Pseudomembranous colitis: causes and treatment

The name describes what a doctor sees when looking at the colon. "Colitis" means inflammation of the colon, and a "pseudomembrane" is a false membrane: a layer made of inflammatory cells and debris that sits on the surface of the bowel lining instead of being part of it.

A review in Disease-a-Month explains that on endoscopy these appear as raised yellow-white nodules or plaques, which can be scattered over normal or red lining. In severe disease they can merge to cover the whole surface.

It is a description of the bowel rather than one single disease. Most of the time it is a sign of a C. difficile infection, which is why the two terms are so often used together.

The NHS explains that C. diff bacteria usually live harmlessly in the bowel among many other bacteria. When antibiotics change the balance, C. diff can multiply and cause infection. NHS inform adds that it then produces toxins that make you ill, and that the bacteria are found in the bowel of about 1 in every 30 healthy adults.

The NHS lists these things as raising the chance of infection.

• Being over 65.

• Taking, or having recently taken, antibiotics.

• A long stay in hospital or a care home.

• A weakened immune system, for example from diabetes, kidney failure or chemotherapy.

• Taking a proton pump inhibitor such as omeprazole, or other medicines that reduce stomach acid.

• Having had a C. diff infection before.

The Disease-a-Month review stresses that C. difficile is still the most common cause, but that pseudomembranes can also follow other problems. These include Behcet's disease, collagenous colitis, inflammatory bowel disease, ischaemic colitis, other bacterial, parasitic or viral infections, and a small number of drugs and toxins.

This matters when a stool test for C. difficile is negative but symptoms persist. The review suggests early input from a gastroenterologist and a look inside the bowel in that situation, with biopsies if pseudomembranes are seen, because the tissue can offer clues to the underlying cause.

It is a reminder that persistent bloody or severe diarrhoea should not simply be put down to an antibiotic. Tell your doctor which antibiotics you have taken and when.

The NHS lists common symptoms of C. diff infection as diarrhoea, a high temperature, loss of appetite, feeling sick and a stomach ache. NHS inform adds that the diarrhoea is watery and can be bloody, that tummy cramps are typical, and that signs of dehydration include a dry mouth, headaches and peeing less often.

Symptoms usually develop during antibiotic treatment or in the weeks after finishing. NHS inform notes that diarrhoea is a common side effect of antibiotics, so having it does not by itself mean you have C. diff, and your GP may suggest a stool sample to confirm.

The NHS advises an urgent GP appointment or NHS 111 if you have diarrhoea while taking or having recently taken antibiotics, if you have bloody diarrhoea or bleeding from the bottom, or if diarrhoea lasts more than 7 days.

NHS inform advises phoning your GP for severe diarrhoea, fainting, severe abdominal pain or a high fever. Phone ahead rather than turning up, because visiting a surgery can put others at risk. Call 999 or go to A&E for confusion, drowsiness, a very rapid heart rate or collapse.

Most cases are manageable, but NHS inform lists serious complications such as damage to the bowel and severe dehydration, which can cause drowsiness, confusion, a rapid heart rate and fainting. The NHS says infections can sometimes lead to sepsis.

The Disease-a-Month review reports that a small proportion of people with C. difficile infection develop a fulminant form, with severe ileus, toxic megacolon, perforation of the bowel or septic shock, and that some of these patients need surgery to remove part of the colon. The review gives an estimate of 3 to 8% of patients with infection, from US data.

NICE advises referring people to hospital if they are severely unwell or their symptoms worsen rapidly, and urgently if infection is life-threatening. It also notes that people at higher risk because of age, frailty or other illnesses may be considered for hospital care.

The NHS says a doctor who suspects C. diff infection may ask for a stool sample to be tested. NHS inform adds that a blood test may help judge severity and that scans or other tests in hospital may check whether the bowel is damaged.

NICE says that on assessment, clinicians should work out whether it is a first or repeat episode, how severe it is, and whether age, frailty or other conditions raise the risk of complications.

Looking inside the bowel is not needed for most people. The review in Disease-a-Month describes flexible sigmoidoscopy or colonoscopy as the next step when stool tests are negative and symptoms continue despite treatment, because the camera can show pseudomembranes directly.

According to the NHS, C. diff infection is treated by stopping any antibiotics you are already taking, if possible, and taking a new 10-day course of another antibiotic that can treat it. NICE advises reviewing existing antibiotics and stopping them unless essential, and reviewing the need for acid-reducing medicines and other drugs that could worsen dehydration.

NICE says adults should be offered an oral antibiotic and that fluid loss should be managed as for acute gastroenteritis. NICE specifically says not to offer anti-motility medicines such as loperamide. The NHS agrees, and advises drinking plenty of water.

The NHS tells people to finish all the antibiotics prescribed for C. diff, even if they feel better. NHS inform describes the course as 10 to 14 days, and says rarely a serious infection may require surgery. Mild cases may be treated at home, and hospital care may be needed for more serious ones.

NICE does not advise antibiotics to prevent C. diff, nor prebiotics or probiotics for prevention.

The NHS says symptoms should improve a few days after starting the new antibiotic, but that it may be 1 to 2 weeks before the infection fully clears. Go back to the GP if you get worse or if symptoms return. NHS inform says they return in around 1 in 5 cases, and treatment may need repeating.

The NHS says if the infection comes back 2 or more times, you may be offered a faecal microbiota transplant, in which bacteria from a healthy person's stool are placed in the gut. NICE also says to consider this for adults with 2 or more previous episodes.

C. diff spreads easily. The NHS and NHS inform advise staying at home until at least 48 hours after diarrhoea stops, washing hands with soap and water rather than hand gel, cleaning the toilet area, washing soiled clothes separately at the highest possible temperature and not sharing towels.