Ischaemic colitis: symptoms, causes, treatment and when to get help

Patient.info says the condition may be difficult to diagnose, with nonspecific symptoms of an acute abdomen such as acute-onset abdominal pain. The pain is most frequently located in the left iliac fossa, nausea and vomiting often occur, and in later stages loose motions contain dark blood. The sudden onset helps distinguish it from inflammatory or infective colitis, where pain often has a more gradual onset, and symptoms develop over hours and, unlike infective or inflammatory colitis, continue to worsen if the person becomes systemically unstable.

• Sudden-onset tummy pain, most often on the left side of the lower abdomen.

• Nausea and vomiting, which often occur.

• Loose stools containing dark blood in later stages.

• Symptoms that develop over hours and keep worsening if the person becomes systemically unstable.

The colon (large bowel) needs a steady blood supply to stay healthy. In ischaemic colitis that supply is compromised. Patient.info explains that the transverse and descending parts of the colon are supplied by branches of the middle colic and left colic arteries, with a watershed area near the splenic flexure, which is why that part of the colon is at particular risk. Blood flow can also be impaired when the colon is distended, for example just above an obstruction, and ischaemic colitis may also be caused by venous occlusion.

Patient.info classifies bowel ischaemia into three main types: acute mesenteric ischaemia, chronic mesenteric ischaemia and ischaemic colitis. Patient.info notes that many mild cases may go unreported. NHS Highland's guidance on mesenteric ischaemia notes that isolated colon ischaemia is managed by general or colorectal surgery, because vascular reconstruction is not usually feasible.

Because the most common cause is atheroma (fatty narrowing) of the vessels supplying the bowel, Patient.info says it is mainly a disease of the elderly and rare before 60. It reports that incidence rose from 6.1 cases per 100,000 person-years in 1976 to 1980 to 22.9 per 100,000 in 2005 to 2009, and that the incidence is likely to increase as the population ages.

The same source lists predisposing factors including thrombosis or emboli in the mesenteric vessels, decreased cardiac output or arrhythmias, shock from sepsis, haemorrhage or low blood volume, trauma, strangulated hernia or volvulus, several drugs (digoxin, oestrogens, antihypertensives, cocaine and methamphetamine, vasopressin, phenylephrine, pseudoephedrine, immunosuppressive and psychotropic agents), surgery on the heart or aorta, vasculitis, sickle cell disease, clotting disorders, long-distance running, colonoscopy or barium enema, and idiopathic cases with no clear cause. In younger patients it is often associated with the contraceptive pill, cocaine or methamphetamine use, pseudoephedrine, sickle cell disease and inherited clotting disorders.

The sources used for this guide do not give a long-term diet plan for ischaemic colitis. What they do describe is the hospital treatment: Patient.info says bowel rest is often helpful, and NHS Highland's guidance for suspected mesenteric ischaemia says to keep the patient nil by mouth, which means no food or drink while the bowel is assessed and supported with fluids.

Eating pain is a feature of a related condition rather than ischaemic colitis. Patient.info says that in chronic mesenteric ischaemia, sometimes called intestinal angina, the constant fear of abdominal pain after eating leads to significant weight loss. If you have pain after meals, weight loss or bloody stools, see a GP rather than changing your diet on your own.

Patient.info says the ischaemia may be transient and resolve once the cause of the reduced blood flow has been dealt with, that bowel rest and supportive care are often helpful, and that broad-spectrum antibiotics are recommended. If symptoms do not improve in 24 to 48 hours, repeat colonoscopy or CT angiography is needed to re-evaluate the severity.

Increasing abdominal tenderness with guarding and rebound tenderness, fever, uncontrollable bleeding and paralytic ileus suggest possible infarction of the colon and require urgent laparotomy with removal of the dead part of the colon, according to the same source. NHS Highland's mesenteric ischaemia guidance describes admission under the on-call general surgeon, immediate supportive treatment with oxygen, fluids and pain relief, and keeping the patient nil by mouth, with laparotomy mandatory if there are signs of peritonitis or bowel infarction.

Patient.info states that the diagnosis may be one of exclusion and should always be borne in mind in patients with abdominal pain of unclear cause. Ischaemic colitis is usually diagnosed via an abdominal CT scan, ideally with intravenous contrast. CT angiography should be performed if isolated right colon ischaemia is found, because it may be a precursor of acute mesenteric ischaemia, or if acute mesenteric ischaemia is otherwise suspected.

Colonoscopy may show blue, swollen mucosa not showing contact bleeding and sparing the rectum. Ultrasound can sometimes show it but is operator-dependent. The conditions it can resemble include dysentery, acute diverticular disease, acute inflammatory bowel disease, and perforation or pancreatitis causing left-sided peritonitis. NHS Highland's guidance notes that an early contrast CT scan of the abdomen is essential when mesenteric ischaemia is suspected.

Patient.info classifies bowel ischaemia into three main types. The table summarises what it says about each.

The NHS stomach ache page says to call 999 or go to A&E if a stomach ache came on very suddenly or is severe, hurts when you touch your stomach, your poo is bloody or black, sticky and extremely smelly, you are vomiting blood, you cannot poo or fart, or someone has collapsed. It advises asking for an urgent GP appointment or NHS 111 help if the pain gets much worse, does not go away or keeps coming back, or you bleed from your bottom.

Do not drive yourself to A&E; ask someone to drive you or call 999 for an ambulance, as the NHS advises. Sudden severe abdominal pain with blood in the stool is not something to wait out at home, whatever the cause.

Patient.info says the prognosis depends on the location and extent of the disease, other illnesses, and whether emergency surgery is needed. It reports that severity and overall mortality are higher in right-sided disease, with overall mortality of about 22%. Because many mild cases may go unreported, as Patient.info notes, individual outlook varies widely, and your own team can give you a more specific picture.

Patient.info's list of predisposing factors, which includes heart rhythm problems, some medicines and clotting disorders, shows why teams look for an underlying cause. Ask your team what was found and whether anything needs to change.

Ischaemic colitis is typically diagnosed in hospital after an emergency presentation, so the NHS emergency and surgical pathway is the usual route. NHS Highland's guidance says isolated colon ischaemia is managed by general or colorectal surgery, because vascular reconstruction is not usually feasible.

Follow-up, such as a repeat colonoscopy and a review for an underlying cause, is arranged by the hospital teams who looked after you. Some people ask for a private gastroenterology or colorectal opinion afterwards; the sources used here do not describe private services or costs. Any second opinion will rely on your hospital CT and endoscopy reports, so ask for copies.