Ultrasonography in the diagnosis of acute appendicitis.

Ultrasonography with graded compression was performed in 525 patients with clinical signs of acute appendicitis. Of 207 patients with surgically proven appendicitis the inflamed appendix (diameter greater than or equal to 6 mm) had been visualized sonographically in 177 (86 per cent). The score for non-perforated appendicitis (91 per cent) was higher than for perforated appendicitis (55 per cent). Twenty-four patients in whom an inflamed appendix was seen on ultrasonography did not undergo surgery because of rapidly subsiding symptoms ('abortive appendicitis'). Four of these 24 developed recurrent appendicitis warranting surgery. Two underwent elective appendectomy and 18 have remained symptom-free. Of 155 patients with a subsequently confirmed alternative condition, ultrasonography made the correct diagnosis in 140: bacterial ileocaecitis (69), mesenteric lymphadenitis (eight), gynaecological conditions (34), urological conditions (eight), caecal diverticulitis (six), perforated peptic ulcer (six), Crohn's disease (two) and miscellaneous conditions (seven). Of 139 patients in whom no definite diagnosis was made ultrasonography showed no abnormalities in 138. In four patients a false positive sonographic diagnosis of appendicitis was made and in two patients with appendicitis an alternative condition was incorrectly diagnosed. During the last 3 years of the study the negative appendicectomy rate was 7 per cent and delay beyond 6 h after admission occurred in only 2 per cent of patients with surgically proven appendicitis. When used to complement the clinical diagnosis ultrasonography improves the diagnostic accuracy and patient management in those suspected of having acute appendicitis.