Ruptured Renal Artery Aneurysm in Late Pregnancy: Challenges in a Patient with Atrophic Kidney

Introduction

Renal artery aneurysm (RAA) is a rare condition in the general population. The incidence of visceral arterial aneurysms is 0.01–2% of the population, and 0.01–0.09% of these are found in the renal arteries [1,2]. Most RAAs are discovered incidentally on imagining studies and do not pose immediate health risks [3]. Symptomatic patients typically present with hematuria or acute flank pain related to rupture, leaking, dissection, or thromboembolism [4]. Females comprise 72% of recorded cases [4], and the mortality of RAA rupture is directly related to pregnancy. The mortality rate for nongestational RAA rupture is around 10%. Pregnancy results in a mortality rate of 50% and 80% in the mother and infant, respectively [5,6]. The higher risks of RAA rupture during pregnancy are likely due to arterial wall changes secondary to the physiological hormonal and hemodynamic adjustments [7,8].

Asymptomatic unilateral kidney atrophy occurs in around 1.5% of patients, and in the vast majority of cases the atrophic kidney is on the left side [9]. The concurrent presence of a third-trimester ruptured RAA with maternal and fetal distress and a contralateral atrophic kidney has not been previously reported. We present a complex case of rapid maternal and fetal deterioration that required emergency surgery adjustments intraoperatively. Access to a highly specialized healthcare network to prevent major loss was essential.

Case Report

A 39-year-old woman with 1 previous term cesarean delivery presented to an outside emergency department (ED) at 36 weeks of gestation due to the sudden onset of unexpected, unprovoked, non-radiating right flank pain. She denied trauma, chills, fever, or a history of medical illness other than treated hypothyroidism. Her family and social history were negative. She had experienced 3 spontaneous first-trimester abortions. The current pregnancy was characterized by late entry into prenatal care, but otherwise was uneventful.

Vitals signs at the outside ED were reportedly stable. Physical exam results were unremarkable except for right flank pain, and the cervix was 2 cm dilated per the ED physician. Her pain was worsened with breathing, so computed tomography (CT) with contrast to rule out pulmonary embolus (PE) was ordered. The fetal heart tones (FHTs) were shown as 120 bpm on Doppler. The vital signs precipitously worsened, and the patient was urgently transferred to our facility for treatment before the results of the CT were available. Upon arrival at the tertiary receiving center, she was diaphoretic. Vital signs were significant for hypotension with a systolic blood pressure of 60. FHTs could not be obtained on Doppler, but bedside ultrasound showed depressed agonal FHTs in the 60s. The duration of the bradycardia was unknown. The patient was quickly transferred to the operating room (OR) for an emergency repeat cesarean delivery under general endotracheal anesthesia through a Pfannenstiel incision. On entering the abdomen, a 200-cc unexplained hemoperitoneum was encountered. The previous uterine scar was intact. A cesarean section was performed, and a 3185-g infant was delivered with Apgar scores of 1, 4, and 7, and pH of 6.8, with a base deficit of 29. The hysterotomy was closed. Through a midline abdominal incision, the surgeons quickly discovered the source of the hemorrhaging as the ruptured right RAA. While preparing for a right nephrectomy, a kidney-like mass was felt on the side of the lower spine, just below the ribcage retroperitoneally. The imaging results from the CT (Figure 1) at the first ED were communicated to the OR, and the patient was noted to have an atrophic left kidney. General Surgery examined the hematoma directly, and it was non-expanding; her vital signs stabilized, so they promptly ordered her transferred her to the main critical care hospital. She had received 1 unit of packed red blood cells and 1 unit of fresh frozen plasma. Her abdomen was closed, and she was sent to the nearby adult intensive care unit (ICU) in an adjacent section of the main campus (Figure 2). Subsequently, she was taken to interventional radiology, and a renal angiogram was performed (Figure 3). A right renal artery stent placement was successful. At this time, her hemoglobin remained stable at around 7 g/dL (grams per deciliter) (normal range, 12.0–15.5 g/dL for women) (Table 1). Her baseline creatinine (Cr) from 2 years previously was 0.65 mg/dL (milligrams per deciliter) (normal range, 0.6–1.1 mg/dL for women). When she first presented during this admission, her Cr was 0.93 mg/dL. Postoperatively, her creatinine rose to 1.27; however, it normalized to 1.02 mg/dL on postoperative day 2 and then was 0.78 mg/dL at the time of discharge. She had a mild acute kidney injury, which resolved with a baseline creatinine of 1.10 mg/dL (milligrams per deciliter) (normal range, 0.6–1.1 mg/dL for women). Her postpartum course was complicated by gestational hypertension and postpartum endometritis, which resolve over time with administration of ampicillin-sulbactam 3 g intravenous (IV) every 6 hours. A repeat abdominal CT on postoperative day 6 showed a small pleural effusion with a stable retroperitoneal hematoma. She was transitioned to oral amoxicillin-clavulanic acid 875 mg every 12 hours on hospital day 10, but again became febrile. Her recurrent fevers were presumed to be secondary to the large retroperitoneal hematoma, which was treated medically with intravenous antibiotics. Per infectious disease recommendations, she was started on IV ertapenem and discharged on hospital day 12 with a midline in place to complete treatment for 7 days. She started aspirin and Plavix after her stent placement, as well as enoxaparin 30 mg subcutaneously every 12 hours for 10 days for DVT prophylaxis. Since discharge, a pseudoaneurysm was found on imaging to be formed distal to the stent in her right renal artery. She was counseled extensively about the consequences of potential renal damage from an attempted endovascular correction of a pseudoaneurysm in the sole functioning kidney and consented to the procedure. This was successfully embolized through an endovascular approach (Figure 4). The patient was also seen by Nephrology and is being monitored for functional status of her left kidney. Of note, the neonate was discharged from the neonatal intensive care unit after 6 months and is now meeting appropriate developmental milestones.

Discussion

There are 3 important components to this case. First, rupture of a RAA is rare in pregnancy and can affect the clinical outcome. Second, nephrectomy is an accepted treatment for ruptured RAA in pregnancy, but this patient had a contralateral atrophic kidney that was undiagnosed preoperatively. Third, a very complex healthcare network with extensive resources and active communication is required to treat this condition.

First, rupture can be clinically devastating in pregnancy. Multiple case reports and several case series have all consistently shown how lethal the rupture of an RAA can be for mothers and infants in pregnancy [5,9]. The clinical presentation is consistent with back, flank, or abdominal pain followed by an obstetric emergency. Since 62% [9] of ruptured RAAs in pregnancy occur in the third trimester, the fetus is likely viable when the rupture occurs. Although advanced gestation can reduce neonatal complications, overall fetal well-being depends on reliable uteroplacental blood flow [10]. A ruptured RAA hemorrhaging into the retroperitoneal space can produce rapid hypovolemia resulting in a marked intravascular depletion, consumptive coagulopathy, and uteroplacental failure. If the patient is supine, the condition is worsened [11].

Unless normal pregnancy physiology is restored, nonremedial fetal distress follows, and without delivery and renal vascular surgery, the outcome is fatal. This patient’s initial chief concern of flank pain probably reflected leaking or dissection [12]. She and the fetus were clinically stable enough to be sent to an imaging location to have a CT to rule out PE. Even before the CT could be interpreted, however, she and the fetus rapidly became hemodynamically unstable, likely reflecting RAA rupture and hypovolemia from rapid retroperitoneal exsanguination. She was transported to a higher-level care center [13], but by the time she arrived at the tertiary center both the fetus and mother were in extreme distress. The maternal condition on arrival was a clear obstetric emergency with shock. The fetus had an agonal heart rate on arrival and at cesarean delivery was profoundly acidotic with an umbilical cord pH of 6.8 (7.34±0.07) and a base deficit of 29 mmol/l (milli mole per liter) (3.0±2.7).

Neonatal metabolic acidosis of this degree reflected an accumulation of unbuffered fixed acids in the fetus secondary to a switch to anaerobic metabolism caused by asphyxia [14]. The level of base deficit is predictive of newborn complications. The moderate-to-severe complication risk is as high as 40% when the base deficit exceeds 16 mmol/L at birth [15]. Fetal decompensation will occur if the asphyxia continues and in utero fetal death will result. There is no published time limit to intervene to ensure a favorable outcome, but a comparable clinical condition would be a postmortem cesarean at 36 weeks. Ideally, delivery should occur within 4 minutes [16], although there are data describing successful deliveries after 15 minutes [17]. A ruptured RAA is an unusual cause of shock but there was no clinical evidence of other more common etiologies such as abruptio, placenta previa, amniotic fluid embolus, ruptured uterus, sepsis, or trauma.

The second and most unique component to this case was the incidental finding of an atrophic contralateral kidney. Nephrectomy is usually an unplanned but accepted surgical treatment in the event of RAA rupture, and a right nephrectomy was considered the safest and most expeditious management once she was stabilized [3]. In a case series of 53 pregnant women, 47% with ruptured RAA underwent ipsilateral nephrectomy [9]. In our patient, however, a nephrectomy suddenly became contraindicated based on telephoned information called into the OR from the original imaging center associate with the first ED. Endovascular coiling is highly successful in managing an RAA in a patient with a single functioning kidney, but treatment is evolving [18]. There are multiple endovascular options for the treatment of RAA, and the advantages of these procedures include a shorter hospital stay, minimal invasiveness, and a safe approach with less blood loss and lower postoperative morbidity [19]. Minor early postoperative complications of properly placed coils or stents include bleeding, infections, and transitory renal compromise. Up to 15% of patients have renal infarction [19]. There is no established protocol for postoperative anticoagulation. Most clinicians prescribe either low-molecular-weight heparin or anti-platelet agents administered life-long.

The third important point of this case is the complexity required of a healthcare network facing an evolving medical disaster occurring in 2 separate centers and an affiliated stand-alone imaging center. All of the medical conditions were occurring rapidly and all were life-threatening. Maternal transport from the outlying ED to a higher-level care center became vital [20]. Multiple system resources at the receiving center, including triage, OR, ICU, and NICU (neonatal intensive care unit), are present to diagnose and treat critical care emergencies. However, perhaps the most important element of successful transport is effective communication. Improved communication before and during transport can lead to better patient outcomes [21]. In our case, the most important communication between referring and receiving centers was the last-minute notification of the atrophic right kidney.

Conclusions

This case report details the start-to-finish full maternal vascular collapse from a rare ruptured RAA in the third trimester. The fetus became progressively hypoxic and was profoundly depressed at birth. The communication between essential elements of the care systems and the resources at the receiving center during the treatment of this patient crucially affected the outcome. Continued communication of essential information, even as the case is proceeding in the OR, can be helpful, as demonstrated in this case.