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What Are Anal Sinuses?

By Erin J. Hill
Updated Mar 03, 2024
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The anal sinuses are openings that are comprised of folds of tissue which separate the rectal columns. They have not traditionally been well understood, but it has been determined that the sinuses are separated from the rectum and anus as entities in their own rights. It is not believed that they are particularly significant in terms of colorectal diseases, although they can occasionally become infected if pathogens enter the rectal cavity.

Both the anus and rectum are connected as a long canal leading from the rectal opening to the large intestine or colon. Their primary functions include pushing solid waste materials out of the body during defecation, and absorbing water from fecal matter so that it is not lost by the body as the wastes are removed. The rectum and anus have a column-like shape which is separated by the anal sinuses.

The rectum and anus are comprised of several mucus membranes which overlap each other. Spaces between these membranes are referred to as the anal sinuses. They are partially comprised of mucus membranes as well as by muscular tissues. The anal sinuses are located toward the top portion of the anal cavity.

Presence of the anal sinuses is usually of no consequence to most individuals. They are not considered more vulnerable than other areas of the colorectal cavity to cancers and other serious complications. These sinuses may become affected by colorectal cancer just like any other area of the anal cavity, but they are not generally affected in isolation since they are directly connected to the remaining area of the anus.

The anal sinuses may become infected sometimes, however, if they are blocked or clogged in some way. This may occur if pathogenic bacteria enter the rectum or if fecal matter is allowed to remain in the area for too long, thus allowing bacteria to multiply. When this occurs a large sore or abscess will typically form. Pain is a common symptom of having an anal abscess, especially when attempting to relieve the bowels or sitting down.

When an abscess located in the anal sinuses ruptures, blood or pus may exit the rectum both during bowel movements and sometimes between them. Medical treatment is recommended. Anal infections are not overly common, although they are more prevalent in those with other medical conditions or who have had anal surgery. Wiping thoroughly after bowel movements may help prevent infection, as well as defecating often enough.

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Discussion Comments

By anon941579 — On Mar 23, 2014

I've been getting small abscesses near my sphincter every month or so and the skin on my right cheek gets really inflamed, red and prickly. Ever time it flared up the doctor gave me a week of antibiotics and it all cleared up. But, it kept happening every couple of months and has been going on for over three years.

I finally had an MRI that they thought showed a small fistula and then last week I had an exploratory operation under general anesthetic. While looking around the surgeon found an anal sinus, not a fistula, about half an inch long that he believes is the source of the abscesses and infections. He removed it while I was under.

A week later and I'm still in a lot of pain down there and passing stools is horrid. Lots of soaks in hot salty bath water are keeping any post op infections at bay and fingers crossed I'll have no more abscesses.

By ddljohn — On Dec 10, 2011

@fify-- A great way to treat fistulas, abscesses and inflammation in this area is to do hot water soaks. Just fill a tub with hot water and sit in it for a while everyday.

If there is an infection, doctors will give antibiotics. If there is pus, doctors can drain that which helps relieve the pain.

But aside from these, I think the best treatment is prevention through a healthy diet, lots of fiber containing foods and regular bowel activity like the article said.

By fify — On Dec 09, 2011

@ysmina-- I'm not a doctor or an expert on this issue, but I'll try and answer as best as I can.

I know that abscesses and hemorrhoids are not the same thing. Abscess is inflammation and formation of pus under the tissue. Hemorrhoids is when veins in the anus become larger and the tissue swells because of it.

I think when it comes to inflammation, sensitivity, abscess and hemorrhoids, they are categorized that way no matter where they occur in the rectum and anus membranes. So I think that abscesses and hemorrhoids can occur anywhere, including the anal sinuses.

By panda2006 — On Dec 09, 2011

@afterall- Sometimes people with chronic sinuses have no issues with anal sinuses, but it just depends. I had sinusitis treatment many times but still had issues with anal sinuses for awhile. Not all treatment of sinuses work for everyone, so it can take awhile to figure out just what problems you have and how to fix them.

By ysmina — On Dec 08, 2011

@StarJo-- That's exactly what I was wondering right now- the difference between abscesses in the anal sinuses and hemorrhoids.

They really sound the same to me. I've experienced hemorrhoids several times, generally after eating unhealthy and dry foods and long trips. It's always scary to see blood while in the bathroom and I try to keep some hemorrhoid cream on hand in case it happens.

Abscesses seem like the same thing to me. What is the difference? Doesn't hemorrhoids take place on the anal sinuses as well?

And what's the best anal sinuses inflammation treatment?

By afterall — On Dec 07, 2011

I didn't even realize that anal sinuses existed. Now that I think of it though, I have a couple of friends with chronic sinus problems and they have issues relating to it all over their bodies. I guess it's a problem that is even more complicated than I had thought.

By StarJo — On Dec 07, 2011

@kylee07drg – You really should see a doctor. I had an anal sinus infection last year, and I had both pain and bloody stools.

I had a lot of constipation. Even though the anus is made to expand and allow feces to move through, my stools were just too thick and hard to be pushed out.

Because of this, they just sat there for about a week, until I took a super strong laxative. This was long enough for my anal sinuses to get a bacterial infection.

It hurt to sit down. It felt a lot like hemorrhoids, but the fact that it didn't go away made me worried.

I had to have antibiotics. Without the medication, things would have only gotten worse.

By kylee07drg — On Dec 06, 2011

Has anyone here actually had an anal sinus infection? I have been having some of the symptoms mentioned in the article, but I'm not sure that's what it is.

I have noticed blood in my feces and pain when I have a bowel movement. However, I just assumed it was my hemorrhoids acting up again.

My hemorrhoids usually cause me grief for awhile, and then the symptoms fade. The blood and pain have lingered extra long this time, and though I hate to have a colonoscopy, I am afraid that is what my doctor will deem necessary if I see her.

By OeKc05 — On Dec 06, 2011

@wavy58 – Yes, anal sinuses are something most of us don't even know we have. I only heard of them after my friend's newborn baby had issues with hers.

Babies don't have much immunity to infection. Plus, they are always having to sit around in feces until the parents notice they need to be changed.

My friend's baby started having blood mixed with her feces. After seeing this in her diaper, my friend got in to see her doctor right away. He gave her antibiotics, and the infection cleared up.

The baby must have been in pain, because she had been crying for nearly two days straight before the blood showed up. After starting the antibiotics, she slept peacefully and seemed content.

By wavy58 — On Dec 05, 2011

I am currently studying human anatomy in college, and I just saw a diagram of the anus and rectum the other day in class. The anal sinuses were in between the two, and the book said they are also called “anal crypts.”

They look like scalloped edges on a cookie cutter. I expected sinuses to be more rounded and like pockets of air, but they are only the spaces between the “scallops.”

We didn't spend much time discussing them in class. They don't seem to have much of an effect on the overall function of the system, so we barely touched on them at all.

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