THE SURGERY OF RENAL ARTERY STENOSIS'

By KENNETH OWEN, F.R.C.S.

St Mary's Hospital, Loridon

THE diagnosis of these cases has been fully discussed elsewhere (Brown et a/., 1960) and only a brief summary will be made in this paper. In the majority of patients little help has been gained from the history, most of the patients being in the middle-age group and only one had a history of renal pain.

The finding of an abdominal murmur has been helpful but its absence does not preclude a renal artery lesion. The diagnosis has therefore rested upon clinical investigation, the following tests being used :-

I . Intravenous pyelogram. 2. Radio-active renogram. 3. Angiography. 4. Divided renal function studies. 5. Operative renal artery pressure measurements. 6. Operative biopsy (retrospective and prognostic).

1. Intravenous Pye1ogram.-The characteristic findings in unilateral lesions of decreased renal size, smaller pelvis and increased contrast density on the affected side are now generally Tecognised.

2. Renogram.-Radio-active renography has only recently been done in a few of these cases by Dr Joekes and Dr Sherwood, but the results bear out the value of the method as a screening test which has been found by other workers.

3. Angiography.-Both free aortic injections and selective renal artery catheterisation have been used. The latter method performed by Dr David Sutton has given excellent definition of the renal arteries and has in one or two cases which have previously had free aortography, allowed of more certain diagnosis than aortography. There has been no evidence in this series of aberrant vessels being missed by this technique.

4. Divided Renal Function Studies.-Simultaneous ureteric catheter studies have been done on all patients in whom it was possible to pass ureteric catheters. Maximal diuresis is obtained by using local or low spinal anasthesia for the cystoscopy and giving a urea infusion. Differential sodium and water reabsorption as measured in the Howard test has occasionally been misleading, but these figures in conjunction with creatinine or P.A.H. clearances and concentrations have been of great value, not only in diagnosing a unilateral lesion but in supplying detailed information about over-all renal function.

5. Renal Artery Pressure Measurements.-The final diagnostic step is at operation when simultaneous pressure measurements are taken from the renal artery and aorta. This is done as early as possible in the operation with precautions to avoid displacing or compressing the renal

Read at the Nineteenth Annual Meeting of the British Association of Urological Surgeons at Leeds. July 1963.

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artery either proximal or distal to the recording needle. It is equally important to repeat the readings at the end of the operation to ensure that an adequate circulation has been established.

6. Renal Biopsy.-Percutaneous biopsy has- not been thought advisable because of the risks in these hypertensive patients, but a biopsy is taken from each kidney at operation and is of value in confirming the diagnosis and assessing secondary hypertensive changes.

Indications for Surgery.-The indications for surgery have in general been severe hypertension uncontrolled or poorly controlled by medical means. The exact level of blood pressure at which surgical treatment is thought advisable has varied with the age of the patient, but in general the patients have been severely hypertensive with a diastolic pressure of 120 mm. or over. Many of the patients have had complications such as hypertensive retinopathy.

Surgical Approach.-A transverse incision is used, its level being usually about one inch above the umbilicus but being varied according to the width of the subcostal angle. This incision has been found to give an excellent exposure of both renal arteries and kidneys. Should greater exposure be necessary it can be obtained by extending the incision across the costal margin into the chest, but this has not proved necessary in any cases of the present series. Even if nephrectomy is contemplated this anterior abdominal incision is used where it is desired to confirm the diagnosis by pressure measurements and to obtain a biopsy of the opposite kidney. In poor risk patients with well-established diagnosis or where there has been a previous failed reconstruction operation a loin incision is used for nephrectomy.

The right renal artery is exposed by mobilising the duodenum to the left and the left artery is exposed by incising the peritoneum lateral to the splenic flexure and mobilising this and the descending colon to the right.

SURGICAL MEASURES

1. Nephrectomy.-This is reserved for poor risk cases with a normal contra-lateral kidney or for cases where there has been technical failure of a reconstruction operation or where there is involvement of multiple renal artery branches.

2 . Partial Nephrectomy.-This operation has not been used in the present series as no case with a localised segmental lesion has occurred.

3. Aorto-renal Thrombendarterect0my.-This operation has the advantage of avoiding the use of any foreign material, but in the common atheromatous lesions involving the origin of the renal artery access is often difficult and this may preclude the operation. The factor which limits the use of this operation is the difficulty of obtaining adequate exposure of the aorto-renal junction, the main obstruction being the left renal vein which limits access to both right and left arteries in many cases. This vein may be mobilised by dividing the left spermatic or ovarian vein to allow of slightly more retraction of renal vein and vena cava.

The other factor which limits the use of this operation is that the position of the renal arteries may not allow of oblique aortic clamping between them and it has not been thought justifiable to clamp the aorta above the renals even with hypothermia. It is important to allow for the aortic wall thickness in clamping the' aorta because a thick layer of atheromatous intima may occlude the orifice of the opposite renal artery even though the clamp appears to be safely below it. This was thought to be the cause of several day's oliguria in one patient in this series who had a left thrombendarterectomy with a patch graft.

It is important to carry the incision into the aorta and remove aortic intima around the vessel origin even when the stenosis appears limited to the renal artery. The incision in the artery

T H E S U R G E R Y OF R E N A L ARTERY STENOSIS 9

may be sutured directly or a patch may be inserted to widen the vessel. This has not been thought necessary in most cases and may be harmful in increasing the period of ischzmia as the long suture line required for'a patch takes a much longer time to complete than simple closure of an arteriotomy ; however, where the vessel seems dangerously narrow a patch may be inserted and the segment of the spermatic or ovarian vein may be opened out and used for this purpose.

Splenic to Renal Artery Anastomosis.-This operation has a number of advantages : it can be done without the risks attendant upon clamping the aorta and it involves only one suture line without the use of foreign materials. The splenic artery is usually reached fairly easily behind the pancreas, mobilised to its division into branches and then divided, leaving the spleen nourished by the short gastric vessels. The main difficulty in this dissection is the presence of small pancreatic branches which may tear easily if not demonstrated and ligated.

Two difficulties which have been met are disease in the splenic artery and difficulty in occasional cases in mobilising sufficient length for a tension-free anastomosis. It is therefore important t o assess the splenic artery from the aortogram, by palpation and by taking pressure measurements from the vessel before considering its use. A decision as to whether the length is adequate can sometimes be reached only after mobilisation.

By-pass Grafting.-This operation has been used on the left side when splenic-to-renal anastomosis or thrombendarterectomy is not feasible and on the right side when the latter procedure is not possible. By-pass grafting has not been used as the method of first choice because of doubts as to the long-term survival of the materials which have been used. Plastic materials have been used infrequently because of the thrombosis incidence in other situations in vessels of similar size (Shucksmith and Addison, 1962). Homografts were used initially but recent reports of aneurysm formation and late rupture in other situations (Ashton et al., 1962) have led to a trial of autogenous vein grafts. The saphenous vein has been largely used for this purpose in other situations, but in order to confine the operation to one field a trial is being made of the ovarian or testicular vein which is frequently mobilised or divided in the course of mobilising the vena cava and left renal vein. The usual precaution is taken of identifying the ends carefully so that the vein is inserted with flow in the direction of the valves. The vein dilates to a diameter larger than the normal renal artery. It also lengthens appreciably with danger of kinking. In order to avoid this the aortic clamp is released temporarily after thefirst anastomosis has been made, the distal end of the graft being included. When the graft has filled and stretched with a few palpations the required length is assessed, the vein emptied after the aortic clamp has been reapplied, and the second anastomosis is made.

Excision and end-to-end anastomosis, or division of the renal artery and re-implantation t o the aorta, are only occasionally possible.

RESULTS OF SURGERY

Out of thirty-five cases there have been four deaths within the first post-operative week, three of these being due to coronary thrombosis. Although this mortality seems on the high side it is not thought unduly high when considered in relation to the severity of the underlying disease, many of the patients having had previous cormary or cerebral thrombosis and operation having been undertaken in several cases as a last resort when the hypertension was otherwise untreatable and the prognosis a matter of weeks. The death of one patient the day before he was due to have an operation emphasises the poor-risk patients with whom one is dealing. There have been two further deaths in the follow-up period, one at just over a year in a patient whose blood-pressure had returned to normal-post-operatively, and another at one and a half years in a patient who had been only slightly improved after operation.

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Of the survivors fourteen have had an excellent result with return of the blood-pressure to normal without any further drug treatment and regression of retinal changes when these were present pre-operatively. Seven have been appreciably improved with blood-pressure controlled by drugs at normal or near-normal levels when this was not previously possible. The other cases have had no benefit from the operation. It is of interest to note that in none of these cases was there a temporary drop due to the non-specific effect of a major operation. The general pattern

FIG. 1 Aortogram of a norrnotensive patient investigated for peripheral vascular disease, demonstrating an apparent left renal artery stenosis

without hypertension.

has been that the cases which were going to do well had a slight drop in the early post-operative period and this increased in the following weeks or months whereas the cases that did not do well eventually had an unchanged or an even higher blood-pressure immediately after surgery.

There does not appear to be any obvious relation between the procedure adopted and the result, but in such small groups no statistical significance can be demonstrated. The failures cannot all be due to technical failure of revascularisation as one case has occurred of an apparently certain unilateral stenosis in which nephrectomy failed to affect the blood-pressure.

Three cases are worthy of mention in commenting upon the results of surgery and illustrating some of the difficulties.

I . Figure 1 shows the aortogram of a patient zged 60 who was being investigated for peripheral vascular disease and prostatic symptoms. His blood-pressure was 125/85 mm. Hg despite an apparent left renal artery stenosis. The chances of such a lesion occurring coincidentally in a patient with essential hypertension cannot be insignificant. with both atheroma and essential hypertension being so common in middle age. It is also possible that essential hypertension may produce a secondary atheromatous plaque in the renal artery as in other situations so that one may expect to find occasional cases in which a renal artery stenosis is coincidenta1,or even secondary to hypertension rather than being the primary cause. This could account for some failures and, conversely, the presence of such a lesion in a patient with a labile blood-pressure could account for some of the good results of surgery if this is done on too slight an indication or without function studies to confirm the presence of a functional as well as an anatomical stenosis.

T H E S U R G E R Y OF R E N A L A R T E R Y STENOSIS

Fig. ?.-Right renal artery stenosis due to fibro-muscular hyperplasia.

F i g . 3.-A, B, By-pass graft in the patient shown in Figure 2.

FIG. 2

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FIG. 3

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FIG. 4

Fig. 4.-A, B, Arteriogram demonstrating left renal artery stenosis and normal right renal

artery.

Fig. S.-Right renal arteriogram demonstrating the development of stenosis in the artery shown in Figure 4, A, two years after

the left side had been treated.

FIG. 5

T H E S U R G E R Y O F R E N A L A R T E R Y S T E N O S I S 13

2. Figure 2 shows the arteriogram of a female patient aged 50 with severe hypertension present for many years and a typical lesion of fibro-muscular hyperplasia. It appeared that this lesion was confined to a central segment of the artery and a t operation this was treated by excision and end-to-end anastomosis. However, post-operative pressure measurenients showed a persistent pressure drop between the aorta and the distal renal artery. The artery was therefore reopened and several small flaps of hypertrophic intima were found distal to the anastomosis ; these were not evident on the X-ray and could not be palpated externally. A by-pass graft was then inserted from the aorta to the distal renal artery at its division (Fig. 3) and the patient has done well. The presence of such ill-defined intimal lesions in fibro-muscular hyerplasia may lead to the condition being missed and it is conceivable that such lesions in the distal branches or in the opposite kidney may account for failures of surgical treatment.

3. Figure 4 (A and B) shows the arteriogram of a patient aged 45 with left renal artery stenosis and severe crippling hypertension. He was treated initially by thrombendarterectoniy but this was followed by thrombosis and a left nephrectomy was done. Following this operation the patient’s blood-pressure returned to normal and he was symptom-free. However, some two years later he returned with further symptoms and his blood-pressure had again risen to its previous high levels. At this time he had a coronary thrombosis. Further investigation demonstrated that the right renal artery which had previously been normal had developed an atheromatous stenosis (Fig. 5) , and with some hesitation it was decided to treat this with a by-pass graft as his outlook was thought otherwise to be extremely poor. This operation was followed by a second remission, and although he is now on small doses of hypotensive drugs his blood-pressure has returned to normal. This development of a lesion in the opposite renal artery is another possible cause of failure following operation and demonstrates the importance of re-investigating such patients. One further theoretical cause for the failure of surgery is the perpetuation of hypertension because of secondary necrotising arteriolitis in the contralateral kidney. However, despite experimental and some clinical evidence of this finding the extent of secondary arteriolitis in this series as judged by biopsy specimens has been nitich less than expected.

CONCLUSION

It has been possible to deal with only a few aspects of this condition in this short paper. In the series of cases which have been reported apparent cure of hypertension has been achieved by a variety of surgical techniques but there are still a number of diagnostic and technical difficulties t o be overcome if better results are to be achieved in these poor-risk patients.

REFERENCES

ASHTON, F., SLANEY, G., and RAINS, A. J. H. (1962). Brit. med. J., 2 , 1149. BROWN, J. J., OWEN, K., PEART, W. S., ROBERTSON, J . I. S., and SUTTON, D. (1960). Brif. med. J., 2, 327. SHUCKSMITH, H. S., and ADDISON, N. V. (1962). Brit. med. J., 2 , 1144. ,