Subacute Appendicitis: Symptoms, Causes, Diagnosis, Radiology and Treatment Options

Have you just got a USG report saying you have subacute appendicitis? Well, you are probably panicking already and your situation is completely understandable.

This is a form of appendicitis in which the appendix remains inflamed for a longer amount of time than acute appendicitis. Because the symptoms are not as severe or as rapid as those observed in acute appendicitis, this illness can be difficult to identify.

It should not be ignored at all since it might develop into difficulties if left untreated. We will look at the symptoms, causes, diagnostic tests, and treatment options for subacute appendicitis in this post to help you obtain a thorough understanding of the problem.

What is Subacute Appendicitis?

In simpler meaning, it is a kind of appendicitis that occurs over time rather than immediately.

It is a more progressive process marked by mild to moderate pain in the lower right side of the abdomen, as opposed to acute appendicitis, which is a rapid and severe disease.

Most often, people have mild pain in their right lower abdomen and seek medical care where a USG reveals the diagnosis. There is no need to panic if you have seen a doctor already. A clear-cut diagnosis often helps with appropriate management.

Is Subacute Appendicitis serious?

While Acute Appendicitis is a surgical emergency that needs to be operated on as soon as possible, the Subacute type can be managed with antibiotics and conservative efforts. This depends on the severity of the symptoms.

The symptoms might be vague and difficult to identify, making the diagnosis challenging. Furthermore, pain may be less severe and more intermittent than pain from the acute type.

As a result, people may postpone obtaining medical assistance, increasing their risk of complications.

Here is a video that will help you grasp the concepts quickly:

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Subacute Appendicitis vs Acute Appendicitis

The difference between the two has been summarised in the table below:

Subacute AppendicitisAcute Appendicitis
The onset of symptoms is gradual and may last for several days or weeksThe onset of symptoms is sudden and severe
Symptoms may be milder and less specificSymptoms are severe and specific
Inflammation is less severe and the appendix may not be as tender to the touchInflammation is severe and the appendix is highly tender to the touch
Pain is often located in the lower right abdomen and may come and goPain is located in the lower right abdomen and is constant
Elevated white blood cell count may not be as noticeableElevated white blood cell count is noticeable
Diagnosis may be more difficult and may involve additional testingDiagnosis is typically straightforward based on symptoms and physical examination
Antibiotics may be used to treat the infection before or after surgerySurgery is typically required to remove the infected appendix
Subacute vs Acute Appendicitis

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The 5 Signs that you might be having appendicitis are:

  1. Abdominal Pain: Pain in the lower right side of the abdomen is the most common sign of subacute appendicitis. The pain might be subtle or intense, and it could be accompanied by a sense of heaviness or tightness. An absence of bowel sounds can mean rupture.
  2. Nausea and vomiting: These are two usual symptoms that could arise while the body attempts to expel toxic chemicals from the appendix.
  3. Appetite Loss: People may have a loss of appetite and may not feel like eating.
  4. Fever: It is another typical sign indicating that the body is combating an infection in the appendix.
  5. Constipation or diarrhea: They may develop if the appendix inflammation disrupts the natural passage of fluid and waste particles in the intestines.


The 5 most common causes of subacute appendicitis are:

  1. Infection: A bacterial infection, such as a urinary tract infection, that travels to the appendix is one of the most prevalent causes.
  2. Blockage: Obstruction in the appendix, such as a fecal impaction, which prevents normal fluid and waste passage.
  3. Chronic illnesses: Conditions such as Crohn’s disease or ulcerative colitis, can weaken the appendix walls and therefore, raise the risk.
  4. Genetics: Some persons may be genetically predisposed.
  5. Age: The risk increases with age.

Additionally, poor nutrition, lack of physical exercise, and smoking are some of the contributing factors to the disease.

What food can cause appendicitis?

There is no recognized diet that causes appendicitis. However, some meals which lead to conditions like constipation can contribute to the development of circumstances that raise the risk.

A diet low in fiber, rich in fat, and poor in fruits and vegetables can contribute to constipation and raise the risk of fecal impaction, which can lead to the disease itself.

In general, a fiber-rich diet rich in fruits, vegetables, and whole grains can help minimize the incidence. Drinking plenty of fluids and keeping physically active can also help avoid constipation and lower the risk.

Can stress cause appendicitis?

Stress is not regarded to be the main reason for appendicitis. On the contrary, it might weaken the immune system and make it more susceptible to diseases.

Long-term stress can lead to sleep deprivation, poor nutrition, and physical inactivity. All of these variables lead to the development of related disorders such as constipation.

Furthermore, stress can cause muscle tension and stomach discomfort, which might mimic the symptoms of subacute appendicitis. This might make detecting the illness in stressed persons more difficult.


The diagnosis is made clinically followed by confirmation from radiology. Alvarado score is often used to calculate the probability of acute appendicitis. However, USG and CT are the best modalities to confirm it.

Blood tests such as CBC (WBC count), ESR, and other inflammatory markers also help in establishing the diagnosis. Routing testing also involves urinalysis and stool tests.

It is noteworthy that appendicitis is not routinely diagnosed with X-rays but with USG or CT. An xray is ineffective in detecting the appendix and does not give the amount of details required to reliably diagnose the disease.


The two most commonly used radiological investigations performed are:


It is first important to know the normal appendix size on ultrasound. This is considered to be less than 6 mm. A size of 7mm or more on the USG report is considered dangerous and should be considered for surgery.

On the other note, the 9 USG findings of appendicitis usually written on the report are:

  1. Appendix enlargement: Due to the inflammation and swelling, the appendix may seem bigger than normal (more than 6mm).
  2. Thickening of Wall: More than 3mm of the thickened appendix ion USG or CT is significant for diagnosis.
  3. Accumulation of Fluid: An ultrasound may reveal fluid collection around the appendix, indicating that it has gotten infected and is leaking fluid.
  4. Abscess formation: A collection of pus in the region around the appendix.
  5. Peri-appendiceal fat infiltration: Infiltration of surrounding fat tissue, indicating inflammation and infection.
  6. Anechoic area: This means a black region in the interior of an inflamed appendix due to the buildup of fluid.
  7. Lymph node enlargement: Lymphadenopathy can be observed due to infection.
  8. Surrounding structures inflammation: This can be seen with mesentery usually. Other structures involved are the small intestine and caecum.
  9. Free fluid in the abdominal cavity: This indicates rupture of the appendix and should be managed immediately or it can lead to fatal consequences.


The CT criteria are similar to USG findings, however, the preciseness and sensitivity (up to 98%) are significantly higher for appendicitis. This is usually CECT Abdomen (CT scan with contrast enhancement).


Subacute appendicitis can be treated with antibiotics and conservative measures without the need for surgery. However, this decision depends on the treating surgeon.

Antibiotics are generally given for 7-14 days in mild appendicitis before they can start working. It can take longer to heal if the case is complicated. IV route is preferred in cases of admitted patients.

Surgery is performed when there is urgency such as rupture or high chances of shifting to acute type.

Out of all the 3 types of appendicitis, only the Subacute variant can be managed with antibiotics which include:

  1. Metronidazole
  2. Ciprofloxacin
  3. Clindamycin
  4. Amoxicillin
  5. Azithromycin

Out of the 5 mentioned above, Metronidazole and Ciprofloxacin are widely used in India for the management of subacute appendicitis.


What are the 4 stages of Appendicitis?

These are:

1. Early Stage: The first stage is distinguished by minor abdominal discomfort, bloating, and a sense of fullness. Passing gas or having a bowel movement may help to ease the discomfort.

2 Acute Stage: The pain grows more intense and is localized in the lower right side of the abdomen during this stage. Additionally, the individual may have nausea, vomiting, and a low-grade temperature.

3. Gangrenous Stage: The appendix becomes infected and the blood flow to the appendix is blocked during the gangrenous stage. This can result in gangrene, which is the death of tissue owing to a lack of blood supply.

4. Perforated Stage: Throughout this stage, the inflamed appendix explodes, causing an accumulation of bacteria and other hazardous substances in the abdominal cavity. This can lead to major complications such as peritonitis (inflammation of the lining of the abdominal cavity) and sepsis (a life-threatening infection that spreads throughout the body).

What are the three types of appendicitis?

1. Acute appendicitis: This is the most common type defined by immediate abdominal pain, a low-grade temperature, nausea, and vomiting. It occurs when the appendix gets infected and enlarged, necessitating quick medical attention and treatment.

2. Chronic appendicitis: It causes mild to severe stomach pain and discomfort when the appendix becomes inflamed and infected on a regular basis. It can develop gradually and without presenting obvious symptoms.

3. Subacute appendicitis: This variety causes moderate stomach pain and discomfort over a period of days to weeks. A multitude of causes can induce subacute appendicitis, including bacteria and other infections, foreign objects in the appendix, and prolonged constipation.

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