Fig. 13.1
Acute ileocolic intussusception in a 4-year-old-boy. (a) Transverse US section shows a target appearance (the crescent-in-doughnut sign). (b) Sagittal section demonstrated a multilayered structure giving the appearance of a sandwich
13.2.2 Rule Out Differential Diagnoses
As previously mentioned, clinical signs can be quite confusing and AII may mimic different diseases including gastroenteritis, appendicitis, Meckel’s diverticulitis, and any other causes of bowel obstruction. US is the examination of choice to differentiate accurately between these different entities. Noteworthy, in children with suspected but absent intussusception, the percentage of other intraabdominal diseases discovered by US has been reported ranging from 4% [9] to 16.7% [10].
Intermittent intussusception: Transient intussusception is extremely frequent and is usually not responsible for the patient’s clinical presentation. The small intestine and preferably the jejunum are mainly involved. It tends to occur in asymptomatic patients or in patients presenting GI viral infections. The loops involved are not thickened, their peristalsis is preserved and there are no signs of upstream bowel distension. The diameter of an ileoileal intussusception is inferior to 2.5 cm and its length is short, less than 3.5 cm [11] (Fig. 13.2). It disappears spontaneously or its position changes during the US examination. The prevalence of transient small bowel intussusception identified by CT with no clinical significance has been reported around 0.4% [12].
False positive results include bowel volvulus secondary to malrotation and thickened bowel wall of any origin (inflammatory, infectious, tumoral, etc.).
Fig. 13.2
Transient jejuno-jejunal intussusception incidentally discovered in a 1-year-old boy explored for UTI. The diameter of this intussusception on US is less than 2 cm. The thickness of the hyperechoic fat corresponding to the invaginated mesentery is similar to the one in Fig. 13.1. In these two cases, type of intussusception cannot be reliably differentiate on the inner fat core sign
Fig. 13.3
Ileocolic intussusception in a 10-month-old-girl secondary to a Meckel’s diverticulum: US appearances. (a) The tip of MD is slightly hyperechoic (short yellow arrow) with some anechoic fluid testifying associated bowel suffering (dashed yellow arrow). Hyperechoic mesenteric fat is present within the intussuscipiens (long yellow arrow). (b) Ischemic small bowel and associated ischemic MD were surgically removed
13.2.3 Look For Evidence of Perforation
Bowel necrosis would lead to perforation and peritonitis but no descriptions of such abnormalities have been reported in pediatric practice either on US or on X-rays.
13.2.4 Identify the Type of Intussusception
For this purpose multiple US signs and measurements have been described.
Diameter: It ranges from 0.8 to 4 cm. Below 2.5 cm, the likelihood of ileoileal intussusception (III) is high but ileocolic intussusceptions (ICI) diameter can be as small as 1.3 cm [13]. The mean diameter of an ileoileocolic (IICI) type is larger than that of an ICI but with a large overlap [14]. Therefore, the diameter alone cannot accurately differentiate between the different types of intussusceptions.
Length: ICI is longer than an III; a length above 3.5 cm has been reported to be a strong independent predictor for the need of surgery [11].
In theory, the number of bowel layers could help to differentiate between an III and an ICI from an IICI which by definition contains more bowel layers. Still, edematous infiltration of these layers induces the loss of their limits and subsequently they cannot be “counted” and distinguished one from another.
Inner fat core (fat surrounding the vessel within the mesentery) has been reported to be almost absent in III, thus its ratio with the thickness of the outer bowel wall (<1.0) is significantly different compared to ICI [13]. In our experience this sign does not appear highly specific (Figs. 13.1 and 13.2).
Lymph nodes inside the lesion are much more frequent in ICI [13]. Peripheral enlarged lymph nodes are frequent but of no diagnostic value except when these enlarged nodes are rounded, frankly hypoechoic, and/or present with a disorganized vascularization, all features that must also raise the suspicion of lymphoma.
Ascites is frequently present. Its volume is usually limited and of no help to differentiate the types of IIA.
Abdominal location:
ICI are more likely to be located within the subhepatic area or the right lower quadrant.
Ileo-ileal spontaneous intussusceptions are preferably located in the paraumbilical area and in the left abdomen.
Type of lead point [15]:
Primary Intussusception: It represents the most frequent form of AII which is either ileocolic or ileoileocolic. Most authors consider the so- called idiopathic or primary intussusception to be in fact related to hypertrophy of lymphoid tissue. Hypertrophied Peyer patches become entrapped and serve as lead point. Viral infections such as those caused by adenovirus, rotavirus, human herpes virus, CMV, and Epstein-Barr virus have all been reported to be associated with intussusceptions. However, the seasonal viral influence is not validated by large studies [16]. On the other hand, vaccination against rotavirus has been shown to be responsible for a slight increase in the incidence of intussusception with a more severe evolution [17]. For Hryhorczuk et al. [10] the overall sensitivity of US to detect intussusception was 97.9% and its specificity was 97.8%; the positive predictive value of the test was 86.6% and the negative predictive value was 99.7%. On daily practice, a junior resident on call with 6 months training in US should not miss this kind of intussusception.
Secondary Intussusceptions: They represent 1.5–12% of AII in children [18]. A majority involve the small bowel only. They can occur at any age but their incidence increases with age. Yet, they may occur in patients younger than 3 months [15]. Many but not all of them will require surgery. A long duration of symptoms, a known underlying disease, and recurrence are important clinical arguments to suspect a pathological lead point; however, the absence of these signs cannot exclude it [19].
Meckel’s diverticulum (MD): The inverted MD will induce an IICI. The presence of mesenteric fat at the tip or around the serosal surface of the intussusceptum is the clue for a US diagnosis. The location of the fat is different from the mesenteric fat which follows the associated invaginated small bowel (Fig. 13.3). This sign has been described as the double target sign [20]. Other findings include the presence within the intussuscipiens of a blind-ending segment of a thick-walled bowel; bowel which has lost its normal gut signature [21]; it may also appear as a thick-walled cystic mass [22].
Duplication cyst: A duplication can be recognized when a cystic mass with a layered wall is present within the intussusception. In theory, the external hypoechoic layer, the muscularis mucosa, is in continuity with the equivalent one of the adjacent bowel loop; this finding being difficult to ascertain within the intussusceptum. The size of the cyst may help to differentiate it from a Meckel’s diverticulum [22]. Spontaneous regressions have been documented [19].
Intestinal tumors:
Polyps (familial polyposis, Peutz-Jeghers syndrome): on US, a polyp may have different patterns and is rarely recognized as such. A clue for diagnosis is the presence of central vessels (in the pedicle) which divides in a branching pattern within a focal mass visible within the intussusceptum [22] (Fig. 13.4).
Lymphoma may present as an intraluminal hypoechoic mass or a hypoechoic irregular thickened bowel wall. Chronicity of clinical symptoms and associated supplementary abnormal findings on US are of great help to propose this diagnosis [22].
Leiomyoma, lipoma, adenoma, Ewing’s tumor are exceptionally involved and do not present typical US signature.
Celiac disease: AII may develop in the course of such disease. It is limited to the small bowel and has a favorable prognosis with spontaneous healing. Dysmotility and mucosal inflammation are considered to be the lead points [23]:
Postoperative: IIA was reported to account for 5–10% of postoperative bowel obstruction [15] and is supposed to be related to altered peristalsis. Most frequent abdominal surgeries involved are Ladd’s procedures and retroperitoneal tumor resection. However, they may occur after non-abdominal surgery as well. AII commonly presents within the first 2 weeks after any surgery and involves exclusively the small bowel and on occasion multiple sites.
Cystic fibrosis: Appendiceal mucocele, dysmotility, and thick inspissated feces may be responsible for intussusceptions.
Henoch–Schönlein Purpura (See also Chap. 29): Intramural hemorrhage and edema within the bowel wall occur during this vasculitis and serve as lead points; the layered bowel wall structure is usually preserved [22]. Hyperemia on color Doppler is present within the wall of the intussusceptum. III is the type most frequently encountered still ICI and even colo-colic intussusceptions have been described [19]. Spontaneous resolution is the rule but exceptionally, perforation may occur [24]. Usually, AII is only one non-specific symptom of the disease which includes skin purpura, arthritis, renal involvement with the risk of renal failure, ureter and/or bladder thickening, scrotal involvement in boys and rarely cholecystitis, pancreatitis, muscular hemorrhagic infiltration, and neurological complications [25].
Upper GI tubes: intussusception may develop secondary to the presence of a feeding tube or gastrostomy. Retrieval of the tube after disinflation of the inflated balloon is usually curative. In case of failure, surgery is required [15].
On occasion, other lesions have been reported to be responsible for AII. The clinical context is sometimes helpful but the final diagnosis needs confirmation by means of biology or histology. This includes: ectopic pancreas, appendicitis, intestinal parasites, neutropenic colitis, Hirschsprung colitis, and foreign body.
Waugh syndrome represents a rare association of ileocolic intussusception and malrotation. Less than 70 cases have been reported and reduction was successful only in a few cases [26].
Fig. 13.4
Colo-colic intussusception secondary to a polyp in a 6-year-old boy: US appearance. (a) Typical target sign of an AII on a transverse scan. (b) Sagittal scan reveals a large pedunculated structure corresponding to a polyp. (c) Identification of the polyp is easier obtain when central vascularization is observed on color Doppler
13.2.5 Search For Signs Predicting Difficult Reduction
Trapped peritoneal fluid between the incarcerated loop and the receiving one is observed in less than 15% of cases [27] and has been described as a highly predictive of bowel necrosis (Fig. 13.5) [28]. However, del-Pozo et al. have shown that 26% of such cases could still be reduced [27] and for Ntoulia et al. it has no impact on the reducibility [29].
Absence or presence of flow on color Doppler in the intussusception is neither indicative of irreducibility nor for a risk of perforation. Kong et al. have shown that 31% of intussusceptions without detectable flow could be reduced by air enema in contrast to a 90% reduction rate when a flow was detectable [6]. On the other hand, color Doppler flow was present in all patients for whom reduction failed in Ntoulia’s series [29].
Thickening of the external bowel wall has a controversial role to predict reduction [30].
Usually, intussusception limited to the small bowel is not candidate for radiological reduction because it may/will disappear spontaneously without interventional treatment. Furthermore, the presence of a lead point renders reduction more hazardous and surgery will be required. However, some authors have proposed to try to reduce them anyway if they are located close to the ileocecal valve even if a lead point has been identified, in order to facilitate subsequent surgery. This should not be attempted when there is evident or potential risk of perforation [19, 31]. The role of the ileocecal valve as a limiting factor in the success of pneumatic reduction in small bowel intussusceptum remains controversial [6, 31].
IICI is more prone to present a lead point and is less easy to reduce [14].Related posts:
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