Selasa, 29 Januari 2008
Senin, 10 Desember 2007
Achalasia
Clinically important features defined by this pathophysiology include the following:
- Peristalsis in the distal smooth muscle segment of the esophagus may be lost. Contractions occur, but they are weak; simultaneous; uncoordinated; and, therefore, nonpropulsive.
- The LES fails to relax, either partially or completely.
- LES pressure is elevated in some patients.
- The coordination of LES relaxation in response to swallowing and esophageal contraction is lost.
Race: No racial predilection has been described for achalasia.
Sex: Achalasia has no sex predilection.
Limitations of Techniques: A fluoroscopically guided barium swallow study that demonstrates 1 or more findings (see X-ray) is highly suggestive of achalasia. However, a definitive diagnosis can be made only by means of esophageal manometry, preferably with the addition of upper endoscopy.
RADIOGRAPH
Features of achalasia depicted at barium study under fluoroscopic guidance include the following:
- Failure of peristalsis to clear the esophagus of barium with the patient in the recumbent position
- Antegrade and retrograde motion of barium in the esophagus secondary to uncoordinated, nonpropulsive, tertiary contractions
- Pooling or stasis of barium in the esophagus when the esophagus has become atonic or noncontractile (which occurs late in the course of disease)
- LES relaxation that is incomplete and not coordinated with esophageal contraction
- Dilation of the esophageal body, which is typically maximal in the distal esophagus
- Tapering of the barium column at the unrelaxed LES, resulting in the bird beak sign
- Associated epiphrenic diverticula (possible finding)
Acetabulum, Fractures
Background
Most acetabular fractures occur in the setting of significant trauma secondary to either a motor vehicle accident or a high-velocity fall. Blunt force is exerted on the femur, passes through the femoral head, and is transferred to the acetabulum. The direction and magnitude of the force, as well as the position of the femoral head, determine the pattern of acetabular injury. The determination of the pattern of injury is key to the classification of an acetabular fracture. Once the acetabular fracture is classified, appropriate therapy can be planned and implemented.
Pathophysiology
One function of the acetabulum is to provide a means of transferring weight-bearing forces from the appendicular skeleton to the axial skeleton via the acetabulum's articulation with the femoral head. The femoral head also transfers high-energy forces to the acetabulum in the setting of trauma. The pattern of acetabular injury is determined by the position of the femoral head at the time of the traumatic event. When the femoral head is rotated internally, the force is transferred to the posterior column. When the femoral head is rotated externally, the force is directed toward the anterior column. If the femoral head is adducted, the force is transmitted to the acetabular roof; if it is abducted, the force is directed inferiorly.
The direction of the force also determines which part of the acetabulum is injured. An anterior force applied to the femoral head is transmitted to the posterior wall and column. Conversely, a posterior force affects the anterior wall and column. A force to the lateral aspect of the femoral head is directed toward the medial wall of the acetabulum, often resulting in transverse acetabular fractures.
Frequency
United States
Table 1. Relative Frequency of Acetabular Fracture Types
| Fracture Type | Letournel1* (%) | Matta2** (%) | Dakin et al3† (%) |
|---|---|---|---|
| Both-column | 27.9 | 33.3 | 14.1 |
| Transverse with posterior wall | 20.6 | 23.5 | 35.3 |
| Posterior wall | 22.4 | 8.6 | 12.9 |
| T-shaped | 5.3 | 12.2 | 3.5 |
| Transverse | 3.7 | 3.5 | 8.2 |
| Anterior column | 3.9 | 4.7 | 1.2 |
| Anterior column with posterior hemitransverse | 8.8 | 5.9 | 3.5 |
| Posterior column with posterior wall | 3.5 | 3.9 | 18.8 |
| Posterior column | 2.3 | 3.1 | 1.2 |
| Anterior wall | 1.6 | 1.2 | 1.2 |
*n = 567.
**n = 255.
† n = 85.
Mortality/Morbidity
- Associated injuries
- Significant trauma is required to cause a fracture of the acetabulum. Therefore, acetabular fractures are most often observed in the setting of major trauma, in which injuries elsewhere in the body are common.
- Intracranial, spinal, intrathoracic, and intra-abdominal injuries often are observed in conjunction with acetabular fractures.
- Pelvic ring and extremity fractures also are common in patients with acetabular fractures.
- Bladder injury and clinically significant pelvic hemorrhage are not routinely observed in the setting of acetabular fracture unless a concomitant pelvic ring injury also is present.
- Complications of acetabular fracture include the following:
- Immediate posttraumatic complications include injuries to the sciatic, femoral, or superior gluteal nerves.
- Immediate postsurgical complications include nerve injuries, such as sciatic, femoral, and superior gluteal nerve injuries; wound infection; and thromboembolic disease.
- Late complications include heterotopic ossification, osteonecrosis (avascular necrosis) of the femoral head or acetabular fracture fragment, chondrolysis, posttraumatic osteoarthritis, and acetabular implant failure.
Age
Elderly patients and persons with osteoporosis may occasionally have an acetabular fracture as a result of low-energy trauma, such as a fall from a standing height.
Anatomy
Gross anatomy
The acetabulum is formed from 3 ossification centers; the ilium, ischium, and pubis each contribute to its development at the triradiate cartilage. The important anatomic components of the acetabulum are the columns, walls, dome, and quadrilateral plate. The acetabulum is divided into 2 columns: anterior and posterior. The 2 columns are described as having the shape of an inverted Y, or of the Greek letter lambda (l).
The anterior column is the larger of the 2 columns. It begins at the iliac wing and extends down the anterior portion of the acetabulum to incorporate the superior pubic ramus. The posterior column begins at the sciatic notch and extends down the posterior acetabulum into the ischium. Both columns are attached to the axial skeleton by the sciatic buttress, which connects the acetabulum to the sacroiliac joint. The column concept is appreciated more easily on the lateral view (see Image 1).
The posterior wall is larger than the anterior wall. The lateral portion of either wall is termed the acetabular rim. The walls help to stabilize the hip joint. The quadrilateral plate is the medial wall of the acetabulum. The dome of the acetabulum is the superior aspect that carries most of the weight-bearing forces. The obturator ring is an important landmark because some acetabular fractures spare the ring, while others disrupt it. The iliac wing is considered part of the anterior column.
Radiographic anatomy
The anteroposterior (AP) view of the pelvis is the primary tool for radiographic evaluation of the acetabulum (see Images 2-3). The iliopectineal, or iliopubic, line is the radiographic landmark for the anterior column. It begins at the sciatic notch and travels along the superior pubic ramus to the symphysis pubis. The ilioischial line demarcates the posterior column. It also begins at the sciatic notch, coursing inferiorly to the medial border of the ischium. The ilioischial line should pass through the acetabular teardrop. If it does not overlap the teardrop, the ilioischial line and, thus, the posterior column are disrupted.
The iliac wing is considered to be part of the anterior column. An iliac wing fracture in the setting of an acetabular injury indicates anterior column involvement. An iliac oblique radiograph provides a better view of the iliac wing. The posterior wall of the acetabulum is more visible than the anterior wall on the AP view because of its more lateral position. The anterior wall can be difficult to appreciate on the AP view. The obturator oblique view better depicts the posterior wall, and the iliac oblique view better depicts the anterior wall. The integrity of the obturator ring is an important feature to recognize. Certain fracture patterns (such as those of column and T-shaped fractures) characteristically include fractures through the obturator ring.
The oblique, or Judet, views of the pelvis are named relative to the side of interest (see Images 4-5). For example, if the acetabular fracture is on the left side, the views are named with reference to the left side. The left posterior oblique radiograph displays the iliac wing en face; therefore, this view is termed the left iliac oblique view. The right posterior oblique radiograph shows the obturator ring en face; therefore, this view is the left obturator oblique view. The iliac oblique view clearly demonstrates the iliac wing, sciatic notch, and ischial spine. In addition, the posterior column and anterior wall of the acetabulum are seen in profile. The obturator oblique radiograph provides the best depiction of the obturator ring and shows the anterior column and posterior wall in profile.
Clinical Details
Fractures of the acetabulum are most commonly classified according to the system described by Judet and colleagues.4 The system is based on the orientation of the fractures and the structures involved. In this system, the orientation of the fracture is based on its depiction on a lateral view of the acetabulum. In order to arrive at the correct classification, AP and oblique (Judet) radiographs of the pelvis are obtained and analyzed. Some authors have questioned the necessity of oblique views of the pelvis in the age of multidetector CT scanning. 5 Harris and colleagues have proposed a new classification system based on the multidetector CT scan appearance.6, 7 Other authors have defended the utility of the standard radiographic series in the evaluation of acetabular fractures.8 The Judet system will be presented in the remainder of this article.
In the system described by Judet and colleagues, 10 patterns of acetabular fracture are defined. The 10 patterns are divided into 5 elementary and 5 associated patterns (see Image 6). Elementary patterns include fractures with a single fracture orientation, whereas associated patterns usually involve combinations of the elementary fractures. Elementary patterns include anterior wall, posterior wall, anterior column, posterior column, and transverse fractures. Associated patterns include both-column fractures, posterior column fractures with posterior wall fractures, transverse fractures with posterior wall fractures, T-shaped fractures, and anterior column fractures with posterior hemitransverse fractures. For simplicity, the 10 patterns can be grouped into 3 categories: wall, column, and transverse fractures. Some fractures fit into 2 categories. The following fractures are indicated by pattern type:
- Wall fractures
- Anterior wall
- Posterior wall
- Posterior column with posterior wall (also a column fracture)
- Transverse with posterior wall (also a transverse fracture)
- Column fractures
- Anterior column
- Posterior column
- Both-column
- Posterior column with posterior wall (also a wall fracture)
- Anterior column with posterior hemitransverse (also a transverse fracture)
- Transverse fractures
- Transverse
- T-shaped
- Transverse with posterior wall (also a wall fracture)
- Anterior column with posterior hemitransverse (also a column fracture)
Fracture patterns
Both-column fractures are the most common acetabular injury. As the name implies, the anterior and posterior columns are involved (see Image 6). On AP radiographs, a disruption of the iliopectineal and ilioischial lines, as well as the obturator ring, can be seen (see Image 24). An iliac wing fracture may be seen on the AP view, but often, it is appreciated only on the iliac oblique radiograph (see Image 25). The pathognomonic spur sign (see Radiograph Findings) is present on the obturator oblique view (see Image 26) and confirmed on a computed tomography (CT) scan (see Images 27-29).
Isolated anterior and posterior column fractures are uncommon. Anterior column fractures disrupt the iliopectineal line while preserving the ilioischial line. Conversely, posterior column fractures disrupt the ilioischial line but not the iliopectineal line (see Images 18-23). Column fractures divide the acetabulum into front and back halves (see Image 7). The posterior column fracture with a posterior wall fracture has the features of each of its components (see Image 6). The slightly more common anterior column fracture with a posterior hemitransverse fracture is the most complex acetabular fracture to classify.
The combination of column fractures and transverse fractures can be difficult to appreciate radiographically (see Image 30). The iliopectineal and ilioischial lines are broken, and an iliac wing fracture should be evident. Unlike the both-column fracture, which shares these features, the obturator ring is intact and the spur sign is not present. On CT scans, the anterior column and the posterior transverse fracture planes can be appreciated (see Image 31).
Transverse fractures are transverse because of their appearance when the acetabulum is examined from the lateral view (see Image 6). The iliopectineal and ilioischial lines are interrupted, but the obturator ring is spared. On CT scans, the fracture is oriented vertically (front to back).
Transverse fractures divide the acetabulum into top and bottom halves, as seen on the lateral view of the acetabulum (see Image 7). The transverse fracture with a posterior wall fracture is a common fracture that incorporates the features of transverse and posterior wall elementary fractures (see Images 13-15). The T-shaped fracture is a fairly common acetabular injury. This fracture has the characteristics of an elementary transverse fracture with the addition of a medial acetabular wall fracture extending through the obturator ring (see Images 16-17). The anterior column with posterior hemitransverse fracture is discussed earlier.
In a study by Brandser and colleagues, the following 3 most common types of acetabular fracture accounted for roughly two thirds of all fractures: both-column fractures, transverse fractures with posterior wall fractures, and posterior wall fractures.2 This number increased to 90% when the next 2 most common fracture types were considered: T-shaped and transverse fractures. The frequency of the fractures types is as follows:
- Commonly occurring acetabular fractures (90%)
- Both-column
- Transverse with posterior wall
- Posterior wall
- T-shaped
- Transverse
- Uncommonly occurring acetabular fractures (10%)
- Anterior column
- Anterior column with posterior hemitransverse
- Posterior column with posterior wall
- Posterior column
- Anterior wall
Preferred Examination
AP radiography of the pelvis is used in the initial radiographic assessment of patients with major trauma that is suggestive of pelvic and/or acetabular injury (see Images 2-3). Images are obtained with the patient in the supine position and with the radiographic beam passing in an AP direction. Abnormalities depicted on the AP pelvis radiograph direct the need for the next set of radiographs. Acetabular fractures are imaged by using oblique (ie, Judet) views of the pelvis. Pelvic ring fractures are imaged by using inlet and outlet views of the pelvis (see Pelvic Ring Fractures).
Oblique, or Judet, radiographs of the pelvis are obtained with the patient in the left posterior oblique and right posterior oblique positions (see Images 4-5). The patient should be at a 45º angle relative to the radiographic beam, which remains perpendicular to the cassette. This technique results in 2 orthogonal radiographs of the pelvis. The patient must be moved to the oblique position; the radiographic tube is not moved so as to be at a 45º angle relative to the patient and film cassette. Angling the tube results in unacceptable radiographic distortion. A common mistake in this radiographic technique is the positioning of the patient in an oblique position that is not steep enough, with a resultant angle of less than 45º. On an oblique view obtained with good positioning, the coccyx should project over the femoral head.
Pelvic CT scans may be obtained alone or in combination with abdominal CT scans during the initial trauma evaluation. Axial CT scans may be obtained, but helical CT scanning yields better 2-dimensional and 3-dimensional reformatted images. Pelvic CT scans allow the detection of subtle fractures and displacements that are not appreciated on radiographs.
Limitations of Techniques
Virtually all acetabular fractures can be correctly classified after careful interpretation of AP and oblique radiographs of the pelvis. Intra-articular fracture fragments can be difficult to recognize on radiographs.
Compared with radiography, pelvic CT scanning allows a more precise determination of the degree of articular involvement, as well as of fragment displacement and orientation. Pelvic CT scanning also permits the identification of intra-articular fracture fragments. In complex acetabular fractures, 3-dimensional reformatted images may help conceptualize the fracture pattern and, thereby, aid in the planning of orthopedic surgery.
RADIOGRAPH
Findings
Brandser and Marsh devised a system of observations leading to the correct classification of most acetabular fractures.9 The answers to the following questions about the radiographic observations are used to determine the acetabular fracture pattern:
- Is a fracture of the obturator ring present? A fracture of the obturator ring indicates either a T-shaped or a column fracture (with the exception of the hemitransverse type of fracture). An intact obturator ring eliminates these fractures from consideration.
- Is the ilioischial line disrupted? Disruption of the ilioischial line occurs in fractures involving the posterior column or fractures in the transverse group.
- Is the iliopectineal line disrupted? Disruption of the iliopectineal line indicates anterior column involvement or 1 of the transverse-type fractures.
- Is the iliac wing above the acetabulum fractured? Iliac wing fractures are observed in fractures involving the anterior column.
- Is the posterior wall fractured? Posterior wall fractures can occur in isolation or in combination with posterior column or transverse fractures.
- Is the spur sign present? The spur sign is observed exclusively in the both-column fracture. The spur is a strut of bone extending from the sacroiliac joint. Usually, this strut of bone connects to the articular surface of the acetabulum. In the both-column fracture, this connection is disrupted; a fractured piece of bone that resembles a spur remains. The spur sign is best depicted on the obturator oblique view (see Image 26). In addition, the spur sign can be appreciated on CT scans (see Image 27).
Table 2 shows the combined set of radiographic and CT scan observations that are useful in acetabular fracture classification.
Table 2. Radiographic Features of Acetabular Fracture Types9
| Fracture Type | Obturator |
|---|
| Ring |
|---|
| Fracture | Ilioischial |
|---|
| Line |
|---|
| Disrupted | Iliopectineal |
|---|
| Line |
|---|
| Disrupted | Iliac |
|---|
| Wing |
|---|
| Fracture | Posterior |
|---|
| Wall |
|---|
| Fracture | Pelvis |
|---|
| Into |
|---|
| Halves | Spur |
|---|
| Sign | CT Scan |
|---|
| Fracture |
|---|
| Orientation | ||||||||
|---|---|---|---|---|---|---|---|---|
| Both-column | Yes | Yes | Yes | Yes | No | Front/back | Yes | Horizontal |
| Anterior column | Yes | No | Yes | Yes | No | Front/back | No | Horizontal |
| Posterior |
| column | Yes | Yes | No | No | No | Front/back | No | Horizontal |
| Posterior |
| column with |
| posterior wall | Yes | Yes | No | No | Yes | Front/back | No | Horizontal |
| T-shaped | Yes | Yes | Yes | No | No | Top/bottom | No | Vertical |
| Transverse with |
| posterior wall | No | Yes | Yes | No | Yes | Top/bottom | No | Vertical |
| Transverse | No | Yes | Yes | No | No | Top/bottom | No | Vertical |
| Posterior wall | No | No | No | No | Yes | No | No | Oblique |
| Anterior wall | No | No | Yes | No | No | No | No | Oblique |
| Anterior column |
| with posterior |
| hemitransverse | No | Yes | Yes | Yes | No | N/A* | No | N/A |
*N/A indicates not applicable.
Degree of Confidence
By using Brandser and Marsh's system, the accurate classification of acetabular fractures is possible in almost every patient.
False Positives/Negatives
An accessory ossification center, the os acetabulum, can mimic an acetabular wall fracture. Its differentiating features include its characteristic superolateral location and well-corticated margins. Fractures of the anterior puboacetabular junction can be observed in pelvic ring fractures. These fractures may extend into the anterior column of the acetabulum, but they are not anterior column fractures per se. Such fractures are more correctly considered to be superior pubic ramus fractures.
Abdominal Aortic Aneurysm, Rupture
Background
Abdominal aortic aneurysms (AAAs) are segmental dilatations of the aortic wall that cause the vessel to be larger than 1.5 times its normal diameter or that cause the distal aorta to exceed 3 cm. These can continue to expand and rupture spontaneously, exsanguinate, and cause death.
AAA rupture is an important cause of unheralded deaths in people older than 55 years, claiming more than 15,000 lives annually in the United States alone.
Pathophysiology
A marked decrease in aortic elastin, an increase in collagen production and degradation, inflammatory changes, and imbalances of matrix metalloproteinases and their inhibitors have been noted in pathologic studies. Atherosclerosis may be only a facilitating factor.
Genetic predisposition plays some role, especially in disorders such as Marfan disease and type IV Ehlers-Danlos syndrome. Familial clustering of cases also has been documented.
Clinical risk factors that predispose individuals to these degenerative changes in the arterial wall include smoking, advanced age, male sex, chronic obstructive pulmonary disease (COPD), hypertension, and family history.Females, African-Americans, and persons with diabetes appear to have a lower prevalence of AAA.
Larger aneurysms tend to enlarge at a higher rate, as noted by Bernstein.
Table 1. Growth Rate of AAAs
| Initial Size of AAA, cm | Mean Growth Rate, cm/y | 95% Confidence Interval of the Mean Growth Rate |
|---|---|---|
| 3.0–3.9 | 0.39 | 0.20, 0.57 |
| 4.0–4.9 | 0.36 | 0.21, 0.50 |
| 5.0–5.9 | 0.43 | 0.27, 0.60 |
| 6.0–6.9 | 0.64 | 0.16, 1.1 |
The natural history of an individual case is difficult to predict, and AAAs can have intervals of stability and slow and rapid expansion. The general recommendation is to consider elective aneurysmorrhaphy for aneurysms with a diameter of 5 cm or greater or for small aneurysms that have an average growth rate of more than 0.5 cm/y. Approximately 20% of aneurysms expand faster than 0.4 mm/y; the rest do so at slower rates.
AAA rupture
In addition to the initial aneurysm diameter, independent predictors of rupture include current smoking, lower forced expiratory volume (FEV-1), and higher mean blood pressure, all risk factors possibly amenable to modification. Findings from various series have suggested that diabetes mellitus, elevated levels of serum markers such as amino-terminal type III procollagen propeptide (PIIINP), a rapid rate of AAA expansion, and unfavorable morphology and aortic wall compliance are also predictive of rupture. Of note, the prevalence of diabetes in the population with AAAs is relatively low.
Attempts have been made to index the aneurysmal diameter to individual body size or anatomic points of reference (eg, body surface area, supraceliac aortic diameter, aneurysm length), but no feature has been found to be highly predictive of rupture. Rupture has been observed in some AAAs smaller than 5 cm in diameter but wider than the transverse dimension of the third lumbar vertebral body.
Findings from a few studies have suggested that most AAAs rupture into the left retroperitoneum. The retroperitoneum contains the leak by means of mechanisms that cause clotting or tamponade. This rupture can also cause abdominal, back, or flank pain; this symptom is related to impingement of the hematoma on adjacent structures.
Aneurysms that continue to leak or those that rupture into the peritoneal cavity can result in hemodynamic collapse and, often, death.
Frequency
United States
The estimated incidence of ruptured AAA in a population study from Sweden was 0.06 case per 1000 people.This rate increased with age; the age-adjusted incidences were less than 0.01, 0.37, or 1.36 per 1000 people younger than age 60 years, those aged 70-79 years, and those older than 90 years, respectively.
The best-known predictor of rupture rate is the maximal aneurysm diameter. Simplified estimates for the annual rupture rates based on size are as follows:
Table 2. Annual Rupture Rates Based on Size
| Maximum Aneurysmal Diameter, cm | 5-Year Rupture Rate, % |
|---|---|
| <4.0 | 2 |
| 4.0–4.9 | 3–12 |
| 5.0–5.9 | 25 |
| 6.0–6.9 | 35 |
| >7.0 | 75 |
The annual rupture rate in the UK Small Aneurysm Trial (N = 2257, with about half in randomized arm and half in the registry) was 2.2% per year for the first 3 years of follow-up. The initial aneurysm diameter was 3-6 cm, and the mean was approximately 4.4 cm.
AAA rupture after stent-graft placement has been observed with specific devices, but device evolution and operator experience in both patient selection and device placement make it difficult to provide any stable estimates of the incidence at this time.
Mortality/Morbidity
The mortality rate for ruptured AAA is substantial. As many as 2 of 3 patients with ruptured AAA die before arriving at the hospital.Of those who reach the hospital, as many as one fifth of those who die do so before the operation, and the overall mortality rate still averages approximately 49%.
Multivariate analyses by Harris and coworkers revealed adverse predictors for early mortality, as shown in Table 3 below.
Table 3. Predictors of Early Mortality
| Risk Factor | Percentage of Patients With Factor, % | Associated Mortality Rate, % | Mortality Rate in Patients Without Factor, % |
|---|---|---|---|
| Cardiac arrest | 19 | 81 | 26 |
| Loss of consciousness | 26 | 72 | 24 |
| Intraoperative BP <> | 28 | 62 | 24 |
Note: For all comparisons, P <.05 unless otherwise noted. BP indicates blood pressure.
*P value <.10.
Deaths that occurred after the second postoperative day were predicted by variables shown in Table 4 below.
Table 4. Variables Predictive of Mortality
| Risk Factor | Percentage of Patients With Factor, % | Associated Mortality Rate, % | Mortality Rate in Patients Without Factor, % |
|---|---|---|---|
| Renal failure | 30 | 75 | 8 |
| Respiratory failure | 28 | 69 | 19 |
In the consecutive series of 180 patients with ruptured AAA, the following factors were independently related to the mortality rate: age; systolic BP less than 80 mm Hg; and a history of hypertension, angina, or myocardial infarction (MI). In patients who survived the surgery, the causes of death were as follows:
- Renal failure or multisystem failure (32%)
- Cardiac failure (29%)
- Respiratory failure, including pneumonia (17%)
- Coagulopathy (12%)
- GI hemorrhage (3%)
- Perforated duodenal ulcer (1.5%)
- Renal hemorrhage (1.5%)
- Hemorrhage from graft anastomosis (1.5%)
- Stroke (1.5%)
- Aspiration (1.5%)
Major postoperative complications observed in a series of 174 patients at the Mayo Clinic are shown in Table 5 below.
Table 5. Major Postoperative Complications
| Event | Percentage of Patients Affected, % | Case Fatality Rate, % |
|---|---|---|
| Respiratory failure | 48 | 34 |
| Tracheostomy | 14 | 44 |
| Renal failure | 29 | 76 |
| Sepsis | 24 | 45 |
| MI/CHF* | 24 | 66 |
| Bleeding | 17 | 90 |
| Stroke | 6 | 50 |
| Ischemic colitis | 5 | 67 |
| Lower extremity ischemia | 3 | 17 |
| Paraplegia/paraparesis | 2 | 50 |
*CHF indicates congestive heart failure.
Other major postoperative morbidities reported in the literature include the following:
- Delayed hemorrhage from iatrogenic injuries
- GI or genitourinary tract injuries
- Pancreatitis
- Duodenal obstruction
- Prosthetic graft infection
One in 5 patients undergo a repeat operation. One half undergo repeat laparotomy, and the other half undergo a tracheostomy or vascular procedure.
Late in-hospital deaths occur at a mean of 25 days ± 23.
The long-term outlook for patients is grim. Table 6 below shows survival statistics of the 147 patients with ruptured AAA (defined as blood outside the aortic wall) in the prospective Canadian Aneurysm Study.Younger age and total intraoperative urine output were the only factors that were independently predictive of survival.
Table 6. Cumulative Survival of Ruptured AAA Patients, as Determined at Kaplan-Meier Analysis
| Time Since First Diagnosis | Survival Rate of Cohort, % | Patients Surviving > 1 mo After Surgery, % |
|---|---|---|
| 1 month | 49 | 96 |
| 1 year | 41 | 87 |
| 2 years | 37 | 77 |
| 3 years | 36 | 73 |
| 4 years | 29 | 60 |
| 5 years | 26 | 53 |
Roughly 40% of early and late ( <5>
The availability of vascular surgeons, as opposed to general surgeons, was independently associated with a decreased 30-day mortality rate.
Sex
- In 2001, the National Center for Health Statistics reported that annual deaths attributable to AAA are almost 2-fold higher for males compared with females.
- An autopsy study revealed that the peak incidence of AAA was a decade later for women compared with men. Specifically, the peak incidence for women was at 90 years (4.5%) and 80 years in men (5.9%).
- Females were noted to have 3 times more ruptures than males in the UK Small Aneurysm Trial.In addition, females who have ruptured AAA may have a higher mortality rate than that of their male counterparts.
Age
- The incidence of AAA increases significantly after age 55 years in men and after age 70 years in women.
- The mean age of men with ruptured AAA is 70.6 years (range, 44-89 y) versus 77.3 years (range, 67-86 y) for women.
- Consequently, a number of competing comorbidities occur in this elderly cohort. These diminish the long-term survival rates even after successful AAA repair. On average, two thirds of postoperative patients died within the next 5 years, mostly due to causes related to cardiovascular disease.
Anatomy
Approximately one third of AAAs originate close to or at the level of the renal arteries, and suprarenal involvement has been reported in as many as 10% of patients.
In an old series by Rosch, 1 in 3 patients had accessory renal arteries, of which 7% arose from the AAA, and 1 in 5 patients had celiac or superior mesenteric artery stenosis. As many as 30% of patients with AAA can have renal artery stenosis. These are relevant findings because colon ischemia, as well as renal failure, can occur after aneurysmectomy.
A Japanese series of 97 cases of ruptured AAA revealed the following distribution of sites of rupture:
- Right lateral wall - 28%
- Pelvic arteries - 22%
- Posterior wall - 19%
- Left lateral wall - 17%
- Anterior wall - 10%
- Suprarenal - 4%
In a series of 226 AAAs in Italy, bleeding occurred into the following regions41:
- Retroperitoneal - 85.3%
- Peritoneal - 7.1%
- Inferior vena cava (IVC) or iliac vein - 5.8%
- Enteric - 1.8%
Although ruptures into the retroperitoneum typically originate from the left posterior aspect of the AAA, ruptures into the intestine tend to occur from the right anterior aspect.
Clinical Details
As many as three fourths of AAAs are initially asymptomatic. Most aneurysms are incidentally discovered during routine physical examination, during a diagnostic imaging study, or during surgery for other abdominal pathology.
Hypotension, pulsatile abdominal mass, and flank or back pain constitute the classic triad for ruptured AAA. However, this triad may be incomplete in as many as 50% of patients. Cardiac arrest can be the clinical presentation in a fourth of patients. In 1985, Donaldson et al described the presentation of their series of 81 patients that survived to undergo surgery for ruptured AAA.
Symptoms
- Abdominal pain - 58%
- Back pain - 70%
- Syncope - 30%
- Vomiting - 22%
Findings
- Mass - 91%
- Tenderness - 78%
- Systolic blood pressure less than 80 mm Hg - 42%
- White blood cell count greater than 10,000/µL - 79%
- Hematocrit less than 38-42%
- AAA apparent on abdominal plain film - 74%
Atypical presentations
- Pain radiating to the groin
- Back pain from AAA erosion into the vertebral body, with rare false aneurysm formation into the left psoas muscle
- Acute femoral neuropathy with or without thigh ecchymosis due to femoral nerve compression as blood dissects inferiorly between the iliacus and psoas muscles and the overlying fascial pockets
- Partial upper GI obstruction from AAA compression of the third portion of the duodenum
- Lower extremity ischemia and visceral thromboembolism caused by embolization of AAA mural thrombi
- Acute bilateral limb ischemia from aortic thrombosis
- GI bleeding secondary to aortoenteric fistula, usually involving the third part of the duodenum
- High output CHF, widened pulse pressure with machinery-like murmur, hematuria, rectal bleeding, priapism, or lower extremity swelling related to a fistula from the aorta to IVC or renal, lumbar, or common iliac vein
Preferred Examination
Intravenous access with 2 large-bore catheters should be established if a ruptured AAA is suspected. Blood should be drawn for stat determination of the CBC and kidney profile and for blood typing and screening. The vascular surgery team should be involved from the outset.
Ideally, in a hemodynamically stable patient, nonenhanced and enhanced helical or spiral CT of the thorax, abdomen, and pelvis should be expeditiously performed. This examination provides key information about the extent of aneurysmal disease, and it can be used to confirm and localize the site of rupture.
In the patient with an unstable presentation, an emergency operation is indicated. Time may permit only rapid bedside ultrasonography (US) and Doppler study of abdominal aorta and iliac arteries to confirm the presence of aneurysms.
The maximal aneurysm diameter is adequately assessed by using B-mode ultrasonography, CT scanning, and MRI. Aortography reveals only the lumen of the AAA because laminated clot obscures the outer limit of the aneurysm wall. Therefore, it often causes underestimation of the true aortic diameter.
Limitations of Techniques
Although CT and MRI provide detailed information about the blood vessels and their surrounding structures, these examinations require time; therefore, they may be unsuitable for use in patients in unstable condition. When contrast material is used in conjunction with CT to delineate blood-filled structures, it poses a risk of acute renal failure, particularly in hypovolemic elderly patients who may already have baseline nephrosclerosis or diabetic nephropathy.
Sonography is a quick and convenient modality, but it is much less sensitive and specific for the diagnosis of aneurysmal rupture. The absence of sonographic evidence of rupture does not rule out this entity if clinical suspicion is high.