In this case, cesarean section (C/S) was performed for fetal bradycardia of unknown origin. Retroperitoneal hematoma was found intraoperatively and turned out to be caused by the rupture of a RAA. This case was rare and unique, in that RAA rupture in a pregnant woman was the cause of prolonged hypotension and retroperitoneal hematoma. Fetal bradycardia likely resulted from blood loss and decreased perfusion to the placenta.
The prevalence of visceral artery aneurysm (VAA) has been reported as 0.01–2% of the population [1, 2]. However, the number of undetected VAAs may be much larger, as VAAs are usually asymptomatic. VAAs can be found in the following locations: splenic artery, 60%; hepatic artery, 20–50%; superior mesenteric artery, 5.5–6%; celiac artery, 4%; gastric and gastroepiploic arteries, 4%; jejunal, ileal, and colic arteries, 3%; pancreaticoduodenal and pancreatic arteries, 2%; gastroduodenal artery, 1.5%; inferior mesenteric artery, < 1%; and renal artery, 0.01–0.09% [2, 3, 6]. Risk factors for rupture include hypertension, aneurysm size ≥ 2 cm, non-calcified aneurysm, and pregnancy . The mortality rates for maternal and fetal death due to VAA rupture are 70–75% and 90–95%, respectively. Since 24–45% of VAAs rupture during the last trimester and the early phase after delivery, these periods are particularly hazardous . Although RAA comprises approximately 0.01% of VAAs and only 32 cases have been reported over the past 20 years , over 50% of ruptured RAAs in patients under 40 years old are reportedly related to pregnancy .
Rupture of RAA likely caused lumbar and abdominal pain, but pressure from the gravid uterus limited the severity of hemorrhage, and the mother did not experience severe shock right away. After delivery, decreased pressure from the uterus caused an increase in hemorrhage from the ruptured RAA, leading to enlargement of the retroperitoneal hematoma and persistent hypotension despite transfusion and administration of IV fluids and vasopressors.
At the time of starting surgery, maternal hypotension and tachycardia were indicated to have resulted from hemorrhage. Thorough examination by US, not just of the uterus and placenta, could have detected RAA or retroperitoneal hematoma on arrival. However, continuous fetal bradycardia did not allow any delay in emergency C/S, so the origin was detected intraoperatively. Although preoperative US yielded no significant results, delivering the baby may have made the hematoma more prominent as uterine pressure on the origin of hemorrhage was released.
Dissection or aneurysm rupture during pregnancy is considered more likely to occur. Hemodynamic stresses and hormonal changes associated with pregnancy could lead to changes in arterial structure and integrity. Various theories have been suggested in terms of these changes. Some previous studies have referred to possibilities including increased outflow resistance of arteries due to the increase in circulating blood and compression by the gravid uterus, vasodilation induced by estrogen or nitric oxide (NO) , histological changes in reticulin fibers or elastic fibers, and changes in smooth muscle cells [8, 9]. Underlying diseases related to the formation of VAA include vasculitis, fibromuscular dysplasia, syphilis, hypertension, atherosclerosis, and trauma [2, 10]. Sjögren syndrome, as seen in this case, is not typically associated with VAA.
In conclusion, we reported a case of emergency cesarean section due to fetal bradycardia of unknown origin, which turned out to be caused by renal artery aneurysm rupture. Non-reassuring fetal status with maternal hypotension may reveal underlying retroperitoneal hemorrhage. Since preoperative US did not show placental abruption or uterine rupture in this case, other causes of non-reassuring fetal status should have been considered. Pregnancy increases the risk of VAA rupture, and several reports have described VAA rupture during the perinatal period. Rupture of the VAA should be considered when sudden-onset abdominal pain and acute hemodynamic changes are seen during pregnancy. When emergency C/S is indicated, the focus tends to be on delivering the fetus immediately, rather than finding the cause. However, rupture of aneurysms should not be forgotten.