US-guided procedures are extremely helpful in many areas. It helps to identify anatomy and it can help to guide in several situations, e.g.
Locating a fragment of the foreign body for surgical removal, e.g., fish bone in the oral mucosa, fragment tooth that embedded in the lips, wood splinter in soft tissue.
Botox/steroid injection into the salivary gland or any soft tissue safely.
Identify small recurrence or metastatic lymph nodes for removal.
Fine needle aspiration cytology (FNAC).
Basket retrieval of a stone from a salivary duct.
Balloon ductoplasty of a salivary duct.
Guidance aid during a sialoendoscopy of a salivary duct.
20.1 US-Guided Fine Needle Aspiration Cytology (FNAC)
US is extremely helpful to guide a needle into a lump in the head and neck area for cell aspiration or drainage of a fluid collection. Understanding the anatomy is vital as to the structures in the surrounding area to avoid complications. It is important to have a sterile technique to avoid infection.
The FNA tray preparation is as shown below Fig. 20.1 on sterile sheet.
The equipment that is needed depends on the lump and the site of the lump. The needles that are used are normally nonsafety needles. This allow for easy handling when performing the FNAC procedure, slide preparation and also for needle washing in a stadardised specimen pot. The needle sizes range from 19G to 27G. Some of the needle sizes are shown in Fig. 20.2. For majority of the lumps, a 27G and 25G needles are recommended for FNAC. If the lesion is very deep, the spinal needle is useful as it is one of the longest needle available.
Prior to FNAC or core biopsy, it is very important to know the patient’s medical history and if there are any contraindication factors to the patient having a FNAC, e.g., bleeding disorder, anticoagulation medication, e.g., warfarin, heparin, rivaroxaban, etc., steroid medication and any drug allergies.
Patient’s consent: In the UK, it is vital to have a patient’s consent for any intervention procedure. Depending on your local hospital policy, this may be verbal or written consent. Patient should be informed of the expected risks and complications that may arise from the procedure. This includes pain, swelling, bruising, bleeding, possible damage to the nerve giving rise to nerve palsy, infection, abscess/tumor tracking through the needle track, scar formation and non diagnostic sampling. In any patient who has a history of keloid scar formation or whom form scar easily, a skin incision should be avoided where possible eg during the insertion of a core biopsy needle.
Prior to inserting the needle, it is very important to wipe the skin of any US gel contamination. As this can cause artifacts on the slide. It is also important to disinfect the skin with an antiseptic solution. During the FNAC, instead of the US gel, chlorhexidine solution can be used as a lubricant (Figs. 20.3 and 20.4). Skin that has not been cleaned or usage of non sterile needle may cause abscess formation.
There are two techniques for US-guided FNAC: (1) Using parallel technique or (2) perpendicular technique (Figs. 20.5, 20.6, and 20.7).