From the Guidelines
The most appropriate initial diagnostic study for a patient with persistent left lower quadrant abdominal pain despite 2 days of broad-spectrum antibiotics and a clear liquid diet is a CT scan of the abdomen and pelvis with intravenous and oral contrast. This recommendation is based on the highest quality and most recent evidence available, which emphasizes the importance of CT scans in diagnosing diverticulitis and other causes of left lower quadrant pain 1. The CT scan provides detailed visualization of the abdominal structures, particularly the colon, and can effectively identify diverticulitis, as well as detect complications such as abscess formation, perforation, or fistula development that might explain why the patient has not responded to initial therapy.
Key Points to Consider
- The patient's symptoms and lack of improvement with initial treatment suggest the need for advanced imaging to guide further management decisions.
- A CT scan of the abdomen and pelvis with intravenous and oral contrast is highly accurate for diagnosing diverticulitis, with a sensitivity and specificity of 95% 1.
- Other imaging modalities, such as ultrasound and MRI, may be less sensitive or less readily available, and are not recommended as the initial diagnostic study in this scenario.
- The negative stool occult blood test does not rule out significant pathology, making advanced imaging necessary to guide further management decisions.
Rationale for Recommendation
The recommendation for a CT scan of the abdomen and pelvis with intravenous and oral contrast is based on the evidence from the American Gastroenterological Association (AGA) clinical practice update on medical management of colonic diverticulitis, which suggests that CT should be considered to confirm the diagnosis of diverticulitis in patients without a prior imaging-confirmed diagnosis and to evaluate for potential complications in patients with severe presentations 1. Additionally, the American College of Radiology (ACR) Appropriateness Criteria for left lower quadrant pain-suspected diverticulitis recommend CT as the imaging examination of choice for evaluating patients with suspected descending or sigmoid colon diverticulitis 1.
From the Research
Diagnostic Approach
The patient presents with left lower quadrant abdominal pain and has not improved after 2 days of broad spectrum antibiotics and a clear liquid diet, with a stool exam negative for occult blood. The most appropriate initial diagnostic study in this scenario would be:
- Computed Tomography (CT) scan, as it is a highly sensitive and specific modality for diagnosing acute diverticulitis and its complications, as well as for excluding alternate causes of pathology 2, 3, 4.
Rationale
CT scan is preferred because it can help differentiate between diverticulitis and other conditions such as appendicitis or colon cancer, and can also identify complications such as abscesses or perforation 2, 3, 4.
Contrast Enhancement
The use of contrast enhancement in CT scans can be beneficial in diagnosing acute colonic diverticulitis, but non-contrast CT may be non-inferior for the diagnosis of diverticulitis 4. However, contrast-enhanced CT is associated with significantly higher sensitivities for the presence of an abscess or perforation 4.
Considerations
It is also important to consider the patient's overall clinical presentation and medical history when selecting the most appropriate diagnostic study, as well as the potential risks and benefits of each study 5, 6.