Acute Appendicitis

What is appendicitis?

Appendicitis is an inflammation of the appendix, a small, finger-shaped pouch attached to the large intestine in the lower right side of the abdomen. It is one of the most common surgical emergencies worldwide.

The condition usually develops when the opening of the appendix becomes blocked, allowing bacteria to multiply inside. This leads to swelling, infection and a build-up of pus. If left untreated, the appendix can burst (rupture), spreading infection within the abdomen and causing serious, potentially life-threatening complications such as peritonitis or abscess formation.

Appendicitis can occur at any age but is most common in teenagers and young adults. With early diagnosis and prompt treatment, most patients recover quickly and without long-term problems.

Acute vs. chronic appendicitis

• Acute appendicitis — this is the sudden and severe form, where symptoms such as abdominal pain, nausea and fever develop quickly. It requires urgent treatment, usually surgical removal of the appendix.

• Chronic appendicitis — much less common, this form causes milder, recurring abdominal pain over weeks or months. Symptoms are less specific, which often delays diagnosis. Treatment is also surgical removal, though it is less urgent than in acute cases.

What causes acute appendicitis?

Acute appendicitis occurs when the narrow opening of the appendix becomes blocked. This blockage leads to bacterial overgrowth, swelling and infection inside the appendix. Several different factors can cause this:

• Hard stool (faecoliths) — a faecolith is a small, hardened lump of stool that can lodge in the appendix opening. This is one of the most common causes. Once the passage is blocked, bacteria multiply rapidly, leading to inflammation and pus formation.

• Swollen lymph tissue — the appendix contains lymphoid tissue, which helps the body fight infections. After a viral or bacterial illness, this tissue can become enlarged and block the appendix, setting the stage for appendicitis.

• Parasites or foreign bodies — in some cases, intestinal worms (such as Enterobius vermicularis, also known as pinworm) or rarely swallowed foreign objects can obstruct the appendix. Although uncommon, these can trigger the same cascade of infection and inflammation.

• Tumours — very rarely, tumours in the appendix or nearby bowel can block the appendix opening. This is seen more often in older adults and may present with symptoms similar to appendicitis.

Once blocked, the appendix swells and becomes infected. Without treatment, the pressure inside builds up until the appendix may burst, spreading infection into the abdominal cavity.

What are the signs and symptoms of acute appendicitis?

The hallmark symptom of acute appendicitis is abdominal pain, but the way this pain develops can help distinguish it from other conditions. Classically, the pain starts near the belly button (periumbilical area) and then shifts to the lower right side of the abdomen, where the appendix is located. The pain often worsens with movement, coughing, or deep breathing.

Other common signs and symptoms include:

• Pain in the lower right side of the abdomen (right lower quadrant)

• Loss of appetite
• Nausea and vomiting
• Low-grade fever
• Tenderness and guarding when the right lower abdomen is pressed
• Constipation or diarrhoea in some cases
• A general feeling of being unwell (malaise)

Less common symptoms may include urinary frequency or discomfort if the inflamed appendix irritates the bladder.

Symptoms are not always straightforward. Children, older adults, and pregnant women may present atypically, with milder or less localised pain, which can delay diagnosis. Because appendicitis can mimic other conditions such as gastroenteritis, urinary tract infection or gynaecological problems, any persistent or severe abdominal pain should be assessed promptly by a doctor.

Who is at risk of acute appendicitis in Singapore?

Acute appendicitis can occur at any age, but certain groups are more likely to develop it:

• Age — it is most common in teenagers and young adults, though it can also affect children and older adults.

• Sex — slightly more common in males than females.

• Family history — having close relatives with appendicitis may increase the likelihood.

• Infections — recent gastrointestinal infections can sometimes trigger swelling of lymph tissue in the appendix, leading to blockage.

• Lifestyle and diet — diets very low in fibre and high in processed foods may play a role in increasing the risk, although evidence is not conclusive.

While appendicitis can happen to anyone, being aware of these risk factors can help with early recognition and timely medical attention.

What are the complications of acute appendicitis?

If acute appendicitis is not treated promptly, the inflamed appendix can rupture, releasing pus and bacteria into the abdominal cavity. This can lead to serious and potentially life-threatening complications:

• Perforation (ruptured appendix) — when the appendix bursts, infection spreads within the abdomen. This is the most feared complication and can occur within 24 to 72 hours from the onset of symptoms.

• Peritonitis — rupture can cause infection of the lining of the abdomen (peritoneum), leading to severe pain, fever and widespread illness that requires emergency treatment.

• Abscess formation — sometimes the infection becomes walled off, forming a pocket of pus inside the abdomen. Abscesses often require drainage as well as antibiotics.

• Sepsis — if bacteria enter the bloodstream, widespread infection can occur. This can progress to septic shock, where blood pressure drops dangerously low and organs begin to fail.

Prompt surgery and antibiotics significantly reduce the risk of these complications. Early recognition of appendicitis is therefore vital to prevent serious outcomes.

How is acute appendicitis diagnosed?

Because acute appendicitis can progress rapidly to serious complications, timely diagnosis is essential. Doctors usually start with a clinical assessment and then use tests such as imaging and blood work to confirm the diagnosis.

• Physical examination — your doctor will ask about the onset, location and nature of your pain, as well as any associated symptoms such as nausea, fever or loss of appetite. They will examine your abdomen for tenderness, swelling or guarding, often pressing on the lower right side to see if this reproduces pain (a classic sign of appendicitis).

• Imaging tests — these help confirm the diagnosis and rule out other causes of abdominal pain.

• CT scan — abdominal CT is the most accurate test for appendicitis in adults, showing inflammation, thickening of the appendix or an appendicolith (a hardened mass blocking the appendix). Contrast may be used to improve visibility.

• Ultrasound — often the first choice in children and pregnant women, as it avoids radiation. It can show an enlarged appendix or local fluid collection.

• MRI — very sensitive and specific, and particularly useful in pregnant women or patients where radiation exposure should be avoided. However, it is less widely available and not routinely used as a first-line test.

• Blood tests — blood work is used to detect signs of infection or inflammation. A raised white blood cell count and elevated C-reactive protein (CRP) are common in appendicitis. These results, together with clinical findings, can help doctors decide whether the case is complicated (with higher risk of perforation) or uncomplicated.

In some cases, if results remain inconclusive but suspicion of appendicitis is high, surgery may still be recommended to prevent rupture and further complications.

What are the treatment options for acute appendicitis? 

The standard treatment for acute appendicitis is surgical removal of the appendix, known as an appendicectomy. This prevents rupture and eliminates the source of infection. In most cases, surgery is straightforward and recovery is quick.

• Appendicectomy — this is the most common and definitive treatment. It can be performed through:

• Laparoscopic (keyhole) surgery — small incisions are made in the abdomen, and the appendix is removed using a camera and specialised instruments. This method is associated with less pain, shorter hospital stays and faster recovery.

• Open surgery — a single incision is made in the lower right abdomen to remove the appendix. This approach is usually reserved for complicated cases, such as when the appendix has ruptured or when infection has spread widely.

• Antibiotics — antibiotics are often given before and after surgery to reduce infection risk. In selected cases of uncomplicated appendicitis, especially in patients unfit for surgery, a course of antibiotics alone may be used, although recurrence is possible.

• Drainage of abscesses — if an abscess has already formed, it may be drained with the help of imaging guidance before surgery is performed. This helps control infection and reduces the risk of complications.

With timely treatment, most patients recover well and return to normal activities within a few weeks. Delay in treatment increases the risk of rupture, peritonitis, and more complex surgery.

Summary 

Acute appendicitis is a common but potentially dangerous condition where the appendix becomes inflamed, usually due to a blockage and infection. It most often presents as sudden abdominal pain, which may start near the belly button and shift to the lower right side, accompanied by nausea, loss of appetite, and fever. If left untreated, the appendix can rupture, leading to life-threatening complications such as peritonitis or sepsis. 

Acute appendicitis requires urgent treatment, usually surgical removal of the appendix, while chronic appendicitis is rare and tends to cause milder, recurring symptoms. With timely diagnosis and treatment, most patients recover quickly and fully.

If you are experiencing persistent or severe abdominal pain, schedule a consultation with Tan Siong Siong Surgery for expert diagnosis and safe, effective treatment of appendicitis.