[Endovascular aneurysm repair in high-surgical-risk abdominal aortic aneurysm patients: initial and long-term results].

OBJECTIVE: To evaluate the initial and long-term results of endovascular aneurysm repair (EVAR) in high-surgical-risk abdominal aortic aneurysm (AAA) patients. METHODS: From July 1997 to July 2011, 120 consecutive high-surgical-risk patients with AAA who were treated electively using a bifurcated aortic endograft were entered in a registry. There were 96 male and 24 female patients, aged from 52 to 95 years with a mean of 74 years. Follow-up protocol consisted of computed tomography angiograms or ultrasound performed at 3, 6, 9, 12 months, and annually thereafter. The main goal was evaluation of the operative mortality and the long-term survival of these patients. Secondary goals were determination of the frequency of secondary operations, the outcome of the aneurysm sac, and primary and secondary patency rates after aortic endograft placement. RESULTS: Mean aneurysm diameter was (57 ± 8) mm. Thirty-seven patients were operated under local anesthesia and eighty-three under general anesthesia. Five type I endoleaks, twenty-five type II endoleaks and one type III endoleak occurred during the perioperative period. The technical success rate was 95%. Operative mortality was 2.5%. The survival rates at 1-, 3- and 5-year were 92%, 75% and 43% respectively. The mean follow up was (36 ± 3) months. Primary and secondary patency rates at 3 year were respectively 97% and 100%. Secondary intervention rate was 10% (12/120) at 5 year. The reasons included endoleaks for 7 patients, stent-grafts fracture for 2 patients, stent-grafts migration for 2 patients and stent-graft thrombosis for 1 patients. CONCLUSIONS: Initial and long-term results with endograft repair of AAA in high-surgical-risk patients were satisfactory. These results appear to justify endovascular repair for this patient population.

[Surgical treatment of peripheral arterial aneurysms: a report of 35 cases].

OBJECTIVE: To investigate the treatment strategies of peripheral arterial aneurysms. METHODS: Thirty-five cases were reviewed from July 1998 to December 2007, and 28 cases were male, 7 cases were female. Eleven cases were popliteal artery aneurysms, 15 cases were femoral artery aneurysms, 4 cases were extracranial carotid aneurysms and 5 cases were subclavian artery aneurysms. All cases had either open procedures or endovascular procedures. RESULTS: Surgical open procedures were performed on 24 cases, and endovascular procedures were performed on 11 cases. The perioperative complication rate were 16.7% (4/24) and 0% for open and endovascular groups respectively. The average follow-up time was 41 months (7 months to 8 years). The accumulative five year patency were 61% and 48% for surgical grafts and stent grafts respectively. Two cases died of diseases and one had stroke during follow-up. CONCLUSIONS: Surgical open repair is still standard procedure for most peripheral arterial aneurysms and endovascular repair may have its own advantage for high risk patients.

[Diagnosis and surgical therapy of primary retroperitoneal neurogenic tumors].

OBJECTIVE: To explore the diagnosis and surgical therapy for retroperitoneal neurogenic tumors (PRNTs). METHODS: The clinical records of 79 surgically treated patients with retroperitoneal neurogenic tumor were retrospectively analyzed. RESULTS: Twenty-nine patients presented with abdominal pain, 26 with abdominal mass, 15 with inferior extremities pain and numbness and 9 patients without clinical symptoms. Type B ultrasound (BUS), CT scan and surgical resection were performed for all the patients. Pathological analysis identified 19 patients with neurofibroma, 8 with neurilemmoma, 4 with paraganglioma, 21 with neurofibrosarcoma, 14 with malignant neurilemmoma, 6 with malignant paraganglioma, 5 with neuroectodermal tumor and 2 with neuroblastoma. The mortality rate of PRNT operation is was 1.3%, 3-year recurrence rate of benign tumor 0%, 5-year recurrence rate of benign tumor 12.9%, reoperation rate 100%, 5-year survival rate 100%. 3 years recurrence rate of malignancy tumor 41.6%, reoperation rate 90%, 5 years recurrence rate of malignancy tumor 79.1% and 5 years survival rate is 62.5%. CONCLUSION: BUS, CT and MRI are decisive for localization diagnosis. Surgical resection is the mainstay of therapy for this disease. Pre-operative preparation of intestinal tract and blood, maintaining the intactness of involved nerve are important for tumor resection. To prevent tumor recurrence, the key surgical techniques are to minimize tumor residues and . to handle intervertebral foramen properly.

[Diagnosis and treatment of pancreatogenic portal hypertension: analysis of 26 cases].

OBJECTIVE: To investigate the diagnostic and treatment methods of pancreatogenic portal hypertension and to summarize the experience in surgical treatment of these patients, especially in dealing with the complications and sophisticated cases. METHODS: Twenty-six patients with pancreatogenic portal hypertension, 19 males and 7 females, aged 37 (29 - 57), underwent pericardial vessel ligation and splenectomy during the period from January 1990 to November 2006 and were followed up for 8 years (2 - 15 years). The clinical data were analyzed. RESULTS: Seven patients received Roux-en-Y operation for huge pancreatogenic cysts and 3 patients received regional dissection operation of diaphragmatic muscle for severe adhesion. One died of acute myocardial infarction 5 days after the operation, and 25 patients were cured without recurrence during the follow-up. CONCLUSION: Pericardial vessel ligation and splenectomy are rational and reliable methods to treat pancreatogenic portal hypertension. The key issue is how to diagnose pancreatogenic portal hypertension correctly and deal with its complications reasonably.

[Diagnosis and treatment of aneurysm in the common trunk of malformed superior mesenteric artery and celiac trunk].

OBJECTIVE: To explore the diagnosis and treatment of the aneurysm in the common trunk of malformed superior mesenteric artery and celiac trunk, especially the approach how to expose and excise such aneurysm. METHODS: The clinical data of 6 patients with aneurysm in the common trunk of malformed superior mesenteric artery and celiac trunk, who were operated on under general anesthesia from 1998 to 2006, were analyzed. At first, the body of pancreas was isolated and retracted, the malformed celiac trunk and its ramification were blocked and ablated, the initial part of the celiac trunk and the distant end of left gastric artery were ligated, and then by-pass operation was operated from infra-renal aorta to the visceral arteries (hepatic, splenic, and superior mesenteric arteries) with artificial blood vessels. Follow-up was conducted for 1 - 8 years. RESULTS: Five cases underwent aneurysm ablation and by-pass from aorta to hepatic, splenic, and superior mesenteric arteries; while 1 case underwent aneurysm ablation and spleen ablation, superior mesenteric artery reconstruction, and by-pass from aorta to hepatic artery simultaneously. All patients were cured without complication and recurrence. No arterial anastomosis stricture or stenosis was found in the 5 patients who received by-pass from aorta to hepatic, splenic, or superior mesenteric artery; however, slight stricture was found at the repaired portion of superior mesenteric artery in another one patient, but without any arterial anastomosis stricture in aorta or hepatic artery. CONCLUSION: It is an effective and safe method to treat the aneurysm common trunk of malformed superior mesenteric artery and celiac trunk by using the artificial blood vessel by-pass from aorta to visceral arteries (hepatic, splenic, and superior mesenteric arteries) after controlling the initial part of common trunk and cutting off the aneurysm there.

[Mid-long term complications of endovascular repair in aortic diseases and its secondary interventional strategies].

OBJECTIVE: To investigate the methods and effects of secondary intervention for mid-long term complications of endovascular repair (EVR) in aortic diseases. METHODS: From May 1999 to Jun 2007, 21 patients with mid-long term complications after EVR were treated in our center. Of these cases, 15 cases received first EVR for abdominal aortic aneurysm (AAA), 3 cases for thoracic aortic aneurysm (TAA) and 3 cases for aortic dissection (TAD). The mid-long term complications included 11 cases of type I endoleak, 4 cases of type II endoleak, 2 cases of type III endoleak and 4 cases of migration of stent grafts. Proximal or distal extensions were used for type I and III endoleak in 9 cases. Fenestrated, scallop and bifurcated stent grafts were used to reconstruct the aortic arch in 3 cases. Emboli technique was used in treating type II endoleak. Thrombectomy and bypass technique were used in 4 cases with stent graft limb occlusion. One ruptured AAA accepted open surgery. RESULTS: Secondary endovascular technique were undergone in 20 (95.2%) cases. One case died in 30 days after the secondary intervention and endoleak remained after the secondary operation in 5 cases. Three cases died of the secondary intervention. CONCLUSIONS: Endoleak and limb occlusion were the chief mid-long complications after EVR. Secondary endovascular technique can be used in most cases and carries great challenges in aortic arch lesions.

[Treatment of left subclavian artery in endovascular repair of thoracic aortic aneurysm and thoracic aortic dissection].

OBJECTIVE: To investigate the treatments of left subclavian artery (LSA) in endovascular repair (EVR) of thoracic aortic aneurysm (TAA) and thoracic aortic dissection (TAD). METHODS: In 54 TAD or TAA cases, all of the proximal landing zone (PLZ) were less than 15 mm and only the LSA was needed to be treated in EVR, the following methods and techniques were used in the treatments of LSA: complete cover, partial cover, endovascular reconstruction following complete cover, surgical reconstruction before complete cover. RESULTS: DSA was used to evaluate the condition of cerebral circulation in all cases. Forty left subclavian arteries were covered completely. Ten were covered completely after right subclavian artery (RSA)-LSA or left common carotid artery (LCCA)-LSA bypass. PTA and stent in LSA was done in 3 cases. In 1 case, LSA was covered completely first, and then the graft was punctured and bare stent was fixed after inflation by cutting balloon. All of the ancillary techniques were enforced successfully. No severe complications were found in brain and upper extremity. The proximal endoleak rate was 17% (9/54). In the 40 cases whose LSA were not reconstructed, the primary left subclavian steal syndrome (LSSS) happened in 8 cases (20%) and the primary average systolic pressure of left brachial artery was 63 +/- 24 mm Hg. CONCLUSIONS: EVR can be enforced safely and efficiently in TAA and TAD with short PLZ by some ancillary endovascular or surgical techniques. The methods to treat the LSA depend on the condition of the cerebral circulation.

[The feasibility study of endovascular reconstruction of aortic arch with modular branched stent-graft system in canine].

OBJECTIVE: To design and manufacture a modular branched stent-graft system of endovascular reconstruction of the aortic arch in canine, and to investigate the feasibility of endovascular repair. METHODS: After the length and the diameter of ascending aorta, aortic arch and super-arch branched vessel measurement, a modular branched stent-graft system, including two pieces bifurcated stent-graft and one piece straight stent-graft, was designed and manufactured. Under X-ray fluorescope, these three modulars were accessed from right subclavian, left subclavian and femoral artery respectively and connected one by one to reconstruct the aortic arch. The shape and structure of stent-grafts, haemodynamics in aortic arch and endoleak were observed. RESULTS: Eight of ten operations were completed successfully. Two dogs died of obstruction of coronary artery and artery rupture of left subclavian respectively during operation. In the eight successful cases, two proximal type I endoleaks were observed, and no other type endoleak occurred. The shape and the localization of stent-grafts were fine, and the coronary artery and carotid artery were unobstructed. CONCLUSION: It is feasible to reconstruct aortic arch of canine by modular branched stent-graft, and it is significant to direct the research of reconstruction of human aortic arch.

[Surgery for iatrogenic obstruction of the second hepatic portal].

OBJECTIVE: To summarize the effects of surgery for iatrogenic obstruction of the second hepatic portal and the curative effects thereof. METHODS: Seven patients, 5 males and 2 females, aged 25-38, with iatrogenic obstruction of the second hepatic portal, due to blocking of the reflux of hepatic vein by translocated stent in 4 cases and due to occlusion of hepatic vein local thrombosis and endometrial hyperplasia caused by broken wires in 3 cases, underwent removal of the foreign bodies and plastic operation of the second hepatic portal under temporary circulatory pause and hypothermic general anesthesia via the approach of incision of the pericardium and inferior vena cava. The patients were followed up for 6 months to 5 years. RESULTS: After the operation the liver shrank and ascites was decreased significantly in all patients. The liver functions of all patients were normal during the follow-up and no complication or signs of recurrence were found. Ultrasonography and CT scan showed no stricture and stenosis. CONCLUSION: Translocation of stent is the common reason of iatrogenic obstruction of the second hepatic portal. Operational procedure including removal of the foreign bodies and plastic operation of the second hepatic portal under temporary circulatory pause and hypothermic general anesthesia via the approach of incision of the pericardium and inferior vena cava is an effective radical surgical treatment for this complication.

[Apoptosis of pathological tissues and expression of apoptosis-related genes in hepatic venous stricture Budd-Chiari syndrome].

OBJECTIVE: To investigate the pathogenesis of hepatic venous stricture Budd-Chiari syndrome from the point of view of hepatic venous intimal proliferation, apoptosis and apoptosis-related genes. METHODS: Thirty samples resected from patients with hepatic venous stricture Budd-Chiari syndrome and 21 samples of normal hepatic vein and vena cava obtained from necropsy of fresh corps as controls were examined. The paraffin sections of the samples were stained with hematoxyline and eosin and diaminobenzidine respectively and observed under light microscope to examine the pathology and calculate the apoptotic cells. SP immunohistochemistry was used to detect the expression of Bcl-2 and Bax. Proliferating cell nuclear antigen (PCNA) expression was detected by SABC immunohistochemistry. RESULTS: Light microscopy showed irregular proliferation in the tunica intima and tunica media, especially in the former. Incomplete elastic fiber, spotted smooth muscle cells, proliferation of fibrous connective tissue, and degeneration of partial tissues, and infiltration of inflammatory cells, etc. were observed. In the endothelial tissue TUNEL positive cells was 1.94 +/- 0.64 in the Budd-Chiari syndrome patients, significantly higher than that in the controls (0.56 +/- 0.21, P < 0.002); and PCNA positive cells was 3.46 +/- 0.51 in the Budd-Chiari syndrome patients, significantly higher than that in the controls (0.78 +/- 0.16, P < 0.0005). The bcl-2 expression rate was 8.56 +/- 1.17 in the Budd-Chiari syndrome patients, significantly higher than that in the normal controls (4.34 +/- 1.28, P < 0.0005); Bax expression was 3.95 +/- 1.31 in the Budd-Chiari syndrome patients, significantly lower than that in the normal controls (5.06 +/- 1.21, P < 0.001); and the bcl/Bax ratio of the cells in the tunicae intima and media of the normal hepatic veins was 0.914 +/- 0.334, significantly lower than that in the Budd-Chiari syndrome patients (2.402 +/- 1.021, P < 0.01). Electron microscopy showed that in comparison with the normal tissues the pathological tissues had more synthesized smooth muscle cells and lacked normal myoendothelial structure. CONCLUSION: Irregular proliferation of tunica intima of hepatic vein and apoptosis may be one of the mechanisms of hepatic venous stricture Budd-Chiari syndrome.

[The endovascular repair of ruptured aortic aneurysm].

OBJECTIVE: To discuss the safety, feasibility, efficacy and problem of endovascular repair (EVR) for ruptured aortic aneurysm (RAA). METHODS: Fourteen patients with RAA were obtained diagnosis and anatomic data of proximal and distal neck through magnetic resonance imaging and CT. The patients with hypotension were accepted anti-shock treatment. Stent-grafts were deployed in proper position of RAA under X-ray fluoroscopic. RESULTS: The time from rupture to operation was 50 min to 21 d. Three cases had plenty of blood in left pleural cavity and 2 cases were done under bleeding shock condition. Five cases with RAA were fixed by bifurcated stent-grafts and others by straight stent-grafts. Follow-up term was 1 month to 38 months. One with ruptured thoracic aortic aneurysm died 4 h later after operation, another one died of left thoracic cavity infection 9 months later, and others lived well without complication. CONCLUSION: The EVR is a safe, efficient and feasible method. It will be a potential alternative to treat RAA in future, but more suitable for RAA with better proximal and distal landing zones.

[The endovascular repair of aortic dissection: early clinical results of 178 cases].

OBJECTIVE: To discuss the safety, feasibility, efficacy and problems of endovascular repair for aortic dissection. METHODS: From June, 1998 to Dec, 2004, 178 aortic dissections were treated by stent-grafts, including 76 acute cases and 102 chronic cases, 19 cases with Stanford A and 159 cases with Stanford B. Under local or general anesthesia, every stent-graft was deployed at the proper position of first tear entry through femoral artery under X-ray fluoroscopic. The changes of hemodynamic in true and false lumen, visceral and limbs blood supply were investigated after operation. RESULTS: 10 cases combined with left common carotid artery or left subclavian artery or hepatic artery and superior mesenteric artery bypass. 36 left subclavian arteries were covered simultaneously without bypass and the average blood pressure of left brachial artery was (61.6 +/- 23.7) mm Hg. The stent-grafts were deployed above thoracic 8 in 159 cases and below thoracic 8 in 19 cases. This group included 3.4% 30-day death rate, 12.9% endoleak rate after deployment, and without misplace of stent grafts, migration, rupture, conversion to open surgery and paraplegia complication. The average operation time 1.5 h (0.5-4.3 h), blood loss 140 ml (30-500 ml), movement recover time 1.8 d (0.5-21.0 d), food recover time 1.5 d (0.5-9.0 d). The true lumen blood supply in most of damaged visceral arteries were improved. Follow up between 1 month to 76 months, the endoleak rate was 6.4% one month later. CONCLUSION: The endovascular repair is a safe, efficacy and feasible method to aortic dissection. The long term results keep in follow up.

Aneurysm resection and vascular reconstruction for true aneurysm at the initial segment of splenic artery.

The aneurysms at the initial segment of splenic artery are rare. This paper aimed to investigate the methods to treat the true aneurysm at the initial segment of splenic artery by aneurysmectomy plus vascular reconstruction. Retrospectively reviewed were 11 cases of true aneurysm at the initial segment of splenic artery who were treated in our hospital from January 2000 to June 2013. All cases were diagnosed by color ultrasonography, computer tomography (CT) and angiography. Upon resection of the aneurysm, the auto-vein transplantation was performed in situ between the hepatic artery and the distal part of the splenic artery in 1 case; the artificial vessel bypass was done between the infra-renal aorta and distal portion of the splenic artery in 7 cases; the splenectomy was done in 2 cases; the splenectomy in combination with ligation of multiple small aneurysms were performed in 1 case. All cases were cured and discharged from the hospital 10-14 days after operation. A 1-14 year follow-up showed that 9 cases survived, and 2 cases died, including 1 case who died of acute myocardial infarction 2 years after aorta-splenic artery bypass operation and 1 case who died of acute cerebral hemorrhage 5 years after aneurysm resection and the splenectomy. Among 6 cases receiving aorta-splenic artery bypass, 1 gradually developed stenosis at anatomosed site, which eventually progressed to complete occlusion 2 years to 6 years after operation, without suffering from splenic infarction because the spleen was supplied by the short gastric vessel and its collaterals. The other 5 cases receiving aorta-splenic artery bypass and 1 case undergoing autologous vascular transplantation did not develop stricture or pseudoaneurysm at the stoma. Our study showed that the aneurysmectomy plus vascular reconstruction is a better treatment for aneurysm at the initial segment of splenic artery.

[Prevention and management of frequent complications after endovascular repair of infrarenal abdominal aortic aneurysm].

OBJECTIVE: To prevent and manage frequent complications after endovascular repair of infrarenal abdominal aortic aneurysm (AAA). METHODS: The data of 71 cases of infrarenal abdominal aortic aneurysm (AAA) treated by endovascular repair were analysed retrospectively. The reasons, managements, results and prognosis of frequent complications were investigated. RESULTS: Seventy-one cases of infrarenal AAA were treated by endovascular repair with 100% success rate. There was no surgical conversion to open aneurysm repair. There were 8 cases of primary endoleak, 1 case of nervous complication and acute thrombosis. An average follow-up period was 26 +/- 5 months. Three persistent endoleaks and 4 secondary endoleaks were found during the follow-up period. The endoleak rate was 9.8% (7/71) within 1 month postoperatively and mortality rate was 1.3% (1/71). Total mortality rate was 4.2% (3/71). Two patients died from acute myocardial infarction and one from acute heart failure. CONCLUSIONS: Endovascular treatment of abdominal aortic aneurysm is technically feasible and can effectively exclude aortic aneurysms from the circulation. Endoleak is a chief complication after endovascular repair of infrarenal AAA.Additional procedures and follow up are very important. Endoleak with enlarged aneurysm should be treated actively.

[The change of blood supply pattern in visceral arteries of Stanford B dissection after endovascular repair].

OBJECTIVE: To discuss the change of blood supply pattern in visceral arteries of Stanford B dissection. The visceral arteries include celiac trunk (CA), superior mesenteric artery (SMA) and renal artery (RA). METHODS: By retrospectively analysing the clinical data of 52 cases with Stanford B dissection, the blood supply pattern of visceral arteries was confirmed by aortography and the changes before and after endovascular repair were compared. RESULTS: After repair: the stenosis lesions disappeared in 7 cases supported by true channel completely but one. Twenty-two visceral arteries supported by true and false channel simultaneously recovered true channel chiefly but one. One recovered true channel chiefly and one had no change in 2 visceral arteries supported by false channel completely. Four recovered true channel chiefly and one had no change in 5 visceral arteries without blood support. 88.9% blood support got better and 11.1% blood support had no change in 36 damaged visceral arteries after endovascular repair. CONCLUSION: Blood support from true and false channel simultaneously is the chief pattern in the injured visceral arteries before repair; Endovascular repair technique is benefit to recovering the blood support of true channel.

Endovascular repair: alternative treatment of ruptured abdominal aortic aneurysm.

BACKGROUND: As an alternative to open aneurysm repair, endovascular aortic repair (EVAR) has been applied to ruptured abdominal aortic aneurysm (rAAA). The aim of this study was to evaluate the immediate and long-term outcomes of EVAR for rAAA. METHODS: From July 1997 to September 2007, 20 men and six women with rAAA (median age, 68 years) were treated with EVAR. Most patients with suspected rAAA underwent emergency computed tomographic angiography (CTA). The procedure was performed under general or local anesthesia. Endovascular clamping was attempted in hemodynamically unstable patients. Bifurcated endografts and aorto-uni-iliac (AUI) endografts with crossover bypass were used. Patients had CT scan prior to discharge, 3, 6, 12 months after discharge, and annually thereafter. RESULTS: Time between diagnosis and EVAR ranged from 1 hour to 5 days. EVAR was performed under general anesthesia in 21 patients, and under local anesthesia in five patients. Endovascular aortic clamping was performed in four patients. There was no conversion to open surgery during EVAR. Stent-graft insertion was successful in all patients. One patient died during EVAR from acute myocardial infarction. Ten patients had systolic blood pressure < 80 mm Hg. Eleven patients received a blood transfusion. Mean aneurysm size was (47 +/- 12) mm. Mean ICU stay was (8 +/- 3) days, mean hospital stay (18+/- 6) days, and mean procedure time (120 +/- 32) minutes. The 30-day mortality was 23% (6/26 patients), and major morbidity 35% (9/26 patients). Early endoleak occurred in 8/26 patients (31%). The mean follow-up was (18 +/- 7) months. No patient demonstrated migration of the stent-graft. CONCLUSIONS: EVAR is a safe and effective option for treatment of acute rAAA, independent of the patient's general condition. Immediate and mid-term outcomes are favorable, but long-term outcome is unknown. Multi-center studies are necessary to establish the role of EVAR for rAAA.

[Ligation and resection of the inferior vena cava during surgical removal of the retroperitoneal tumors involving the inferior vena cava: feasibility and safety assessment].

OBJECTIVE: To assess the feasibility and safety of excising or patching the inferior vena cava (IVC) without replacement in patients with primary retroperitoneal tumors (PRPT) involving the IVC. METHODS: A retrospective analysis was conducted in 116 consecutive patients with PRPT presented to our Hospital between December 2007 and December 2008. IVC involvement was found in 11.2% of the cases, and in 93 cases receiving surgical tumor removal, the complete resection rate was 93.55%. According to the location of IVC involvement by the PRPT, the cases were classified into 3 groups with IVC involvement in the segment from the second hepatic portal vein to the renal vein (segment A), the segment on the bilateral renal vein plane (segment B), and the segment from the caval bifurcation to the renal vein (segment C). RESULTS: The most common vascular involvement occurred in segment C (61.54%, 8/13), and 2 cases presented with segment A involvement and 2 had segment B involvement. All the 3 segments of IVC were involved in 1 case. Five cases with IVC involvement received IVC patching only, and 4 had resection or ligation of the segment C of the IVC, and resection of the segment A and B of the IVC was performed in 2 and 1 case, respectively. One patient received complete resection of whole IVC involved. All patients recovered smoothly and were discharged. CONCLUSION: The infrarenal IVC can be ligated or resected safely without reconstruction. Combined resection of the bilateral renal vein and segment B of the IVC may result in renal insufficiency. IVC involvement and occlusion between the second hepatic portal and renal veins can be ligated safely without affecting the renal function.