Diagnosis Coding For Pilonidal Cysts Need Not Be Painful

diagnosis coding for pilonidal cysts

Coding For Pilonidal Cysts

In order to accurately code for pilonidal cysts in ICD-10-CM, the coder must know certain facts about the condition and what to look for in the documentation.

A pilonidal cyst is an abnormal pocket in the skin that is usually found near the tailbone at the top of the cleft of the buttocks. According to the Mayo Clinic, the pocket usually contains hair and skin debris. If the cyst becomes infected, it can turn into a painful abscess. 

Coding for pilonidal cysts is based on whether the documentation specifies the cyst is with or without an abscess. 

In the following two coding scenarios, I will explain how to locate and verify the correct codes and review the coding guidelines.

Coding Exercise: Pilonidal Cyst With Abscess

A 25-year-old male presents with a painful growth above the cleft of the buttocks and is diagnosed with a pilonidal abscess. 

Locate and Verify

Look in the ICD-10-CM coding manual Index under Abscess, pilonidal, pilonidal cyst with abscess, L05.01.

In the Tabular, this code can be verified as:

L05.01, Pilonidal cyst with abscess 

Inclusion terms:

  • Pilonidal abscess
  • Pilonidal dimple with abscess
  • Postanal dimple with abscess

There are different ways to find the appropriate code here. 

For example, if the documentation states “pilonidal cyst with abscess,” the coder can look under Cyst, pilonidal, with abscess. 

“Pilonidal dimple with abscess” or “Postanal dimple with abscess” can be found by looking up Dimple, pilonidal or postanal – see Cyst, pilonidal. 

No matter which of the above terms is used in the documentation, your search will take you to the same code (L05.01). 

Note: The documentation may use terms such as “associated with” or “due to” to show a link between the pilonidal cyst and abscess. Even if the documentation does not link the two, we can presume there is a causal relationship unless the documentation states otherwise. This is because of the word “with” in the code description (“Pilonidal cyst with abscess”).  

Pilonidal cyst definition. facts to look for in documentation in order to code for it in icd-10-cm

Coding Exercise: Pilonidal Cyst Without Abscess

A 22-year-old male presents with a painful, swollen lesion in the sacrococcygeal region. A review of systems is negative for fever, chills, or drainage at the site of the lesion, and there is no abscess. The patient is diagnosed with a pilonidal cyst.  

Locate and Verify

I would start by looking in the Index under Cyst, pilonidal (infected) (rectum), L05.91. This is the default code.

Or we can go further down the list and see that Pilonidal cyst without abscess points us to L05.91. When we verify the code in the Tabular, it indicates:

L05.91, Pilonidal cyst without abscess

Inclusion terms:

  • Pilonidal dimple
  • Postanal dimple
  • Pilonidal cyst NOS

Again, depending on which of the above synonyms are specified in the documentation, we can locate the same code (L05.91) by using different terms in our search. 

For example, “Pilonidal dimple” can be found by looking up Dimple, pilonidal or postanal – see Cyst, pilonidal, without abscess.

Review the Instructional Notes

Before we can be sure we are done coding for the above two coding examples, we must first review all the notes provided at each of the codes to ensure our ICD-10-CM codes are accurate and complete.

We have verified the codes in the Tabular, so what else needs to be done?

Let’s look a little further at all the notes provided at L05.01 and L05.91.

There are coding guidelines for both of these codes, which are identical.

Excludes2 at L05.01 and L05.91

There is an Excludes2 note at each of the above codes that indicate if the patient has either of the following conditions, they too should be reported:

  • congenital sacral dimple (Q82.6)
  • parasacral dimple (Q82.6)

Use Additional Code at L00-L08

A Use additional code indicates we need to assign a code from B95-B97 to identify the infection agent if applicable. 

Excludes2 at L00-L08

An Excludes2 note at L00-L08 indicates if any of the following conditions are documented in addition to the pilonidal cyst with abscess (L05.01) or in addition to the pilonidal cyst without abscess (L05.91), a code should also be assigned to report for each of these conditions:

  • hordeolum (H00.0)
  • infective dermatitis (L30.3)
  • local infections of skin classified in Chapter 1
  • lupus panniculitis (L93.2)
  • panniculitis NOS (M79.3)
  • panniculitis of neck and back (M54.0-)
  • Perlèche NOS (K13.0)
  • Perlèche due to candidiasis (B37.0)
  • Perlèche due to riboflavin deficiency (E53.0)
  • pyogenic granuloma (L98.0)
  • relapsing panniculitis [Weber-Christian] (M35.6)
  • viral warts (B07.-)
  • zoster (B02.-)

Excludes2 at L00-L99

At L00-L99, an Excludes2 note indicates if any of these conditions are documented in addition to the pilonidal cyst with abscess (L05.01) or in addition to the pilonidal cyst without abscess (L05.91), they should be reported as follows:

  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • lipomelanotic reticulosis (I89.8)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)

Now we are done!

Upon reviewing all of these notes, we can now be certain that we have our correct codes based on the documentation. The coding examples I provided were pretty simple and straightforward, but this is not always the situation.  

My point: Review all “Code First”, “Use Additional”, “Includes”, and “Excludes” notes before selecting the appropriate codes, because they all mean something.

ICD-10-CM codes for pilonidal cyst, L05.01 and L05.91 for with and without abscess

Disease Process of Pilonidal Cyst

To accurately and efficiently code for ICD-10-CM for pilonidal cysts, it’s important to understand the disease process (pathophysiology).

The following explains the signs and symptoms, causes, diagnosis, and treatment.

Signs and Symptoms

A pilonidal cyst, when infected, turns into a swollen mass. Signs and symptoms of an infected pilonidal cyst include:

  • Pain
  • Reddening of the skin
  • Pus or blood drainage from an opening in the skin
  • Foul odor from the pus drainage


The exact cause of pilonidal cysts is unknown, but loose hairs that protrude through the skin seem to be the main cause. 

This can occur in the following situations:

  • Skin rubbing against skin
  • Tight clothing
  • Riding a bicycle
  • Sitting for long periods

These situations force the hair down into the skin. The body looks at this as a foreign substance and creates a cyst around the hair.  

Risk Factors

Certain factors increase the odds of developing pilonidal cysts, such as:

  • Male
  • Individuals in their 20’s
  • Obesity
  • Inactive lifestyle
  • Job that requires long periods of sitting 
  • Excess body hair
  • Stiff or coarse hair


A chronically infected pilonidal cyst that isn’t properly treated may put a person at a slightly higher risk of developing squamous cell carcinoma.


The physician will ask the patient about the symptoms and then perform a physical examination of the area. If it is a primary care physician, he or she may refer the patient to a dermatologist or surgeon. 

According to Medicinenet.com, blood tests may need to be performed to diagnose an infection if severe. Imaging tests are not usually required. 


An infected pilonidal cyst is usually treated initially in the physician’s office. An incision and drainage (I&D) is performed to open and drain the cyst. 

A more extensive surgical procedure may be needed to remove the abscess if the cyst returns. This is known as a pilonidal cystectomy. 

Once the surgery is completed, the physician may elect to leave the wound open and allow it to heal, or close the wound with sutures. 

Dressings will need to be changed after surgery, and the patient may need to shave around the site to keep hairs from getting inside the wound. 


Now that you know how to locate and verify the diagnosis codes for pilonidal cysts (L05.01, L05.91) and understand the related ICD-10-CM coding guidelines, you should have no problem coding for this condition.

The main thing to look for in the documentation is whether it is “with abscess” or “without abscess.” Then be sure to review all the instructional notes to make sure your codes are correct and complete.

Having knowledge of the pilonidal cyst disease process also helps to better abstract the pertinent information from the physician’s documentation in order to accurately code.

Incision and Drainage of Pilonidal Cyst Coding

Now that you have learned how to code for pilonidal cysts in ICD-10-CM, check your knowledge of CPT coding for an incision and drainage of a pilonidal cyst in this Coding Challenge.

diagnosis coding for pilonidal cysts

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