Teaching Case

A 26-year-old female, gravida 3 para 2, presented with postpartum haemorrhage on day 42 of delivery via cesarean section. She was tachycardic and hypotensive with a haemoglobin of 5 gm/dL. On examination, the superficial lower abdominal wall scar was well apposed. Her uterus was bulky and the vagina was non-lacerated.

Ultrasound showed a bulky post-partum uterus without evidence of retained products of conception. A rounded sac was noted in close contact with endometrial canal at the site of the surgical scar, measuring 1.8 X 1.7 cm (Figure 1A). The central anechoic area was showing turbulent blood flow on colour Doppler giving a “yin-yang” sign (Figure 1B). There was bidirectional flow suggestive of systolic and diastolic blood flow within the sac (Figure 1C). A computed tomography (CT) angiogram showed a saccular dilatation arising from the right uterine artery, in the right lateral wall of the uterus, consistent with a pseudoaneurysm (Figure 2).

Due to the risk of rupture of the pseudoaneurysm and to preserve fertility, a digital subtraction pelvic angiography was performed. Selective catheterisation using microcatheter was done. The pseudoaneurysm was occluded using cyanoacrylate glue and Lipiodol. Post-procedural angiogram revealed complete embolisation and exclusion of the pseudoaneurysm (Figure 3).

Secondary causes of delayed postpartum haemorrhage include retained products of conception, sub-involution of the placental bed, and less commonly endometritis. Rarer causes include pseudoaneurysm, arteriovenous malformations, and choriocarcinoma [1].

A pseudoaneurysm is an extra-luminal collection of blood contained by the adventitia or surrounding perivascular soft tissue. It communicates with the flowing arterial blood through a defect in the arterial wall and when connected with the uterine cavity it results in recurrent haemorrhage [2]. It has been reported as a complication of pelvic surgery, vascular trauma during cesarean section or after uterine curettage. After hematoma formation, there is central liquefaction which results in a cavity with turbulent blood flow, as a result of persistent communication between the parent artery and the hematoma. The absence of a 3-layer arterial wall lining the pseudoaneurysm differentiates it from a true aneurysm [2].

Uterine artery pseudoaneurysm can easily be diagnosed on Doppler sonography, computed tomography (CT), magnetic resonance angiography and conventional angiography. On ultrasound, pseudoaneurysms appear as an anechoic sac which shows turbulent arterial flow. Doppler demonstrates to-and-fro sign in the neck of the pseudoaneurysm and yin-yang sign in the body of the pseudoaneurysm which is pathognomonic. During systole, with higher arterial pressure, there is an influx of blood into the pseudoaneurysm. In diastole, the pressure in the artery drops and blood flows back through the pseudoaneurysm neck [3].  

Conventional angiography, however, remains the gold-standard for diagnosis of uterine artery pseudoaneurysms and to decide treatment options [4]. Trans-catheter uterine artery embolization (UAE), first reported by Brown et al. in 1979, has been regarded as a highly effective technique for controlling obstetric and gynecologic haemorrhage, including that from pseudoaneurysms and therefore sparing fertility [5]. The success rate has been reported by up to 97% [4].

Some previous reports have documented recurrent bleeding after uterine artery pseudoaneurysm which may have been attributed to bleeding from a branch of the contralateral uterine artery feeding the same false aneurysm. Therefore, bilateral UAE has been proposed by many to be safe and more advantageous in such cases [4,6].

To conclude, uterine artery pseudoaneurysms are rare complications that can arise after repeated curettage, abortions, cesarean sections or reproductive tract infections and are potentially life-threatening causes of secondary postpartum haemorrhage. They have characteristic imaging features and can easily be diagnosed promptly. In our case, the pseudoaneurysm was successfully embolized, and the patient went on to conceive and have children subsequently without any consequences.