CPT Code 45330: Diagnostic Flexible Sigmoidoscopy Billing Guide for 2026

What Is CPT Code 45330?

CPT code 45330 is a lower GI endoscopy code that reports a diagnostic flexible sigmoidoscopy, an exam of the rectum and sigmoid colon that can include specimen collection by brushing or washing. It is the base code for the 45330 to 45350 sigmoidoscopy family and a separate procedure. In 2026, Medicare’s national rate is $215.10 in the office and $53.78 in a facility.

45330 vs G0104: Medicare screening sigmoidoscopy uses G0104, covered every 48 months from age 45, while commercial screening is typically billed as 45330 with modifier 33 and a Z12 screening code.

Incomplete colonoscopy: A colonoscopy that cannot reach the cecum in a patient prepped for it is billed as 45378-53, not 45330, which is reserved for a planned sigmoidoscopy.

Biopsy or polyp removal: Once a biopsy or polypectomy is done, bill the therapeutic code, such as 45331 or 45338, because 45330 is bundled as the family’s base code.

What 45330 Covers and When It Applies

The AMA’s CPT descriptor defines 45330 as a diagnostic flexible sigmoidoscopy that includes specimen collection by brushing or washing when performed, and it labels the code a separate procedure. CPT defines sigmoidoscopy as an exam of the entire rectum and sigmoid colon that may include part of the descending colon, which separates it from a proctosigmoidoscopy of the rectum and sigmoid only (45300) and from a colonoscopy, which must reach the cecum.

Two parts of that descriptor drive billing. Brushing and washing are included, so a cytology brushing never adds a code, while a forceps biopsy moves the claim to 45331. The separate procedure label means 45330 is not reported with a more extensive procedure in the same area, such as a colonoscopy, unless it was a distinct service. The procedure note should state how far the scope advanced, in centimeters or by landmark, because the extent of the exam is what separates a sigmoidoscopy from an incomplete colonoscopy.

Typical diagnostic indications include rectal bleeding (K62.5), a change in bowel habit (R19.4), diarrhea (R19.7), surveillance of ulcerative rectosigmoiditis (K51.30), and evaluation of a rectal polyp (K62.1). A flexible sigmoidoscopy with balloon dilation is a different code, 45340, a common point of confusion; the rigid proctosigmoidoscopy version with dilation is 45303.

Setting changes payment sharply. The 2026 national rate is $215.10 when 45330 is performed in the office and $53.78 in a facility, where the ASC or hospital bills its own fee. Moderate sedation is not bundled into GI endoscopy codes, so when the endoscopist provides it, 99152 reports the first 15 minutes, at $51.44 in the office.

What Is the Difference Between 45330 and G0104?

45330 reports a diagnostic flexible sigmoidoscopy, while G0104 is the HCPCS code Medicare uses for a screening flexible sigmoidoscopy in a patient without symptoms. Medicare covers G0104 once every 48 months starting at age 45, with no cost sharing. Commercial payers usually take 45330 for screening instead, with modifier 33 and a Z12 screening diagnosis.

Medicare adds a timing rule: a patient who is not high risk and had a screening colonoscopy (G0121) qualifies for G0104 only after 119 months have passed. When a screening sigmoidoscopy turns into a biopsy or polypectomy, the claim moves to the therapeutic code, such as 45331, with modifier PT. The Part B deductible still does not apply, and the patient’s coinsurance is 15% through 2026, drops to 10% for 2027 through 2029, and reaches zero in 2030.

For commercial plans, screening sigmoidoscopy is generally an Affordable Care Act preventive service when billed with modifier 33 and Z12.11 or Z12.12, though plans differ on how they handle a screening exam that becomes diagnostic.

Here is how 45330 compares with the codes it is most often confused with:

Code	What it reports	2026 national rate (office / facility)
45330	Diagnostic flexible sigmoidoscopy	$215.10 / $53.78
G0104	Medicare screening flexible sigmoidoscopy	$214.77 / $53.44
45331	Flexible sigmoidoscopy with biopsy	$322.99 / $66.80
45300	Rigid proctosigmoidoscopy, diagnostic	$148.63 / $45.09
45378	Diagnostic colonoscopy	$378.10 / $164.67
45378-53	Incomplete colonoscopy, patient prepped	$189.38 / $82.50

National amounts from the CMS 2026 Physician Fee Schedule relative value file (October release) at the $33.4009 conversion factor, before geographic adjustment.

How Do You Code an Incomplete Colonoscopy: 45330 or 45378-53?

Code by intent. If the patient was scheduled and prepped for a colonoscopy and the scope could not reach the cecum, CPT directs 45378 with modifier 53, even if the exam stopped in the sigmoid colon. Report 45330 only when the physician planned a sigmoidoscopy. Screening colonoscopies that stop early use G0121-53 or G0105-53 for Medicare.

One question we hear constantly from practice managers is whether a colonoscopy stopped at the splenic flexure becomes a sigmoidoscopy. Before 2015, CPT treated a colonoscopy that did not pass the splenic flexure as incomplete, and Medicare paid it at the sigmoidoscopy rate. CPT 2015 redefined an incomplete colonoscopy as one that does not reach the cecum in a patient prepared for the full exam, and CMS followed in 2016: under Transmittal R3368CP and the Claims Processing Manual, Chapter 12, Section 30.1, Medicare pays 45378-53 at one-half the value of the code’s inputs.

The difference shows up in 2026 payment. In a facility, where colonoscopies are usually performed, 45378-53 pays $82.50 nationally against $53.78 for 45330, so coding the aborted exam as a sigmoidoscopy underpays the physician by $28.72 each time. In the office the relationship flips, $189.38 against $215.10, which is exactly why the code must follow intent rather than payment.

Two variations matter. If the physician performed a biopsy or polypectomy before stopping, CPT calls for the therapeutic colonoscopy code with modifier 52 instead of 53. The facility claim uses its own modifiers, 73 or 74, depending on whether the procedure stopped before or after anesthesia.

In our experience matching providers with billing partners, intent-based coding like this is a frequent source of avoidable rework for GI practices that code in-house.

How Does the Multiple Endoscopy Rule Apply to 45330?

45330 is the base code for the flexible sigmoidoscopy family, codes 45331 through 45350. When two or more codes from the family are billed in one session, Medicare pays the highest-valued code in full and each additional code at its value minus the 45330 base. 45330 itself is not billed when any other family code is reported.

Here is how that plays out for a biopsy (45331) and a snare polypectomy (45338) in one session. In the office, 45338 pays $335.01, and 45331 adds $107.89, its $322.99 value minus the $215.10 base, for a total of $442.90. In a facility, the same pair pays $108.89 plus $13.02, or $121.91. Billing either code alone leaves the increment unpaid, and billing 45330 on top of them invites a bundling denial.

Procedures from different families follow a different rule. An upper endoscopy and a sigmoidoscopy on the same day are two separate families, so each family is priced first and then the standard multiple procedure reduction pays the lower-valued family at 50%. Our CPT 43235 guide covers the upper GI base code that anchors that second family. Colonoscopy is its own family as well, with 45378 as its base, which is why 45330 does not accompany a colonoscopy for the same patient on the same day.

Advanced resections need care too. Endoscopic mucosal resection in the sigmoid reports with 45349, while lesions removed by endoscopic submucosal dissection are moving to dedicated Category I codes on January 1, 2027 rather than unlisted codes; our breakdown of the new ESD CPT codes for 2027 covers that change.

Diagnosis Codes That Support 45330

Providers often come to us after sigmoidoscopy denials that trace back to the diagnosis rather than the scope. A diagnostic 45330 needs a symptom or condition code that explains the exam, such as K62.5 for rectal bleeding, R19.4 for a change in bowel habit, or K57.30 for diverticulosis, while a screening code on a diagnostic claim signals a mismatch payers catch.

Surveillance is its own category. A patient with a personal history of adenomatous or serrated polyps carries Z86.0101, part of the Z86.010- subcategory that now separates adenomatous and serrated, hyperplastic, and other polyps, and a family history of colorectal cancer adds Z80.0. Commercial plans differ on whether surveillance counts as preventive, so verify benefits before the procedure.

Screening sigmoidoscopies lead with Z12.11 for the colon or Z12.12 for the rectum. When a finding turns the exam diagnostic, keep the screening code first and add the finding, such as D12.5 for a benign neoplasm of the sigmoid colon, so the payer sees why the exam started and what it found. Code to the highest specificity the report supports: a rectal polyp is K62.1 until pathology confirms an adenoma, which then codes to D12.8.

None of these codes changed in the FY2027 update that took effect October 1, 2026, although FY2027 did add Z86.17 for a personal history of Clostridioides difficile infection, which can matter when a sigmoidoscopy evaluates recurrent colitis. Some GI practices hold sigmoidoscopy claims with biopsies until pathology returns, so the final diagnosis is coded once instead of corrected later.

Why Do 45330 Claims Get Denied?

45330 claims often deny over bundling, intent, and screening rules rather than medical necessity. Common causes include billing 45330 with a colonoscopy or another sigmoidoscopy family code, coding an aborted colonoscopy as a sigmoidoscopy, billing 45330 to Medicare for a screening exam that should be G0104, and missing the PT or 33 modifier.

Watch for these seven errors:

• Billing 45330 with a colonoscopy. A colonoscopy includes the sigmoid exam, so 45330 bundles into 45378 and its family.
• Stacking the base code. 45330 is not billed alongside 45331, 45338, or any other family code from the same session.
• Coding an aborted colonoscopy as 45330. A patient prepped for colonoscopy gets 45378-53, or modifier 52 on the therapeutic code if therapy was performed.
• Sending Medicare screening as 45330. Medicare expects G0104 for a screening sigmoidoscopy in an asymptomatic patient.
• Missing the frequency window. G0104 repeats only after 48 months, or 119 months after a screening colonoscopy for patients who are not high risk.
• Dropping the conversion modifier. A screening exam that becomes a biopsy needs PT for Medicare or the payer’s screening modifier, often 33, for commercial plans.
• Confusing rigid and flexible scopes. A rigid proctosigmoidoscopy reports with 45300, not 45330.

Each of these errors is visible in the procedure note, so a coder review before submission catches them.

The most common issue we see providers run into is a sigmoidoscopy with both a biopsy and a snare polypectomy billed as one line. Consider an office-based practice that performs 15 of those sessions a month. Billing only 45338 forfeits the 45331 increment of $107.89 per session at the 2026 national rate, or $1,618.35 a month and $19,420.20 a year.

Frequently Asked Questions

Next Steps

• Planning for 2027 lower GI resections? Review the new ESD CPT codes for 2027.
• Billing an EGD and a sigmoidoscopy on the same day? See the CPT 43235 diagnostic EGD guide.
• Adding liver stiffness testing to GI visits? Read the 91200 liver elastography billing guide.