GASTROINTESTINAL EMERGENCIES IMAGING

GASTROINTESTINAL EMERGENCIES
Appendicitis, and its possible complications, is one of the most common reasons for referral. Ultrasound has a high sensitivity for acute appendicitis, particularly in children. Although the detailed assessment of the primary gastrointestinal pathology usually requires evaluation by an experienced operator with a high-frequency linear probe, many useful indicators can be found with the basic curvilinear or sector abdominal scan.

The presence of fluid-filled bowel segments, which may also show ‘overactive’ peristalsis, should alert the operator to the possibility of acute intestinal obstruction. Such segments frequently lie proximal to the obstructing lesion, and so the point at which they appear to end should be the subject of detailed examination.

Ultrasound is highly accurate in demonstrating obstruction. However, it is less successful in finding its cause and contrast CT or other bowel studies are usually undertaken when obstruction is diagnosed. With both intestinal obstruction and focal pain it may be necessary to examine the hernial orifices. A small but symptomatic epigastric hernia often goes unnoticed unless a detailed scan of the abdominal wall is performed.

Fluid collections such as abscesses may also point to the diseased segment, for example in Crohn’s disease or acute diverticulitis. Such inflammatory bowel conditions may well present with an established history which helps the operator to focus the ultrasound examination accordingly. Perforation of an abdominal viscus can produce small amounts of ascites. This is usually ‘mucky’, i.e. containing particulate or gas bubble echoes, and may be localized close to the perforation site, around the duodenum or within the lesser sac.

Although gas is usually regarded as an obstacle to ultrasound diagnosis, recent studies have shown that specific patterns of gas echoes can make ultrasound more sensitive than plain radiography in the diagnosis of pneumoperitoneum.