Cause of a rare acute renal insufficiency: Rupture aortocaval fistula

Introduction

Chronic fistulation between an abdominal aortic aneurysm and the inferior vena cava is an unusual entity. It is one of the less well-recognized complications of abdominal aortic aneurysm. We report a case which was presented by acute renal insufficiency as a consequence of ruptured aortocaval fistula.

Case report

A 56-year-old man was admitted to the hospital for abdominal pain and leg oedema of three days duration. Oedema of bilateral lower extremities was a sign of venous stases. Severe anuria was also noted.

Laboratory data included blood urea nitrogen (BUN) 94 mg/dl, creatine 4.05 mg/dl, serum potassium 5.06 mEq/l and hematocrit level 40%.

Thus, the patient was referred to an urgent abdominal computerized tomography (CT) angiography. Angiography also showed a fistula from the right lateral wall of aneurysm to the distal of vena cava inferior (Figure 1).

OPEN IN VIEWER

Figure 1.

View of aortocaval fistula in three-dimensional CT angiography.

At operation, the aneurysm was opened and the large fistulous opening between aneurysm and the inferior vena cava was visualized.

The defect was closed with pledged-reinforced 4/0 polypropylene suture by several interrupted sutures in the aneurysmal wall. Aorto-iliac synthetic graft was tailored into the aorta and iliac arteries.

Fourteen hours after the operation, the patient’s legs oedema was turned to normal. On the first postoperative day, 650 ml diuresis was started. On the second postoperative day, the amount of urine output increased to 1850 ml. But the laboratory data included BUN 144 mg/dl, creatine 4.55 mg/dl and potassium 5.5 mEq/l. He was dialysed two times. At the postoperative 10th day, his urine nitrogen and creatinine values returned to normal. He was discharged with normal renal function.

Discussion

Abdominal aortic aneurysms can be complicated by some conditions and aortocaval fistula is one of them. It is seen in 1% of all abdominal aortic aneurysms and 4–5.5% of ruptured aneurysms. ¹ Ruptured abdominal aortic aneurysms have an overall mortality of 49% even in operated patients ² and aortocaval fistula is a factor that contributes to this result.

In our case, the patient had a serious oedema in the lower extremity which was a sign of increased venous pressure.

For an adequate renal perfusion, venous pressure is also important in addition to the arterial blood flow. In our patient, acute kidney failure had developed as a consequence of increased venous pressure. The decrease in venous pressure and dramatic amelioration of kidney functions after the operation was the indicator of this mechanism.

We have more than one imaging modality in the diagnosis of aortocaval fistulas. CT angiography and magnetic resonance (MR) angiography are the options.^3–5 Because of the absence of MR imaging machine in our institution, we used CT angiography.

Even after the diagnosis of aortocaval fistulas in elective conditions, some factors can complicate the process and increase morbidity and mortality. Precautions should be made to avoid excessive bleeding, deep vein thrombosis or pulmonary embolism and hemodynamic instability during the operation. Inferior vena cava filters or balloon catheters which were inserted before the procedure can be a preventive method for pulmonary embolism and deep vein thrombosis.^6,7 We did not have any opportunity for any other interventional procedure and we had to take the patient to operation room immediately because of the rapid fall in the hematocrit levels, deteriorations of his clinical condition and acute kidney failure.

Pitting oedema was turned to normal in the 14th hour after the operation. Urine output was turned to normal in the second postoperative day. The patient was discharged with normal renal function and structure of legs.

Aortocaval fistula is a rare pathology, and therefore a vascular surgeon’s possibility to experience such a case is low. We believe that correct surgical intervention with the symptomatic treatment of clinical deteriorations in the follow-up can provide satisfactory outcomes.