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The Plunging Ranula: Pathophysiology & Workup
Julia Casazza • Aug 16, 2023 • 40 hits
While uncommon, plunging ranluae - salivary pseudocysts that protrude through the myelohyeoid muscle - are among the most gratifying benign neck masses to treat. Patients generally complain of pain and neck swelling. Through physical examination, ultrasound, and CT scans, otolaryngologists can rule out life-threatening causes of neck swelling and plan for surgery. Interviewed by hosts Dr. Ashley Agan and Dr. Gopi Shah, Dr. Rohan Walvekar, professor of otolaryngology and vice chair for head & neck oncology services at LSU Health New Orleans guides readers through pathophysiology, workup, and differential diagnosis of the plunging ranula.
This article features excerpts from the BackTable ENT Podcast. We’ve provided the highlight reel in this article, and you can listen to the full podcast below.
The BackTable ENT Brief
• A ranula is a saliva-filled pseudocyst that forms when normal flow out of a salivary gland is compromised. While any salivary gland could be implicated, over 90% of ranulae come from the sublingual gland.
• A plunging ranula is a ranula that has entered the neck.
• The differential diagnosis for a plunging ranula includes benign and malignant pathologies. Otolaryngologists should consider dermoid cysts, duplication cysts, lymphovascular malformations, lymphangiomas, and thyroid malignancy.
• Ranulae can form following damage to salivary glands during oral surgery, particularly sialendoscopy.
• Both ultrasound and CT scan have a role in workup of the plunging ranula.
Table of Contents
(1) Pathophysiology of the Plunging Ranula
(2) Plunging Ranula Formation
(3) How to Workup a Suspected Plunging Ranula
Pathophysiology of the Plunging Ranula
A ranula is a saliva-filled pseudocyst that forms when normal flow out of a salivary gland is compromised. Due to their pouch-like appearance, they share a name with the frog’s underbelly. More than 90% of ranulas come from the sublingual gland, the smallest of all three major salivary glands. Sandwiched between the muscles of the tongue and the mandible, an obstructed sublingual gland can leak saliva into surrounding tissues. When immune cells surround this saliva, a pseudocyst forms. If the ranula protrudes through weaknesses in the myelohyoid muscle, it can “plunge” into the neck. Patients with plunging ranulas will report neck swelling and mild-moderate neck pain that can be referred to the ear. Differential diagnosis for a suspected ranula depends on patient age. For children, consider dermoid cysts, duplication cysts, and lymphovascular malformations. For teenagers and adults, lymphovascular malformations, lymphangiomas, and thyroid malignancy should be ruled out.
[Ashley Agan MD]
Yes. It just occurred to me that we jumped into the patient presentation before we talked about what is a ranula. You talked about your spiel to patients about: What is a ranula?, How does it plunge? Can you just tell us what your spiel sounds like?
[Rohan Walvekar MD]
Yes, absolutely. It's really difficult to describe to patients and so this is how I usually tell my patients about ranulas. I tell them that the sublingual gland is this small gland that contributes to less than 1% of saliva, but then, when it gets obstructed, or it gets injured for whatever reason, it can really be troublesome. I talk to them about it being tucked between the mandible on one side and the mandible is trying to elbow it in.
Then the other side is the muscles of the tongue that are really sandwiching this gland in the middle. When the glands gets obstructed, or it gets injured, it starts leaking saliva because it has nowhere to go. Saliva leaks out of this gland, because it's overcapacity, and now it's flowing into the floor of the mouth. I tell patients that saliva in its normal space in the mouth, in the digestive system, is very helpful, but outside of that, and we know that from our laryngectomy, fistulas, and things like that, it's very irritant.
I graphically tell them that if I take a syringe, fill it with saliva, and inject it into my muscles, what it's going to do is going to create an intense reaction. When saliva leaks out from the sublingual gland, the body tries to create a reaction around it, almost trying to shepherd it into trying to stop the saliva from going to different places, and that what that looks like is a pseudocyst. Basically, a wall of inflammatory cells that really don't have any integrity, but it's just a way for them to curb that infection.
If that's limited to the floor of the mouth, then you see a cyst in the floor of the mouth, but at some point in time, this is just a free-flowing water, it's like a leaking faucet and sometimes the fluid will find weaknesses in the floor to be able to escape into the neck. These tend to be the neurovascular ports in the mylohyoid muscle. You actually see these weaknesses, or these areas of dehiscence while you do level one neck dissection.
If you really pay careful attention to your level one neck dissection, as you take this fibrofatty packet of tissue out of level one, you'll see a lot of vasculature over the mylohyoid muscles. Guess what, that's exactly where the saliva is going to flow out of and come into the neck. I talk to them about that and say that once it's in the neck, it forms this plunging ranula, but the source is that leaking faucet in the floor of the mouth, which is the sublingual gland. I don't know if that's helpful.
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Plunging Ranula Formation
For a ranula to form, the normal drainage of the sublingual gland must be compromised. Inflammation surrounding the duct, whether due to autoimmune or infectious causes, provides a set-up for obstruction and subsequent ranula formation. Alternatively, manipulation of minor salivary gland during sialendoscopy can damage the sublingual gland outflow tract, predisposing the patient to future ranula development. While studies linking sialendoscopy to subsequent ranulas are limited, Dr. Walvekar estimates the incidence of this to be less than one percent of all sialendoscopies.
[Gopi Shah MD]
As far as age, these patients tend to be younger than our typical older neck mass patients in general.
[Rohan Walvekar MD]
Most of them tend to be younger in their teens or young adults and that's the majority that you'll see in this age group. Having said that, we create problems and while we are trying to fix problems with sialendoscopy, and more and more people are undergoing endoscopic salivary gland procedures and consequently transoral incisions, you are going to see a lot more ranulas. Because when you start manipulating the submandibular duct and the minor salivary glands in that area, you could potentially injure the outflow tract to the sublingual gland. I've recently seen a patient who has a floor-of-mouth ranula as a consequence of a pretty extensive transoral approach for management of stones.
This is going to happen even in the older group and you need to keep that as a part of your differential.
[Gopi Shah MD]
That's an interesting point. Is there a percentage, are there studies that show follow-up, or is this now we've been doing sialendoscopy for close to 8 to 10 years, and now I'm seeing these patients come in?
[Rohan Walvekar MD]
I think that's a really good question what is the incidence of ranulas after endoscopic or transoral procedures related to management of stones or stenosis in the floor of the mouth? I don't think there's a good number for that. It is something that is real and can happen, and so it should be a part of your discussion when you talk about your informed consent and possible complications, but in reality, I would say it's less than 0.5%.
Now, it's also important to note that when you think about making an incision in the floor of the mouth to get to the submandibular duct, the way the sublingual gland and the minor salivary glands interact with the submandibular duct is a very important thing. In many cases, after you make the submucosal incision, you can actually input the sublingual gland bluntly away from the duct. If you do that, then your likelihood of injuring the sublingual duct or the sublingual gland becomes less. Careful attention to technique at that time is really important.
The important thing is not to think about getting the stone out when you think about management of the floor of the mouth and you think about how do you approach it as a way to prevent future complications after you make the incision in the mouth. You have to make an attempt to move the sublingual gland away. You have to get through one layer of minor salivary glands, but then you can easily bluntly dissect the sublingual gland away so that you don't injure the sublingual duct and the gland itself. That can prevent the ranulas in the future. Now, there are no guarantees that this would happen, but at least you're reducing your chances of doing that.
How to Workup a Suspected Plunging Ranula
Dr. Walvekar recommends investigating a suspected plunging ranula through physical exam and imaging. A simple ranula appears as a blue-tinged, translucent mass underneath the tongue. If a plunging ranula is suspected, examine the floor of mouth. Bimanual palpation is an excellent tool to determine whether the suspected mass comes from the sublingual gland. If the diagnosis remains unclear after examination, a head and neck ultrasound can be used to visualize the mass. When planning for surgery, physicians genrally order a CT scan with and without contrast. On CT, ranulae appear as irregularly-shaped collections of hypodense fluid.
[Gopi Shah MD]
Moving on to our patient that's presenting with the ranula, what does your physical exam look like? What are you seeing and what are you looking for?
[Rohan Walvekar MD]
Honestly, the physical examination is very minimalistic. The main components I'm looking for is I examine the floor of the mouth for the patency of the submandibular duct. One is, can I visualize the papilla? Is it working? Because those are important things. If I do want to cannulate the duct for the procedure to maybe stent it so that I know where the duct is, I know that it's not going to be an issue or whether it's working or not. I can counsel the patients accordingly.
The second thing is obviously do a good bimanual palpation. You can get good elimination and examine the floor of the mouth. The best feeling is when you see that the ranula or a blue translucent thing in the floor of the mouth you know that your diagnosis is pretty much spot on. Sometimes you'll just look at the floor of the mouth and it'll appear normal and then what you want to do is do a comparative examination. Examine the normal side and see what the sublingual gland feels like, then examine the abnormal side and see if you feel it's slightly more bulky. That can give you a little bit of a clue as to whether this is truly a sublingual gland in origin. Then, of course, you bi-manually examine it.
If you have the ability to do an ultrasound in the office, that can be tremendously helpful. No harm in putting an ultrasound in the neck and just getting a sense of is this fluid collection around the submandibular gland, is the submandibular gland involved, or no. It's very difficult to sometimes see the sublingual gland in these settings because there's a lot of fluid around it but at least if you can examine the architecture of the submandibular gland, you'll know that it's not like a submandibular gland cyst. It's a combination of things.
I have an ultrasound in my office that I use pretty routinely for situations like this. I would definitely encourage you guys to-- at least whoever is listening or listeners to this podcast, to invest some time in learning how to do ultrasound of the head and neck.
[Gopi Shah MD]
Do you do an ultrasound even for anybody that has a intraoral component in the neck component or is it part of your neck mass workup anyways? If you have an intraoral component and you can see the blue and that clinical picture fits which you're thinking is that enough or do you feel ultrasound is something that you always do as an intermediary step?
[Rohan Walvekar MD]
No, I don't believe in doing things “just because you have to do them.” I focus my examination and interventions just to give me enough information to make a decision. If I am pretty confident that this is a plunging ranula, the ultrasound is not going to help me make that decision. I try to keep it as practical as possible.
Dr. Rohan Walveker
Dr. Rohan Walvekar is clinical professor of head and neck surgery with LSU in Metairie, Louisiana.
Dr. Ashley Agan
Dr. Ashley Agan is a practicing ENT and assistant professor at UT Southwestern Medical Center in Dallas, TX.
Dr. Gopi Shah
Dr. Gopi Shah is a practicing ENT at UT Southwestern Medical Center in Dallas, TX.
Cite This Podcast
BackTable, LLC (Producer). (2023, June 8). Ep. 115 – Management of the Plunging Ranula [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.