Summary & Overview
CPT 43645: Laparoscopic Gastric Bypass with Small Intestine Reconstruction
CPT code 43645 is a critical billing code for laparoscopic gastric bypass surgery with small intestine reconstruction, a procedure widely used in the treatment of severe obesity. This code is central to bariatric surgery programs across the United States, reflecting the growing demand for surgical interventions that address obesity and its related health risks. The procedure is typically performed in an inpatient hospital setting and is recognized by major national payers, including Aetna, Blue Cross Blue Shield, Cigna Health, Medicare, and UnitedHealthcare.
This publication provides a comprehensive overview of CPT code 43645, including payer coverage, clinical context, and policy updates relevant to bariatric surgery. Readers will gain insight into the procedure's role in obesity management, the typical patient population, and the importance of accurate coding for reimbursement and compliance. The analysis also highlights benchmarks and trends in payer policies, offering a clear understanding of how this code is utilized in clinical practice and its impact on healthcare delivery. Key modifiers and associated taxonomies are discussed to ensure clarity in billing and documentation. This resource is designed for healthcare professionals, administrators, and policy analysts seeking up-to-date information on bariatric surgery coding and coverage.
CPT Code Overview
CPT code 43645 describes a laparoscopic surgical gastric restrictive procedure that includes gastric bypass and small intestine reconstruction to limit absorption. This procedure is a form of bariatric surgery designed to help patients with severe obesity achieve significant weight loss by reducing the size of the stomach and rerouting the small intestine. The typical site of service for this procedure is an inpatient hospital setting, specifically at Place of Service 21.
Clinical & Coding Specifications
Clinical Context
A typical patient scenario involves an adult with morbid obesity, often defined by a body mass index (BMI) of 40 or greater, or a BMI of 35 or greater with associated comorbidities. The patient has failed to achieve significant weight loss through conservative measures such as diet, exercise, and medical management. After multidisciplinary evaluation, the patient is scheduled for a laparoscopic gastric bypass procedure with small intestine reconstruction to limit absorption. The procedure is performed in an inpatient hospital setting, with preoperative assessment, surgical intervention, and postoperative monitoring for complications and nutritional status.
Coding Specifications
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Modifier
22: Increased Procedural Services. Used when the procedure requires substantially greater effort due to factors such as patient complexity or intraoperative findings. -
Modifier
51: Multiple Procedures. Used when more than one surgical procedure is performed during the same operative session.
| Modifier Code | Description |
|---|---|
22 | Increased Procedural Services |
51 | Multiple Procedures |
- Provider Taxonomies:
| Taxonomy Code | Specialty Name |
|---|---|
208600000X | Surgery Physician |
208D00000X | General Practice Physician |
208B00000X | Obesity Medicine Physician |
These taxonomies represent providers specializing in surgery, general practice, and obesity medicine, all of whom may be involved in the care and management of bariatric surgery patients.
Related Diagnoses
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E66.01: Morbid (severe) obesity due to excess calories- Indicates the primary clinical reason for bariatric surgery, reflecting severe obesity that is resistant to conservative management.
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Z68.35: Body mass index [BMI] 35.0‑35.9, adult- Used to document BMI in the range qualifying for bariatric surgery with comorbidities.
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Z68.36: Body mass index [BMI] 36.0‑36.9, adult- Documents BMI in the qualifying range for surgical intervention.
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Z68.37: Body mass index [BMI] 37.0‑37.9, adult- Indicates BMI relevant for surgical eligibility.
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Z68.38: Body mass index [BMI] 38.0‑38.9, adult- Used for patients with BMI in this range, supporting medical necessity.
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Z68.39: Body mass index [BMI] 39.0‑39.9, adult- Documents BMI just below the threshold for morbid obesity.
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Z68.41: Body mass index [BMI] 40.0‑44.9, adult- Indicates morbid obesity, a primary indication for bariatric surgery.
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Z68.42: Body mass index [BMI] 45.0‑49.9, adult- Used for patients with higher BMI, supporting surgical intervention.
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Z68.43: Body mass index [BMI] 50.0‑59.9, adult- Documents extreme obesity, reinforcing clinical necessity.
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Z68.44: Body mass index [BMI] 60.0‑69.9, adult- Indicates super morbid obesity, often requiring surgical management.
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Z68.45: Body mass index [BMI] 70 or greater, adult- Used for patients with extremely high BMI, supporting the need for bariatric surgery.
Each code documents the severity of obesity and supports the medical necessity for the procedure described by 43645.
Related CPT Codes
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43644: Laparoscopy, surgical, gastric restrictive procedure; with gastric bypass and Roux‑en‑Y gastroenterostomy (roux limb 150 cm or less)- This code describes a similar procedure to
43645, specifically for Roux-en-Y gastric bypass with a shorter roux limb. It is often used as an alternative depending on surgical technique.
- This code describes a similar procedure to
-
43770: Laparoscopy, surgical, gastric restrictive procedure; placement of adjustable gastric band (gastric band and subcutaneous port components)- This code represents a different type of bariatric surgery, used as an alternative to gastric bypass for weight loss.
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43771: Data not available in the input. -
43772: Data not available in the input. -
43773: Data not available in the input.
These codes are related to bariatric surgical procedures and may be used as alternatives or in conjunction with 43645 depending on patient needs and surgical approach.
National Reimbursement Benchmarks
Nationally, the mean rate for CPT code 43645 under Medicare is $1,727.06, while the average commercial benchmark (BUCA) is $2,530.47. This represents a difference of $803.41, with commercial rates significantly higher than Medicare. UnitedHealth Group has the highest mean rate at $3,305.15, and Cigna also stands out with a mean rate of $2,997.50.
Rate dispersion, measured by the difference between the 75th and 25th percentiles, varies across payers. Medicare shows the tightest range at $132.00, indicating relatively consistent rates. In contrast, UnitedHealth Group exhibits the widest dispersion at $1,957.00, reflecting substantial variability in contracted rates. Cigna and BUCA also display broad ranges, while Aetna and Blue Cross Blue Shield are more moderate.
The table and chart below present a detailed breakdown of national mean rates and percentile benchmarks for each payer.
Trek Health ingests and normalizes Transparency in Coverage data and payer policy updates to give provider organizations a clear view of how commercial reimbursement behaves across markets, payers, and services. Our platform transforms raw payer disclosures into structured intelligence that supports contract evaluation, payer negotiations, and service line strategy. By combining market benchmarks with ongoing policy visibility, Trek helps teams identify variability, risk, and opportunity in commercial reimbursement. The result is faster insight, stronger negotiating positions, and more informed financial decisions.