CPT code 43845 – Gastric restriction with duodenal switch

Key takeaways

CPT 43845 covers open biliopancreatic diversion with duodenal switch: a partial gastrectomy plus a pylorus-preserving duodenoileostomy and ileoileostomy, billed as one line.

It is not a Roux-en-Y gastric bypass, which is 43846 or 43847, and laparoscopic BPD/DS usually goes to unlisted 43659 per payer policy.

E66.01 leads the diagnosis list, with the matching Z68 BMI code and every documented comorbidity listed after it.

Medicare covers 43845 under NCD 100.1, and facilities no longer need Center of Excellence certification for dates of service on or after September 24, 2013.

Pabau’s claims management software tracks prior authorizations and routes claims electronically through Claim.MD.

CPT code 43845 is the open duodenal switch code

CPT code 43845 reports an open biliopancreatic diversion with duodenal switch (BPD/DS), with both the restrictive and the malabsorptive halves billed as one procedure.

AAPC’s CPT 43845 listing places it under Other Procedures on the Stomach (43800-43999), inside the digestive system surgery range. Its official descriptor is a gastric restrictive procedure with partial gastrectomy, pylorus-preserving duodenoileostomy and ileoileostomy (50 to 100 cm common channel) to limit absorption.

In plain terms, the surgeon removes part of the stomach, divides the duodenum just past the pylorus and joins it to the ileum. A second anastomosis, the ileoileostomy, leaves a short common channel where food meets bile. The AMA’s CPT code set owns the descriptor, and our CPT codes library lists the neighboring stomach procedures.

Both halves of the operation sit inside one 43845 line

CPT 43845 bundles the partial gastrectomy and the duodenoileal reconstruction into a single billable unit. Split them onto separate claim lines and the National Correct Coding Initiative (NCCI) edits deny the claim. That includes the sleeve gastrectomy code, 43775, which NCCI bundles into 43845.

Some work at the same session still falls outside the code. The right-hand column below is what you report separately, with the appropriate modifier.

SADI-S and laparoscopic duodenal switch often go to 43659

43845 describes the open procedure. Laparoscopic BPD/DS is commonly reported with unlisted 43659 per payer policy. Single anastomosis duodeno-ileal bypass with sleeve (SADI-S) is split the same way.

Some payers accept 43845 because SADI-S still creates a duodenoileal anastomosis. Others want 43659, since SADI-S uses one anastomosis rather than the two the descriptor implies.

• Check the payer’s medical policy before you bill SADI-S as 43845.
• When you use 43659, attach a letter of medical necessity and the operative report.
• Check the American Society for Metabolic and Bariatric Surgery (ASMBS) for its current position on SADI-S coding before you submit.

43846 is the code most often billed in its place

The most common code-selection error on these claims is reporting 43846 for a duodenal switch. The two operations differ in anatomy, mechanism and anastomosis configuration.

A wrong pick also changes the expected payment and the NCCI edits that apply. Read the operative note for the anatomy, then match it against the five options below.

E66.01 leads the diagnosis list on a 43845 claim

E66.01 (morbid obesity due to excess calories) is the primary diagnosis for a CPT 43845 claim. Report E66.09 (other obesity) or the nonspecific E66.9 as primary, and most payers deny for medical necessity.

Those codes don’t meet their clinical criteria for bariatric surgery. Clear medical billing documentation of the obesity class keeps the diagnosis right from chart to claim.

The operative note has to show both components

The operative report is the most scrutinized document in a 43845 audit. It must show that the surgeon performed both the gastric restriction and the intestinal bypass.

A report that describes only the gastrectomy, with no duodenoileal anastomosis, won’t support 43845 and gets downgraded to 43775. Sound billing compliance requirements mean the chart backs both components before the claim goes out.

• Pre-operative workup: A BMI calculation dated within 6 months of surgery, psychological clearance and nutritional counseling records (typically 3-6 months). Add the history of failed conservative weight loss.
• Comorbidity documentation: Physician notes confirming each diagnosed comorbidity (diabetes, hypertension, sleep apnea, hyperlipidemia) with its current treatment.
• Operative note components: The gastrectomy technique and bougie size, duodenal transection point, common channel length, limb measurements, anastomosis technique, leak test result and closure.
• Informed consent: A signed consent specific to BPD/DS, showing the patient understands the malabsorptive component and lifelong supplementation.
• Post-operative plan: The follow-up schedule and supplementation protocol in the discharge summary.

Prior authorization has to clear before the OR date

Nearly every commercial payer and Medicare Advantage plan requires prior authorization for 43845. Submitting without a confirmed approval is the most common denial cause for this code. Requirements vary by payer, so never lean on an approval another payer issued for the same patient.

Most commercial payers build their criteria around these thresholds. Confirm each one against the payer’s current medical policy.

• BMI 40 or above, or BMI 35 or above with at least one documented obesity-related comorbidity
• Documented failure of a supervised non-surgical weight loss program (typically 3-6 months)
• Psychological clearance from a licensed mental health professional
• Nutritional counseling records covering the pre-operative period
• Medical clearance from the patient’s primary care provider
• No active substance use disorder or uncontrolled psychiatric condition

Medicare’s National Coverage Determination (NCD 100.1) covers bariatric surgery for beneficiaries with a BMI of 35 or more and at least one obesity-related comorbidity. Facilities are no longer required to be certified, since NCD 100.1 dropped that condition for dates of service on or after September 24, 2013.

Traditional Medicare doesn’t require prior authorization for 43845. Medicare Advantage plans set their own rules and commonly do.

Medicare pays about $1,510 for 43845 before locality adjustment

Medicare covers CPT code 43845 under NCD 100.1 for beneficiaries who meet the BMI and comorbidity criteria above. The surgeon’s professional claim goes on the CMS-1500 (837P), and the hospital bills its facility charges on the UB-04.

2026 fee schedule and relative value units

The 2026 Medicare Physician Fee Schedule (MPFS) values for CPT 43845 are below. They are national amounts before the geographic practice cost index (GPCI) is applied. Use the CMS Physician Fee Schedule lookup tool or the FastRVU 2026 lookup tool for your locality’s rate.

Commercial rates for 43845 often run above Medicare, but they vary widely by market and contract. Check the contracted rate in each payer agreement before you estimate expected payment.

Modifiers change what a 43845 claim pays

Modifier selection on a 43845 claim affects both payment and audit exposure. Claims management software like Pabau helps your biller track the claim from the encounter to submission. Check modifier rules against the operative note.

How a 43845 claim moves from consult to payment

A duodenal switch claim starts months before surgery. Each step below hands something to the next one, and a weak link shows up later as a denial.

1. Workup. The program documents BMI, comorbidities, counseling and psychological clearance in the chart.
2. Authorization. The office submits the request with that workup and records the approval number, its dates and the approved CPT code.
3. Surgery. The surgeon dictates an operative note that names each anastomosis and the common channel length.
4. Coding. The coder matches the note to 43845, lists E66.01 first, adds the Z68 code and comorbidities, then sets any modifiers.
5. Submission. The professional claim goes out as an 837P through the clearinghouse, with the authorization number on it.
6. Remittance. The ERA comes back, and the biller posts payment or works the denial against the global period.

Why 43845 claims get denied, and how to stop it

A 43845 claim needs three things in place: an approved authorization, exact diagnosis coding and complete operative documentation. Miss any one and the claim comes back denied. Structured denial management workflows catch these problems before submission rather than after the remittance arrives.

Bundling and unbundling rules

CMS NCCI edits bundle the sleeve gastrectomy code (43775) into 43845, so billing both on the same date of service brings an automatic denial. Pabau routes claims through the Claim.MD clearinghouse for electronic submission and remittance. Verify NCCI edits in the CMS tool before billing any second code on the same claim as 43845.

Before you submit: a 43845 checklist

• The operative note names the partial gastrectomy, the duodenoileostomy, the ileoileostomy and the common channel length.
• The approach was open; a laparoscopic case is checked against the payer’s 43659 policy.
• The authorization number, approved code and date range match the claim.
• E66.01 is first, followed by the Z68 BMI code and every documented comorbidity.
• No 43775 line sits on the same date of service.
• Modifiers 80 and AS match who actually assisted.

How Pabau keeps 43845 authorizations and claims on track

Bariatric billing usually lives across a spreadsheet of authorizations, a shared inbox and the surgeon’s dictation queue. That’s where an approval number goes missing or a claim leaves before sign-off.

In Pabau, the authorization code, its dates and the approved sessions sit on the patient’s case, with a warning when one is missing. Claims go out electronically through Claim.MD as CMS-1500/837P files, with eligibility checks before the visit and ERA remittances posted back.

Your team sees each 43845 claim’s status in one place, so a denial gets worked while the global period is still open.

Keep bariatric authorizations and claims in step

Pabau tracks each prior authorization on the patient’s case and routes claims electronically through Claim.MD. Your billing team spends its time on complex cases rather than chasing paperwork.

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Conclusion

Most 43845 denials trace back to a decision made before the claim was built. Someone read “duodenal switch” and picked a bypass code, or scheduled the case before the authorization cleared.

Make the operative note the deciding document. If it names an open partial gastrectomy, both anastomoses and a 50 to 100 cm common channel, bill 43845 with E66.01 first. If it doesn’t, query the surgeon before you code.

To see how Pabau tracks authorizations and routes bariatric claims through Claim.MD, book a demo.

Continue your research

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