Visiting Veterinarian : In dogs, too much saliva can lead to trouble
The first thing Kermit's owner noticed was that the young beagle was having difficulty chewing. "His appetite is fine," she reported. "But he seems to have trouble eating. Then I saw that!"
"That" was a thin-walled, pink swelling protruding from under Kermit's tongue and poking out one side of his mouth.
"Is it cancer?" she asked with a worried expression.
"Nope," I reassured her. "Probably not cancer. It's called a ranula and it's simply a pocket filled with saliva."
"What causes that?" she inquired.
Our explanation must start with an anatomy lesson. Dogs have four pairs of salivary glands. The parotid glands, near the ears, and the zygomatic glands, by the cheekbones, both have ducts that open inside Kermit's mouth near the fourth upper premolars. The mandibular salivary glands lie near the jugular veins where Kermit's lower jaw (mandible) and neck meet. The sublingual glands are, well, sublingual, i.e., beneath the tongue. Ducts from the mandibular and sublingual glands both open under Kermit's tongue. When everything is working properly, saliva from each gland travels down these ducts, emptying into the mouth so Kermit can eat, pant, lick, and drool all over you, as needed.
But occasionally something goes awry. Instead of flowing freely into the mouth, saliva leaks into surrounding tissue, creating a salivary mucocoele. That's a fancy name meaning mucous-filled cavity. There are two common locations where this occurs in dogs. With cervical mucocoeles, drool accumulates along the underside of the throat by the lower jawbone, creating a pouch that looks like a double chin or big, pendulous jowl.
Another common location is sublingual, like Kermit's. People also get sublingual mucocoeles. When these patients open their mouths to say "Aaah" for their physicians, they look a little like — well, frogs. You know the way a bullfrog puffs out its throat to croak? Some long-ago doctor with a dearth of sensitivity to the feelings of those thus afflicted dubbed the condition "ranula," meaning "little frog" in Latin. So much for bedside manner.
Diagnosis of salivary mucocoele is fairly straightforward. If it looks like a frog, and croaks like a frog, it's probably a frog. Seriously, most mucocoeles are readily diagnosed on appearance, history, and, if needed, aspiration to confirm that the fluid inside is saliva. Secondary infection and hemorrhage sometimes turn the fluid an opaque reddish-brown, but the classic viscosity of drool still clues us in. But salivary mucocoele is really just an impressive-sounding way to describe the condition. It tells us what it is, but not why it is.
What actually causes Kermit's malady? On occasion we can pin the cause down to something that obstructs or damages a salivary gland or duct. The culprit might be trauma, tumor, inflammation, infection, or even a tiny foreign body blocking outflow. But in the majority of cases, there is no visible explanation and we cannot determine the origin of the problem. Since we medical people don't like to appear stumped, we maintain our dignity by dubbing these cases "idiopathic."
So how do we treat salivary mucocoeles? In the few cases where we find an obvious underlying etiology, such as a tumor, we address the cause. Otherwise, our options are limited. The current literature says that primary bacterial infection is not commonly implicated, but when I was in school we were taught to begin by treating mucocoeles medically — draining them if needed, and prescribing antibiotics and anti-inflammatories.
I have had frequent success with this protocol. Maybe it was the pills. Or maybe a ten-day course of medication simply gave the owners something to keep them busy while Mother Nature fixed things on her own, since a certain percentage of ranulas resolve spontaneously. "Let's give Kermit antibiotics and see how he does," I suggested. Ten days later, Kermit was all better. "That's that," I thought, mentally filing the case away. "Fixed another one."
Only Kermit wasn't fixed.
"It was looking good, Doc," Kermit's mom told me on the phone, "but it's come back. Can we do more antibiotics?" I agreed readily. Over the next few months, Kermit's ranula resolved and recurred several times. At first I conjectured that he was simply repeatedly traumatizing the swollen tissue. The way the ranula bulged to one side, it was easily caught between his teeth when he chewed. But I finally had to accept the fact that conservative medical care was not working. I needed to get a good, long look under that tongue, something he resisted vehemently. Kermit needed to be anesthetized so we could do a thorough exam and follow up with appropriate surgical intervention. "If we find an obvious cause, like a tumor or foreign body, we can address that," I explained, but I knew that odds were I would find neither of these things. "Sometimes we need to actually remove the affected salivary glands to cure this problem," I continued. But excising salivary glands is neither minor nor without potential complications. Before going to such lengths, I suggested we proceed with a technique called marsupialization.
We now jump from frogs to kangaroos. Marsupials are "pouched" mammals like koala bears, kangaroos, and opossums. The poetic term "marsupialization" refers to a surgical procedure in which the surgeon creates an opening between the interior of a cyst and the exterior tissue, suturing it open so that the cyst can drain indefinitely. Kermit's surgery went swimmingly. Rather than making a simple slit on the mucocoele, I removed a substantial rectangular window of excess tissue, extracting the gooey slime that filled the ranula, then suturing the edges of the window open in a way to provide ongoing drainage.
"There's a chance that area could eventually fill back in," I cautioned the family. "If that happens, we may have to proceed with surgically removing the salivary glands on that side."
To date, however, Kermit is doing well. In our veterinary menagerie, the kangaroo technique on the froggy ranula seems to be working, and our little doggy is once again happy as a clam in mud at high tide.