Posttransplant hypertension: studies of cortical blood flow and the renal pressor system

Thoracic endovascular aortic repair for type B aortic dissection after renal transplantation

Thoracic endovascular repair (TEVAR) is an effective treatment for type B aortic dissection (TBAD). Here, we evaluated the early-midterm effectiveness and safety of TEVAR for treating TBAD patients after renal transplantation. Six patients with TBAD treated with TEVAR after renal transplantation were recruited between February 2012 and December 2016. They were then followed up with clinical examinations and computed tomography angiography (CTA). TEVAR was successfully performed in all patients (100%), and the primary tear sites were well covered by stents with or without coverage of the left subclavian artery. No severe complications occurred in any patient during perioperative period. The one-year survival rate was 100%, one patient died of renal graft failure and heart failure four years after TEVAR; the remaining five patients (83.3%) survived and exhibited no severe complications. Our findings show that TEVAR provides satisfactory short-midterm results for TBAD patients after renal transplantation. Moreover, our experience shows that it need relative longer proximal landing zone to prevent the endoleak and recurrence. However, regular hematodialysis, long-term immunosuppressive therapy, and blood pressure control remain crucial factors to prolong survival. Long-term follow-up studies are needed to evaluate the long-term prognosis in these patients.

The renin-aldosterone system and renal hemodynamics in patients with posttransplant hypertension

Plasma renin concentration (PRC), plasma aldosterone concentration (PAC), renal plasma flow (RPF) and glomerular filtration rate (GFR) have been studied in 19 patients who had received a renal allotransplant. Group 1 consisted of 7 normotensive and group 2 of 12 hypertensive patients. Bilateral nephrectomy was performed in all patients; all were on a fixed daily sodium intake, and no antihypertensive agents were given. No significant differences were found between the groups in age, time after transplantation or dosages of prednisone. PRC and PAC were normal in all but one patient in group 1 and two in group 2. In these three patients a slight elevation of PRC was measured. After one hour in the erect position, a significant increase was measured in PAC, but not in PRC in both groups. After 6 days on a 10 mEq sodium diet, PRC and PAC increased significantly in both groups. After a further 6 days on the diet plus 150 mEq sodium daily, significant decreases in PRC and PAC were measured in both groups. No differences were detected in PRC or PAC between groups 1 and 2 either before or after the two dietary periods. RPF was significantly lower in the hypertensive group, whereas no significant difference was found in GFR between the groups. No significant relationship could be demonstrated between blood pressure (BP) and PRC or PAC, and PRC and PAC were not correlated to each other. RPF was significantly correlated to mean BP and PRC in the normotensive group but not in the hypertensive. It is concluded that PRC and PAC are normal in most patients with posttransplant hypertension, whereas the RPF is decreased. It is suggested that an abnormal regulation of renin secretion plays a role in the sustained elevation of BP after renal allotransplantation.

Plasma renin, plasma aldosterone and exchangeable sodium in normotensive and hypertensive kidney transplant recipients with and without transplant renal artery stenosis

Blood pressure (BP), plasma renin concentration (PRC), plasma aldosterone concentration (PAC) and exchangeable sodium (ES) were studied in 19 kidney recipients on different fixed levels of sodium intake after successful kidney transplantation. The following groups of kidney recipients were investigated: group 1: 7 normotensives, group 2:7 hypertensives without transplant renal artery stenosis (TRAS), group 3:5 hypertensives with angiographically verified TRAS. Hypertension in the recipients without TRAS (group 2) was characterized by a positive correlation between BP and ES and a normal response of PRC and PAC to a fixed low (10 mEQ/day) and high (150 mEq/day) sodium intake. In contrast, hypertension in the recipients with TRAS (group 3) was characterized by a normal or varyingly increased PRC on a liberal sodium intake and a reduced response of PRC to sodium restriction, whereas PAC did not differ from the other groups of recipients. In one recipient in group 3 who underwent surgical correction for TRAS, PRC and PAC decreased before operation during sodium restriction, but BP remained high until after operation, when it normalized simultaneously with a decrease in ES. The results indicate that sodium retention is involved in the pathogenesis of posttransplant hypertension and suggest that an increased activity of the renin--angiotensin system is counterbalanced by an accumulation of sodium in TRAS.

Secondary hypertension: evaluation and treatment

Most patients with hypertension in the United States have essential (primary) hypertension (95%), the cause of which is unknown. The remaining 5% of adults with hypertension have the secondary form of hypertension, the cause and pathophysiologic process of which are known. Internists and other primary care physicians refer to this as treatable or curable hypertension, because the hypertension can be managed or even controlled with medications. Similarly, the condition is called surgical hypertension by surgeons in the belief that once the cause is determined and identified, surgical intervention will result in cure of hypertension. Secondary causes of hypertension include renal parenchymal disease, renovascular diseases, coarctation of the aorta, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and hyperparathyroidism. Occasionally included in this category are alcohol- and oral contraceptive-induced hypertension and hypothyroidism, but these conditions are not discussed herein. The evaluation of secondary hypertension is of interest and can bring together different facets of anatomy, physiology, pharmacology, and radiology in the medical and surgical treatment of these disorders. Despite enthusiasm that can be generated in the evaluation of these conditions, evaluation can be expensive and should not be conducted for all patients with hypertension. Features that aid in the diagnosis of secondary hypertension include the following: 1. Onset of hypertension before the age of 20 or after the age of 50 years. The presence of hypertension at a young age may suggest coarctation of the aorta, fibromuscular dysplasia, or an endocrine disorder. Hypertension found for the first time after the age of 50 years may suggest the presence of renovascular hypertension caused by atherosclerosis. 2. Markedly elevated blood pressure or hypertension with severe end-organ damage, as in grade III or IV retinopathy. These findings suggest the presence of renovascular hypertension or pheochromocytoma. 3. Specific body habitus and ancillary physical findings. For example, truncal obesity and purple striae occur with hypercortisolism, and exophthalmos is associated with hyperthyroidism. 4. Resistant or refractory hypertension (poor response to medical therapy usually necessitating use of more than three antihypertensive medications from three different classes). 5. Specific biochemical test that suggest the existence of certain disorders, such as hypercalcemia in hyperparathyroidism, hyperglycemia in Cushing's syndrome and pheochromocytoma, and unprovoked hypokalemia with renin-producing tumors, primary hyperaldosteronism, or renin-mediated renovascular hypertension. 6. Other characteristics that may suggest secondary hypertension such as abdominal diastolic bruits (renovascular hypertension), decreased femoral pulses (coarctation of the aorta), or bitemporal hemianopias (Cushing's disease). A combination of a good history and physical examination, astute observation, and accurate interpretation of available data usually are helpful in the diagnosis of a specific causation.

Effects of dietary protein in patients with chronic renal transplant rejection

Dietary protein restriction reduces proteinuria and slows the progression of renal failure in a variety of renal diseases in native kidneys. Such beneficial effects may be mediated by the multiple renal effects of dietary protein including those on glomerular capillary hemodynamics and the renin-angiotensin system. The role of dietary protein restriction in the management of chronic renal transplant rejection is, however, unclear. This study was therefore undertaken to examine the effects of dietary protein restriction in patients with chronic rejection. Fourteen patients with biopsy proven chronic rejection, who had been on a self-selected home diet of 1.0 +/- 0.1 g protein/kg/day, were randomly assigned, using a crossover design to two 11-day periods, one on a low protein diet (0.55 g/kg/day) and the other on a high protein diet (2 g/kg/day). The effect of these diets on renal hemodynamics, proteinuria, plasma renin activity, and nutritional status was examined. The low protein diet was associated with a significant improvement in glomerular permselectivity in all patients as evidenced by a significant fall in the fractional clearance of albumin and IgG and reduction in 24-hour urinary excretion of total protein, albumin and IgG without any change in blood pressure, glomerular filtration rate, or renal plasma flow. Compared to the proteinuria at the beginning of each diet, a high protein diet did not increase but a low protein diet significantly decreased the proteinuria. The low protein diet was also associated with a significant reduction in plasma renin activity, suggesting that part of the beneficial effect of protein restriction was related to the suppression of the renin-angiotensin system.(ABSTRACT TRUNCATED AT 250 WORDS)

Percutaneous transluminal angioplasty for transplant renal artery stenosis in children

Severe hypertension developed secondary to renal artery stenosis in 11 of 229 children who received a renal allograft. Renal artery stenosis was suspected because of de novo development of hypertension or exacerbation of pre-existing hypertension, which was detected 1 to 24 months after transplantation. Selective renal angiography was performed 2 to 74 months after transplantation (mean 13 months). Follow-up was 1 to 8 years (mean 2.5 years). The stenosis involved the anastomosis in 5 patients and was distal to the anastomosis in 6. One graft had an arteriovenous malformation. Seven grafts were suitable for vessel dilation; percutaneous transluminal angioplasty was partially successful in 4 cases in which the stenosis occurred at the anastomosis. The remaining patients were treated with medical therapy alone and the grafts were not lost. Our findings suggest that strictures distal to the anastomosis rarely are amenable to percutaneous transluminal angioplasty and should be treated medically whenever possible. Strictures at the anastomosis respond to vessel dilation but antihypertensive medication also often is required. An operation should be reserved for patients who do not respond to these measures.

[Duplex sonography in the diagnosis of renal artery stenoses following allogenic kidney transplantation]

Posttransplant renal artery stenosis (TRAS) as a cause of secondary hypertension is reported with an incidence of 1 to 10%. Early diagnosis of TRAS should be made by non-nephrotoxic and non-invasive means to lower the risk of hypertension. One to 66 months after kidney transplantation 335 patients underwent Duplex-scanning, 38 of cases for clinical tentative diagnosis of TRAS. Parameters for clinical diagnosis of TRAS were diastolic hypertension greater than 100 mm Hg with resistance to therapy (A), an abdominal bruit over the transplant (B), disturbance of renal function (serum-creatinine greater than 2 mg/dl) (C). Admission to study followed the parameter-combination A + B. A + C, B + C. Rejection crisis was excluded in 18/38 cases by fine needle biopsy, cyclosporine over-dosage was negative in 38/38 cases, 20/38 cases had normal renal function. Duplex-/Doppler-ultrasound criteria for TRAS were systolic peak velocity greater than 100 cm/s-1 and broadening of the diastolic frequency spectra with a smooth decline in diastole to an elevated diastolic level. In 32/38 cases (84.2%, n = 38) diagnosis of TRAS was made by duplex-scanning, angiography confirmed the result in 30/32 cases (93.75%, n = 32); sensitivity was 88.2% with a specificity of 66.6%. Duplex-scanning as a primary diagnostic means for TRAS seems a promising method compared to e.g. radionuclide imaging or angiography. Duplex-scanning is a non-nephrotoxic and non-invasive procedure repeatable at any time with only few preliminary conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-transplant hypertension in the rat: effects of captopril and native nephrectomy

In patients with well-functioning renal allografts, the presence of diseased native kidneys appears to be a common cause of elevated blood pressure. We evaluated the role of native kidneys in post-transplant hypertension using a rat model in which the confounding variables of rejection and immunosuppression could be eliminated. To produce disease in native kidneys. PVG rats were subjected to 5/6 nephrectomy. Four weeks following renal ablation, these hypertensive animals were transplanted with kidneys from syngeneic PVG donors. Four weeks later, the effects of captopril and native nephrectomy on blood pressure and renal hemodynamics were examined. Animals with remnant native kidneys which received non-rejecting renal isografts had sustained hypertension, elevated plasma renin levels and reduced transplant function. In these animals, administration of captopril reduced systemic blood pressure. Despite the reduction in blood pressure, PAH clearance by the transplanted kidney increased markedly while GFR rose modestly. Removal of the remnant native kidney also acutely lowered blood pressure. However, compared to captopril, native nephrectomy produced a more marked increase in GFR without significantly affecting renal blood flow. In this model of post-transplant hypertension in the rat, elevated blood pressure and reduced isograft function are mediated by the diseased native kidney, in part through the effects of angiotensin II. These data suggest that ACE inhibitors and native nephrectomy may have beneficial hemodynamic effects in patients with post-transplant hypertension caused by native kidneys.

Hypertension in cyclosporine-treated renal transplant recipients is sodium dependent

PURPOSE

Physicians increasingly prescribe cyclosporine as an immunosuppressive agent for both organ-transplant and non-organ-transplant recipients. Investigators have reported a high incidence of drug-induced hypertension even when clinical nephrotoxicity was not present. We wanted to determine the reason.

PATIENTS AND METHODS

A comparison was made of hypertension in 15 cyclosporine-treated transplant recipients with that in a similar group of 15 azathioprine-treated transplant recipients.

RESULTS

Hypertension in the cyclosporine group responded differently from that seen in the azathioprine group and from previously described forms of post-transplantation hypertension. Hypertensive cyclosporine-treated patients show a sodium acquisitive renal state that responds to sodium restriction. Unlike rat models, which suggest cyclosporine-induced stimulation of the renin-angiotensin system, or previous forms of post-transplant hypertension in humans, plasma renin levels were not elevated and blood pressure did not respond to a test dose of captopril.

CONCLUSION

Hypertension in cyclosporine-treated patients is an iatrogenic form of hypertension that may be associated with an early, subtle, renal defect in sodium excretion, a genesis of hypertension that is consistent with Guyton's view of essential hypertension.

Influence of cyclosporine on posttransplant blood pressure response

The suggestion that hypertension is more prevalent in renal allograft recipients receiving cyclosporine (CyA), particularly those displaying nephrotoxicity, was tested by reviewing 200 patients' courses, including 92 cadaver (CAD) and 58 living-related (LRD) transplants using CyA and prednisone immunosuppression, and 19 CAD and 31 LRD transplants using azathioprine (Aza) and prednisone, all of whom had at least 1 year posttransplant complete outpatient follow-up. Both groups had a mean age of 33 years with a similar distribution of renal failure etiologies. Renal function was significantly impaired in the CyA group at all intervals (P less than .001, t test). The prevalence of hypertension was higher in the CyA group at all intervals, becoming significant at 12 (P less than .01) and 24 (P less than .05) months following transplantation (chi 2). While there was only a significant difference in mean diastolic BP at 12 months (P less than .05, t test), the mean number of antihypertensive and/or diuretic medications was significantly greater in the CyA group at 1 and 6 months (P less than .001) and at 12 months (P less than .01). By 24 months, the mean number of all antihypertensive and/or diuretic medications was no longer significantly different. However, the antihypertensive and diuretic requirements of the CyA group diminished with time, suggesting that the hypertension is not progressive if the CyA serum trough levels are maintained in the nontoxic range (less than 200 ng/mL).

Post-renal-transplant hypertension. Urine volume, free water clearance and plasma concentrations of arginine vasopressin, angiotensin II and aldosterone before and after oral water loading in hypertensive and normotensive renal transplant recipients

Urine volume (V), free water clearance (CH2O) and plasma concentrations of arginine vasopressin (AVP), angiotensin II (A II) and aldosterone (Aldo) were determined before and three times during the first 5 h after an oral water load of 20 ml/kg body wt in 19 patients with post-renal-transplant hypertension (group I), in 13 normotensive renal transplant recipients (group II) and in 20 control subjects (group III). Both V and CH2O increased significantly in all groups, but considerably less in groups I and II than in group III. When CH2O was related to glomerular filtration rate no differences existed between patients and control subjects. Basal AVP was the same in groups I (3.3 pmol/l, median) and II (3.0 pmol/l), but significantly (p less than 0.01) higher than in group III (1.9 pmol/l). Basal A II was significantly (p less than 0.01) elevated in group I (18 pmol/l) when compared to both groups II (10 pmol/l) and III (11 pmol/l), and the level was independent of the presence of native kidneys. Basal Aldo was the same in all groups. During loading, AVP was reduced in all groups, A II was almost unchanged, and Aldo was increased in groups I and II and reduced in group III depending on alterations in serum potassium. Thus urinary diluting ability is reduced in renal transplant recipients due to a reduced glomerular filtration rate. The enhanced A II in hypertensive renal transplant recipients gives further evidence for the point of view that hypertension is angiotensin-dependent in most of these patients.

Hypertension and kidney transplantation

Patients with kidney transplants are often hypertensive. Investigators have described the characteristics of this hypertension in man. Moreover, the hypertension of kidney transplant patients has a higher probability of being responsive to surgical intervention than does hypertension in the general population. Yet the mechanisms of the many varieties of posttransplantation hypertension are not known in detail. Detailed studies that would best be done in animal models are rare. Both medical and surgical management of this transplantation-associated complication needs further study.

Hypertension after successful renal transplantation

Thirty-three renal allograft recipients who had high blood pressure (mean arterial pressure more than 105 mm Hg) at least one year after their successful transplant operation were compared with 23 normotensive kidney transplant recipients (mean arterial pressure less than 105 mm Hg) at the General Clinical Research Center. The patients with higher blood pressure had markedly and significantly higher (96 percent) renal vascular resistance and significantly lower (41 percent) renal plasma flow. Responses to salt loading and restriction were suggestive of marked activity of the renin-angiotensin system as were plasma renin activity measurements. Subsequent follow-up has revealed chronic rejection or renal artery stenosis as a probable cause of hypertension for 11 of the 33 patients. The remaining 22 patients had increased renal vascular resistance and decreased renal plasma flow indistinguishable from that in the 11 patients in whom follow-up revealed a cause for their persistent hypertension; however, 21 of these 22 patients have their native kidneys in place.

Remission of essential hypertension after renal transplantation

Six patients in whom "essential hypertension" led to nephrosclerosis and kidney failure received kidney transplants from normotensive donors. After an average follow-up of 4.5 years, all were normotensive and had evidence of reversal of hypertensive damage to the heart and retinal vessels. These six patients, all of whom were black, and six control subjects matched for age, sex, and race were admitted to the General Clinical Research Center for 11 days for observation of their blood pressure and their responses to salt deprivation and salt loading. Mean arterial pressure (+/- S.E.M.) among the patients who had previously had essential hypertension was similar to that of the normal controls (92 +/- 1.9 vs. 94 +/- 3.9; P not significant), and both groups had similar responses to salt deprivation and salt loading. Thus, essential hypertension in human beings is shown to be similar to the hypertension seen in spontaneously hypertensive rats in that both can be corrected by transplantation of a kidney from a normotensive donor. This observation supports the concept of the primary of the kidney in causing essential hypertension.

Screening for transplant renal artery stenosis in hypertensive recipients using digital subtraction angiography

Digital subtraction angiography was used in 10 renal allograft recipients with sustained hypertension after transplantation to detect transplant renal artery stenosis. Recipients with end-to-end vascular anastomoses were visualized adequately in the anteroposterior projection. Two cases of transplant renal artery stenosis were identified by digital subtraction angiography and then verified by catheter angiography. Patients with end-to-side vascular anastomoses may require additional oblique projections. Digital subtraction angiography is a safe, noninvasive and cost-effective screening procedure to diagnose transplant renal artery stenosis in most recipients. Catheter angiography can be applied more selectively to those recipients with stenosis observed by digital subtraction angiography or when more detailed imaging is required.

Urinary kallikrein excretion after renal transplantation: relationship to hypertension, graft source, and renal function

The role of the renal kallikrein-kinin system in the pathogenesis of hypertension and various forms of renal dysfunction after human renal transplantation has been assessed by measurement of urinary kallikrein activity in 41 renal transplant recipients. The urinary tosyl arginine methyl esterase assay was used. The urinary kallikrein in these patients appeared to originate from the transplanted kidney and not their own diseased kidneys. Twenty-three recipients had hypertension (mean blood pressure 156 +/- 3/98 +/- 2 mm Hg) and excreted less kallikrein (4.0 +/- 1.2 versus 12.5 +/- 4.0 esterase units [EU] per 24 hours, p less than 0.05) than their 18 normotensive counterparts (mean blood pressure 132 +/- 2/77 +/- 1 mm Hg, both p less than 0.01). Subjects with renal complications of transplantation (acute tubular necrosis [ATN], nine patients, or acute rejection [AR], eight patients) also excreted less kallikrein than the 28 subjects without such complications (3.4 +/- 0.9 versus 10.3 +/- 2.7 EU/24 hours, p less than 0.02). Among those with acute renal complications, subjects with ATN excreted less kallikrein than those with AR (1.3 +/- 0.3 versus 5.7 +/- 1.7 EU/24 hours, p less than 0.02). Cadaver graft recipients excreted less kallikrein than living related donor graft recipients (2.1 +/- 0.4 versus 13.0 +/- 3.5 EU/24 hours, p less than 0.01), perhaps reflecting their higher blood pressures (mean systolic pressure 151 +/- 3 versus 140 +/- 3 mm Hg, p less than 0.04), relatively impaired renal function (creatinine clearance values 42 +/- 8 versus 62 +/- 5 ml/min, p less than 0.04), and higher incidence of ATN (nine cases versus none). The kallikrein-kinin system may be involved in the pathogenesis of hypertension and some forms of renal dysfunction after renal transplantation.

The improving utility of renal transplantation in the management of end-stage renal disease

The results achieved by treating patients with end-stage renal failure with allotransplantation have improved dramatically since the 1950s when immunosuppression was induced by total body irradiation and there was a lack of HLA typing. Although long-term hemodialysis offers prolonged survival and partial rehabilitation for many individuals with end-stage renal disease, the technique is inconvenient and time consuming. Patients are restricted by necessary proximity to the machine, dietary limitations, potential failure of access sites, and complications of various organ systems. Despite the availability of dialysis and the federal funds to partially pay for treatment, long-term dialysis still remains a costly process for the individual in need of care. During the same period when dialysis techniques improved and became widely available, transplantation of the human kidney became an established and justified treatment for some patients with end-stage renal disease. Those with successful kidney allografts may achieve remarkable recovery and are often able to return to normal lives. One of the more striking improvements in the results of renal transplantation in recent years had been the decline in morbidity and mortality. Mortality by the end of the first year after transplantation during which time most deaths occur, is currently less than 5 percent in a number of major medical units. In part, this decline represents a change in philosophy by transplant teams, who now tend to decrease immunosuppression and sacrifice the kidney rather than the patient in instances of inexorable rejection. In addition, declining mortality is directly attributable to improved methods of preventing, discovering, and treating patients with potential or real infections. More recently, in some centers, the rate of successful engraftment has shown gratifying improvement due to refinements in tissue typing, improved cross matching, new immunosuppressive therapies, and pretransplant conditioning with blood products. These recent improvements are the primary focus of this review. Unfortunately, until very recently, rates of functional survival of allografts have not been satisfactory.

Peripheral plasma renin activity (PRA) in recipients with allograft artery stenosis; its diagnostic value in acute stage hypertension

Peripheral PRA was examined in 11 patients with graft artery stenosis after the onset and throughout the course of hypertension. In the acute stage PRA was elevated in 9 patients and decreased to normal in the later stage of hypertension in all but 1 patient with malignant hypertension. The findings suggest that the determination of peripheral PRA is helpful in diagnosing graft artery stenosis only in the acute stage of hypertension, but it has no unequivocal value to the prognosis of hypertension or indication for operation.

Parathyroid hormone: a determinant of posttransplant blood pressure regulation

Persistent hyperparathyroidism and its attendant hypercalcemia have been implicates as possible etiologic factors in posttransplant hypertension. To better define the role of parathyroid hormone (PTH) and calcium in posttransplant blood pressure homeostasis, we measured the acute response of blood pressure, ionized calcium (Ca++), plasma renin activity (PRA), and parathyroid hormone (PTH) to a 4-hr infusion of calcium (15 mg/kg) and an isoproterenol injection (0.15 mg SC) in seven normal subjects and 13 renal transplant (Tx) recipients with stable graft function and persistent hyperparathyroidism. Transient hypercalcemia produced a significant (p less than 0.01) increase in the systolic blood pressure (delta SBP) and suppression of PTH (p less than 0.001) in the posttransplant subjects. There was a significant (p less than 0.02) inverse correlation between changes (delta) in PTH and delta SBP in these subjects. There was no correlation between the delta SBP and either the change in Ca++ (delta Ca++) or the change in PRA (delta PRA) observed in the Tx recipients administered calcium. Following isoproterenol administration, SBP increased (p less than 0.01), PTH fell (p less than 0.05) and Ca++ was only minimally increased in the Tx recipients. A virtually identical, significant (p less than 0.05) inverse correlation existed between the delta PTH and delta SBP observed in the transplant subjects. Greater suppression of PTH was associated with a larger increase in systolic blood pressure. Transient hypercalcemia of comparable degree in normal subjects caused an insignificant increase in their blood pressure. The fact that PTH suppression in the normals was substantially (0.01) less (delta PTH -13 microliter/Eq/ml versus -65 microliter/Eq/ml in the transplant group) with a similar increase in serum calcium suggests that the blood pressure response to transient hypercalcemia is more dependent on PTH suppression than the level of ionized calcium. Plasma renin activity was unchanged during the blood pressure fluctuations induced by either the calcium or the isoproterenol administration to the normal subjects. Under the conditions of this study, endogenous parathyroid hormone has the characteristics of a vasodepressor hormone and may have a role in blood pressure regulation in transplant recipients with hyperparathyroidism. Since the vasodepressor effect can be dissociated from delta Ca+ and delta PRA, such a conclusion seems warranted. The implications of these findings for all subjects with renal disease requires further investigation.

Surgical correction of posttransplant renovascular hypertension

The incidence of renovascular hypertension in the transplanted kidney is reported to range between 5 and 15%. A review of 391 consecutive renal transplant patients revealed 16 patients (5.4%) with hypertension secondary to partial obstruction of renal arterial blood flow. The clinical course of this group of patients was marked by early normotension followed by progressive diastolic pressure elevation, with improving renal function and loss of accumulated excess volume. Five etiologic factors are responsible for impaired arterial flow in this group of patients. Indication for operation was based on hypertension and/or impaired renal function. Patch angioplasty using saphenous veins was the procedure of choice in most instances. The average blood pressure was 185 mmHg; systolic/125 mmHg; diastolic preoperatively, compared with 140 mmHg; systolic/90 mmHg: diastolic postoperatively. Twelve of 16 patients had good results, and improvement in renal function was observed in eight patients. Serum renin levels did not correlate well with the operative findings. The use of meticulous technique, combined with maximum use of autogenous tissue, is emphasized.

Transplant renal artery stenosis

Renal artery stenosis occurred in 13.5% of 229 consecutive cadaver renal transplants performed at the Royal Melbourne Hospital over an eight and a half year period. Clinical and laboratory indices which suggested the diagnosis were examined. The presence and severity of hypertension were of little predictive value, while deterioration of renal function for which other causes had been excluded and the histological appearance of renal biopsy speciments were valuable in suggesting the diagnosis. A selective approach in both investigation and attempted surgical repair is recommended.

Renovascular hypertension after kidney transplantation

The development of hypertension after kidney transplantation was examined in a consecutive series of 83 transplantations (79 patients) with a graft survival of more than 30 days. After transplantation, 50% of the normotensive recipients developed mild or severe hypertension, while 74% of the hypertensive recipients remained hypertensive. Stenosis of the graft artery with a narrowing of the diameter of more than 50% was found in 13 patients and in 3 patients a minor or peripheral stenosis was found. Significantly more stenoses were seen in the presence of two donor arteries, whereas no other etiological factors could be shown. In arterial stenosis, severe hypertension was established within a few months after transplantation, but in spite of satisfactory controlled blood pressure and good graft function, hypertensive crises could arise. It is therefore concluded that arteriography and renin analysis should be considered in all cases of severe hypertension, and surgical correction should be considered when arterial stenosis is present.

Role of the renin-angiotensin system in post-transplantation hypertension in patients with multiple kidneys

To define the role of the renin-angiotensin system in post-transplantation hypertension we studied 12 hypertensive recipients of renal transplants. The patients received saralasin acetate, an angiotensin II antagonist, while on a normal sodium diet and again after seven days of sodium restriction. In six patients with only one kidney, saralasin did not lower blood pressure on either diet; salt depletion did not lower systolic or diastolic blood pressures. In six patients with more than one kidney, salt depletion also did not lower blood pressure; however, salt depletion plus saralasin lowered their systolic pressures from a mean (+/- S.E.M.) of 146 +/- 9 to 128 +/- 8 mm Hg, and mean diastolic pressures fell from 103 +/- 5 to 89 +/- 5 (P less than 0.001). In four of five patients renal-vein renin activity was greater in one or more host kidneys than in the transplant kidney (or kidneys). Although pre-transplant blood pressure was the same in both groups, post-transplantation hypertension is more likely to be angiotensin II-dependent in patients with more than one kidney.

Renal artery stenosis in hypertensive renal transplant recipients

Reconstruction of a stenotic renal artery was done on 5 hypertensive renal transplant recipients, all of whom had deterioration of renal function when the stenosis was detected. After reconstruction renal function improved in 4 of the patients. The blood pressure was easier to control in all 5 patients, with 3 becoming normotensive. A high preoperative plasma renin activity returned to normal postoperatively in 4 patients. No recurrences were observed after a followup of more than a year.

The significance of body sodium content in hypertension following renal transplantation: exchangeable sodium and plasma renin concentration before and after renal transplantation

The purpose of the present study was to determine the importance of body sodium content in hypertension following renal transplantation using measurements of exchangeablesodium (NaE) before and after transplantation. Plasma renin concentration (PRC) was also investigated. In the present study the necessity of a reference for expressing NaE values was eliminated because the subjects investigated acted as their own controls. The study included fourteen recipients, of whom seven were normotensive with an average blood pressure (BP) of 136/84 mmHg and seven were hypertensive with an average BP of 182/113 mmHg after renal transplantation. In the hypertensive NaE increased significantly (mean 22%) in contrast to an insignificant decrease in NaE in the normotensives (mean, -5%). The change in NaE was positively correlated to the mean BP after renal transplantation (p = 0.69, n = 14, P less than 0.02). BP and NaE were not correlated to prednisone dosages. PRC was normal in all the hypertensives. The results strongly suggest that sodium accumulation in the body, which is not prednisone-dependent, is involved in the pathogenesis in post-transplant hypertension.

Post-transplant hypertension. Normoreninemic severe hypertension treated by bilateral nephrectomies

In a nineteen-year-old male in whom severe and protracted hypertension developed after a successful renal transplantation, the removal of the diseased kidneys resulted in restoration of normal blood pressure. Prenephrectomy blood samples obtained from the venous drainage of all three renal veins demonstrated no evidence for excessive renin secretion, nor was a significant difference in renin activity found between any two kidneys. It is postulated that the patient may be a clinical variant of the experimental form of renal hypertension with normoreninemia. Alternatively, the remnant kidneys may be implicated to produce a nonrenin pressor substance.

Treatment of high-renin hypertension with propranolol in children after renal transplantation

Ten children with hypertension poorly controlled with other drugs and high peripheral plasma renin activity after renal transplantation were treated with propranolol. The mean systolic pressure decreased from 139 to 127 mm Hg (p less than 0.05) and the mean diastolic pressure from 98 to 83 mm Hg (p less than 0.01). Eight children had an antihypertensive response; two did not respond. The maximum dose of propranolol in responders varied from 1.0 to 6.2 mg/kg/day and duration of treatment until response varied from four to 49 days. PRA, repeated in seven responders, decreased in all (p less than 0.01). There was no correlation between changes in PRA and blood pressure. Propranolol was well tolerated and was a valuable antihypertensive drug in these children.

Arteriovenous fistula complicating renal transplantation

A case of arteriovenous fistula of the major transplant vessels contributing to posttransplant hypertension hypertension and severe microangiopathic hemolytic anemia is reported. Improvement in blood pressure and correction of anemia followed ligation of the fistula. This case reinforces the need for diagnostic evaluation of all patients with sustained post-transplant hypertension.

Abnormalities of renal perfusion and the renal pressor system in dogs with chronic aortic coarctation

To clarify the role of the renin-angiotensin system in coarctation hypertension, 2-year-old inbred dogs with chronic neonatally induced thoracic aortic coarctation were subjected to 6 days of rigorous salt restriction. The following parameters were then measured: glomerular filtration rate, renal plasma flow, plasma renin activity, plasma renin concentration, renin reactivity, and renin substrate concentration. Glomerular filtration rate and renal plasma flow were significantly lower in salt-restricted coarcted dogs: 3.0 +/- 0.2 and 9.0 +/- 1.5 ml/min kg-1, respectively, compared with values of 4.0 +/- 0.2 (P less than 0.005) and 13.2 +/- 0.6 (P less than 0.025) ml/min kg-1 in salt-restricted controls. Plasma renin activity was abnormally high in experimental dogs: 13.5 +/- 2.5 vs. 4.5 +/- 1.5 ng angiotensin I/ml hour-1 in controls (P less than 0.005). In addition, a significant elevation of renin reactivity (indicating a relative increase in circulating accelerators or a relative decrease in inhibitors of the renin reaction) was apparent in the plasma of coarcted dogs. Plasma renin concentration was elevated but to an insignificant degree in coarcted dogs, and renin substrate concentration was comparable with that of controls. The impaired renal perfusion and abnormal elevation of plasma renin activity during salt restriction is analogous to clinical and experimental observations in hypertensive states associated with total renal underperfusion and supports a major role for the renal pressor system in the pathogenesis of coarctation hypertension. The insignificant elevation of plasma renin concentration is not incompatible with this view. The demonstration of increased renin reactivity in coarctation hypertension provides additional evidence that acceleration of the renin reaction is common to all hypertensive states.

Hypertension due to renal artery stenosis in transplanted kidneys

Hypertension appeared to be related to stenosis of the hypogastricrenal artery system in 5 patients among 153 recipients of renal allografts. Renin assay and arteriography were crucial in the comprehensive evaluation of patients whose hypertension was not clearly related to rejection or excessive sodium intake. Hypereninemia was persistent in 4 of the 5 patients. Stenoses of the transplant renal arteries in three patients were caused by extensive intimal plaque formation. In one patient, periarterial fibrosis caused reduction of flow; 180 degrees torsion of the anastomosis resulted in stenosis in the fifth patient. Surgical correction is difficult and may be facilitated by a transabdominal approach. Vein bypass is probably preferable to patch angioplasty for intimal lesions. Following operation, hypertension was ameliorated and function improved in all patients. Rejection, which has been suggested as one of the causes of intimal plaque formation, ultimately led to the loss of the transplant in one patient. Function is normal in two patients; two patients have evidence of chronic rejection. No effort should be spared to evaluate this special group of patients whose transplant function can predictably be prolonged by decisive surgical management.