Comparing the Diagnostic Accuracy of Ultrasound and CT in Evaluating Acute Cholecystitis

Abstract

Objective: In 2013, a multidisciplinary group at our Veterans Administration hospital collaborated to improve the diagnosis and treatment of patients with acute cholecystitis (AC) at our facility. Our role in this project was to evaluate the diagnostic accuracies of ultrasound (US) and CT.

Materials and methods: AC was diagnosed in 60 patients (62 patient encounters) between July 1, 2013, and July 1, 2015. Of these patients, 56 underwent US, 48 underwent CT, and 42 underwent both. For the same time period, 60 patients without AC underwent US and 60 patients without AC underwent CT, and these imaging studies served as comparison studies. The groups were combined for a total of 182 unique patient encounters. A single radiologist reviewed the studies and tabulated the data.

Results: The sensitivity of CT for detecting AC was significantly greater than that of US: 85% versus 68% (p = 0.043), respectively; however, the negative predictive values of CT and US did not differ significantly: 90% versus 77% (p = 0.24-0.26). Because there were no false-positives, the specificity and positive predictive values for both modalities were 100%. Among the 42 patients who underwent CT and US, both modalities were positive for AC in 25 patients, CT was positive and US was negative in 10 patients, and US was positive and CT was negative in two patients; in five patients, both US and CT were negative.

Conclusion: CT was significantly more sensitive for diagnosing AC than US. CT and US are complementary, and the other modality should be considered if there is high clinical suspicion for AC and the results of the first examination are negative.

Keywords: CT; Veterans Administration medical center; acute cholecystitis; quality improvement; ultrasound.

Fig. 1—

Acute calculous cholecystitis in 84-year-old man with end-stage renal disease, diabetes mellitus type 2, hypertension, and history of renal cell carcinoma and prostate cancer. Patient presented to emergency department with abdominal pain and constipation. A and B, Ultrasound (A) and CT (B) images show cholelithiasis, gallbladder distention and wall thickening, and pericholecystic fluid (arrow). Sonographic “Murphy” sign was positive. Because of multiple comorbidities, patient was poor surgical candidate and was treated medically.

Fig. 2—

Acute acalculous cholecystitis in 85-year-old man who presented to emergency department with 2-day history of cramping right upper guadrant pain, which worsened with eating, and nausea. A, CT image shows pericholecystic inflammation (arrow), wall thickening, and gallbladder distention. B, Ultrasound image obtained before CT but on same day as CT is occult for acute cholecystitis. Cholecystectomy was subseguently performed.

Fig. 3—

Acute calculous cholecystitis in 53-year-old man who presented to emergency department with recurrent postprandial right upper guadrant abdominal pain and tenderness. A, Ultrasound image shows gallbladder wall thickening and cholelithiasis (arrow). Sonographic “Murphy” sign was positive. B, Cholelithiasis (arrow) is evident on CT image obtained later same day as ultrasound (A); however, there are no other CT findings suggestive of acute cholecystitis. Patient was not good surgical candidate secondary to alcoholic cirrhosis and thrombocytopenia and was treated medically.