Fig. 1. Severe proximal stenosis of the proximal left renal artery.	Fig. 2. DSA demonstrates forward migration of the partially expanded renal stent.

Case Reference No. CC-497-01 A 75-year-old female with hypertension and a known left renal artery stenosis was referred for renal angioplasty and possible stent placement prior to repair of her thoracoabdominal aneurysm. The stenosis was dilated with a 5 x 2-mm PTA balloon. Angiography revealed a 40% residual stenosis. Repeat PTA using a 6-mm balloon effaced the stenosis, but created a small dissection flap that was thought to potentially limit flow. A 1.5-cm long Palmaz stent was hand-mounted and crimped onto a 6 x 2 Medi-Tech Diamond balloon. Prior to stent mounting, the balloon was repeatedly wiped with a wet gauze to remove the silicone coating. As soon as inflation of the stent bearing balloon began, the stent migrated forward off the balloon and into the renal artery beyond the stenosis ("watermelon-seed effect") (Fig. 2). We were unable to advance any balloon catheters through this stent, despite ultimately switching to an 0.018-inch guidewire and 3.8-F balloon. In order to retrieve the stent, a 1-cm loop snare was advanced paraxially (over the luminal guidewire) to the trailing edge of the stent. Attempts to pull the stent through the femoral access proved unsuccessful because one of the trailing "tines" of the stent had bent outwards at a 90 degree angle to the stent. The stent was held by the snare in its minimally expanded state within the right common iliac artery.

Fig. 3. The stent is retracted into the right external iliac artery. A bent tine is faintly seen (arrow). Fig. 4. Final position of the stent expanded across the external iliac artery stenosis.

Using a contralateral approach, a second snare was used to grasp the stent lumen wire and draw this wire out through the left femoral sheath. (Fig. 3). A 6-mm 3.8-F balloon was passed through the stent from this contralateral approach. The stent was then positioned across a marked focal narrowing in the right external iliac artery and expanded. A second attempt at renal stent placement was not performed. Her blood pressure was improved the next morning. Questions 1) Has anyone had a similar experience mounting stent upon this particular balloon (Diamond)? We experienced stent slippage despite following instructions for using this reportedly "stent-ready" balloon and have real reservations about using this system again for stent delivery. 2) How common is stent placement of proximal ostial lesions independent of angiographic outcome (i.e. primary stent placement)? 3) Any comments on, or other techniques or tips for, handling a migrated stent (through which a balloon could not be passed in a prograde fashion)?