CPT Code 45378: Colonoscopy, diagnostic, including collection of specimens by brushing or washing, with or without colon decompression

What is CPT code 45378?

CPT code 45378 is a colonoscopy procedure code used to report a diagnostic colonoscopy—a procedure involving direct visualization of the entire colon, from the rectum to the cecum, using a colonoscope. The physician may collect specimens by brushing or washing during the procedure, and colon decompression may be performed if indicated. This code is used when the colonoscopy is intended to evaluate a medical issue, rather than to conduct a colorectal cancer screening test.

CPT 45378 is appropriate when a patient presents with symptoms or abnormal findings that require further investigation. These may include rectal bleeding, chronic diarrhea or constipation, iron-deficiency anemia, abdominal pain, or a positive fecal occult blood test, provided the test was not ordered as part of a routine screening. It also applies to surveillance colonoscopies conducted to monitor previously identified abnormalities, such as polyps, inflammatory bowel disease, or colorectal lesions. These procedures are considered diagnostic or therapeutic services, depending on the outcome, and not preventive.

It is important to note that CPT 45378 should not be used to report a colorectal cancer screening colonoscopy performed as a preventive measure in asymptomatic individuals. Screening colonoscopies are typically coded using HCPCS codes G0105 or G0121, depending on the patient’s risk level.

Documentation requirements

Accurate and complete documentation is essential when billing CPT 45378. Providers must clearly establish the medical necessity of the colonoscopy and detail the scope and outcome of the procedure.

Reason for the procedure

The clinical indication must be specific and well documented. Common reasons include rectal bleeding, iron-deficiency anemia, chronic diarrhea, or a positive fecal occult blood test. If the colonoscopy is a follow-up to a previous abnormal finding, that should also be stated. Avoid labeling the procedure as “routine” unless it was performed as a screening, in which case CPT 45378 would not be appropriate.

Extent and findings

The procedural note must describe the anatomic reach of the colonoscopy (e.g., whether the cecum or terminal ileum was visualized). It should include any abnormalities identified—such as polyps, inflammation, or diverticulosis—and whether the exam was complete or had limitations (e.g., due to poor prep).

Specimen collection details

If specimens were collected by brushing or washing, this should be clearly documented. Specify the method of collection, the site, the reason for sampling, and whether the samples were sent for pathology or culture.

Sedation or anesthesia

Note the type and level of sedation used (conscious, deep, monitored anesthesia care), the provider responsible, and the patient’s response to sedation. This is particularly important if separate anesthesia services are billed.

Post-procedure notes

Include any immediate assessment and recommendations, including whether further testing, surveillance, or treatment is needed. If no abnormalities were found, reiterate that the procedure was medically necessary based on the presenting symptoms.

Billing guidelines

CPT 45378 is used for colonoscopies to evaluate signs, symptoms, or known abnormalities. It does not apply to routine screening procedures.

When to use CPT 45378

Use CPT 45378 when the procedure is diagnostic. This includes patients presenting with symptoms (e.g., bleeding, anemia), follow-up of abnormal test results, and surveillance of known pathology (e.g., previous polyps or IBD). Although no abnormalities are found during the procedure, 45378 is still valid if the initial intent was diagnostic.

Modifier usage

Use modifier PT on Medicare claims when a screening colonoscopy becomes diagnostic or therapeutic, as this ensures correct cost-sharing for the beneficiary.

Appropriate diagnosis codes

Match CPT 45378 with a diagnosis that justifies a diagnostic procedure. Common examples include:

• R19.5: Other fecal abnormalities
• D50.9:  Iron deficiency anemia, unspecified
• K59.1 : Functional diarrhea
• K62.5:  Hemorrhage of anus and rectum

Commercial and Medicaid payer notes

Unlike Medicare, commercial and Medicaid payers may vary in how they interpret and reimburse CPT codes. Some may accept G-codes for screening procedures, while others prefer CPT 45378 paired with a Z-code and modifier 33. Certain payers may also require prior authorization or the use of specific documentation templates. Additionally, cost-sharing rules can differ between plans. Because of these variations, it is essential to confirm payer-specific guidelines before submitting claims.

Other relevant CPT codes

• 45379: Colonoscopy with removal of foreign body(s)
• 45380: Colonoscopy with biopsy, single or multiple
• 45381: Colonoscopy, flexible; with directed submucosal injection(s), any substance
• 45382: Colonoscopy with control of bleeding