Several catheterization types are routinely performed in veterinary and human medicine. Among them, intravenous (IV) catheterization is essential to manage veterinary patients; it is one of the most common medical procedures to administer medications and fluids. When removing a peripheral venous catheter, these devices should not be cut, twisted, or overmanipulated to avoid breakage (8). However, ruptures might still occur despite a meticulous removal technique. When an IV catheter breaks, the detached distal part could migrate to the central venous system, heart, and pulmonary circulation (3,14).

In both human and veterinary medicine, several cases of catheter fragment embolism have been reported (3,6-8,14,15,17,18). Foreign bodies in the vascular system involve a high risk of embolization, perforation, and infection (13). They may also cause severe complications, such as lung abscesses, pulmonary embolism, dysrhythmias, endocarditis, cardiac perforation, sepsis, and even death (12,14). Various techniques, such as surgery, non-surgical removal, and interventional procedures, have been introduced in human and veterinary medicine to retrieve foreign bodies in the right ventricle, vena cava, or pulmonary artery (1,5,9-12).

Several reports described localizing the catheter fragment with different imaging modalities in dogs, including radiography, fluoroscopy, ultrasonography, and computed tomography (CT) (6,15,17). Regarding ultrasound to localize a catheter piece in dogs, a study reported that this modality is not appropriate due to the similar appearance of the catheter and blood vessel, thereby hindering fragment identification (6). In contrast, another report mentioned that the catheter fragment was properly visualized using ultrasound with a conventional linear probe, resulting in successful surgery (17).

This report describes the use of ultrasound with a high-frequency small-footprint linear array transducer (also called a hockey-stick probe) to localize the catheter fragment in the cephalic vein of a toy poodle dog.

A 2-year-old, 2.6 kg, intact female toy poodle presented to the clinic due to a recent onion intake, and the owner requested to induce emesis. The dog appeared bright, alert, and responsive, with no contributory clinical signs. A 24 gauge IV catheter was inserted into the right cephalic vein, and 50 mg/kg of tranexamic acid was administered through the IV line. Emesis was successfully induced with the drug injection. No adverse effects of the medicine, including tonic-clonic seizure, were observed. At the time of discharge, the 24-gauge IV catheter was removed; however, the retrieved catheter was markedly shorter than expected. A catheter breakage was assumed; thus, a tourniquet was applied proximally to the right elbow. Palpation did not aid in localizing the catheter fragment. An ultrasound scan was performed with a high-frequency linear probe (18–4 MHz, surface area: 6 × 1 cm, Fig. 1A), eL18-4 (Philips Ultrasound Inc.; Shanghai, China). However, due to the linear probe’s relatively large scanning area and the uneven surface of the patient’s forelimb, the cephalic vein and broken catheter were poorly visualized. Thus, a high-frequency small-footprint linear array probe, called a hockey-stick probe (15–7 MHz, surface area: 3 × 1 cm, Fig. 1B), L15-7io (Philips Ultrasound Inc.; Shanghai, China) was used. The intravenous catheter fragment appeared as two parallel hyperechoic lines of approximately 1.2 cm in length in the lumen of the right cephalic vein. The location of the catheter fragment was confirmed and marked on the skin before venotomy. Another IV line was inserted into the left cephalic vein.

Figure 1. (A) The high-frequency linear transducer (18–4 MHz) first used in this case report. The scanning area is 6 × 1 cm. (B) High-frequency small-footprint linear array transducer, also called hockey-stick probe (15–7 MHz). Its reduced contact area (3 × 1 cm) allowed us to scan the narrow and uneven surface of the right forelimb.

The ultrasound with the hockey-stick probe was repeated immediately before catheter removal to confirm the fragment’s location. This scan was performed in a sterile manner following the surgical site preparation. The fragment had migrated proximally, approximately 5 cm from the marked line (Fig. 2).

Figure 2. The intravenous catheter fragment appeared as two parallel 1.2 cm hyperechoic lines (arrows at the proximal and distal ends of the fragment) in the lumen of the right cephalic vein (double arrow). A high-frequency small-footprint linear array transducer was used.

After the re-localization of the fragment, venotomy was performed with minimal manipulation of the patient to prevent further migration of the catheter piece. A 2.5 cm skin incision was performed at the expected fragment location. The cephalic vein was identified and carefully isolated, and the catheter was located within the vessel. Curved Mosquito forceps were used to hold the fragment in position, and a stab incision of the vein was performed at the level of the proximal margin of the fragment using a number 15 blade (Fig. 3A). Additional Mosquito forceps were used to grasp the proximal end of the catheter piece and retrieve it (Fig. 3B). The applied tourniquet was released, and the vascular puncture was compressed with sterile gauze for approximately 3 min to achieve complete hemostasis. The subcutaneous tissue and skin were closed routinely with 4-0 polydioxanone II (Ethicon, Raritan, NJ, USA). The anesthetic infusion and patient’s recovery were uneventful.

Figure 3. (A) The proximal tip of the catheter fragment (arrow) was visible after the stab incision of the cephalic vein (dashed arrow). Mosquito forceps were used to grasp the fragment and prevent further migration. (B) The catheter fragment was retrieved through venotomy.

Stitches were removed ten days following surgery, and no significant clinical sign related to the treatment was observed. Discomfort or swelling was not identified at the 2 month follow-up.

In the present case, the IV catheter was noted to be broken upon removal. The fragment was located clearly with ultrasound using a hockey-stick probe, and surgically removed without complications.

A hockey-stick probe is suitable for musculoskeletal and peripheral vascular regions and is mainly used in intraoperative procedures (20). In human medicine, the hockey-stick probe is used to visualize vessels in neonates and pediatric patients (2,16). It is also widely used in veterinary medicine for areas with a limited surface, and to evaluate ligaments and tendons due to its high resolution and ability to visualize the near field as well as its reduced contact area as compared to a general linear probe (4,10). Our patient was smaller than the patient in the previous veterinary case report that successfully used ultrasound (17); thus, the conventional linear probe was inappropriate to visualize the catheter fragment under the uneven surface of the patient’s forelimb since the contact was insufficient. Instead, the hockey-stick probe was the most appropriate option because it could localize the near-field foreign body in this narrow and uneven location owing to its sufficiently high frequency and reduced area. Therefore, the hockey-stick probe may be an optimal option to visualize a catheter fragment, especially in small breed dogs, if it is not detected with a conventional linear probe.

As we performed an additional ultrasound prior to the skin incision, we noted the migration of the catheter, approximately 5 cm proximal to the line previously drawn on the skin. In humans, a study reported that ultrasound ensured a prompt localization, preventing the fragment migration to the central veins or heart and further complications (19). In this case, a rapid assessment was possible with ultrasound, allowing treatment without complications. However, migration of the fragment was noted through repeated ultrasound scans. In the reports using CT and ultrasonography in dogs, an extended incision was necessary to retrieve the catheter fragment, likely due to peripheral migration after localization (6,17). Thus, we suggest performing an additional ultrasound immediately before surgery to allow a minimal skin and small vein incision.

Despite the usefulness of ultrasound for a peripheral catheter fragment, a centrally migrated piece might not be detected with this technique. In this case, other modalities may be needed for localization, such as radiography, fluoroscopy, or CT (6).

In conclusion, ultrasonography with a hockey-stick probe may be an ideal imaging modality to locate a catheter fragment in a peripheral vessel of small breed dogs. Moreover, an additional ultrasound immediately before surgery can determine the exact location of the fragment in case of catheter migration.

The authors have not received any specific grant for this research from any funding agency in the public, commercial, or not-for-profit sectors.

None.

The authors have no conflicting interests.