In adults, the indications for abdominal radiography have dramatically decreased, as it has been largely if not completely replaced by CT. This is not the case in pediatric radiology where abdominal radiographs are still indicated in (1) Intestinal obstruction; (2) Ingested foreign body or suspected intraabdominal calcification; (3) Suspected perforation. Of note, in children, abdominal radiographs should not be performed to investigate chronic abdominal pain or constipation.

Abdominal radiographs can be limited to one supine film in most cases. In children, differentiating between small and large bowel loops is sometimes possible when the haustra are visible. In neonates, this differentiation is not possible in most cases.

In case of intestinal obstruction, analysis of bowel gas dilatation and distribution on supine abdominal radiograph helps to determine the type of obstruction: functional or mechanical. In older children and adults, small bowel loop diameter does not usually exceed 20–25 mm. In neonates and infants, the upper limit changes according to the age. Obstruction should be considered when the loop diameter exceeds the diameter of a vertebrae. Normal large bowel diameter does not exceed 60 mm. In case of functional obstruction (gastroenteritis, post-operative paralytic ileus), general dilatation of small and large bowel loops is observed on the supine view and air-fluid levels of varying lengths are found on the upright view. In mechanical obstruction, small bowel dilatation with decreased or absent colon or rectal gas can be found on the supine view and air-fluid levels in dilated loops can help localize the level of obstruction on a standing film.

Pneumoperitoneum, pneumatosis and in some cases the etiology of the intestinal obstruction (foreign body, abdominal mass) can be detected on abdominal radiographs. If intestinal perforation is suspected, upright position, lateral decubitus with horizontal beam or cross table lateral views depending on patients’ age might be necessary to confirm the presence of extraluminal air (Fig. 9.2).

Still, the diagnostic yield of abdominal radiograph is low, as it is inconclusive in 25–35% of intestinal obstructions. Therefore, abdominal radiographs should not be performed if ultrasound or contrast examination finds the cause.

Indications for upper gastrointestinal (UGI) series, small-bowel follow-through (SBFT), or contrast enema in acute or subacute intestinal obstruction are summarized in Table 9.2. Iso-osmolar iodinated water-soluble contrast is generally preferred in children with signs of acute intestinal obstruction. The use of barium sulfate should be limited to the evaluation of non-complicated internal hernia or suspected malrotation without midgut volvulus. Air can be administered as natural contrast to reduce ileocolic intussusception [2].

In most cases of suspected intestinal obstruction, ultrasound should be the first imaging modality performed as it is a noninvasive and radiation free technique. It may localize the level of transition between dilated (>35 mm in older children) and normal loops. US can distinguish functional and mechanical obstruction [3] (Fig. 9.3). Moreover, US can depict the cause of the obstruction (appendicitis, Meckel diverticulum, malrotation, duplication cyst, etc.) and its related complications.

The different organs and vascular landmarks can be evaluated with US. The abnormal relative position of the superior mesenteric artery (SMA) and vein (SMV) is observed in small-bowel volvulus by Doppler ultrasound [4]. Finally, US can depict signs of severity such as bowel wall thickness >4 mm, absence of peristalsis, pneumatosis, intraperitoneal free fluid, or portal venous gas.

US has a lower specificity compared to CT for the diagnosis of pneumoperitoneum and for the assessment of bowel wall ischemia.

CT is usually not the initial radiologic examination in intestinal obstruction in children. In children under 2 years, the small amount of abdominal fat limits the distinction between the different digestive structures [5]. In older children and adolescents, the amount of fat increases and CE-CT allows an accurate evaluation of the localization and cause of the obstruction as well as the degree of severity. Therefore, CE-CT may be recommended when US is inconclusive especially in cases of volvulus, internal hernias, and complicated Meckel diverticulum. Precontrast imaging is not useful in most cases. An optimization of the CT settings according to the child age and weight is mandatory.

MR imaging is rarely performed to establish a diagnosis of acute intestinal obstruction. MR enterography may be useful for the diagnosis of obstruction related to intestinal stricture/fibrosis in patients with Crohn’s disease (see Chap. 13).

Compared with adults, gastric volvulus is rare in infants and children. The obstruction may be acute (43%) or chronic (57%) [6]. Two types of gastric volvulus have been described:

Mixed-type volvulus corresponds to the presence of features of both OA and OM volvulus.

Clinically, the most common signs of acute gastric volvulus in children are nonbilious vomiting, epigastric distension, and abdominal pain. Less common signs include acute respiratory distress, cyanosis, and hematemesis. In case of chronic gastric volvulus, symptoms may last for a longer time and include: nonbilious emesis, failure to thrive, growth retardation, gastroenteric reflux disease, and dyspnea [6]. In both types, it may be impossible to pass a nasogastric tube into the stomach or its course may be unusual [7]. Neurologic abnormalities, postsurgical interruption of the gastric ligaments following liver transplantation, Nissen fundoplication, heterotaxy syndrome with polysplenia can predispose to gastric volvulus. The mortality rate is relatively high in both acute and chronic gastric volvulus (6.5% and 2.7% respectively); more than two thirds of reported deaths are due to a delayed surgery [6].

Plain supine radiographs show a single large spherical gas bubble in the left upper abdomen or mid-abdomen (Fig. 9.4). It may contain an air-fluid level (one in OA, two in MA) on erect film. Elevation of the left diaphragm may be seen. A paucity of distal bowel gas is also seen in acute volvulus.

Contrast opacification will demonstrate the type of volvulus. In MA volvulus, the greater and lesser curvature maintain their normal relationship. The pylorus is abnormally placed close to and anterior and above the gastroesophageal junction (Fig. 9.4). In OA volvulus, the greater curvature lies above and to the right of the lesser curvature.

CT is not necessary in children and may delay the surgery. It is usually performed when the diagnosis is missed on initial plain radiographs [7]. Gastric distension, gastric pneumatosis, and patterns of heterotaxy may be demonstrated with CT.

As mentioned, the treatment is surgical.

Bezoars correspond to intraluminal accumulation in the stomach or small bowel of ingested material that cannot be digested due to its particular composition. They may be composed of vegetable fibers (phytobezoar), hair (trichobezoar), or milk (lactobezoar). Trichobezoar is more frequent in children compared with phytobezoar. Lactobezoar is more common in lactating newborns. Initial symptoms are pain, vomiting, anemia, enteric and pancreaticobiliary obstructions. A left upper abdominal mass is usually palpable.

Ultrasound may demonstrate an endoluminal highly echogenic arc of air with a posterior acoustic shadowing whose appearance does not change with the position of patient or with different transducers [8]. The main differential diagnosis is a heavily calcified tumor or a mass of impacted feces [8]. In this case, UGI or CT might be required (Fig. 9.5).

Sensitivity and specificity of CT for diagnosing an ileus induced by a bezoar are 90% and 57%, respectively [9]. The presence of a round, mottled intraluminal mass associated with dilated intestinal loops is a good sign suggestive of bezoar [10]. CT is also effective for excluding other causes of intestinal obstruction.

The removal of the bezoar can be performed by open or laparoscopic surgery [9].

Hypertrophic pyloric stenosis occurs usually during the first 3 weeks to the end of the second month of life. Males are more frequently affected than females. Vomiting is usually projectile and non-bilious, as the obstruction is located above the ampulla of Vater. US shows the muscular thickening, the gastric stasis, and the absence of pylorus opening (Fig. 9.6). US is the only useful examination. The muscle wall thickness is above 3 mm and the pyloric channel length is above 14 mm. Parietal pneumatosis may rarely occur. Pyloric hypertrophy may rarely be diagnosed in utero. Symptoms of hypertrophic pyloric stenosis can also appear after administration of prostaglandin E in patients with cyanotic congenital heart disease. In this case, pyloric stenosis is not secondary to muscular thickening but to mucosal hypertrophy often with polypoid or lobular appearance at US (Fig. 9.7). Subsequent progressive thickening of the antropyloric muscle may develop [11].

Treatment consists first in correcting the dehydration and second in surgical pyloromyotomy.

Duodenal duplication cysts represent approximately 5% of all gastrointestinal duplication [12]. The cyst is always located on the mesenteric side of the second portion of the duodenum. The cyst is located either within the wall or inside the lumen of the duodenum. The differential diagnosis includes duodenal atresia in the neonatal period and duodenal stenosis and duodenal web in later life.

US is helpful in demonstrating a round hypoechoic structure with a characteristic multilayered wall with hyperechoic inner mucosal layer and hypoechoic outer muscular layer. Cross-sectional imaging may reveal an intraluminal cyst in the second portion of the duodenum, with a shared medial wall between the cyst and the duodenum (Fig. 9.8).

Another differential diagnosis of intraluminal duodenal duplication cyst is a choledochocele: the former is located distal to the papilla, whereas the latter is located proximal to the papilla [13]. Clinically, children have symptoms of duodenal obstruction or palpable abdominal obstruction. The most common complication is pancreatitis [14].

The management includes either complete surgical resection of the duplication cyst or, in selected cases, endoscopic marsupialization.

Superior mesenteric artery syndrome is defined by the compression of the third portion of the duodenum between the aorta and the superior mesenteric artery (SMA). The prevalence of this syndrome is between 0.1 to 0.3%. The most common clinical presentation is vomiting, nausea, epigastric pain/distention, postprandial discomfort, and weight loss. It may be secondary to significant weight loss such as in anorexia nervosa, malabsorption syndrome, malignancy or following any severe injury. Correction of scoliosis (1–3 weeks after surgery) [15], rapid linear growth without compensatory weight gain particularly during the adolescence are other causes of superior mesenteric artery syndrome.

On UGI series, a dilatation of first and second portions of the duodenum with an abrupt narrowing of the third portion is observed (Fig. 9.9). The stomach may be distended as well. When the patient is positioned in a left lateral or ventral decubitus position, the obstruction resolves. However, a study comparing CT to fluoroscopy has a reported false-negative rate of 18.6% for barium studies [16].

On CE-CT with sagittal oblique reconstructions, the two key signs are: aortomesenteric angle below 22° and aortomesenteric distance of less than 8–10 mm [17] (Fig. 9.10). The SMA normally forms an angle of 45° with the aorta, with the normal angle ranging from 25° to 60° [18]. Associated imaging features include gastric and duodenal dilatation up to the aortomesenteric space where a sharp narrowing of the third portion of the duodenum can be seen.

The management is first conservative. It includes insertion of a nasojejunal tube to decompress the stomach and duodenum and enteral feeding. If conservative treatment is unsuccessful, laparoscopic or open duodenojejunostomy should be considered.

Malrotation anomalies occur in approximately 1 in 500 live births [19]. Duodenal obstruction is due to extrinsic compression from Ladd’s bands (extending from the cecum to the lateral abdominal wall) or to small-bowel volvulus. Malrotation related volvulus (midgut volvulus) occurs within the first year of life in 90% of cases (75% in neonates), however acute cases can be diagnosed at any age. Midgut volvulus can lead to intestinal ischemia and irreversible necrosis and is potentially fatal.

The most common clinical presentation is bilious vomiting during the first weeks of life. Vomiting may be accompanied by abdominal distension or rectal bleeding, as a late sign. Beyond the first months of life, symptoms are less typical. They range from acute abdominal pain and vomiting to recurrent abdominal pain or simply failure to thrive. In some cases, these signs are wrongly attributed to gastroesophageal reflux or to anorexia in adolescents.

On US, the characteristic finding of midgut volvulus is the so-called “whirlpool sign” [20] (Fig. 9.11). This sign is produced by the clockwise twisting of the bowel, mesentery and superior mesenteric vein (SMV) around the axis of the superior mesenteric artery (SMA) [20]. The SMV, normally located at the right of the SMA, wraps around the SMA and is abnormally located on the left side of the SMA (Fig. 9.11). The presence of dilated bowel loops, thickened bowel walls, aperistaltic loops, and peritoneal fluid suggest intestinal ischemic damage. However, the absence of these signs at US cannot exclude intestinal ischemia.

On abdominal radiographs, air is visible in the stomach with a paucity of or lack of gas in the distal bowel. However, in some cases, the bowel gas pattern is normal. Therefore, normal abdominal radiograph cannot completely exclude malrotation and even volvulus [21].

At UGI series, in children with malrotation, the duodenal-jejunal junction is abnormally located to the right of the spine (or at least on the right side of the left pedicle), below the level of the duodenal bulb and anteriorly on the lateral view. In children with midgut volvulus, the proximal twisted segment has a characteristic corkscrew-like appearance (Fig. 9.12). Obstruction due to Ladd bands produce a Z-shaped configuration of the duodenum [22]. In malrotation (without signs of intestinal obstruction), barium enema is performed to document the position of the cecum.

Older children, like adults, with suspected small bowel volvulus secondary to malrotation, are more likely to undergo CT than any other imaging modality. CE-CT may demonstrate the whirlpool sign and signs of small-bowel ischemia.

Children with midgut volvulus should be immediately referred to surgery. The curative surgical treatment consists in a Ladd’s procedure (i.e., untwisting the intestine, dividing congenital bands and widening the mesenteric attachments).

Congenital inguinal hernias affect between 1 to 2% of children and approximately 10% of these may be complicated by incarceration and bowel obstruction [1]. Males are more commonly affected than females. If incarceration has occurred, pain and vomiting are associated at physical examination with a localized inguinal lump that may or may not be reducible. In most cases, imaging is not necessary as inguinal hernia is a clinical diagnosis managed with manual reduction or surgery [1]. However, imaging might be required if the differential diagnosis includes hydrocele or if the hernia is not fully reduced.