Diagnosis Coding For Pilonidal Cysts Need Not Be Painful

coding for pilonidal cysts
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** This article was reviewed and updated on December 16, 2023. **

Accurate diagnosis coding for pilonidal cysts is essential for medical coders. This comprehensive guide will explain the nuances of ICD-10-CM coding for these pockets of skin, offering insights into coding scenarios, guidelines, and the disease process. By the end, you will be equipped with the knowledge to report for pilonidal cysts confidently.

Understanding Pilonidal Cysts

Pilonidal cysts are abnormal pockets in the skin, typically found near the tailbone at the top of the cleft of the buttocks. According to the Mayo Clinic, these cysts may contain hair and skin debris and can become painful abscesses when infected. Coders must understand the disease process to ensure accurate coding. 

Coding Exercise – Pilonidal Cyst With Abscess (L05.01)

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 (connective tissues) (embolic) (fistulous) (infective) (metastatic) (multiple) (pernicious) (pyogenic) (septic)/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 (colloid) (mucous) (simple) (retention)/pilonidal (infected) (rectum)/Pilonida cyst 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 (L05.91)

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)/pilonidal (infected) (rectum), L05.91. This is the default code. Or we can go further down the list and see that a 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 synonyms are specified in the documentation, we can locate the same code (L05.91) using different search terms.

Review the Instructional Notes

Before we can be sure we are done coding for the above two coding examples, we must review all the notes provided for each code 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 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 indicates 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 note indicates we must 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 these notes, we can now be sure that we have the correct codes based on the documentation.

Always review all “Code First,” “Use Additional,” “Includes,” and “Excludes” notes before selecting the appropriate codes because they all mean something.

coding for pilonidal cysts

Disease Process of Pilonidal Cyst

To accurately and efficiently code for ICD-10-CM for pilonidal cysts, it’s essential to understand the disease process (pathophysiology). The Mayo Clinic reports the following symptoms, causes, diagnosis, and treatment of pilonidal cysts.

Symptoms of Pilonidal Cysts

A pilonidal cyst does not always cause symptoms. However, if it becomes infected, the skin surrounding the cyst may become swollen and painful. Symptoms of an infected pilonidal cyst include:

  • A pit close to the top of the buttocks crease
  • Pain and inflamed, swollen skin
  • Pus or blood drainage from an opening in the skin
  • Foul odor from the pus drainage

Causes of Pilonidal Cysts

Loose hairs that protrude through the skin are the leading cause. This can occur due to friction and pressure from skin rubbing against skin, tight clothing, riding a bicycle, or sitting for long periods. These situations force the hair down into the skin, and the body looks at this as a foreign substance, creating a cyst around the hair.  

Risk Factors

Individuals who have a higher risk of developing a pilonidal cyst are:

  • Young adult white males
  • Overweight
  • Inactive
  • Sit for long periods
  • With thick, stiff body hair


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

Diagnosing Pilonidal Cysts

The physician will ask the patient about the symptoms and then physically examine the area. If it is a primary care physician, they 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 leave the wound open and allow it to heal or close it 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, review all the instructional notes to ensure your codes are correct and complete. Knowledge of the pilonidal cyst disease process also helps to better abstract the pertinent information from the physician’s documentation to code accurately.

Incision and Drainage of Pilonidal Cysts in CPT

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.

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