Antibiotics For Diverticulitis

  • Jason Ha Bachelor of Medicine, Bachelor of Surgery - MBBS, University of Bristol

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Diverticulitis is a condition characterised by small pouches developing in the lining of the bowel, which then become inflamed, and on occasion infected.1 In this article, we will delve into the causes, symptoms, and management of diverticulitis, with a particular emphasis on antibiotic therapies available for treatment.

Understanding diverticulitis

Whilst the exact cause of diverticulitis is still unknown, it is speculated that it is due to a state of chronic low-level inflammation inside your body. Lifestyle factors such as obesity, a Western/low-fibre diet, and smoking are all known risk factors for diverticulitis, alongside certain connective tissue disorders like Ehlers-Danlos syndrome.2 

Symptom-wise, diverticulitis can cause lower abdominal pain, constipation, nausea, and vomiting. If left untreated, complications such as complete bowel obstruction, internal bleeding, abscess formation, and rupture of the bowel could develop.3 In the most severe cases, these complications can be life-threatening, requiring hospital admission and necessitating potential surgical intervention. This could include surgical drainage of an abscess, laparoscopic lavage (washing the abdominal cavity and colon with keyhole surgery), or Hartmann’s procedure (where the affected bowel is removed and an end stoma is formed). 

Role of antibiotics in diverticulitis

Antibiotics work by targeting and killing bacteria (bactericidal) or by preventing them from replicating and growing in number (bacteriostatic). These effects help minimise the spread of the bacteria and thus can work wonders in diverticulitis when there is a confirmed infection present.

The usage of antibiotics in treatment depends on the severity of the diverticulitis, which is categorised according to the Hinchey classification.4

Uncomplicated diverticulitis refers to a milder condition where the symptoms are mostly localised to a single area of the bowel, often without any infection. Thus, in this scenario, it can be possible to successfully treat it without the use of any antibiotics.5

However, in more complicated cases of diverticulitis, there are more severe complications such as abscess formation or perforation. These can lead to the accumulation of stagnant digesting food and bacteria, which can lead to the development of infection. In the most severe cases requiring hospitalisation, IV fluids, antibiotics, and surgical intervention.6

Before starting any antibiotic, it is essential to confirm the diagnosis. In addition to taking a thorough medical history and conducting a physical examination, doctors can utilise a variety of investigations to diagnose diverticulitis. These include blood tests to look for inflammatory markers, a stool sample to check for bacterial growth, and ultrasound scans. However, the gold standard for diagnosis is via imaging with an abdominal CT scan.7

Once a diagnosis and presence of infection are confirmed, antibiotic therapy can then be initiated, usually ranging from a minimum of 5 days for simpler infections to several weeks depending on the severity of the infection.

Antibiotics in action

Many classes of antibiotics can be used, the choice of which can be tailored depending on the underlying organism causing the infection. Ideally, obtaining a sample would allow us to determine which species of bacteria that is growing. Certain pathogens are sensitive to specific antibiotics; thus, we can tailor the treatment by choosing the best antibiotic. Every hospital will have local trust guidelines that recommend the best antibiotics depending on common bacteria found in the local patient population that the hospital serves.

As a general principle in treating infection, we usually start by using an antibiotic that works against many species of bacteria (referred to as a broad-spectrum), such as Ceftriaxone or Cefuroxime. According to NICE clinical guidance, the first-line antibiotic choice for uncomplicated diverticulitis is oral co-amoxiclav, with amoxicillin, metronidazole and gentamicin being another common combination often used for more complicated cases. Then, once we’ve obtained a stool or sputum sample from the microbiologists, we can narrow down and choose a specific antibiotic depending on the findings and recommendations of a doctor who specialises in the treatment of infectious diseases.8

Risks and side effects

Many people can suffer adverse reactions from antibiotics, which is why upon admission to the hospital, a detailed history, including prior allergic reactions to medication, is always taken, and documented to ensure this can be avoided. Despite this, side effects can still occur. The risk of side effects can be minimised by choosing a lower dose, as well as administering the drug slowly if given intravenously. However, this is not always possible, as depending on the severity of the infection, you may need to have several doses of medication multiple times per day at a high dosage in order to be effective.

Another important consideration is antibiotic resistance, which is where bacteria develop mutations that can shield them against antibiotics. As responsible clinicians, it is our duty to ensure we find the right balance between providing proper treatment and preventing the development of resistant strains of bacteria. This principle of only prescribing antibiotics when we strongly suspect a bacterial infection is known as antibacterial stewardship. By practicing this, we can ensure that our antibiotic treatments remain effective against these infections for generations to come.

Difficulty arises when an infection is found to be caused by a strain of bacteria that is resistant to multiple types of antibiotics, in which case we may have to choose our most powerful antibiotic, vancomycin. However, this can come with its own risks, as vancomycin can have many side effects, including being unsuitable for pregnant mothers, being toxic to the kidney (nephrotoxic) and damaging to the ears (ototoxic).9

In cases of a suspected allergic reaction to an antibiotic, the most important measure is to immediately stop administering the drug. After that treatment options include administering adrenaline in the case of anaphylaxis, or giving antihistamines for milder reactions where the main symptoms consist of rashes and swelling.10

Mapping the road back to health

For these reasons, acute diverticulitis is best managed on a hospital ward, where there is access to the appropriate medications and organised multi-disciplinary teams of healthcare professionals who are well-versed in its management. In the most severe cases where there is abscess formation or perforation, surgical repair will also be required. Additionally, Intravenous fluids may be given in severe cases where there is rupture and internal bleeding, to maintain a patient's blood pressure.11

Alongside antibiotics, adequate pain relief is also an important mainstay of treatment. Some painkillers can be very toxic for the health of your gut such as aspirin, ibuprofen, or any other drugs of the NSAID family. These drugs can degrade the lining of the stomach and gut, making you more prone to infections and the formation of ulcers, which can then rupture, causing internal bleeding. Additionally, opioid medications such as morphine have a notable side effect of slowing down digestion, and thus are not recommended for those who are constipated or suffering from diverticulitis. Thus, paracetamol is the first line for pain management, with stronger options such as codeine only being considered in more severe cases.12

Non-antibiotic based treatments.

While antibiotics are a key part of treating diverticulitis, preventative measures are by far the most effective way to prevent diverticulitis from developing or recurring. This is because there are no real routine medications that can be given to prevent diverticulitis. Measures such as modifying your diet to increase the amount of fibre your intake can help ensure regular and healthy bowel movements. Drinking enough fluids throughout the day is another important step, and those with chronic constipation, bulk-forming laxatives can be prescribed to aid digestion.13 

All these measures would be discussed by your clinical team as part of a holistic plan for treatment once you have been discharged from the hospital. These measures help to minimise the risk of you being re-hospitalised with a recurrence of diverticulitis, and to improve your condition long-term.


To summarize, antibiotics can play a key role in treating diverticulitis, by targeting bacterial infections to minimise the spread of infection and thereby mitigating the symptoms associated with infection. Selecting the right antibiotic is guided by the severity of the condition, complications, as well as the type of bacteria causing the underlying infection. However, it is also important to consider the risk of side effects, as well as the potential to cause antibacterial resistance in bacteria with every use of antibiotics.

Overall, antibiotics form just one prong of a multi-treatment approach that can target other factors leading to the development of diverticulosis (pouches without inflammation). Many of these are lifestyle changes such as incorporating more fibre into the diet, cessation of smoking, and increased exercise. In addition, proper follow-up care is also essential, given the possibility of future episodes, each with an increasing risk of serious complications.

Like many diseases, early assessment, recognition of symptoms, and prompt treatment are essential for an optimal outcome. For individuals facing diverticulitis, early recognition of symptoms and prompt medical attention are paramount. Antibiotics when used judiciously and in conjunction with other therapeutic measures contribute significantly to successful management of diverticulitis, promoting healing and reducing the risk of recurrence.


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  • Dichman ML, Rosenstock SJ, Shabanzadeh DM. Antibiotics for uncomplicated diverticulitis. Cochrane Database Syst Rev [Internet]. 2022 Jun 22 [cited 2023 Dec 15];2022(6):CD009092. Available from:
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  • Sartelli M, Weber DG, Kluger Y, Ansaloni L, Coccolini F, Abu-Zidan F, et al. 2020 update of the WSES guidelines for the management of acute colonic diverticulitis in the emergency setting. World Journal of Emergency Surgery [Internet]. 2020 May 7 [cited 2023 Dec 15];15(1):32. Available from:
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  • National Guideline Centre (UK). Evidence review for management of recurrent diverticular disease: Diverticular disease: diagnosis and management: Evidence review E [Internet]. London: National Institute for Health and Care Excellence (NICE); 2019 [cited 2023 Dec 15]. (NICE Evidence Reviews Collection). Available from:

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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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