A 74-year-old man is evaluated on postoperative day 3 following an elective open inguinal … — USMLE Step 2 CK

A 74-year-old man is evaluated on postoperative day 3 following an elective open inguinal hernia repair due to new-onset right knee pain and swelling. The pain began overnight and has become so severe that he cannot bear weight on his right leg. His medical history is significant for hypertension, chronic kidney disease stage 3b (baseline creatinine $2.1$ mg/dL), and a history of a bleeding gastric ulcer $2$ years ago. His temperature is $38.1$ °C ( $100.6$ °F), blood pressure is $142/86$ mm Hg, and pulse is $98$ /min. Physical examination of the right knee reveals marked effusion, erythema, and warmth. The joint is exquisitely tender to palpation, and range of motion is severely limited by pain. Arthrocentesis is performed, yielding $15$ mL of cloudy yellow fluid. Synovial fluid analysis shows a leukocyte count of $32,000/\mu L$ with $85\%$ neutrophils. Polarized light microscopy reveals numerous rhomboid-shaped crystals that exhibit weak positive birefringence. Gram stain shows no organisms. Which of the following is the most appropriate next step in management?

Intra-articular triamcinolone injectionAnswer
B
Intravenous vancomycin and ceftriaxone
C
Arthroscopic joint irrigation and debridement
D
Initiation of oral allopurinol
E
Administration of oral indomethacin

Answer

Intra-articular triamcinolone injection

The correct step is to perform an intra-articular glucocorticoid injection. This patient is experiencing an acute flare of calcium pyrophosphate deposition (CPPD) disease, commonly known as pseudogout. This condition frequently manifests in the setting of physical stress, such as acute medical illness or surgery (e.g., postoperative day 3). The diagnosis is confirmed by the presence of rhomboid-shaped, weakly positively birefringent crystals in the synovial fluid. Standard first-line therapies for acute pseudogout flares include NSAIDs, oral colchicine, or intra-articular glucocorticoids. However, this patient's chronic kidney disease (CKD stage 3b) and history of a bleeding gastric ulcer are strong contraindications to NSAIDs. Additionally, colchicine must be used with extreme caution or avoided in advanced CKD due to the risk of severe neuromyotoxicity and bone marrow suppression. For monoarticular involvement in a patient with these comorbidities, intra-articular glucocorticoid injection (e.g., triamcinolone) is the safest and most effective therapy.

Step-by-Step Solution

Evaluate the clinical presentation and synovial fluid analysis.

The synovial fluid shows rhomboid-shaped, weakly positively birefringent crystals and a leukocyte count of

32,000/\mu L

This establishes a definitive diagnosis of acute calcium pyrophosphate dihydrate (CPPD) crystal arthritis (pseudogout) and makes septic arthritis highly unlikely.

Review the patient's medical history for contraindications to standard therapies.

The patient has chronic kidney disease stage 3b and a history of a bleeding gastric ulcer.

These comorbidities represent absolute or strong relative contraindications to nonsteroidal anti-inflammatory drugs (NSAIDs) and systemic colchicine.

Select the most appropriate, safe intervention for an acute monoarticular flare.

Intra-articular triamcinolone injection is chosen.

Intra-articular glucocorticoids provide rapid local relief without the systemic risks associated with NSAIDs, colchicine, or oral corticosteroids in this high-risk patient.

Key Concept

Management of acute calcium pyrophosphate deposition (CPPD) disease (pseudogout) in a patient with contraindications to NSAIDs and colchicine.

Estimated Time:1m 0s

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