Benefit of CT venography for the diagnosis of thromboembolic disease

The aim of this study was to determine the benefit of lower extremity CT venography (CTV) with pulmonary CT angiography (CTA) for diagnosing thromboembolic (TE) disease.

Reports of all CTAs and CTVs over a 3-year interval (Group I) and CTAs, CTVs, and lower extremity Doppler ultrasounds (US) over a 1 1/2-year subset (Group II) were reviewed. Patient population was inpatients and emergency department patients who were assessed for pulmonary embolism (PE) and deep venous thrombosis (DVT) at a tertiary care hospital. Reported results for CTA or CTV were categorized as positive (CTA(P), CTV(P)), negative (CTA(N), CTV(N)), or indeterminate for PE or DVT. When CTV and US results were discrepant, medical records were reviewed for clinical management. Additional benefit of CTV was assessed by chi-square analysis.

In Group I, 737 (81.1%) of 909 CTAs from combined CTA/CTV studies were negative. The diagnosis rate of TE disease increased from 13.0% to 17.3% with the addition of CTV(P)s (P=.01). Of the 119 cases in Group II undergoing combined CTA, CTV, and US, CTV and US were both positive in eight and both negative in 88. Of the seven discordant CTVs and USs with clinical follow-up, five CTVs were positive while USs were negative, three of which were treated clinically for TE disease, while two were considered falsely positive. As CTA also proved positive in one of the three, CTV therefore affected management in two of these five cases and increased the rate of thromboembolism diagnosis from 21.0% to 22.6%; however, this was not significant (P>.05). Two CTV(N)s were managed as false negatives.

The combined use of CTA and CTV significantly increases the rate of TE disease over CTA alone. In cases in which ultrasound is performed, however, there is no significant advantage to performing combined CTA/CTV studies.