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The adrenal glands 415
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Decreased function
Hypoadrenalism is most commonly a sequel of
prolonged corticosteroid therapy, in which endogenous
steroid production is suppressed, followed by abrupt
steroid withdrawal. It may also be due to the following:
•
Congenital adrenal hypoplasia.
•
Autoimmune destruction: Addison’s disease.
• Adrenal infarction: a rare consequence of stress or
sepsis (notably, meningococcal sepsis).
Bilateral adrenalectomy: intentionally (to treat
•
Cushing’s syndrome) or secondary to bilateral
nephrectomy.
Adrenal infiltration by secondary tumours from
•
primaries in bronchus and breast.
•
Bilateral tuberculosis of the adrenals.
1
Enzyme disorders
Congenital adrenal hyperplasia, the collective
description for the adrenal hyperplasias resulting
from increased ACTH secretion, may result from certain enzyme disorders. ACTH is produced in excess
because glucocorticoids, the end point in the pathway
of steroid hormone synthesis, are not produced as a
result of one of many possible enzyme deficiencies.
Instead, all the substrate synthesized is turned into an
intermediate hormone, such as an androgen.
Cushing’s syndrome
Cushing’s syndrome2 is produced by increased circulating corticosteroids. Excepting therapeutic exogenous
steroid administration, the majority of cases result
from a pituitary adenoma producing ACTH, resulting
in hyperplasia of the adrenal cortex (the disease that
Cushing first described); 10 to 20% are due to benign
or malignant adrenocortical tumours and another 10
to 15% are due to ectopic ACTH production by a distant tumour, such as carcinoma of the bronchus.
Cushing’s syndrome due to bilateral macronodular
adrenal hyperplasia is very rare.
1
omas Addison (1773–1860), Physician, Guy’s Hospital,
London.
2
Harvey Cushing (1869–1939), Professor of Surgery, Harvard
Medical School, Boston, MA, USA. He was one of the
founders of neurosurgery.
Clinical features
The syndrome usually affects young adults (occasionally, children), women more often than men. The
nature and relative severity of symptoms depend on
the degree and duration of hypercortisolism; when
the latter is severe, the appearance is characteristic:
adiposity with central distribution, abdominal striae,
a red moon face and diabetes. There may be osteoporosis, leading to vertebral collapse, hypertension, with
increased cardiovascular risk, and thromboembolic
events. Associated androgenic corticoid oversecretion
occurs only in females with adrenal cancer or with
driven stimulation (the adrenal gland is the
ACTHmajor source of androgen production in females
whereas it is the testes in males) and can produce varying degrees of hirsutism, acne and oligomenorrhea.
Most adrenal adenomas secrete only glucocorticoids.
Special investigations
These may be thought of as investigations to confirm
the diagnosis, and investigations to identify the cause.
The diagnosis is usually established when at least two
different first line tests are abnormal:
• Urinary 24- h cortisol level: a level above three times
the upper limit of normal is considered positive.
•
Late night salivary cortisol level: the normal evening
nadir is lost in patients with Cushing’s syndrome.
This test in nonformed on two or more separate occasions to
increase accuracy (the levels of cortisol in
Cushing’s may be variable).
•
Late night serum cortisol: similar principle to the
salivary cortisol test, but less convenient; hence it
is not used routinely.
• Dexamethasone suppression test (DST), in which
the steroid dexamethasone is administered. The
overnight low- dose DST (1 mg dexamethasone
orally between 11 pm and midnight followed by
serum cortisol measurement at 8 am the next
morning) is commonly used as a screening test to
differentiate patients who have Cushing’s syndrome from those that do not. As an alternative
test, or when the overnight test is equivocal, a twoday low- dose DST can be performed (total of 4mg
dexamethasone).
Careful interpretation of the tests is required
and physiological causes of hypercortisolism may
need to be excluded (e.g. obesity, pregnancy, and
invasive and can easily be per-
416 The adrenal glands
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physical or psychological stress). After establishing the presence of hypercortisolism, further
investigations can help determine the cause:
•
Plasma ACTH is usually performed on two sepa-
rate days. ACTH is raised in the presence of ectopic
or pituitary ACTHsuppressed in ACTHcan be normal in cyclic or mild hypercortisolism).
Abdominal computed tomography (CT) and magnetic
•
resonance (MR) scans are the best imaging modalities
for localization of a tumour in the adrenal gland.
Pituitary MR can also detect corticotroph adenomas.
driven disease; its secretion is
independent disease (ACTH
Treatment
ACTH- independent Cushing’s
syndrome
In cases of ACTH- independent Cushing’s syndrome
due to bilateral adrenal hyperplasia, bilateral adrenalectomy is performed and the patient placed on
glucocorticoid replacement. Removal of the affected
adrenal gland is carried out in cases of adenoma or
carcinoma. Prolonged hypercorticolism will result in
suppression of the contralateral adrenal which may
necessitate glucocorticoid replacement, often for several months post- surgery.
ACTH- dependent Cushing’s disease
Cases due to basophil adenoma of the pituitary (the
disease Cushing described) can be treated with transsphenoidal adenomectomy, when a clear adenoma
can be identified at surgery, or with subtotal resection
of the anterior pituitary (anterior hypophysectomy).
Medical therapy with adrenal enzyme inhibitors,
pituitary irradiation and bilateral adrenalectomy are
further treatment options, especially when surgery is
unsuccessful or contra-
indicated.
Primary hyperaldosteronism (Conn’s syndrome)
Once considered to be rare, it is now acknowledged that
the prevalence of Conn’s syndrome
and the condition often underdiagnosed. The aetiology
3
Jerome Conn (1907–1994), Physician, University of
Michigan, Ann Arbor, MI, USA.
3
is much higher
most commonly involves an aldosterone- secreting
adenoma or bilateral hyperplasia of the adrenal cortex.
Unilateral adrenal hyperplasia and familial hyperaldosteronism are relatively rare. Characteristically, there is
unexplained hypokalaemia (which may result in
episodes of muscle weakness or paralysis), metabolic
alkalosis and hypertension. However, most patients are
normokalaemic. Drugand hypertension presenting at a young age should
raise suspicion of primary aldosteronism.
The condition is interesting because aldosteroneproducing adenomas represent a curable cause of
hypertension.
resistant or severe hypertension
Special investigations
• Serum electrolytes: hypernatraemia and hypo-
ka laemia.
• Plasma aldosterone concentration (PAC) and
plasma renin concentration (PRC) or activity
(PRA): High PAC (typically, >555 pmol/L) and
undetectable PRC establish the diagnosis, especially
in the presence of spontaneous hypokalaemia.
Otherwise, aldosterone suppression testing is
required (e.g. with administration of intravenous
sodium chloride and measurement of PAC).
Interfering drugs, such as mineralocorticoid
receptor antagonists and angiotensin- converting
enzyme inhibitors, may have to be discontinued.
Once the diagnosis of Conn’s syndrome is established, it is important to determine whether this is
due to a unilateral adrenal adenoma or bilateral
hyperplasia. Most commonly, this involves:
•
Abdominal CT: this may show a solitary unilateral
adenoma or bilateral adrenal thickening or
micronodules.
•
Selective adrenal vein sampling: this can confirm
the presence of unilateral disease and lateralize
the side of the tumour. It is particularly important
when surgery is considered and in cases where the
adenoma is less than 1cm (when it may be missed
by CT) or both adrenals are abnormal (e.g. bilateral adrenal nodularity but unilateral source of
excess aldosterone). A PAC/cortisol ratio between
abnormal and normal side of >4:1 often indicates
unilateral excess aldosterone production (cortisol
corrected aldosterone ratio).
Metomidate positron emission tomography (PET)
•
CT: increased tracer avidity at the site of an adrenal
nodule may help lateralize the disease. Although
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not fully established in clinical practice, this investigation may be particularly helpful in cases of inconclusive adrenal vein sampling results, especially in
the presence of bilateral adrenal nodularity.
Treatment
Laparoscopic adrenalectomy has become the standard procedure for unilateral lesions; it has the advantage of lower morbidity and a shorter hospital
stay than the traditional open procedure. Medical
treatment is the usual standard of care for bilateral
BIOSYNTHESIS OF ADRENOCORTICAL HORMONES
ACTH
Cholesterol
Cholesterol desmolase
Pregnenolone
+
17α-hydroxylase
17-Hydroxypregnenolone
adrenal hyperplasia, with mineralocorticoid receptor
antagonists being the first line.
The adrenogenital
syndromes (Figure42.1)
These rare syndromes result from the hypersecretion
of adrenocortical androgens, due either to a defect
in the enzyme pathway of steroid production,
17,20-lyase
Dehydroepiandrosterone
3β-hydroxysteroid
dehydrogenase
Progesterone
21β-hydroxylase
11-Deoxycorticosterone (DOC)
11β-hydroxylase
Corticosterone
aldosterone synthase
Aldosterone
Mineralocorticoids Glucocorticoids Androgens
17α-hydroxylase
+
Angiotensin II
Figure42.1 Adrenocortical steroid synthesis
3β-hydroxysteroid
dehydrogenase
17-Hydroxyprogesterone
21β-hydroxylase
11-Deoxycortisol
11β-hydroxylase
Cortisol
17,20-lyase
3β-hydroxysteroid
dehydrogenase
Androstenedione
Testosterone
17β-estradiol
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commonly 21- hydroxylase deficiency (the congenital
form), or to an autonomous tumour producing
androgens (the acquired form).
Congenital adrenogenital
syndrome
Also known as congenital adrenal hyperplasia, this is
due to an inborn defect of normal steroid synthesis
(especially, hydrocortisone) by the adrenal cortex.
Excessive ACTH production by the pituitary then
occurs with resulting hyperplasia of the cortex and
hypersecretion of cortical androgens.
Acquired adrenogenital syndrome
In children, it is always due to an adrenocortical
tumour, which is usually malignant. In young adults,
the condition may be caused either by a tumour or by
cortical hyperplasia in cases of Cushing’s syndrome,
in which androgen production is excessive.
Clinical features
These are conveniently divided into three varieties
depending on age of onset.
Infancy
In the congenital variety of the adrenogenital
syndrome, the newborn female child has a large
clitoris and is often mistaken for a male (female
pseudohermaphrodite). Growth is initially rapid,
but the epiphyses fuse early so that the final result is
stunted growth. There may be episodes of acute
adrenocortical insufficiency, especially with stress
or infection.
Childhood
Differential diagnosis
The diagnosis is based on detecting the excessive
amount of steroid precursors, such as 17α-
hydroxyprogesterone, which is raised in the most
common congenital form, 21-
Differentiation must be made from the masculinizing tumour of ovary, in which the 17urinary excretion is normal, and also the common
condition of simple hirsutism in women.
hydroxylase deficiency.
ketosteroid
Treatment
Bilateral cortical hyperplasia in infancy is treated by
suppressing the excess ACTH secretion with exogenous steroids (e.g. hydrocortisone); on this regimen
the virilizing features clear and growth progresses normally. In the acquired variety, when a tumour is present
it can be removed by laparoscopic adrenalectomy, and
hyperplasia can be treated by bilateral adrenalectomy
with hydrocortisone maintenance treatment.
Non- functioning tumours
ofthe adrenal cortex
Small non- secreting adenomas of the adrenal cortex are
common postmortem findings of no significance; they
are increasingly detected by modern crossimaging techniques such as CT and MR (see later in this
chapter). Lesions less than 4cm in diameter with benign
characteristics on imaging studies, which are proven to
be non- secreting and which do not change on repeated
imaging over a 6- month interval can be safely left in situ.
Adrenal cysts and myelolipomas are relatively uncommon and usually are easily characterized on crosssectional imaging. Myelolipomas may grow over time
and cause local mass- effect symptoms; surgery can be
considered when they exceed 6cm in diameter.
sectional
Virilization occurs in the female child and precocious
sexual development, particularly of the penis, in the
male child.
Adults
Amenorrhoea, hirsutism and breast atrophy in
women, often associated with other features of
Cushing’s syndrome. In men, feminization is seen,
but this is extremely rare.
Adrenocortical
carcinoma
Carcinomas of the adrenal cortex are rare with an incidence of one to two per million population per year.
They are highly malignant and most cases are sporadic.
Most patients present with clinical symptoms related
to hormone excess, commonly Cushing’s syndrome
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and less frequently with virilization syndrome or
hyperaldosteronism. Nonsent with abdominal or flank pain and/or constitutional symptoms, such as anorexia and weight loss.
functioning tumours pre-
Special investigations
• Hormonal evaluation: carcinomas secrete large
amounts of adrenal steroid precursors. Urine steroid
profiling of metabolites of glucocorticoid, androgen,
and aldosterone steroids and their precursors is a
valuable diagnostic tool that can help differentiate
benign (e.g. lipid- poor adenomas) and secondary
(e.g. metastases or lymphoma) from malignant
tumours and can serve as tumour markers.
CT and MRI are both used for diagnostic evaluation
•
and to plan surgery (e.g. evidence of local invasion).
FDG-
PET CT scanning is used to stage the disease.
• Fine- needle aspiration biopsy should not be per-
formed when adrenal cancer is suspected as it is
poor at differentiating benign from malignant adrenocortical tumours and can lead to needle track
seeding.
Treatment
The only potential curative option is complete surgical
resection that often has to include en bloc removal of
involved organs. Tumour stage and resection margin
status are the most important prognostic factors.
most common malignant tumour in neonates and
infants under 1 year old. It may be bilateral, and up to
80% are associated with chromosomal abnormalities.
Macroscopically, it varies from a small nodular tumour
to a large retroperitoneal mass, containing areas of
haemorrhage and necrosis. Microscopically, it arises
from neuroblasts of the adrenal medulla, or within any
cells of neuroectodermal origin along the spine.
Neuroblastomas are clinically diverse and their
behaviour can range from spontaneous regression, to
maturation to a ganglioneuroma, to aggressive disease.
They can invade adjacent tissues and spread to regional
nodes and by the blood to bones and the liver.
Special investigations
• CT, MR, ultrasound and bone scan are all used to
stage the disease.
Treatment
A combined approach with surgical removal of local
disease together with chemotherapy and/or radiotherapy is necessary.
Prognosis
Early disease, localized to the area of origin and in the
absence of distant or lymph node spread, carries a
favourable prognosis, as do absence of chromosome
abnormalities, and age under one year together with
histologically well- differentiated tumour.
Adrenomedullary
tumours
Classication
Primary
• Neuroblastoma.
•
Phaeochromocytoma.
• Ganglioneuroma.
Secondary (metastasis)
A common site, especially from breast and bronchus.
Neuroblastoma
A highly heterogeneous tumour of sympathetic cells
occurring in children under the age of 5 years, and the
Phaeochromocytoma
andparaganglioma (PPGL)
A physiologically active tumour of chromaffin cells,
which secretes adrenaline and noradrenaline in varying proportions. Ten per cent are malignant and 10%
are multiple; 10% arise outside the adrenal gland (the
‘10% tumour’) from the sympathetic or parasympathetic ganglia from the skull base to the pelvis or the
organ of Zuckerkandl
(paragangliomas). Until recently, it had been thought
that 10% of cases are familial, however, molecular
genetics studies have now shown that around 40% of
4
Emil Zuckerkandl (1849–1910), Professor of Anatomy in
Graz, and later Vienna, Austria. e organ he described is
important in the regulation of blood pressure in early foetal
life, but regresses in the third trimester. It is composed of
cells of neural crest origin and its remnant typically lies near
the aortic bifurcation or inferior mesenteric artery.
4
near the aortic bifurcation
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patients harbour a germline mutation in an inherited
PPGL gene.
Any age may be affected, but the tumour is most
common in the fourth to fifth decade. The sexes are
equally affected.
Clinical features
These are produced by excess circulating adrenaline
and noradrenaline.
There is hypertension, which is paroxysmal or sustained, and which may be accompanied by palpitations, headache, blurred vision, fits, papilloedema
and episodes of pallor, sweating and anxiety. There
may be hyperglycaemia with glycosuria. Attacks may
be infrequent, or occur several times a day.
The diagnostic triad, with high specificity and sensitivity, is as follows:
Headache, sudden in onset, and pounding.
•
• Tachycardia and/or palpitations.
• Sweating.
Familial cases can be multifocal. The tumour may coexist with neurofibromas and café- au- lait spots (neurofibromatosis type 1, NF1), medullary carcinoma of
the thyroid or a parathyroid adenoma as part of a
multiple endocrine neoplasia (MEN2) syndrome and
von Hippel–Lindau disease (see Chapter 38).
Germline mutations in the various succinate dehydrogenase subunit genes (SDHX) are relatively common but mutations in multiple other genes have been
described.
Special investigations
Identifying thepresence ofa
phaeochromocytoma
• Fluorodeoxyglucose (FDG) PET scan: this is the
imaging modality of choice in patients with
suspected metastatic disease and has largely superseded the meta- iodobenzylguanidine (
iodobenzylguanidine]) scan, although this
[meta-
is still useful in patients considered for MIBG therapy). A
more sensitive than other imaging modalities for
detection of metastatic disease.
68
Gallium (Ga- 68)- dotatate PET scan is
Treatment
Surgical excision is performed, usually laparoscopically
but larger tumours may require an open operation.
Prior to surgery, the patient receives αblockade (e.g. phenoxybenzamine or alternatively doxazosin) to negate the hypertensive effects of catecholamines, which are released as a consequence of
manipulation of the tumour during the operation. Betablockade (e.g. propranolol) is not routinely required
unless significant tachycardia is noted in a euvolaemic
patient (no significant postural blood pressure drop).
The catecholamines produced by phaeochromo
cytomas cause marked vasoconstriction; hence,
patients with phaeochromocytomas are relatively
volume depleted. Immediately after removal of the
tumour, the blood pressure may fall to very low levels;
this is countered by volume replacement, although a
vasopressor infusion is sometimes required.
Histological examination cannot differentiate
benign from malignant PPGL. Patients who are less
than 60 years old or any patients with extra- adrenal or
metastatic disease should be referred for genetic testing. Patients should be followed up for a minimum of
10 years or sometimes for life (e.g. familial cases).
Surveillance is based on plasma or urinary metanephrine testing and/or cross- sectional imaging.
131
I- MIBG
adrenergic
-
• Plasma metanephrines: measurement of plasma
metanephrine and nor- metanephrine is a useful
first line test. Specificity and sensitivity depend on
upper cut- off limits used in the assay (specificity
can reach 100%). Some medications are implicated in false positive results (e.g. beta- and alphablockers, tricyclic antidepressants, caffeine, SSRIs).
• Twenty- four- hour urine metanephrines: highly
accurate, especially when the index of suspicion for
identifying catecholamine- secreting tumours is low.
Locating aphaeochromocytoma
• CT or MR may demonstrate the site and size of the
tumour.
Ganglioneuroma
A benign, slow- growing tumour of sympathetic ganglion cells, which only becomes clinically manifest if it
reaches a large size. Only about 15% arise in the adrenal;
the rest arise elsewhere along the sympathetic chain.
Adrenal ‘incidentaloma’
Adrenal masses are increasingly being recognized as
incidental findings on imaging performed for other
Incidental adrenal mass
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The adrenal glands 421
History and physical examination
(e.g. symptoms or signs suggestive of
hormonal hypersecretion, history of cancer)
Benign on imaging
Hormonal evaluation
Non-functional:Functional:
Endocrinology
assessment,
consider surgery
>4cm: consider surgery or
surveillance
<4cm: consider discharge
Differential diagnosis
Adrenocorttical cancer
Phaeochromocytoma
Lipid poor adenoma ,
Adrenal metastasis
Benign non-cortical tumour
(e.g. ganglioneuroma)
Dedicated adrenal imaging
Indeterminate on
Hormonal evaluation
Consider surgery
consider surveillance
Figure42.2 Scheme for investigation of incidental adrenal lesion on imaging.
indications. Their prevalence is increasing and is
higher among older adults. The majority are non-
A simplified algorithm for the assessment of adrenal
incidentalomas is shown in the above Figure42.2.
functional benign tumours but approximately 25%
represent functional tumours and/or primary or secondary adrenal malignancies. Assessment should
focus on establishing whether incidentalomas are
Hypertension
functional and whether they are malignant.
This section summarizes some surgical aspects of
Special investigations
• Hormonal evaluation: this should focus on testing
for phaeochromocytoma (plasma metanephrines), hyperaldosteronism if the patient is
hypertensive or has episodes of hypokalaemia
raised blood pressure.
Classication
• Primary (cause unknown).
• Secondary (causes at least partially understood).
(paired PAC and PRC, potassium level), and for
hypercortisolism (e.g. overnight low- dose DST). If
primary adrenal malignancy is suspected, a urinary steroid profile should be added.
•
Dedicated adrenal imaging (CT or MRI): a low
attenuation, homogeneous adrenal mass on noncontrast CT (<10 Hounsfield Units, HU) is very
likely to be an adrenal adenoma. Over 10 HU on
unenhanced attenuation and delayed contrast
washout on contrast enhanced CT (<60% absolute
washout or <40% relative washout) indicate an
indeterminate adrenal mass.
Primary hypertension
Primary hypertension is a disease of middle- aged and
elderly patients, which tends to run in families. It is a
very common condition and may be compatible with
few symptoms and a long life. There is an increase in
the peripheral resistance due to arteriolar thickening
or spasm but, as arteriolar thickening is a conse-
quence of hypertension, the argument as to which is
the primary factor has not been resolved in this
disease.
imaging
Consider FDG PET CT
Avoid biopsy (unless
metastasis suspected)
If no surgery,
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The kidney may be an important contributor to the
hypertension when its blood supply is impaired
owing to arteriolar narrowing. There is a vicious circle
of arteriolar spasm, arteriolar thickening, renal
ischaemia and further hypertension, which leads to a
progressive increase in the severity of this condition.
Secondary hypertension
This should be suspected mainly in patients with
resistant hypertension, young patients (e.g.
drugunder 30 years), hypertension associated with electrolyte abnormalities and patients with malignant
hypertension. It may be due to the following factors:
Renal disease.
1
2 Coarctation of the aorta (see Chapter13).
3 Endocrine causes:
Phaeochromocytoma (see earlier in this
a
chapter).
Cushing’s syndrome (see earlier in this chapter).
b
c Conn’s syndrome (see earlier in this chapter).
4
Raised intracranial pressure (see Chapter17).
5 Toxaemia of pregnancy.
6 Obstructive sleep apnoea.
(and thus hypertension) and acts on the adrenal
cortex to release aldosterone (which causes sodium
retention). The features of hypertension are thus set
in motion. This renin mechanism is protective as far
as the kidney is concerned and is one method by
which the kidney maintains its circulation. How
important renin is in the maintenance of normal
blood pressure has not been established. All forms of
renal parenchymal disease are likely to produce
hypertension. Especially common are chronic
glomerulonephritis and chronic pyelonephritis.
ACE inhibitors, such as captopril, are effective at
reducing blood pressure in patients with renal disease. However, when renal insufficiency is due to
renal artery stenosis, their use will exacerbate the
impaired perfusion and may result in deterioration in
renal function.
Unilateral renal diseases
producing hypertension
These are of particular surgical importance, as they
may sometimes be amenable to curative treatment
either by nephrectomy or by reconstructive procedures on the kidney or on its blood supply.
Renovascular
hypertension
Mechanism of renal hypertension
(Figure42.3)
Ever since the experiments of Goldblatt,5 it has been
known that impairment of blood perfusion to the kidneys can result in hypertension which, if the renal
perfusion remains impaired, may become permanent, owing to the vicious circle that has already been
mentioned. The mechanism of renal hypertension
appears to be the release of the hormone renin from
the juxtaglomerular cells in the renal cortex. Renin
acts on the serum protein angiotensinogen to give rise
to a physiologically inactive decapeptide, angiotensin I.
Angiotensin I is then converted to the octapeptide
angiotensin II by the action of angiotensinenzyme (ACE). Angiotensin II is a potent vasoconstrictor and causes an increase in peripheral resistance
5
Harry Goldblatt (1891–1977), Professor of Experimental
Pathology, University of Southern California, Los Angeles,
California.
converting
Unilateral pyelonephritis
Rarely, pyelonephritis may affect one kidney only,
especially if this kidney has been the site of previous trauma or of congenital malformation, if the
ureter on that side has been blocked or if there is
unilateral hydronephrosis. If the condition is diagnosed early, before the hypertension has reached
the chronic established stage and before hypertensive changes have taken place in the opposite
kidney, removal of the affected kidney may result
in a return to normal blood pressure. Presence of
a functioning contralateral kidney must be confirmed first.
Renal artery stenosis
This is a fairly common cause of secondary hypertension. It occurs in two age groups: the elderly (70%), in
whom the cause of the narrowing is atherosclerosis,
and young people, especially women, in whom the
cause appears to be the thickening of the intima
and media by hyperplasia of collagen and muscle–
fibro- muscular dysplasia.
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Angiotensinogen
Reduced
Vasoconstriction
Hypertension
Angiotensin III
Deactivated
blood
flow
Renin
from
juxtaglomerular cells
Angiotensin-converting
Proteases
Asp Arg
enzyme
Asp Arg
Circulating protein
Angiotensin I
Val Tyr Ile
HisPhe ProHisLeu
Angiotensin II
Val Tyr Ile
HisPhe Pro
Figure42.3 Mechanism of renal hypertension.
Special investigations
• Arteriography should be performed in young
patients, in whom fibromuscular dysplasia characteristically shows up as a string of beads in the
distal part of the renal artery and is bilateral.
• Duplex scanning may permit diagnosis of a significant stenosis.
• Renin estimation should be performed by selective renal vein catheterization. Renin concentration is at least 1.5 times higher on the affected side.
It is mostly informative in the presence of bilateral
renal artery stenosis where the test can help
lateralize the side that contributes most to the
hypertension.
Diethylene- triamine- penta- acetic acid (DTPA)
•
radionuclide scan will show renal blood flow
difference, especially if the patient has been given
an ACE inhibitor such as captopril to exaggerate
the condition. It helps determine the relative
function of each kidney when therapeutic
nephrectomy is considered.
Treatment
• Angioplasty with or without stent placement. In
suitable cases, a localized stenosis can be dilated
by a balloon angioplasty. This is particularly
successful in fibromuscular dysplasia.
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• Renal artery bypass. If the stenosis is fairly proximal and the distal vessels relatively healthy, it may
be possible to remove the stenotic portion of the
artery or bypass it, for example on the left side by
joining the splenic artery to the renal artery distal
to the blockage.
•
Autotransplantation of the kidney may be performed
after excising the stenosed portion of the artery.
Unilateral nephrectomy may be appropriate when
•
the small intrarenal branches of the renal artery are
also diseased or to remove a small atrophic kidney
with almost complete renal artery occlusion.
Other lesions of the renal arteries, for instance
aneurysm and congenital bands, may also result in
hypertension, which can be cured by unilateral
nephrectomy or direct arterial surgery.
It should be noted that, since the introduction of
effective antihypertensive drugs (in particular ACE
inhibitors), enthusiasm for surgery in unilateral renal
disease has waned, apart from patients in whom the
kidney’s function is grossly impaired.
Other unilateral renal diseases can cause hypertension, including hydronephrosis, tuberculosis of the
kidneys or tumours of the kidney; nephrectomy is
indicated in these conditions.
Additional resources
Case 109: A girl with hirsutes
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