Isolated calf vein thrombosis: Comparison of MR venography and conventional venography after initial sonography in symptomatic patients

Rationale and Objectives. The authors performed this study to compare magne tic resonance (MR) venography and conventional venography in the diagnosis of deep venous thrombosis (DVT) in the calf after sonography. Materials and Methods. Sonography was performed in 595 patients who were su spected of having lower-extremity DVT. Patients with positive above-knee du plex sonograms, allergy to iodinated contrast material, renal insufficiency , or cardiac pacemakers and patients who were obese were excluded. The rema ining 73 patients were asked to undergo MR venography and conventional veno graphy. All studies were to be performed within 48 hours of the clinical di agnosis and according to standard clinical practice. Images were interprete d by radiologists who were blinded to the results of other modalities. Two separate analyses were performed: one in which conventional venography was used as the standard of reference, and one in which the presence of at leas t two positive studies for thrombus was considered diagnostic. Results. Although 36 patients agreed to participate in the study, only 14 u nderwent MR venography and conventional venography within 48 hours of the c linical diagnosis. With use of any two positive studies for confirmation, a cute DVT was diagnosed in three patients. Conventional venography depicted two of the three cases, whereas sonography and MR venography each depicted all three. The findings were concordant in only five of the 14 patients. Conclusion. Moderate discrepancy among modalities was demonstrated. This su ggests radiologists should undertake comparisons among these three modaliti es for the detection of calf DVT. In patients with a high clinical suspicio n, a second modality may be useful if the initial study is negative.