Percutaneous Drainage Procedures


Fig. 11.1

Both superficial epidermis and dermis can be evaluated and appear as a hyperechoic layer on ultrasound. Subcutaneous tissue lies just deep to the dermis and can be visualized as hypoechoic fat lobules with hyperechoic septae. The dense fibrous membrane is the fascial layer and usually appears as a linear hyperechoic layer



Indications


Patients with localized erythema, increased warmth, swelling, and/or discomfort of an affected body part should undergo sonographic imaging to identify pathology such as cellulitis and abscess (Fig. 11.2). In the study by Squire et al., out of 18 cases in which clinical exam did not suggest abscess, but POCUS demonstrated evidence of anechoic fluid collection, ultrasound was accurate in 17/18 (94%) of cases confirmed by incision and drainage. This suggests that patients who are found to have anechoic fluid collections by POCUS concerning for abscess should undergo incision and drainage, even if the clinical examination suggests only superficial cellulitis without abscess [2].

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Fig. 11.2

Note the heterogeneous fluid contents with mixed echogenicities within the abscess (arrow). There is also associated cobblestoning seen in the upper left portion of the image, signifying cellulitis (arrow heads) overlying the abscess


Contraindications


The location of concern should be evaluated with POCUS to ensure that no neurovascular structures lie in the region of interest, which would in turn warrant an alternative method for incision and drainage [2]. In addition, color Doppler can be used to ensure there is no evidence of a necrotic or cancerous lymph node, aneurysm, or pseudoaneurysm (Figs. 11.3 and 11.4). Discretion should be used in bedside incision and drainage of abscess in patients on anticoagulation or with known coagulopathic states. Abscess located in muscle, known as pyomyositis, can present similarly with erythema, pain, swelling, and tenderness on palpation of the affected region (Fig. 11.5). Pyomyositis is generally drained in the operating room.

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Fig. 11.3

This is an example of a metastatic cancer lymph node. The usual architecture of a normal lymph node is disrupted. There is no central hilar blood flow. The blood flow is now on the periphery. There is no change in shape with graduated compression with the ultrasound transducer to suggest fluid contents


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Fig. 11.4

(a) This superficial circular mass is pulsatile with blood contents swirling. (b) With color Doppler, you see the swirling flow of the blood more clearly. This example illustrates the importance of using bedside ultrasound before an incision and drainage should be performed. It also shows the importance of using color Doppler to identify blood flow


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Fig. 11.5

Note the heterogeneous fluid collection that is seen within the muscle along with significant inflammation of the muscle suggesting pyomyositis


Equipment and Probe Selection


The high-frequency (12–7 MHz) linear array probe is ideal for evaluation of superficial structures. Color Doppler can aid in identifying surrounding neurovascular structures. One percent lidocaine with or without epinephrine is a commonly used anesthetic. Chlorhexidine, a needle driver for blunt dissection, and a #11 blade scalpel should be readily available prior to starting the procedure. In more delicate areas or for smaller fluid collections, an 18- or 20-gauge needle attached to a 10 mL syringe can be used as an alternative to the #11 blade scalpel.


Of note, if the subcutaneous abscess is in a location of thick subcutaneous fat, such as the buttock, thigh, or abdominal wall, use of the low frequency curved array probe for deeper imaging may be helpful.


Preparation and Pre-procedural Evaluation


The patient should be positioned such that the affected area is easily accessible to the provider. Topical anesthetic, such as lidocaine-epinephrine-tetracaine gel, can be used over the affected area to minimize discomfort.


Procedure


Begin scanning away from the affected area to evaluate the patient’s normal anatomy. Scan the entire length of the affected area in both sagittal and transverse planes using the linear array probe. An abscess will appear as an anechoic fluid collection with hyperechoic contents often with posterior acoustic enhancement. This can be distinguished from cellulitis, which has a cobblestone appearance without fluid collection (Fig. 11.2). Gentle graded compression ensures a loculated fluid collection is not missed, and color Doppler flow can be used to confirm lack of vascularity (Fig. 11.6). Furthermore, graded compression may result in swirling of abscess contents. Comparison to the contralateral side can be useful. If a fluid collection is located, the boundaries, depth from the tissue surface, and estimated size of the cavity should be noted. The sonographic appearance of a hematoma is non-specific and is challenging to differentiate from an abscess [3].

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Fig. 11.6

It is normal to see scant blood flow in the periphery of an abscess, secondary to infection and inflammation. There is no central or pulsatile flow in this abscess, which makes it safe for incision and drainage


Once the abscess and surrounding anatomy have been visualized, the affected area should be cleaned with chlorhexidine and subsequently anesthetized. The probe should be covered with a Tegaderm to minimize transmission of nosocomial infections, and gel should be placed over top of the probe. Under ultrasound guidance, a small stab incision should be made using a #11 blade scalpel, and blunt dissection with a needle driver can break up loculated fluid collections. Extensive abscesses may require irrigation with normal saline to aid in breakdown of loculations. In anatomically challenging locations or for small fluid collections, needle aspiration using an 18- or 20-gauge needle attached to a 10 mL syringe can be used as an alternative to using the #11 blade scalpel (Figs. 11.7 and 11.8). Ultrasound should be used after incision and drainage is complete to verify complete evacuation of the abscess cavity.

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Fig. 11.7

(a) In sensitive areas, such as the scrotum, or if the abscess is small, needle aspiration may be preferred. In this image, you see the needle in short axis as an echogenic dot (arrow) (out-of-plane technique). (b) With real-time ultrasound guidance and imaging, you can see the actively shrinking abscess as purulence is aspirated


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Fig. 11.8

Here is another example of needle aspiration of a left breast abscess. The dotted circle highlights the abscess in the left breast, and the arrows denote the length of the needle


Complications


Color Doppler can aid in the identification of neurovascular structures, lymph nodes, solid masses, etc. In addition, ultrasound should be used after the procedure to verify complete evacuation of the abscess cavity. A partially drained abscess may result in the need for further intervention.


Pearls and Pitfalls





  1. 1.

    The use of color Doppler during the initial evaluation and real-time ultrasound guidance during the procedure can help avoid neurovascular complications.


     

  2. 2.

    Purulent material in the abscess cavity may appear isoechoic, and therefore, the use of graded compression and color Doppler can help in identification of an abscess cavity (Fig. 11.9).


     

  3. 3.

    Use of a larger 18-gauge needle is recommended for needle aspiration procedures, as purulent material may be difficult to aspirate when using a smaller gauge needle.


     

  4. 4.

    When purulent material is too viscous for needle aspiration or if the abscess cavity is too large to adequately evaluate using needle aspiration, a #11 blade scalpel can be used to create a small stab incision to allow drainage.


     

  5. 5.

    Be aware that necrotic lymph nodes appear similar to an abscess. Use gray-scale imaging and color Doppler imaging to evaluate for necrotic lymph nodes before performing an incision and drainage, and incision and drainage of necrotic lymph nodes is discouraged.


     

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Fig. 11.9

Especially in areas of high-fat content, such as the buttocks, thighs, and, for some patients, abdominal wall, abscesses can appear isoechoic and subtle to identify under ultrasound. Note that this abscess does not have the usual obvious characteristics of a classic abscess. Compression of the area with the transducer may cause swirling of the contents to reveal pus


Integration into Clinical Practice


Ultrasound-guided incision and drainage of abscess and hematoma provide definitive treatment. The features to distinguish abscess from cellulitis are easily learned and can help guide management decisions about the need for incision and drainage. Furthermore, ultrasound-guided drainage provides real-time visualization of the surrounding neurovascular structures which helps reduce the incidence of complications.


Evidence


Ultrasound-guided abscess drainages are technically uncomplicated and minimally invasive. In a study by Kjær et al., subcutaneous truncal abscesses were treated successfully in 93% of their patients [4]. This approach yielded high patient satisfaction and was well-tolerated with short healing times.


Ultrasound-guided breast abscess drainages have replaced open treatment of breast abscesses, with 97% resolution rate in puerperal abscesses and 81% resolution rate for nonpuerperal abscesses [5]. Needle drainage under ultrasound decrease pain and scar formation. The evidence for using ultrasound to directly guide abscess drainage makes it suitable for outpatient settings.



Key Points






  • POCUS for the diagnosis or confirmation of a subcutaneous abscess is recommended in addition to physical examination due to concern of a suspected abscess being a mass, lymph node, aneurysm, etc.



  • For smaller abscesses, it is reasonable to use a large gauge needle to attempt aspiration and proceed to incision if necessary.



  • In-plane technique is always preferred, if possible, to ensure the needle tip does not injury nearby structures.



  • Always use color Doppler to evaluate abscesses to identify vascular or blood flow within the fluid collection.


Drainage of Subcutaneous Hematomas


Advantages of Ultrasound Guidance


POCUS is a useful tool to differentiate soft tissue swelling from hematoma, although differentiation of hematoma from abscess can be more challenging. Differentiation between a hematoma and an abscess will depend more on the clinical picture. Patients can also present with an infected hematoma, which may present with signs and symptoms of an abscess over an area of previous trauma or if the patient is prone to bleeding.


Anatomy


Pay close attention to surrounding structures, especially vasculature that may have been injured to cause the hematoma. After drainage of the hematoma that may have tamponade feeding vessels, bleeding may commence from the incision. It is also important to note the sonographic characteristics of the hematoma. Fresh blood may appear hyperechoic or isoechoic to the surrounding subcutaneous tissue, and as blood products break down over time, the blood may become anechoic with possible fibrin strands (Fig. 11.10).

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Fig. 11.10

This 4-day-old hematoma shows some heterogeneous contents, but it is mostly anechoic. It is important to incorporate clinical symptoms into diagnosing hematomas. As you can see with this image, this hematoma can certainly be confused for an abscess, but note there is no associated overlying cellulitis, which may give a clue to it being a hematoma


Indications


Patients with an area of fluctuance, induration, erythema, increased warmth, swelling, and/or discomfort should undergo ultrasound imaging to evaluate for underlying pathology. The differentiation of abscess and hematoma is largely clinical, with only very subtle differences by ultrasound. Hematoma should be clinically suspected in patient who present with history of trauma, easy bruising, thrombocytopenia, coagulopathy, anticoagulation, or recent surgery, although abscess remains on the differential diagnosis. When the pressure in the hematoma cavity exceeds that of the dermal and subdermal capillaries, there is increasing potential for overlying skin necrosis.


Contraindications


The contraindications for this procedure are very similar to those for draining abscesses. POCUS should be used to ensure that no neurovascular structures lie in the region of interest, which would warrant an alternative method for incision and drainage [2]. Use color Doppler to ensure the area in question is not a necrotic lymph node, aneurysm, or pseudoaneurysm. Discretion should be used when performing bedside incision and drainage of a hematoma in patients on anticoagulation or with known coagulopathic states, as bleeding is a concerning potential risk; patients should be counseled regarding the potential risk of bleeding prior to starting the procedure. Laboratory testing such as complete blood count to check platelet count and a coagulation panel (PTT and PT/INR) may be helpful prior to starting the procedure to further assess for bleeding risk.


Equipment and Probe Selection


As with evaluation of most superficial structures, the high-frequency (15–7 MHz) linear array probe is ideal. Color Doppler over the area in question can help identify surrounding neurovascular structures. One percent lidocaine with or without epinephrine is commonly used for anesthesia, although the use of lidocaine with epinephrine can help minimize potential bleeding if not otherwise contraindicated. Chlorhexidine, a needle driver for blunt dissection, a package of 4 × 4 inch gauze pads, and a #11 blade scalpel should be readily available. Compression dressing or an ACE bandage should also be considered for adequate pressure over the drained hematoma, since the hematoma may continue to ooze or re-bleed. The viscous nature of hematoma generally contraindicates use of needle drainage, but it is reasonable to start with a needle aspiration and convert to incision and drainage if necessary (Figs. 11.11 and 11.12).

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Fig. 11.11

Although the viscous nature of hematomas may preclude needle drainage, it is always reasonable to start with a needle drainage and convert to an incision if necessary. This is an example of a long-axis or in-plane technique, with visualization of the needle tip and the entire length of the needle that is in the patient. This is the preferred method for ultrasound-guided procedures. The dotted line outlines the needle and needle tip


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Fig. 11.12

B-mode image of echogenic needle in a post-procedural groin hematoma (in-line approach). Aspiration was done to determine if any abscess was present


Preparation and Pre-procedural Evaluation


The patient should be positioned such that the affected area is easily accessible to the provider. Topical anesthetic, such as lidocaine-epinephrine-tetracaine gel, can be used over the affected area to minimize discomfort. As mentioned previously, evaluation of the patient’s platelet count and coagulation studies may be indicated. Additionally, for larger hematomas, consider a type and screen and ensure that appropriate blood products are readily available, should a bleeding emergency result. Gauze impregnated with hemostatic agents or tranexamic acid can also be at bedside to assist with bleeding control.


Procedure


Evaluate the patient’s normal anatomy by initially scanning away from the affected area. Scan the entire length and width of involved area in two planes—both sagittal and transverse—using the linear array probe. Applying graded compression helps ensure a loculated fluid collection, which can be easily overlooked in the case of hematoma, is not missed. Application of color Doppler flow confirms lack of vascularity. If a fluid collection concerning for hematoma is located, note the boundaries, depth from the tissue surface, and estimated size of the cavity. The sonographic appearance of a hematoma is non-specific and is challenging to differentiate from an abscess [3].


The affected area should then be cleansed with chlorhexidine and subsequently anesthetized. The probe should be covered with a Tegaderm, and gel should be placed over top of the probe. Under ultrasound guidance, a minimal stab incision should be made using a #11 blade scalpel, and blunt dissection should be used to break up loculations, especially if there are clots or it is an infected hematoma (Fig. 11.13). Gauze pads can be used to apply pressure and evacuate any remaining clot. After incision and drainage is complete, verify complete evacuation of the hematoma cavity using ultrasonography.

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Fig. 11.13

Another possible diagnosis is an infected hematoma. A hematoma that later becomes infected. Note the heterogeneous contents of this infected hematoma. There is also thickened skin overlying this fluid collection. The patient had presented with signs and symptoms of an abscess with a history of trauma in this area. This fits with an infected hematoma


Complications


Bleeding is a potential complication associated with this procedure. Caution is advised in patients with a known bleeding diathesis or on anticoagulation. There may be persistent oozing from the incision site. It is advised to apply a compression dressing after the incision and drainage.


Pearls/Pitfalls





  1. 1.

    Use of color Doppler pre-procedure and real-time sonographic evaluation during the procedure can help avoid potential neurovascular complications.

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Oct 20, 2020 | Posted by in ANESTHESIA | Comments Off on Percutaneous Drainage Procedures

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