Identification and differentiation of surgically correctable hypertension due to primary aldosteronism

Review of surgical management of aldosterone secreting tumours of the adrenal cortex

AIMS

To evaluate the investigation and surgical management of primary hyperaldosteronism. Retrospective case note analysis of thirty-three patients who underwent adrenalectomy for primary hyperaldosteronism between 1982 and 2001 and a current relevant literature review.

METHODS

The records of twelve male and twenty-one female patients, age range 18 to 81 (mean 48 years) were reviewed. Eleven operations were performed by an open approach and twenty-two laparoscopically. Preoperative investigations included computed tomography (CT), magnetic resonance imaging (MRI), selective venous sampling and seleno-cholesterol isotope scanning, along with biochemical and hormonal assays. Twenty-six benign adenomas, three nodular hyperplastic lesions, one primary adrenal hyperplasia and three functional carcinomas were excised. Mean follow up was 12 months.

RESULTS

Patients had a mean blood pressure of 185/107 mmHg for 6.2 years mean duration. The mean severity of hypokalaemia was 2.7 mmol/l. Sensitivity of CT scanning was 85%, and of MRI 86%. Fifty percent of seleno-cholesterol scans were accurate. Mean operating time was 158 min for laparoscopic adrenalectomy whilst open surgery took 129 min (p=0.2, NS). Two cases commenced laparoscopically required open access for control of primary haemorrhage whilst one other bleed was managed via the operating ports. Mean postoperative stay was significantly shorter for the laparoscopic group (3 days compared with 7.9 days, p<0.0001). Thirty day mortality was zero. There were three infective complications in the open group (two chest, one wound) with no postoperative complications in the laparoscopic group. All patients were cured of hypokalaemia, whilst 62% cure of hypertension was achieved. Of those patients whose blood pressure was improved preoperatively by spironolactone 78% were cured by adrenalectomy. Adrenalectomy led to an overall reduction in the mean number of anti-hypertensive medications (2.3 drugs preoperative to 0.6 postoperative, p<0.0001). Of those not cured, 58% had improved blood pressure control requiring less medication on average (1.6 drugs compared with 2.6 drugs, p=0.08). Mean age of patients not cured by surgery was 55 years, whilst those cured was 44 years (p=0.03).

CONCLUSIONS

Primary hyperaldosteronism is a rare but important cause of hypertension. Selective venous sampling is a useful tool where investigations are inconclusive and fail to lateralise secretion. Patients with primary hyperaldosteronism enjoy lower complication rates and earlier discharge with the advent of laparoscopic surgery. Most patients will be cured of their hypertension and all of hypokalaemia. Laparoscopic adrenalectomy is now the accepted method of surgery for benign hyperaldosteronism. Those with bilateral disease due to idiopathic hyperaldosteronism (IHA) are not candidates for surgery and should be treated medically.

Primary aldosteronism: are we diagnosing and operating on too few patients?

Many cases of potentially curable primary aldosteronism are currently likely to be diagnosed as essential hypertension unless screening tests based on suppression of renin are carried out in all hypertensive patients. More than half of the patients with primary aldosteronism detected in this way have normal circulating potassium levels, so measurement of potassium is not enough to exclude primary aldosteronism. When primary aldosteronism is diagnosed, fewer than one-third of patients are suitable for surgery as initial treatment, but this still represents a significant percentage of hypertensive patients. After excluding glucocorticoid-suppressible primary aldosteronism, adrenal venous sampling is essential to detect unilateral production of aldosterone and diagnose angiotensin-responsive aldosterone-producing adenoma. One cannot rely on the computed tomography scan. If all hypertensive patients are screened for primary aldosteronism and the workup is continued methodically in those with a positive screening test, patients with unilateral overproduction of aldosterone who potentially can be cured surgically are not denied the possibility of cure.

Hormonal and humeral considerations in hypertensive disease

This article has discussed the classic hormonal causes of hypertension. Pheochromocytoma and hyperaldosteronism have been discussed, and a clinical approach to evaluation of patients for these problems has been presented. Other humeral factors that influence volume pressure homeostasis have been discussed. It is likely that pharmacologic agents affecting these other factors will become available to patients with hypertension in the future.

Primary aldosteronism. Results of surgical treatment

SUMMARY BACKGROUND DATA

Management of primary hyperaldosteronism has undergone dramatic changes in the past 40 years. This retrospective study was carried out to review our recent surgical experience and to identify potential factors associated with postoperative persistent hypertension.

METHODS

Forty-six patients who had adrenal surgery for primary hyperaldosteronism from 1983 to 1994 were included in the study.

RESULTS

Periodic paralysis occurred in 12 (26%) patients. Hypertension and hypokalemia (mean serum potassium, 2.2 + 0.5 [+ standard deviation (SD) mmol/L) were present in all patients. Postural study was diagnostic in 85% (23 of 27). Computed tomography scan correctly localized the tumor in all except 1 patient, and venous sampling was performed in 11 patients. There was no operative mortality, and complications developed in six patients (13%), including one patient requiring re-exploration for hemostasis. All patients had a histologically documented adenoma. During a mean follow-up of 51 months, 34 (77%) of the 44 patients required no further antihypertensive treatment. Two patients were lost to follow-up. Age, response to spironolactone treatment, and blood pressure on discharge were risk factors identified for persistent hypertension.

CONCLUSION

Primary hyperaldosteronism due to aldosterone-producing adenoma can be diagnosed and localized expeditiously, whereas surgical treatment can be performed safely. Hypokalemia may be cured by surgical treatment, although persistent hypertension, usually of a mild degree, still occurs in selected patients.

Clinical significance of associated nodular lesions of the adrenal in patients with aldosteronoma

Thirty-seven patients with primary aldosteronism were treated by unilateral total adrenalectomy during a 7-year period (1981-1987). The 37 patients were classified into 3 groups on the basis of adrenal pathology: unilateral solitary adenoma, 23 cases (group 1); unilateral adenomas, 3 cases (group 2); and adenoma with multiple macro- or microscopic nodules, 11 cases (group 3). The preoperative conditions of the patients (age, duration of hypertension, plasma renin activity, plasma aldosterone concentration, and serum potassium concentration), postoperative sequential changes of hormone levels, and outcome of hypertension were compared among the groups in order to determine whether the differences of adrenal pathology would affect the postoperative course. The preoperative parameters excluding age at surgery did not differ significantly among the 3 groups. The mean age in group 3, however, was slightly higher than in groups 1 and 2 (47.8 versus 42.8 versus 42.7 years). Postoperative hormonal changes were also similar, particularly in groups 1 and 3, staying within the normal range throughout the follow-up period (mean, 31 months; range, 3-86 months). However, postoperative improvement of hypertension showed marked differences, being significantly retarded in patients with multinodular lesions (group 3), about half of whom remained hypertensive even after 1 year. Nodular lesions other than adenoma(s) were, therefore, thought not to contribute to hormonal excess but to result from intractable hypertension.

Primary aldosteronism: diagnosis and treatment

The syndrome of primary aldosteronism produces few signs or symptoms. The diagnosis should be suspected when either spontaneous hypokalemia or easily provoked hypokalemia is found in a patient with hypertension. Hypokalemia in association with inappropriate kaliuresis, low plasma renin activity, and a high plasma aldosterone concentration/plasma renin activity ratio are the findings on initial screening tests that should suggest primary aldosteronism. The diagnosis must be confirmed by demonstrating nonsuppressible aldosterone excretion in conjunction with normal cortisol excretion. The choice of therapy is based on distinguishing unilateral from bilateral adrenal disease. With a unilateral adrenal adenoma, surgical removal reverses the hypokalemia and frequently cures the hypertension. In most patients with bilateral adrenal hyperplasia who are treated surgically, however, hypertension persists; thus, the initial treatment in these patients should be pharmacologic.

Scintigraphic studies in adrenal hypertension

Endocrine hypertension secondary to disorders of the adrenal glands is uncommon, but by no means rare. The importance of correct biochemical diagnosis and subsequent localization of the responsible lesion(s) lie in the fact that many of these syndromes occur in younger patients, may exhibit familial patterns of inheritance and are frequently amenable to surgical cure. The radiopharmaceuticals (131)1-6 beta-iodomethyl-19-norcholesterol (NP-59), a marker of adrenocortical cholesterol uptake, and (131)1- and (123)1-metaiodobenzylguanidine (MIBG), a norepinephrine (NE) analog and marker of energy-dependent NE storage vesicle accumulation, can be shown to accurately localize adrenal cortex and sympathoadrenal dysfunction, respectively. In Cushing's syndrome (CS) not only does the pattern of NP-59 uptake depict the adrenal dysfunction and its pathophysiologic basis, but the level of NP-59 accumulation reflects the degree of adrenocortical hyperfunction. Adrenocorticotrophin-independent CS is uniformly and accurately localized, especially in bilateral cortical nodular hyperplasia where even high resolution computed tomography (CT) may fail to depict the often subtle, asymmetric anatomic abnormalities. Dexamethasone suppression NP-59 adrenal scintigraphy has been shown to be highly sensitive and specific, and exceeds the efficacy of CT in the differentiation of adenoma and bilateral hyperplasia in primary aldosteronism. MIBG is useful as a sympathoadrenal imaging agent whose clinical utility has been demonstrated in the localization of pheochromocytoma, especially as a modality to screen the body for multiple and extraadrenal, recurrent, or metastatic lesions. Moreover, the extent of metastatic involvement from neuroblastoma can also be accurately depicted using MIBG. In this review we will examine the role of adrenal scintigraphy in the characterization of hypersecretory disorders of the adrenal cortex, medulla, and related conditions that produce hypertension as part of their symptom(s) complex. This approach, which is complementary to other anatomical modalities of imaging, can be used to advantage in the localization of functioning cortical and medulla adrenal diseases and other neoplasms of adrenergic origin.

Radiochemical diagnosis of adrenal disease

The adrenal gland consists of cortical and medullary components, both of which may be functionally imaged using radiopharmaceuticals designed to take advantage of the specialized physiology of each tissue. Radiolabeled cholesterol derivatives are taken up by normal and abnormal adrenal cortex and provide an in vitro map of adrenocortical function in Cushing's Syndrome, hyperaldosteronism, and hyperadrenogenism. Quantification of uptake shows strong correlation with biochemical parameters of adrenocortical hyperfunction. In the case of incidentally discovered euadrenal masses scintigraphy may help to distinguish between benign, nonfunctional cortical adenomas, and destructive, potentially malignant lesions. Radiolabeled metaiodobenzylguanidine (MIBG) is a tracer of type I uptake and intracellular storage capacity for catecholamines in sympathomedullary tissues and tumors derived from this system. This permits the location of pheochromocytomas of all types (benign and malignant, intra- and extra-adrenal, sporadic and familial) as well as neuroblastomas in all stages. Other neuroendocrine tumors with type I uptake capacity may also be imaged. In suitable cases preliminary data suggests the administration of large doses of MIBG may permit internal radiotherapy of otherwise untreatable neuroendocrine tumors.

Primary aldosteronism: changing concepts in diagnosis and management

Unilateral adrenalectomy for benign causes of primary aldosteronism is an established procedure. The established surgical cure for aldosterone-producing adenoma justifies a thorough preoperative evaluation. No single test accurately identifies aldosterone-producing adenomas in patients with primary aldosteronism. However, a useful algorithm combines postural studies, computerized axial tomography, and adrenal vein catheterization for selective hormonal assay, if computerized axial tomography is negative or equivocal and the suspicion of aldosterone-producing adenoma is high. If an adrenal mass is present and biochemical studies suggest a diagnosis of aldosterone-producing adenoma, resection of the affected gland from a limited unilateral approach is indicated. Cure can be expected in 80 percent of cases. In the uncommon circumstance that the adrenal tumor was not an aldosterone-producing adenoma but a hyperplastic nodule, these patients may still be cured or more easily controlled with antihypertensive medications. Thirty-eight patients who underwent unilateral adrenalectomy are presented and discussed.

Use of the saline infusion test to diagnose the cause of primary aldosteronism

Angiotensin II has a major effect on mineralocorticoid hormone synthesis in patients with idiopathic hyperaldosteronism; it has little or no effect in those with an aldosterone-producing adenoma. To determine if this difference could be of use in clinically separating these two forms of primary aldosteronism, saline infusion tests were performed in 20 patients--14 with surgically proved aldosterone-producing adenoma and six with idiopathic hyperaldosteronism. With the patients receiving a balanced diet containing 120 meq of sodium, 1,250 ml of isotonic saline was infused intravenously between 8 A.M. and 10 A.M. after overnight recumbency. Plasma samples were obtained immediately before and after the infusion. Plasma cortisol level decreased appropriately in both groups, but plasma renin concentration decreased only in those patients with idiopathic hyperaldosteronism (p less than 0.05). Aldosterone and 18-hydroxycorticosterone levels decreased in both groups. To account for the circadian variation in adrenocorticotropin levels during the course of saline infusion, 18-hydroxycorticosterone/cortisol and aldosterone/cortisol ratios were examined. Both ratios increased in every patient with aldosterone-producing adenoma (p less than 0.01 and p less than 0.001, respectively), but these ratios remained unchanged or decreased in the patients with idiopathic hyperaldosteronism. This divergent variation in ratios after saline infusion allows for the differentiation of patients with an aldosterone-producing adenoma from those with idiopathic hyperaldosteronism. In patients with primary aldosteronism, an 18-hydroxycorticosterone/cortisol ratio of less than 3.0 or an aldosterone/cortisol ratio of less than 2.2 after saline infusion is diagnostic of idiopathic hyperaldosteronism.

Malignant hypertension due to an aldosterone producing adrenal adenoma

Malignant hypertension in Conn's syndrome is rare. We report an 18 year old boy who presented with visual and renal impairment due to malignant hypertension which subsequently proved to be secondary to an aldosterone secreting adrenal adenoma. Diagnosis was delayed in this patient as plasma renin concentrations (PRC) were not invariably low and it is emphasized that suppression of PRC is not always a feature of primary hyperaldosteronism. The diagnosis of primary hyperaldosteronism is only excluded adequately by the demonstration of suppression of aldosterone secretion.

Scintigraphic localization of adrenal lesions in primary aldosteronism

Dexamethasone suppression adrenal cortical scintiscanning was performed in 87 patients with primary aldosteronism. Fifty patients had adrenal cortical adenomas and 37 had bilateral adrenal hyperplasia. The diagnosis of adrenal cortical adenoma was confirmed by surgery in 49 of 50, and bilateral adrenal hyperplasia was confirmed by adrenal vein aldosterone sampling in 33 and at operation in four. Dexamethasone suppression adrenal scintigraphy correctly identified the lesion(s) in 82 of the 87 patients. There were three false-negative and two false-positive adrenal cortical scintiscanning results. Computed tomography was performed in 33 patients and correctly identified 14 of 23 patients with adrenal cortical adenomas and two of 10 patients with bilateral adrenal hyperplasia and bilateral enlarged adrenals, whereas the remaining eight were considered to have normal findings. These data indicate that, when properly performed, adrenal cortical scintigraphy is an accurate and efficacious modality for the localization of adrenal cortical adenomas and in the differentiation of adrenal cortical adenoma from bilateral adrenal hyperplasia in primary aldosteronism.

Idiopathic hyperaldosteronism. A possible role for aldosterone-stimulating factor

To test the hypothesis that idiopathic hyperaldosteronism is secondary to increased adrenal stimulation by aldosterone-stimulating factor, we measured the latter in seven patients with idiopathic hyperaldosteronism and in four patients who had undergone surgical removal of an aldosterone-producing adenoma. In the patients with hyperaldosteronism, plasma aldosterone concentrations (mean +/- 1 S.E.) were 38 +/- 10 and 78 +/- 19 ng per deciliter in the supine and upright position, respectively (P less than 0.01). Supine plasma aldosterone-stimulating factor was 81 +/- 5 ng per deciliter in 15 normal subjects and 185 +/- 10 (P less than 0.01) in the patients with idiopathic hyperaldosteronism. After removal of an aldosterone-producing adenoma, plasma aldosterone-stimulating factor was normal. The supine value in each patient with idiopathic hyperaldosteronism was above the normal range (61 to 91 ng per deciliter) and increased to 290 +/- 59 ng per deciliter after four hours of upright posture. Twenty-four hour urinary excretion of aldosterone-stimulating factor was 424 +/- 35 ng (normal, 145 +/- 3; P less than 0.01) by affinity chromatography and high-pressure liquid chromatography, and it was not suppressed after two days of treatment with dexamethasone (0.5 mg orally every six hours). At the end of 48 hours, plasma concentrations were 248 +/- 40 ng per deciliter. Plasma cortisol and ACTH concentrations were under 2 micrograms per deciliter and under 40 pg per milliliter, respectively. We conclude that increased secretion of aldosterone-stimulating factor may be the cause of idiopathic hyperaldosteronism.

Use of an intravenous sodium load in screening for primary hyperaldosteronism

A sodium loading test was performed in 35 patients presenting with hypertension and hypokalemia. In 14 of these patients, intravenous administration of 0.9% saline (2 l in 4 h) on two consecutive days caused urinary aldosterone excretion to fall to values within the range for normal volunteers. The other 21 patients, in whom urinary aldosterone excretion did not decline following two days of saline loading, or in whom pronounced hypokalemia after the first day of loading precluded further saline infusion, were designated as having primary aldosteronism. Seventeen of this group underwent surgery and discrete adrenal adenomas were found in 16. When serum potassium concentration, plasma renin activity or the relationships of serum potassium to concurrent urinary potassium excretion or of urinary aldosterone excretion to plasma renin activity were used as alternative diagnostic criteria for primary aldosteronism, overlapping of the two groups occurred. It is concluded that measurement of urinary aldosterone excretion after intravenous sodium loading is a useful test in the test in the identification of primary aldosteronism due to aldosterone-producing adenoma. In this series the saline loading test was more specific in diagnosis than criteria based on serum and urinary potassium, plasma renin activity or unsuppressed aldosterone excretion.

Unilateral hypersecretion of aldosterone associated with adrenal hyperplasia as a cause of primary aldosteronism

In 3 patients with longstanding hypertension and spontaneous or diuretic-induced hypokalemia, the diagnosis of primary aldosteronism was established by the dual criteria of non-suppressible plasma aldosterone level and suppressed plasma renin activity. Preoperative studies of the etiology for the hyperaldosteronism using the postural plasma aldosterone test and adrenal venous steroid measurements gave conflicting results. On the basis of the differential adrenal venous steroid content, which suggested an unilateral adrenal source for the aldosterone hypersecretion, presumed to be adrenal adenoma, each patient was operated upon. In each case the excised adrenal revealed adenomatous or macronodular hyperplasia. Reinvestigation of the patients 3 to 12 months after the adrenalectomy showed that the dynamics of the renin-aldosterone axis was now restored to the normal state even though the patients remained hypertensive. These findings indicate that unilateral hypersecretion of aldosterone associated with adrenal hyperplasia can occur in some patients with primary aldosteronism simulating that due to an aldosteronoma. Such observations also raise questions about the pathogenesis of the adrenal hyperplasia and seem to add further complexity to the evaluation of patients with hyperaldosteronism.