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Diseases in Older Children 5.7.1

Small Bowel Intussusception

Intussusceptions are a pediatric GI emergency, most being ileocolic. Small bowel intussusceptions are less frequently diagnosed, but if searched for carefully, are relatively frequently encountered. Mostly these small bowel intussusceptions are also idio-pathic and transient and of no clinical importance. Pathologic entities that might predispose a child to small bowel intussusception that can be clinically significant are infection, malabsorption syndromes, gastroenteritis with increased peristaltic activity of small bowel, lymphoma, cystic fibrosis, intramural hematomata (Henoch-Schonlein, posttraumatic), polyps, Meckel diverticulum, duplication, foreign body and adhesions.

Small bowel intussusceptions can be found incidentally when searching for other pathology, in which case patients will have no complaints.

Otherwise patients can present with transient cramping abdominal pain or with persistent abdominal pain, or even with symptoms of obstruction.

On sonography (Fig. 5.17) an intraluminal mass with a layered appearance may be seen. It can be seen to intussuscept and de-intussuscept, can have the 'pseudo-kidney' or 'donut' appearance and occasionally the lead point can be determined. CT (Fig.5.19c) findings correlate with the findings described for sonography. A layered or target

Intussusception Pseudo Kidney Ultrasound

Fig. 5.17. a Transient small bowel intussusception. The intra-luminal mass with layered appearance is the small bowel. b Small bowel (jejunal) intussusception caused by a bezoar

Fig. 5.17. a Transient small bowel intussusception. The intra-luminal mass with layered appearance is the small bowel. b Small bowel (jejunal) intussusception caused by a bezoar appearance of the mass, fat within the mass, particularly if in continuity with mesenteric fat and mesenteric vessels entering the mass, are features suggestive of intussusception. Both on sonography and CT a crescent of gas or fluid may separate the mass (the intussusceptum) from the adjacent small bowel (the intussuscipiens).

Idiopathic, transient small bowel intussusceptions need no treatment. The transient nature of the small bowel intussusception will be confirmed by reinvestigation of the small bowel, preferably by sonography, after a few minutes or hours. The intussusception will in most cases have then disappeared (ParkEr 2003; StrousE et al. 2003).

5.7.2 Ileus

Acquired ileus, encountered in older children or even infants, can be paralytic (adynamic) or obstructive (mechanical).

Paralytic ileus, due to intrinsic abnormalities of the bowel wall, can be caused for example by drugs, after laparotomy, sepsis or peritonitis. Obstructive ileus is most often due to extrinsic causes, for example adhesions (in 70% of cases), incarcerated hernia, small bowel wall hematoma posttraumatic, neoplasms, Crohn disease and intussusception (Parker 2003; Devos and Meradji 2003). Clinically the child has a distended and tender abdomen with failure to pass stools or no defecation and possibly (bilious) vomiting.

Imaging can indicate location, degree, and cause of obstruction and assess for the presence of ischemia.

Plain films remain the first line of imaging. CT is used increasingly because it provides essential diagnostic information not apparent on plain radiographs.

In paralytic ileus supine radiographs of the abdomen will show both dilated small bowel loops and colon, whereas in obstructive ileus usually only the loops proximal to the obstruction are dilated and those distal have a reduced caliber. The closer to the obstruction, the more the loops are dilated. Air-

fluid levels on horizontal beam films can be seen in both types of ileus, but in case of obstructive ileus air-fluid levels are concentrated in the dilated loops (Figs. 5.18 and 5.19).

In the acute setting and with clinical symptoms such as (bilious) vomiting and the inability to drink contrast, studies such as a GI tract series and/or enteroclysis are usually not indicated.

Sonography may show dilated fluid-filled bowel loops. The obstructing cause can occasionally be visualized if it is a tumor or hernia. Absence of peristaltic movements, bowel wall thickening without perfusion on color Doppler imaging and dilated small bowel containing fluid can all indicate infarction in the appropriate clinical setting.

CT can be used to distinguish between paralytic (Fig. 5.19) and obstructive ileus or to localize the obstruction but should not be used routinely and care needs to be taken to minimize total radiation dose. Other advantages include the fact that no oral contrast material is needed as the retained intraluminal fluid serves as a natural (negative) contrast agent. It is a rapid, non-invasive, readily available technique with which also extralumi-nal pathology can be visualized. CT images of an obstructive ileus will identify dilated bowel loops proximally with normal caliber or collapsed loops distally. Sometimes the transition zone, which may resemble a beak, can be identified. This CT sign,

Fig. 5.19. a,b Paralytic ileus. Note the extremely dilated small bowel loops and also the colonic loops containing gas and fluid levels. c CT image shows multiple dilated loops of almost equal caliber: indicative of paralytic ileus. Arrow indicates small bowel intussusception

among others, is well described by Nicolaou et al. (2005). They also describe the so-called 'string-of-pearl' sign and small-bowel-faeces sign. The string-of-pearl sign is caused by slow resorption of intraluminal air leaving small bubbles trapped between the folds of the valvulae conniventes. The small-bowel-faeces sign results from stasis and mixing of small bowel content. Signs associated with ischemia include thickened bowel wall, ascites, the 'target' sign which refers to the trilaminar appearance of the bowel wall after IV contrast injection, poor or absent contrast enhancement of the bowel wall after IV injection, pneumatosis intestinalis and gas in mesenteric or portal veins, the 'whirl-pool' sign caused by twisting of the mes-enteric vasculature around itself caused by a volvulus, tortuous engorged mesenteric vessels, mes-enteric hemorrhage, and increased attenuation of bowel wall on non-contrast scans (Nicolaou et al. 2005; Boudiaf et al. 2001).

5.7.3 Tumors

Tumors of the small intestine are rare in children and with the exception of the pre-malignant polyposis syndromes, such as Gardner syndrome and Peutz-Jeghers syndrome, a malignant lesion of the small bowel in children is extremely rare.

Benign small bowel neoplasms are often associated with multi-organ syndromes such as Osler-Weber-Rendu (telangiectatic arteriovenous fistu-

lae), Klippel-Trenaunay-Weber (solitary or multiple haemangiomas) or neurofibromas.

Benign mesenchymal lesions such as lipomas, fibromas and leiomyomas may also occur.

Any of these tend to present with symptoms of abdominal pain or obstruction, sometimes due to intussusception (Carty et al. 2005; Parker 2003).

Plain film is usually unremarkable. Diagnosis may be made with contrast studies. These may reveal polypoid filling defects or a classic intussusceptum.

US distinguishes solid from cystic lesions, and may reveal the polyps as intraluminal, floating lesions that are hyperechogenic, due to the mucosal secretions, and may be nodular or tubular structures. The so-called 'target' configuration on US is caused by the echogenic center that represents the polyp and the surrounding hypoechogenic region, which is the fluid collection in the dilated loops (Fig. 5.20).

CT and MRI can also reveal polyps, but the small bowel should then be filled with enough intralumi-nal contrast material that surrounds the polyps.

Malignant tumors of the small bowel in children, other than non-Hodgkin lymphoma, usually the B-cell Burkitt lymphoma, are exceedingly rare. Burkitt lymphoma can develop at any age, but is most common in children under the age of 8 years and then predominantly in males. It is a very fast growing non-Hodgkin lymphoma that originates from B-lymphocytes with a predilection for abdominal organs, particularly the distal ileum. Large numbers of lymphoma cells may accumulate in mesenterial lymph nodes. Over the age of 4 years it is the most

Fig. 5.21. a Burkitt lymphoma. Note the hypoechoic mass located in the ileum wall. b Burkitt lymphoma of the small bowel wall with visualization of air (hyperechogenic band) containing small bowel loop. c,d Burkitt lymphoma as a hypodense, contrast enhancing mass in the ileum. Dilated neighboring loops

Fig. 5.21. a Burkitt lymphoma. Note the hypoechoic mass located in the ileum wall. b Burkitt lymphoma of the small bowel wall with visualization of air (hyperechogenic band) containing small bowel loop. c,d Burkitt lymphoma as a hypodense, contrast enhancing mass in the ileum. Dilated neighboring loops

Burkitt Lymphoma Blood Film

common lead point in children with ileocolic intussusception. Burkitt lymphoma metastasizes often to bone marrow, blood and central nervous system (Parker 2003; Husband and Reznek 2004).

Patient complaints include loss of appetite, vomiting, abdominal pain, obstipation, GI bleeding or a palpable mass in the right lower quadrant.

Plain films may be normal or show signs of obstruction. This may include so-called aneurysmal dilatation, better appreciated on contrast studies as polypoid enlargement/thickening of the mucosal folds. Sometimes a mass in the right lower quadrant can be detected.

Ultrasound may show a hypoechoic or anechoic mass, localized eccentrically in the ileum of which the lumen is frequently dilated (Fig. 5.21a). Enlarged mesenterial lymph nodes and sometimes ascites may be seen.

CT and MRI may show infiltration of the bowel wall, dilatation of the lumen, sometimes ascites and enlarged mesenteric lymph nodes (Fig. 5.21b).

Unusual tumors in childhood also include the malignant counterparts of lipomas, fibromas, neu-rofibromas and leiomyomas (Parker 2003).

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