Dr Henry WeiGastroenterology & Endoscopy
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Constipation in primary care: assessment and treatment

Assess stool consistency, evacuation and daily function, then prescribe an adequate treatment trial and review the response.

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Author: Dr Henry Wei. Sources checked 16 October 2026.

In practice

Assess stool consistency and the ability to empty

I distinguish hard stools from difficulty emptying despite soft stool. I review medicines, impaction and the actual doses and duration of previous treatment before choosing the next step.

Guidance behind this advice
GP consultation tool

Use the IBS consultation navigator

If recurrent abdominal pain or discomfort and bowel change suggest IBS-C, the IBS navigator can help review tests and treatment response. Constipation without that pattern needs its own assessment, including evacuation and possible overflow.

1. Clarify symptoms and exclude impaction

Normal bowel frequency varies. Ask about stool form, straining, blockage, incomplete emptying, manual assistance and impact on daily life. Review opioids, anticholinergics, iron, diet and previous pelvic surgery.

Examine the abdomen and offer a rectal examination for suspected loading or an evacuation disorder. Severe pain, vomiting, distension or inability to pass wind needs acute assessment. Bleeding, IDA, weight loss or a mass warrants investigation.

Clear confirmed impaction before adding bulking fibre, then provide maintenance treatment.

2. Agree practical food and toileting changes

Encourage regular meals, time for the toilet after a meal, a supported position, appropriate fluid intake and activity. Introduce soluble fibre gradually. Two green kiwifruit daily or coffee may help if tolerated; respect fluid restrictions.

3. Match treatment to the problem

Common NZ treatment options
ProblemOptionsReview
Low fibre intakePsyllium, e.g. Konsyl-D or Metamucil.Increase gradually; check bloating and fluid needs.
Hard stoolMacrogol, e.g. Movicol or Molaxole. Lactulose is an alternative.Adjust to soft, comfortable stools; lactulose may cause gas.
Inadequate responseAdd senna (Senokot) or bisacodyl (Dulcolax).Check dose, regular use, cramps and diarrhoea.
Difficult evacuation despite soft stoolAssess outlet function.Consider manometry/balloon expulsion and targeted biofeedback.

4. Review adequate trials and refer when needed

Check what was actually taken and the response before escalating. Persistent evacuation difficulty may need anorectal testing and biofeedback before transit studies.

Specialist options include prucalopride (Resotrans) after inadequate usual laxatives; it is not routinely funded in NZ. Surgery is reserved for highly selected patients after objective assessment. Include the bowel pattern, examination and treatment trials in the referral.

Clinical pearls

  • Constipation alone usually does not indicate serious colonic disease; investigate alarm features or a concerning new change.
  • Loose leakage can be overflow around retained stool. Assess before prescribing loperamide.
  • Biofeedback for a defaecatory disorder retrains relaxation and coordination; it is more than pelvic-floor strengthening.
Diagrams for patient discussions
Explore the explanation

Hard stool, difficult emptying or both?

Choose a view
Explanatory diagram
Water absorption and stool consistencyA straightened segment of large bowel is shown as a cutaway, with softer stool on the left and harder stool on the right. A rightward arrow represents passage, and outward arrows represent absorption of water through the bowel wall into the body. Slower passage may lead to harder stool. This is a physiological concept, not a patient-specific transit test, a blockage diagram or a claim that all constipation is dehydration. Length, shapes and scale are exaggerated.The large bowel absorbs water from its contents Water absorbed into the bodySofter contentsDrier, harder stool Slower passage can allow more water to be absorbed.Not all constipation is caused by slow transit or low fluid intake.

Stool and water

The large bowel absorbs water. Slower passage can make stool harder, but some people have difficulty emptying even when stool is soft. Drinking extra water alone does not fix every cause.

Simplified illustrations, not to scale. These show an example, not your own anatomy or test result.

Read every diagram explanation

Stool and water

The large bowel absorbs water. Slower passage can make stool harder, but some people have difficulty emptying even when stool is soft. Drinking extra water alone does not fix every cause.

How emptying works

The rectum, pelvic floor and anal muscles need to coordinate. If the outlet does not relax properly, specialist testing and retraining may help. Treatment may involve learning to relax these muscles, rather than simply strengthening them.

Why loose leakage can occur

Sometimes liquid stool leaks around retained hard stool. This can be mistaken for diarrhoea. Your GP may need to examine you before changing laxatives or adding an anti-diarrhoeal medicine.

Choosing treatment

I review medicines, stool consistency, emptying and any warning signs. Food and toilet changes, laxatives and pelvic-floor treatment have different roles. Persistent symptoms need a planned review.

Information to share with your patient

Related clinician articles

References

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