CT in the evaluation of nontraumatic abdominal pain in pregnant women.

PURPOSE: To retrospectively determine sensitivity and specificity of computed tomography (CT) for the diagnosis of appendicitis in pregnant women with nontraumatic abdominal pain and retrospectively compare findings at CT and ultrasonography (US) in patients who underwent both examinations, with surgery or clinical follow-up as a reference standard.

MATERIALS AND METHODS: Institutional review board approval was obtained, and the study was HIPAA compliant. Informed consent was waived. Findings of 80 consecutive CT examinations performed in 78 pregnant women (mean age, 25.9 years; range, 17-43 years) for abdominal pain between September 2000 and October 2004 were compared with findings at prior US (n=52), surgery, and clinical follow-up. Sensitivity and specificity were calculated for the diagnosis of appendicitis. The average fetal radiation dose was 16 mGy (1.6 rad) (range, 4-45 mGy [4-4.5 rad]).

RESULTS: CT findings were normal in 51 examinations (64%) and abnormal in 29 (36%). Abnormal findings were appendicitis (n=13), urinary tract calculi (n=6), small-bowel obstruction (n=2), cholelithiasis (n=2), pyelonephritis (n=2), diaphragmatic hernia (n=1), cecal bascule (n=1), ileus (n=1), and metastatic lymphadenopathy (n=1). One surgically confirmed case of appendicitis was not detected at CT. For diagnosis of appendicitis, sensitivity of CT was 92% (12 of 13 examinations), specificity was 99% (66 of 67), and negative predictive value was 99% (66 of 67). Fifty-two CT studies were performed after US. US findings were normal in 46 patients (88%) and abnormal in six (12%). Abnormal findings were cholelithiasis (n=3), obstructive hydronephrosis (n=1), small-bowel dilatation (n=1), and appendicitis (n=1). Among 46 patients with normal US findings, CT findings were abnormal in 14, nine of whom required surgery. CT added important diagnostic information in 14 of 46 patients (30%).

CONCLUSION: CT findings established the diagnosis in 35% of examinations in pregnant women with abdominal pain (28 of 80), with a negative predictive value of 99% for appendicitis; when CT followed negative US findings, CT findings established the diagnosis in 30% of patients.