notes by dr Claudio Italiano
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CT abdomen: the arrow indicates a voluminous abdominal aortic aneurysm |
The abdominal aorta is the most frequent site for the formation of aneurysms.
98% is located distally to the renal artery and most involve the terminal
portion of the aorta and often the origin of the common iliac arteries.
CT abdomen: the arrow indicates a voluminous aneurysm of the abdominal aorta
Since arteriosclerosis is the cause of almost all abdominal aortic aneurysms,
these tend to appear especially in the last decades of life, rarely before age
60 and usually between 70 and 80 years.
As for sex, there is a male relationship: female variable between 5: 1 and 9: 1.
Abdominal aneurysm tends to be a silent lesion until a rupture occurs.
Most are discovered incidentally, during a routine routine examination or
radiological investigations practiced for entirely different reasons.
Retrospectively, a history of mild symptoms can be obtained from about a third
of these patients by questioning them carefully.
These patients may report slight abdominal abdominal pain, back pain and
sometimes a sense of pulsation in the abdomen. If the patient complains of
significant pain in the back and abdomen, aneurysm rupture is usually imminent.
With careful palpation of the epigastrium, aortic pulsation can be highlighted
in most non-obese subjects.
When this pulsation becomes very strong and is associated with an expansive
mass, the diagnosis of aneurysm is generally obvious.
Although a retroperitoneal tumor can sometimes simulate an aneurysm by
transmitting the aortic wrist very intensely, this occurs rarely and perhaps
this symptom has been given too much importance.
In some patients, only a distinct pulsation is felt without a mass sensation
and it may be difficult to distinguish a generalized ectasia of the abdominal
aorta from a true aneurysm. If the aorta is deviated quite clearly towards the
right or left quadrant or if the aortic pulsation is well appreciated below the
navel, then the presence of the aneurysm can be considered very probable.
Approximately 50% of cases of aneurysm are accompanied by a short systolic noise, but this symptom is also found in the aorta and tortuous aorta.
If we consider that the rupture of an abdominal aortic aneurysm may be
responsible for death in 1 out of 250 subjects over the age of 50, it is evident
that the palpation of the abdominal aorta is one of the most important maneuvers
when examining subjects in average or advanced age.
The most useful test to confirm the diagnosis consists of an x-ray of the
abdomen in a lateral position taken with the techniques used for bone
radiography. Given the considerable calcification of the aortic wall, in this
way between 60% and 75% of abdominal aneurysms can be visualized.
By locating the posterior border along the lumbosacral column and also the
anterior wall, one can usually judge the size, location and extent of the
aneurysm with considerable accuracy. Aortography is not normally necessary to
make the diagnosis. In fact, the white plate often allows a better estimate of
the extension of the aneurysm than an aortography, since the wall clusters tend
to considerably decrease the size of the opaque lumen.
Sometimes aortography is necessary to determine if the aneurysm extends above
the renal arteries. Patients with abdominal aneurysm tend to be affected by a
generalized cardiovascular disease. In one series, 47% had a clear coronary
artery disease; 43% an obstruction of a peripheral artery; 8% a cerebrovascular
syndrome and 34% a hypertension.
However, the results of longitudinal studies conducted in patients with these
lesions are clearly in favor of aggressive treatment.
5-year survival from initial diagnosis in untreated patients ranges from 17.2 to
36.4%. About half of the deaths are due to rupture of the aneurysm. Several
researchers have shown that life is prolonged with aneurysmectomy. De Bakey and
Coll. reported that 72% of patients in whom resection was performed were still
alive three years after surgery and 58% after 5 years.
Szilagyi and Coll. they compared the progress of untreated patients and those
treated after excluding elderly patients, hypertensives and cardiopaths, and
found a doubling of survival in the group of operated patients. Mortality from
elective aneurysmectomy was significantly reduced.
De Bakey and Coll. they recorded an operating mortality rate of 9% in 1964; in
1966 a percentage of 4% was reported in a group of patients of whom 88% had
another cardiovascular disease. Arterial pressure, central venous pressure and
diuresis should be monitored very carefully during and after surgery.
Continuous electrocardiographic monitoring is advisable because often silent
arrhythmias and myocardial infarcts occur. In particular, the signs of acute
arterial occlusions at the level of the lower extremities must be sought.
Embolism from the aneurysm sac or an atheromatous plaque may occur during aortic
manipulation and sometimes embolectomy is required.
Although it is admitted by most that most patients, including those with
occlusive arteriopathy, must undergo an elective intervention, there are some
patients that it is preferable to exclude from the intervention.
An intervention on lesions extending above the renal arteries is quite
dangerous. Patients with severe angina, congestive heart failure or frequent
episodes of cerebral ischemia present a high risk because there is a higher rate
of surgical mortality and a relatively high chance of death from occlusive
disease before the breakdown of the aneurysm.
An aneurysm with a diameter of less than 5 cm rarely breaks before further
expansion and it is best to leave it in place if the patient has other signs of
cardiovascular disease. However, it should be remembered that an easily palpable
aneurysm usually has a diameter of more than 5 cm.
The rupture of an abdominal aortic aneurysm is usually fatal, but some patients
may be rescued if subjected to immediate and competent treatment. An initial
rupture may be temporarily buffered due to the formation of a thrombus in the
retroperitoneal area.
The patient may complain of a violent dorsal or abdominal pain and yes. a
hypotension may appear several hours before a bleeding occurs in the peritoneal
cavity.
The sudden appearance of pain in the back or abdomen in a patient with a
palpable aneurysm requires immediate laparotomy. In an obese person over the age
of 60, the association of severe pain and a state of shock must make one think
of the possibility of rupture of an aneurysm even if the palpation is completely
negative.
If there are no electrocardiographic signs of acute myocardial infarction,
immediate surgical exploration should be performed without waiting for the
results of radiological investigations.
As long as the patient's pressure remains above 60-70 mm Hg it is probably not
advisable to quickly restore the blood volume until the aortic clamping is
performed above the perforation site, as a high pressure of perfusion may result
in the displacement of the buffering thrombus.
Once the aorta is clamped, the prompt restoration of the actual blood volume is
essential, making a recourse as a guide to the trend of central venous pressure.
Mannitol is administered intravenously to cause diuresis and to protect the
patient from renal failure.
The arterial pH must be determined and the metabolic acidosis corrected with
sodium bicarbonate.
The postoperative course is often very complicated. Due to the increased
permeability of the inflamed mesentery and peritoneum, a significant amount of
liquids may be sequestered retroperitoneally during the first 24-36 hours. The
sudden decline in circulating blood volume can quickly lead to shock and
oliguria.
Arterial pressure, central venous pressure and urinary flow must be
continuously monitored, while blood volume is rapidly restored.
The appearance of acute renal failure may require dialytic treatment (preferably
hemodialysis) for several days. After the first 48 hours, the seized liquids
begin to be reabsorbed and the patient may experience congestive heart failure
and sudden pulmonary edema if there is underlying heart disease.
For this reason, a prophylactic digitalization after surgery is often
recommended. Adequate oxygenation is essential at all times. The patient may
need intermittent use of a respirator during the first few days, as the
extensive abdominal incision, the orthopedic position and the presence of a
shock lung syndrome can impair ventilation.
If the patient exceeds the first five days with a satisfactory cardiopulmonary
and renal situation, he will probably manage to recover, provided that a wound
dehiscence or a retroperitoneal infection does not occur.
Several other less frequent complications of abdominal aortic aneurysm deserve
mention. Due to the formation of large thrombi in the aneurysmal sac, peripheral
embolization may occur with acute occlusion of the femoropoplitis arteries or
small foot infarcts.
Interestingly, the remarkable prevalence of peripheral arteriopathies in
patients with abdominal aortic aneurysm is mainly due to femoropopliteal
occlusion rather than aortoiliac obstruction. Relapsing and silent emboli from
an aneurysm are likely to contribute to the occlusive process in the distal
site.
A rare complication of arteriosclerotic aneurysms is bacterial infection, which
occurs more frequently in abdominal aortic aneurysms.
Only 35 cases of secondary aneurysm infection have been reported, but the actual
incidence is perhaps higher. In an autoptic study, 6 of 178 arteriosclerotic
aortic aneurysms were infected.
Salmonella (35% of the cases), seguitedallo staphylococcus (12%), were the most
frequently found germs. Patients usually present with fever of unknown origin or
with a long-standing intractable sepsis. A break occurred in 79% of cases. In
these cases, an early surgical intervention is necessary after establishing an
adequate antibiotic treatment. Finally, some cases of haemorrhagic diathesis
secondary to a consumption coagulopathy have been reported in association with
abdominal aortic aneurysms.
Less severe forms may perhaps be highlighted in the future using the most
sophisticated tests to highlight fibrinogen degradation products.
To learn more:
Aocp
La rivascoralizzazione degli arti inferiori nelle arteriopatie periferiche: by-pass