac fossa (Fig 3) in continuity with an ileal loop with local inflammatory changes.
Characteristic US features of diverticulitis include loss of peristalsis,
lack of compressibility,
thickened walls and increased luminal content in a blind ending structure.
Although variable in length,
in our experience it usually measures less than 25 mm in most cases.
Signs of inflammation of adjacent fat such as increased echogenicity and stranding,
and local hyperemia are also common features and may be “the tip of the iceberg” when facing a Meckel’s diverticulitis.
Endoluminal contents may be fluid,
air/ fluid levels,
enteroliths or fecal-like solid material.
PERFORATED MECKEL’S DIVERTICULIM
Perforation of a Meckel’s diverticulum can occur in the setting of diverticulitis,
gangrene or peptic ulceration due to ectopic gastric mucosa.
Ulceration can occur in the diverticulum itself or in the adjacent ileum.
US features of Meckel’s diverticulum perforation include signs of diverticulitis with the presence of adjacent fluid collections,
extraluminal or transmural gas bubbles and foci of peumoperitoneum.(Fig 4).
INTUSSUSCEPTION
One of the most frequent causes of intestinal obstruction in the setting of complicated Meckel’s diverticulum is intussusception.
It can act as a leading point in intussusception: the diverticulum usually inverts or invaginates into the small bowel and advances to the ileocecal valve and then into the colon.
US findings of a complex intussusception are demonstrated: the intussusceptum not only contains lymph nodes or the appendix but also a complex layered structure or mass located in the center of the intussusceptum.
(Fig 5,
6 & 7).
Since the diverticulum is inverted,
the echogenic inner layer corresponds to the mesenteric fat and serosa of the diverticulum (pseudolipoma sign) and the rest of the layers,
which are thickened and hypoechoic are less easily identifiable.
This ultrasound finding is called the “pseudolipoma” sign.
TORSION OR VOLVULUS
Torsed Meckel’s diverticulum can be a cause of bowel obstruction,
in which the diverticulum is twisted around a omphalomesenteric fibrous band remnant (mesodiverticular band) that attaches it to the umbilicus (Fig.
8).
In those cases,
it appears as a blind ending,
non-compressible,
aperistaltic cystic-like structure.
Internal content may be present secondary to hemorrhage or inspissated material.
In our experience,
a diameter of more than 25mm should rise the suspicion of a volvulated Meckel’s diverticulum since inflamed appendix is usually less than 20mm.
The fibrous band may also predispose to volvulus or rarely forms a true knot between distal ileus and sigma,
or can impinge a small bowel loop with a mesodiverticular band that attaches it to the umbilicus.
OTHER COMPLICATIONS
Meckel’s diverticulum can produce intestinal obstruction due to herniation through the inguinal canal or the umbilicus (Littre hernia).
In most cases Meckel’s diverticulum is rarely diagnosed by imaging prospectively and it is usually found in surgery.
Enteroliths are more commonly seen in patients above 40 years although they have been described in pediatrics also.
Calcification of the enterolith is peripheral with a lucent center in most cases.
Enterolith formation can complicate with intestinal obstruction.
DIFFERENTIAL DIAGNOSIS
Acute appendicitis is the main differential diagnosis of perforated,
inflamed and volvulated Meckel’s diverticulum in children.
In order to avoid incorrect diagnosis,
a dedicated US technique with graded compression at the right lower quadrant is of paramount importance.
Recognition of a normal appendix in the setting of an inflamed blind ending structure nearby; a diameter of more than 25mm; location of the structure halfway between the right lower quadrant and the umbilicus and inability to follow the structure all the way to the cecum should make us think of a complicated Meckel’s diverticulum.
An enteric duplication cyst is also included in the differential diagnosis of complicated Meckel’s diverticulums,
but enteric duplication cysts do not communicate with the bowell and its mucosa is more regular than in Meckel’s diverticulum.
Omental infarction can occur anywhere in the abdomen,
but when occurs at the right lower quadrant or periumbilical,
it can also be included in the differential diagnosis of Meckel’s diverticulitis.
A more superficial location (below the abdominal wall) and the absence of an accompanying inflamed small bowel segment favor the diagnosis of omental infarction.
Other leading points of intussusception can also mimic an invaginated Meckel’s diverticulum in children.
Both lymphoma and polyps lack the characteristic layered disposition of the inverted Meckel’s diverticulum.
Duplication cysts may act also as a leading point of an intussusception,
but conversely to Meckel’s diverticulum,
they do not invaginate into the small bowel lumen,
so the center of the intussusceptum is occupied with a cyst with gut signature at ultrasound.