Puncture Site Hematoma

Often presents with local pain, swelling, and subcutaneous ecchymosis. Hematomas occurring at the puncture site of the fistula vein may also be accompanied by enhanced pulsation of the fistula vein at the distal end of the hematoma and weakened thrill.

Ultrasound Manifestations: Hypoechoic or anechoic areas around the blood vessel, which may be located anterior to, posterior to, or surrounding the vessel. The local blood vessel may be significantly compressed (attention should be paid to comparison with pre-puncture findings).

Management Strategies:
(1) Small hematomas can be managed with local compression and ice application, allowing them to absorb spontaneously;
(2) In cases of continuous active bleeding, significant luminal compression, excessively high fistula tension, or even blood stasis, re-puncture at an alternative site is feasible. A balloon can be used for internal vascular compression to stop bleeding and reshape the lumen;
(3) For large hematomas complicated by severe pain or significant compression on surrounding tissues, surgical evacuation may be considered.

Vascular Spasm

Often caused by irritation of the vascular wall by endoluminal instruments or inherent vascular sensitivity to stimuli, with arterial spasm being more common.

Ultrasound Manifestations: Compared with preoperatively, the vascular diameter is locally or segmentally narrowed, appearing beaded or thread-like, with slowed or even interrupted blood flow.

Management Strategies:
(1) Mild vascular spasm requires no special treatment and can resolve spontaneously;
(2) Severe vascular spasm that impairs blood flow and carries a high risk of secondary thrombosis: During the procedure, 30 mg papaverine or 100–300 μg nitroglycerin (use with caution in hypotensive patients) can be diluted and injected locally into the blood vessel to relieve spasm. Alternatively, balloon dilation of the spasmodic vascular segment can be performed under low pressure (usually 1–2 atm). Caution should be exercised for recurrent spasm or secondary spasm of adjacent blood vessels, which may require multiple interventions.

Vascular Dissection

Often caused by improper operation, severe intrinsic vascular lesions, and difficulty in clearly identifying the vascular wall in occlusive lesions, which can lead to vascular lumen stenosis or even thrombosis.

Ultrasound Manifestations: Two-dimensional ultrasound in the short axis can detect vascular wall stratification; in the long axis, a band-like structure within the lumen separating the lumen is observed. Color Doppler flow imaging can show double-layered blood flow signals in the same blood vessel.

Management Strategies:
(1) The guidewire should be immediately withdrawn back into the true vascular lumen, and repositioned for passage;
(2) A balloon can be used to appose the dissection under low pressure, followed by re-evaluation with ultrasound after 3 minutes;
(3) Severe vascular dissection can lead to blood stasis in the false lumen compressing the true lumen. A balloon can be used to fenestrate the intima to communicate the true and false lumens and restore blood flow in the true lumen;
(4) Stent implantation may be performed if necessary.

 Vascular Rupture

Often caused by the guidewire or catheter puncturing the vascular wall, oversized balloon selection, etc. It is characterized by rapid local swelling along the vascular course, which spreads to the surroundings.

Ultrasound Manifestations: Interruption of the continuity of the vascular intimal line, and newly appeared hypoechoic or anechoic areas around the vessel. In cases of active bleeding, color Doppler flow imaging shows color blood flow signals entering the area.

Management Strategies:
(1) If a guidewire or catheter is found outside the vessel during the procedure, the guidewire and catheter should be immediately withdrawn back into the vascular lumen. If ultrasound does not detect blood flow signals spreading outside the vessel, the operation can be continued to find the true lumen;
(2) For a large rupture with continuous bleeding, the upstream artery should be compressed to reduce the fistula pressure, and a balloon should be used to compress the rupture under low pressure. Re-evaluate with ultrasound every 3–5 minutes, which can be repeated;
(3) It is necessary to relieve the downstream vascular stenosis as soon as possible to reduce the fistula pressure;
(4) If repeated compression is ineffective, covered stent implantation or surgical repair may be considered.

 Pseudoaneurysm

It is a pulsatile cystic hematoma formed by blood being encapsulated by surrounding fibrous tissue after vascular rupture, without the three-layer structure of the intima, media, and adventitia of the blood vessel wall.

Ultrasound Manifestations:
(1) Anechoic mass adjacent to the blood vessel with the disappearance of local vascular wall structure;
(2) A shunt orifice exists between the blood vessel and the mass, in which bidirectional blood flow can be detected, and red-blue alternating blood flow signals (i.e., “yin-yang sign”) in the aneurysm sac;
(3) Due to the back-and-forth flow of blood between the aneurysm sac and the parent vessel, a characteristic “to-and-fro” blood flow spectrum is formed.

Management Strategies:
(1) Timely diagnosis and rapid compression can close most pseudoaneurysms;
(2) Endovascular balloon compression can be combined with external compression on the skin surface. Evaluate the blood flow in the aneurysm sac and the formation of thrombosis by ultrasound every 3–5 minutes. If there is no blood flow signal and the aneurysm sac is completely filled with thrombus, the compression is successful, and it can be repeated 3–4 times.
(3) If simple compression fails, ultrasound-guided injection of thrombin or topical use of lyophilized human fibrin adhesive [50] can be adopted, which is suitable for cases with small rupture, long aneurysm neck, and small aneurysm sac. During injection, care should be taken to avoid the drug entering the artery and causing arterial embolism.
(4) Covered stents and surgical procedures can be used for cases where compression or occlusion fails.

 Acute Thrombosis

Often caused by vascular intimal injury, prolonged balloon occlusion, and insufficient anticoagulation. When the thrombus occludes the downstream fistula vein, it can lead to increased vascular tension, enhanced fistula pulsation, and weakened thrill. If the upstream artery is occluded, both the pulsation and thrill of the entire fistula will be weakened.

Ultrasound Manifestations: Newly appeared hypoechoic lesions in the vascular lumen, which may adhere to the vascular wall and present as irregular masses or patches.

Management Strategies:
(1) A small amount of thrombus requires no special treatment;
(2) For a large amount of thrombus, a large-caliber catheter or vascular sheath can be used for aspiration combined with manual compression and local thrombolytic drugs;
(3) Systemic thrombolysis has a poor effect and is not recommended;
(4) In the presence of vascular rupture, continuous local infusion of thrombolytics should be extremely cautious to avoid extravasation of blood and thrombolytic drugs;
(5) Surgical thrombectomy may be considered if necessary.

 Balloon Rupture

Common when the dilation pressure exceeds the burst pressure or when treating severely calcified blood vessels. The main manifestations of balloon rupture include no increase in pressure inside the balloon after injecting normal saline with a pressure pump, uneven inflation or unstable pressure of the balloon, and blood can be seen upon aspiration. In case of transverse rupture, the ultrasound image will show the balloon divided into two segments.

Management Strategies:
(1) Slowly pull the ruptured balloon to the vascular sheath opening, and gently pull to attempt direct removal through the sheath;
(2) Difficulty in removal often indicates that the balloon may have ruptured transversely with the broken end forming an umbrella-like structure. Do not pull violently. The broken balloon can be removed by interventional methods or surgical operation.

 Guidewire and Catheter Fracture

Often caused by repeated excessive shaping, knotting, excessive traction, and improper manipulation of the guidewire or catheter. Ultrasound can detect the fractured ends of the guidewire or catheter remaining in the blood vessel.

Management Strategies:
(1) Immediately block blood flow to prevent the fractured guidewire or catheter from drifting;
(2) A gooseneck snare or a vena cava filter snare can be used to capture the fractured ends of the guidewire or catheter;
(3) During the capture procedure, violent manipulation must be avoided to prevent the fractured ends from scratching or puncturing the blood vessel;
(4) If interventional capture is difficult, surgical operation is safer.