Constipation, diarrhoea or alternating changes in bowel habits are among the most common reasons for a gastroenterology consultation. Sometimes they result from diet, stress, medication or functional bowel disorders, but they may also be a symptom of diseases that require diagnosis. In addition, chronic constipation and diarrhoea very often affect the anal area, causing pain, itching, fissures, haemorrhoids or irritation.
This article explains when bowel habit problems should be discussed with a gastroenterologist, when proctological assessment may also be needed and which symptoms should not be ignored. If the problem lasts longer, recurs or affects daily functioning, it is worth booking a gastroenterology consultation.
Author: Dr Mateusz Jóźwiak, gastroenterologist | Medical review: Dr Kamil Smok, surgeon and proctologist | Publication date: 29.06.2026 | Last updated: 29.06.2026
What do changes in bowel habits mean?
Bowel habits may vary among healthy people. For one person, daily bowel movements are normal; for another, several times a week may be normal. A problem begins when there is a clear change compared with the previous rhythm, stools become very hard or very loose, there is strong straining, pain, a feeling of incomplete evacuation or a sudden need to use the toilet.
Constipation does not only mean infrequent bowel movements. It may also mean hard, lumpy stools, difficulty passing stool, long sitting on the toilet, strong straining, a feeling of blockage in the anus or the impression that the bowel movement was incomplete.
Diarrhoea, in turn, does not always mean a one-off “food poisoning”. If loose stools recur, last for a long time, wake the patient at night, contain blood or mucus, lead to weakness or weight loss, they require diagnosis.
“Patients often say: I have constipation or I have diarrhoea. For the doctor, it is important to clarify: since when, how often, what the stool looks like, whether there is blood, pain, weight loss, night-time symptoms and what medications the patient is taking. Only then can diagnostics be planned reasonably.”
— Dr Mateusz Jóźwiak, gastroenterologist
The most common causes of constipation
Constipation may result from simple everyday causes, but also from general diseases, medications or bowel function disorders. That is why treatment should not be limited to random use of laxatives.
Common causes of constipation include:
- a diet low in fibre,
- too little fluid intake,
- low physical activity,
- delaying bowel movements despite the urge,
- long sitting on the toilet and strong straining,
- stress, tension and irregular lifestyle,
- some medications, such as selected painkillers, iron supplements, antidepressants or some cardiac medications,
- hypothyroidism and other hormonal disorders,
- pregnancy,
- irritable bowel syndrome with constipation predominance,
- coordination disorders of the pelvic floor muscles,
- strictures, tumours or other organic bowel diseases — especially when alarm symptoms are present.
In many patients, constipation is functional in nature, but a functional diagnosis should be made cautiously only after assessing symptoms, the patient’s age, duration of the problem and the presence of so-called red flags.
The most common causes of chronic or recurrent diarrhoea
Diarrhoea may be acute, for example after infection or food poisoning, but it may also be chronic or recurrent. In that case, it requires a broader view, because the causes may be very different.
Possible causes of recurrent diarrhoea include:
- gastrointestinal infections, including past or prolonged infections,
- food intolerances, for example lactose or fructose intolerance,
- coeliac disease,
- irritable bowel syndrome with diarrhoea predominance,
- inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis,
- microscopic colitis,
- bile acid malabsorption,
- pancreatic diseases and fat digestion disorders,
- side effects of medications,
- hyperthyroidism,
- stress and disorders of the gut–brain axis,
- less commonly — cancers of the digestive tract.
This is why chronic diarrhoea should not be treated only with a probiotic or medication that slows bowel movements. First, it is necessary to understand whether the problem is functional, inflammatory, infectious, medication-related, hormonal or linked to malabsorption.
Constipation and diarrhoea — when not to delay?
| Symptom | Why is it important? |
|---|---|
| blood in the stool or rectal bleeding | requires identifying the source of bleeding; it is not always haemorrhoids |
| unintentional weight loss | may suggest inflammatory disease, malabsorption or another organic disease |
| anaemia or weakness | may indicate chronic bleeding, deficiencies or inflammation |
| diarrhoea waking the patient at night | less typical for a simple functional disorder and requires assessment |
| fever, severe abdominal pain or dehydration | may indicate infection, inflammation or a condition requiring faster help |
| new change in bowel habits after the age of 40–50 | should not automatically be explained by stress or diet |
| alternating constipation and diarrhoea with pain or bloating | may occur in IBS, but requires differentiation from other diseases |
The role of the gastroenterologist — not just diet and probiotics
A gastroenterologist assesses the function of the entire digestive tract. In constipation or diarrhoea, it is important to determine whether the problem mainly involves the intestines, diet, medications, hormones, microbiota, functional disorders, inflammation or diseases requiring further diagnostics.
During a gastroenterology consultation, the doctor may ask about:
- frequency of bowel movements,
- appearance and consistency of the stool,
- presence of blood, mucus, pus or fat in the stool,
- abdominal pain, bloating, urgency and a feeling of incomplete evacuation,
- night-time symptoms, fever, weight loss, weakness,
- diet, fluid intake, physical activity and stress,
- medications and supplements,
- thyroid disease, diabetes, autoimmune diseases,
- family history of bowel diseases and colorectal cancer.
Depending on the situation, the doctor may consider laboratory tests, stool tests, assessment of inflammation, tests for coeliac disease, thyroid hormone assessment, ultrasound, colonoscopy or other tests. Not every patient needs full diagnostics immediately — the scope of testing should depend on symptoms and risk.
Why is proctology sometimes an important complement?
Bowel habit disorders very often affect the anal area. A patient may come to the gastroenterologist with constipation but also suffer from an anal fissure, pain during bowel movements or haemorrhoids. A patient with chronic diarrhoea, on the other hand, may experience increased itching, burning, skin irritation and difficulty maintaining hygiene.
Chronic constipation may contribute to problems such as:
- haemorrhoidal disease,
- anal fissure,
- pain and burning during bowel movements,
- anal skin folds,
- mucosal prolapse or a feeling of blockage when passing stool,
- increased fear of bowel movements when every bowel movement is painful.
Recurrent diarrhoea, in turn, may lead to:
- irritation of the skin around the anus,
- itching and burning,
- worsening of haemorrhoid symptoms,
- inflammation and maceration of the skin,
- a feeling of moisture and staining of underwear,
- worsening pain when an anal fissure coexists.
In such situations, regulating bowel function alone may not be enough if a local proctological complication has already developed. Then a proctological consultation may be helpful, and sometimes also anoscopy.
“Constipation and diarrhoea very often have proctological consequences. If the patient has pain during bowel movements, blood on toilet paper, itching or a lump near the anus, we need to assess not only the intestines but also the anal area.”
— Dr Kamil Smok, surgeon and proctologist
Constipation can drive pain — the vicious circle of anal fissure
One frequent example of cooperation between a gastroenterologist and a proctologist is anal fissure. Hard stool and strong straining may damage the anoderm, the delicate skin of the anal canal. Pain during bowel movements appears, and the patient begins to avoid going to the toilet. Stools become even harder, and the next bowel movement becomes even more painful.
In such a situation, treating the fissure alone without regulating bowel movements may be ineffective. On the other hand, diet alone may not be enough if pain, sphincter spasm and the wound have persisted for a long time. That is why a combined gastroenterological and proctological approach may sometimes be needed.
Are probiotics enough?
Probiotics may be helpful in selected situations, for example after antibiotic therapy or in some functional disorders, but they should not be treated as a universal treatment for constipation and diarrhoea. A patient with blood in the stool, weight loss, fever, anaemia, night-time diarrhoea or a long-lasting change in bowel habits needs diagnostics, not only supplementation.
Similarly, fibre is not the solution for everyone. In some patients it may help, especially with constipation, but in others it may worsen bloating, pain and discomfort. That is why increasing fibre is best done gradually and with adequate hydration, and in severe symptoms — after consulting a doctor.
Treatment — a comprehensive approach
Effective treatment depends on the cause. Constipation related to diet and low activity is treated differently from constipation caused by medication, pelvic floor disorders, inflammatory diarrhoea, infection-related diarrhoea, medication-related diarrhoea or functional diarrhoea.
The treatment plan may include:
- diet modification, but adapted to symptoms, not random,
- gradual increase of fibre if indicated,
- adequate hydration,
- regular physical activity,
- treatment of constipation or diarrhoea matched to the cause,
- stopping or changing medications that worsen symptoms — only after consulting a doctor,
- laboratory or endoscopic diagnostics if indicated,
- treatment of anal fissure, haemorrhoids, itching or irritation if proctological complications have occurred,
- work on stress, sleep and regular meals if they worsen symptoms.
The most important thing is not to treat the symptom separately from the cause. If the patient has an anal fissure, pain and the wound need to be treated, but the stool also needs to be regulated. If the patient has diarrhoea and anal itching, the irritation needs treatment, but it is also necessary to find out why diarrhoea keeps returning.
When gastroenterologist, when proctologist?
| Situation | Where to start? |
|---|---|
| constipation without anal pain, but with bloating and a feeling of incomplete evacuation | gastroenterology consultation |
| recurrent diarrhoea, night-time diarrhoea, diarrhoea with mucus or weight loss | gastroenterology consultation and diagnostics of the cause |
| anal pain during bowel movements, blood on toilet paper, suspected fissure | proctological consultation, often together with stool regulation |
| lump near the anus, itching, burning, prolapsing haemorrhoids | proctological consultation |
| alternating constipation and diarrhoea with abdominal pain | usually gastroenterology consultation, with assessment of red flags |
| constipation or diarrhoea together with anal symptoms | preferably combined approach: gastroenterologist and proctologist |
Frequently asked questions
Is constipation always caused by diet?
No. Diet is important, but constipation may also result from medications, hormonal diseases, bowel function disorders, pelvic floor problems or organic diseases. If the problem lasts long, recurs or appears suddenly, it is worth consulting a doctor.
When does diarrhoea require consultation?
Consultation is needed for chronic, recurrent or night-time diarrhoea, diarrhoea with blood, mucus, fever, dehydration, weight loss, severe abdominal pain or weakness. In such situations, it is not worth relying only on symptomatic treatment.
Are alternating constipation and diarrhoea IBS?
They may occur in irritable bowel syndrome, but this should not be assumed automatically. First, the duration of symptoms, the patient’s age, alarm symptoms, test results and possible other causes should be assessed.
Can constipation cause haemorrhoids?
Yes, chronic straining and hard stools may worsen haemorrhoidal disease. This does not mean, however, that every rectal bleeding episode is caused by haemorrhoids — proctological assessment is recommended when bleeding occurs.
Is colonoscopy needed for bowel habit problems?
Not always. Colonoscopy depends on the patient’s age, alarm symptoms, family history, test results and the nature of the symptoms. The decision is made by the doctor after consultation.
Who should I see at Wyspa Medycyny Przyjaznej?
If constipation, diarrhoea, bloating and abdominal pain dominate, it is worth starting with a gastroenterology consultation with Dr Mateusz Jóźwiak. If anal pain, bleeding, a lump, itching or suspicion of fissure or haemorrhoids occurs, a proctological consultation with Sara Godyńska, MD, Justyna Szul, MD or Dr Kamil Smok may be helpful.
Do constipation, diarrhoea or pain during bowel movements keep returning?
Do not treat only the symptom. Start by identifying the cause and checking whether the problem involves the intestines, the anus or both areas at the same time.
Book a gastroenterology consultation →Summary
Chronic constipation and recurrent diarrhoea may have many causes: from diet, medications and stress to bowel diseases requiring diagnosis. Not every change in bowel habits means a serious disease, but long-lasting, recurrent or sudden symptoms should not be ignored.
It is also important that bowel habit disorders often lead to proctological problems. Hard stool and straining may worsen haemorrhoids and anal fissure, while diarrhoea may cause itching, burning and irritation. That is why in some patients the best results come from cooperation between a gastroenterologist and a proctologist.
If intestinal symptoms dominate, start with a gastroenterology consultation. If anal pain, bleeding, a lump, itching or suspicion of fissure or haemorrhoids appears, also consider a proctological consultation.
Sources and medical context:
- AGA/ACG Clinical Practice Guideline — Pharmacological Management of Chronic Idiopathic Constipation
- British Society of Gastroenterology — Guidelines for the investigation of chronic diarrhoea in adults
- NIDDK — Symptoms & Causes of Constipation
- NIDDK — Symptoms & Causes of Diarrhea
- NICE NG12 — Suspected cancer: recognition and referral
This article is for informational purposes only and does not replace medical consultation. Blood in the stool, rectal bleeding, unintentional weight loss, anaemia, fever, night-time diarrhoea, severe abdominal pain, dehydration, sudden change in bowel habits or symptoms persisting despite treatment require medical assessment.