APPENDICITIS ULTRASOUND DIAGNOSIS

Appendicitis
Ultrasound is the first line of investigation for the child presenting with acute abdominal pain, where the diagnosis is uncertain following clinical assessment. The position of the appendix in small children may vary pointing upwards, downwards or to the patients left making the clinical diagnosis difficult, as the pain is not always confined to the right lower quadrant. Ultrasound is particularly useful in establishing the diagnosis of acute appendicitis and in diagnosing other possible causes of acute abdominal pain, such as gynaecological disorders. It is always good practice to perform a full abdominal survey when the clinical presentation is indeterminate.

Ultrasound demonstrates a hypoechoic, thickened appendix, > 6 mm thick, with a blind end. Occasionally an appendicolith, with strong acoustic shadowing, is present. The inflamed appendix is not compressible on gentle, graded compression with the transducer. This should be done very carefully, and released very slowly to avoid rebound tenderness.

Ultrasound cannot reliably exclude appendicitis, especially if the appendix is retrocaecal. Perforation may not be easy to see with ultrasound, as fluid may disperse through the abdomen with decompression of the appendix itself. However, a frank periappendiceal fluid collection or abscess is easily demonstrable in a proportion of children and may, in some cases, be treated conservatively with antibiotics or drained percutaneously prior to surgery.

The presence of free fluid, particularly if clear, in the abdomen is a non-specific finding and is not a reliable indicator of an acute abdomen. If echogenic fluid is seen, this is suggestive of intraperitoneal infection in the child with acute abdominal pain, but may be seen in other conditions, for example rupture of a haemorrhagic ovarian cyst. If ultrasound is equivocal, the clinicians may decide to observe the child but further imaging with CT scanning can be helpful in a few selective cases. Alternatively a laparoscopic examination may be performed where there is significant clinical concern.