History of present illness
The patient is a male in his 30s who presented to the emergency department (ED) with a right arm laceration and suicidal ideation. The patient was in an argument with several family members just prior to presentation, and in frustration drove his fist through a glass window. Upon presentation, he was complaining of pain in his right arm but denied numbness, paresthesia, and weakness in the right hand.
Past Medical History: Depression
Past Surgical History: Incision and drainage of an abscess from a prior gunshot injury
Vital Signs: T 98.3°F BP 135/89 P 63 R 16 SaO2 98% on room air
Physical Exam: The patient is an African American male who appears his stated age and is in no apparent distress. He has a 3 cm linear laceration to the volar surface of the right forearm with a moderate amount of pulsatile bleeding and no obvious foreign bodies or gross contamination present. His distal ulnar and radial pulses are intact in the right wrist with a brisk capillary refill in the right fingers. He has intact sensation to light touch in the median, ulnar, and radial nerve distribution in the right hand. He also has intact motor function of the radial, median, and ulnar nerves. Cardiovascular, pulmonary, abdominal, and neurologic exams are within normal limits.
Na: 140 K: 3.9 CO2: 32 Cr: 0.96 Glucose: 107
EtOH: 241 Urine Drug Screen: Negative
X-ray Right Radius/Ulna: No acute osseous findings of the right
forearm. Large soft tissue edema without visible radiopaque foreign body.
The patient presented with a simple laceration and what appeared to be a small, superficial arterial injury to the right forearm. Hemostasis was achieved quickly with compression over the injury, and the wound was irrigated with saline. The wound was repaired with two horizontal mattress sutures and one simple interrupted suture with good approximation and cosmesis. It was dressed with gauze and Kerlix, and the patient was discharged with instructions to follow up in one week for suture removal.
The patient returned to the ED two weeks later. At that time, he reported that the wound had been bleeding for two days and his forearm had become increasingly swollen. His repeat exam revealed a diminished ulnar pulse in his right wrist and a palpable pulse over his laceration repair. A CT angiogram of the right upper extremity revealed a 2.2 cm multilobulated pseudoaneurysm arising from the ulnar artery at the level of the proximal forearm with no active extravasation. Hand surgery was consulted and recommended placing a compression dressing over the area and to leave the sutures in place. Follow up was arranged three days later in hand clinic.
The patient was seen in hand clinic and the decision was made to repair the pseudoaneurysm operatively. He was taken to the operating room the following day and underwent pseudoaneurysm excision and primary repair of the ulnar artery with no complications. A heparin drip was started post-operatively and the patient was discharged on post-op day three with instructions to take a full dose aspirin twice daily.
An aneurysm is defined as a localized dilation of an artery to at least 1.5 times its normal diameter. A true aneurysm involves dilatation of all three layers of the vessel wall: the intima, media, and adventitia. A false aneurysm, or pseudoaneurysm, is similar but does not include all layers of the arterial wall. Pseudoaneurysms may be confused with a pulsatile hematoma, which often occurs during traumatic injury to the blood vessel.
The most common cause of pseudoaneurysm formation is secondary to catheterization for either angiography or cardiac catheterization, and they are most commonly found in the femoral artery. Meanwhile, true aneurysms are most commonly found in the infrarenal abdominal aorta, as well as the iliac, femoral, and popliteal arteries.
Aneurysms and pseudoaneurysms are much less frequently encountered in the upper extremities, as in the case described above. Despite the low overall incidence of upper extremity pseudoaneurysms, several case reports have been published describing pseudoaneurysm formation following traumatic injury to the affected artery. Cases have been reported following self-inflicted injuries, blast injuries during combat situations, and injection drug use.[2,3] Pseudoaneurysms can also form in vascular access sites of hemodialysis patients, most frequently occurring with AV grafts. These pseudoaneurysms commonly form after repeated vascular access from the same site, and the incidence of pseudoaneurysms in AV grafts increases with the age of the graft.
Aneurysms commonly form in atherosclerotic arteries as a mechanism to bypass an area of decreased arterial flow. True aneurysms typically take longer periods of time to develop, on the scale of months to years. Pseudoaneurysms, on the other hand, often develop rapidly following an injury to the affected artery that results in disruption of the vessel wall without complete rupture. The area of the artery that sustained trauma is replaced by an organized hematoma with a fibrous wall resulting in localized dilatation of the vessel.
Patients will often report a slow growing or painful mass. Many will experience sensory disturbances in a dermatomal distribution if the aneurysm is compressing a nearby nerve. On physical exam, the provider will often be able to palpate a mass, which is only pulsatile in about 50% of cases. There may also be changes in the overlying tissue, such as local erythema, eschar formation, skin necrosis, or erosion. A history of preceding trauma, intravenous drug use, or intermittent hemodialysis access to the area should prompt consideration of this diagnosis.
The differential diagnosis for a patient presenting with a slowly expanding and painful mass is fairly broad, and will often require advanced imaging to make a definitive diagnosis. Other than pseudoaneurysm, clinicians must also consider other vascular abnormalities such as true aneurysm, arterial fistula, and expanding hematoma. Infectious causes such as abscess or infected hematoma can present similarly, often with overlying cellulitis and warmth. Inflammatory causes such as vasculitis can also present similarly, although this would likely present as a more chronic rather than acute problem. A foreign body with granuloma formation can present similarly, and should be considered especially if a penetrating injury occurred, such as a laceration with glass, metal, or wood. Finally, neoplastic causes should also be considered, such as angioma, neuroma, and soft tissue lipoma.
Laboratory testing is not necessary in making the diagnosis of pseudoaneurysm. However, studies such as a complete blood count, sedimentation rate, and c-reactive protein can be helpful for consultants, especially if the pseudoaneurysm will be managed surgically. The diagnosis is confirmed by imaging, and several different modalities can be used.
Doppler ultrasound is a useful study that does not subject the patient to any contrast or radiation, and it can be performed quickly at the bedside. The pseudoaneurysm will appear as a hypoechoic cystic structure adjacent to the artery. Color doppler may show the classic “yin-yang sign” which is a swirling, alternating color motion within the aneurysm. The most specific ultrasound finding for a pseudoaneurysm is a communicating channel between the artery and sac with a “to and fro” waveform on duplex ultrasound.8 Ultrasound has been reported to have a sensitivity of 94% with a specificity of 97% in detecting pseudoaneurysms of the femoral artery after cardiac catheterization, but it has not been studied extensively at other sites and is operator dependent. Regardless, it remains a viable option when evaluating these lesions.
While traditional angiography remains the “gold standard” for this diagnosis, with advances in CT technology, CT angiography has become an extremely valuable tool in the diagnosis of pseudoaneurysms. CT angiography can be obtained quickly and is useful for surgical planning. CT angiography can also detect alternative diagnoses and injuries, as well as give information on blood flow to the pseudoaneurysm. It can also detect active extravasation from the pseudoaneurysm. CT angiography has been reported to have a sensitivity of 95.1% and specificity of 98.7% in detecting pseudoaneurysms in the proximal extremities, making it an excellent diagnostic study that can be obtained in the ED.
MRI is another imaging modality that can be used in diagnosing pseudoaneurysms. While MRI does not expose the patient to ionizing radiation or iodinated contrast, it is a time- and resource-intensive test that requires patient cooperation. The sensitivity and specificity in detecting pseudoaneurysms are similar to that of CT angiography, making it an effective diagnostic tool. Nonetheless, the time required to obtain this study is often a limiting factor.
Once the diagnosis has been made with advanced imaging, surgical consultation is warranted. If there are no signs of extravasation on imaging and the patient is hemodynamically stable, operative planning can often be arranged as an outpatient. However, more urgent surgical intervention is indicated if there is active extravasation, significant erosion of the overlying skin, evidence of infection, or signs of compartment syndrome of the affected extremity.
Emergency physicians must have a low threshold for advanced imaging if this diagnosis is suspected, as the consequences of a missed diagnosis are severe and can be limb threatening. Failure to diagnose an expanding pseudoaneurysm and arrange surgical follow up can lead to compartment syndrome and permanent neurologic deficits. While the overall incidence of peripheral artery pseudoaneurysm is low, missing this diagnosis has severe consequences for patients and should always be considered in the evaluation of a mass in the extremity, especially in the setting of recent trauma or arterial instrumentation.
Authored by MIchael Klaszky, MD
Posted by Matthew Scanlon, MD
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