The normal features of the intestine in ultrasonography are well defined: as rule, all parts of the gastrointestinal (GI) tract have a three-layer appearance, corresponding to the muscularis propria, the submucosa, and the mucosa. All parts of the GI tract have a more or less pronounced luminal filling content of various properties: water or water-like liquids are contents that enable the best visualisation, while gas or faeces filling the intestinal tube can prove less favourable or even a hindrance to ultrasound examination.
Physical examination and careful clinical follow up in GI emergencies deserve special attention and work – any imaging modality can only contribute to the information gained from these basic clinical procedures. Repetitive palpation of the abdomen is the mandatory and diagnostically leading step.
Changes from normal to pathological anatomy can be observed and defined quite clearly in a number of acute emergency intestinal diseases. However, other diagnostic challenges – especially vascular disorders – may be inadequately met via abdominal ultrasound, and should be met with secondary imaging modalities such as computed tomography (CT) or magnetic resonance (MR).
Increased lumen diameter in a given GI tract section and too high a fluid content are the main features of intestinal obstruction. Ultrasound diagnosis of this can precede the radiological typical ileus aspect by several hours, since ultrasound does not depend on the gas–fluid-separation processes needed for conventional X-ray imaging. The location and even the reason for the obstruction can be defined by ultrasound examination with some – or even a (very) high – degree of probability. This is the case in inflammatory or tumourous acute obstructions as well as in other rare pathologies (as for example in gallstone ileus or in bolus obstruction in body packers) (see Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6).
Acute wall thickening processes – such as “spontaneous” intramural bleeding in anticoagulant therapy – are easily defined by ultrasonography, as are decompensated strictures in chronic inflammatory bowel disease, (sigmoid) diverticulitis and acute appendicitis (see Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11).
Acute ischemic wall thickening in intestinal loops followed by bacterial inflammation can lead – in case of gas producing microbes – to typical intramural and portal gas bubbles. Acute intestinal arterial and/or venous perfusion disorders of the not necrotising type, however, still remain an unsolved problem for ultrasound diagnostic techniques, even with elaborate coöour doppler techniques, since there is, as a rule, limited access to the main peripheral abdominal vessel branches and often to the main feeding vessels as well. Other modern technologies, such as angio CT or MR, might prove more useful in such situations (see Fig. 12, Fig. 13, Fig. 14, Fig. 15, Fig. 16, Fig. 17).
Intestinal perforation – be it spontaneous or traumatic – with collection of free gas (“free air”) and/or pathological fluid collections (“ascites”) is a good target for quick ultrasound detection and further decision making in emergency situations. Ultrasound guided emergency puncturing of pathological fluid collections will quickly reveal their true nature (blood, intestinal content, empyema, etc.), and this diagnostic procedure may lead to immediate and adequate therapy in the sense of ultrasound guided drainage application.
Combined with the patient’s history and the clinical findings (including laboratory findings), ultrasound is the main – but not always the sole – imaging tool for precise, truly cost effective and reliable decision making for further diagnostic steps and emergency therapeutic options in a variety of situations (see Fig. 18, Fig. 19, Fig. 20, Fig. 21).
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