Quiz Page February 2009: Unilateral Urinary Obstruction in a Man With Peripheral Vascular Disease

What is the differential diagnosis in a patient with these features? 

There are many possible causes of unilateral urinary tract obstruction, such as carcinoma of the urinary tract, retroperitoneum, or pelvis; retroperitoneal fibrosis; stricture of the urinary tract; vascular anomaly of the abdominal aorta; and calculi. Considering the patient's advanced age and history of peripheral vascular disease, it should be emphasized that all patients with unexplained hydronephrosis must be evaluated for a vascular anomaly. Abdominal computed tomography showed a 9 × 6 × 4-cm left internal iliac artery aneurysm compressing the distal left ureter (Fig 1). It was fusiform shaped, with a large portion of aneurysm filled with thrombus. The superior portion of the aneurysm was located 3 cm distal to the origin of the left internal iliac artery. The inferior portion was located posterior to the bladder with compression of the uretovesicular junction. The lumen of the aneurysm opened just before the left internal iliac artery bifurcated into anterior and posterior divisions (Fig 1A to C).

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Figure 1. Computed tomography and computed tomographic angiogram at admission. (A) Marked hydronephrosis (arrow) was noted on the left kidney. (B) Aneurysmal sac was filled with contrast media (arrow) and compresses the ureterovesicalar junction. (C) Aneurysmal sac (arrow) located just below the left iliac artery bifurcation site.

What is your diagnosis? 

The diagnosis was a left internal iliac artery aneurysm causing obstruction of the left ureter and hydronephrosis. Percutaneous nephrostomy was performed, with marked improvement in flank pain. Two days later, aortography and aneurysm embolization with 3 microcoils (6 × 4, 5 × 4, and 4 × 3 cm) occluded the lumen of the aneurysm. A double J catheter was inserted into the left ureter until the aneurysm resolved. One month later, the patient's kidney function returned to its previous level, with a serum creatinine level of 0.7 mg/dL (62 μmol/L) and eGFR of 82 mL/min/1.73 m2. Five months later, the double J catheter was removed without recurrence of hydronephrosis or flank pain.

An internal iliac artery aneurysm is defined as a 2-fold increase in the diameter of the artery. It is unusual, with an incidence of 0.4%. It is much more common in men, with a male-female ratio in most studies of 6:1 or greater.1 Urinary tract obstruction caused by iliac artery aneurysm is rare, with 4 cases of hydronephrosis previously reported in the literature. Obstructive uropathy can also occur after aortofemoral bypass graft and obstruction extrinsic compression of the ureter by the graft.2 The aneurysm typically grows at a rate of 4 mm annually, exposing the patient to a risk of rupture.3 An early diagnosis with prompt management before rupture is the treatment of choice. Although perianeurysmal fibrosis and inflammation cause the obstruction in most cases, this patient represents a case of left ureter and bladder compression by a huge aneurysm without inflammatory reaction. Although surgical resection was necessary in the past, iliac artery aneurysm can now be treated successfully by using endovascular techniques.4, 5, 6, 7