The Acute Abdomen

10.1055/b-0034-87873

The Acute Abdomen

**Table 2.68 The acute abdomen in infants, toddlers, and older children**
Diagnosis	Findings	Comments
Appendicitis Fig. 2.138a, b Fig. 2.139 Fig. 2.140 Fig. 2.141, p. 230	US: Dilated or collapsed blind-ending structure ≥ 6 mm, with thickened or vanished submucosal layer; prominent hyperechoic periappendicular fat, echogenic fluid. Appendicolith (25%). Sono-graphic Blumberg (+). Hyperemia in Doppler images.	Mechanical or paralytic ileus may associate. DD: bacterial ileocecitis, inflammatory intestinal disease (IID), adenitis, right-sided omental infarction, Henoch-Schönlein purpura, primary peritonitis, ovarian pathology. US: diagnostic modality of choice. CT/MRI in equivocal cases.
Intussusception Fig. 2.142 Fig. 2.143 Fig. 2.144 Fig. 2.145 Fig. 2.146a, b Fig. 2.147	US: “crescent-in-doughnut” sign: mesenteric fat encircling entering intussusceptum. Sandwich sign. Can produce obstruction signs.	Mean age is 6 mo to 2 y. More than 95% ileocolic. Successfully enema reduction in more than 80% of cases. Less of 5% nonidiopathic: Meckel diverticulum, lymphoma (thick hypoechoic apex), etc.
Mechanical obstruction (see Table 2.44)	Proximal dilatation. Air-fluid levels.	AAIIMM (appendicitis, adhesions, IT, incarcerated hernia, Meckel diverticula, miscellanea).
Postoperative, postinfection adhesions	Dilated bowel loops proximal to the obstruction. Decreased or absent distal intestinal content.	May be present as early as 48 h. After 4% of surgeries.
Incarcerated hernia	Gas can be depicted beyond the abdominal cavity.	Obstruction complicated with strangulation: worse prognosis.
Volvulus Fig. 2.148a, b	Of stomach, duodenum, small bowel, sigmoid colon.
Midgut volvulus (see Table 2.44)	“Whirlpool” sign. Rare but severe. Prerequisite: malrotation.
Adynamic (paralytic) Ileus (see Table 2.44)
Inflammatory causes	Generalized or focal (sentinel loop) distended bowel loops with distal gas.	Gastroenteritis, appendicitis, enteritis, ovarian pathology.
Postoperative
Posttraumatic		After blunt abdominal trauma, including child abuse.
Extra-abdominal causes		Pneumonia, discitis, sepsis, metabolic, medication.
Toxic megacolon
Traumatic acute abdomen (AA): blunt abdominal trauma	Pneumoperitoneum, intraperitoneal or retroperitoneal hemorrhage/laceration of viscera.	Multidetector CT in polytrauma patients can be necessary.
Nontraumatic hemorrhagic AA: Gl bleeding from other causes Fig. 2.88a–c, p. 199 Fig. 2.89, p. 199	Angio-CT or MRI, angiography, endoscopy.	Massive bleed from a Meckel diverticulum: uptake of 99mTc pertechnetate if ectopic gastric mucosa is present. Hemolytic-uremic syndrome, ulceration, IID, tumors, angiodysplasia, intussesception.

**Fig. 2.138a, b Acute appendicitis.** RLQ US, longitudinal (a) and axial (b) views, shows a dilated obstructed appendix with a thin-rings pattern: the normal bowel wall layers are patent, unless their thickness is decreased and the lumen is occupied by purulent anechoic content. In axial view, there is an increased sound transmission pointing to the fluid nature of the content. The hyperechoic mesenteric fat is enlarged. The Doppler signal (longitudinal view) is increased in appendix wall.

**Fig. 2.139 Acute appendicitis.** Transverse Doppler US image of RLQ: An inflamed hypervascularized appendix is depicted. Note the difference in size and vascularization with the adjacent fluid-filled ileum.

**Fig. 2.140 Omental segmental infarction.** Sagittal Doppler US scan in mesogastric area: A hyperechoic avascular thickened omen-tum is seen beside the liver and kidney. The inflamed fat-containing omentum progressively attenuates the US beam.

**Fig. 2.141 Mesenteric adenitis.** Transverse Doppler US image in mesogastric area: There are several slightly increased in size (> 6 mm) mesenteric lymph nodes with patent vascularization. This is a nonspecific finding, and other causes of acute abdomen must be ruled out. In this case, the appendix (not shown) was normal.

**Fig. 2.142 Intussusception.** US axial image of an intussesception depicted at the subhepatic region. There is a thick hypoechoic outer “doughnut” with a crescent-shaped hyperechoic mesentery inside, eccentrically surrounding a hypoechoic central limb of the intussusceptum. This is the “crescent-in-doughnut” sign.

**Fig. 2.143 Intussusception.** US longitudinal image of an intussesception. There are several alternating bands that represent the hypoechoic intussesception and the hyperechoic mesentery. This is the “sandwich” sign.

**Fig. 2.144 Intussusception.** US axial image of an intussesception in the subhepatic region shows the double “crescent-in-doughnut” sign. There is an additional anechoic crescent inside the doughnut formed by trapped ascites located opposite to the mesenteric hyperechoic crescent. The presence of ascites is related with bowel ischemia and low reducibility rates. G Gallbladder

**Fig. 2.145 Intussusception.** Doppler US axial image of an intussesception showing blood flow in the peripheral doughnut and in the central mesentery. The presence of blood flow is a good prognostic sign of reducibility.

**Fig. 2.146a, b Intussusception reduction.** (a) During the hydrostatic echo-guided enema, the intussesception is seen partially reduced at the level of the ileocecal valve. (b) After intussesception reduction, the valve is seen open and with fluid passage through terminal ileum (blue color in the Doppler image).

**Fig. 2.147 Ileoileocolic intussusception.** Longitudinal US during hydrostatic echo-guided enema shows a complex polylobulated ileoileo-colic intussesception with fluid trapped inside attempting to pass through the valve. In this case, the reduction was not possible.

**Fig. 2.148a, b Sigmoid volvulus.** (a) Plain abdominal film shows a distal colonic obstruction with the “coffee-bean sign,” which is formed by twisted sigmoid colon and distended proximal colonic loops. (b) Contrast enema delineates the areas of sigmoid narrowing after devolvulation (arrowhead).

The Acute Abdomen in the Neonatal Period

**Table 2.69 Acute abdomen in the neonatal period**
Diagnosis	Findings	Comments
Gastric outlet obstruction	Plain X-ray: “single-bubble” image. When a single bubble is observed, most patients are taken directly to surgery.	Causes: antral or pyloric atresia, congenital peritoneal bands, annular pancreas. Cardinal symptom: free of bile vomiting.
Pyloric hypertrophy in the neonatal period Fig. 2.149, p. 234	US: mucosal thickening often with polypoid or lobular appearance (DD with the muscular thickening observed in hypertrophic pyloric stenosis).	After administration of prostaglandin E to infants with ductus-dependent congenital heart disease. The stenosis is produced by central foveolar hyperplasia.
Complete duodenal obstruction	More frequent than gastric obstruction. Plain radiograph: “double-bubble” image. Rarely require further radiologic investigation.	Causes: duodenal atresia, annular pancreas, and midgut volvulus. Less frequently secondary to duodenal web, Ladd band, or preduodenal portal vein.
Incomplete duodenal obstruction	Plain X-ray: distention of the stomach and duodenum with a diminished air in the small bowel. DD with HPS by US. UGI series: to differentiate midgut volvulus from a web or stenosis. US: to rule out extraluminal causes (duplication cyst).	Causes: duodenal stenosis, duodenal web, Ladd bands, midgut volvulus, annular pancreas, preduodenal portal vein, and duplication cyst.
High small bowel obstruction (SBO)	Abdominal X-ray: three or four air bubbles (more than in duodenal atresia and fewer than in ileal atresia). A UGI series is clearly not indicated. In cases of doubt, aspiration and insuffiation of air through a nasogastric tube. US to differentiate multiple dilated loops filled with fluid from ascites in patients with lack of air on the plain radiograph.	Causes: atresia or stenosis of the jejunum or proximal ileum. Clinically: bilious vomiting (frequently delayed until after the first feeding) and abdominal distention.
Low intestinal obstruction	Plain X-ray: multiple dilated air-filled bowel loops occupying the entire abdomen. Contrast enema: the critical DD finding on the contrast enema of a neonate with low obstruction is the presence or absence of a microcolon.	Occurring in the distal ileum or colon. Symptoms: vomiting, abdominal distention, and failure to pass meconium. Causes: ileal atresia, meconium ileus, colonic atresia, Hirschsprung disease, and functional immaturity of the colon.
Meconium peritonitis	Plain X-ray: linear or punctate calcifications over the serosal surfaces of the abdominal viscera. Decubitus X-ray to determine the presence of free air with a persistent perforation is essential. US: especially indicated in the presence of a relatively airless abdomen.	In-utero perforation of the fetal GI tract during the last 6 mo of pregnancy. May occur with meconium ileus but may occur with any type of obstruction and in utero perforation.
Anorectal malformations		Anorectal malformations are almost always evident on physical examination.
Pneumoperitoneum of GI origin	Left lateral decubitus radiograph most reliable.	It is usually the result of a hollow viscus perforation. In healthy neonates, is usually iatrogenic. Other causes: necrotizing enterocolitis, atresias, meconium ileus, congenital megacolon.
Pneumoperitoneum of pulmonary origin		Air passes to the abdomen through the normal diaphragmatic foramina. There is no perforation of the GI tract in these cases.
Necrotizing enterocolitis	Abdominal X-ray: linear or cystic pneumatosis intestinalis (submucosal or subserosal air). Portal vein gas: finely branching radiolucencies extending from the porta hepatis to the periphery of the liver. On US: bright, shifting echogenic foci within the portal vein.	Pathophysiology: ischemia, decreased mucus production, diminished immune response of the premature infants.
Massive ascites	US, abdominal radiograph to exclude complications, free air, or calcifications.	In congenital hydrops, urinary tract perforation (e.g., urethral valves), or GI perforation.

**Fig. 2.149 Pyloric hyperthropy.** A neonate with ductus-dependent congenital heart disease treated with prostaglandin E to keep the ductus open. Axial US scan through the gastric antrum reveals markedly hypertrophic mucosal folds (arrows) with an undulating appearance. The thickness of the muscular layer is normal (arrowheads).

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