Renal artery stenting for intimal flap injury in a 2-year-old child after blunt abdominal trauma.

Abstract: Injury to the renal vasculature is an uncommon occurrence in the setting of blunt abdominal trauma. The authors report the case of a 2-year-old girl who developed occlusion from an intimal flap in a renal artery (grade IV renal injury) after blunt abdominal trauma that was treated with a stent placement. The stent procedure was technically successful in establishing renal artery flow. However, several months after the procedure, the patient developed stenosis within the stent and ultimately required a nephrectomy. To the authors' knowledge, this is the first report of percutaneous management of an acute intimal flap in a renal artery in a 2-year-old.

Key Words: pediatric trauma, blunt injury, renal artery injury, stent

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Approximately 1 to 4% of blunt abdominal trauma results in renal artery injury. (1'2) A review of 250 documented cases of renal arterial injury after blunt trauma suggests that one-third of such injuries occur in children. (3) Injuries can range from intimal tears to complete transection of the renal artery. Intimal tears can progress to pseudoaneurysms, dissection, or thrombosis, all of which can lead to occlusion of the vessel lumen and compromise of renal perfusion.

Percutaneous treatment for such traumatic injuries in the renal arteries has been reported (see Table), but all in adult patients. To our knowledge, we present the first case of emergent percutaneous management of an acute intimal tear in a renal artery with a stent in a 2-year-old child.

Case Report

A 2-year-old healthy girl was hanging from a table when it fell corner-first onto her abdomen. She had right-sided abdominal pain and nonbloody emesis. Her parents reported no loss of consciousness or change in mental status.

The patient was initially seen at an outside hospital. Abdominal examination revealed right-sided ecchymosis and mild guarding. Physical examination was otherwise unremarkable. She was subsequently transferred to the trauma center for further evaluation almost ten hours after the injury. Initial workup included an abdominal computed tomography (CT) with intravenous (IV) contrast that revealed lack of contrast perfusion in the right kidney (Fig. 1), a sign of the renal artery injury. This was confirmed with a Doppler ultrasound examination. An emergent arteriogram revealed complete occlusion of the main right renal artery (grade IV renal injury) by an intimal flap (Fig. 2).

Because of the extended renal ischemia time, it was felt that surgical revascularization of the renal artery had a low probability of success, yet was technically challenging with high potential morbidity. In an attempt to salvage the patient's renal function, recannalization and angioplasty of the renal artery was performed with restoration of flow through the main right renal artery. Soon after angioplasty, the renal artery reoccluded secondary to the persistent intimal flap. A balloon-expandable stent was placed (Fig. 3) and resulted in full restoration of blood flow. Approximately twelve hours elapsed between the injury and restoration of flow to the kidney.

A follow-up abdominal CT scan with contrast (Fig. 4) showed perfusion of the right kidney. The patient maintained adequate urine output with no significant change in glomerular filtration rate (GFR) after stent placement. A repeat duplex scan two days later showed a patent main renal artery with normal velocity. The patient was discharged on warfarin, and the family was instructed to keep weekly follow-up visits.

The patient remained asymptomatic for two months following stent placement with no change in urinary habits or hematuria. After two months, however, the patient's blood pressure started to elevate (150-160/90-120). A renal ultrasound showed the right kidney had reduced in size from 8.1 to 5.8 cm longitudinally, and there was suggestion of in-stent stenosis of the main right renal artery by velocity. As the kidney began to reduce in size and the patient became hypertensive, the parents agreed to a laparoscopic right nephrectomy. Pathology showed focal capsular soft tissue hemorrhage and zonal parenchymal scarring (subcapsular and transcortical) with some involvement of the medulla as well. Unfortunately, there were no pathologic details about the renal artery and stent. The child's blood pressure returned to a normal range over a period of four weeks.

Technique

We performed the procedure under general anesthesia due to her age. Right femoral arterial access was achieved under ultrasound guidance, and diagnostic angiography was performed using pediatric 4-French pigtail catheter. We recannalized the occluded right renal artery with 0.035 inch hydrophilic glide wire (Terumo Medical, Somerset, NJ) over a 6-French double renal curve guiding catheter (Guidant, Temecula, CA). After confirming intraluminal location by contrast injection, we performed an initial percutaneous transluminal angioplasty (PTA) with a 2.0 mm x 9.0 mm balloon (Guidant, Santa Clara, CA) over 0.014 inch wire (Boston Scientific, Miami, FL) where the main renal artery measured 2.25 mm in diameter with distal tapering. Prolonged inflation of a 2.5 mm x 9.0 mm balloon at nominal pressure was performed to treat persistent dissection flap. We chose primary PTA rather than stenting due to our patient's young age, with expected future growth necessitating frequent interventions with stenting and potential intimal hyperplasia causing in-stent stenosis. Re-occlusion with persistent dissection flap, however, necessitated stent placement. We placed a 2.25 mm diameter x 8 mm long balloon-expandable stent (Boston Scientific, Maple Grove, MA) over 0.014 inch wire (Boston Scientific, Miami, FL) and overdilated to 2.5 mm proximally to better approximate the artery. We chose a balloon-expandable stent for its availability in a small diameter size and its ability to be overdilated in the future for expected growth of the renal artery. The stenting restored flow with no pressure gradient across the stent. During the procedure, the patient received a pediatric bolus dose of IV heparin at 70 cc/kg of body weight and 40 cc of contrast (Omnipaque 350, [Iohexol]; Nycomed, Princeton, NJ) which is less than 5 cc/kg of body weight recommended for pediatric patients.

Discussion

The treatment of acute renal arterial injury continues to be controversial. When considering treatment options, factors such as unilateral versus bilateral injury, the number of preexisting functional kidneys, the duration of ischemia time, concomitant injuries, and the extent of arterial luminal occlusion must be considered.

The ability of the kidney to tolerate warm ischemia is controversial and has obvious implications for the selection of treatment modalities. It is believed that, like other end organs with a single inflow artery, ischemic changes to the kidney become irreversible in only a few hours. (4'5)

It is clear that surgical revascularization or stent placement should be attempted in patients with bilateral injury or a solitary kidney. In these situations, success should be defined by the deferral of dialysis. (3) In contrast, the optimal treatment in unilateral renal artery injury in a patient with two kidneys is a challenging dilemma. The primary treatment modalities are surgical revascularization, endovascular angioplasty or stenting, and observation. Due to the infrequency of renovascular injuries following blunt trauma, there are no prospective clinical trials comparing the above modalities.

Open revascularization after renal artery injury in the setting of blunt abdominal trauma is the standard of care at many trauma centers. However, there have been few large class II (retrospective studies) and no class I (prospective, randomized) studies evaluating the outcome of revascularization. The reported success rates of revascularization of a unilateral renal artery injury in three large studies of blunt trauma range from 23 to 38%. (2,6,7)

Based on the literature, successful revascularization is rare after 19 hours of renal ischemia, although there is at least one report of restored renal function postrevascularization with a prolonged ischemia time of 48 hours (7) The reported risk of renovascular hypertension after revascularization range from 3 to 33%. (2,3,6,7)

Observation of renovascular lesions is often recommended when ischemia time is "prolonged." Some also recommend that intimal flaps with patent arteries should be observed. This is based on the observation that intimal injuries created by balloon angioplasty can often be managed without revascularization. However, even partial intimal injuries may thrombose and lead to total occlusion of the renal artery. Such an occurrence would be difficult to diagnose given the often occult nature of such an injury, and this would almost certainly lead to loss of renal function unless the cadence of luminal occlusion is prolonged to allow the development of collateral vessels. Furthermore, the reported risk of renovascular hypertension in nonoperative treatment ranges from 6 to 42%, which is comparable to the risk reported for patients who undergo surgical revascularization. (2,3,6,7)

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There are few cases in the literature describing the use of stents in renovascular trauma. (Table 1) (8-12) Although these class III papers report excellent short-term success rates, follow-up data is short. The natural history of such patients needs to be better characterized.

Given the poor success rate of surgical revascularization, we believe that stenting of the renal artery offered the best chance for maximal preservation of renal function in our patient. In doing so, we also avoided the potential morbidity associated with an open procedure. We felt that the chance of preserving some renal artery function was worth the low morbidity associated with stent placement. We chose a balloon-expandable stent for its small available size (2.25 mm in diameter and 8 mm in length) to minimize the stented area and its ability to afford over-dilation to approximate larger diameter renal artery as the child grows over time.

The child, however, developed hypertension and underwent a nephrectomy. The etiology for reduction in kidney size is likely due to the initial ischemic damage to the kidney parenchyma, which, over the course of twelve hours, was irreversible, despite eventual restoration of renal artery flow. In-stent stenosis due to intimal hyperplasia may also have occurred.

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Given the high association of renovascular injuries with other serious intra-abdominal injuries, treating renovascular injuries without the need for an open procedure should be of benefit. We believe that stenting for renal artery injury even with complete occlusion is a promising treatment option that deserves further evaluation.

References

1. Brown MF, Graham JM, Mattox KL, et al. Renovascular trauma. Am J Surg 1980;140:802-805.

2. Lock JS, Carraway RP, Hudson HC Jr., et al. Proper management of renal artery injury from blunt trauma. South Med J 1985;78:406-410.

3. Clark DE, Georgitis JW, Ray FS. Renal arterial injuries caused by blunt trauma. Surgery 1981;90:87-96.

4. Magilligan Jr. DJ, DeWeese JA, May AG, et al. The occluded renal artery. Surgery 1975;78:730-738.

5. Vollmar J, Helmstadter D, Hallwachs O. Complete occlusion of the renal artery: Nephrectomy or revascularization? J Cardiovasc Surg (Torino) 1971;12:441-446.

6. Bruce LM, Croce MA, Santaniello JM, et al. Blunt renal artery injury: incidence, diagnosis, and management. Am Surg 2001;67:550-554.

7. Haas CA, Sprinak JP. Traumatic renal artery occlusion: a review of the literature. Tech Urol 1998;4:1-11.

8. Whigham Jr. CJ, Bodenhamer JR, Miller JK. Use the Palmaz stent in primary treatment of renal artery intimal injury secondary to blunt trauma. J Vase Interv Radiol 1995;6:175-178.

9. Villas PA, Cohen G, Putnam SG 3rd, et al. Wallstent placement in a renal artery after blunt abdominal trauma. J Trauma 1999;46:1137-1139.

10. Lee JT, White RA. Endovaseular management of blunt traumatic renal artery dissection. J Endovasc Ther 2002;9:354-358.

11. Goodman DN, Saibil EA, Kodama RT. Traumatic intimal tear of the renal artery treated by insertion of a Palmaz stent. Cardiovasc Intervent Radiol 1998;21:69-72.

12. Dobrilovic N, Bennett S, Smith C, et al. Traumatic renal artery dissection identified with dynamic helical computed tomography. J Vase Surg 2001;34:562-564.

Wesley Hsu, MD, Sally E. Mitchell, MD, and Hyun S. Kim, MD

From Johns Hopkins University School of Medicine, Baltimore, MD.

Reprint requests to Hyun S. Kim, MD, 600 North Wolfe Street, Blalock 545, Baltimore, MD 21287. Email: [e-mail]

Accepted November 8, 2005.

RELATED ARTICLE: Key Points

* We illustrate that it is technically feasible to place an intravascular stent to repair an intimal flap in the renal artery of a pediatric patient.

* We seek to highlight the controversy in management of acute renal artery injury by reviewing both the literature on the efficacy of surgical repair as well as the limited literature on the use of stents to repair acute renal artery injury.

* We highlight the importance of clinical follow up for patients with injuries to the renal vasculature.

Table. Summary of renovascular injury with stent placement

                         Patient's
Author                   age (year)  Type of injury

Whigham et al (1995)     28          Circumferential linear intimal
                                       defect 2 cm from ostium with
                                       good renal perfusion
Goodman et al (1998)     23          Eccentric linear intimal defect 3
                                       cm from ostium with 90% stenosis
Villas et al (1999)      37          Focal intimal defect with 75%
                                       stenosis
Dobrilovic et al (2001)  25          Intimal dissection with stenosis
Dobrilovic et al (2001)  40          Intimal dissection with 95%
                                       stenosis
Lee et al (2002)         22          Two areas of intimal injury 0.5 and
                                       0.5 and 3.0 cm from ostium with
                                       preservation of distal perfusion
Hsu et al (2005)          2          Focal intimal flap with occlusion

                         Duration between
                         trauma and stent
Author                   placement         Follow up

Whigham et al (1995)     >24 hours         Not reported
Goodman et al (1998)     >12 hours         DTPA (9 mo): 45% of total
                                             renal function
Villas et al (1999)      Not reported       Not reported  imaging
Dobrilovic et al (2001)  Not reported      Nuclear isotope (16 mo): 40%
                                             of flow distribution. Serum
                                             creatinine unchanged and
                                             normotensive at 18 months
Dobrilovic et al (2001)  Not reported      Nuclear isotope imaging
                                             (9 mo): 43% of flow
                                             distribution. Normal
                                             creatinine and normotensive
                                             at 11 months
Lee et al (2002)         24 hours          Renal scan (f/u time not
                                             specified): 42% of total
                                             renal function
Hsu et al (2005)         12 hours          Laparoscopic nephrectomy 2 mo
                                             after stent placement