Symptomatic Hydronephrosis from Renal Artery Aneurysm Associated with Fibromuscular Dysplasia: Management with Transarterial Embolization

Case Report

A 56-year-old woman presented with right-sided flank pain, pain in the upper abdomen, dizziness, and nausea. She had a history of recurrent right flank pain for several years. Oral medication was given for mild hypertension and hypothyroidism. Her surgical history included hysterectomy, appendectomy, and cholecystectomy. Clinical examination of the right flank was painful. Otherwise, the physical examination was normal.

The laboratory and urinary findings were within normal limits. Examination with ultrasonography (US) detected hydronephrosis of the right kidney. This had been diagnosed with US a few years ago, however. Unenhanced and contrast-enhanced CT was then performed to evaluate the upper urinary tract. A nodular mass (Fig. 1) was detected at the ureteropelvic junction of the right kidney with a maximum diameter of 2 cm. The contrast phase revealed the nodular mass as a distal aneurysm of the right renal artery compromising the ureteropelvic junction. When CT images from 2006 were retrospectively reviewed, the renal artery aneurysm of the right kidney could be identified with approximately the same diameter but with a lesser extent of hydronephrosis.

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FIG. 1.

CT angiography shows an aneurysm of the right distal renal artery compromising the ureteropelvic junction.

Cystoscopy was performed. Retrograde pyelography revealed an obstruction at the ureteropelvic junction with subsequent pelvicaliceal dilatation. Finally, an ureteral Double-j stent was placed because of prolonged flank pain.

Angiography was performed via the transfemoral approach with a 7F introducer. Unfractionated heparin (1000 IU) was administered intravenously. Selective diagnostic angiography with injection into the right renal artery confirmed the diagnosis of a distal renal aneurysm (Fig. 2A). Moreover, angiography incidentally detected fibromuscular dysplasia (FMD) of both renal arteries. The aneurysm was interpreted to be FMD related, most likely by a clinically silent dissection a long time ago.

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FIG. 2.

Angiography before intervention demonstrates the tip of the catheter in the right renal artery, which shows the aneurysm. The atypical appearance of the fibromuscular dysplasia can be observed in the renal artery (black arrow). (A) Pre-embolization. (B) Filling the basket: Supraselective catheterization of the renal artery aneurysm allows the tip of the microcatheter to be positioned in the dome of the aneurysm (white arrow). The coils then can be deposited safely within the aneurysmal sac. Here, the deposit of the initial and largest coils (18 mm) is demonstrated. (C) Postembolization control series: Digital substraction angiography revealed preserved perfusion of the complete renal parenchyma after coil delivery. The contrast filling of the aneurysmal sac has already markedly decreased. As a second step, the two inserted bioactive coils will further obstruct the aneurysmal sac by swelling of their coating.

The diagnostic angiography was followed by supraselective catheterization of the renal aneurysm. The initial concept to use a stent graft to occlude the aneurysm was withdrawn with the diagnosis of FMD. The neck of the aneurysm and the aneurysm itself were approached with Excelsior 1018 microcatheter (Boston Scientific, Cork, Ireland) by 0.14 Galeo microwire (Biotronik Inc., Lake Oswego, OR). Neuroradiological coils (GDC Standard and GDC 3D, Boston Scientific, Cork, Ireland) were chosen to form the basket with bioactive coils (Interlock,™ Boston Scientific, Cork, Ireland) for the filling. Initially, a GDC 3D (18 mm × 40 cm) coil was delivered into the aneurysm (Fig. 2B), followed by two GDC Standard (16 mm × 30 cm and 12 mm × 30 cm), and two Interlock 2D coils (14 mm × 30 cm and 10 mm × 30 cm), respectively. Finally, control series were acquired to ensure almost complete occlusion of the lesion (Fig. 2C).

As expected, slow residual filling of the contrast material in the aneurysm was present, but there was no compromise of the parent vessel. The postinterventional course was uneventful. Contrast-enhanced CT was performed 3 months after the intervention to evaluate the aneurysm. A filling of the aneurysm was not observed (Figs. 3A, B). Therefore, the ureteral Double J-stent was removed. The patient was then evaluated with US of the kidney and laboratory tests (creatinine) after 1, 3, and 6 months. Short-term 6-month follow-up was excellent regarding pain, laboratory findings (creatinine level 0.5 and 0.6 mg/dL) and kidney dilatation (no dilatation).

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FIG. 3.

(A, B) Postembolization CT control series: A control CT scan 3 months after the procedure revealed no residual perfusion of the aneurysm (arterial phase).

Discussion

This case represents a unique mixture of rare conditions, which is diagnostically and therapeutically challenging: A distal renal artery aneurysm associated with FMD that is causing symptomatic hydronephrosis. Renal artery aneurysms are rare, with an incidence up to 1%. These aneurysms are generally asymptomatic, but complications can occur, including arteriovenous fistula formation and, rarely, rupture of the aneurysm leading to nephrectomy or death. ^1,2 Because of the retroperitoneal location of the aneurysm and the possibility of self-tamponade, rupture may not be life threatening. Symptomatic hydronephrosis, however, made further therapy necessary.

The prevalence of asymptomatic renal artery FMD is not precisely known, with clinically significant renal artery FMD being about 0.4%. ³ Interestingly, a strong association of renal artery aneurysm with renal artery FMD was demonstrated. All patients in these series with renal artery aneurysms had FMD, even though only 16 patients with renal artery aneurysms were identified and analyzed. ^4,5

Renal artery aneurysm causing hydronephrosis, however, is a rare entity with few case reports in the literature. ^{6 –10} Control of the aneurysm was achieved by open surgery because of the large size of the reported aneurysms. ^{8 –10} In our case, hydronephrosis was caused by an inappropriate position of a relatively small aneurysm 2 cm in diameter. Therefore, a minimally invasive approach was pursued to reduce the risk of complications that are associated with an open procedure.

Transarterial embolization (TAE) has been used successfully for managing renal artery aneurysms and arteriovenous malformation of the kidney. ^{11 –15} Many investigators have reported its usefulness regarding rapid recovery, short hospital stay, and early resumption of physical activities. The choice of intervention is largely dependent on the anatomy of the aneurysm, and because there have not been any large series of percutaneous interventions, the optimal choice is unknown. ¹⁴ In addition, reduction in blood pressure and a decreased need for antihypertensive medications has been well documented after surgical interventions for renal artery aneurysm. ² Whether the same systematic benefit exists after percutaneous intervention is unknown because of the small number of case reports.

In our case, TAE allowed identification and therapy of the aneurysm, obviating the need for open surgery and risk of additional morbidity and complications. Giving the excellent short-term outcome in this rare entity, we suggest consideration of embolization in similar situations.

Conclusion

We present the rare case of hydronephrosis due to distal renal artery aneurysm associated with fibromuscular dysplasia. We conclude that diagnosis by CT angiography and supraselective embolization of the renal aneurysm is an option to minimize morbidity associated with an open procedure.