Re: Endovascular Stent Placement for the Treatment of Nutcracker Phenomenon in Three Pediatric Patients

Abstract

Drs. Chen et al respond: In our recent article on nutcracker syndrome (1Chen W Chu J Yang JY et al.Endovascular stent placement for the treatment of nutcracker phenomenon in three pediatric patients.J Vasc Interv Radiol. 2005; 16: 1529-1533Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar), we mentioned that therapy for the condition is still controversial. Asymptomatic hematuria and orthostatic albuminuria can be monitored without treatment or can be treated conservatively with hemostatic agents (eg, carbazochrome). However, for patients with severe hematuria or abdominal pain, hemostatic agents often have little effect (2Soo JK Chang WK Kim S et al.Long-term follow-up after endovascular stent placement for treatment of nutcracker syndrome [letter].J Vasc Interv Radiol. 2005; 16: 428-431Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar, 3Segawa N Asuma H Iwamoto Y et al.Expandable metallic stent placement for nutcracker phenomenon.Urology. 1999; 53: 631-633Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar). We presented three pediatric patients who did not show a response to conservative treatment. Two of them had received oral medication for longer than 18 months, and the other patient had back pain and gross hematuria. In the latter, after conservative treatment, the back pain remained unchanged, and severe gross hematuria required repeated transfusions. Because they were unable to tolerate or chose not to accept currently accepted therapies (ie, oral medication or surgery), they chose what we believe to be an appropriate therapeutic option, interventional therapy. Because there are few reports about endovascular stent placement in pediatric patients with nutcracker syndrome, the most appropriate time for conservative observation is still unknown. We attempted stent placement in these patients and obtained good clinical results. In our three cases, no complications such as stent fracture, migration, or in-stent restenosis occurred. The diameter of the stents we selected was based on vessel size, vessel access, and patient age. Three stents were equal or close to the diameter of the left renal vein of adults. In a normal adult control group, the diameter of the left renal vein was shown to be 6.74 ± 1.39 mm (4Dai B Yang B Fu S et al.Exploring the relationship between left renal vein entrapment syndrome and left varicocele by color Doppler flow imaging.Chin J Ultrasound Med. 2002; 18: 628-629Google Scholar). Another similar article reported that the diameter of the left renal vein was 6.13 mm in the hilar area and 2.35 mm in the narrow portion (5Cho BS Choi YM Kang HH et al.Diagnosis of nutcracker phenomenon using renal Doppler ultrasound in orthostatic proteinuria.Nephrol Dial Transplant. 2001; 16: 1620-1625Crossref PubMed Scopus (37) Google Scholar). Two years after operation, color Doppler sonography showed excellent patency of the venous stents. The diameters of the stents deployed in the three pediatric patients were 8.51 mm, 8.90 mm, and 8.30 mm, respectively. No invasive procedure was performed at the time of our report because of normal findings on urinalysis and good physical development. Another two factors taken into consideration were as follows: (i) because the stent has a mesh structure, the entire stent is endothelialized within 2–3 months after insertion, as confirmed by autopsy studies; and (ii) as the child matures, collateral vessels may be established step by step to meet the increasing flow of the renal vein (3Segawa N Asuma H Iwamoto Y et al.Expandable metallic stent placement for nutcracker phenomenon.Urology. 1999; 53: 631-633Abstract Full Text Full Text PDF PubMed Scopus (49) Google Scholar). As mentioned earlier, we can presume that the diameter of the stent will match continuous vessel growth. Long-term follow-up is still required. We have read the letter by Shin et al and agree with their opinions on the whole. Endovascular stent placement should be carefully considered, especially in children. However, the appropriate time of clinical observation will not be clear until a larger volume of follow-up data becomes available.