E3276. The Utility of Dual-Energy CT in the Emergency Department: A Case-Based Review of Gout Mimicking 10 Different Acute Diseases
  1. Jasmine Zhao; University of California, Irvine
  2. Peter Pham; University of California, Irvine
Gout is the most common deposition inflammatory arthropathy and is precipitated by the accumulation of monosodium urate (MSU) crystals. Patients with gout may present to the emergency department with symptoms that can be nonspecific and mimic other acute diseases. Definitive diagnosis requires joint aspiration or biopsy, which can be invasive and challenging to perform. The use of dual-energy CT (DECT) to noninvasively diagnose gout has been clinically validated with 78-100% sensitivity and 89-100% specificity. The purpose of this educational exhibit is to emphasize the unique capability of DECT to diagnose acute and ambiguous cases of gout in emergency settings.

Educational Goals / Teaching Points
The educational goals are to understand the basic principles of DECT technology used to detect MSU crystals, describe DECT imaging findings specific to gout, learn that DECT can distinguish gout from 10 different acute diseases with overlapping clinical presentations, and recognize the key advantages and pitfalls of DECT in detection of gout.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
DECT acquires dual-energy attenuation data at low and high energy spectra. A material decomposition algorithm is used to separate MSU crystals from calcium based on differences in dual-energy attenuation ratios. MSU crystals can be color-coded and overlayed on CT images for diagnosis of gout. Ten cases will be presented where DECT definitively diagnoses gout masquerading as osteochondral fracture, spine neoplasm, parosteal osteosarcoma, chronic lymphocytic leukemia, septic arthritis, patella fracture, Achilles tendon rupture, sacroiliitis, myositis/cellulitis, and nephrolithiasis. Advantages of DECT include noninvasive modality, speed, practicality for emergency room applications, and high sensitivity and specificity. Pitfalls include false positive detection of keratin, osteoarthritis, beam hardening and motion, as well as false negatives that may occur in the early stages of disease (< 6 weeks).

DECT plays an essential role in the diagnosis of gout. DECT should be incorporated in routine emergency imaging protocols as it may quickly diagnose acute and challenging gout presentations and guide management.