abdominal aortic aneurysm
Introduction
Introduction to abdominal aortic aneurysm Abdominal aortic aneurysm (abdominalaneurysm) is a local or extensive permanent dilation or bulging due to the destruction of the arterial mid-layer structure and the inability of the arterial wall to withstand the pressure of blood flow impact. After the abdominal aortic aneurysm occurs, it can gradually increase, and finally rupture and hemorrhage, resulting in death of the patient. Abdominal aortic aneurysms mainly occur in the elderly over the age of 60, with a male to female ratio of 10:3. Often accompanied by hypertension and heart disease, but young people are also occasionally visible. More men than women. The occurrence of abdominal aortic aneurysm is mainly related to arteriosclerosis. Other rare causes are aortic dysplasia, syphilis, trauma, infection, arteritis, Marfan syndrome. The prevalence of abdominal aortic aneurysm accounts for 63%-79% of aortic aneurysms. Most abdominal aortic aneurysms are caused by atherosclerosis. They are usually located at the distal end of the renal artery and extend to the bifurcation of the abdominal aorta. The brachial artery, occasionally located above the renal artery, also known as the thoracic and abdominal aortic aneurysm, often invades the branches of the inferior mesenteric artery, and some patients may have no symptoms before the rupture and near rupture. basic knowledge The proportion of illness: 0.002% Susceptible people: no special people Mode of infection: non-infectious Complications: abdominal aortic aneurysm
Cause
Abdominal aortic aneurysm
Arteriosclerosis (20%):
Because abdominal aortic aneurysm and arteriosclerosis mainly occur in the elderly, and they often coexist, it has been considered that abdominal aortic aneurysm is the result of the evolution of arteriosclerosis, and is often described as "arteriosclerotic abdominal aortic aneurysm Studies have shown that atherosclerosis is related to the formation and expansion of aneurysms. The possible mechanisms are mainly the following three aspects. First, due to the lack of nourishing blood vessels, the nutritional supply of the abdominal aorta wall is mainly derived from the blood in the lumen. Dispersion, and the formation of arteriosclerotic plaque and its attached thrombus, will inevitably lead to dystrophic barrier, leading to necrosis of the intima of the arteries, weakening of the wall, easy formation of aneurysms, and secondly, after atherosclerotic plaques fall off Exposed smooth muscle cells activate collagenase, which degrades a large amount of collagen, which is one of the factors that cause the membrane in the aortic wall to be weak and easy to form tumors. In addition, in areas with low shear stress (such as above the aortic bifurcation) The blood flow is distorted, the hardening factor in the blood is prolonged in contact with the wall of the tube, and the hardened plaque and its attached wall thrombus make the two common iliac artery cavities at the bifurcation Stenosis, aortic wall so that the withstand pressure greater reflection, but also easy to induce the formation of aneurysms.
The results of Allardice et al. showed that the incidence of abdominal aortic aneurysm was significantly increased in patients with sclerotic performance in the leg and neck arteries, and Gaspar found that in the study of patients undergoing abdominal aortic aneurysm surgery, 44% of patients have atherosclerotic disease at the same time.
Although recent studies suggest that arteriosclerosis is likely to be a disease that coexists with abdominal aortic aneurysms and plays a role in its formation and progression, most studies and clinical data indicate that arteriosclerosis remains the abdominal aorta. The most common and most important cause of tumors.
Arterial structure changes (20%):
It is the weakening of the abdominal aortic wall, which is an indispensable local factor for the formation of abdominal aortic aneurysm. Firstly, compared with the aorta, the abdominal aortic wall is weak, and the number of elastin layers is significantly reduced, often lower than 40 layers. It is proved that when the aortic layer of the aorta is destroyed to below 40 layers, aneurysms are easily formed, and the half-life of elastin is 70 years, which coincides with the peak period of clinical aneurysm, and secondly, the abdominal aorta The nourishing blood vessels are less, and the nutrient supply of the membrane and the intima is mainly derived from the diffusion of blood in the lumen. When there is atherosclerotic plaque formation, it may lead to nutrient diffusion disorder, and even the intima, mesial necrosis, and wall changes. It is weak, once again, the repair ability of the abdominal aortic wall is weak, and smooth muscle cells play an important role in the repair of the damage of the blood vessel wall, and the cells need to synthesize collagen and elastin under the stimulation of pulse pressure shock, due to The stiffness of the abdominal aorta is larger, the shock pressure of the pulsed pressure on smooth muscle cells is reduced, and the synthetic power is decreased, coupled with the tumor expansion after angiogenesis. There are many smooth muscle cells replaced by fibrotic connective tissue, which reduces the synthesis of collagen and elastin. Quantitative analysis shows that elastic fibers account for 35% of the dry weight of the normal aorta, but only 8 in patients with aneurysms. %, existing animal models have demonstrated that intra-arterial infusion of elastase or laparotomy exposure of a segment of the abdominal aorta with elastase and destruction of elastin can lead to the formation of abdominal aortic aneurysm, also provided by Loosemore et al in 1988 The change in collagen protein and amount may be the basis for the formation of aneurysm. In this way, the matrix of the arterial wall is continuously inactivated and degraded, and at the same time, effective nutrition and timely supplementation and repair are not obtained, so that the arterial wall is continuously thinned. The intensity decreases, eventually leading to the appearance of an aneurysm.
The local load of the abdominal aorta increases, and it plays a non-negligible role in the formation of the aneurysm. In the aortic system, from the proximal end to the distal end, the compliance becomes smaller, and its congenital upper The narrow and narrow vertebra structure makes the pressure on the aortic wall gradually increase from the top to the bottom. In addition, the blood pressure pulse transmitted to the peripheral vascular artery is reflected and amplified in the abdominal aorta, and its size is determined by the aorta and bifurcation. The ratio of the posterior vessel diameter is the smallest when the sum of the diameters of the two common iliac arteries is 1.1 to 1.2 times the diameter of the abdominal aorta. As the age increases, the proportion gradually decreases, and at the age of 50, it has dropped to 0.75. Clinically, the incidence of abdominal aortic aneurysm below the renal artery is the highest, because in elderly patients often accompanied by arteriosclerotic disease, arteriosclerotic plaque and its wall thrombus, the two common iliac arteries at the bifurcation The caliber is narrower, so that the abdominal aorta segment below the level of the renal artery is subjected to greater reflex pressure, and the retention time of the local sclerosis factor is longer, so that the incidence of the aneurysm is significantly increased.
Genetic factors (10%):
Abdominal aortic aneurysm has a family-genetic tendency. Johnson and Koepsell compared the family history of 250 patients with abdominal aortic aneurysm and controls, and found that 19.2% of patients had a first-degree blood relationship with known aneurysms. In the control group, only 2.4%, the risk of disease increased by 11.6%, especially the siblings have greater risk. The abdominal aortic aneurysm is mainly the sex inheritance of the X chromosome, and autosomal dominant inheritance. The genetic defects of elastin and collagen directly cause the weakening of the aortic wall, and the genetic changes of various enzymes increase the inactivation and degradation of the matrix structure protein of the arterial wall, and the integration of the joints is destroyed. Indirectly leads to weakness of the arterial wall, such as the thoracic and abdominal aortic aneurysm that occurs in Marfan syndrome.
(1) Genetic variation related to elastin degradation: The genetic variation of elastin has not been confirmed in aneurysm patients. It is clear that the haptoglobin gene on the long arm of the 16th autosome is adjacent to its cholesterol. The variation of the ester transfer protein gene, in patients with abdominal aortic aneurysm, the frequency of expression of the globin 1 allele is significantly increased, resulting in increased synthesis of haptoglobin, which can promote the degradation of elastin by elastase, thereby affecting The integrity of the connective tissue of the arterial wall leads to the occurrence of an aneurysm, and the variation of the cholesterol ester transfer protein gene can affect lipid metabolism, causing a decrease in the concentration of high-density lipoprotein (HDL) in the blood of patients, and triglycerides, An increase in the concentration of low-density lipoprotein (LDL) leads to the appearance of arteriosclerosis, which indirectly promotes the formation and development of aneurysms.
Corresponding to the deletion of 1-AT (1 antitrypsinogen) gene expression, 1-AT is the main inhibitor of elastase, and the gene phenotype responsible for 1-AT is about 35% of the monozygous gene. The gene phenotype is not expressed in about 90% of patients with abdominal aortic aneurysm, so that the inhibition level of 1-AT is significantly decreased, the activity of elastase is significantly increased, a large amount of elastin is degraded, and the aortic wall becomes weak. Easy to develop and develop aneurysms.
(2) Gene mutations related to collagen and its metabolism: One or a single base of the type III collagen gene is mutated, and the glycine at position 619 is replaced by arginine, which can cause abnormal expression of type III collagen. Experiments have shown that this is related to the formation of abdominal aortic aneurysm, but since the gene mutation is personalized and not confirmed in the majority of patients, a recent study on genetic variation in 54 patients with abdominal aortic aneurysm suggests that Although the gene mutation of type III procollagen is only found in a small number of patients, the replacement of a single amino acid residue will cause profound geological changes in collagen, and this gene mutation plays an important role in the pathogenesis of abdominal aortic aneurysm.
The gene of collagenase inhibitor associated with collagen metabolism is located on the X chromosome. In patients with abdominal aortic aneurysm, the gene is deleted, the synthesis of collagen inhibitor is reduced, the level of collagenase inhibition is reduced, and finally the degradation of collagen is significantly increased. The arterial wall is weak and the aneurysm is formed.
In short, the inheritance of abdominal aortic aneurysm is a very complex multi-factor mechanism involving several different genes. It is precisely because of the synergistic effect of these genes that the occurrence and development of aneurysms.
Enzyme chemistry (10%):
(1) The role of elastase: The results of the study showed that the content and activity of elastase in the wall of patients with abdominal aortic aneurysm were higher than those of patients with aortic occlusion. Currently, neutrophil elastase (NE) and smooth muscle cell elastase (SME) The Kang E is also carried on the arterial wall at the same time. In addition, after the arteriosclerosis occurs, the smooth muscle cells of the arterial wall are stimulated to produce and secrete SME. The increase of these two types of elastase causes the degradation of elastin. The rate is abnormally increased, and its normal folded sieve-like structure is destroyed. It cannot provide sufficient elastic traction force in the longitudinal direction and the circumferential direction, thereby causing the artery to be distorted and deformed, further expanding into a tumor, and elastically connecting the tissue in the entire aortic wall. Lysis disruption lays the foundation for the formation of aneurysm. In addition to the genetic factors, the increase in elastase activity is also affected by many environmental factors. Studies have shown that smoking, trauma, hypertension, etc. can promote elastase. The activity increased by a factor of 2 on the original basis.
(2) The role of collagenase: Studies have shown that the concentration and activity of collagenase in the aortic wall of patients with abdominal aortic aneurysm increase, the possible mechanism is the loss of collagenase inhibitor gene expression, and when elastin is degraded, The balloon-like tumor formed by the arteries can also activate collagenase. Under the action of collagenase with increased concentration and activity, the normal structure of collagen is destroyed, the degradation is significantly increased, and the tensile strength of the arterial wall is significantly reduced. An aneurysm ruptures when the collagen reserve is depleted and cannot withstand the pressure load that is passed on by the inactivation of elastin.
(3) The role of metalloenzymes: In 1984, Tilson et al. found in the animal model of abdominal aortic aneurysm that the lack of copper metabolism in mice caused a decrease in the activity of a copper-containing metalloenzyme, dissolved oxidase. The enzyme plays an important role in the integration of collagen and elastin, suggesting that the lack of this enzyme will lead to weak aortic wall and easy aneurysm. In patients with Menkes syndrome, elastic tissue of the arterial wall is also found. Reduction and abnormalities in copper metabolism indicate that metalloenzyme abnormalities play a role in the pathogenesis of abdominal aortic aneurysm. In 1994, Karen et al. found that zinc-related matrices were found in patients with abdominal aortic aneurysms. The activities of the metalloproteinases MMP-3 and MMP-9 are increased. The enzyme is mainly responsible for the degradation of the matrix components in the blood vessel wall, and the destruction of the normal matrix component of the arterial wall will result in the weakening of the arterial wall and the formation of an aneurysm in severe cases.
Smoking (5%)
Twenty years ago, it was clear that smoking was closely related to abdominal aortic aneurysm. The incidence of abdominal aortic aneurysm increased with the increase of cigarette consumption, in addition to various toxic components in cigarette tar, tobacco When the gaseous substances produced during combustion are absorbed into the blood, the methionine can be oxidized to methionine sulfoxide, thereby inactivating 1-AT, increasing the activity of proteolytic enzymes, aggravating the degradation of aortic wall elastin, and causing aortic wall strength. The weakening, leading to the occurrence and development of aneurysms, statistics show that smokers die from aneurysm rupture 4 times more than non-smokers, and smoking sputum sputum is up to 14 times.
Inflammation (5%)
In 4% to 10% of patients with abdominal aortic aneurysm, it is found that it has a thick white tumor wall and is closely adhered to the surrounding. This is called "inflammatory abdominal aortic aneurysm", which is characterized by a large number of inflammatory cells. Infiltration, often spreading to the surrounding tissue outside the wall of the aorta, is currently considered to be an autoimmune reaction of the arterial wall component, the lipid oxidation product - waxy, exuded adjacent tissue.
Histological examination of the aortic wall of any aneurysm can be seen with varying degrees of inflammatory infiltration, and the extent of inflammatory infiltration of lymphocytes and histiocytes in the adventitia and media is associated with tenderness and enlargement of the palpation Arterial diameter-related, recent studies have shown that macrophages and activated T, B lymphocytes are involved in chronic inflammatory reactions, and TL-1B and TNF- secreted by macrophages play an important role in the process of inflammation, they can It stimulates the production of metalloproteinases and promotes the degradation of connective tissue, thereby weakening and destroying the middle layer of the aorta. Therefore, inflammation may also be one of the causes of abdominal aortic aneurysm.
Surgical trauma (5%)
It has been reported in the literature that 10 patients have a rupture of abdominal aortic aneurysm within 36 hours after exploratory laparotomy. It is likely that laparotomy has disrupted the dynamic balance between matrix protein connective tissue anabolism and catabolism. Risk factors for aneurysm rupture, studies have shown that surgical trauma such as intestinal resection, laparotomy, etc. can cause a significant increase in aortic elastase activity.
High blood pressure (5%)
Hypertension is also a risk factor for abdominal aortic aneurysm, which is associated with increased morbidity and increased risk of rupture. Recent studies of a mouse model of abdominal aortic aneurysm have shown that the presence of hypertension is an aneurysm. The basic conditions of formation, especially systolic hypertension, play an important role in the formation of aortic aneurysm. However, whether hypertension is involved in the formation of aneurysm or only promotes the expansion of the aortic wall that has been weakened has not yet reached a positive conclusion. .
Age (5%)
Abdominal aortic aneurysm is a senile disease. It is rare in people under the age of 50. Under normal circumstances, the structural changes of the arterial wall are accompanied by age. As the age increases, the elastin fibers of the arterial wall degrade, break and Calcification, the aging of the aortic wall can not resist the role of aortic aneurysm expansion factor, so the occurrence of aortic aneurysm in the elderly.
In summary, the occurrence and development of abdominal aortic aneurysm is the inevitable result of many long-term interactions between factors causing weak aortic wall and increasing its load. Degradation and inactivation of elastin will lead to the formation of abdominal aortic aneurysm. This is a key factor in tumorigenesis, and the depletion of collagen stores can cause irreversible, continuous aneurysm expansion, and even the final rupture, smoking, inflammation, trauma, advanced age, hypertension and other risk factors for abdominal aortic aneurysm. Occurrence and development have a promoting effect (Figure 1).
Pathogenesis
Abdominal aortic aneurysm wall is generally a single spherical or prismatic shape, and there are many cases. Histological examination shows that the aneurysm wall has elastic fiber breakage, elastin content is reduced; middle and outer membrane chronic inflammation, B lymphocytes and plasma cells are infiltrated, and Containing a large number of immunoglobulins, suggesting an autoimmune response, no matter which type of aneurysm has a disappearance of the intima and a break in the elastic layer, when the intra-arterial pressure exceeds the expansion limit of the arterial wall, the aneurysm will rupture, almost all the abdomen There are blood clots in the aneurysm cavity, blood clots can be mechanized and infected, blood clots can cause distal arterial embolization, B-mode ultrasound scan to follow abdominal aortic aneurysm, and the average diameter of the tumor is increased by 3.8mm per year. Traumatic aneurysms, infectious aneurysms and anastomotic pseudoaneurysms are para-aortic pulsating hematomas formed after rupture of the arterial wall, all of which are pseudoaneurysms.
Pathological type:
(1) Classification: According to the structure of the aneurysm wall, it can be divided into three categories:
1 true aneurysm: the structure of each layer of the tumor wall is complete, and the cause is mostly arteriosclerosis.
2 pseudoaneurysm: formed after arterial rupture, no complete arterial wall structure, the tumor wall is composed of part of arterial intima and fibrous tissue, blood flow in the tumor cavity through the arterial rupture and the real lumen of the arteries, clinically more common in Traumatic aneurysm.
3 dissection aneurysm: After the rupture of the intima of the artery, the arterial blood flows through the intima and the media of the artery, so that the arterial wall separates and bulges, and the endometrium of the distal end of the tumor can be broken, and the true cavity of the artery The same, double-cavity in the sandwich, can form a wall thrombus in the aneurysm, can be secondary infection, the tumor wall can be broken, causing serious bleeding and life-threatening.
(2) Classification: According to the different parts of the tumor invasion, abdominal aortic aneurysm can be divided into 2 types:
1 High abdominal aortic aneurysm above the level of renal artery opening, also known as thoracic and abdominal aortic aneurysm and suprarenal abdominal aortic aneurysm.
2 aneurysm is located below the level of renal artery opening, called abdominal aortic aneurysm or sub-renal abdominal aortic aneurysm, clinically more common in the lower level of the renal artery, abdominal aortic aneurysm above the radial artery, this type of aneurysm is near The distal end has a relatively normal arterial wall, which provides favorable conditions for surgical treatment.
Prevention
Abdominal aortic aneurysm prevention
The main cause of abdominal aortic aneurysm is arteriosclerosis. In order to prevent the occurrence of this disease, we must start from preventing arteriosclerosis; limit the intake of animal fat, limit the intake of high cholesterol foods, and stop smoking and alcohol to prevent arteriosclerosis. A certain benefit, once the abdominal aortic aneurysm is formed, it is necessary to strictly stop drinking, and at the same time limit activities, not to be active, avoiding irritability, to reduce the rupture of abdominal aortic aneurysm caused by external causes, in addition, taking enteric aspirin, double Drugs such as pyridoxol and pancreatic kallikrein prevent secondary thrombosis and improve lower limb ischemia.
Complication
Abdominal aortic aneurysm complications Complications abdominal aortic aneurysm
Common arterial embolism of the lower extremity, hydronephrosis caused by compression of the ureter and rupture of the abdominal aortic aneurysm, etc., the rupture of the abdominal aortic aneurysm is the main cause of sudden death, abdominal aorta and abdominal aorta Venous fistula is a rare complication, and the tumor occasionally sticks to adjacent intestinal ducts.
Symptom
Abdominal aortic aneurysm symptoms Common symptoms Relaxation heat pale pale abdominal mass Abdominal discomfort Dull pain Hypotension Nausea Abdominal pain Ascites Kidney area tenderness and cramps
1. Pain: Pain is a common clinical symptom of abdominal aortic aneurysm. About one-third of patients show pain. The location is mostly located in the umbilical circumference of the abdomen, two ribs or the waist. The nature of the pain can be dull pain, swelling. Pain, tingling or knife-like pain, it is generally believed that pain is an increase in the tension of the tumor wall, causing traction of the adventitia and posterior peritoneum, which is caused by compression of adjacent somatic nerves. When a large abdominal aortic aneurysm erodes the spine, It can also cause radiculopathy. It is worth noting that sudden severe abdominal pain is often a characteristic manifestation of ruptured abdominal aortic aneurysm or acute stenosis. The characteristics of pain caused by acute dilatation of abdominal aortic aneurysm are very similar to their rupture, and it is difficult to distinguish. The pain is persistent, it is a severe knife-like pain, and it is not relieved by the change of body position. It is only the pain that occurs when the abdominal aortic aneurysm is acutely dilated, and it is not accompanied by hypotension or shock. It is so important because of the pain. Therefore, sudden abdominal pain in abdominal aortic aneurysm is regarded as the most dangerous signal. Pain is closely related to surgical indications and is related to the mortality of surgery. The mortality rate of elective surgery for patients with non-ruptured abdominal aortic aneurysm is 4.9%, and the mortality rate is 26.5% in patients with pain and non-rupture. Especially in patients with pain and tenderness, the operative mortality rate can be as high as that of patients with simple abdominal pain. More than 2 times.
Because abdominal aortic aneurysm has a variety of pain manifestations and is not specific, it often leads to misdiagnosis and rapid deterioration of the disease. In a few cases, a patient with a controlled abdominal aortic aneurysm rupture (hematoma obstruction rupture, etc.) Due to a small amount of blood loss and reflex tachycardia, symptoms of angina may be associated with this, which must be well differentiated to prevent misdiagnosis.
2. Compression symptoms: With the continuous expansion of abdominal aortic aneurysm, it is possible to oppress adjacent organs and cause corresponding symptoms, which is more common in clinical practice.
(1) Intestinal compression symptoms: This is the most commonly compressed organ of abdominal aortic aneurysm. Due to the small activity of the duodenum, early symptoms may occur due to oppression, which may indicate abdominal discomfort, fullness, and loss of appetite. In severe cases, nausea, vomiting, cessation of bowel movements, and other symptoms such as incomplete or complete intestinal obstruction may be misdiagnosed as other diseases of the gastrointestinal tract, delaying the early diagnosis of abdominal aortic aneurysm.
(2) urinary system compression symptoms: due to abdominal aortic aneurysm compression or inflammatory abdominal aortic aneurysm invading into the ureter, ureteral obstruction, renal pelvic effusion, and the incidence of urinary stones will also increase, may appear Pain in the lower back, even severe abdominal pain that is released into the groin area, and may be accompanied by hematuria. Due to anatomical relationship, the left ureter is most susceptible.
(3) Symptoms of bile duct compression: It is rare in clinical practice. Patients often show discomfort and irritability in the liver area. In severe cases, yellow staining of the skin and sclera can occur, urine is red, stool is terracotta, and biochemical examination is obstructed. Changes in sexual jaundice.
3. Embolism symptoms: The thrombus of abdominal aortic aneurysm becomes an embolus once it has fallen off, embolizing the blood supply organs or limbs and causing acute ischemic symptoms, such as mesenteric vessels at the embolization site. Intestinal ischemia, severe cases can cause intestinal necrosis, patients with severe abdominal pain and bloody stools, followed by hypotension and shock, as well as abdominal peritoneal irritation, embolization to the renal artery, can cause infarction of the corresponding parts of the kidney, patients It is characterized by severe low back pain and hematuria. When embolized to the main arteries of the lower extremities, the corresponding limbs have pain, the pulse is weakened and disappeared, the limbs are paralyzed, the color is pale, and the sensation is abnormal.
4. Abdominal pulsating mass: This is the most common and most important sign of abdominal aortic aneurysm. Most patients have a sense of jumping around the heart or the umbilicus. About 1 in 6 patients report that the heart falls to the abdominal cavity. It is especially prominent in the supine position and at night. The mass is mostly located in the left abdomen. It has a continuous and pulsating and dilating sensation in multiple directions. The upper rim and the rib arch can accommodate two horizontal fingers, often indicating that the lesion is below the renal artery. If there is no gap, it indicates that the aneurysm is mostly located above the renal artery. At the same time, palpation of the abdomen is the simplest and most effective method for diagnosing abdominal aortic aneurysm. The accuracy rate is between 30% and 90%, although the abdomen pulsation mass is touched. Abdominal aortic aneurysm can be diagnosed, but the size and extent of the tumor still need to be confirmed by other auxiliary examinations. The surface of the mass can be tender, systolic murmur and/or convulsions and tremors, partial obesity, ascites and physical examination are not heard. Cooperative patients can lead to failure of palpation of abdominal aortic aneurysm. Of course, it is clinically necessary to distinguish from pancreatic masses, cystic lesions of the posterior abdominal wall or aortic distorted.
5. Rupture symptoms: Abdominal aortic aneurysm rupture is an extremely dangerous surgical emergency, the mortality rate is as high as 50% to 80%. The diameter of the aneurysm is the most important factor determining the rupture. According to Laplace's law, the load pressure of the wall It is proportional to the radius of the tumor. The larger the diameter of the tumor, the greater the risk of rupture. The data indicates that the rupture rate of abdominal aortic aneurysm within 5 years is 10% to 15% of the diameter of the tumor within 4 cm. 20% within 5cm, 33% for 6cm, and 75%~95% for 7cm or more. According to the relationship between the rupture rate of abdominal aortic aneurysm and the diameter of the tumor, the diameter of 6cm or more is called dangerous artery. Tumors, but a large number of recent imaging studies have shown that when the diameter of the abdominal aortic aneurysm reaches 5 cm, the risk of rupture is significantly increased. This view has been agreed by the vascular surgery community.
Gronenwet et al. found that in patients with chronic obstructive pulmonary disease and systolic hypertension, the risk of ruptured abdominal aortic aneurysm was significantly increased, although the rate of expansion of small aneurysms was not well predicted, but blood vessels were used. Ultrasound and CT tracking results show that the expansion rate of aneurysms is also significantly increased in patients with increased pulse pressure difference. The average annual expansion rate is 0.4 cm anteroposterior diameter and 0.5 cm transverse diameter. In normal patients, the anteroposterior diameter is only 0.19cm, the transverse diameter is only 0.22cm, usually the expansion speed of the aneurysm in the lateral direction is greater than the anteroposterior direction, so the cross section of the aneurysm is mostly elliptical, which coincides with the fact that the lateral aortic aneurysm ruptures. .
The clinical symptoms and duration of ruptured abdominal aortic aneurysm are determined by the specific circumstances of the rupture. In general, a typical abdominal aortic aneurysm rupture has the following triads: sudden mid-abdominal or diffuse abdominal pain, low Blood pressure and even mild to severe hemorrhagic shock and pulsatile abdominal mass, abdominal aortic aneurysm has five kinds of rupture methods, depending on the specific way, clinical manifestations are also different.
(1) Open rupture into the abdominal cavity: mostly the rupture of the anterior wall of the tumor. The clinical manifestations are mainly severe hemorrhagic shock, which is difficult to treat. The patient died more quickly than in the short term. Most patients died before arriving at the hospital. Therefore, the actual incidence rate is higher than the clinical statistics.
(2) retroperitoneal rupture: mostly the rupture of the posterior wall of the aneurysm, into the retroperitoneal space, the formation of retroperitoneal hematoma, the patient showed a pain in the mid-abdomen knife, about a quarter of patients with the waist and The pain in the ribs is predominant, and is released to the groin area and the thigh roots, accompanied by cold sweat, pale complexion, pulse beats and other signs of hemorrhagic shock, easy and acute pancreatitis, mesenteric vascular embolization, peptic ulcer perforation and dissection Diseases such as aneurysms are confused and should be well identified.
(3) Restrictive rupture: the ruptured hole is blocked by hematoma, and its clinical manifestations are similar to those of retroperitoneal rupture. The duration is short for about ten minutes and the length can be longer than 24 hours. Chronic restrictive rupture can sometimes be misdiagnosed as groin. Hemorrhoids, femoral neuropathy, etc., will eventually develop into an open rupture, so early diagnosis and surgical treatment should be made.
(4) rupture into the intestinal lumen: the formation of the primary abdominal aorta and intestinal fistula, clinical manifestations of gastrointestinal bleeding, abdominal pain, infection and other symptoms, patients with several days or weeks of intermittent gastrointestinal tract bleeding, eventually leading to major bleeding In the case of shock, especially in male patients, hemorrhagic anemia is the main feature, while the symptoms of abdominal pain are mild, fever is often relaxation heat, blood culture bacteria are consistent with the normal intestinal flora, and in a few cases intestinal bacteria Downstream of the blood can form septic arthritis or a localized infection of the lower extremities.
(5) rupture of the inferior vena cava or iliac vein: the formation of aortic-inferior vena cava or aortic-iliac vein fistula, the clinical incidence rate is less than 1%, mostly occurs in a large abdominal aortic aneurysm, patients may have congestion Sexual heart failure, varicose veins of the lower extremities, some patients have large mouthwash and lack of myocardial blood supply, and the clinical manifestations of left heart failure, individual patients have oliguric renal failure, abdominal examination, near the pulsatile mass The heart can touch the tremor, auscultation audible and continuous murmur, but usually systolic murmur.
Examine
Abdominal aortic aneurysm examination
In patients with larger abdominal aortic aneurysms, laboratory tests of blood often show changes in consumptive coagulation due to the expansion of the local vascular lumen of the aneurysm, uneven blood flow, and increased vascular endothelial cells. Shear force, resulting in local sustained fibrin and / or platelet deposition, and secondary fibrinolysis, so it is necessary to check platelet count, coagulation factor and fibrinogen before surgery, for fibrinogen at 200mg Below /dl, platelets below 150,000/mm3 should be treated with anticoagulant therapy. Otherwise, postoperative DIC and multi-system organ failure may occur due to the reduction of consumptive coagulation factors.
1. Abdominal plain film: 67% to 75% of the abdominal lateral radiograph may have calcification in the abdominal aortic wall, and 2/3 of the patients can roughly determine the size of the aneurysm through the calcification image, but Negative cases cannot deny the presence of abdominal aortic aneurysms.
2. Ultrasound examination
(1) Two-dimensional ultrasound:
1The characteristics of the acoustic image of the dissecting aneurysm: the longitudinal section shows that the outer diameter of the abdominal aorta is wider than normal, showing a double cavity (in most cases, the false cavity is wider than the true cavity), the cross section shows a double ring, and the inner ring is thin and weak. The endometrial gyrus is dedicated, swinging with the pulsation of the blood vessels, and sometimes the endometrium is interrupted.
2 pseudo-aneurysm sound features: pulsatile mass can be seen beside the abdominal aorta, the boundary is clear, there is no echo zone, no clear capsule wall echo, there is a channel between the echo-free zone and the abdominal aorta; There was no obvious abnormality in the abdominal aorta wall and lumen, and the tumor only communicated with the abdominal aorta by a breach.
(2) Color Doppler flow imaging:
1The characteristics of the acoustic image of the dissecting aneurysm: the blood flow in the true cavity is similar to the normal arterial blood flow, the blood flow is narrowed by the influence of the stripping cavity, and the blood flow in the false cavity is irregular, such as the blood velocity in the false cavity is too low, the thrombus is formed. The blood flow signal is not detected, but if there is a re-rupture, a blood signal is visible.
2 pseudo-aneurysm sound characteristics: can clearly show the channel between the tumor and the abdominal aorta, such as the narrow channel, which can be seen in the monochromatic or mosaic color blood flow signal, and the blood flow echo in the tumor is "cloud" Movement, if there is a thrombus, irregular low echo can occur at the edge of the tumor.
(3) Spectrum Doppler:
1 The characteristics of the acoustic image of the dissection aneurysm: the blood spectrum in the true cavity is similar to that of the normal artery. The blood flow spectrum in the pseudocavity is a low-speed disorder spectrum. Using color, the spectral Doppler can also determine the branch artery of the abdominal aorta (kidney artery, The blood of the superior mesenteric artery is from the true or the false lumen.
2 pseudo-aneurysm sound characteristics: can be measured in the tumor or in the channel connected to the tumor and the blood flow spectrum; high-speed high-resistance blood flow spectrum can be obtained at the break, the blood flow spectrum is biphasic (reciprocating sign ); eddy currents in the tumor cavity.
3. Spiral CT angiography (SCTA): High-speed spiral CT is used to perform slice scan with thickness of 3~5mm. After three-dimensional reconstruction, stereo images of arteries can be obtained. SCTA thoracic aorta and abdominal aortic aneurysm are developed. The basis of preoperative evaluation of internal treatment, CT scan has a positive value for the diagnosis of abdominal aortic aneurysm, can find a small abdominal aortic aneurysm, can find calcification and intratumoral thrombosis of the aortic wall, and can also find the formation of aneurysm rupture Retroperitoneal hematoma, CT is also very sensitive to the diagnosis of iliac aneurysms, while SCTA can stereoscopically show the morphology of aneurysms and their distal and proximal arteries, especially the relationship between aneurysms and renal arteries (Figure 5).
4. Magnetic resonance angiography (MRA) : MRA is a new technique for displaying blood vessels using the flow effects of MR. It can collect a series of continuous thin sections in cross-section, coronal or sagittal planes. The image data is then reconstructed. The most common reconstruction method is maximum intensity projection (MIP). The reconstructed blood vessel image is not only similar to conventional angiography, but also can be displayed in three dimensions (3D). That is to show the vascular projection image at any angle, suitable for examining blood vessels perpendicular to the imaging plane, and can be widely used for head and neck, chest and abdomen aorta and limb blood vessel examination.
When performing MRA examination on the patient, different spatial presaturation bands can be set as needed to inhibit the vein display of the artery or to inhibit the artery and display the vein. For patients with abdominal aortic aneurysm, since the tumor often contains a wall thrombus, MRA only It shows the lumen of blood flow, but can not reflect the true size of the tumor. Therefore, it is necessary to add a cross-sectional spin echo method to show the tumor and the intracavitary wall thrombus. At present, the general MRA technique shows that the blood vessel can be used. Injection of paramagnetic contrast agent (Gg-DTPA) can visualize blood vessels. In recent years, there have been many reports that MRA combined with paramagnetic contrast agents can enhance intravascular signals and improve image quality. Abdominal aortic aneurysms of MRA image.
5. Angiography: In the above three examinations can not make a diagnosis of abdominal aorta or can not determine the relationship between aneurysm and renal artery and various visceral arteries, should do conventional abdominal aortic angiography or digital subtraction angiography (digital Substraction angiography (DSA), angiography can undoubtedly provide the most direct image of the abdominal aorta. Aneurysm angiography is the bulging of the artery. This bulging can be long and uniform, and most of the aneurysms are The fusiform shape also has a cyst shape, which can be single or multiple. The disadvantage of angiography is that the actual size of the tumor cavity cannot be correctly displayed when there is a blood clot in the tumor.
Diagnosis
Diagnosis and diagnosis of abdominal aortic aneurysm
According to the slow onset of the disease, the periumpanal or mid-abdominal hernia and the swelling pulsation can be accompanied by acute or chronic ischemic symptoms of the lower extremity; the abdominal percussive tumor has mild tenderness, and some cases are You can hear vascular murmurs and tremors, you can suspect abdominal aortic aneurysm, further color ultrasound, CT or magnetic resonance examination, showing the diameter of abdominal aortic aneurysm, the relationship with adjacent tissues, if necessary, abdominal aorta angiography To further confirm the diagnosis.
Differential diagnosis
1. Distorted abdominal aorta can cause pulsatile mass, but the long abdominal aorta is often located on the left side of the midline, easy to push, while the edge of the abdominal aortic aneurysm is located in the midline of the umbilical cord and two Side expansion, the tumor is more fixed.
2. The two types of tumors, the retroperitoneal mass and the pancreatic tumor, can have a pulsatile conduction pulsation, but there is no swelling, and the abdominal aortic aneurysm has a special expansive pulsation.
B-ultrasound, CT and MRI examinations are helpful for identification.
