Spontaneous Rupture of a Renal Artery Aneurysm Presenting as Gross Hematuria

Abstract

Renal artery aneurysms (RAAs) are localized dilations of the renal artery and/or its branches. They are being found with increasing frequency as a result of unrelated abdominal imaging or on workup for hypertension. They are rarely symptomatic; however, they can be a cause of life-threatening hematuria. Discussed is the case of a previously healthy 46-year-old man presenting with flank pain and gross hematuria. It is imperative for the practicing urologist to be aware of the appropriate evaluation and management of RAAs.

The patient is a healthy 46-year-old man with no prior history of medical problems who developed the acute onset of left flank pain and gross hematuria 1 day after riding on a wooden roller coaster. He presented to the emergency room 6 days later for evaluation and was found to be anemic with a hemoglobin level of 6.7 and hematocrit level of 19. He was hemodynamically stable. Computed tomographic urogram demonstrated hyperattenuation in the left collecting system and a large clot in the bladder (Figure 1). On arterial phase, there was evidence of an enhancing 3-cm left lower pole renal mass. Magnetic resonance imaging/magnetic resonance angiography (MRI/MRA) confirmed these findings (Figure 2). Cystoscopy and left ureteroscopy revealed active bleeding from the left renal pelvis without a clear identifiable source. An arteriogram demonstrated a 22-mm pseudoaneurysm in the lower pole of the left kidney. This was coiled off selectively and the bleeding stopped immediately.

Figure 1.

(A) Computed tomographic urogram of the abdomen/pelvis demonstrated hyperattenuation in the left collecting system and (B) a large filling defect in the left renal pelvis and bladder suggestive of clot.

Figure 2.

Magnetic resonance imaging/magnetic resonance angiography of the abdomen/pelvis demonstrated enhancement of a left lower pole renal mass.

Discussion

Renal artery aneurysms (RAA) are localized dilations of the renal artery and/or branches. It was the first disease process of the renal artery to be identified and has historically been considered a rare phenomenon until the widespread use of angiography.¹ In 1957, 141 cases of RAA had been reported in the literature¹ and by 1967, this number had risen to well over 300.² A true aneurysm is a balloonlike dilation of all layers of the vessel wall, whereas a false (pseudo) aneurysm is derived from tissues surrounding the arteries.^1,3,4

There are 4 basic structural types: saccular, fusiform, dissecting, and arteriovenous/microaneurysms.⁵ Saccular are the most common and represent 70% to 75% of all RAAs.^1,4,5 Intraparenchymal RAAs are rare and account for < 10% of all RAAs.^4,6 Although rare, there has been a recent increase in the discovery of renal arteriovenous fistulas secondary to trauma, inflammation, renal surgery, and percutaneous needle biopsy.⁷ Approximately 75% of renal arteriovenous fistulas are acquired and easily identifiable by their cirsoid configuration. ⁴ These aneurysms account for 17% of all RAAs and do have the tendency for rupture.⁴

The overall incidence of RAA in autopsy studies ranges from 0.01% to 0.3%^1,5 and has even been reported to be as high as 9.7% in one autopsy study²; however, more recent literature has demonstrated that the overall incidence ranges between 0.01% to 1%.^6,7 This increases to 2.5% when only patients with hypertension are considered^4,6 and as high as 39% in patients with hypertension unresponsive to medical therapy.⁸ The mean age at diagnosis is age 60 years, occurs more commonly in men, and is primarily located on the right.^2,5

RAAs can be either congenital or acquired. Congenital RAAs have been associated with autosomal dominant polycystic disease, fibromuscular dysplasia, and tuberous sclerosis.⁵ Congenital RAAs are frequently located at the bifurcation of the renal arteries and are typically of the fusiform type.^1,4 Acquired etiologies include longstanding untreated hypertension, atherosclerosis, blunt^7,9 and penetrating⁶ trauma, recent surgical manipulation (open, laparoscopic, and/or endovascular),¹¹ angiomyolipomas, infectious (ie, mycotic),¹² polyarteritis nodosa,² malignancy, coagulopathy, radiation, and/or cyclophosphamide use.² Acquired RAAs have a highly variable location^1,6 and size (1 to 10 cm), although most (> 90%) are smaller than 2 cm.⁵ The risk of rupture is thought to vary inversely with size, and most investigators agree that aneurysms larger than > 2 cm are more likely to undergo rupture.⁶ The rupture rate occurs in approximately 30% of cases, with mortality greater than 20%.^4,6

RAAs are frequently asymptomatic, especially in children.¹ Most RAAs are discovered on a workup for hypertension (55%), and are more frequently being discovered incidentally during unrelated abdominal imaging (ie, radiography, color Doppler ultrasound, computed tomography [CT], MRI) or angiography.⁵ When patients do present with symptoms, they usually present with flank pain and hematuria that can range from mild microscopic hematuria to gross hemorrhage leading to hemodynamic instability.^2,4,10,13 Ecchymosis, a palpable or pulsatile abdominal mass, and/or bruits are rare presenting symptoms.¹⁴ A thorough history and physical examination cannot be overemphasized, specifically addressing any previous history of trauma, as there can often be a substantial delay from months to years from the initial insult.⁹

Imaging is required to confirm the diagnosis of a RAA. In one series, only 66% of excretory urograms were diagnostic or suggestive of the presence of a renovascular lesion, whereas angiography was 100% diagnostic.^2,4,10,14 Although angiography is the gold standard, perhaps the best noninvasive test to evaluate location, size, structure, and relation to nearby organs is CT/MRA.⁶ In one study, MRA was able to distinguish between aneurismal-type malformations with a sensitivity, specificity, and accuracy of 78%, 100%, and 91%, respectively.¹⁵ Small cirsoid-type malformations (grade 1 = <2 cm) were not detected in 2 patients. Other imaging modalities that can give clues to the diagnosis include Doppler ultrasound, contrast-enhanced CT, and nuclear scintigraphy.^8,10,12

Although most RAAs are small and asymptomatic, growth is unpredictable and complications may result as they enlarge. Frequently cited complications include dissection, arterial thrombosis, renal infarction, showering of emboli, obstructive uropathy, erosion, and/or spontaneous rupture with hemorrhage.^4,7,16 We report a case of spontaneous renal artery aneurysm rupture into the collecting system presenting as massive gross hematuria in a previously healthy male without prior history of hypertension, renal surgery, or trauma. Severe hematuria resulting from rupture of the RAA into the renal pelvis is fortunately a rare event.

Indications for treatment include hemorrhage, uncontrolled hypertension, pain, progressive enlargement, presence of an arteriovenous fistula, size > 2 to 2.5 cm, or > 1 cm in a female of childbearing age.^2,4,16 Currently, endovascular surgery is the intervention of choice in elective or emergent circumstances.^6,7,10,17 Much literature has surfaced in recent years demonstrating acceptable feasibility and results with endovascular treatment.^6,7,17 Accepted endovascular treatments include embolization (ie, gelfoam, coils, alcohol) or stenting across the aneurysm.^6,17 There have also been case reports of successful management of RAAs with percutaneous thrombin injection directly into the aneurysm.¹¹ Factors that may preclude endovascular management are size and multiplicity, although there have been reports of successful endovascular management of large (10 cm) RAAs endovascularly. ^17,18 RAAs that are not amenable to endovascular therapy may undergo nephrectomy, partial nephrectomy, renal artery grafting, aneurysmectomy, autotransplantation, and/or renal artery ligation.^4,13,19–22

The largest series of renal artery surgery, spanning 35 years, was reported by Henke and colleagues²³ on 121 patients undergoing RAA surgical repair at the University of Michigan. There were no perioperative mortalities; however, there were 8 unplanned nephrectomies. A retrospective review by Pfeiffer and colleagues²² of 94 patients with RAAs undergoing open repair resulted in 1 perioperative mortality, a 17% morbidity rate, and a 97% primary success rate. Similar results were achieved by English and colleagues²⁴ when they examined 72 RAAs over a 16-year period. There was 1 perioperative mortality, a 12% morbidity rate, and a 96% primary success rate.

Conclusions

Although rare, the diagnosis of RAA is being made more frequently with more patients undergoing abdominal aortography and abdominal imaging for unrelated causes. It is imperative for the practicing urologist and clinician to be aware of life-threatening causes of gross hematuria, appropriate evaluation and imaging of suspected RAAs, endovascular management, operative indications, and techniques.

Main Points.

• Renal artery aneurysms (RAAs) are localized dilations of the renal artery and/or branches. Saccular aneurysms are the most common form representing 70% to 75% of diagnosed RAAs; intraparenchymal RAAs are rare and account for only < 10%.

• Most RAAs are discovered during workup for hypertension (55%), and are more frequently being discovered incidentally during unrelated abdominal imaging (ie, radiography, color Doppler ultrasound, computed tomography, magnetic resonance imaging) or angiography. When patients do present with symptoms, they are usually in the form of flank pain and hematuria that can range from mild microscopic hematuria to gross hemorrhage that leads to hemodynamic instability.

• Indications for RAA treatment include hemorrhage, uncontrolled hypertension, pain, progressive enlargement, presence of an arteriovenous fistula, size > 2 to 2.5 cm, or > 1 cm in a female of childbearing age. Currently, endovascular surgery is the intervention of choice in elective or emergent circumstances.

• Health care practitioners should be aware of life-threatening causes of gross hematuria, appropriate evaluation and imaging of suspected RAAs, endovascular management, operative indications, and techniques.