Ileostomy: recognising and counteracting dehydration

Key facts at a glance

• An ileostomy gives off fluid and salt constantly – the large intestine, which would recover both, is bypassed
• Drinking less does not thicken the stool, it only reduces urine and endangers the kidneys
• The urine volume must not fall below one litre a day – it is your measuring instrument
• Early warning signs: thirst, dry mouth, headache, dark urine, tiredness. Late: dizziness, racing heart, muscle cramps, confusion
• More than 1.5 to 2 litres of output over several days is a high-output stoma – and a reason to see a doctor quickly

People with an ileostomy are told in hospital that they must drink a lot. Why this is so, how you notice that it is not enough, and when a fluid deficit becomes an emergency, hardly anyone explains. This article makes up for that.

Why the ileostomy is different

The large intestine has a job you only miss when it is gone: it extracts water and salts from the very liquid content that comes from the small intestine. With an ileostomy, the bowel ends before the large intestine. What arrives goes into the bag without this step – frequently, soft to liquid, spread over the whole day.

The Coloplast stoma handbook gives an output of 1,000 to 3,000 millilitres a day for the period after surgery; after about eight to ten weeks, the content usually thickens to a pasty consistency and the volume drops to 400 to 600 millilitres. So the small intestine adapts – but never to the point where the loss of fluid and salt disappears. The German ILCO writes in its nutrition brochure that these losses are pronounced and permanent and partly have to be compensated for life.

The mistake in thinking that endangers the kidneys

Anyone with liquid stool instinctively drinks less. With an ileostomy, that is exactly wrong. The ILCO puts it unambiguously:

“Restricting fluid intake with an ileostomy does not lead to thickening of the stool but to a reduction in urine output.”

The bowel takes what it gives off not from the drinking glass but from the body. So anyone who drinks less does not have less in the bag – but less in the bladder. And the kidneys need sufficient fluid to excrete waste products. From this follows the most important rule:

“The urine volume should not fall below one litre per day in any phase, in order to prevent kidney complications.”

The urine volume is therefore your measuring instrument. Not the amount you drink – that only says what goes in – but what the kidneys actually excrete. Anyone who rarely needs the toilet and passes little, dark urine when they do is drinking too little, whatever the glass says.

How much to drink – and what

There is no fixed number of litres for everyone, because output is individual. As a guide, the Coloplast handbook, based on recommendations of the specialist association DVET, gives two to three litres of fluid and around 7 grams of table salt a day. The ILCO advises agreeing the exact amount with the treatment team – with an ileostomy “considerably more fluid” than in the general food pyramid.

With salt, a second point is added: sodium is lost with the water. Plain water does not replace this. In its information for doctors, the ILCO names two levers to improve the bowel's fluid absorption: take electrolyte preparations and avoid very sugary and carbonated soft drinks. Sugar-rich drinks worsen the bowel's fluid absorption rather than improving it.

In practice this means: water and tea form the basis, plus salty foods and broth, if needed an electrolyte preparation from the pharmacy. Spread the amount over the day – the bowel absorbs small portions better than a litre at once.

Situations with increased need

The ILCO names three situations in which more must be drunk in addition to the normal amount: heavy sweating in heat or during sport and breastfeeding. And a fourth, which is the most dangerous: if the stool becomes watery through an intolerance or a gastrointestinal infection, this loss must be compensated additionally and the cause treated medically.

A gastrointestinal infection that means two unpleasant days for other people can lead to a serious fluid deficit within a day with an ileostomy. Anyone who is also vomiting and keeping nothing down does not wait. What heat means for travel is explained in our article on travelling and sport with a stoma.

Recognising warning signs

The German Institute for Quality and Efficiency in Health Care (IQWiG) describes the signs of fluid deficiency in two stages.

Early, mild signs:

• thirst, dry mouth and furry tongue
• headaches, difficulty concentrating
• weariness and rapid fatigue
• less frequent urge to urinate, less and darker urine

Late, serious signs:

• dry mucous membranes, sunken eyes
• dizziness after standing up quickly
• racing heart
• muscle cramps
• apathy, confusion

The IQWiG advises seeking medical or emergency medical advice quickly in the case of unusual weakness, confusion or dizziness – and expressly also if you lose a lot of fluid over several days without being able to compensate. For mild signs, drinking more over a few hours helps; after heavy sweating, isotonic drinks can be useful, for diarrhoea a salty broth.

For people with an ileostomy there is an additional early warning sign that nobody else has: the bag. If the content becomes thin as water for hours and has to be emptied much more often than usual, that is the moment to counteract – not only when your head hurts.

When it is a high-output stoma

There are figures for the line between a “bad day” and “in need of treatment”. In its guide, the German ILCO names two conditions under which specialists speak of a high-output stoma:

• an output of more than two litres a day on more than three consecutive days, or
• an output of one and a half litres on more than two consecutive days

In clinical practice, the following also applies: a high-output stoma is present when the loss can no longer be compensated by drinking, diet and medication. The ILCO warns that vital nutrients are lost with the fluid and that a high-output stoma can become life-threatening if it is not counteracted in time. Its recommendation: with persistently high output, to be on the safe side, quickly see a specialist or the hospital where the stoma was created.

To recognise these limits at all, you have to measure. A drainable bag with a scale or a measuring jug and a tally sheet for two or three days are enough. Anyone who knows the figures saves themselves the discussion on the phone with the practice – “a lot” is not a figure, “2.3 litres since yesterday” is.

What thickens the stool – and what does not

Drinking less is not an option, but the consistency can be influenced. The ILCO nutrition brochure describes how bulking agents can thicken liquid stool and recommends rather binding foods for diarrhoea. For an ileostomy, the Coloplast handbook advises avoiding food rich in fibre, fat and seeds such as mushrooms, peppers, pineapple, asparagus, nuts or oranges – they not only increase the volume but can also block the stoma. Which foods thicken and which loosen in your case is shown more reliably by a diary over a few weeks than by any list. The basics are in our article on diet with a stoma.

Medicines that slow bowel transit belong in medical hands – they are often part of the treatment for high output, but nothing to experiment with.

Frequently asked questions

I drink three litres and still have dark urine. What now?

Then your stoma is losing more than you are replacing. Measure the output for two days and talk to the practice. Also check what you drink: sugar-rich drinks can increase the loss.

Is water enough, or do I need electrolytes?

Salt is lost with the water, and plain water does not replace it. The ILCO names electrolyte preparations as a means of improving absorption. What suits you should be clarified with the treatment team.

How do I tell from the bag that something is wrong?

From the consistency and the frequency: thin as water instead of pasty, and emptying much more often than usual. This is usually visible earlier than physical signs.

When do I call the emergency services?

With confusion, pronounced weakness, dizziness with a racing heart, or if you keep nothing down because of vomiting. According to the IQWiG, these are signs of serious fluid deficiency – aggravated in an ileostomy by the ongoing loss.

Does it get better with time?

Usually yes. After eight to ten weeks, the small intestine increasingly thickens the content and the volume drops considerably. The increased need for fluid and salt remains permanently, however.

Your next step

We stock drainable bags and high-output appliances from Coloplast, Dansac, Hollister and B. Braun, plus skin protection for the particularly stressed skin around an ileostomy. Which appliance makes sense for frequent, liquid emptyings is explained in our article on one-piece and two-piece systems.

Sources

• Diet after stoma or bowel cancer surgery, Deutsche ILCO e.V., Bonn, 12/2024 (in German)
• Colostomy / ileostomy – a guide, Deutsche ILCO e.V., Bonn (keyword high-output stoma) (in German)
• Diet after stoma and bowel cancer surgery – information for doctors, Deutsche ILCO e.V. (in German)
• The little stoma handbook, Coloplast GmbH (nutrition figures according to DVET) (in German)
• Fluid deficiency (dehydration), gesundheitsinformation.de, Institute for Quality and Efficiency in Health Care (IQWiG), 18 October 2023 (in German)