Intestinal obstruction happens when food, fluid, gas or stool cannot move normally through part of the bowel. Doctors may also call it a bowel obstruction or bowel blockage.

A blockage can affect the small intestine or large bowel. It can be partial or complete. Causes range from scar tissue after surgery and hernias to inflammatory disease, twisting of the bowel and cancer.

Possible bowel obstruction needs urgent medical assessment

Seek urgent medical help if you develop severe or worsening abdominal pain, repeated vomiting, marked abdominal swelling, or you cannot pass stool or wind.

A complete obstruction can become dangerous because the bowel may lose its blood supply, perforate or cause serious dehydration and infection. Do not try to treat suspected obstruction yourself with laxatives, enemas or colon hydrotherapy.

What is an intestinal obstruction?

The digestive tract normally moves its contents forward through coordinated muscular contractions. A mechanical obstruction physically blocks this movement. In other situations, the bowel may stop moving properly even when no physical object blocks it.

Doctors first need to establish whether the obstruction affects the small or large bowel, whether it is partial or complete, and what has caused it. These factors determine how urgently the condition needs treatment and which treatment is appropriate.

Medical literature describes intestinal obstruction as an important surgical emergency because delayed assessment can increase the risk of bowel ischaemia, perforation and other complications.

PubMed: small bowel obstruction and imaging

Symptoms of intestinal obstruction

Symptoms vary according to the position and severity of the blockage. A partial obstruction may behave differently from a complete obstruction.

Cramping or colicky abdominal pain that may come in waves.
Abdominal bloating or swelling.
Nausea and vomiting.
Constipation.
Difficulty or inability to pass wind.
Feeling unusually full.
Changes in bowel sounds or movement.

A person with a partial obstruction may sometimes still pass some stool or gas. Therefore, having a bowel movement does not automatically exclude a partial blockage.

NHS hospital guidance advises urgent medical assessment when symptoms suggest a bowel obstruction. See the Dudley Group NHS Foundation Trust guidance on bowel obstruction.

What causes intestinal obstruction?

The causes of intestinal obstruction differ between the small intestine and large bowel. They also vary according to age, previous abdominal surgery and medical history.

Adhesions after abdominal surgery

Adhesions are bands of scar tissue that can form after abdominal or pelvic surgery. They can pull, kink or trap the small bowel and are an important cause of small bowel obstruction.

Hernias

A section of bowel can become trapped within a hernia. In some cases this can also affect the blood supply to the bowel, which makes urgent assessment particularly important.

Cancer and tumours

A tumour can narrow the bowel until its contents can no longer pass normally. Cancer is particularly important as a cause of large bowel obstruction.

Inflammation and narrowing

Inflammatory bowel disease and other conditions can sometimes lead to narrowing, also called a stricture. This may restrict movement through the bowel.

Twisting of the bowel

A section of bowel can sometimes twist around itself. Doctors call this a volvulus. The twist may obstruct the bowel and can also threaten its blood supply.

Small bowel obstruction and large bowel obstruction

Small bowel obstruction affects the small intestine. Adhesions after surgery and hernias are important causes, although tumours and inflammatory disease can also cause a blockage.

Large bowel obstruction affects the colon or rectum. Cancer, strictures and twisting of the colon are among the causes doctors investigate.

The location matters because symptoms, imaging findings and treatment options can differ.

Bowel obstruction and cancer

A bowel obstruction from cancer can occur when a tumour grows into or around the bowel and narrows its internal passage. Bowel cancer itself can cause a blockage, while other abdominal cancers can sometimes obstruct the bowel directly or through spread within the abdomen.

A bowel cancer obstruction may be the problem that leads to diagnosis, or it may occur later in someone already receiving treatment for cancer.

Cancer Research UK lists bloating, sickness or vomiting, constipation, inability to pass wind and pain among symptoms associated with bowel obstruction in people with metastatic bowel cancer. See Cancer Research UK guidance on treating symptoms of metastatic bowel cancer.

Can bowel cancer cause complete obstruction?

Yes. A colorectal tumour can sometimes narrow the bowel enough to produce an acute large bowel obstruction. This requires hospital assessment and may need a stent, surgery or another treatment depending on the exact situation.

NICE recommends considering a stent for acute left-sided large bowel obstruction when treatment is palliative. When potentially curative treatment is suitable, NICE recommends offering either stenting or emergency surgery. See the NICE colorectal cancer recommendations.

How doctors diagnose intestinal obstruction

Doctors assess the symptoms, examine the abdomen and review previous operations and medical conditions. They may also check for dehydration, abdominal tenderness or signs that the bowel has become compromised.

Hospital investigations can include blood tests and abdominal imaging. CT is particularly useful because it can help identify the level and cause of a blockage and look for complications such as bowel ischaemia or perforation.

A Royal Marsden NHS Foundation Trust patient leaflet on bowel obstruction in people with gynaecological cancer describes blood tests, an abdominal X-ray and, in some cases, CT as investigations used when obstruction is suspected. See its patient information on bowel obstruction.

How is intestinal obstruction treated?

Treatment depends on the cause, location and severity of the obstruction and on the person’s overall condition.

Hospital care may initially include bowel rest, intravenous fluids, pain relief and anti-sickness treatment. If vomiting or abdominal distension is significant, doctors may sometimes use a nasogastric tube to drain fluid and air from the stomach.

Some obstructions resolve without an operation. Others require surgery because the blockage cannot safely resolve on its own or because the bowel’s blood supply is at risk.

Treatment may include removing the cause of the obstruction, freeing adhesions, removing a damaged or obstructed section of bowel, forming a stoma or inserting a stent in selected cases.

Colonic stents for cancer-related bowel obstruction

A self-expanding metal stent can hold open a narrowed section of colon so bowel contents can pass through it.

For some people with cancer, a stent can relieve the obstruction without immediate major surgery. In other circumstances, doctors can use it as a bridge to a later planned operation.

However, stenting is not suitable for every patient. It can fail technically and carries risks, including perforation. NICE therefore recommends that clinicians choose between stenting and emergency surgery according to the treatment aim and individual circumstances.

Peer-reviewed research also continues to evaluate surgery, decompression, stenting and other approaches to malignant colonic obstruction.

NICE colorectal cancer guidance

PubMed: obstructed colon cancer review

Can laxatives help a bowel obstruction?

Do not assume that constipation caused by a bowel obstruction should be treated like ordinary constipation.

The NHS states that bisacodyl is not suitable for people who have a blockage in the bowel. Royal Marsden guidance also notes that laxatives would not normally be given during acute bowel obstruction because they may cause harm.

See the NHS guidance on who can and cannot take bisacodyl.

If you have severe abdominal pain, vomiting, marked swelling or cannot pass stool or wind, seek medical assessment instead of taking additional laxatives.

Possible complications

A severe obstruction can lead to dehydration and electrolyte disturbance. If pressure compromises the blood supply to the bowel, tissue can become damaged. Perforation can allow bowel contents to leak into the abdomen and cause a serious infection.

This is why rapidly worsening symptoms or signs of complete obstruction should not be managed as routine constipation.

When bowel obstruction is linked to bowel cancer

If tests identify colorectal cancer as the cause, treatment planning goes beyond relieving the immediate blockage. The specialist team also assesses the cancer itself and decides whether further surgery, chemotherapy, radiotherapy, targeted medicines or immunotherapy may be appropriate.

Read our guide to bowel cancer treatment.

Read about stage 4 and metastatic bowel cancer.

Read about bowel cancer symptoms and warning signs.

Learn about FIT, colonoscopy, blood tests, biopsy and scans used to investigate bowel cancer.

Colon hydrotherapy and bowel obstruction

Colon hydrotherapy must not be used to treat or attempt to clear a suspected bowel obstruction.

If you have symptoms that could indicate obstruction — particularly abdominal swelling, significant pain, vomiting or inability to pass stool or wind — medical assessment takes priority.

At Parkland Natural Health in Holborn, bowel obstruction is treated as a contraindication to colon hydrotherapy. Our consultation and suitability screening are designed to identify medical circumstances in which we should not proceed with treatment.

If you previously had a bowel obstruction, surgery or another significant bowel condition, please tell us before booking. We may ask you to obtain advice or clearance from your medical team before considering colon hydrotherapy.

Frequently asked questions about intestinal obstruction

Can you still pass stool with an intestinal obstruction?

Sometimes. A partial obstruction may still allow some stool or gas to pass. A complete obstruction is more likely to stop stool and wind completely.

Can bowel obstruction cause vomiting?

Yes. Nausea and vomiting are recognised symptoms of bowel obstruction, particularly when the blockage prevents intestinal contents from moving forward normally.

Can bowel cancer cause an obstruction?

Yes. A tumour in the colon or rectum can narrow the bowel and cause a partial or complete blockage. Cancer-related obstruction may require stenting, surgery or another specialist treatment.

Is bowel obstruction an emergency?

It can be. Complete obstruction, severe pain, persistent vomiting or signs that the bowel’s blood supply is affected require urgent medical assessment.

Can colon hydrotherapy clear an intestinal obstruction?

No. Colon hydrotherapy is not a treatment for intestinal obstruction and should not be performed when an obstruction is suspected or present.

Trusted medical and scientific sources

Medical information notice: This article provides general educational information and does not diagnose intestinal obstruction. Suspected bowel obstruction requires medical assessment. If symptoms are severe or rapidly worsening, seek urgent medical care.

Intestinal Obstruction: Symptoms, Causes and Treatment