High Incidence of Pelvic Deep Vein Thrombosis Detected by Magnetic Resonance Venograpy Post-Caesarean Section.

Background Venous thromboembolism (VTE) is the leading cause of maternal mortality in the developed world. The post-partum period is the highest risk period for pregnancy associated VTE and delivery by Caesarean section further increases this risk. The true incidence of deep vein thrombosis (DVT) post- Caesarean section is unknown but felt to be low. The limited number of screening studies conducted to date have not included systematic pelvic vein imaging.

Objectives To determine the incidence of DVT post-Caesarean section using Magnetic Resonance Venograpy (MRV) and bilateral compression ultrasounds.

Methods Prospective cohort study of moderate to high risk women (one or more VTE risk factors) post-Caesarean section. On the day of post-partum discharge we conducted systematic bilateral proximal leg vein compression ultrasound imaging to detect proximal leg DVT and pelvic vein imaging with magnetic resonance venography (MRV). MRVs were independently and blindly interpreted by two radiologists with disagreements resolved by consensus. MRVs were interpreted as demonstrating definite, probable, possible or no thrombosis. Two rater Kappa scores were calculated from initial interpretations (prior to consensus review). Incidence of DVT and 95% confidence interval were calculated.

Results Fifteen patients were recruited. At discharge, there were no proximal DVTs on bilateral leg compression ultrasounds. MRV results are shown in Table I.

Conclusions The incidence of pelvic vein DVT post- Caesarean section is much higher than anticipated (46%). The clinical significance of this finding remains to be determined. However, diagnoses such as septic pelvic vein thrombophlebitis, which depend on demonstrating the presence pelvic vein thrombosis in the setting of post-partum fever may be falsely overdiagnosed. Pelvic vein thrombosis may be a common (and normal) finding post-Caesarean section. MRV may also prove to be a useful surrogate outcome measure in post-partum VTE prophylaxis studies.

Table I: Pelvic Vein Imaging Results Post-C-Section