Colorectal Services


Endoscopy enables a doctor to directly examine a patient’s GI tract. The endoscope is a flexible tube composed of thin fibres of glass attached to a powerful light source, and it transmits light and images as it goes through the GI tract.

Upper GI Tract

In Upper gastrointestinal tract endoscopy (Oesophago-gastro-duodenoscopy), the doctor examines your oesophagus, stomach and duodenum using an endoscope. Disorders, such as Gastro-oesophageal reflux disease, ulcers, gastritis and cancer can affect the Upper GI Tract. Treatment may sometimes be performed through the endoscope.

Lower GI Tract

In Lower gastrointestinal tract endoscopy (Colonoscopy), the doctor examines your colon and large intestines using an endoscope to evaluate symptoms or screen for colorectal cancer. Disorders such as haemorrhoids (piles), inflammation, polyps, and cancer can affect the Lower GI Tract. Treatment may sometimes be performed through the colonoscope.

Perianal Surgery

Anal abscesses, anal fistulae, haemorroids (piles) and rectal prolapse are common perianal conditions. Although rarely life threatening, these conditions can cause considerable distress and inconvenience.

The best treatment will be recommended for your case. Besides Surgery for anal abscesses, anal fistulae and rectal prolapse, other treatments include:

  • Injection
  • Rubber Band Ligation
  • Conventional Haemorrhoidectomy
  • Stapled Haemorrhoidectomy
  • Transanal Haemorrhoidal Dearterialization (THD)

Colorectal Surgery

Medical conditions affecting the colon and rectum can be broadly categorized into two groups: benign and malignant (cancerous). Depending on the diagnosis, a suitable treatment will be recommended.

Both open technique surgery and minimally invasive surgery are available. For advanced minimally invasive surgery, our team offers single port and robotic assisted surgery, on top of conventional ("key-hole") laparoscopic surgery.


Different colorectal conditions require its own set of management. Depending on the nature and severity of your condition, Dr Ong will advise which methods are the most appropriate to treat or cure the condition. Should you have any concern that you may be suffering from one of the following conditions, do make an appointment with Dr Ong for a consultation.

The colorectal conditions and diseases most commonly diagnosed are Haemorrhoids (Piles), Irritable Bowel Syndrome, Inflammatory Bowel Disease, Diverticular Disease, Colorectal Cancer, Familial Adenomatous Polyposis (FAP), Polyps, and Rectal Prolapse.

Anal Abscess
What is an anal abscess?

It is a cavity found near the anus or rectum that has been infected and filled with pus.

What causes an anal abscess?

It typically results from a severe infection of a small gland, located just inside the anus. This occurs when bacteria or foreign matter enters the tissue through the gland.

How is an anal abscess treated?

A minor operation will drain the pus from the infected cavity. A deep or large abscess may require surgery under general anaesthesia and hospitalisation. The skin opening is left to heal after the operation, and the wound needs to be cleaned daily.

Anal Fistula
What is an anal fistula?

It is a small tunnel under the skin that connects a previously infected anal gland to the skin on the buttocks outside the anus. It is usually the result of a previous abscess.

What causes an anal fistula?

After draining an abscess, a tunnel may persist in connecting the anus or rectum to the skin. Persistent drainage of mucous or pus may suggest the presence of this tunnel.

How is an anal fistula treated?

The surgery normally involves cutting a small section of the anal sphincter muscle to open the tunnel and convert it into a groove that will then heal outwards. If a large section of the muscle is involved, two operations may be required. The surgery can usually be performed on an outpatient basis in the day surgery centre, or with a short hospital stay.

What are the symptoms of an anal abscess or anal fistula?

Constant pain is present, occasionally accompanied by swelling that may not be related to bowel movements. Other symptoms include fever and discharge of pus.

What kind of post-surgery care is needed?

Discomfort may range from mild to moderate in the first week, but this can be controlled with painkillers. The patient may rest at home and visit a family clinic daily to dress the wound initially.

Haemorrhoids (Piles)
What are piles?

Piles (or haemorrhoids) are vascular tissue or 'cushions' located in the anal canal. Their function is to help prevent leakage of stool or gas. Should the piles swell up and/or bleed during defaecation, you need to have a medical check.

4-Grade Classification:

  • First degree: Internal piles that bleed, but do not prolapse past the anus (or 'pop out').
  • Second degree: Piles that prolapse past the anus during bowel movement but reduce spontaneously.
  • Third degree: Piles that are prolapsed and must be manually reduced.
  • Fourth degree: Piles that are permanently prolapsed and cannot be reduced, or piles with painful blood clots.
What are the symptoms?

Symptoms include bleeding before, during or after bowel movement, bright red blood from the anus on the toilet paper or in the toilet bowl, presence of anal lumps, and pain or itching in the anal area.

What causes piles?

When the tissue supporting the cushion-like, clusters of veins stretch and break, the blood vessels enlarge. This causes the vessel walls to thin out and bleed. Further stretching may lead to a prolapse.

Some contributing factors include inadequate fibre in the diet, chronic constipation and excessive straining during bowel movements, spending long periods of time in the toilet (e.g. reading in the toilet), pregnancy, and ageing.

Treatment options

Each procedure differs in length of recovery process, risks and complications, as well as post-operative discomfort. A proper consultation will help you make an informed decision.

How are piles treated?

Mild symptoms can be relieved by improving and regularising bowel habits. This can be done by increasing the amount of fibre and fluid intake in one’s diet, and by eliminating excessive straining during bowel movement to reduce the pressure on piles.

First and second degree piles may be treated with injection treatment or rubber band ligation. Third and fourth degree piles almost always require surgery (e.g. Transanal Haemorrhoidal Dearterialization (THD), conventional haemorrhoidectomy, and stapled haemorrhoidectomy).

How does injection treatment work?

An oily solution is injected onto the top of the piles to cause mild inflammation at the base of the haemorrhoids. When the blood vessels shrink, the size of the piles becomes smaller.

How does rubber band ligation work?

A rubber band is placed around the base of the haemorrhoid inside the anal canal. The band cuts off blood supply to the haemorrhoid which shrivels and falls off in 3-4 days.

How does Transanal Haemorrhoidal Dearterialization (THD) work?

There is no cutting or removal of haemorrhoidal tissue. The surgeon identifies the blood vessels supplying the haemorrhoids with a Doppler Ultrasound, and stitches the appropriate blood vessels. The haemorrhoids shrink when blood supply is limited. The prolapsed tissue can then be further reduced by stitching.

How does Conventional Haemorrhoidectomy work?

A small incision is made to remove the piles. This may be followed by wound closure.

How does Stapled Haemorrhoidectomy work?

A circumferential ring of excess haemorrhoidal tissue is removed. This disrupts the blood supply to the piles, and also lifts them back to their normal position within the anal canal.

Rectal Prolapse
What is rectal prolapse?

It occurs when the rectum drops downwards and turns inside out. The rectum, which is the lower end of the colon located just above the anus, remains inside the body in the early stage. As the condition worsens, it may protrude out through the anus. The anal muscles are often weak, and this may result in leakage of stool or mucous. This condition is more common in women than men.

What causes rectal prolapse?

Possible factors include repeated straining during defaecation and stresses during childbirth. Weakening of the tissue supporting the rectum, weakening of the muscles of the anus and neurological problems (e.g. spinal cord injury or spinal cord disease) can also lead to prolapse.

How successful is surgery for rectal prolapse?

The success of the surgery depends on a few factors, including the type of surgery, the stage of the prolapse, the strength of the anal muscles prior to the operation, and the overall health of the patient. With the appropriate procedure, a large majority of patients experience a positive outcome.

What are polyps?

A polyp is an abnormal growth of tissue rising from the lining of the large intestine and protruding into the intestinal canal. A polyp may be flat or attached to a stalk. Polyps occur in 15-20% of the adult population and are considered one of the most common conditions affecting the colon and rectum.

What are the symptoms?

Most polyps produce no symptoms and are often discovered incidentally. Some polyps can produce bleeding, mucous discharge, change in bowel habits etc.

How can I check for polyps?

The most effective way is to go for colorectal screening with colonoscopy. Other methods include a barium enema, CT colonography, and stool occult blood test.

In colonoscopy, the doctor uses a flexible instrument to look directly at the colon lining to inspect for polyps. The risks of colonoscopy include: colonic perforation (1:1000), bleeding, and infection. For both barium enema and CT Colonography, the doctor examines the colon with the help of X-rays.

Do polyps need to be treated and will they recur?

There is no foolproof way of predicting the malignant potential of a polyp. As such, complete removal of all polyps is advised. Small polyps can be removed during colonoscopy, while larger polyps may require surgery.

Once a polyp is completely removed, its recurrence is rare. However, new polyps will develop in at least 30% of patients with a history of polyps. Regular colonoscopy is recommended.

Familial Adenomatous Polyposis (FAP)
What is Familial Adenomatous Polyposis (FAP)?

FAP is a genetic condition in which numerous polyps form in the colon. It occurs when the individual's FAP gene (on chromosome 5) is faulty. If left untreated, it will eventually develop into cancer when the patient is in his 20s.

What are the symptoms?

In the early stages, there may be no symptoms. As this is an inherited condition, should you have a family member previously diagnosed with FAP, you should arrange for a check-up immediately.

Can we rely on blood tests?

If someone in the family has FAP, and the 'faulty spot' has already been identified, a blood test can be done to check if the individual also has FAP. However, this test does not work for everyone at the moment.

How is FAP treated?

As the patient would have too many polyps for removal via endoscopy, the only effective treatment is to remove the entire colon with surgery. After recovery, most patients go on to lead normal and functional lives.

Colorectal Cancer
What is colorectal cancer?

It is cancer that starts in the large intestine (colon) or the rectum (end of the colon), developing from the cells lining the colon/rectum. It is one of the most common cancer amongst males and females in Singapore.

Colorectal cancer can cause blockages in the colon, and may cause bleeding (observed in the stools). If diagnosed early enough, 80-90% of patients are restored to health.

Am I at risk?

Colorectal cancer may occur at any age. Other high risk factors include: a family history of polyps and colorectal cancer, especially so if the family member is young; a personal history of ulcerative colitis, colonic polyps or cancer(s) of other organs (especially of the breast or uterus). Your lifetime risk for developing colorectal cancer without any other risk factors is 1 in 50.

Can we rely on blood tests?


What are the symptoms?

None or very few symptoms may be observed. The most common symptoms of colorectal cancer are rectal bleeding and a change in bowel habits (e.g. persistent constipation or diarrhoea, change in frequency of stools). Abdominal discomfort or pain and weight loss are usually late symptoms indicating possible extensive disease. It is important to undergo a thorough examination to diagnose even benign conditions.

How is colorectal cancer treated?

Nearly all cases require surgery for complete cure. Chemotherapy and radiotherapy are sometimes used. Colostomy, an artificial opening in the abdominal wall, is occasionally required.

Can colorectal cancer be prevented?

Removing benign polyps is an effective method to prevent progression to cancer. Having a colonoscopy and removing polyps is a safe procedure that can be done on an outpatient basis, with or without sedation.

A healthy diet, being aware of changes in your bowel habits, and undergoing a thorough examination if you belong to a ‘high risk’ group are also other ways to prevent colorectal cancer.

Diverticular Disease
What is diverticulosis and diverticulitis?

Diverticulosis is a condition when pockets develop in the colon, out-pouching through the weak muscle layers in the colon wall. This condition affects around 19% of Singaporeans above the age of 14.

Usually no symptoms are observed, and very few people require surgery. Complications that can occur with diverticulosis include infection (diverticulitis) and bleeding (diverticular disease).

What are the symptoms?


Often, no symptoms are experienced although some people may have cramps or discomfort in the lower left abdomen, bloating, and changes in bowel habits (diarrhoea and constipation). However, these symptoms are similar to those of irritable bowel syndrome, stomach ulcers and colorectal cancer so it is best to go for a check-up.


When the pockets in the colon are inflamed, the most common symptom is abdominal pain. The most common sign on examination is tenderness in the abdomen. The intensity of the pain can fluctuate over several days. A person may also experience cramping, nausea, vomiting, fever, and chills.

Diverticular bleeding

Should you experience sudden and massive bleeding from the rectum, hospital admission is compulsory for monitoring and possibly blood transfusions. Some patients may require surgical or radiological intervention to stop the bleeding. A life-threatening bleed may result in heart attacks, strokes or even death.

What are the complications of diverticulitis?

If not treated, intra-abdominal infection, abscesses, fistula formation and colon obstruction may occur. The sufferer may experience nausea, vomiting, fever, chills, and severe abdominal pain. Surgery may be required for severe cases.

How is diverticular disease treated?

For diverticulitis, treatment includes oral antibiotics, dietary restrictions, bed rest, and pain relief for mild cases. If hospitalized, treatment may involve intravenous antibiotics and strict dietary restraints to help the colon rest. In some cases, surgery may be necessary.

Inflammatory Bowel Disease
What is inflammatory bowel disease (IBD)?

It is a group of inflammatory conditions that affect the colon and small intestines. Sometimes referred to as idiopathic IBD, the cause of the disease is still unknown.

Crohn's disease and Ulcerative colitis

Crohn's disease affects any part of the gastrointestinal (GI) tract, whereas Ulcerative colitis (UC) affects the large intestines.

Inflammation occurs on the lining of the intestines (mucosa), and open sores may result on the surface. The ulcers may produce excessive amounts of mucus with pus, and the intestinal lining may bleed. Managing IBD is complex as it is possible to be in remission for long periods, yet suffer a relapse at any time.

What are the symptoms of IBD?

Common symptoms include diarrhoea, bloody stools and passage of mucus with stools. Other symptoms include fever, weight loss, abdominal pain, cramps, bloating, anal pain or drainage, skin lesions, rectal abscess, fissure, and joint pain (arthritis).

How is IBD treated?

There is no known cure as the cause of the disease is unclear. Treatment aims to reduce activity of the disease, and minimize relapses.

Patients have to medicate for life to control and manage the symptoms. Medication may be taken by mouth, injected directly into the veins, or applied directly into the intestines through the anus. The most regularly used medicines are steroids (e.g. prednisolone) and various anti-inflammatory agents. Stronger drugs (e.g. 6-mercaptopurine, azathioprine) may be used in more severe cases, but these do cause more side effects and suppress the immune system.

Surgery may be recommended in more complicated cases of IBD. Emergency surgery may be required when complications (e.g. obstruction of the bowel, perforation of the intestine, or massive bleeding) occur with IBD.

Operations may also be required patients who do not respond to medication, have abscess formation, have fistulas, and/or have severe anal disease.

Is surgery really necessary?

Medication is always the preferred method of treatment. However, up to 75% of patients may require surgery eventually. Surgery may offer relief of symptoms in the long-term, and decreases the reliance on medication.

Irritable Bowel Syndrome
What is Irritable Bowel Syndrome (IBS)?

It is a common disorder of the large intestines that may cause pain, bloating and changes in bowel habits. It mainly interferes with the normal functions of the large intestine (colon). About 20% of the population suffer from this non-threatening disorder.

What are the symptoms of IBS?

Abdominal pain, bloating, and discomfort are the main symptoms of IBS. Other symptoms are diarrhoea, constipation and/or both. For some, their symptoms subside after a few months and then return, while others experience a constant worsening of symptoms over time. The symptoms may worsen when one is stressed, has been ill, or has irregular meals.

What causes IBS?

To date, there is no known organic cause for IBS. However, scientific research has shown that individuals with IBS seem to have more sensitive and reactive colons compared to other people. Generally, women are more susceptible to IBS than men.

How is IBS diagnosed?

IBS is a diagnosis of exclusion, generally diagnosed on the basis of a complete medical history that includes a careful evaluation of symptoms and a physical examination. Diagnostic tests such as blood tests or x-rays may be required to ensure that your symptoms are not caused by something other than IBS. A colonoscopy is necessary.

How is IBS treated?

To alleviate the symptoms of IBS, the following are recommended:

  • Change to a Low fat, High fibre diet. Keep a food diary to note the foods that seem to worsen your condition, and try to avoid them.
  • Take small meals. Eat smaller portions more frequently or decrease the quantity of food intake.
  • Take medication to relieve symptoms. These may include fibre supplements, probiotics, laxatives for constipation or medicine to decrease diarrhoea and to relieve or reduce pain.
  • Reduce stress and anxiety. Seek out counseling and support, train yourself to relax or have adequate sleep for better mental health.
  • Go for Clinical Hypnotherapy. Learn how to influence and gain control of your gut function, thereby changing the way the brain modulates gut activity.
Is IBS all in the mind?

Studies have shown that patients with IBS are 50-60% more likely to experience anxiety and mood disorders as compared to other people. However, this should not be taken to mean that IBS is caused by psychiatric illness or vice versa.

Interestingly, there is a strong link between the gut and the brain as both organs use many of the same chemical messengers. With this in mind, it is easy to see how a disturbance in function of one is able to cause symptoms in the other.

Will IBS develop into other health problems?

No, IBS will not cause permanent harm to the intestines nor lead to serious diseases such as cancer.