Introduction
Endometriosis is a common gynecologic condition in which tissue similar to the lining of the uterus grows outside the uterus, often causing pelvic pain, heavy menstrual bleeding, infertility, and pain during intercourse or bowel movements. For some patients, symptoms are managed with medications, but many eventually need surgery to remove endometriosis lesions, treat adhesions, or address related organ involvement.
For years, it has been unclear how much of endometriosis surgery is now being done in outpatient ambulatory settings rather than during a hospital admission. This matters because surgical setting can affect recovery, cost, patient selection, and the kinds of procedures that are performed. The study summarized here examined national trends in inpatient versus ambulatory surgery for endometriosis across the United States from 2016 to 2022.
Why the Surgical Setting Matters
Endometriosis surgery can range from relatively limited procedures to complex operations involving the ovaries, bowel, bladder, or multiple pelvic organs. Some patients can safely go home the same day after surgery, while others need hospital monitoring because of severe disease, higher medical complexity, or risk of complications.
Ambulatory surgery, also called outpatient surgery, usually means the patient has the procedure and goes home the same day. Inpatient surgery means the patient stays in the hospital after the operation. A shift toward outpatient care often reflects improved surgical techniques, better pain control, and more careful patient selection. However, it may also raise questions about whether patients with more severe disease are still receiving the level of care they need.
Study Design and Data Sources
This was a serial cross-sectional study, meaning the researchers examined repeated national snapshots over several years rather than following individual patients over time. They looked at surgeries from 2016 through 2022 with a primary diagnosis of endometriosis.
Two large national databases were used:
The National Inpatient Sample for hospital-based inpatient surgeries.
The Nationwide Ambulatory Surgery Sample for outpatient ambulatory surgeries.
The researchers used joinpoint regression to analyze trends over time and reported the average annual percent change, or AAPC. They also compared demographic features, disease distribution, surgical procedures, and complications between inpatient and ambulatory cases.
Key Findings: A Major Shift Toward Outpatient Surgery
A total of 70,535 weighted inpatient surgical encounters and 561,894 weighted ambulatory surgical encounters were identified nationwide between 2016 and 2022.
The most striking finding was the opposite trend in the two settings:
Inpatient surgical volume fell by 49%, from 14,080 cases in 2016 to 7,110 cases in 2022.
Ambulatory surgical volume rose by 17%, from 73,270 cases in 2016 to 85,896 cases in 2022.
In trend terms, inpatient surgery declined significantly each year, while outpatient surgery increased modestly but steadily. This suggests that endometriosis care is increasingly moving away from the traditional hospital admission model and into same-day surgical treatment.
Who Was More Likely to Have Inpatient Surgery?
Patients who underwent inpatient surgery tended to have more complex health and social profiles than those treated in ambulatory settings.
Compared with outpatient cases, inpatient cases were more likely to involve patients who were:
Older, with a median age of 40 years versus 37 years.
Medically more complex, reflected by a higher Elixhauser comorbidity index, a standard measure of overall illness burden.
More likely to have Medicaid insurance, 20% versus 16%.
More likely to live in the lowest median income ZIP code quartile, 26% versus 21%.
These findings suggest that socioeconomic factors and medical complexity both influence where surgery is performed. Patients with fewer resources or more chronic health conditions may be more likely to receive care in a hospital setting rather than an outpatient center.
Disease Severity Was Greater in Inpatient Cases
The study also found that patients undergoing inpatient surgery more often had endometriosis involving deeper or more extensive disease sites.
Compared with ambulatory cases, inpatient surgery more commonly involved:
The ovaries, 37% versus 26%.
The bowel, 10% versus 3%.
Multiple organs, 40% versus 30%.
Concurrent pelvic infection, 3.0% versus 1.4%.
Intraoperative complications were also more common in the inpatient group. This pattern fits with clinical experience: more advanced or anatomically complicated endometriosis is harder to remove and more likely to require postoperative monitoring, blood loss management, or multidisciplinary surgical support.
What Procedures Were Performed?
One of the most important findings was the distribution of hysterectomy with salpingo-oophorectomy, a procedure that removes the uterus, fallopian tubes, and ovaries. This was the most frequent inpatient procedure, but it was also very common in the ambulatory setting.
Overall, hysterectomy with salpingo-oophorectomy accounted for 61% of inpatient procedures and 47% of ambulatory procedures.
This is clinically meaningful because it shows that even relatively major gynecologic operations are increasingly being performed without hospital admission in selected patients. Over the study period, there was a significant movement of this operation from inpatient toward ambulatory care.
Several factors likely contribute to this shift, including minimally invasive surgical techniques, enhanced recovery protocols, shorter operative times in some centers, and improved anesthetic and postoperative pain management. Still, not all patients are appropriate candidates for same-day discharge, especially when disease is extensive or organ involvement is present.
Interpretation of the Results
The study shows a clear and important change in how endometriosis surgery is delivered in the United States. Outpatient surgery is now the dominant setting, while inpatient surgery is becoming less common.
This likely reflects a combination of improvements in gynecologic surgery and changes in health care delivery. Surgeons are increasingly able to perform complex procedures using laparoscopic or robotic approaches, which can reduce pain, lower complication rates, and speed recovery. At the same time, hospitals and surgical centers may be encouraging outpatient management whenever safe and appropriate.
However, the data also suggest that inpatient surgery remains essential for a subset of patients. Those with more advanced disease, more medical conditions, or socioeconomic barriers may still require or receive hospital-based care. The increasing outpatient trend should not be interpreted as meaning all endometriosis surgery can safely be moved outside the hospital.
Clinical and Public Health Implications
These findings have several implications for clinicians, patients, and health systems.
For clinicians, the study reinforces the importance of careful preoperative planning. Patients with bowel involvement, multiple affected organs, infection, or significant medical comorbidities may be better served in a hospital environment where additional support is available.
For patients, the results may be reassuring because outpatient surgery can often mean a shorter hospital stay, quicker return home, and potentially lower costs. However, the safest setting depends on the individual’s disease severity, overall health, and the expertise of the surgical team.
For health systems and policymakers, the study highlights persistent disparities. Patients with Medicaid insurance and those living in lower-income areas were more likely to undergo inpatient surgery. This may reflect differences in access, referral patterns, disease severity at presentation, or the availability of ambulatory surgical centers. Addressing these inequities could improve both quality and efficiency of care.
Strengths and Limitations
This study has important strengths. It used large, nationally representative databases and covered a seven-year period, allowing the researchers to describe real-world trends across the United States. The inclusion of both inpatient and ambulatory surgical datasets provides a broad view of modern endometriosis care.
There are also limitations. Administrative databases depend on billing codes, which can misclassify diagnoses or procedures. The analysis could not capture symptoms, patient preferences, surgeon skill, lesion completeness, long-term outcomes, recurrence, or quality of life. The databases also do not fully explain why one patient was treated inpatient while another had outpatient surgery.
In addition, the study reflects U.S. practice patterns and may not generalize directly to other countries, where surgical organization, insurance systems, and access to outpatient surgery differ.
Bottom Line
From 2016 to 2022, endometriosis surgery in the United States shifted substantially toward ambulatory care. Inpatient surgery became less common, while outpatient surgery increased. Patients treated in hospitals were generally older, more medically complex, and more likely to have extensive disease involving the ovaries, bowel, or multiple organs.
The trend toward outpatient surgery shows progress in minimally invasive gynecologic care, but the study also confirms that inpatient surgery remains important for patients with more complex disease or higher health risks. In other words, endometriosis surgery is becoming more efficient and more outpatient-based, but the right surgical setting still depends on careful patient selection.
Reference
Zhang E, Huang Y, Seaman SJ, Wright JD, Friedman AM. Trends and Characteristics of Inpatient versus Ambulatory Surgery for Endometriosis. American Journal of Obstetrics and Gynecology. 2026-05-13. PMID: 42134736.