Constipation in adults - red flag symptoms

Dr Pipin Singh outlines red flag symptoms to consider in patients presenting with constipation.

Bowel cancer: a potential cause (Photograph: SPL)
Bowel cancer: a potential cause (Photograph: SPL)

Red flag symptoms

  • Change in bowel habit for more than six weeks
  • Persistent rectal bleeding
  • Weight loss, night sweats, appetite loss
  • Family history of colorectal pathology
  • Bowel distension, pain and vomiting
  • Abdominal bloating
  • New-onset confusion
  • Significant weight gain


Constipation is a common presenting symptom in primary care. A careful history and examination is crucial to identify a possible underlying cause. This article focuses on adult constipation.

It is essential to identify what the patient means by constipation. A normal bowel habit for one person may be very different to that of another. This may be a result of social and dietary variations and possibly even behaviour acquired as a child.

Constipation is the incomplete passage of hard stools. There may be associated straining, bleeding, pain, palpable faeces in the rectum and/or a sensation of incomplete defecation (tenesmus). The stool can be described on the Bristol Stool Chart as type 1.


When a patient presents with constipation, it is important to know how old they are, what they mean by constipation, what is a 'normal' bowel habit for them and when this changed.

It is important to ask about:

  • Any rectal bleeding and whether they are passing flatus
  • Weight loss or loss of appetite
  • Abdominal pain, bloating, nausea and/or vomiting, or urinary symptoms
  • Night sweats

Is the patient prone to constipation and if so, what interventions normally work? Elicit whether the patient has tried anything to alleviate their constipation, such as over-the-counter treatments, and whether they are taking any new medications (particularly opioid-based medication).

It is worth enquiring about any changes in dietary habits and asking about smoking and alcohol.

Determine whether there is any significant family history of serious bowel problems.

Why has the patient decided to present now and what are their fears around the problem?

In the elderly population, particularly institutionalised patients, constipation may present as confusion. It may also present with urinary retention. It is worth asking carers or the nursing staff if the patient has a stool chart and if not, consider one to get a objective picture of the patient’s pattern of defecation.


Look for any signs suggestive of anaemia (pale conjunctiva, nail changes). Check whether the abdomen is distended and whether there are any palpable masses on superficial and deep examination. You may even feel faeces on palpation. Listen for bowel sounds. Tinkling bowel sounds may signify obstruction.

A detailed pelvic examination may be necessary if indicated by the history. In addition, a chaperoned rectal examination palpating for a rectal mass, faeces, evidence of overflow and - if indicated - rectal tone may be needed.


Patients aged under 40 years usually warrant minimum investigation if no red flags are present. Simple dietary advice may be all that is necessary.

If patients present with red flags suggestive of serious underlying pathology then various investigations may be required, including:

  • FBC
  • Ferritin
  • U&Es
  • Calcium
  • TSH (if the history dictates)
  • HbA1c
  • LFTs
  • Coeliac screen
  • CA125
  • CEA

Referral may be needed for further investigations including barium enema, flexible sigmoidoscopy, colonoscopy, CT colonography, abdominal/pelvic CT and bowel transit studies, depending on your local arrangements.

Differential diagnosis

The differential diagnosis for constipation is wide. Common causes seen in primary care tend to be related to patients being elderly, poor intake of fibre or constipation-predominant IBS (IBS-C).

Iatrogenic constipation (for example, secondary to opiates) is also common, particularly in patients on complex analgesic regimens - for example those with malignancy or approaching the end of life - so concurrent prescription of laxatives may be appropriate.

Gastrointestinal causes include colorectal carcinoma, bowel obstruction (for which the differential is wide), diverticular disease, bowel ileus, volvulus, Crohn's disease, rectal prolapse or anorectal abscess.

Urogynaecological causes may include ovarian mass or a rectocele.

Treatment and newer drugs

Treatment will depend on the underlying cause and may range from simple laxatives to more complex laxative regimens for idiopathic constipation. More complex diagnoses will require medical or surgical intervention.

Familiarise yourself with the newer drugs available for constipation. Some of the newer agents available include linaclotide, lubiprostone and prucalopride (licensed in women only).

Laxatives can be classed as bulk-forming agents, stimulant laxatives, osmotic laxatives, and stool softeners. Enemas and suppositories are also available.

  • Dr Singh is a GP in Northumberland. This article first appeared on 23 June 2011 and was updated by the author in December 2018.

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