Why would a patient with small bowel obstruction be started on antibiotics (abx)?

From the Guidelines

Antibiotics should be started in patients with small bowel obstruction to prevent bacterial translocation and potential complications such as perforation or ischemic bowel, with a recommended regimen including broad-spectrum coverage with a combination of a third-generation cephalosporin plus metronidazole, or a fluoroquinolone plus metronidazole, as stated in the guidelines by the Surgical Infection Society and the Infectious Diseases Society of America 1. The rationale behind antibiotic use is that bowel obstruction leads to bacterial overgrowth in the stagnant intestinal contents, and increased intraluminal pressure can compromise the intestinal wall integrity, allowing bacteria to translocate into the bloodstream. Some key points to consider when starting antibiotics in patients with small bowel obstruction include:

• Coverage for obligate anaerobic bacilli should be provided for distal small bowel, appendiceal, and colon-derived infection and for more proximal gastrointestinal perforations in the presence of obstruction or paralytic ileus, as recommended by the guidelines 1.
• The use of ticarcillin-clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline as single-agent therapy or combinations of metronidazole with cefazolin, cefuroxime, ceftriaxone, cefotaxime, levofloxacin, or ciprofloxacin are preferable to regimens with substantial anti-Pseudomonal activity, as stated in the guidelines 1.
• Antimicrobial therapy should be initiated once a patient receives a diagnosis of an intra-abdominal infection or once such an infection is considered likely, and for patients with septic shock, antibiotics should be administered as soon as possible, as recommended by the guidelines 1. The most appropriate antibiotic regimen for a patient with small bowel obstruction would be a combination of ceftriaxone (1-2g IV daily) plus metronidazole (500mg IV every 8 hours), or a fluoroquinolone (such as ciprofloxacin 400mg IV every 12 hours) plus metronidazole, which provides broad-spectrum coverage against enteric gram-negative aerobic and facultative bacilli and enteric gram-positive streptococci, as well as obligate anaerobic bacilli 1.

From the Research

Reasons for Antibiotic Administration in Small Bowel Obstruction

• The administration of antibiotics (abx) in patients with small bowel obstruction is a common practice, although the evidence supporting its use is limited 2.
• One of the main reasons for starting abx in these patients is to prevent bacterial translocation, which can lead to sepsis and other complications 3.
• However, a study published in 2021 found that the use of abx in patients with adhesive small bowel obstruction did not reduce the risk of sepsis or mortality, and was actually associated with a longer hospital stay 2.
• Another study published in 2017 recommended the use of intravenous antibiotics as part of the medical resuscitation for small bowel obstruction, along with intravenous hydration and nil per os 3.
• The use of abx in small bowel obstruction is also supported by a study published in 2014, which stated that treatment of small bowel and colonic perforations generally includes intravenous antibiotics and fluid resuscitation 4.

Potential Benefits and Risks of Antibiotic Administration

• The potential benefits of abx administration in small bowel obstruction include preventing bacterial translocation and reducing the risk of sepsis and other complications 3.
• However, the use of abx also carries potential risks, such as promoting antibiotic resistance and increasing the risk of Clostridioides difficile colitis 2.
• The decision to start abx in patients with small bowel obstruction should be made on a case-by-case basis, taking into account the individual patient's risk factors and medical history 2, 3.