A wide variety of bowel diseases, may manifest with intestinal wall thickening at computed tomography (CT). • Common causes of bowel wall thickening include edema, hemorrhage, infection, graft-versus-host disease, and inflammatory bowel disease; • more unusual causes includimmunodeficiencies, lymphoma, hemangioma, pseudotumor, and Langerhans cell histiocytosis.
CT is an increasingly useful technique in the evaluation of intestinal disease, allowing the evaluation of bowel disease as well as extraintestinal disease • (eg, adenopathy, ascites, fat stranding, presence of abscesses and fistulas) and improves specificity in diagnosis
The faster scanning times made possible by multidetector (spiral) technology decrease the need for sedation in children. • we currently use a 16-detector CT scanner. We obtain 5-mm-thick axial images that are routinely retrospectively reformatted in the coronal plane. • If the patient is less than 6 months old, we obtain 3.75-mm-thick axial images. • All images are acquired after the oral and intravenous administration of contrast material, with no routine acquisition of delayed images. • Oral contrast administrataccounts for the 40–45 minutes just prior to the actual scanning.
. • At our institution, iohexol (Omnipaque); is offered initially to children. Besides being nonionic, iohexol is tasteless and has a thinner consistency, increasing patient compliance. In addition, we have noticed a faster transit time, yielding better enhancement of more distal portions of the colon and sometimes even of the rectum. • When there is a history of iodine allergy, the child is offered flavored barium suspension.( Volumen (0.1% barium suspension)) We also use cold water as a negative contrast agent more frequently in children who refuse other oral contrast agents and when the evaluation of the mucosa is most important, such as in graft-versus-host disease (GVHD) and vasculitis. • the use of a negative contrast agent has few disadvantages. Such agents limit the examination when fistulous tracts or intramural accumulation of contrast material is present. In cases of acute appendicitis,
. CT scan obtained with intravenous contrast material and with water as a negative oral contrast agent gives a false impression of mild wall thickening of the jejunum (arrow).
Bowel Characterization • Some authors have described the normal bowel wall thickness in adults as 1–2 mm when the lumen is distended. Colonic wall thickness is more dependent on distention and intraluminal contents than is small bowel wall thickness. When distended, the colonic wall is often imperceptible . • To our knowledge, there are no published standards of normal bowel wall thickness in children. As a practical general rule, the bowel wall should be barely perceptible when adequately distended. • When a peristaltic loop is imaged, transient wall thickening is present, usually posing no diagnostic dilemma at CT.
CT scan obtained with oral and intravenous contrast material shows poor distention of the cecum (arrow), a finding that simulates bowel wall thickening. There is evidence of seat belt injury in the anterior abdominal wall. (b) Delayed CT scan obtained with oral contrast material shows adequate distention of the cecum
Distribution of the wall thickening is a critical finding, since several diseases follow a well-established pattern and others affect either the small bowel, the large bowel, or both. • The distribution may be: focal (only a few centimeters), segmental (usually a few bowel loops), diffuse (either the entire small bowel or large bowel), or universal (the entire small and large bowel).
Some diseases demonstrate a specific pattern of wall thickening: • Eccentric involvement is more commonly seen with tumors, either benign or malignant, whereas • circumferential thickening tends to occur with inflammatory conditions and infections. One exception to this rule is the “apple core” sign, which represents luminal narrowing resulting from focal circumferential wall thickening of the bowel. This sign is most commonly but not exclusively associated with colonic adenocarcinoma.
Several patterns of wall attenuation • . A hyperattenuating wall is seen with hemorrhage as a result of trauma, purpura, or vasculitis. • A submucosal fatty “halo” has been described as a result of chronic inflammation, such as in inflammatory bowel disease and GVHD. A fatty halo has also been reported in asymptomatic obese patients . • The term pneumatosisrefers to air in the bowel wall. may have a different appearance, depending on whether it is submucosal or subserosal; the former is bubbly or cystic in appearance and the latter is curvilinear. • pneumatosis in children has been associated with rotavirus gastroenteritis, bowel obstruction such as pyloric stenosis and meconium ileus, accidental and nonaccidental trauma, steroids, chemotherapy, and organ transplantation. Cystic fibrosis and asthma may also result in pneumatosis . A significant number of cases have underlying risk factors, most commonly related to immunosuppression.
A submucosal fatty “halo” has been described as a result of chronic inflammation, such as in inflammatory bowel disease and GVHD. A fatty halo has also been reported in asymptomatic obese patients .
The termpneumatosisrefers to air in the bowel wall. Intramural gas may have a different appearance, depending on whether it is submucosal or subserosal; the former is bubbly or cystic in appearance and the latter is curvilinear. Pneumatosis is an imaging finding and not a diagnosis Pneumatosis in a patient with a history of bone marrow transplantation who was receiving steroids. CT scan (bone window) demonstrates linear subserosal mural air
Submucosal edema is definitive evidence of bowel wall injury (typically acute), often producing the “target” sign . • Mural stratification is due to hypoattenuatingsubmucosal edema, with the enhancing hyperattenuating inner and outer layers of the target representing the mucosa and muscularispropria–serosa, respectively .
The “accordion” sign is caused by contrast material trapped between thickened edematous haustral folds in the colon . Although the accordion sign is most commonly seen in pseudomembranous colitis, it is not pathognomonic for this disease .
The “comb” sign represents hypervascular engorged vasa recta aligned like the teeth of a comb on the mesenteric site of the bowel. • This finding is classically seen in inflammatory bowel disease, especially Crohn disease, and suggests a clinically active disease. The comb sign can also be seen in vasculitis and purpura
The “toothpaste” or “lead pipe” sign has been associated with chronic diseases leading to a “featureless” bowel. • It is commonly seen with Crohn disease or chronic GVHD or as the sequela of radiation therapy.
Bowel Diseases • Infection • Gastroenteritis and colitis are probably the most common causes of bowel wall thickening and are usually diagnosed clinically. Occasionally, however, they are identified at CT, either incidentally or as an atypical manifestation. • Some bacterial causes include Escherichia coli, Shigella, Salmonella, Yersinia, Campylobacter, and Staphylococcus. Viral causes include Rotavirus, Herpes, and Cytomegalovirus. Rotavirus is a very common cause of gastroenteritis in infants and children. It most often affects children between 6 months and 2 years of age during the winter months. Parasitic infections such as amebiasis are more common in underdeveloped countries.
The segment of the colon involved may suggest a specific diagnosis. • Most of the bacterial colitides tend to involve the right colon. • Certain ancillary signs such as lymphadenopathy and splenomegaly suggest Salmonella. • Diffuse involvement suggests E coli or Cytomegalovirus. • The rectosigmoid colon tends to be involved with Herpes, Neisseria gonorrhoeae , • Treponemapallidum as part of the so-called gay bowel syndrome . The patient’s sexual history is critical in suggesting the diagnosis .
Gay bowel syndrome in a homosexual teenager. CT scan obtained with oral and intravenous contrast material shows segmental wall thickening of the sigmoid colon (arrow). Herpes simplex infection was confirmed at biopsy.
Pseudomembranous results from toxins produced by an overgrowth of Clostridium difficile , most often but not exclusively associated with antibiotic therapy. ( commonly clindamycin,) . CT findings include: extreme segmental or diffuse wall thickening, either confined to a segment or involving the entire colon . The so-called accordion sign is suggestive of but not pathognomonic for this entity and is usually seen in advanced cases . Typically, no significant pericolonic fat stranding is seen.
E coli Infection.: in children may result in hemolytic uremic syndrome. That is triggered by an infection that induces an autoimmune response characterized by a microangiopathic hemolytic anemia, thrombocytopenia, and renal failure. most common cause of acute renal failure in children. The cecum and ascending colon are the most commonly involved areas. CT findings include mural stratification, narrowing of the bowel lumen, and pericolonic fat stranding . Colonic ischemia and perforation are well-known complications.
Trauma • The duodenum and small bowel are commonly injured after trauma. • Typically, duodenal hematomas are intramural, involving the second or third portion of the duodenum . The characteristic finding is an eccentric mass protruding into the bowel lumen and causing varying degrees of obstruction. • The attenuation of the mass varies according to the time of trauma; in acute trauma, the mass tends to be slightly hyperattenuating. In focal or segmental small bowel hematomas, more pronounced and localized enhancing wall thickening is usually present . • A careful search for signs of perforation, mesenteric and abdominal wall hematomas, and spinal fractures must be performed.
Duodenal hematoma marked focal duodenal wall thickening (arrow). Free fluid and fat stranding are seen in the right paracolic gutter (arrowhead) and anterior abdomen. Jejunal hematoma. diffuse concentric jejunal wall thickening with associated abnormal enhancement (arrowhead) and hemoperitoneum (curved arrow).
Hypoperfusion complex–shock bowel syndrome : is the manifestation of a tenuous hemodynamic instability, usually secondary to trauma even after aggressive resuscitation efforts with intravenous fluid. It is seen predominantly in infants and young children. CT findings: dilated and fluid-filled small bowel loops with sparing of the colon. . In more severe cases, an abnormal intense parenchymal enhancement of solid organs such as the kidneys and adrenal glands, a small-caliber aorta, and a collapsed inferior vena cava are present .
Lymphoma.— Primary gastrointestinal lymphoma is most frequently of B-cell origin, predominantly of the non-Hodgkin type. Secondary bowel involvement from generalized lymphomas is more common than primary lymphoma. The appearances of T-cell lymphomas of the bowel include plaques, mucosal ulceration, and strictures, whereas B-cell type lymphoma manifests as polypoid masses or eccentric wall thickening. Aneurysmal dilatation. . Both the small bowel and colon are involved; however, B-cell lymphomas tend to affect the distal ileum, whereas T-cell types affect the duodenum and jejunum.
large, low-attenuation eccentric mass with intense peripheral enhancement (arrow) arising from the second portion of the duodenum. Gastrointestinal Stromal Tumors.— the most common mesenchymal neoplasms of the gastrointestinal tract. The most common site of involvement is the stomach, followed by the small intestine, anorectum, colon, and esophagus. Gastrointestinal bleeding due to mucosal ulceration is usually the presenting sign. These tumors arise from the muscularispropria, typically manifesting as an eccentric well-circumscribed mass, occasionally with a hypoattenuating center representing cystic degeneration or necrosis .
Gastrointestinal stromal tumor. Consecutive CT scans obtained with oral and intravenous contrast material show a large, low-attenuation eccentric mass with intense peripheral enhancement (arrow) arising from the second portion of the duodenum.
Neurogenic Tumors. One example of a neurogenic tumor is a mesenteric plexiformneurofibroma associated with neurofibromatosis. Mesenteric neurofibromas are very rare but should be suspected if a mesenteric mass is seen with or without wall thickening of the small or large bowel in a patient with neurofibromatosis . The diagnosis is usually suggested when multiple neurofibromas are identified elsewhere in the body. . Mesenteric neurofibroma in a patient with neurofibromatosis type I. moderate concentric cecal wall thickening (arrowhead), with an adjacent lobulated soft-tissue mass (arrow) that represents a mesenteric neurofibroma.
Vascular Tumors.— Most hemangiomas are pedunculated, intraluminal polypoid lesions; occasionally, they may have an infiltrative growth pattern. If there is diffuse involvement, the term hemangiomatosis should be used. The small bowel is the most commonly affected site, with jejunal predominance. CT findings include diffuse infiltration of the intestinal wall with mural thickening and occasional phleboliths. A hyperattenuating, markedly enhancing bowel wall is a classic finding that is better seen when a negative oral contrast agent such as water is used (.
Colon Cancer Arising from the mucosa, adenocarcinoma of the colon is rare in the pediatric age. The transverse colon and the rectosigmoidare the two most commonly affected sites. Children with a family history of colon cancer, chronic ulcerative colitis, or familial polyposis syndromes are at greater risk. Imaging findings do not differ from those encountered in the adult population, with radiologic features including polypoid, ulcerative, annular constricting (apple core sign) , and scirrhous carcinomas. The complications of colon cancer include bowel obstruction, intussusception (polypoid lesions), perforation, local recurrence, and peritoneal spread .
Langerhans Cell Histiocytosis. most commonly affects the terminal ileum, producing diarrhea, protein-losing enteropathy, and malabsorption . Colonic involvement has also been reported .
Other causes of small bowel wall thickening related to malabsorption syndromes include celiac disease and lactose intolerance. • In addition, hypoproteinemia may be seen involving the wall of the gastrointestinal tract, most commonly the small bowel. Hypoproteinemia causes diffuse, hypoattenuating wall thickening with prominence of the folds and, in more severe cases, ascites. In children, it is commonly seen in nephrotic syndrome and renal failure from various causes.
Hypoproteinemia in a patient with chronic renal failure. CT scan shows concentric wall thickening of the jejunum (arrow). Multiple cysts are incidentally seen in the atrophic right kidney (arrowhead).
Inflammatory Bowel Disease.— • . Approximately 25% of cases of Crohn disease and 20% of cases of ulcerative colitis occur in children Ulcerative colitis usually starts during adolescence). • Crohn disease more frequently involves the terminal ileum and the right colon/ degree of wall thickening is significantly COMB SIGN/ Wall thickening is usually eccentric on the mesenteric side, with pseudodiverticulum formation on the antimesenteric side/ Frequently, there are skipped areas /abscess&fistula/ • ulcerative colitis: , right colonic involvement /. the terminal ileum may be involved in ulcerative colitis due to “backwash ileitis,/ usually wallthikness circumferential and continuous /. Pseudopolyps are a feature when more extensive ulceration of the mucosa and submucosa develops and only scattered islands of normal mucosa /remain/ Pseudopolyps are characteristic of active disease/. Abscess and fistula are not seen /. • A halo of fat in the bowel wall is seen in chronic inflammatory bowel disease, more commonly in ulcerative colitis.
Crohn disease. (a) CT scan shows wall thickening of the transverse colon with mural stratification (arrow). The engorged pericolonic vessels (arrowhead) are suggestive of active disease. Mild pericolonicfibrofatty proliferation is also present. (b) CT scan shows marked wall thickening of the descending colon, cecum, and terminal ileum (arrowheads), findings that indicate diffuse colonic involvement
Pseudodiverticulum in a patient with Crohn disease. CT scan show pseudodiverticulum (arrow) at the antimesenteric side of a small bowel loop secondary to Crohn disease. Circumferential and eccentric mural thickening of the same loop is also present. (b) Image from a small bowel series helps confirm the presence of a pseudodiverticulum (arrow). A segmental ileal stricture and separation of loops due to fibrofatty proliferation are also noted.
Pseudopolyps in a patient with proved ulcerative colitis. CTshows nodular circumferential concentric thickening of the descending colon with pseudopolyp formation (arrow). (b) Image from a barium enema examination helps confirm the presence of pseudopolyps (arrow) in the distal transverse and descending colon
Ulcerative colitis. CT scan shows diffuse circumferential concentric wall thickening of the colon (arrows). Mild associated fibrofatty proliferation of the mesentery is seen in the right side of the abdomen.
Typhlitis. refers to the inflammation of the cecum often seen in immunosuppressed or neutropenic patients, usually after bone marrow transplantation. The cause is unknown but is probably multifactorial (ischemia, infection [especially cytomegalovirus], mucosal hemorrhage, and even neoplasm) . CT is the study of choice due to the commonly associated bowel dilatation and the increased risk of perforation. The cecum is usually distended, with circumferential wall thickening . Pericecal fat stranding tends to be severe.
Inflammatory Pseudotumor.: consists of inflammatory and myo-fibroblastic spindle cells and may involve virtually any site in the body, most commonly the orbit and lung. Because inflammatory pseudotumor can mimic a malignancy both clinically and radiologically, In the gastrointestinal tract, ileocecal and gastric lesions are most frequently reported in young girls. At CT, pseudotumor manifests as a mass that is hypo- or isoattenuating relative to muscle. A mild degree of enhancement is usually present. Pseudotumor can produce bowel wall in-filtration, which manifests as focal circumferential wall thickening (apple core sign), and adjacent fat stranding . Mural calcifications have also been reported .
Autoimmune Causes • Autoimmune causes include collagen vascular disease and vasculitis, immunodeficiencies, and GVHD. Food allergies with gastrointestinal manifestations frequently diagnosed in children are included in this category
Collagen Vascular Disease • The small bowel is more commonly affected, usually in a concentric, segmental, or diffuse pattern . • Among the collagen vascular diseases, systemic lupus erythematosus and scleroderma are the most common causes of bowel disease, whereas periarteritisnodosa and Henoch-Schönleinpurpura are the most common vasculitides. • CT is very helpful in identifying other supportive signs of systemic involvement that are commonly associated with collagen vascular disease, such as polyserositis, renal involvement, or hepatosplenomegaly.
Systemic lupus erythematosus. (a) CT scan obtained shows thickened folds in the proximal jejunum (arrowhead). The peripheral cortical hypoattenuating area in the right kidney (arrow) represents a small infarct. (b) CT scan obtained shows diffuse wall thickening throughout the jejunum (arrow) secondary to active vasculitis.
Henoch-Schönleinpurpura • usually manifests with abdominal pain due to edema and intramural hemorrhage, • The radiologist may be the first to suggest the diagnosis. Gastrointestinal involvement occurs in more than 50% of affected patients. • CT findings include multifocal bowel wall thickening with skipped areas , hyperattenuating bowel wall due to hemorrhage, bowel dilatation due to localized ileus, vascular engorgement (comb sign), and mesenteric edema. • The presence of skipped areas may help differentiate Henoch-Schönleinpurpura from other types of vasculitis . • complications including intussusception, bowel ischemia, or perforation may be seen
.Henoch-Schönleinpurpura. (a) CT scan shows diffuse hyperattenuating concentric wall thickening of the jejunum (arrow) and ascites (arrowhead). No perforation was confirmed. (b) CT scan shows diffuse hyperattenuating concentric wall thickening of a more distal jejunal loop (arrow), a finding that indicates the presence of skipped areas. Ascites is also seen (arrowhead).
Graft-versus-Host Disease.—GVHD • is a complication of allogenic bone marrow transplantation when the donor lymphocytes in the9it mount an immunologic attack against the host. • The skin, gastrointestinal tract, and liver are the organs most commonly affected • A negative oral contrast agent should be the contrast material of choice in suspected cases of GVHD; such a contrast agent may make the commonly seen hyperattenuating mucosa more conspicuous. • The CT findings may vary depending on the age of the process. Both the large and small bowel are involved, with the distal ileum most commonly affected. Varying degrees of concentric wall thickening with a hyperattenuating enhancing mucosa are seen . Prolonged coating of the bowel with oral contrast material is occasionally present, since the contrast material is incorporated into the submucosal layer through mucosal ulcers. • This finding can also be seen with ischemia. • Ascites and perienteric fat stranding can be seen in the acute setting. • The presence of a stricture, a featureless segment of bowel, the so-called toothpaste appearance (also called moulage), or fibrofatty proliferation favors a chronic process .