The pelvis after cesarean section and vaginal delivery: normal MR findings

In postpartum women, pain and fever can indicate serious complications, such as phlegmon or abscess of the parametrium or bladder flap, ovarian vein thrombosis, or uterine dehiscence. The purpose of this study was to ascertain the MR appearance of the normal pelvis after uncomplicated cesarean section and vaginal delivery.

Twenty-two patients (14 who had cesarean sections and eight who had vaginal deliveries) were imaged with a superconducting 0.35-T MR system 1-5 days after delivery. Sagittal and axial T1-weighted, proton density-weighted, and T2-weighted spin-echo images were acquired. Phase reconstruction of the axial T1-weighted sagittal images was performed to confirm flow in the ovarian veins. The ovarian veins, parametrium, bladder flap, endometrium, and uterine incision were analyzed on all images.

The uterine incision was well seen in all 14 patients who had cesarean section. The signal characteristics of the incision suggested subacute hematoma within the myometrium, and no myometrial defects were seen. In all 13 patients with a low transverse incision, a hematoma of the bladder flap was seen. Patency was confirmed in the majority of ovarian veins (39/44). No evidence of parametrial edema or mass, which can be seen in abscess or phlegmon, was found in any of the 22 patients. The ovarian perivenous fat did not show edema, which can indicate acute ovarian vein thrombosis. Increased signal in the endometrial cavity was seen in all patients; the signal characteristics were similar to those of subacute hematoma, consistent with clinical findings.

Normal findings of the postpartum pelvis on MR imaging are subacute hematoma in the uterine incision, bladder flap, and endometrial cavity. Patent ovarian veins are demonstrated in most (89%) cases.