Bloating, Visible Abdominal Distension, and Other Intestinal Gas‐Related Symptoms in Irritable Bowel Syndrome and Functional Dyspepsia

ABSTRACT

Background

Bloating refers to the sensation of tension in the abdomen, reported in the presence or absence of visible abdominal distension. These and other gas‐related symptoms are often reported by patients with irritable bowel syndrome (IBS) and functional dyspepsia (FD). However, the prevalence of bloating and visible abdominal distension as separate symptoms in these disorders is not well known. The aim of this study was to investigate the link between bloating, distension, and intestinal gas‐related symptoms with IBS and FD, and their overall impact.

Methods

Data from a population‐based internet survey of adults from the US, UK, and Mexico were used. This survey included Rome IV diagnostic questions for IBS and FD, questions to distinguish between ≥ weekly bloating and/or distension, and the Intestinal Gas Questionnaire (IGQ) to assess the impact of six gas‐related symptoms.

Results

The analyses included 131 individuals with only IBS, 360 with only FD, 217 with IBS + FD and 4740 without IBS and FD (reference group). Individuals with IBS (64.9%), FD (50.6%), and especially IBS + FD (88.5%) reported bloating and/or distension more frequently than the reference group (13.7%). Bloating and distension as distinct and combined symptoms were strongly linked to IBS and FD even after correcting for confounding factors. Also, other gas‐related symptoms had a higher impact on individuals with IBS and/or FD compared with the reference group.

Discussion

Bloating and visible abdominal distension can occur as concomitant or distinct impactful symptoms and are, together with other gas‐related symptoms, strongly linked to IBS and FD. These findings may provide arguments to include bloating and distension as supportive criteria for IBS and FD diagnoses.

Key Summary

• Summarise the established knowledge on this subject

  • ◦Bloating with or without visible abdominal distension is often reported by patients with irritable bowel syndrome (IBS) and functional dyspepsia (FD).
  • ◦Bloating and visible abdominal distension may have partially different underlying pathophysiological mechanisms.

• What are the significant and/or new findings of this study?

  • ◦In addition to bloating with or without distension, visible abdominal distension alone is also frequently reported in a smaller but relevant proportion of individuals with IBS and FD.
  • ◦Intestinal gas‐related symptoms, apart from bloating and visible abdominal distension, have a high impact on individuals with IBS and FD.

1. Introduction

Abdominal bloating refers to the subjective sensation of tension, abdominal fullness, pressure, or a sensation of trapped gas, and can be present with or without measurable or objective increase in abdominal girth, i.e. visible abdominal distension [1]. The sensation of abdominal bloating and visible abdominal distension are very common across disorders of gut‐brain interaction (DGBI), and in irritable bowel syndrome (IBS) and functional dyspepsia (FD) in particular [2, 3, 4]. However, these symptoms are not part of the formal diagnostic criteria for both DGBI, apart from epigastric bloating being a supportive symptom for FD [5, 6]. Importantly, 60% of patients with IBS report bloating‐type symptoms as their most bothersome symptoms, which are associated with a reduction in daily activities and well‐being, resulting in an impaired quality of life [7, 8, 9].

To date, few studies have distinguished the sensation (abdominal bloating) from the visible component (abdominal distension) of these symptoms [3, 4, 10]. Since the underlying mechanisms of bloating and visible abdominal distension are at least partly distinct, this likely requires different management approaches [1, 11, 12, 13]. In clinical practice, other intestinal gas‐related symptoms, such as flatulence and belching, are also often reported by individuals with IBS and FD. However, relevant data on the prevalence and impact of these symptoms as well as on the treatment approaches are currently sparse [14].

Given their high prevalence and substantial impact, a better understanding of bloating and visible abdominal distension, in particular as distinct or concomitant symptoms, and other intestinal gas‐related symptoms in individuals with IBS and FD seems important. Therefore, the aims of this study were to investigate (1) the prevalence of bloating and visible abdominal distension as distinct and concomitant symptoms in individuals with IBS and/or FD, (2) factors associated with bloating and visible abdominal distension, and (3) other gas‐related symptoms and their impact on daily life in individuals with IBS and FD.

2. Materials and Methods

2.1. Study Setting and Participants

In this study, data from a nationwide internet survey conducted in three countries—United States of America (US), United Kingdom (UK), and Mexico ‐ were used [15, 16]. Anonymized participant data were collected in 2020 by a market research company (Qualtrics LLC). The enrollment was quota‐controlled for sex and age. Participants were told that the survey was a health survey rather than a survey about intestinal gas‐related symptoms or GI diseases. The surveys included several built‐in quality‐assurance measures [15].

2.2. Variables and Definitions

For this study, we used demographic data, body mass index (BMI) based on self‐reported height and weight, individual items and symptom profiles based on the bowel and gastroduodenal modules of the adult Rome IV Diagnostic Questionnaire [17], the Intestinal Gas Questionnaire (IGQ, Supporting Information S1: Methods) [14, 18], the Patient Health Questionnaire‐12 (PHQ‐12) (non‐GI somatic symptoms as a surrogate marker for somatization, with menstruation symptoms excluded) [19, 20], and the Patient Health Questionnaire‐4 (PHQ‐4) (psychological distress) [21]. An extra question was included to assess if participants typically had only bloating, only visible abdominal distension or both.

2.3. Definition of IBS, FD, and the Reference Group

Individuals were classified as IBS or FD if they fulfilled the corresponding diagnostic criteria according to the Rome IV Diagnostic Questionnaire and did not self‐report a history of being diagnosed by a physician with celiac disease, inflammatory bowel disease, GI cancer, diverticulitis (only for IBS), a peptic ulcer (only for FD), or having had a bowel resection (only for IBS) [22]. Individuals with IBS were, based on the same questionnaire, further subtyped into IBS with predominant constipation (IBS‐C), predominant diarrhea (IBS‐D), or mixed bowel habits (IBS‐M). Since the group with IBS unclassified (IBS‐U) was small (n = 22), they were not included in IBS subtype analyses. Individuals with FD were subtyped into postprandial distress syndrome (PDS), epigastric pain syndrome (EPS), or fulfilling the criteria of both subtypes (PDS + EPS).

The reference group consisted of individuals who did not fulfill the criteria for IBS and FD, and who did not report a history of any of the previously mentioned organic diseases or a bowel resection.

2.4. Definition of Bloating and Visible Abdominal Distension

Having bloating and/or visible abdominal distension was defined as having at least weekly bloating and/or visible abdominal distension during the last 3 months based on the Rome IV Diagnostic Questionnaire [17]. The cutoff of reporting weekly symptoms was used to estimate clinically relevant symptoms of bloating and visible abdominal distension [3, 5]. As the next step, these individuals were subdivided into groups of those who reported typically only having a sensation of tension or pressure in the abdomen with an abdomen that never or rarely looked unusually large (bloating alone), those who reported typically only having an abdomen that looked unusually large and never or rarely having a sensation of tension or pressure in the abdomen (distension alone), and those who reported experiencing both at the same time (bloating and distension). For some analyses, all frequencies of bloating and/or visible abdominal distension were included, ranging from none to all the time during the last 3 months. When all frequencies were included in the analysis, this was explicitly stated.

2.5. Statistical Methods

Numbers, proportions, and medians, including the corresponding 95% confidence intervals (CI) and interquartile ranges (IQR), were used for the descriptive analyses.

Logistic regression analyses were used to assess associations between the independent variable bloating and/or abdominal distension (with no bloating and abdominal distension as reference), and the dependent variable of fulfilling the criteria for only IBS, only FD, or IBS + FD versus the reference group used in three different logistic regression models.

Analyses were performed without (crude odds ratio (OR)) and with (adjusted OR) adjustment for potential confounding factors, chosen based on clinical knowledge and previous literature [3, 23]. These included age, sex, BMI, country, psychological distress (PHQ‐4), and non‐GI somatic symptoms (PHQ‐12). Similar analyses were performed stratified by IBS and FD subtypes, also including those individuals with overlapping IBS and FD. Multicollinearity was assessed with the adjusted generalized standard error inflation factor, and was low (< 1.6) in all models.

To investigate the association between IBS and/or FD and overall gas‐related symptom burden (IGQ global score), multivariable linear regression models were performed with separate models for only IBS, only FD, and IBS + FD. Potential confounding variables were added based on clinical knowledge and previous literature and were the same as those used for the logistic regression models. Multicollinearity was assessed with the variance inflation factor and was low in all models (< 2.5). Normality of residuals was confirmed based on predicted probability plots. There was heteroscedasticity based on scatterplots of residuals, which was judged as acceptable with alternative models such as logistic or ordinal regression models considered inferior.

The Spearman's rank correlation coefficient was used to assess associations between the frequency of only bloating, only distension or both, and other factors.

Effect sizes (ORs and β‐coefficients, including 95% CI, and Spearman's rho's) are shown without p‐values due to the explorative character of this study [24]. The adjusted generalized standard error inflation factors were calculated using R version 4.4.3 and RStudio version 2025.05.1. All other statistical analyses were performed using IBM SPSS (version 29.0.0.0).

2.6. Ethics Considerations

The study was reviewed by the Institutional Review Board (IRB) at the University of North Carolina at Chapel Hill (US) and was determined to be exempt from IRB oversight due to the anonymity of the online survey method. All participants gave consent prior to completing the survey.

3. Results

The survey was completed by 5978 respondents with a median age of 45 years [IQR 34–61] of whom 49.9% were female. The prevalence of IBS was 5.8% (n = 348) and of FD 9.7% (n = 577). Country‐specific data are shown in Supporting Information S1: Table 1. Of those fulfilling the criteria of IBS and/or FD, 18.5% (n = 131) met only the criteria for IBS, 50.9% (n = 360) only for FD and 30.6% (n = 217) for both. After the exclusion of 530 individuals due to self‐reported organic conditions, 4740 participants were included in the reference group. The characteristics of each group are shown in Table 1.

TABLE 1.

Characteristics of the study population.

	Reference n = 4740	Only IBS n = 131	Only FD n = 360	FD + IBS n = 217
Age (years), median [IQR]	46 [34–61]	38 [31–54]	39 [32–55]	38 [31–50]
Female, n (%)	2315 (48.8%)	83 (63.4%)	174 (48.3%)	133 (61.3%)
BMI (kg/m2), median [IQR]	26.1 [23.1–30.0]	27.3 [24.6–32.9]	26.0 [22.5–30.4]	26.1 [22.4–30.4]
Country, n (%)
US	1566 (33.0%)	36 (27.5%)	143 (39.7%)	73 (33.6%)
UK	1631 (34.4%)	52 (39.7%)	120 (33.3%)	61 (28.1%)
Mexico	1543 (32.6%)	43 (32.8%)	97 (26.9%)	83 (38.2%)
IBS subtype, n (%)
IBS‐C	—	48 (36.6%)	—	102 (47.0%)
IBS‐D	—	38 (29.0%)	—	50 (23.0%)
IBS‐M	—	35 (26.7%)	—	53 (24.4%)
IBS‐U	—	10 (7.6%)	—	12 (5.5%)
FD subtype, n (%)
PDS	—	—	233 (64.7%)	67 (30.9%)
EPS	—	—	81 (22.5%)	54 (24.9%)
EPS and PDS	—	—	46 (12.8%)	96 (44.2%)
Psychological distress (PHQ‐4), median [IQR]	1 [0–4]	4 [1–8]	4 [1–7]	5 [3–9]
Non‐GI somatic symptoms (PHQ‐12), median [IQR]	3 [1–5]	7 [5–9]	6 [4–9]	9 [6–12]

Abbreviations: BMI, body mass index; EPS, epigastric pain syndrome; FD, functional dyspepsia; IBS; irritable bowel syndrome; IBS‐C, irritable bowel syndrome with predominant constipation; IBS‐D, irritable bowel syndrome with predominant diarrhea; IBS‐M, irritable bowel syndrome with mixed bowel habits; IBS‐U, unspecified irritable bowel syndrome; IQR, interquartile range; n, number; PDS, postprandial distress syndrome; PHQ, patient health questionnaire; UK, United Kingdom; US, United States of America.

3.1. The Prevalence of Bloating and Visible Abdominal Distension in IBS and FD

The prevalence of bloating and/or distension was 64.9% (95% CI 56.4–72.5) in individuals with only IBS, 50.6% (45.4–55.7) in those with only FD, and 88.5% (83.5–92.1) in those with IBS + FD, compared to 13.7% (12.8–14.7) in the reference group (Figure 1A). The majority in all four groups reported concomitant bloating and distension, followed by bloating alone and visible abdominal distension alone (Figure 1B). Stratified by IBS and FD subtypes, bloating and abdominal distension were common across all IBS and FD subtypes, with no differences across IBS subtypes, but with higher proportions of individuals with bloating and/or visible abdominal distension in the PDS + EPS group compared to PDS or EPS alone (Figure 1C–F). In general, the same patterns of bloating and/or distension were observed when comparing the reference group and IBS and/or FD groups stratified by sex, age, BMI, country, and level of psychological distress (Supporting Information S1: Figure 1).

FIGURE 1.

The proportion of individuals with IBS and/or FD with bloating and/or visible abdominal distension. In figures A,C,E, and G, the proportion, including the 95% CI, of individuals reporting bloating and/or visible abdominal distension at least once a week are shown. In figures B,E,F, and H, bloating and/or visible abdominal distension are further divided into bloating alone, visible abdominal distension alone, or reported both together. In figures C and D, all individuals with IBS, including those with overlapping IBS + FD, are included. IBS‐U is not included as a subtype because of the low numbers of individuals with IBS‐U (n = 22). In figures E and F, all individuals with FD, including those with overlapping IBS + FD, are included. EPS, epigastric pain syndrome; FD, functional dyspepsia; IBS; irritable bowel syndrome; IBS‐C, irritable bowel syndrome with predominant constipation; IBS‐D, irritable bowel syndrome with predominant diarrhea; IBS‐M, irritable bowel syndrome with mixed bowel habits; IBS‐U, irritable bowel syndrome unspecified; n, number; PDS, postprandial distress syndrome.

A sensitivity analysis, including any bloating and/or distension, that is ranging from less than once a month to all the time during the last 3 months, showed the same patterns when comparing the (sub)groups (Supporting Information S1: Figure 2).

3.2. The Association of Bloating and Visible Abdominal Distension With IBS and FD

Logistic regression analyses were performed to determine the association between symptoms of bloating alone, distension alone, or having both together, and IBS and FD compared to the reference group. Having bloating and/or distension was strongly associated with having only IBS, only FD and especially concomitant IBS + FD, also after correcting for confounding factors (Figure 2). The strongest association was found between concomitant bloating and distension and concomitant IBS + FD (adjusted OR 29.0 (95% CI 17.7–47.6)).

FIGURE 2.

Associations between bloating and/or visible abdominal distension and IBS and/or FD. Logistic regression analyses were performed with dependent variables (A) only IBS versus reference group, (B) only FD versus reference group, and (C) IBS + FD versus reference group. The ORs of visible abdominal distension alone, bloating alone, and combined bloating and visible abdominal distension are relative to individuals without bloating and/or distension. The adjusted ORs are adjusted for age, sex, BMI, country, psychological distress, and somatization. BMI, body mass index; FD, functional dyspepsia; IBS; irritable bowel syndrome; OR, odds ratio.

All IBS and FD subtypes were strongly associated with bloating and/or distension, also after correction for confounding factors, except for distension and IBS‐M (Supporting Information S1: Figures 3 and 4). Furthermore, there was a tendency toward a stronger link between IBS‐C and distension (adjusted OR 9.9 (95% CI 5.0–19.4), compared to the other two IBS subtypes (IBS‐D: adjusted OR 4.6 (1.8–12.2), IBS‐M adjusted OR 2.7 (0.9–8.3)). In addition, individuals with PDS + EPS overlap had similar strong associations with bloating and/or distension as those observed for the IBS subtypes, whereas those with only EPS or PDS tended to have weaker associations.

3.3. Factors Associated With Bloating and Visible Abdominal Distension

To investigate factors associated with reporting bloating alone, distension alone, or both symptoms together, we analyzed the total group, including individuals with self‐reported organic conditions that were excluded from all other analyses. In particular, the frequency of key symptoms of IBS (abdominal pain, hard and loose stools) and FD (postprandial fulness, early satiety, and epigastric pain or burning) as well as higher levels of psychological distress and somatization were all associated with the frequency of bloating alone, distension alone, and the presence of both symptoms together (Figure 3).

FIGURE 3.

Associations between demographic factors, BMI, and the frequency of key symptoms of IBS and FD and the frequency of bloating and/or visible abdominal distension in the total population (n = 5978). Associations are shown as Spearman's rho with the frequency of bloating and/or visible abdominal distension ranging from never to all the time. BMI data of 421 individuals (7.0%) was missing based on unreliable self‐reported data. BMI, body mass index; GI, gastrointestinal.

3.4. Other Intestinal Gas‐Related Symptoms in IBS and FD and Their Impact on Daily Life

Individuals with IBS and FD reported a higher intestinal gas‐related symptom burden (mean IGQ IBS: 36.6 (95% CI 32.7–40.4), FD: 31.8 (29.4–34.1)) compared to the reference group (mean IGQ 14.4 (13.9–14.9)), with an even higher burden in individuals with IBS + FD (mean IGQ 47.1 (44.2–50.0); Figure 4A). To correct for the role of other factors, multivariable linear regression models were performed. After correcting for these potential confounding factors, the intestinal gas‐related symptom burden (IGQ global score) was still higher in individuals with only IBS (β‐coefficient 13.4 (95% CI 10.8–16.0)), only FD (β‐coefficient 9.9 (8.2–11.6)), and IBS + FD (β‐coefficient 17.8 (15.7, 20.0)) compared to the reference group.

FIGURE 4.

Intestinal gas‐related symptoms in IBS and FD. In figure A, the mean IGQ global scores (95% CI) are shown for the reference group and individuals with only IBS, only FD, and IBS + FD. In figure B, the mean IGQ global scores (95%) are shown for each IBS and FD subtype, also including individuals with IBS and FD overlap. EPS, epigastric pain syndrome; FD, functional dyspepsia; IBS; irritable bowel syndrome; IBS‐C, irritable bowel syndrome with predominant constipation; IBS‐D, irritable bowel syndrome with predominant diarrhea; IBS‐M, irritable bowel syndrome with mixed bowel habits; IGQ, intestinal gas‐related symptoms; PDS, postprandial distress syndrome.

No differences were observed between the IBS subtypes. However, differences were found between FD subtypes, with the highest intestinal gas‐related symptom burden reported by individuals with PDS + EPS (mean IGQ 49.3 (45.6–53.0), followed by EPS (mean IGQ 38.9 (35.3–42.4) and PDS (mean IGQ 31.4 (28.7–34.0)) (Figure 4B). The small difference between EPS and PDS diminished when performing a multivariable linear regression analysis correcting for country and comorbid IBS (Supporting Information S1: Table 2), while the difference between PDS or EPS alone versus PDS + EPS remained after correcting for country, comorbid IBS, age, sex, BMI, somatization, and psychological distress (PDS + EPS vs. EPS β‐coefficient 6.5 (95% CI 1.3, 11.8); PDS + EPS versus PDS β‐coefficient 6.8 (2.1, 11.5).

Details about overall intestinal gas‐related symptoms severity and impact on daily life as well as the six intestinal gas‐related domains are depicted in Table 2, showing the highest levels of symptoms and impact in individuals with overlapping IBS + FD.

TABLE 2.

Intestinal gas‐related symptoms in IBS and FD.

IGQ scores mean (95% CI)	Reference group n = 4740	Only IBS n = 131	Only FD n = 360	FD + IBS n = 217
Overall intestinal gas‐related symptoms severity	16.9 (16.4–17.5)	43.4 (39.8–47.0)	36.0 (33.6–38.4)	55.1 (52.6–57.6)
Overall intestinal gas‐related impact on daily life	12.6 (12.1–13.1)	34.9 (30.9–38.9)	31.8 (29.2–34.4)	49.0 (46.1–52.0)
Dimension score
Bloating	13.0 (12.4–13.5)	39.8 (35.7–44.0)	35.0 (32.2–37.8)	56.4 (53.7–59.1)
Flatulence	20.5 (19.9–21.2)	44.9 (40.5–49.2)	39.5 (36.6–42.4)	56.9 (53.2–60.5)
Belching	11.9 (11.4–12.4)	32.0 (27.2–36.8)	28.4 (25.6–31.2)	43.7 (39.8–47.6)
Bad breath	13.6 (13.0–14.2)	34.6 (29.5–40.0)	30.4 (27.4–33.4)	42.6 (38.5–46.8)
Stomach rumbling	14.1 (13.5–14.7)	39.3 (34.4–44.2)	31.8 (28.9–34.8)	50.3 (46.7–53.9)
Difficult gas evacuation	12.8 (12.3–13.3)	33.7 (29.3–38.0)	30.0 (27.1–32.9)	46.7 (43.3–50.0)

	All IBS n = 348	IBS‐C n = 150	IBS‐D n = 88	IBS‐M n = 88
Overall intestinal gas‐ related symptoms severity	50.7 (48.5–52.9)	52.3 (49.0–55.7)	48.6 (44.3–52.9)	51.9 (47.7–56.1)
Overall intestinal gas‐ related impact on daily life	43.7 (41.2–46.2)	47.3 (43.6–50.9)	37.7 (32.9–42.4)	45.5 (40.3–50.8)
Dimension score
Bloating	50.2 (47.7–52.6)	53.7 (50.1–57.3)	43.9 (39.2–48.7)	51.8 (46.8–56.8)
Flatulence	52.3 (49.5–55.6)	53.9 (49.5–58.2)	49.0 (43.3–54.7)	54.6 (48.7–60.6)
Belching	39.3 (36.2–42.4)	41.9 (37.2–46.6)	36.6 (30.6–42.6)	40.8 (34.3–47.2)
Bad breath	39.7 (36.4–42.9)	40.6 (35.5–45.6)	38.9 (32.2–45.6)	41.0 (34.7–47.4)
Stomach rumbling	46.2 (43.2–49.1)	48.4 (44.0–52.7)	45.4 (39.1–51.7)	46.1 (40.5–51.6)
Difficult gas evacuation	41.8 (39.1–44.5)	46.8 (42.6–51.0)	32.2 (27.7–36.8)	44.0 (38.5–49.5)

	All FD n = 577	PDS n = 300	EPS n = 135	PDS + EPS n = 142
Overall intestinal gas‐ related symptoms severity	43.2 (41.3–45.1)	35.9 (33.2–38.6)	44.9 (41.5–48.3)	56.9 (53.6–60.2)
Overall intestinal gas‐ related impact on daily life	38.3 (36.2–40.3)	32.1 (29.3–34.9)	38.5 (34.5–42.6)	51.1 (47.2–55.1)
Dimension score
Bloating	43.1 (40.9–45.2)	36.1 (33.1–39.1)	42.3 (38.4–46.3)	58.4 (54.8–62.0)
Flatulence	46.0 (43.6–48.4)	39.5 (36.3–42.8)	48.0 (43.3–52.7)	57.9 (53.4–62.3)
Belching	34.2 (31.8–36.5)	27.3 (24.2–30.4)	37.4 (32.8–42.0)	45.6 (40.7–50.6)
Bad breath	35.0 (32.5–37.5)	30.4 (26.9–33.8)	34.4 (29.8–39.0)	45.4 (40.5–50.4)
Stomach rumbling	38.8 (36.4–41.1)	32.2 (29.0–35.5)	40.4 (35.8–45.0)	51.0 (46.3–55.7)
Difficult gas evacuation	36.3 (34.0–38.6)	28.4 (25.4–31.5)	38.7 (34.2–43.2)	50.6 (46.4–54.8)

Abbreviations: EPS, epigastric pain syndrome; FD, functional dyspepsia; IBS; irritable bowel syndrome; IBS‐C, irritable bowel syndrome with predominant constipation; IBS‐D, irritable bowel syndrome with predominant diarrhea; IBS‐M, irritable bowel syndrome with mixed bowel habits; IGQ, intestinal gas questionnaire; PDS, postprandial distress syndrome.

4. Discussion

In this study, we showed that bloating and visible abdominal distension, as distinct and concomitant symptoms, are highly prevalent in individuals fulfilling the Rome IV criteria for IBS and FD in the general population. The strong associations between these symptoms and IBS and FD persisted after correction for multiple confounding factors. Furthermore, we identified clear associations between the frequency of bloating alone, distension alone, and concomitant bloating and distension, and the frequency of key symptoms of IBS and FD, the levels of psychological distress, and somatization. The burden of intestinal gas‐related symptoms, including bloating, flatulence, belching, bad breath, stomach rumbling, and difficult gas evacuation, was higher in individuals with IBS and/or FD compared with the reference group and was associated with a negative impact on daily life.

This study showed that the subjective sensation of bloating and visible abdominal distension can be considered as separate, although closely related, symptoms frequently reported by individuals with IBS and FD. In line with previous studies, we showed that bloating and visible abdominal distension are often reported together, but that there is a relevant subgroup of individuals who reported bloating without distension [4, 10, 25]. The current study is one of the first studies that investigated the presence of visible abdominal distension alone, that is, without bloating, in individuals fulfilling Rome IV IBS and FD criteria. We showed that the symptoms of visible abdominal distension alone were linked to both IBS and FD, although the subgroup reporting only visible abdominal distension was smaller compared to the subgroup that (also) reported bloating.

The underlying mechanisms of these bloating and visible abdominal distension may differ. One of the mechanisms proposed to be more clearly related to the sensation of bloating is visceral hypersensitivity, explaining why slight increases in gastrointestinal gas can cause symptoms [12, 26, 27]. In line with this, bloating was most strongly associated with overlapping IBS and FD, which is congruent with the notion that pathophysiological mechanisms involving gut‐brain interactions, such as visceral hypersensitivity, play an important role in patients with overlapping DGBI [28]. One of the factors proposed to play a key role in visible abdominal distension is slow transit [13]. In agreement with this, we observed a tendency toward a stronger relationship between IBS‐C and visible abdominal distension in the absence of bloating compared with IBS‐D. However, based on the lack of measurements of gut physiology in the current study and the absence of a strong relation between IBS subtype and oro‐anal transit time [29], the proposed relations between bloating, visible abdominal distension and gut physiology should be interpreted with caution.

Since bloating and visible abdominal distension in patients with DGBI, including IBS and FD, may partly differ in pathophysiological mechanisms, it might be important to differentiate between these two symptoms to better understand IBS and FD pathophysiology and to select the optimal treatment strategy. A challenge can be to distinguish between bloating and visible abdominal distension in some languages (e.g., Spanish) [30]. In those particular languages, this distinction requires a more thorough assessment of symptoms or the use of pictograms to improve clarity during symptom evaluation [30]. If bloating is the main symptom, treatment could be more focused on reducing visceral hypersensitivity, whereas the treatment of distension could focus on accelerating transit time, particularly in patients with IBS‐C, although studies investigating the optimal treatment strategies for these symptoms are sparse [11]. Based on the current evidence, reducing the intake of foods rich in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) can help to reduce symptoms of both bloating and abdominal distension [31]. Secretagogues (e.g., linaclotide), may also be helpful, particularly if the symptoms are associated with constipation [11, 32]. Other treatment options are neuromodulators, such as low dose tricyclic antidepressants (e.g., amitriptyline), that can reduce visceral hypersensitivity and beneficially influence abnormal brain‐gut interactions [11]. A promising and relatively new option to treat visible abdominal distension is biofeedback to treat underlying abdomino‐phrenic dyssynergia [33, 34].

Intestinal gas‐related symptoms can be embarrassing to report and data on these symptoms in DGBI are sparse. One of the reasons for the lack of data could be that most of these intestinal gas‐related symptoms, especially flatulence and belching, are common in the general population, and might be considered normal physiological activity until reaching a level where they become bothersome [6, 35, 36]. This transition from physiology to pathology most likely lies on a continuum with many factors, including central mechanisms and social factors, influencing the threshold for each individual. By using an anonymous survey, we tried to maximize the reliability of the assessment of these symptoms [37]. We showed that intestinal gas‐related symptom burden was higher in individuals fulfilling the criteria for IBS and/or FD compared with the reference group, including a higher impact on daily life. The intestinal gas‐related symptom burden did not differ between EPS and PDS, although a higher burden in PDS would be expected based on the dominant symptoms of bothersome postprandial fullness and early satiation [6].

This study has several strengths. Due to the population‐based character of the study, without the participants knowing that the aim of the study was to investigate gas‐related symptoms, it was possible to not only estimate the overall population‐based prevalence of bloating, visible abdominal distension, and intestinal gas‐related symptoms but to do this also for individuals who fulfilled the criteria for IBS and FD on a population‐based level. Furthermore, this is one of the first studies investigating the presence of bloating and visible abdominal distension as two separate symptoms in IBS and FD; this made it possible to support previous data that these symptoms can exist independently [27, 38]. To clearly differentiate between bloating and distension and to take potential translation problems into account, we did not simply rely on the words bloating or distension in our questions. Rather, we explained to the study participants what each of these words means, asking them about tension or pressure in the abdomen (bloating) and if their abdomen looked unusually large (distension). Despite distinguishing between bloating and visible abdominal distension in the survey, we have to acknowledge that it may still be difficult to recall them as separate symptoms for some participants.

Limitations of this study were that the IBS and FD diagnoses were based on a questionnaire. Other causes of symptoms could therefore not be excluded by clinical assessment, including a gastroscopy to rule out organic causes of dyspepsia, which is formally needed to diagnose Rome IV FD. We tried to reduce this limitation by excluding individuals with a self‐reported history of certain organic gastrointestinal diseases or bowel resection that could result in IBS‐ or FD‐like symptoms, similar to what has been done in previous studies [22, 37]. Furthermore, the data were collected during the first year of the COVID‐19 pandemic, which could have influenced many factors including psychological distress caused by social restrictions and GI symptoms caused by a COVID‐19 infection [39]. We are confident that our results are still reliable since all data, including those in the reference group, were collected during the same period. For the regression analyses investigating the relationship between bloating and/or distension and IBS subtypes, we have to acknowledge that the multivariable models had a relatively low power due to the small number of individuals within some IBS subtypes, resulting in a lower reliability of these estimates.

In this study, we showed that experiencing bloating and/or visible abdominal distension at least once a week, including visible abdominal distension alone, are highly prevalent in individuals with IBS and FD, and even more prevalent in individuals with overlapping IBS and FD. Furthermore, we identified associated factors of bloating and distension and highlighted that intestinal gas‐related symptom burden was higher in individuals with IBS and FD. This study provides arguments for using bloating and visible abdominal distension as supportive criteria for IBS and FD. More studies are needed to further reveal the mechanisms behind bloating and visible abdominal distension, to know the clinical relevance of differentiating between these two symptoms, and to improve treatment strategies of these very common symptoms in order to improve the quality of life for the many individuals who experience them.

Funding

Danone Nutricia Research, Swedish Research Council (Grant 2021–00947), the ALF‐agreement (grant ALFGBG‐965173), Erling‐Persson Foundation and the Faculty of Medicine, University of Gothenburg.

Ethics Statement

The study was reviewed by the Institutional Review Board (IRB) at the University of North Carolina at Chapel Hill (US) and was determined to be exempt from IRB oversight due to the anonymity of the online survey method.

Consent

All participants gave consent prior to completing the survey.

Conflicts of Interest

Tom van Gils: has received a speaker honorarium from Takeda. Max J. Schmulsson: has received a speaker honorarium from Prometis/Promedix Mexico, Daewoong South Korea, M8 Pharmaceuticals Mexico, Biopas Colombia, Megalabs Ecuador, and served as a Consultant/Advisory Board for Prometis/Promedix Mexico, GEMELLI BIOTECH, Daewoong South Korrea, and M8 Pharmaceuticals Mexico. Alfa Sigma México: other. Magnus Simrén: has received unrestricted research grants from BioGaia, and served as Consultant/Advisory Board member Biocodex, Tillotts, BioGaia, Renapharma, and AlfaSigma, and as a speaker for Tillotts, Takeda, Biocodex, Sanofi, Abbvie, Janssen Immunology, Pfizer, BioGaia, Renapharma, Mayoly and Bromatech. No conflicts of interest are declared by the other authors.

Permission to Reproduce Material From Other Sources

The authors have nothing to report.

Supporting information

Supporting Information S1

van Gils, Tom , Katsumata Ryo, Hreinsson Jóhann P., et al. 2026. “Bloating, Visible Abdominal Distension, and Other Intestinal Gas‐Related Symptoms in Irritable Bowel Syndrome and Functional Dyspepsia,” United European Gastroenterology Journal: e70186. 10.1002/ueg2.70186.

Data Availability Statement

The data that support the findings of this study are available from the Rome Foundation under a data use agreement.