Perianal abscess and fistula: Clinical sciences

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Introduction0:00–0:27

Perianal abscesses and fistulas are anorectal diseases that result from obstructed glandular crypts of the rectum or anus.
A perianal abscess is a collection of pus that can form in a number of spaces within the anus or rectum. On the other hand, perianal fistulas can form after an abscess is drained and typically result from chronic changes of the same infectious process.
Now, the first step is to obtain a focused history and physical examination. You should also obtain basic labs, such as a CBC to look for any clues of spreading infection.Now, a patient might report intermittent pain that’s typically associated with sitting, activity, and possibly with defecation.

Perianal fistula - History and physical0:27–1:35

The patient may also report intermittent malodorous drainage with or without pruritus. On a physical exam, you’ll typically find a non-healing abscess or chronic purulent drainage.
As you’re performing the exam, see if you can visualize the external opening of the fistula, which might be found with excoriation, inflammation, or induration, as well as drainage of purulent fluid.
On a digital rectal exam, you may be able to palpate the internal opening or an abscess, if present. Lastly, labs may reveal leukocytosis.
If the patient presents with this clinical picture, you can suspect a perianal fistula.Now that we have a potential diagnosis in mind, let’s talk about imaging.

Diagnostics1:35–2:40

The next step is to proceed with anoscopy or sigmoidoscopy, which can help confirm the diagnosis of a perianal fistula. If you don’t see any findings suggestive of a fistula on anoscopy or colonoscopy, consider an alternative diagnosis.
However, if you find an internal opening of the fistula in the anus or rectum, this supports your suspected diagnosis of a perianal fistula.
The next step is to proceed with diagnostic imaging, such as pelvic MRI or endosonography, which helps you get a better picture of the fistula and determine if it’s a simple or a complex fistula.
Some high-yield facts to keep in mind! Crohn disease has a strong association with perianal and anorectal manifestations.
So, in patients with Crohn disease, be sure to look out for a perianal abscess, perianal fistula, anal fissure, or anal stricture at some point.Now, one way to tell whether the patient has a simple or a complex fistula is by determining the level of external sphincter involvement.

Simple fistula2:40–4:20

Most simple fistulas don’t involve the external sphincter, and if involved, it will be 30% or less of its thickness. If this is the case, you can diagnose a simple fistula.
There are three main types of simple fistulas to know: superficial, low transsphincteric, and intersphincteric fistulas.
Superficial fistulas don’t involve the external sphincter at all. Low transsphincteric fistulas involve the lower third of the sphincter.
Lastly, intersphincteric fistulas extend between the internal and external sphincters. Alright, let’s talk about the management of simple fistulas.
First, start with empiric antibiotics, such as ciprofloxacin or metronidazole. Next, consult the surgical team for incision and drainage and a sphincter-sparing procedure, such as fistulotomy or fistulectomy.
A fistulotomy involves cutting open the entire fistula to clean the area and allow it to heal. On the flip side, fistulectomy involves complete excision of the entire tract and closing the ends.
After the chosen procedure is complete, counsel the patient on keeping the area clean, as well as performing Sitz baths frequently in order to help alleviate any residual pain and to prevent infection or future recurrence.Now that we’re done with simple fistulas, let's go back to imaging and talk about complex fistulas.

Complex fistula4:20–6:22

Unlike simple fistulas, complex ones are, well… more complex. If you see external sphincter involvement greater than 30%; a fistula that’s proximal to the dentate line; a multiple tract fistula; a recurrent fistula; or if the patient has a history of anal incontinence, you can diagnose a complex fistula.
Now, there are four main types of complex fistulas to know. These are high transsphincteric, suprasphincteric, extrasphincteric, and horseshoe fistulas.
High transsphincteric fistulas involve greater than 30% of the external sphincter and extend from the external sphincter to the ischiorectal fossa.
Suprasphincteric fistulas extend from the anal crypt to the ischiorectal fossa. Next, extrasphincteric fistulas are in the high anal canal and are located proximal to the dentate line.
Lastly, horseshoe fistulas are located posterior to the anal space and extend to the ischiorectal space. Okay, time to talk about management.
As before, you want to start the patient on empiric antibiotics. Next, proceed with surgical consultation for seton placement.
A seton is basically a surgical thread that is placed to help with drainage and prevent the fistula from closing while it heals.
It also helps preserve the sphincter mechanism and prevents fecal incontinence. After 6 weeks, the patient can then have a definitive sphincter-sparing procedure, such as an advancement flap, the Modified Hanley procedure, ligation of the intersphincteric fistula tract, fibrin sealant use, or a fistula plug.
After the procedure is complete, advise the patient on keeping the area clean and performing Sitz baths frequently.Alright, now that we’ve discussed the perianal fistula, let’s go all the way back to history and physical exam, and talk about a different presentation.

Perianal abscess - History and physical6:22–9:40

Okay, your patient may report a history of severe, constant pain in the anal or rectal area, which may or may not be associated with defecation, and there may also be spontaneous drainage coming from the area.
Additionally, the patient might report fever and chills. On physical exam, you might notice a focal area of fluctuance with possible erythema and induration overlying the perianal skin.
On digital rectal exam, you might palpate a fluctuant, indurated mass that might be tender. Lastly, labs may come back showing leukocytosis.
If you see these findings, the diagnosis is a perianal abscess. Okay, since this is a clinical diagnosis, we can move on directly to management.
The management of perianal abscesses starts with surgical consultation for incision and drainage. Most patients are often only treated with incision and drainage.
Remember that the pus within the abscess is under pressure, so when doing an incision and drainage, be sure to stand to the side of the patient to prevent getting blasted in the face!
Next, for local wound care, you want to prevent the skin surrounding the wound from healing and close the infection back in, you need packing, usually using wet to dry dressings or a wick so the lesion can heal from the inside out.
However, IV empiric antibiotics, such as ciprofloxacin or metronidazole, can be started in some patients, such as those who are immunocompromised or otherwise complicated.
You can also obtain cultures from samples like blood, tissue, pus, or any fluid that is draining from the abscess, so that you can tailor antibiotics down the line.
Once the treatment is started, you should assess the patient's response to it after about 48 to 72 hours. If you notice clinical improvement or resolution of symptoms, the patient has an adequate response to treatment.
In this case, you can continue local wound care, and for patients who were started on antibiotics can switch from IV antibiotics to oral ones and complete the antibiotic course.On the other hand, if after 48 to 72 hours the patient doesn’t improve, it’s considered an inadequate response to treatment.
In this case, you should consider the presence of a refractory abscess, an infection, or a fistula. At this point, order an anoscopy or sigmoidoscopy to confirm your suspected diagnosis.
If you see a remaining fluid collection or a loculated abscess, then the diagnosis of a refractory abscess or infection is confirmed.
In this case, repeat incision and drainage, obtain cultures, and give tailored antibiotics per culture results. On the other hand, if you notice an internal opening in the anus or rectum, then a diagnosis of a fistula can be made.
In that case, start or continue antibiotics and consult the surgical team for fistula treatment.Alright, as a quick recap… Perianal abscesses and fistulas result from obstructed glandular crypts of the rectum or anus.

Review9:40–10:56

Patients should be evaluated with anoscopy or sigmoidoscopy to make a diagnosis. Further imaging with a pelvic MRI or endosonography can help identify the level of external sphincter involvement and make a distinction between simple and complex fistula.
For treatment, simple fistulas require antibiotics, incision and drainage, and a sphincter-sparing procedure like a fistulotomy or fistulectomy; while complex fistulas are treated with antibiotics, seton procedure, and then a sphincter-sparing procedure.
On the other hand, the diagnosis of perianal abscesses is mainly clinical. Treatment involves incision and drainage, local wound care, and sometimes antibiotics.
After 48 to 72 hours, patients who don’t improve should be evaluated with anoscopy or sigmoidoscopy to look for refractory abscesses or fistulas.
For treatment, refractory abscesses are treated with repeat incision and drainage and antibiotics; while fistulas require antibiotics and surgical consultation.
or fistulas for treatment Refractory abscesses are treated with repeat incision and drainage and antibiotics While fistulas