Ulcerative colitis

What ulcerative colitis is

Ulcerative colitis is one of the two main forms of inflammatory bowel disease. The immune system attacks the lining of the large bowel, producing inflammation that is continuous rather than patchy, superficial rather than full thickness, and that always starts at the rectum and extends upwards by some distance before stopping.

Those three features are what separate it from Crohn's disease, which can affect any part of the gut from mouth to anus, skips areas, and goes through the full thickness of the bowel wall. The distinction matters because the two are treated differently, they carry different risks, and surgery means something quite different in each.

It is a lifelong condition that runs in flares and remissions. It is not caused by anything the person did, it is not caused by diet, and it is not a psychological illness, though living with it affects mood and mood affects how symptoms feel.

How far it extends, and why that decides treatment

The single most useful thing to know about your own colitis is how far up it goes. It is measured at colonoscopy and it determines which treatments will reach the inflammation at all.

• Proctitis. Confined to the rectum, the last 15 cm or so. Treated largely with medicine delivered directly into the rectum, which reaches a far higher concentration there than anything swallowed.
• Left-sided colitis. Extends up the left side of the colon as far as the splenic flexure. Usually needs both rectal and oral treatment, which together work better than either alone.
• Extensive colitis. Reaches beyond the splenic flexure, often involving the whole colon. Needs systemic treatment, and brings forward the start of bowel cancer surveillance.

What it feels like

The symptoms track the inflammation. Rectal involvement is what produces the urgency and the bleeding, which is why those are present in almost everyone.

• Blood in the motions, mixed through rather than only on the paper
• Diarrhoea, often many times a day, including at night
• Urgency, the sense of having only a minute or two of warning
• Mucus
• Cramping low abdominal pain that eases after opening the bowels
• Tenesmus, a constant feeling of needing to go with little result
• Tiredness out of proportion to everything else, which is often the hardest part

Waking at night to open the bowels is an important symptom and is worth mentioning specifically. It separates inflammation from irritable bowel syndrome, which generally does not wake people.

How the diagnosis is made

No single test makes the diagnosis. It is made by putting together the history, the exclusion of infection, blood and stool results, and what the colonoscopy and biopsies show.

Excluding infection first

Several infections produce bloody diarrhoea that looks identical in the first week. Stool cultures and a test for Clostridioides difficile are done before anyone is committed to a diagnosis of colitis, and are repeated at each significant flare, because an infection on top of colitis is common and is treated differently.

Faecal calprotectin

A stool test that measures a protein released by inflammatory cells in the bowel wall. It does not say what the inflammation is, but it distinguishes inflammation from a functional bowel disorder reliably, and it becomes the main way activity is tracked once the diagnosis is known.

Colonoscopy with biopsies

The test that makes the diagnosis. It shows the pattern of inflammation, measures how far it extends and allows biopsies, which confirm the microscopic changes and help separate ulcerative colitis from Crohn's disease and from microscopic colitis. In acute severe disease a limited examination of the left side is done instead, because a full colonoscopy carries more risk when the colon is badly inflamed.

Your care pathway

What it can affect beyond the bowel

Ulcerative colitis is an immune condition, and in a minority of people it shows itself outside the gut as well. Some of these track disease activity and settle when the colitis settles. Others run their own course and need treating in their own right.

• Joints. The commonest. Large joint pain that follows disease activity, or a spinal arthritis that does not.
• Skin. Tender red nodules on the shins, and less commonly a deeper ulcerating rash.
• Eyes. A red, painful or light-sensitive eye needs same-week ophthalmology review rather than waiting.
• Liver and bile ducts. Primary sclerosing cholangitis is uncommon but important, because it changes both liver care and the bowel cancer surveillance interval. It is looked for on liver blood tests.
• Bones. Thinned by repeated steroid courses and by the inflammation itself.
• Blood clots. The risk rises during a flare and during hospital admission, which is why preventive treatment is given in hospital.

How it is treated

Treatment has two separate jobs: settling a flare, and keeping things settled afterwards. The medicine that does one is not always the medicine that does the other, and the commonest avoidable problem is stopping maintenance treatment once the flare has passed.

Medicines are described here by class rather than by brand, because which particular agent suits a person depends on their disease, their other conditions, what they have already tried and what is available to them. That is a conversation for the consultation.

Aminosalicylates

The foundation for mild to moderate disease, both to settle a flare and to prevent the next one. Given into the rectum, by mouth, or both together, which works better than either alone in left-sided disease. Taken properly these also appear to reduce the long-term risk of bowel cancer, which is a reason to stay on them even when things are quiet.

Corticosteroids

Effective at settling a flare and not suitable for keeping it settled. They do not heal the lining reliably, and the side effects of repeated or prolonged courses are substantial. Needing more than one course a year, or being unable to come off them, is the clearest signal that the underlying treatment needs to change. A locally acting steroid with limited absorption is used for some patterns of disease.

Thiopurines

Immune-modifying tablets used to maintain remission, often alongside a biologic. They take two to three months to work, so they are never the answer to an acute flare. Blood monitoring is required throughout.

Advanced therapies

Where the disease is moderate to severe, or has not responded to the above, there is now a genuine range of options rather than a single next step. Broadly they fall into:

• Anti-TNF agents. The longest track record, given by infusion or injection.
• Anti-integrin agents. Act on immune cell traffic into the bowel, so their effect is largely gut-specific.
• Anti-interleukin agents. Target specific inflammatory signals, with a favourable safety profile.
• JAK inhibitors. Tablets, and fast acting, which matters in severe disease. Prescribed with attention to cardiovascular and clot risk.
• S1P modulators. Also tablets, working by holding immune cells in the lymph nodes.

Choosing between them weighs speed of onset, how severe the disease is, other medical conditions, whether pregnancy is being considered, whether the person would rather take a tablet than have an infusion, and what has already been tried. In Australia, access to most of these is through the Pharmaceutical Benefits Scheme, which sets its own criteria for when each can be started and continued, and that shapes the order in which they are used.

Acute severe ulcerative colitis

About one in five people with ulcerative colitis will have at least one episode severe enough to need hospital admission. It is the part of the condition that frightens people most, and the part where outcomes have improved most.

Treatment starts with intravenous corticosteroids. About a third of people do not respond to them, and the important change in practice is that this is now identified in the first three days rather than at the end of the second week. Simple measurements on admission, including the inflammatory marker CRP, the albumin level and the endoscopic appearance, predict reasonably well who will not respond, so rescue treatment is brought forward rather than waited for.

Those who do not respond to steroids are offered rescue therapy, either a biologic or a calcineurin inhibitor, given in hospital. A colorectal surgeon is involved from the start of the admission in every case, not because surgery is likely, but because the decision is better made jointly and early than hurriedly and late.

What remission means now, and how it is measured

Feeling well is the point, but it is not the whole target, because the lining can remain inflamed in someone whose symptoms have settled. Inflammation left running is what drives the long-term risks: more flares, hospital admission, surgery and bowel cancer.

The framework used internationally is called treat to target, set out by the International Organization for the Study of IBD in its STRIDE consensus. It was updated in October 2026, as STRIDE-III, and the update is worth understanding because it changes what a disappointing result should actually lead to.

Three kinds of target, and what each one means for you

• Actionable targets. Backed by trials showing that treating towards them improves outcomes. Not reaching one, once the current treatment has been properly optimised, is a reason to change treatment.
• Adjunctive targets. Consistently linked to doing better, but without trial evidence that chasing them helps. They prompt closer monitoring and fine-tuning rather than a switch to a different class of drug.
• Patient-centred targets. Quality of life, disability and fatigue. These are formal targets in their own right, and they are handled by a shared decision rather than by a rule.

That distinction is the main practical change. Previously any missed target tended to read as treatment failure. Now only some of them mean the treatment itself should change.

The timeline

The calprotectin numbers changed

Faecal calprotectin is the stool test that tracks bowel inflammation between colonoscopies, and STRIDE-III refined the thresholds.

• Under 200. The acceptable range, in micrograms per gram.
• Under 100. Associated with deeper control, and in ulcerative colitis with healing on the biopsies.
• 100 to 200. A grey zone, read alongside symptoms and everything else rather than on its own.
• Persistently over 200 after enough time on a treatment, and after that treatment has been optimised, means the target has not been met and the plan needs revisiting.

One caution the consensus is explicit about: calprotectin should be confirmed on repeat testing rather than acted on from a single result, because the test varies more than people assume and infections, anti-inflammatory medicines and other conditions can all push it up.

Intestinal ultrasound is increasingly used alongside all of this. It is non-invasive, needs no preparation, is done in the clinic room, and in ulcerative colitis it earns its place as a monitoring tool that can pick up a response within a couple of weeks of starting treatment.

The framework is meant to be adapted to the person rather than applied as an algorithm, and it covers medically managed disease in the bowel itself rather than pouch or joint and skin complications. What it changes for you is that treatment gets judged against something measurable at a planned point, instead of drifting on because nothing has got dramatically worse.

Surgery, and what a pouch is

Surgery for ulcerative colitis differs from surgery for Crohn's disease in one fundamental way. Because the condition affects only the large bowel, removing the colon removes the disease. It is a major operation with real consequences, but it is not a holding measure.

It is considered when medical treatment has not controlled the disease, when a severe attack does not respond, when steroids cannot be stopped, or when a pre-cancerous change is found on surveillance biopsies.

It is usually done in stages. The colon is removed first and an ileostomy formed, which deals with the illness and lets the person recover their strength and come off medication. Later, many people go on to have an internal pouch constructed from the end of the small bowel and joined to the anus, so that the bowels work through the normal route again. A pouch typically means opening the bowels several times a day. Some people choose to keep a permanent ileostomy instead, and do very well with it.

Bowel cancer risk and surveillance

Long-standing inflammation of the colon raises the risk of bowel cancer above the general population. The risk is not uniform: it depends on how much of the colon is involved, how long it has been involved, how well controlled the inflammation has been, whether there is a family history, and whether primary sclerosing cholangitis is present.

That is why surveillance colonoscopy is offered on a schedule rather than at a single fixed interval, usually starting around eight years after symptoms began for people with left-sided or extensive disease. The examination is done with dye sprayed on the lining and careful inspection, with targeted biopsies, because the changes being looked for are flat and subtle rather than the obvious polyps of ordinary screening.

Two things reduce the risk. Keeping the inflammation controlled, and attending the surveillance colonoscopies. The surveillance intervals page covers the general rules after polyps; the schedule in colitis is set separately.

Pregnancy and family

Most people with ulcerative colitis have straightforward pregnancies and healthy babies. The single most important factor is being in remission when conception happens, because active disease at conception tends to stay active through the pregnancy and carries the real risks.

Most IBD medicines are continued through pregnancy, and stopping them because of pregnancy is a far more common cause of harm than the medicines themselves. A small number do need changing, and that is a conversation to have before trying rather than afterwards.

Ulcerative colitis is not straightforwardly inherited. Having a parent with it raises a child's risk somewhat above the general population, but most children of people with ulcerative colitis never develop it.

Diet, stress and living with it

No diet causes ulcerative colitis and no diet treats it. What food does affect is how comfortable you are, and during a flare most people find that reducing fibre, fat and caffeine helps them get through the day. Outside a flare, the evidence points towards an ordinary varied diet rather than restriction, and people who narrow their diet in the hope of controlling the disease generally end up less well nourished without being less inflamed.

Iron deficiency is common, from ongoing blood loss and from inflammation itself, and is worth looking for rather than assuming. Iron deficiency explains more of the tiredness than people expect.

Stress does not cause the condition. It does influence how symptoms are experienced, and living with an unpredictable bowel is itself a significant source of anxiety. Anxiety and low mood are common in inflammatory bowel disease and they are treatable, and raising them is not a distraction from the real problem.

Getting the most out of the appointment

• How many times a day the bowels open, and how many of those contain blood
• Whether you are woken at night
• Previous colonoscopy and biopsy reports, with dates, if you have them
• Every IBD medicine tried, the dose, how long for and why it was stopped
• How many steroid courses in the last twelve months
• Recent calprotectin and blood results
• Joint, skin or eye symptoms, which are easy to forget to mention
• Whether pregnancy is being considered in the next year or two

Where ulcerative colitis is managed in Sydney

A/Prof Viraj Kariyawasam is a consultant gastroenterologist and hepatologist whose practice is focused on inflammatory bowel disease. He consults at Norwest, Rouse Hill, Pennant Hills and Macquarie Park.

Colonoscopy, including surveillance colonoscopy with dye spray, is performed at Norwest Private Hospital, Macquarie University Hospital and Pennant Hills Day Surgery. New diagnoses, significant flares and people needing a treatment decision are prioritised. A referral from your GP is needed for a consultation.