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Technical considerations in the surgical management of renovascular hypertension in children
Technical Considerations in the Surgical Management of Renovascular Hypertension in Children By Arnold G. Coran, Walter M. Whitehouse, Jr., and James C. Stanley A n n Arbor, Michigan 9 Fifteen children with severe renovascular hypertension have been treated at the Mott Children's Hospital in the University of Michigan Medical Center b e t w e e n July 1974 and December 1980. The average age was 10.4 yr. Stenoses w e r e of both intimal and medial fibrodysplastic types. Four patients had significant bilateral disease. Three patients had coexistent renal artery aneurysmal disease, and three others had midabdominal aortic coarctations. The most important diagnostic studies included assays of plasma renin activity and selective renal arteriography. Primary operations (11 unilateral, 4 bilateral) included 14 aortorenal by passes (13 vein grafts, 1 hypogastric artery graft), 1 vein patch angioplasty, 1 primary anastomosis, 1 aortic reimplantation, 1 partial nephrectomy (segmentectomy), and 1 arterial dilation. Four secondary operations w e r e performed. Critical factors in pediatric reconstructive renovascular surgery include: (1 | exposure through a generous transverse anterior abdominal incision, (2) systemic anticoagulation with sodium heparin, (3) end-to-end graft-to-renal artery anastomoses, (4) generous spatulation of vessels and grafts at anastomoses, (5) use of microvascular clamps, (6) use of silicon lubricants on dilators, and (7) extreme gentleness in handling all tissues. Eleven children experienced complete remission of hypertension. Four children were improved. Excellent results w e r e attributable to carefully planned and executed reconstructive procedures.
INDEX WORDS: Renovascular hypertension.
ENAL artery occlusive disease is a curable
form of hypertension being recognized R with increasing frequency. Excluding thoracic aortic coarctation, it is the most common type of surgically remedial hypertension in the pediatric age group. Recent improvements in diagnostic From the Section of Pediatric Surgery and Division of Peripheral Vascular Surgery, The University of Michigan Medical School and Mott Children's Hospital, Ann Arbor, Mich. Presented before the Twelfth Annual Meeting of the American Pediatric Surgical Association together with the British Association of Paediatric Surgeons, Tarpon Springs, Florida, April 29-May 2, 1981. Address reprint requests to Arnold G. Coran, M.D., Section of Pediatric Surgery, Mott Children's Hospital, Room F7516, Box 66, Ann Arbor, Mich. 48109. 9 1981 by Grune & Stratton, Inc. 0022-3468/81/1606-0025501.00/0 890
modalities have markedly enhanced the recognition and management of this entity. However, because of its rarity, few surgeons have encountered enough cases to formulate standards for the surgical management of pediatric renovascular hypertension. Recent experience at the University of Michigan with the treatment of this disease, and particular considerations in technical aspects of surgical management provide the basis for this report. MATERIALS AND METHODS Fifteen children with renovascular hypertension have been treated at the Mort Children's Hospital in the University of Michigan Medical Center during the period July 1974 to December 1980 (Table 1). Included were nine boys and six girls with an average age of 10.4 yr, and a range of 3-17 yr. Patients with arterial obstructions due to trauma or extrinsic compression were specifically excluded from this review. Seven children exhibited right sided stenotic disease only, and, in two patients, the left renal artery alone was involved. Six other children had bilateral diseases including four with functionally important contralateral lesions. The main renal artery was the site of involvement in 15 of this series' 19 diseased arteries. Stenotic lesions were located in segmental branches in the remaining four arteries. All lesions were of either focal intimal or medial dysplastic types. Stenoses alternating with mural aneurysms were not encountered in this experience. Diagnosis of hypertension was based on definitions as stated in the recent report of the N I H Task Force on Blood Pressure Control in Children. ~ Mean preoperative blood pressure in this group was 166 _+ 34/112 _+ 18 m m Hg without medication, and 151 _+ 18/101 _+ 13 m m Hg with drug therapy (p < 0.05, all data expressed as E _+ 1 SD). The mean duration of known hypertension in these children was 4.5 _+ 4.5 mo. Although seven children were asymptomatic, eight suffered from various symptoms including headache, fatigability, hyperkinesis, and failure to thrive. Hypertension was unexpectedly diagnosed following routine blood pressure measurements in the asymptomatic children. Extensive diagnostic tests were carried out in all patients. Diagnostic studies. Intravenous pyelography in the form of hypertensive urography was performed in 11 patients to rule out renovascular causes of hypertension. Renal parenchymal disease was not encountered. Urographic evidence indicative of renovascular disease was noted in only 27% of cases studied. Thus, in this series, urography was of little diagnostic or prognostic value. Abnormal elevations in plasma renin activity occurred in all but one of the 11 patients in whom the assay was performed. Renal vein renin ratios ( R V R R ) , comparing
Journal of Pediatric Surgery, Vol. 16, No. 6 (December),1981
SURGERY FOR RENOVASCULAR HYPERTENSION
891
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effluent activity from each kidney was suggestive of functionally important unilateral renovascular disease when greater than 1.4. In the present experience, the mean RVRR among patients benefiting from operation was 2.08 _+ 1.11. Bilateral disease and segmental lesions lessened the sensitivity of renin ratios as a diagnostic study. Determination of individual renal renin secretory activity, expressed as a renal:systemic renin index (RSRI) allowed identification of hyperreninemic patients having functionally important bilateral renal ischemia. RSRI is calculated by subtracting systemic renin activity from renal vein renin activity, and dividing the remainder by the systemic renin activity. An individual kidney's RSRI was normally not greater than 0.24. When the combined activity of both kidneys is related to systemic activity, the RSRI should not be greater than 0.48. RSRI greater than 0.48 from an individual kidney, or both kidneys together, reflects renin production that exceeds hepatic degradation, and thus documents functionally important hyperreninemia. Application of this information of the 11 patients in our series where this data were available, revealed an ischemic kidney RSRI of 1.11 ~ 1.10 and a contralateral kidney RSRI of 0.03 • .23. The latter RSRI reflects suppression of renin secretion. Reliable renin data requires that the patient be prepared by reducing sodium intake, administering a natriuretic drug for three days prior to sampling, and collection blood with patients in the upright position. Aortography with selective renal arteriography using magnification technique was performed in all patients. Arteriograms defined the anatomic location and morphologic character of the stenosis. Arteriography also documented the hemodynamic importance of the renal artery stenosis by demonstrating collateral vessels circumventing the occlusive lesions in 10 cases. Operative therapy. Eleven unilateral and four bilateral primary procedures were performed. Included were 14 aortorenal bypasses (13 autogenous vein grafts, one hypogastric artery graft), one partial nephrectomy, one arterial dilation, one vein patch, one resection with primary anastomosis, and one aortic implantation. Three patients had coexistent aneurysmal disease treated at the time of the revascularization. Three other children had midabdominal aortic coarctations which were managed by a thoracoabdominal bypass graft in one patient and a patch-graft aortoplasty in the other two children. 2 The surgical approach to arterial reconstructive surgery in children has become standardized at our medical center. A generous upper abdominal supraumbilical transverse incision in which both rectus muscles are transected is preferred. The incision is extended from the opposite midclavicular line to the midaxillary line on the side of the renal artery lesion. Extension of this incision into both flanks is used when bilateral repairs are contemplated. Transverse abdominal incisions facilitate the handling of instruments in a direction perpendicular to the longitudinal axis of the body and are of particular benefit in renal artery reconstructive procedures. This small but definite technical advantage, rather than the healing properties of transverse incisions, make this the favored incision over the midline vertical incisions. Once the peritoneal cavity is entered, the intestines are either displaced to the opposite side of the abdomen in the
CORAN, WHITEHOUSE, AND STANLEY
older child or eviscerated in small children. The right renal artery and vein, as well as the inferior vena cava and aorta are exposed by reflecting the colon and duodenum medially. This is accomplished by incising the lateral parieties from the hepatic flexure to the cecum and separating the mesocolon from retroperitoneal structures by both blunt and sharp dissection. Care is required to avoid entering Gerota's fascia anterior to the kidney. It is important that disturbance of perinephritic collateral vessels be minimized during this exposure. As dissection progresses, the duodenum which overlies the upper portion of the right kidney and the proximal pancreas are carefully displaced to the left in an extended Kocher-like manuever. Excellent visualization of the upper abdominal vena cava and vessels to the right kidney is thus provided. Dissection of the renal artery is usually facilitated by retraction of the renal vein superiorly. By blunt and sharp means the renal artery is initially isolated in its midportion just lateral to the vena cava. If one dissects the more proximal artery first, and then commences to expose the more distal vessels, troublesome injury to small arterial and venous branches may be more easily avoided (Fig. 1). Exposure of the left kidney and renal vessels follows a retroperitoneal dissection similar to that performed on the right with reflection of the viscera, including the left colon, medially. The tail and body of the pancreas are easily elevated, without undue tension, over the superior pole of the kidney. Only rarely does a low-lying or large spleen obscure the operative field. It is the authors' contention that his retroperitoneal approach through a transverse incision offers better visualization of the renal vessels than does direct exposure of these structures through an incision in the mesocolon at the root of the mesentery. The proximal and midrenal artery lie beneath the renal vein on the left. Exposure often requires mobilization of the latter vein with ligation and transection of the gonadal branch inferiorly and multiple small adrenal venous branches superiorly. Similar to right-sided exposure, the left renal artery is dissected from the midportion toward the hilum of the kidney. Atte~rltion is then directed to the infrarenal aorta, which is dissected about its circumference for approximately 4-6 cm
Fig. 1. Extraperitoneal exposure of right renal vasculature. (See text for details.)
SURGERY FOR RENOVASCULAR HYPERTENSION
893
adjacent to, or below the inferior mesenteric artery. Subsequently a segment of saphenous vein or an internal lilac artery is procured for use in the reconstruction. Vein grafts are carefully procured, gently handled and irrigated with cold heparinized blood prior to implantation. They are not distended with irrigation solutions. Disturbance of adventitial tissue is minimized. Ligation of venous branches is always a few millimeters away from the parent vein such that the latter is not constricted by a "purse-string" effect of adventitial gathering. Removal of a hypogastric artery for use as an interposition graft proceeds in a similar fashion, using care not to cause excessive trauma to the vessel. Prosthetic grafts are not recommended for renal artery reconstructive procedures in the pediatric patient. Once exposure of the renal artery and aorta has been achieved and a graft has been obtained, systemic anticoagulation is instituted. This is accomplished by the intravenous administration of sodium heparin, 150 U/kg. Regional heparinization is not considered effective. A side-biting vascular clamp is placed on the aorta adjacent to, or just below the inferior mesenteric artery. In smaller children this may necessitate total aortic occlusion. A lateral aortotomy is created, such that its length is approximately two to three times the diameter of the vein or artery graft. The graft is spatulated and the aortic anastomosis is performed using a continuous suture, usually of 5-0 or 6-0 polypropylene. The initial stitch is placed through the apex of the spatulated graft and the superior aspect of the aortotomy (Fig. 2). Once this anastomosis has been completed, attention is directed to performance of the distal anastomosis. The most direct route for aortorenal grafts to the right kidney is in the retrocaval
position. In general, this lessens the likelihood of distal anastomotic kinking, sometimes seen when grafts are carried anterior to the inferior vena cava and down to the renal pelvis. However, the choice of antecaval or retrocaval positioning of the graft must be individualized. Grafts to the left kidney lie behind the inferior mesenteric vessels of the mesocolon, and usually are passed beneath the left renal vein. The aortic clamp remains in place during the completion of the distal anastomosis. To remove this clamp and to place another occluding device on the graft may cause significant injury to the latter conduit. The proximal renal artery as well as vessels beyond the stenosis are occluded, and the artery is transected (Fig. 3). The proximal artery is ligated. Microvascular clamps (Heifitz clips), developing tensions ranging from 30-70 g are preferred over conventional vascular clamps for occluding distal renal vessels. They have less potential to cause vessel wall injury, and, because of their small size, obscuration of the operative field is less likely. Application of these devices should be such that the blades, rather than the handles, are positioned anteriorly. This reduces nuisance entanglements of suture material in the clamp handles as the reconstruction progresses. A graft-to-renal artery anastomosis is then performed in an end-to-end fashion (Fig. 4). This anastomosis is facilitated by spatulation of the renal artery on its anterior aspect and the graft on its postrior aspect. The renal artery spatulation allows visualization of the vessel's interior, such that inclusion of intima with each stitch is easily accomplished. Initial suture placements, usually with 6-0 polyester or 6-0 prolene are through the apex of the spatulated vessel to the margin of the opposite vessel. These are tied, and, with traction, used as stay-sutures. The anastomosis is completed using three or four sutures, so as to interrUpt the anastomosis and allow for later growth. In the case of vessels smaller than 2 mm in diameter, the anastomosis may be best completed by using individual interrupted sutures about the entire circumference. Spatulated anastomoses are somewhat ovoid and
Fig. 2. The graft-to-aortic, (See t e x t for details.)
Fig. 3. Transection of diseased renal artery. (See t e x t for details.)
end-to-side anastomosis.
894
CORAN, WHITEHOUSE, AND STANLEY
A Fig. 5. Completed renal artery reconstruction. (See t e x t for details.)
One of our three children with abdominal aortic coarctation underwent a thoracoabdominal bypass with a synthetic graft, from which a saphenous vein bypass graft was taken to reconstruct the stenotic renal artery. The other two children with abdominal aortic coarctation underwent synthetic patch-graft aortoplasties. In one of these patients, bilateral simultaneous aortorenal vein grafts were placed, and, in the
B Fig. 4. The graft-to-renal artery, end-to-end anastomosis. (See t e x t for details.)
have increased suture line circumferences. With healing, they are less likely to produce late strictures, a situation more likely to occur with nonspatulated end-to-end anastomoses. Following completion of the anastomosis, the aortic and renal artery clamps are removed and antegrade renal blood flow reestablished (Fig. 5). The heparin effect is reversed with slow intravenous administration of 1.2 mg pi'otamine sulfate for each 100 U of previously given heparin. The intestines are returned to their normal position and the abdomen is closed in a standard manner. If arterial dilatation is being carried out, alone or in conjunction with a bypass procedure, the renal artery is exposed in the aforementioned manner and anticoagulation is achieved prior to clamping the vessel. Rigid dilators are passed through a transverse arteriotomy in the main renal artery (Fig. 6). They are thoroughly lubricated with a sterile silicone solution so as to lessen traumatic intimal injury. The stenotic area is progressively dilated by careful advancement of increasingly larger dilators in increments of 0.5 ram. Dilators 1.0 mm greater than the diameter of the normal proximal artery should not be used, as they may be injurious to the vessel.
Fig, 6. Rigid arterial dilators are used to dilate segmental branch stenoses. (See t e x t for details.)
SURGERY FOR RENOVASCULAR HYPERTENSION
895
Fig. 7. (A) Preoperative renal arteriogram with magnification showing right renal artery stenosis and aneurysm. (B) Postoperative aortogram showing the patent reversed saphenous vein aortorenal graft. Note the presence of an undiseasad accessory renal artery.
other, a left aortorenal vein graft and a right renal artery aortic implantation were used to revascularize the ischemic kidneys. Late nephrectomy was required twice because of distal strictures resulting in recurrent hypertension. In addition, two other patients required secondary surgical procedures.
RESULTS
Patient follow-up, ranging from 6-47 too, averaged 26 mo. Effectiveness of the operation was based on blood pressure determination at the time of the patient's most recent examination. Patients were classified as cured if, for the preceding 6 mo during which time no antihypertensive medications were administered, their blood pressures were below the 95th percentile for their age and sex. 1 Patients were considered improved if they were within normotensive ranges, but on drug therapy, or if their diastolic pressures were greater than normal, but were at least 15% lower than preoperative levels. Failures, although not occurring in our series, would have been those patients whose diastolic pressures were greater than established normal levels and not 15% lower than preoperative values.
Eleven children were cured with complete amelioration of their hypertensive state and four children were considered improved. The mean postoperative blood pressure for this group was 116 _+ 13/73 _+ 8 m m Hg, which was considerably less than their mean preoperative blood pressure (p < 0.001). Of the four improved patients, one had preoperative intraparenchymal occlusions of multiple vessels, one had an inoperable total segmental artery occlusion in addition to his main renal artery stenosis, one incurred a distal branch occlusion during the revascularization procedure, and the fourth child underwent an unsuccessful attempt at arterial dilatation of a second order intraparenchymal segmental artery. All patients underwent arteriography during the immediate postoperative period prior to discharge (Fig. 7). In all cases, the reconstructions were demonstrated to be patent initially. In addition, late arteriographie follow-up has been obtained in all but the most recently treated patient. One child who underwent resection of the renal artery stenosis with a primary anasto-
CORAN, WHITEHOUSE, AND STANLEY
896
mosis developed an anastomotic stricture postoperatively and nephrectomy was required 3 mo later. Another child, who underwent a resection of a right renal artery aneurysm and repair of the renal artery stenosis with a vein patch, also developed an anastomotic stricture and persistent hypertension postoperatively, resulting in nephrectomy 21 mo later. Four autogenous saphenous vein grafts developed significant postoperative dilatation, without recurrent hypertension. In one of these patients, two vein grafts were subsequently plicated. Peripheral embolization occurred from an aneurysmal vein graft in another patient and eventuated in a later nephrectomy. COMMENTS
The apparent increase in the incidence of renal artery stenosis in children is certainly due to a greater awareness of this curable form of secondary hypertension. The grave consequences
of uncontrolled high blood pressure during infancy and childhood have highlighted this awareness. 3,4 The long-term use of medication to treat hypertension in the young patient is unacceptable if a cure can be provided by surgical intervention. The past decade has witnessed marked improvements in vascular surgical techniques. The incidence of primary nephrectomy in the management of pediatric renovascular hypertension has been markedly reduced] Although the world-wide experience with renovascular hypertension is limited, our series and those of three other institutions who have treated more than 15 children with renal artery stenoses support the concept that renal revascularization is the preferred method of managing this entity. 6-16 Careful attention to technical details in renal artery reconstructive surgery is essential if optimal results are to be afforded the pediatric patient with renovascular hypertension.
REFERENCES 1. National Heart, Lung and Blood lnstitute's Task Force on Blood Pressure Control in Children: Report of the task force on blood pressure control in children. Pediatrics Part 2 59:797-820, 1977 2. Graham LM, Zelenock GB, Erlandson EE, et al: Abdominal aortic coarctation and segmental hypoplasia. Surgery 85:519 529, 1979 3. Foster JH, Pettinger WA, Oates JA, et al: Malignant hypertension secondary to renal artery stenosis in children. Ann Surg 164:700-713, 1966 4. Plumer LB, Mendoza SA, Kaplan GW: Hypertension in infancy: The case for aggressive management. J Urol 113:555-557, 1975 5. Coran AG, Schuster SR: Renovascular hypertension in childhood. Surgery 64:672-677, 1968 6. Fry W J, Ernst CB, Stanley JC, et al: Renovascular hypertension in the pediatric patient. Arch Surg 107:692 698, 1973 7. Lawson JD, Boerth R, Foster JH, et al: Diagnosis and management of renovascular hypertension in children. Arch Surg 113:1307-1316, 1977 8. Stanley JC, Fry W J: Surgical treatment of renovascular hypertension. Arch Surg 112:1291-1297, 1977 9. Stanley P, Gyepes MT, Olson DL, et al: Renovascular
hypertension in children and adolescents. Radiology 129:123-131, 1978 10. Stoney R J, Cooke PA, String ST: Surgical treatment of renovascular hypertension in children. J Pediatr Surg 10:631-639, 1975 11. Benjamin SP, Dustan HP, Gifford RW Jr, et al: Stenosing renal artery disease in children. Clinicopathologic correlation in 20 surgically treated cases. Cleve Clin Q 43:197-206, 1976 12. Kaufman J J, Goodwin WE, Waisman J, et al: Renovascular hypertension in children. Report of seven cases treated surgically including two cases of renal autotransolanration. Am J Surg 124:I49 157, 1972 I3. Kyriakides GK, Najarian JS: Renovascular hypertension in childhood: Successful treatment by renal autotransplantation. Surgery 85:611-616, 1979 14. Novick AC, Straffon RA, Steward BH, et al: Surgical treatment of renovascular hypertension in the pediatric patient. J Urol 119:794-805, 1978 15. Vermuelen F, Stas F, Delegher C, et al: Surgical correction of renovascular hypertension in children. J Cardiovasc Surg 16:21-34, 1975 16. Stanley JC, Fry W J: Pediatric renal artery occlusive disease and renovascular hypertension: Etiology, diagnosis and operative treatment. Arch Surg (in Press)
Discussion James O'Neill (Nashville): I would urge individualization with the problem. We approach things slightly differently. We use a midline incision, and have varied the types of graft
material used including Dacron, which has worked well. We use systemic heparin but do not use protamine. In our series reported by Dean of over 100 children evaluated for hypertension,
SURGERY FOR RENOVASCULAR HYPERTENSION
25% of them had it on a renal basis, a higher incidence than adults. In a group of 18 revascularization procedures done a variety of ways, we had two early thromboses. This was primarily the patch angioplasty group. Of further interest is that on long term followup up to 10 yr, many patients have recurrence of hypertension, primarily because they have fibromuscular hyperplasia. Hence we biopsy the aortotomy site as a predictor. Long term followup shows 91% of patients cured or improved much like Dr. Coran's results, but nine or 10% are unchanged and require long term medication. It is our feeling that neonates or very young infants with renovascular hypertension are best controlled with medication until they are 3 or 4 yr of age. Have you operated on any younger than that? Arnold G. Coran (Closure): All the patients in this series that were diagnosed as having renal artery stenosis were operated upon. I think that hypertension due to renal artery stenosis is a surgical disease in the child. The question of the vein graft versus the hypogastric artery is a very important one. We are concerned about the fact that the vasa vasorum of the saphenous vein in small children are quite short, and we think this is the etiology of the saphenous vein dilation. This may not happen with the hypogastric artery. One must be prepared to use either the
897
saphenous vein or the hypogastric artery. The children that did develop venous graft dilation did not have recurrent hypertension. In one child, two of the veins became so dilated, we decided to plicate them. The child did not undergo any change in his blood pressure, that is, it was normal before and after the plication. The question of segmental artery bypass with a graft is a good one. In actuality, although I did not show the details of it, that patient whose arteriogram you saw had an aneurysm right at the trifurcation of the upper renal artery. In order to reconstruct that patient we had to sew the trifurcation to itself, that is, create one opening from three little vessels and then anastomose the saphenous vein to it. So if it is a proximal segmental artery stenosis we still recommend doing a bypass to it. If it is intraparenchymal, then we obviously can not do that and we prefer dilation. In response to Dr. O'Neill's questions, the transverse incision is used because it is easier to get deep into the wound and to turn your needle at right angles to your anastomosis. Heparinization systemically is very important. There are tiny little vessels and they will clot if the blood is not systemically heparinized. The question of the aortotomy: we biopsy all the tissue at the time of repair, both the renal artery and the aorta.
INDEX WORDS: Renovascular hypertension.
ENAL artery occlusive disease is a curable
form of hypertension being recognized R with increasing frequency. Excluding thoracic aortic coarctation, it is the most common type of surgically remedial hypertension in the pediatric age group. Recent improvements in diagnostic From the Section of Pediatric Surgery and Division of Peripheral Vascular Surgery, The University of Michigan Medical School and Mott Children's Hospital, Ann Arbor, Mich. Presented before the Twelfth Annual Meeting of the American Pediatric Surgical Association together with the British Association of Paediatric Surgeons, Tarpon Springs, Florida, April 29-May 2, 1981. Address reprint requests to Arnold G. Coran, M.D., Section of Pediatric Surgery, Mott Children's Hospital, Room F7516, Box 66, Ann Arbor, Mich. 48109. 9 1981 by Grune & Stratton, Inc. 0022-3468/81/1606-0025501.00/0 890
modalities have markedly enhanced the recognition and management of this entity. However, because of its rarity, few surgeons have encountered enough cases to formulate standards for the surgical management of pediatric renovascular hypertension. Recent experience at the University of Michigan with the treatment of this disease, and particular considerations in technical aspects of surgical management provide the basis for this report. MATERIALS AND METHODS Fifteen children with renovascular hypertension have been treated at the Mort Children's Hospital in the University of Michigan Medical Center during the period July 1974 to December 1980 (Table 1). Included were nine boys and six girls with an average age of 10.4 yr, and a range of 3-17 yr. Patients with arterial obstructions due to trauma or extrinsic compression were specifically excluded from this review. Seven children exhibited right sided stenotic disease only, and, in two patients, the left renal artery alone was involved. Six other children had bilateral diseases including four with functionally important contralateral lesions. The main renal artery was the site of involvement in 15 of this series' 19 diseased arteries. Stenotic lesions were located in segmental branches in the remaining four arteries. All lesions were of either focal intimal or medial dysplastic types. Stenoses alternating with mural aneurysms were not encountered in this experience. Diagnosis of hypertension was based on definitions as stated in the recent report of the N I H Task Force on Blood Pressure Control in Children. ~ Mean preoperative blood pressure in this group was 166 _+ 34/112 _+ 18 m m Hg without medication, and 151 _+ 18/101 _+ 13 m m Hg with drug therapy (p < 0.05, all data expressed as E _+ 1 SD). The mean duration of known hypertension in these children was 4.5 _+ 4.5 mo. Although seven children were asymptomatic, eight suffered from various symptoms including headache, fatigability, hyperkinesis, and failure to thrive. Hypertension was unexpectedly diagnosed following routine blood pressure measurements in the asymptomatic children. Extensive diagnostic tests were carried out in all patients. Diagnostic studies. Intravenous pyelography in the form of hypertensive urography was performed in 11 patients to rule out renovascular causes of hypertension. Renal parenchymal disease was not encountered. Urographic evidence indicative of renovascular disease was noted in only 27% of cases studied. Thus, in this series, urography was of little diagnostic or prognostic value. Abnormal elevations in plasma renin activity occurred in all but one of the 11 patients in whom the assay was performed. Renal vein renin ratios ( R V R R ) , comparing
Journal of Pediatric Surgery, Vol. 16, No. 6 (December),1981
SURGERY FOR RENOVASCULAR HYPERTENSION
891
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effluent activity from each kidney was suggestive of functionally important unilateral renovascular disease when greater than 1.4. In the present experience, the mean RVRR among patients benefiting from operation was 2.08 _+ 1.11. Bilateral disease and segmental lesions lessened the sensitivity of renin ratios as a diagnostic study. Determination of individual renal renin secretory activity, expressed as a renal:systemic renin index (RSRI) allowed identification of hyperreninemic patients having functionally important bilateral renal ischemia. RSRI is calculated by subtracting systemic renin activity from renal vein renin activity, and dividing the remainder by the systemic renin activity. An individual kidney's RSRI was normally not greater than 0.24. When the combined activity of both kidneys is related to systemic activity, the RSRI should not be greater than 0.48. RSRI greater than 0.48 from an individual kidney, or both kidneys together, reflects renin production that exceeds hepatic degradation, and thus documents functionally important hyperreninemia. Application of this information of the 11 patients in our series where this data were available, revealed an ischemic kidney RSRI of 1.11 ~ 1.10 and a contralateral kidney RSRI of 0.03 • .23. The latter RSRI reflects suppression of renin secretion. Reliable renin data requires that the patient be prepared by reducing sodium intake, administering a natriuretic drug for three days prior to sampling, and collection blood with patients in the upright position. Aortography with selective renal arteriography using magnification technique was performed in all patients. Arteriograms defined the anatomic location and morphologic character of the stenosis. Arteriography also documented the hemodynamic importance of the renal artery stenosis by demonstrating collateral vessels circumventing the occlusive lesions in 10 cases. Operative therapy. Eleven unilateral and four bilateral primary procedures were performed. Included were 14 aortorenal bypasses (13 autogenous vein grafts, one hypogastric artery graft), one partial nephrectomy, one arterial dilation, one vein patch, one resection with primary anastomosis, and one aortic implantation. Three patients had coexistent aneurysmal disease treated at the time of the revascularization. Three other children had midabdominal aortic coarctations which were managed by a thoracoabdominal bypass graft in one patient and a patch-graft aortoplasty in the other two children. 2 The surgical approach to arterial reconstructive surgery in children has become standardized at our medical center. A generous upper abdominal supraumbilical transverse incision in which both rectus muscles are transected is preferred. The incision is extended from the opposite midclavicular line to the midaxillary line on the side of the renal artery lesion. Extension of this incision into both flanks is used when bilateral repairs are contemplated. Transverse abdominal incisions facilitate the handling of instruments in a direction perpendicular to the longitudinal axis of the body and are of particular benefit in renal artery reconstructive procedures. This small but definite technical advantage, rather than the healing properties of transverse incisions, make this the favored incision over the midline vertical incisions. Once the peritoneal cavity is entered, the intestines are either displaced to the opposite side of the abdomen in the
CORAN, WHITEHOUSE, AND STANLEY
older child or eviscerated in small children. The right renal artery and vein, as well as the inferior vena cava and aorta are exposed by reflecting the colon and duodenum medially. This is accomplished by incising the lateral parieties from the hepatic flexure to the cecum and separating the mesocolon from retroperitoneal structures by both blunt and sharp dissection. Care is required to avoid entering Gerota's fascia anterior to the kidney. It is important that disturbance of perinephritic collateral vessels be minimized during this exposure. As dissection progresses, the duodenum which overlies the upper portion of the right kidney and the proximal pancreas are carefully displaced to the left in an extended Kocher-like manuever. Excellent visualization of the upper abdominal vena cava and vessels to the right kidney is thus provided. Dissection of the renal artery is usually facilitated by retraction of the renal vein superiorly. By blunt and sharp means the renal artery is initially isolated in its midportion just lateral to the vena cava. If one dissects the more proximal artery first, and then commences to expose the more distal vessels, troublesome injury to small arterial and venous branches may be more easily avoided (Fig. 1). Exposure of the left kidney and renal vessels follows a retroperitoneal dissection similar to that performed on the right with reflection of the viscera, including the left colon, medially. The tail and body of the pancreas are easily elevated, without undue tension, over the superior pole of the kidney. Only rarely does a low-lying or large spleen obscure the operative field. It is the authors' contention that his retroperitoneal approach through a transverse incision offers better visualization of the renal vessels than does direct exposure of these structures through an incision in the mesocolon at the root of the mesentery. The proximal and midrenal artery lie beneath the renal vein on the left. Exposure often requires mobilization of the latter vein with ligation and transection of the gonadal branch inferiorly and multiple small adrenal venous branches superiorly. Similar to right-sided exposure, the left renal artery is dissected from the midportion toward the hilum of the kidney. Atte~rltion is then directed to the infrarenal aorta, which is dissected about its circumference for approximately 4-6 cm
Fig. 1. Extraperitoneal exposure of right renal vasculature. (See text for details.)
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adjacent to, or below the inferior mesenteric artery. Subsequently a segment of saphenous vein or an internal lilac artery is procured for use in the reconstruction. Vein grafts are carefully procured, gently handled and irrigated with cold heparinized blood prior to implantation. They are not distended with irrigation solutions. Disturbance of adventitial tissue is minimized. Ligation of venous branches is always a few millimeters away from the parent vein such that the latter is not constricted by a "purse-string" effect of adventitial gathering. Removal of a hypogastric artery for use as an interposition graft proceeds in a similar fashion, using care not to cause excessive trauma to the vessel. Prosthetic grafts are not recommended for renal artery reconstructive procedures in the pediatric patient. Once exposure of the renal artery and aorta has been achieved and a graft has been obtained, systemic anticoagulation is instituted. This is accomplished by the intravenous administration of sodium heparin, 150 U/kg. Regional heparinization is not considered effective. A side-biting vascular clamp is placed on the aorta adjacent to, or just below the inferior mesenteric artery. In smaller children this may necessitate total aortic occlusion. A lateral aortotomy is created, such that its length is approximately two to three times the diameter of the vein or artery graft. The graft is spatulated and the aortic anastomosis is performed using a continuous suture, usually of 5-0 or 6-0 polypropylene. The initial stitch is placed through the apex of the spatulated graft and the superior aspect of the aortotomy (Fig. 2). Once this anastomosis has been completed, attention is directed to performance of the distal anastomosis. The most direct route for aortorenal grafts to the right kidney is in the retrocaval
position. In general, this lessens the likelihood of distal anastomotic kinking, sometimes seen when grafts are carried anterior to the inferior vena cava and down to the renal pelvis. However, the choice of antecaval or retrocaval positioning of the graft must be individualized. Grafts to the left kidney lie behind the inferior mesenteric vessels of the mesocolon, and usually are passed beneath the left renal vein. The aortic clamp remains in place during the completion of the distal anastomosis. To remove this clamp and to place another occluding device on the graft may cause significant injury to the latter conduit. The proximal renal artery as well as vessels beyond the stenosis are occluded, and the artery is transected (Fig. 3). The proximal artery is ligated. Microvascular clamps (Heifitz clips), developing tensions ranging from 30-70 g are preferred over conventional vascular clamps for occluding distal renal vessels. They have less potential to cause vessel wall injury, and, because of their small size, obscuration of the operative field is less likely. Application of these devices should be such that the blades, rather than the handles, are positioned anteriorly. This reduces nuisance entanglements of suture material in the clamp handles as the reconstruction progresses. A graft-to-renal artery anastomosis is then performed in an end-to-end fashion (Fig. 4). This anastomosis is facilitated by spatulation of the renal artery on its anterior aspect and the graft on its postrior aspect. The renal artery spatulation allows visualization of the vessel's interior, such that inclusion of intima with each stitch is easily accomplished. Initial suture placements, usually with 6-0 polyester or 6-0 prolene are through the apex of the spatulated vessel to the margin of the opposite vessel. These are tied, and, with traction, used as stay-sutures. The anastomosis is completed using three or four sutures, so as to interrUpt the anastomosis and allow for later growth. In the case of vessels smaller than 2 mm in diameter, the anastomosis may be best completed by using individual interrupted sutures about the entire circumference. Spatulated anastomoses are somewhat ovoid and
Fig. 2. The graft-to-aortic, (See t e x t for details.)
Fig. 3. Transection of diseased renal artery. (See t e x t for details.)
end-to-side anastomosis.
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CORAN, WHITEHOUSE, AND STANLEY
A Fig. 5. Completed renal artery reconstruction. (See t e x t for details.)
One of our three children with abdominal aortic coarctation underwent a thoracoabdominal bypass with a synthetic graft, from which a saphenous vein bypass graft was taken to reconstruct the stenotic renal artery. The other two children with abdominal aortic coarctation underwent synthetic patch-graft aortoplasties. In one of these patients, bilateral simultaneous aortorenal vein grafts were placed, and, in the
B Fig. 4. The graft-to-renal artery, end-to-end anastomosis. (See t e x t for details.)
have increased suture line circumferences. With healing, they are less likely to produce late strictures, a situation more likely to occur with nonspatulated end-to-end anastomoses. Following completion of the anastomosis, the aortic and renal artery clamps are removed and antegrade renal blood flow reestablished (Fig. 5). The heparin effect is reversed with slow intravenous administration of 1.2 mg pi'otamine sulfate for each 100 U of previously given heparin. The intestines are returned to their normal position and the abdomen is closed in a standard manner. If arterial dilatation is being carried out, alone or in conjunction with a bypass procedure, the renal artery is exposed in the aforementioned manner and anticoagulation is achieved prior to clamping the vessel. Rigid dilators are passed through a transverse arteriotomy in the main renal artery (Fig. 6). They are thoroughly lubricated with a sterile silicone solution so as to lessen traumatic intimal injury. The stenotic area is progressively dilated by careful advancement of increasingly larger dilators in increments of 0.5 ram. Dilators 1.0 mm greater than the diameter of the normal proximal artery should not be used, as they may be injurious to the vessel.
Fig, 6. Rigid arterial dilators are used to dilate segmental branch stenoses. (See t e x t for details.)
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Fig. 7. (A) Preoperative renal arteriogram with magnification showing right renal artery stenosis and aneurysm. (B) Postoperative aortogram showing the patent reversed saphenous vein aortorenal graft. Note the presence of an undiseasad accessory renal artery.
other, a left aortorenal vein graft and a right renal artery aortic implantation were used to revascularize the ischemic kidneys. Late nephrectomy was required twice because of distal strictures resulting in recurrent hypertension. In addition, two other patients required secondary surgical procedures.
RESULTS
Patient follow-up, ranging from 6-47 too, averaged 26 mo. Effectiveness of the operation was based on blood pressure determination at the time of the patient's most recent examination. Patients were classified as cured if, for the preceding 6 mo during which time no antihypertensive medications were administered, their blood pressures were below the 95th percentile for their age and sex. 1 Patients were considered improved if they were within normotensive ranges, but on drug therapy, or if their diastolic pressures were greater than normal, but were at least 15% lower than preoperative levels. Failures, although not occurring in our series, would have been those patients whose diastolic pressures were greater than established normal levels and not 15% lower than preoperative values.
Eleven children were cured with complete amelioration of their hypertensive state and four children were considered improved. The mean postoperative blood pressure for this group was 116 _+ 13/73 _+ 8 m m Hg, which was considerably less than their mean preoperative blood pressure (p < 0.001). Of the four improved patients, one had preoperative intraparenchymal occlusions of multiple vessels, one had an inoperable total segmental artery occlusion in addition to his main renal artery stenosis, one incurred a distal branch occlusion during the revascularization procedure, and the fourth child underwent an unsuccessful attempt at arterial dilatation of a second order intraparenchymal segmental artery. All patients underwent arteriography during the immediate postoperative period prior to discharge (Fig. 7). In all cases, the reconstructions were demonstrated to be patent initially. In addition, late arteriographie follow-up has been obtained in all but the most recently treated patient. One child who underwent resection of the renal artery stenosis with a primary anasto-
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mosis developed an anastomotic stricture postoperatively and nephrectomy was required 3 mo later. Another child, who underwent a resection of a right renal artery aneurysm and repair of the renal artery stenosis with a vein patch, also developed an anastomotic stricture and persistent hypertension postoperatively, resulting in nephrectomy 21 mo later. Four autogenous saphenous vein grafts developed significant postoperative dilatation, without recurrent hypertension. In one of these patients, two vein grafts were subsequently plicated. Peripheral embolization occurred from an aneurysmal vein graft in another patient and eventuated in a later nephrectomy. COMMENTS
The apparent increase in the incidence of renal artery stenosis in children is certainly due to a greater awareness of this curable form of secondary hypertension. The grave consequences
of uncontrolled high blood pressure during infancy and childhood have highlighted this awareness. 3,4 The long-term use of medication to treat hypertension in the young patient is unacceptable if a cure can be provided by surgical intervention. The past decade has witnessed marked improvements in vascular surgical techniques. The incidence of primary nephrectomy in the management of pediatric renovascular hypertension has been markedly reduced] Although the world-wide experience with renovascular hypertension is limited, our series and those of three other institutions who have treated more than 15 children with renal artery stenoses support the concept that renal revascularization is the preferred method of managing this entity. 6-16 Careful attention to technical details in renal artery reconstructive surgery is essential if optimal results are to be afforded the pediatric patient with renovascular hypertension.
REFERENCES 1. National Heart, Lung and Blood lnstitute's Task Force on Blood Pressure Control in Children: Report of the task force on blood pressure control in children. Pediatrics Part 2 59:797-820, 1977 2. Graham LM, Zelenock GB, Erlandson EE, et al: Abdominal aortic coarctation and segmental hypoplasia. Surgery 85:519 529, 1979 3. Foster JH, Pettinger WA, Oates JA, et al: Malignant hypertension secondary to renal artery stenosis in children. Ann Surg 164:700-713, 1966 4. Plumer LB, Mendoza SA, Kaplan GW: Hypertension in infancy: The case for aggressive management. J Urol 113:555-557, 1975 5. Coran AG, Schuster SR: Renovascular hypertension in childhood. Surgery 64:672-677, 1968 6. Fry W J, Ernst CB, Stanley JC, et al: Renovascular hypertension in the pediatric patient. Arch Surg 107:692 698, 1973 7. Lawson JD, Boerth R, Foster JH, et al: Diagnosis and management of renovascular hypertension in children. Arch Surg 113:1307-1316, 1977 8. Stanley JC, Fry W J: Surgical treatment of renovascular hypertension. Arch Surg 112:1291-1297, 1977 9. Stanley P, Gyepes MT, Olson DL, et al: Renovascular
hypertension in children and adolescents. Radiology 129:123-131, 1978 10. Stoney R J, Cooke PA, String ST: Surgical treatment of renovascular hypertension in children. J Pediatr Surg 10:631-639, 1975 11. Benjamin SP, Dustan HP, Gifford RW Jr, et al: Stenosing renal artery disease in children. Clinicopathologic correlation in 20 surgically treated cases. Cleve Clin Q 43:197-206, 1976 12. Kaufman J J, Goodwin WE, Waisman J, et al: Renovascular hypertension in children. Report of seven cases treated surgically including two cases of renal autotransolanration. Am J Surg 124:I49 157, 1972 I3. Kyriakides GK, Najarian JS: Renovascular hypertension in childhood: Successful treatment by renal autotransplantation. Surgery 85:611-616, 1979 14. Novick AC, Straffon RA, Steward BH, et al: Surgical treatment of renovascular hypertension in the pediatric patient. J Urol 119:794-805, 1978 15. Vermuelen F, Stas F, Delegher C, et al: Surgical correction of renovascular hypertension in children. J Cardiovasc Surg 16:21-34, 1975 16. Stanley JC, Fry W J: Pediatric renal artery occlusive disease and renovascular hypertension: Etiology, diagnosis and operative treatment. Arch Surg (in Press)
Discussion James O'Neill (Nashville): I would urge individualization with the problem. We approach things slightly differently. We use a midline incision, and have varied the types of graft
material used including Dacron, which has worked well. We use systemic heparin but do not use protamine. In our series reported by Dean of over 100 children evaluated for hypertension,
SURGERY FOR RENOVASCULAR HYPERTENSION
25% of them had it on a renal basis, a higher incidence than adults. In a group of 18 revascularization procedures done a variety of ways, we had two early thromboses. This was primarily the patch angioplasty group. Of further interest is that on long term followup up to 10 yr, many patients have recurrence of hypertension, primarily because they have fibromuscular hyperplasia. Hence we biopsy the aortotomy site as a predictor. Long term followup shows 91% of patients cured or improved much like Dr. Coran's results, but nine or 10% are unchanged and require long term medication. It is our feeling that neonates or very young infants with renovascular hypertension are best controlled with medication until they are 3 or 4 yr of age. Have you operated on any younger than that? Arnold G. Coran (Closure): All the patients in this series that were diagnosed as having renal artery stenosis were operated upon. I think that hypertension due to renal artery stenosis is a surgical disease in the child. The question of the vein graft versus the hypogastric artery is a very important one. We are concerned about the fact that the vasa vasorum of the saphenous vein in small children are quite short, and we think this is the etiology of the saphenous vein dilation. This may not happen with the hypogastric artery. One must be prepared to use either the
897
saphenous vein or the hypogastric artery. The children that did develop venous graft dilation did not have recurrent hypertension. In one child, two of the veins became so dilated, we decided to plicate them. The child did not undergo any change in his blood pressure, that is, it was normal before and after the plication. The question of segmental artery bypass with a graft is a good one. In actuality, although I did not show the details of it, that patient whose arteriogram you saw had an aneurysm right at the trifurcation of the upper renal artery. In order to reconstruct that patient we had to sew the trifurcation to itself, that is, create one opening from three little vessels and then anastomose the saphenous vein to it. So if it is a proximal segmental artery stenosis we still recommend doing a bypass to it. If it is intraparenchymal, then we obviously can not do that and we prefer dilation. In response to Dr. O'Neill's questions, the transverse incision is used because it is easier to get deep into the wound and to turn your needle at right angles to your anastomosis. Heparinization systemically is very important. There are tiny little vessels and they will clot if the blood is not systemically heparinized. The question of the aortotomy: we biopsy all the tissue at the time of repair, both the renal artery and the aorta.