Gut health glossary

Gut health comes with its own vocabulary. Here's what the common words mean, in plain English, with a link to where each definition comes from. Terms with their own page are linked.

Anal fissure

A small tear in your anus that causes pain when you poo. It can also cause bright red blood. (NHS)

Bloating

A feeling of fullness or swelling in your belly. (NIDDK)

Bristol stool scale

A 7-point chart doctors use to describe poop, from type 1 (separate hard lumps) to type 7 (entirely liquid). (NHS England)

Bulk-forming laxative

A laxative, such as ispaghula husk, that adds fiber to poo so it's bigger and softer. Takes up to 3 days. (NHS)

Coeliac disease

An autoimmune condition where the immune system reacts to gluten (in wheat, barley and rye). (NHS)

Constipation

Pooing less often than usual or finding it hard to poo. The NHS says it's likely if you haven't pooed at least 3 times in the last week, or you're pooing less often than usual. (NHS)

Distention

When your belly actually becomes larger than usual. Only about half of people with bloating also have distention. (NIDDK)

Diverticula

Small bulges in the wall of the large intestine. Most people get some with age, usually without symptoms. (NHS)

Disorder of gut-brain interaction

The current name for functional GI disorders like IBS, related to how the brain and gut work together. (NIDDK)

Fecal impaction

When poo builds up in the rectum after long-term constipation. Diarrhea can leak around it. (NHS)

Flatus

The gas you pass from your bottom. Passing gas 8 to 14 times a day is average; up to 25 is considered normal. (NIDDK)

FODMAPs

A group of carbohydrates that are poorly absorbed in the small intestine and can trigger IBS symptoms in some people. (Monash University)

Fructans

A FODMAP (an oligosaccharide) found in foods such as wheat, rye, onions, garlic and legumes. (Monash University)

IBD (inflammatory bowel disease)

Long-term conditions that cause inflammation of the gut, mainly Crohn's disease and ulcerative colitis. Not the same as IBS. (NHS)

IBS (irritable bowel syndrome)

A functional GI disorder, now called a disorder of gut-brain interaction, with tummy pain and changes in bowel movements. (NIDDK)

IBS-C, IBS-D, IBS-M

IBS subtypes: mostly constipation, mostly diarrhea, or mixed. (NIDDK)

Insoluble fiber

Fiber that doesn't dissolve in water. It adds bulk to stool and helps food move faster. (MedlinePlus)

Lactose intolerance

When your body can't easily digest lactose, a sugar in milk and dairy. (NHS)

Malabsorption

When your gut doesn't properly absorb nutrients from food. (NIDDK (NIH))

Oral rehydration solution

A powder you mix with water to replace the sugar, salts and minerals lost through diarrhea or vomiting. (NHS)

Osmotic laxative

A laxative, such as lactulose or macrogol, that draws water into the bowel to soften poo. Takes 2 to 3 days. (NHS)

Piles (hemorrhoids)

Lumps inside and around your bottom. They can cause bright red blood after a poo and itching. (NHS)

Soluble fiber

Fiber that attracts water and turns to gel, slowing digestion. Found in oats, barley, beans and lentils. (MedlinePlus)

Stimulant laxative

A laxative, such as senna or bisacodyl, that makes bowel muscles push poo out. Takes 6 to 12 hours. (NHS)

Tenesmus

The feeling that you need to poo even though your bowels are already empty. (MedlinePlus)

Definitions are for understanding, not diagnosis. If a term on this page describes something you're dealing with, talk to a GP.

Sources

1. Bristol stool chart (for carers) (NHS England)
2. FODMAPs and IBS (Monash University)
3. High and low FODMAP foods (Monash University)
4. Tenesmus (MedlinePlus)
5. Symptoms & Causes of Gas (NIDDK)
6. Symptoms & Causes of Diarrhea (NIDDK (NIH))
7. Definition & Facts for IBS (NIDDK)
8. Inflammatory bowel disease (IBD) (NHS)
9. Coeliac disease (NHS)
10. Lactose intolerance (NHS)
11. Laxatives (NHS)
12. Dietary fiber (MedlinePlus)
13. Constipation (NHS)
14. Piles (haemorrhoids) (NHS)
15. Anal fissure (NHS)
16. Diverticular disease and diverticulitis (NHS)
17. Dehydration (NHS)

Last reviewed 2026-11-04

FixMyGut is not affiliated with or endorsed by the NHS, NIH, NICE, Mayo Clinic or Monash University.