Aorta–Left Renal Vein Fistula in a Woman

Abstract

Spontaneous rupture of an abdominal aortic aneurysm into a retroaortic left renal vein is an uncommon occurrence. A 55-year-old woman presented with shortness of breath, vomiting, and diffuse abdominal pain that had radiated to her back and legs for the preceding 10 days. A pulsatile abdominal mass, hematuria, renal insufficiency, and heart failure were present at the initial evaluation. Computed tomography showed an infrarenal abdominal aortic aneurysm that communicated with a retroaortic left renal vein. After urgent surgical repair, cardiac and renal function were dramatically improved. To the best of our knowledge, this is the 1st reported case of a woman with such a fistula. We review treatments reported in the literature.

Spontaneous aorta–left renal vein fistula (ALRVF) caused by abdominal aortic aneurysm (AAA) is a very rare clinical entity.¹ In 1964, Lord and associates² reported the 1st case of a patient with ALRVF. Since then, fewer than 25 cases (all of them involving male patients) have been reported in the English-language literature.^3,4 Aorta–left renal vein fistula is a rare but well-described pathologic condition. We report a case of ALRVF in a woman who had high-output cardiac failure. To the best of our knowledge, this is the 1st report of surgery on a female for aorta–retroaortic left renal vein fistula and abdominal aortic aneurysm.

Case Report

In May 2002, a 55-year-old woman presented at a local hospital with shortness of breath, vomiting, and diffuse abdominal pain that had radiated to her back and legs for 10 days. She had a known history of hypertension and hyperlipidemia. The patient was admitted to that hospital. Abdominal ultrasonography revealed a 7-cm infrarenal AAA. Noncontrast computed tomography (CT) demonstrated isolated infrarenal AAA, for which condition the patient was transferred urgently to our institution's cardiovascular surgical department.

Upon the patient's admission, physical examination revealed a systemic arterial blood pressure of 145/60 mmHg. The electrocardiogram revealed sinus tachycardia. The patient had bilateral pulmonary rales and bilateral lower-extremity edema. A large pulsatile epigastric mass was detected without an audible systolic abdominal bruit. She had oliguric acute renal failure. Significant laboratory values were blood urea nitrogen of 43 mg/dL, creatinine of 2.7 mg/dL, and microscopic hematuria and proteinuria. Echocardiography showed good left ventricular function, moderate right ventricular enlargement with increased pulmonary artery systolic pressure of 54 mmHg, and no valvular pathology. A contrast-enhanced CT scan demonstrated an infrarenal AAA, which was 7.0 cm at its maximum diameter. There was a retroaortic vascular structure, which communicated with the aortic lumen. Early detection of equal contrast material in this vascular structure and the vena cava suggested an ALRVF (Fig. 1). The patient was taken to surgery the following morning.

Fig. 1 Axial section from a contrast-enhanced computed-tomographic scan shows equal opacification of infrarenal aorta, retroaortic left renal vein, and inferior vena cava.

AAA = abdominal aortic aneurysm; LRV = left renal vein; VCI = vena cava inferior

Intraoperatively, a palpable thrill on the infrarenal aneurysm was noted at the time of abdominal exploration. The left renal vein was not in its normal anatomical position anterior to the aorta. Because of the proximal extent of the aneurysm, the aorta was cross-clamped obliquely distal to the right renal artery and proximal to the left renal artery. Clamps were placed distally on the common iliac arteries. When the aneurysm was opened, venous backflow from the posterior wall of the aneurysm was noticed. The bleeding was controlled by the surgical assistant, who performed compression proximal and distal to the fistula with 2 swab sticks. The fistula, which was 1.5 cm in diameter, was oversewn with 3-0 polypropylene sutures (Fig. 2). The aneurysm was repaired with an 18-mm straight Dacron graft.

Fig. 2 Operative approach to aorta–left renal vein fistula. The fistula was repaired through the open aneurysm.

VCI = vena cava inferior; X-Clamp = cross-clamp

Elevated right ventricular pressure and high cardiac output with low systemic vascular resistance, which had been detected preoperatively by pulmonary arterial catheterization, were corrected by surgical repair (Table I). Postoperative duplex scanning revealed normal blood flow in the retroaortic left renal vein (Fig. 3). Postoperative echocardiography showed elevated pulmonary arterial pressure and regression of right ventricular overload. The patient was discharged from the hospital with a serum creatinine level of 0.9 mg/dL, after an uncomplicated postoperative course. She was in good condition at her 1-year follow-up.

TABLE I. Comparison of the Pre- and Postoperative Hemodynamic Variables

Fig. 3 Postoperative duplex scan reveals unobstructed blood flow in the retroaortic left renal vein.

AO = aorta; LRV = left renal vein; VCI = vena cava inferior

Discussion

During the development of the inferior vena cava, anastomotic communications develop between the subcardinal and supracardinal channels, which process is called subsupracardinal anastomosis.⁵ These connections form a collar of veins that encircles the aorta. The ventral portion of the circumaortic collar persists as the normal left renal vein. If the dorsal portion of this collar does not disintegrate, the left renal vein is posterior to the aorta, forming a retroaortic left renal vein.⁶ Failure to recognize this anomaly can lead to inadvertent injury and major venous bleeding.⁷ A retroaortic left renal vein can also form a fistula to the AAA, but this occurrence is very rare.⁶ Fewer than 25 cases have been reported in the English-language literature,^3,4 and all those patients have been male. The cause of the fistula is spontaneous aneurysmal rupture into the left renal vein. Spontaneous rupture into the retroaortic left renal vein might possibly be caused by intense periaortic inflammatory reaction or by pressure-related necrosis.

As described by others,³ this complication is usually accompanied by abdominal pain, hematuria, and a dysfunctioning left kidney. Other common clinical manifestations are pulsatile abdominal mass, audible continuous abdominal bruit, and hematuria. Renal function usually becomes abnormal, likely due to increasing venous pressure in the renal veins, which leads to lower glomerular filtration rates. Hematuria is a warning sign for ALRVF and is due to elevated renal venous pressure that leads vascular channels to communicate directly with the caliceal cavity. In addition, proteinuria is a prominent feature of kidneys affected by venous hypertension. Sudden onset of cardiac failure, especially when it is of the high-output type with no obvious cause, can indicate a large arteriovenous communication such as aortocaval fistula.⁸ Although it is an unexpected situation, ALRVF with high-output cardiac failure must be kept in mind. Signs of left renal vein hypertension (hematuria, proteinuria) are infrequent findings of aortocaval fistula. The nutcracker syndrome (left renal vein compression between the aorta and the superior mesenteric artery) and aortocaval fistula often present similar clinical pictures. The symptoms of nutcracker syndrome are more episodic and intermittent than are those of ALRVF, and AAA is not present.⁹

The extent of the clinical manifestations of ALRVF depends on the size, duration, and location of the fistula. As in the present case, a large fistula and the ensuing central venous hypertension leads to a compensatory increase in cardiac output and plasma volume. A simultaneous decrease in systemic vascular resistance due to left-to-right shunting results in a hyperdynamic circulation characterized by increased stroke volume, heart rate, and cardiac output.

A preoperative diagnosis can be made with the aid of contrast-enhanced CT scanning. Familiarity with this venous anomaly and careful examination of the CT scan can yield an accurate preoperative diagnosis. An intraoperative thrill over the aneurysm or an absent left renal vein anterior to the aorta should raise suspicion of ALRVF.

Open repair is the recognized method of treating rupture of an abdominal aortic aneurysm into a retroaortic left renal vein. Once the precise diagnosis has been made, surgical closure of the fistula and repair of the aneurysm with a graft is relatively easy and safe.

Endovascular stenting might be an alternative that avoids the substantial blood loss sometimes encountered in conventional repair. To the best of our knowledge, Sultan and co-authors¹⁰ reported the 1st and only case of ALRVF in which endovascular techniques were used in conjunction with open surgery. Although total endovascular management was not successful in that patient, the initial endovascular approach improved the patient's clinical status enough to lower the risk attendant upon subsequent surgery. Patients with renal dysfunction may present in unstable condition due to volume overload, and the clinical picture can be complicated by the use of nephrotoxic contrast agents. Initial endovascular management might be considered in high-risk patients, as a bridge to definitive treatment after hemodynamic stabilization and optimization.

During surgical exposure of the aorta, the absence of an anterior left renal vein from its usual anatomic position raises the probability of retroaortic left renal vein. Circumferential dissection of the proximal aorta in order to apply the proximal cross-clamp to the retroaortic left renal vein and explore it is dangerous and unnecessary. When the aneurysm is opened, prompt control of the fistula can be achieved by compression on either side with sponge sticks. Preoperative diagnosis is crucial to adequate preparation; an autotransfusion device, for example, must be on standby before the aortotomy, to prepare for substantial blood loss.

Conclusion

Aorta–left renal vein fistula caused by an AAA is an extremely rare entity in patients with a retroaortic left renal vein. The overwhelming majority of patients with ALRVF are male. The possibility of such a fistula should be kept in mind in diagnosing patients who present with abdominal pain, renal dysfunction, hematuria, pulsatile abdominal mass, cardiac failure, and widened pulse pressure. Preoperative diagnosis can be accomplished with the careful interpretation of CT scans. The results of surgical treatment for this condition have been favorable when preoperative localization has been precise and the operative technique cautious. Cardiac and renal abnormalities are rapidly reversed after surgical closure of the fistula.