Life After Ileocecal Valve Removal: How Bowel Function, Quality of Life, and Vitamin B12 Levels Are Affected

Table of Contents

• Key Points
• Background: Why This Question Matters
• How the Study Was Designed
• Who Took Part in the Study
• Quality of Life Results: The General Digestive Questionnaire
• Quality of Life Results: The Cancer-Specific Questionnaire
• Which Patients Had More Lasting Symptoms?
• Vitamin B12 Levels After Surgery
• What These Findings Mean for Patients
• Limitations of the Study
• Practical Recommendations for Patients
• Frequently Asked Questions
• Source Information

Key Points

• In a study of 158 patients, abdominal pain, bloating, nausea, constipation, and bowel frequency improved significantly over six months after ileocecal valve removal.
• Diarrhea temporarily worsened at two weeks after surgery before improving by six weeks; gas and stool leakage stayed about the same.
• No patient developed clinically significant vitamin B12 deficiency, even with 20 cm or more of ileum removed, but those patients showed a downward trend.
• Women, older patients, those who had open surgery, those with advanced cancer, and those with longer bowel segments removed reported more lasting symptoms.
• The study was observational, had short follow-up, and mostly included cancer patients, so findings apply most confidently to that group.

Background: Why This Question Matters

The ileocecal valve (ICV), also called the ileocecal junction, is a muscular sphincter valve — a ring of muscle that opens and closes like a gate. It separates the small bowel (ileum) from the large bowel (colon). It controls how digested food passes through, under the influence of hormones and nerve fibers.

When surgeons remove this valve during right colectomy or ileocecal resection, bacteria that normally live in the colon can move backward into the ileum. Under certain circumstances, this backward movement can lead to a condition called small intestinal bacterial overgrowth, or SIBO (too many bacteria growing in the upper part of the gut).

SIBO is not rare. The reported prevalence in the general population ranges from 0% to 20%. After removal of the ileocecal valve, that number rises to as much as 32%.

SIBO symptoms are usually vague and non-specific. Patients may notice abdominal discomfort, bloating, and diarrhea. In more serious cases, SIBO can cause malabsorption (poor absorption of nutrients), malnutrition, and vitamin B12 deficiency.

Vitamin B12 deserves special attention here. This vitamin is actively absorbed only in the terminal ileum (the last section of the small bowel). However, a small amount is passively absorbed throughout the entire small bowel. Because of that backup mechanism, ileal resections (surgical removals of ileum) shorter than 20 cm generally do not put patients at risk of vitamin B12 deficiency.

Right colectomy and ileocecal resection are very common operations. They are performed for both cancerous and non-cancerous diseases, and both as planned (elective) surgery and as emergency surgery. Patients frequently ask what their bowel function will be like afterward.

A small number of patients do report a clinically relevant worsening of bowel habits, vitamin deficiency, and a drop in quality of life over the long term. The authors note that in their experience this can even become a source of medical-legal complaints. Understanding what actually happens — and how often — is therefore important for both patients and surgeons.

This study had two goals. The primary aim was to evaluate intestinal activity and quality of life in patients who had an uncomplicated recovery after right colectomy or ileocecal resection, whatever the reason for the operation. The secondary aim was to assess vitamin B12 deficiency after surgery and whether patients needed vitamin supplements.

How the Study Was Designed

This was a prospective, longitudinal, observational, multicentric study. In plain terms: patients were enrolled and then followed forward in time, across multiple hospitals, without the researchers assigning any particular treatment. The study ran from November 2016 to May 2018 at six Italian centers and one Slovenian colorectal surgery center.

Patients were eligible if they were 16 years or older and underwent a right colectomy, an extended right colectomy, or an ileocecal resection. The reason for surgery could be malignant (cancerous) or benign (inflammatory or ischemic, meaning caused by reduced blood flow). Both elective and emergency operations were included.

Surgery was performed by open approach (a traditional incision), laparoscopic approach (keyhole surgery, with the reconnection performed either inside or outside the body), or robotic approach.

Researchers excluded certain patients to keep the results interpretable:

• Patients who had palliative surgery (surgery intended to relieve symptoms, not cure disease)
• Patients with a diverting stoma (an opening on the abdomen that reroutes stool)
• Patients with postoperative complications graded 3b or higher on the Clavien-Dindo classification (a standard scale for surgical complications, where higher grades mean more serious problems requiring further intervention)

The study was approved by all centers under Protocol Number 5903 by the Local Ethical Committee of Trieste University Hospital. Every participant gave written informed consent.

For each patient, the researchers recorded age, gender, whether the disease was benign or malignant, the type of operation, the length of the removed surgical specimen (total length, length of ileum, length of colon), cancer stage according to the AJCC classification (the standard system for staging cancer), and whether the patient received adjuvant therapy (additional treatment after surgery, such as chemotherapy).

How Bowel Function and Quality of Life Were Measured

The team used two validated questionnaires. "Validated" means the questionnaires have been formally tested and shown to reliably measure what they claim to measure.

The first was the Gastrointestinal Quality of Life (GIQLI) questionnaire. It was given to every patient, including those with inflammatory, ischemic, or neoplastic (tumor-related) disease. The GIQLI was completed at the time of surgery, 2 weeks after surgery, and 6 weeks after surgery. Researchers focused on specific items: abdominal pain, bloating, bowel frequency, bowel urgency, bowel movement, diarrhea, constipation, and nausea — question numbers 1, 3, 7, 30, 31, 32, 33, and 36.

The GIQLI uses a five-point scale to show how much symptoms affected quality of life: "0 = never," "1 = rarely," "2 = sometimes," "3 = most of the time," and "4 = all the time." A lower score therefore means fewer symptoms.

The second questionnaire was the European Organization for Research and Treatment of Cancer (EORTC) QLQ-CR29 module. It was given only to patients with cancer. It was completed at the time of surgery, 3 months after surgery, and 6 months after surgery. The selected items covered abdominal pain, bloating, gas and/or fecal incontinence (loss of control over gas or stool), frequency of bowel movements during the day, and frequency of bowel movements during the night — question numbers 35, 37, 49, 50, 52, and 53.

The QLQ-CR29 uses a four-point scale: "1 = never," "2 = occasionally," "3 = most of the time," and "4 = all the time." Again, lower is better.

The researchers defined chronic sequelae (lasting after-effects) as persistent symptoms producing a GIQLI score of 3 or higher at 6 weeks after surgery, and/or a QLQ-CR29 score of 3 or higher at 6 months after surgery.

Vitamin B12 Testing and Statistical Methods

Blood samples for vitamin B12 were collected at the time of surgery, 3 months after surgery, and 6 months after surgery. Serum vitamin B12 levels between 148 pg/mL and 980 pg/mL were considered within the normal range. The researchers also examined whether vitamin B12 levels correlated with the length of small bowel removed.

Data were collected prospectively in an anonymous database using Microsoft Excel 2007. Baseline characteristics were reported as mean ± standard deviation (SD) or as median with interquartile range — the median is the middle value, and the interquartile range describes the spread of the middle half of the data. Categorical variables were reported as frequency and percentage.

The researchers used the Friedman test, a non-parametric test for paired data, to analyze variation in scores between baseline and follow-up. Non-parametric means the test does not assume the data follow a normal bell-shaped distribution. For post-hoc tests (follow-up comparisons performed after the main test), they used the Wilcoxon signed rank test, corrected with the Holm method to reduce the chance of false-positive findings.

To judge whether changes were clinically meaningful — not just statistically significant — the team used the minimal important difference (MID) concept and an approach called the empirical rule effect-size (ERES) calibration method. The ERES method defines a change of 8% in the theoretical range of a questionnaire as a clinically significant change in health-related quality of life (HRQL).

In practical numbers: an 8% change on the GIQLI's 0-to-4 range equals 0.32 points per item. An 8% change on the QLQ-CR29's 1-to-4 range equals 0.24 points per item.

Finally, the team applied a linear mixed-effects (LME) model for longitudinal data. This statistical method identifies which patient-related, intraoperative (during surgery), and postoperative factors most strongly affect the total score over time.

All p values came from two-sided tests, with 0.05 used as the significance level. Analyses were performed with R 3.5.0 software and STATA 14.2.

Who Took Part in the Study

The study analyzed 158 patients who underwent right colectomy, right extended colectomy, or ileocecal resection between November 2016 and May 2018.

Of these patients, 87 (55.0%) were male and 71 (45.0%) were female. The median age was 71 years, with a range from 16 to 91 years.

Cancer was the main reason for surgery, reported in 149 patients (93.3%). Of these, 148 had colonic adenocarcinoma (a type of cancer starting in the glandular cells of the colon) and 1 had a maltoma (a rare type of lymphoma, or cancer of the immune system cells). The remaining 9 patients (6.7%) had inflammatory or ischemic disease.

Cancer stages were distributed as follows:

• Stage 0: 21 patients (14.2%)
• Stage I: 29 patients (19.6%)
• Stage II: 52 patients (35.1%)
• Stage III: 40 patients (27.0%)
• Stage IV: 4 patients (2.7%)
• Stage not recorded: 2 patients (1.4%)

Overall, 46 patients (30.8%) received postoperative adjuvant chemotherapy.

Right colectomy was by far the most common operation, performed in 135 patients (85.4%). Within this group, 127 patients (94.1%) had malignant disease and 8 patients (5.9%) had benign disease. Extended right colectomy was performed in 20 patients (12.7%), all of whom had malignant disease. Ileocecal resection was performed in just 3 patients (1.9%) — 2 with malignant disease and 1 with benign disease.

Laparoscopy was the preferred surgical approach, used in 117 cases (74.1%). Open surgery was used in 40 patients (25.3%), and robotic surgery in 1 patient (0.6%).

The median length of the removed surgical specimen was 31 cm, ranging widely from 16 cm to 152 cm. When broken down by segment, the median length of removed ileum was 8 cm (range 2–140 cm) and the median length of removed colon was 20 cm (range 4–55 cm).

Quality of Life Results: The General Digestive Questionnaire

Overall, 119 patients (75.3%) completed the GIQLI questionnaire before surgery, 118 patients (74.7%) completed it 2 weeks after surgery, and 111 patients (70.3%) completed it 6 weeks after surgery. This represents a drop-out rate of 29.7%. The statistical analysis included only patients who completed the full follow-up.

The researchers found a significant difference in symptoms between baseline and follow-up for every item examined — except for uncontrolled stools.

Over the 6-week follow-up period, there was a clinically relevant improvement in all examined items except diarrhea. In other words, most bowel symptoms got better, not worse.

Scores: "0 = never," "1 = rarely," "2 = sometimes," "3 = most of the time," "4 = all the time." Lower scores mean fewer symptoms. An asterisk (*) marks changes the authors judged clinically significant using the ERES method.

Two patterns stand out. Constipation improved significantly just 2 weeks after surgery and stayed improved at 6 weeks. Diarrhea temporarily worsened at 2 weeks before improving again by 6 weeks. Abdominal pain, bloating, and nausea all improved significantly over the 6-week follow-up (p < 0.001 for each).

The total GIQLI score dropped from 12.50 before surgery to 9.47 at 6 weeks — a change of more than 3 points, which reflects a meaningful improvement in overall digestive well-being.

Persistent Symptoms at 6 Weeks

The researchers then looked at how many patients still had significant symptoms at 6 weeks, defined as a GIQLI score of 3 or higher ("most of the time" or "all the time"). The numbers were low:

• Diarrhea: 8 patients (7.2%)
• Frequent bowel movements: 7 patients (6.3%)
• Urgent bowel movements: 6 patients (5.4%)
• Constipation: 4 patients (3.6%)
• Abdominal pain: 3 patients (2.7%)
• Bloating: 2 patients (1.8%)
• Nausea: 1 patient (0.9%)
• Uncontrolled stools: 1 patient (0.9%)

Expressed in "X in Y" terms, roughly 1 in 14 patients still reported frequent diarrhea at 6 weeks, about 1 in 16 reported frequent bowel movements, and about 1 in 18 reported urgency. Constipation affected about 1 in 28 patients, and pain and bloating each affected fewer than 1 in 35.

Quality of Life Results: The Cancer-Specific Questionnaire

The EORTC QLQ-CR29 questionnaire was completed by 148 patients (93.7%) before surgery, 135 patients (85.4%) at 3 months, and 102 patients (64.5%) at 6 months. The drop-out rate was 35.4%. Again, only patients who completed the full follow-up were analyzed.

A significant improvement in symptoms between baseline and follow-up was recorded for every item except gas and fecal incontinence.

Scores: "1 = never," "2 = occasionally," "3 = most of the time," "4 = all the time." Lower scores mean fewer symptoms. An asterisk (*) marks clinically significant changes by the ERES method.

The total score improved significantly across the 6-month follow-up period (p < 0.001), falling from 9.73 before surgery to 8.28 at 6 months.

Persistent Symptoms at 6 Months

Using the same "3 or higher" threshold at 6 months after surgery, the rates of lasting symptoms were:

• Unintentional gas release (flatulence): 13 patients (12.7%) — about 1 in 8
• Bloating: 9 patients (8.8%) — about 1 in 11
• Frequent bowel movements during the day: 8 patients (7.8%) — about 1 in 13
• Abdominal pain: 5 patients (4.9%) — about 1 in 20
• Stool leakage: 4 patients (3.9%) — about 1 in 26
• Frequent bowel movements during the night: 3 patients (2.9%) — about 1 in 34

Notably, gas and stool leakage were the two items that did not improve over time — they stayed roughly the same from before surgery through 6 months afterward.

Which Patients Had More Lasting Symptoms?

The linear mixed-effects model identified several factors linked to worse symptom scores. This type of analysis accounts for repeated measurements over time and adjusts for other variables.

When using the GIQLI questionnaire, the following associations were found 6 weeks after surgery:

• Female gender was linked to more frequent abdominal pain, bloating, frequent bowel movements, diarrhea, and nausea.
• Advanced age and open surgery were linked to constipation.
• Advanced AJCC cancer stage at the time of surgery was related to postoperative abdominal pain, bloating, frequent bowel movements, and urgent bowel movements.
• Longer surgical specimen (the total piece removed) correlated with bloating, frequent bowel movements, and urgent bowel movements.

Looking specifically at the GIQLI total score at 6 weeks, worsening quality of life was significantly correlated with female gender (p = 0.03) and with the length of ileum removed (p = 0.04). These associations were statistically significant, meaning they are unlikely to be explained by chance alone.

When using the EORTC QLQ-CR29 questionnaire, the following associations were found 6 months after surgery:

• Female gender affected the frequency of bowel movements.
• Advanced age was linked to stool leakage.
• Open surgical approach correlated with postoperative abdominal pain, gas incontinence, and stool leakage.
• Advanced AJCC cancer stage was related to abdominal pain, bloating, and frequent bowel movements during the day.
• Longer specimen length correlated with gas incontinence, stool leakage, and frequent bowel movements during the day.

Put simply: patients who were female, older, had open rather than keyhole surgery, had more advanced cancer, or had a longer segment of bowel removed tended to report more lingering symptoms. The authors emphasize that these are associations, not proof of cause and effect.

Vitamin B12 Levels After Surgery

Blood samples for vitamin B12 were collected before surgery, at 3 months, and at 6 months. Complete 6-month data were available for 92 patients (58.2%), and only these patients were included in the statistical analysis.

The baseline median vitamin B12 level was 307.0 pg/mL (range 81.9–2295.2 pg/mL). At 3 months the median was 287.0 pg/mL (range 76.0–1394.0 pg/mL), and at 6 months it was 294.0 pg/mL (range 73.8–892.3 pg/mL).

The overall longitudinal analysis showed a small but statistically significant decrease over time (p < 0.001). Importantly, these median values all stayed within the normal reference range of 148 pg/mL to 980 pg/mL, and no significant deficiency was observed regardless of the length of the surgical specimen.

The team then split patients by how much ileum was removed. Two very different patterns emerged:

1. Patients with 20 cm or more of ileum removed showed a significant decrease in vitamin B12 levels that was already visible at 3 months:
   • Before surgery: median 376.0 pg/mL (range 185.0–631.0 pg/mL)
   • 3 months after: median 372.0 pg/mL (range 207.0–596.0 pg/mL)
   • 6 months after: median 325.0 pg/mL (range 131.0–564.0 pg/mL)
   • p < 0.001
2. Patients with less than 20 cm of ileum removed actually showed a small but statistically significant increase in vitamin B12 levels at 6 months compared with before surgery:
   • Before surgery: median 240.0 pg/mL (range 81.9–2295.2 pg/mL)
   • 3 months after: median 255.5 pg/mL (range 76.0–1394.0 pg/mL)
   • 6 months after: median 265.0 pg/mL (range 73.8–892.3 pg/mL)
   • p = 0.02

This finding fits with what is known about vitamin B12 absorption. The vitamin is actively absorbed in the terminal ileum, but a small amount is passively absorbed throughout the entire small bowel. When less than 20 cm of ileum is removed, that passive absorption appears to compensate.

In this series, no patient required vitamin B12 supplementation as a result of the surgery.

What These Findings Mean for Patients

After removal of the ileocecal valve, patients can experience changes in bowel habits. These changes vary widely from person to person. Researchers believe they may be related to small bowel bacterial overgrowth (SIBO).

In most cases, bowel function after ileocecal valve removal is reported as satisfactory. That is what this study found too. The overall picture was reassuring: quality of life improved, and vitamin B12 levels did not fall into a deficient range.

However, the authors are clear that a significant postoperative dysfunction can sometimes occur. When it does, it can affect general well-being and health-related quality of life. In rare cases, the authors note, it can even become a potential cause for medical-legal issues — which is one reason they emphasize the importance of informing patients in advance.

The authors also reference guidance from the Italian Society of Legal Medicine and Insurance Policy (SIMLA), underscoring that the duty to warn patients about possible bowel habit changes is not just good practice but a recognized professional obligation.

Several specific takeaways stand out for patients:

• Most symptoms improve, not worsen. Abdominal pain, bloating, nausea, constipation, and both daytime and nighttime bowel frequency all improved significantly after surgery.
• Diarrhea may briefly get worse. Diarrhea scores worsened at 2 weeks after surgery before improving by 6 weeks. Patients should expect a temporary phase, not assume the problem is permanent.
• Gas and stool leakage may not improve. These were the two items that stayed stable rather than improving.
• Vitamin B12 deficiency was not a problem in this group — even among patients who had 20 cm or more of ileum removed. However, those patients did show a measurable downward trend, so monitoring may still be reasonable.
• Some patients are more likely to have lingering symptoms: women, older patients, those who had open surgery, those with more advanced cancer stage, and those with longer bowel segments removed.

It is important to note what the study does not show. It does not prove that any of these factors cause worse symptoms. It also cannot say whether symptoms would have been better or worse without surgery, because there was no comparison group of patients who did not have the operation.

Limitations of the Study

The authors are transparent about the study's constraints. Understanding these helps patients interpret the results correctly.

First, the follow-up periods were relatively short — 6 weeks for the GIQLI and 6 months for the EORTC QLQ-CR29. Longer-term outcomes beyond 6 months are not captured here.

Second, drop-out rates were substantial. The GIQLI had a 29.7% drop-out rate, and the QLQ-CR29 had a 35.4% drop-out rate. Vitamin B12 data at 6 months were available for only 92 patients (58.2%). Patients who dropped out may have had different outcomes than those who stayed in the study, which could bias results in either direction.

Third, the patient population was heavily weighted toward cancer surgery. In total, 149 of 158 patients (93.3%) had malignant disease. Only 9 patients (6.7%) had benign disease, and only 3 patients (1.9%) underwent ileocecal resection specifically. This means the findings apply most confidently to patients having surgery for colon cancer, and less so to other groups.

Fourth, very few patients had laparoscopic surgery converted to robotic surgery (just 1 patient, 0.6%), so no conclusions can be drawn about robotic approaches.

Fifth, the study was observational — patients were not randomly assigned to different operations. Therefore, comparisons between surgical approaches (open vs. laparoscopic) may be influenced by why the surgeon chose that approach in the first place.

Finally, the statistical analysis relied on patients who completed follow-up, which reduces the sample size and the strength of the conclusions.

Practical Recommendations for Patients

Based on this study and the authors' conclusions, here is what patients can reasonably expect and do:

1. Expect a recovery curve, not an immediate result. Bowel symptoms generally improve over weeks to months. Give your body time.
2. Do not be alarmed by early diarrhea. Diarrhea commonly worsens in the first 2 weeks after surgery and then improves. Stay hydrated and discuss persistent diarrhea with your surgeon.
3. Ask about vitamin B12 monitoring if a longer segment of ileum was removed. In this study, patients who had 20 cm or more of ileum removed showed a downward trend in vitamin B12 levels, even though no one became deficient. A simple blood test at 3 and 6 months after surgery can track this.
4. Know your own risk profile. If you are female, older, had open surgery, have a more advanced cancer stage, or had a long segment of bowel removed, you may be more likely to notice lasting symptoms. This does not mean symptoms are inevitable — only that they are more likely.
5. Discuss bowel habit changes openly with your care team. The authors stress that warning patients about potential bowel habit changes is mandatory. If you were not told what to expect, ask.
6. Seek help for persistent symptoms. If gas incontinence, stool leakage, or frequent bowel movements last more than a few months, ask about evaluation for small intestinal bacterial overgrowth (SIBO), which affects up to 32% of patients after ileocecal valve removal.
7. Keep perspective. In this study of 158 patients, health-related quality of life improved overall, and no vitamin B12 deficiency developed. Most patients did well.

Frequently Asked Questions

What is the ileocecal valve, and why does removing it matter?

The ileocecal valve is a muscular ring that separates the small bowel from the large bowel and controls how digested food passes through. When surgeons remove it during right colectomy or ileocecal resection, bacteria from the colon can move backward into the ileum. This backward movement can lead to a condition called small intestinal bacterial overgrowth, or SIBO.

Will my bowel habits get worse after this surgery?

In a study of 158 patients, most bowel symptoms improved over six months. Abdominal pain, bloating, nausea, constipation, and frequent bowel movements all got better. Diarrhea briefly worsened at two weeks before improving by six weeks. Gas and stool leakage stayed about the same. A small number of patients reported lasting symptoms, so some change is possible.

Which patients are more likely to have lasting bowel symptoms?

The study found that women, older patients, those who had open surgery rather than keyhole surgery, those with more advanced cancer stage, and those with a longer segment of bowel removed reported more persistent symptoms. These are associations, not proof of cause and effect. Knowing your risk profile can help you discuss symptoms openly with your care team.

How long does recovery take, and what should I expect?

Expect a recovery curve, not an immediate result. Bowel symptoms generally improve over weeks to months. Diarrhea commonly worsens in the first two weeks after surgery and then improves. Give your body time, stay hydrated, and discuss persistent diarrhea with your surgeon. If gas incontinence, stool leakage, or frequent bowel movements last more than a few months, ask about evaluation for SIBO.

What is SIBO, and how common is it after ileocecal valve removal?

SIBO stands for small intestinal bacterial overgrowth, meaning too many bacteria grow in the upper part of the gut. Symptoms are usually vague and may include abdominal discomfort, bloating, and diarrhea. In the general population, reported prevalence ranges from 0% to 20%. After removal of the ileocecal valve, that number rises to as much as 32%.

If I'm scheduled for a right colectomy that removes my ileocecal valve, when should I get a second opinion?

A second opinion is reasonable before surgery if you want confirmation that removing the ileocecal valve is necessary and whether alternatives exist. Bowel symptoms such as pain, bloating, nausea, constipation and bowel frequency generally improve after surgery, though diarrhea briefly worsens, and gas and stool leakage may persist. Women, older patients, those having open surgery, more advanced cancer stages, and longer bowel segments removed report more lasting symptoms. A second opinion can review your pathology, imaging and planned operation. Diagnostic Detectives Network provides independent expert second opinions.

Source Information

Original article title: Ileocecal valve syndrome and vitamin b12 deficiency after surgery

Authors: Paola Germani, Annalisa Zucca, Fabiola Giudici, Susanna Terranova, Marina Troian, Natasa Samardzic, Marco Greco, Jurij Janez, Camilla Gasparini, Emanuela Cagnazzo, Andrea Vignali, Fabio Giannone Codiglione, Andrea Armellini, Uberto Romario Fumagalli, Riccardo Rosati, Giuseppe Piccinni, Jacques Megevand, Ales Tomazic, Francesco Corcione, Silvia Palmisano, and Nicolò de Manzini

Participating institutions: University Hospital of Trieste (Trieste, Italy); Monaldi Hospital, Azienda Ospedaliera Dei Colli (Naples, Italy); Ljubljana University Medical Center (Ljubljana, Slovenia); San Pio X Humanitas Research Hospital (Milan, Italy); Santa Maria Hospital GVM Care and Research (Bari, Italy); San Raffaele Hospital, Vita-Salute San Raffaele University (Milan, Italy); and Ospedali Civili (Brescia, Italy)

Publication details: Updates in Surgery, 2021, Volume 73, pages 569–580. Published online 9 July 2020. DOI: 10.1007/s13304-020-00845-z. Received 9 May 2020; accepted 1 July 2020.

Ethics approval: Protocol Number 5903, Local Ethical Committee of Trieste University Hospital. Written informed consent was obtained from all participants.

Key terms used in this article: ileocecal valve (the muscular valve between the small and large bowel); SIBO or small intestinal bacterial overgrowth (too many bacteria in the upper gut); GIQLI (Gastrointestinal Quality of Life questionnaire); EORTC QLQ-CR29 (European Organization for Research and Treatment of Cancer colorectal cancer quality-of-life questionnaire); HRQL (health-related quality of life); LME model (linear mixed-effects model); ERES (empirical rule effect-size); AJCC (American Joint Committee on Cancer staging system); Clavien-Dindo classification (a standard scale for surgical complications).

This patient-friendly article is based on peer-reviewed research.