In a patient with Enterococcus and Klebsiella infection of the hip joint, should the initial CT of the abdomen and pelvis be performed with intravenous iodinated contrast?

CT Abdomen and Pelvis with IV Contrast for Suspected Intra-Abdominal Source of Hip Joint Infection

Yes, you should order CT abdomen and pelvis WITH intravenous contrast for your initial imaging study. IV contrast is essential for detecting inflammatory conditions, abscesses, and infectious sources that may have seeded your patient's hip joint with these polymicrobial organisms 1.

Why IV Contrast is Critical in This Clinical Scenario

IV contrast increases detection of urgent inflammatory pathology by enabling visualization of bowel wall enhancement abnormalities, abscesses, and infectious foci that would be missed on non-contrast imaging 1, 2. In patients with suspected intra-abdominal infection:

• IV contrast changes diagnosis in 49% of cases and alters surgical management in 25% of patients with inflammatory conditions 1, 2
• Mural enhancement patterns—essential for identifying inflammatory bowel disease, diverticulitis, appendicitis, and other infectious sources—are only visible with IV contrast 1
• Non-contrast CT markedly reduces sensitivity for detecting small abscesses, inflammatory changes, and vascular complications 1, 3

The combination of Enterococcus and Klebsiella strongly suggests a gastrointestinal or genitourinary source, making contrast enhancement mandatory to identify the primary focus 1.

Specific Imaging Protocol

Order CT abdomen and pelvis WITH IV contrast (standard protocol, not CTA) for evaluation of suspected intra-abdominal infectious source 1, 4. The protocol should include:

• Standard IV contrast-enhanced CT (not CT angiography) is appropriate for inflammatory/infectious evaluation 1
• Avoid oral contrast unless there is specific concern for bowel obstruction or fistula—it delays imaging, is poorly tolerated in acutely ill patients, and provides no additional diagnostic value for detecting abscesses or inflammatory foci 1
• Arterial and portal venous phase imaging to optimize detection of inflammatory changes and abscess formation 1

Addressing Renal Function Concerns

The evidence strongly supports using IV contrast even in patients with mild-to-moderate renal impairment when the diagnostic benefit is critical 5, 6:

• The risk of contrast-induced nephropathy is negligible in patients with creatinine <1.5 mg/dL or eGFR >30 mL/min/1.73m² 5, 6
• In patients with eGFR >30, the benefits of diagnostic information for detecting life-threatening infections far outweigh the minimal nephrotoxicity risk 5
• Only in patients with eGFR ≤30 mL/min/1.73m² does the risk of post-contrast AKI become significant (51% increased risk) 6

If your patient has eGFR >30, proceed with IV contrast without hesitation 5, 6. If eGFR is ≤30, the decision requires weighing the critical need to identify a potentially life-threatening intra-abdominal source against nephrotoxicity risk—but given the severity of polymicrobial septic arthritis, contrast is likely still warranted with appropriate hydration 5, 6.

Common Pitfalls to Avoid

• Do not order non-contrast CT initially—this will miss the majority of inflammatory pathology and abscesses, forcing a repeat study with contrast and doubling radiation exposure 1, 2
• Do not delay imaging by insisting on oral contrast—it adds no diagnostic value for infection detection and delays definitive diagnosis 1
• Do not withhold contrast based solely on mildly elevated creatinine (1.5-2.0 mg/dL)—the diagnostic imperative outweighs minimal nephrotoxicity risk in this range 5

Expected Diagnostic Yield

Contrast-enhanced CT has 93-96% sensitivity and 93-100% specificity for detecting intra-abdominal inflammatory and infectious pathology 4. The study should identify:

• Diverticular abscesses, appendiceal pathology, or other colonic sources
• Pelvic abscesses or inflammatory conditions
• Genitourinary infections (pyelonephritis, perinephric abscess)
• Inflammatory bowel disease complications
• Psoas abscesses or other retroperitoneal collections

If the initial contrast-enhanced CT is negative but clinical suspicion remains high, the yield of a repeat CT within 72 hours is only 5.9%—so ensure the first study is optimized with IV contrast 1.