CPT
31237 — Nasal/sinus endoscopy, surgical; with biopsy, polypectomy, or debridement
Verify the code matches the actual service and dose.
ENT
31231 — Nasal endoscopy, diagnostic, unilateral or bilateral
This code covers diagnostic nasal endoscopy, in which a physician inserts a small scope into the nasal passages to visually examine the nasal cavity, turbinates, and nasopharynx.
- Typical setting: Hospital OR, ENT clinic
- National avg charge (illustrative): $90-$180 Medicare allowed (approx. $95-$150 national Medicare average; commercial payers $130-$250)
- Most-disputed reason: Billing diagnostic when surgical was performed: if any surgical procedure (polyp removal, biopsy, cautery) was performed, a surgical endoscopy code must be used — 31231 is diagnostic only
What it means
What 31231 actually means
This code covers diagnostic nasal endoscopy, in which a physician inserts a small scope into the nasal passages to visually examine the nasal cavity, turbinates, and nasopharynx. It is used to evaluate nasal obstruction, polyps, sinusitis, and other nasal conditions. No surgical intervention is performed under this code — it is diagnostic only.
Common errors with this code
What goes wrong on real bills.
Most bills that look correct still contain at least one of these issues. Up to 49% of medical bills contain errors (CFPB).
- Billing diagnostic when surgical was performed: if any surgical procedure (polyp removal, biopsy, cautery) was performed, a surgical endoscopy code must be used — 31231 is diagnostic only
- Unbundling: billing 31231 on the same day as a surgical nasal or sinus endoscopy code when the diagnostic scope was inherent to the surgical procedure
- Bilateral billing error: 31231 covers unilateral or bilateral examination — billing two units of 31231 for both nostrils is incorrect
If you see 31231 on your bill
Three steps before paying.
1. Get the itemized bill. If your statement only shows a summary, request the CPT-level itemized bill before paying. Generate the request language →
2. Cross-check against the EOB. Compare what your insurer's Explanation of Benefits says you owe versus what the hospital is asking. They disagree more often than people think. Read the bill-vs-EOB guide →
3. Run a free Bill Scan. Upload the bill (and EOB if you have it) and BillBusted will flag the most likely issues with this specific code in your specific state. Run free scan →
Related codes
Other codes in this category.
People who land on 31231 often also see these adjacent codes on the same bill.
CPT
36415 — Routine venipuncture for collection of specimen
Verify the code matches the actual service and dose.
CPT
36416 — Collection of capillary blood specimen, finger, heel, or ear stick
Verify the code matches the actual service and dose.
CPT
38221 — Bone marrow biopsy, needle; first sampling
Verify the code matches the actual service and dose.
Related BillBusted guides
Plain-English reads if you see 31231 on a bill.
31231 FAQ
Plain-English answers.
What does 31231 usually cost?
$90-$180 Medicare allowed (approx. $95-$150 national Medicare average; commercial payers $130-$250). Costs vary by region, payer contract, and whether the service was performed in a hospital outpatient department (which adds a facility fee) versus a free-standing clinic.
What's the most common billing error on 31231?
Billing diagnostic when surgical was performed: if any surgical procedure (polyp removal, biopsy, cautery) was performed, a surgical endoscopy code must be used — 31231 is diagnostic only
What should I do if I see 31231 on my bill?
Request the itemized bill and the matching EOB from your insurer. Compare the units/quantity billed against what you actually received. Run a free BillBusted scan to flag the most likely errors specific to 31231 before paying.
Don't pay 31231 blindly.
The free scan tells you in under 60 seconds whether this charge looks reasonable for your situation.