Any abdominal tumor may compress the intestine and cause obstruction but Burkitt’s lymphoma in particular is known for its close relation to the intestinal tract. Burkitt’s lymphoma, a type of non-Hodgkin-lymphoma, is most frequently located in the abdomen. In 25% of cases the tumor is situated at the ileocecal junction, especially in children under 16 years, most likely because of the high concentration of lymphoid tissue in the terminal ileum [19, 20]. The typical clinical presentation is that of abdominal pain and/or a mass in the right lower quadrant. On imaging studies, the intestinal wall may appear locally thickened and hypoechoic and the intestinal wall structure may appear unclear [22] (Fig. 27.2a, b). Ascites is often present. Burkitt’s lymphoma is a rare but well-known pathological lead point for acute intestinal intussusception (AII) and abdominal pain may be related to that complication. A history of weight loss and a longer duration of symptoms (abdominal pain, vomiting, and intestinal bleeding) are important clinical indications of lymphoma [21]. A lobulated (hypoechoic on US) mass is seen in the intussusceptum (Fig. 27.3a, b); At the end of a therapeutic enema, a mass will typically persist.

Colorectal carcinoma (CRC) is the most common primary GI tumor in children and adolescents, although extremely rare (1% of pediatric neoplasms) [22]. Presenting symptoms are abdominal pain, often cramping, bowel movement changes, rectal bleeding, nausea and/or vomiting, weight loss, and sometimes acute bowel obstruction [23]. The lack of specificity of the symptoms and the low diagnostic suspicion for cancer in children and particularly this type of cancer, frequently account for a delay in diagnosis. The poorer prognosis in young patients is related to this diagnostic delay as well as to the high incidence of poorly differentiated aggressive tumors. Children more frequently present with a more advanced stage (stage 3 and 4) and frequently have nodal involvement at diagnosis compared to adults [23, 24]. Predisposing factors like familial adenomatous polyposis (FAP), inflammatory bowel disease (IBD), and Peutz-Jeghers syndrome are reported in only 10–30% [25]. The same genes and genetic pathways are found as in adult patients but overall the cancer biology is more aggressive [26]. Features of CRC on CT and MRI include focal or circumferential bowel wall thickening and luminal narrowing [27] (Fig. 27.4a–c). The final diagnosis is established with endoscopy and surgical biopsy or resection and histopathology examination.

Neutropenic colitis or typhlitis is a necrotizing infection occurring almost only in cancer patients. It is related to prolonged granulocytopenia and therefore most commonly encountered in patients with acute leukemia although any patient with neutropenia is at risk. In pediatric oncology patients, the reported incidence is between 0.5–6.7% and children above 16 years seem more prone to develop typhlitis [28, 29]. It is characterized by a classical triad of abdominal pain, fever (although fever may be absent in the early stage of this complication), and neutropenia, and the diagnosis is confirmed by thickening of the bowel wall (≥3 mm) on imaging studies (Fig. 27.5a). Other common symptoms are abdominal tenderness, often localized in the right iliac fossa, vomiting, nausea, and constipation. The cecum and right colon are classically involved but McCarville et al. found the transverse colon and descending colon or rectum to be involved in 40% of a cohort of pediatric cancer patients [28] (Fig. 27.5b). Bowel wall thickness can be evaluated very accurately with high frequency US transducers, hence it is a reliable technique for detecting typhlitis. The treatment of choice is medical, with broad-spectrum antibiotics, granulocyte colony-stimulating factor, and total parenteral nutrition [30]. Surgery is required when typhlitis is complicated by perforation, uncontrolled sepsis, and GI bleeding [31]. In the latter, an interventional radiology procedure can also be attempted [32].

Imaging is required whenever a mechanical obstruction needs to be excluded as a cause for jaundice (see Chap. 15). The most common cause of neoplastic biliary obstruction in childhood is embryonal rhabdomyosarcoma (RMS) of the biliary tree, accounting for 1% of all RMS [33]. It is a very rare tumor occurring in young children (median age 3 years) that obstructs the biliary system and usually presents with isolated jaundice [33, 34]. The tumor may arise in the liver parenchyma, in all parts of the biliary tree or within a choledochal cyst [35–38]. Differentiation from a choledochal cyst may at times be an issue: several case reports describe a biliary RMS mistaken for a choledochal cyst, which is a much more common cause of jaundice in a young child [39, 40]. With imaging, an intraductal mass is seen as well as the associated dilatation of the intrahepatic bile ducts (Fig. 27.6a, b). The enhancement pattern on CT is variable. On MRI, the tumor is usually predominantly hypointense on T1-weighted images and shows intense but inhomogeneous contrast enhancement [41]. The tumor is hyperintense on T2-weighted images and shows diffusion restriction (Fig. 27.6c–g). MR cholangiography can be performed in the same session. At percutaneous transhepatic cholangiography (PTC) and endoscopic retrograde cholangiopancreatography (ERCP), the ductal tumor is shown as filling defects with or without obstruction of the extrahepatic bile ducts (Fig. 27.6h) [35, 42]. The most common primary liver tumor in older children, hepatocellular carcinoma (HCC), very rarely presents with jaundice. Primary pancreatic tumors seldom present with jaundice but certain tumors that may invade the pancreas such as PNET, sarcoma or Burkitt’s lymphoma may cause obstructive jaundice [43, 44] (Fig. 27.7a, b).

Veno-occlusive disease (VOD), currently also known as hepatic sinusoidal obstruction syndrome (HSOS), is a serious, potentially life-threatening complication. It most commonly occurs after high dose chemotherapy in a context of hematopoietic stem cell transplantation (HSCT), with an incidence of 10–20% in children [45]. A milder form that usually resolves spontaneously occurs less frequently in patients receiving conventional chemotherapy [46–48]. Hepatic venous microvasculature is damaged and obliterated which leads to decreased liver outflow, causing portal hypertension. Clinically, patients present with weight gain, fluid retention and ascites, painful hepatomegaly and jaundice. Laboratory findings are nonspecific. A reliable predictive diagnostic test is still lacking although according to recent publications, an increase in maximum systolic velocity of the hepatic artery and an increase in liver stiffness evaluated by transient elastography might be early findings of VOD in children [49–51].

Primary and secondary malignancies are uncommon causes of hepatomegaly in neonates and children. They may present as a life-threatening condition with respiratory distress and require an emergency workup and subsequent treatment. Cellular infiltration as a cause of hepatomegaly can be due to primary malignant tumors of the liver, mainly hepatoblastoma and HCC or metastatic disease. Hepatoblastoma is the most frequent malignant liver tumor of young children. The patients are younger than 5 years of age in 90% of the patients. Hepatoblastoma is usually solitary but in 20% of patients it is multifocal. HCC is the most frequent primary hepatic tumor of older children and adolescents. Primary hepatic malignancies in children usually present with progressive abdominal distension, hepatomegaly, or with an asymptomatic abdominal mass [34]. Alpha-fetoprotein (AFP) is strongly elevated in 90% of patients with hepatoblastoma, which makes it a very useful marker.

Diffuse metastatic infiltration can be seen in leukemia, lymphoma, and neuroblastoma. Liver infiltration is common in an advanced stage of neuroblastoma (stage 4) but is also part of a particular phenotype, stage 4S, with a favorable outcome and a usually spontaneously regressing small primary tumor. (Criteria necessary to meet with this particular stage are age below 1 year, dissemination limited to skin, liver, and/or bone marrow (and involvement of less than 10% of total nucleated cells) and metaiodobenzylguanidine (MIBG) scan negative for bone marrow [52]. Hepatomegaly, which is at times extensive, is often the presenting symptom. On US the liver contains multiple round isoechoic tumors surrounded by a hypoechoic rim (Fig. 27.8a) and on MRI the liver shows nodular infiltration (Fig. 27.8c–e). The metastases tend to hypoenhance compared to the liver parenchyma on CE-CT and post-Gd MRI. The primary tumor is usually small, sometimes calcified (Fig. 27.8b). Urine should be tested for elevated catecholamine levels and if necessary a MIBG-scan must be performed, to confirm neuroblastoma. In infants, on occasion, diffuse hepatic hemangiomatosis may mimic metastatic infiltration from neuroblastoma. A decreasing diameter of the abdominal aorta below the celiac trunk and a large hepatic artery are suggestive of infantile liver hemangiomas as well as the hyperenhancing pattern (see also Chaps. 8 and 15).

A large number of chemotherapeutic drugs may induce pancreatitis in children. The drugs used in the treatment of acute lymphoblastic leukemia, doxorubicin, vincristine, prednisolone, and L-asparaginase in particular are known to cause pancreatitis [53]. L-asparaginase may even lead to severe necrotic pancreatitis [54]. Diffuse enlargement of the pancreas as well as peri-pancreatic fat streaking and fluid collections is seen on all imaging modalities (Fig. 27.9a, b). High blood levels of amylase and lipase confirm the diagnosis. Burkitt’s lymphoma very rarely presents with pancreatitis [44].