Acute abdominal pain is one of the most frequent presentations of children visiting emergency departments or outpatient clinics. The differential diagnosis is extensive (Table 40-1). The clinical and radiographic findings are often nonspecific. Appendicitis, gastroenteritis, constipation, trauma, pneumonia, sepsis, toxic ingestion, and hemolytic uremic syndrome are among the conditions that can produce acute abdominal pain in children of all ages. The possibility of Hirschsprung disease, intussusception, and volvulus must be considered in infants with clinical indications of acute abdominal pathology. Intussusception can also occur in preschool children. In older children, testicular torsion and inflammatory bowel disease enter the differential diagnosis. The possibility of tuboovarian disease or ectopic pregnancy needs to be considered in adolescent girls.

Blunt abdominal trauma and penetrating injuries of the abdomen most often lead to solid organ injuries. The spectrum of traumatic pathology includes intraparenchymal contusion, intraparenchymal hematoma, subcapsular hematoma, laceration, fracture, and vascular pedicle injury. CT is generally the imaging modality of choice for evaluating these patients. It provides high sensitivity for the detection of solid organ injuries, characterizes the injury, and determines the severity of hemoperitoneum. Please refer to Chapters 41, 42, 43 and 51 for detailed descriptions of solid organ injuries.¹

Bowel and mesenteric injuries due to abdominal trauma are uncommon, but are potentially life-threatening. Traumatic intestinal lesions include perforation, either intraperitoneal or retroperitoneal, and intramural hematoma. There is often concomitant injury of the mesentery. The diagnosis of GI injury based on the clinical findings alone is often difficult. Substantial hemorrhage is uncommon with these injuries; the intestine is the least common source of hemoperitoneum in patients suffering blunt abdominal trauma. Obstructive symptoms can occur in patients with an intramural hematoma. Patients with trauma-related perforation of the bowel are susceptible to peritonitis, but the clinical manifestations of this complication are often delayed.

The duodenum is the most frequently injured portion of the intestine. This is due to the fixed retroperitoneal position of the duodenum directly over the spine. Because of fixation by the ligament of Treitz, the proximal portion of the jejunum is the next most common site of intestinal injury with blunt trauma in children. In both of these areas, the most common traumatic lesion is hemorrhage, usually intramural. The most common location of a bowel rupture in patients suffering blunt abdominal trauma is in the mid to distal portion of the small intestine. Penetrating injuries can involve any portion of the bowel.

The imaging evaluation of the child who has suffered abdominal trauma begins with supine and decubitus or upright abdominal radiographs. The identification of pneumoperitoneum nearly always indicates the need for emergent laparotomy. Air is occasionally visible in the retroperitoneum in patients suffering a duodenal injury. The gas can collect over the right kidney adjacent to the crus of the diaphragm or adjacent to the leaves of the diaphragm. The radiographic appearance of hemoperitoneum is that of homogeneous soft tissue density in the pelvis and lower portion of the abdomen, due to accumulated blood and displacement of gas-filled bowel. Other potential radiographic findings in patients with intra-abdominal injuries include localized ileus, obliteration of the psoas margins, fractures, and scoliosis due to muscle spasm.²

CT is an essential component of the radiographic evaluation of patients who have experienced substantial abdominal trauma. It is highly sensitive for the detection of extraluminal fluid and air within the peritoneal cavity. The demonstration of even a very small amount of gas in the peritoneal cavity generally indicates the necessity for emergent laparotomy. Pneumoperitoneum is lacking in some patients with bowel rupture, however, as the small bowel predominantly contains fluid. Patients with bowel rupture nearly always have an abnormal accumulation of peritoneal fluid. The CT demonstration of substantial fluid within the peritoneal cavity in a pediatric trauma patient without findings of a solid viscus injury or pelvic fracture is an indication for exploratory laparotomy. In many cases, blood accumulates as a triangular high-attenuation interloop mesenteric fluid collection. Other potential CT findings in patients with bowel rupture include focal discontinuity of the bowel wall, bowel dilation, bowel wall thickening, extravasation of orally administered contrast material, and abnormally prominent bowel wall enhancement (due to peritoneal inflammation) (Figure 40-1).^3–8

The diagnosis of an intramural hematoma can usually be established with radiographic contrast studies, sonography, CT, or MR. Oral contrast administration facilitates the diagnosis on CT studies. With radiographic contrast studies, an intramural hematoma may appear as a localized nodular or smooth mural mass that projects into the bowel lumen (Figure 40-2); this is the most common appearance of a duodenal hematoma. Intramural hemorrhage that elevates, widens, and fixes the mucosa of the bowel often has a “coiled spring” or “stack of coins” appearance on GI contrast studies; this is the most common finding with intramural hemorrhage of the jejunum or ileum. Cross-sectional imaging studies show an intramural hematoma as a mural mass or focus of bowel wall thickening (Figure 40-3). A large hematoma may have a dumbbell configuration. On CT, the hematoma often is slightly hypoattenuating to adjacent enhancing bowel wall (Figure 40-4).^9,10

With blunt trauma, compression of the duodenum against the spinal column can result in a contusion or bowel transection. Rapid deceleration mechanisms in motor vehicle or pedestrian incidents can also cause duodenal injuries. Iatrogenic duodenal perforation and intramural hematoma are potential complications of endoscopy. CT findings suggestive of duodenal injury include retroperitoneal air adjacent to the duodenum, extravasation of oral contrast material into the retroperitoneum, fluid in the retroperitoneum, duodenal wall edema, stranding of peripancreatic fat, and pancreatic transection. On fluoroscopic studies, an intramural hematoma appears as a broad-based filling defect in the contrast-opacified duodenal lumen (Figure 40-2).¹⁰

Traumatic rupture of the diaphragm is an uncommon potential consequence of blunt abdominal trauma (see Chapter 6). The injury is sometimes clinically silent until a bowel complication occurs, such as obstruction or strangulation. Important findings of diaphragmatic rupture on helical CT include diaphragmatic discontinuity, diaphragmatic thickening, segmental nonrecognition of the diaphragm, intrathoracic herniation of abdominal viscera, elevation of the hemidiaphragm, hemothorax, and hemoperitoneum (see Figure 6-15).^11,12

Hypovolemic shock in severely injured children results in characteristic findings on contrast-enhanced CT of the abdomen, termed the hypoperfusion complex (Table 40-2). This finding suggests a tenuous hemodynamic state. The major CT findings of hypoperfusion complex are diffuse dilation of the small intestine with fluid and abnormally intense contrast enhancement of the bowel wall, mesentery, aorta, inferior vena cava, and kidneys. The vena cava is small. There is bowel wall thickening in some patients. The intestine is an uncommon, but important, potential site of injury in children suffering physical abuse. Approximately 20% of fatal instances of child abuse have a visceral injury component. Visceral injuries in these children can occur due to direct blows, rapid deceleration, or penetrating trauma. The most common intestinal injury in child abuse patients is an intramural hematoma, usually within the duodenum. Perforation of the small intestine in association with child abuse involves the duodenum or proximal portion of the jejunum in approximately 90% of cases, and the terminal ileum in 10%.^13,14

There are numerous etiologies of GI bleeding in children. The most common causes of upper GI hemorrhage in children are duodenal ulcers, gastric ulcers, esophagitis, gastritis, and esophageal varices (Table 40-3).¹⁵ Lower GI hemorrhage can occur with a bowel vascular malformation, Meckel diverticulum, intussusception, or typhlitis (Table 40-4). The differential diagnosis of GI hemorrhage varies with the age of the patient. Considerations in the differential diagnosis for neonates with clinical signs of GI hemorrhage are noted in Table 40-5. Radiological techniques serve to define the underlying pathology, localize the bleeding site, and intervene to control the hemorrhage. Barium studies, CT, MRI, and ultrasound serve roles in identifying the underlying pathology. Localization of the bleeding site can be achieved with scintigraphy or angiography. Transcatheter therapy with embolization or intraarterial vasopressin infusion is indicated in selected cases.^16–18