Prospective evaluation of ultrasonography in acute colonic diverticulitis.

Background: The clinical diagnosis of acute colonic diverticulitis (ACD) can be difficult and ultrasonography by experts is valuable in establishing the diagnosis. This prospective observational trial aimed to assess the diagnostic accuracy and clinical value of ultrasonography performed routinely by surgical residents in training.

Methods: The clinical course of 187 unselected consecutive patients admitted with suspected ACD was studied prospectively. Patients who had surgery for generalized peritonitis were excluded, leaving 143 for evaluation. Ultrasonographic findings and clinical assessment on admission were correlated with the patient's clinicopathological data and discharge diagnosis respectively.

Results: Of 74 patients with proven ACD (prevalence 52 per cent) the diagnosis was made by ultrasonography in 62, with an accuracy of 88 per cent, sensitivity 84 per cent and specificity 93 per cent. Ultrasonography gave a false-negative result in 12 patients (negative predictive value (NPV) 84 per cent) and there were five false-positive findings (positive predictive value (PPV) 93 per cent). The final diagnosis in the latter five patients was colitis (two patients), caecal carcinoma (one), colonic ileus due to perforated sigmoid carcinoma (one) and suppurative pyosalpingitis with involvement of the sigmoid colon (one). The accuracy of clinical evaluation on admission was 71 per cent (sensitivity 82 per cent, specificity 55 per cent, PPV 72 per cent, NPV 68 per cent); however, in only 53 per cent of patients was the diagnosis considered clinically unequivocal.

Conclusion: Ultrasonography is a useful and valid modality for imaging ACD and its differential diagnoses in the hands of sonographically trained surgeons. It is especially helpful when the clinical findings are equivocal.