Iatrogenic Arterial Pseudoaneurysm

Iatrogenic arterial pseudoaneurysm is a contained arterial wall defect, with a sac communicating with the artery, caused by a diagnostic or therapeutic procedure. It can occur in any artery that has been punctured, cannulated, dissected, biopsied or sutured.

Common sites and causes are:

• Femoral artery after catheterisation (the commonest).
• Radial and brachial arteries after catheterisation, arterial lines and blood gas sampling.
• Renal arteries after percutaneous biopsy, nephrostomy and partial nephrectomy.
• Hepatic, splenic, pancreaticoduodenal and gastroduodenal arteries after liver biopsy, biliary drainage, cholecystectomy, pancreatic surgery and endoscopic procedures, often with pancreatitis or abscess.
• Subclavian, carotid and internal jugular related arteries after central line insertion.
• Intercostal and internal mammary arteries after chest drain or surgery, and anastomotic sites after bypass graft or transplant surgery.

Frequency varies by procedure. Radial pseudoaneurysm complicates about 0.05 to 0.5% of radial catheterisation. Renal biopsy causes pseudoaneurysm or arteriovenous fistula in a few per cent, and most close spontaneously. Visceral pseudoaneurysm is uncommon but carries a high rupture risk of about 75% when untreated in some series.

Pathophysiology.

Partial or full thickness arterial injury lets blood escape into surrounding tissue, which contains it by a haematoma wall. Pulsatile flow through the neck sustains and enlarges the sac.

Contributing factors are anticoagulation and antiplatelet therapy, infection, pancreatic enzymes (which digest the wall in pancreatitis), anastomotic suture line tension or infection, and repeated punctures.

Visceral lesions rupture into the peritoneum, retroperitoneum, bowel, biliary tree or urinary tract, causing haemorrhage, haemobilia, melaena or haematuria.

Presentation depends on the site:

• Superficial arteries (femoral, brachial, radial): pulsatile painful mass, bruit, expanding haematoma, neuropathy, limb ischaemia.
• Renal: delayed haematuria, flank pain, falling haemoglobin, hypertension.
• Hepatic and biliary: haemobilia with right upper quadrant pain, jaundice and gastrointestinal bleeding (Quincke triad).
• Splenic, gastroduodenal and pancreatic: abdominal pain, gastrointestinal bleeding, shock from rupture.
• Chest and neck: pulsatile swelling, haemothorax, stridor or hoarseness from compression, stroke from embolisation.
• Infected lesions: fever, sepsis, erythema and purulence.

Many are asymptomatic and discovered on imaging.

• Duplex ultrasound for superficial arteries (the to-and-fro waveform in the neck, sac size, neck dimensions) and for renal and hepatic lesions.
• CT angiography (arterial phase) is the key test for deep lesions: contrast filled sac with arterial phase enhancement, extravasation, haematoma, relation to organs. Magnetic resonance angiography is an alternative.
• Catheter angiography for diagnosis and treatment of visceral lesions, and in unstable patients.
• Blood tests: haemoglobin, platelets, coagulation screen, creatinine, amylase and lipase (pancreatic lesions), liver tests, blood cultures (three sets before antibiotics) and inflammatory markers when infection is suspected, and group and cross-match.
• Endoscopy for gastrointestinal bleeding and haemobilia.

Differential diagnosis.

• Haematoma and abscess without a sac, and arteriovenous fistula.
• True aneurysm and tumour with vascular enhancement.
• Bleeding peptic ulcer and other sources of gastrointestinal bleeding, and renal or hepatic tumour.
• Biliary or urinary tract stone and infection.

Unstable patient. Resuscitate with crystalloid and blood (red cells, plasma and platelets in a ratio near 1:1:1 in massive bleeding), calcium chloride 1 g intravenously for each 4 units, and tranexamic acid 1 g intravenously over 10 minutes then 1 g over 8 hours.

Reverse anticoagulation as needed:

• protamine 1 mg for each 100 units of heparin given in the previous 2 to 3 hours (maximum 50 mg, given slowly)
• four factor prothrombin complex concentrate 25 to 50 units/kg (by INR) with vitamin K 5 to 10 mg intravenously for warfarin

Proceed at once to angiographic embolisation or surgery.

Treatment by site.

• Femoral and other superficial arteries (radial, brachial):
  • Observe lesions under 2 cm that are asymptomatic, with repeat duplex in 1 to 2 weeks.
  • Ultrasound directed thrombin injection: thrombin 1000 units/mL injected in 0.1 mL aliquots into the sac under duplex until flow stops (usual total 100 to 1000 units; avoid a short or wide neck, infection or limb ischaemia). In the radial and brachial arteries, take special care because of small vessel size and embolisation, and check distal flow afterwards.
  • Ultrasound directed compression for 10 minutes at a time to a total of 30 to 60 minutes, when thrombin is unsuitable. Success is lower with anticoagulation.
  • Surgery (suture, patch or interposition graft) for rupture, infection, nerve compression, skin necrosis or failure of other methods, and for brachial pseudoaneurysm with median nerve compression.
• Renal arteries: observe small, asymptomatic lesions under 2 cm after biopsy (most resolve). Selective coil embolisation for symptoms, haematuria, falling haemoglobin, growth, or size over 2 cm, with as little loss of renal parenchyma as possible.
• Hepatic, splenic, gastroduodenal and pancreatic arteries:
  • Treat all visceral pseudoaneurysms because of the rupture risk.
  • Transcatheter coil embolisation is first line, with coils placed on both sides of the neck (sandwich technique) or within the sac; liquid embolic agents, plugs or covered stents are alternatives, with covered stents reserved for main trunks where flow must be preserved.
  • Surgery (ligation, resection or repair) when embolisation fails or the lesion is infected or ruptured. After splenic embolisation, monitor for infarction and abscess.
• Subclavian, carotid and chest wall arteries: covered stent, coil embolisation or surgical repair by site, in a vascular centre. Intercostal and internal mammary lesions are treated by embolisation.
• Anastomotic pseudoaneurysm after graft surgery: re-operation with revision, or covered stent in unfit patients; suspect infection and take cultures.

Infected pseudoaneurysm. Draw cultures first. Vancomycin 25 mg/kg intravenously as a loading dose, then 15 to 20 mg/kg every 8 to 12 hours (trough 15 to 20 mg/L), with piperacillin and tazobactam 4.5 g intravenously every 6 hours, adjusted to cultures, and fluconazole or liposomal amphotericin B 3 to 5 mg/kg daily when Candida is isolated. Excision with debridement and reconstruction, and at least 6 weeks of antibiotics after source control. Do not use thrombin or covered stents for active infection, except as a bridge.

Antithrombotic therapy. After covered stent placement, aspirin 75 to 100 mg and clopidogrel 75 mg daily for 3 months, then aspirin alone. After coil embolisation, resume aspirin when bleeding risk allows. Restart anticoagulation only after the sac is secured.

Prevention. Ultrasound directed access, the smallest suitable device, appropriate compression, correct selection of closure device, and careful monitoring after solid organ biopsy (haemoglobin and urine for 24 hours). Treat pancreatitis and intra-abdominal sepsis early.

Monitoring. Duplex or CT angiography at 1 to 2 weeks and at 1, 3 and 12 months after treatment (visceral lesions can recur or develop new sacs). Haemoglobin and clinical review for bleeding. Organ function after embolisation (creatinine after renal, liver tests after hepatic).

Referral and escalation. Refer every pseudoaneurysm to a vascular surgeon or interventional radiologist the same day for visceral or deep lesions, and within 24 hours for superficial lesions. Immediate activation of the bleeding team for shock, expanding mass, haemobilia or gastrointestinal bleeding.

Special groups.

• Pregnancy: embolisation with abdominal shielding and obstetric input; avoid warfarin and direct oral anticoagulants.
• Liver or kidney transplant recipients: pseudoaneurysm at the anastomosis threatens the graft, so give urgent specialist review.
• Kidney impairment: use contrast sparingly with hydration, but do not withhold imaging when bleeding is possible.
• Region specific: infection and intravenous drug use are frequent causes of superficial lesions, so test for HIV, syphilis and tuberculosis, and take cultures.