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

A $74$ -year-old man is evaluated on postoperative day $3$ following an uncomplicated laparoscopic cholecystectomy. Over the past $12$ hours, he has developed a fever and severe pain in his right knee. He states the pain is so intense that he cannot bear weight or tolerate the bedsheets touching his leg. His medical history is significant for essential hypertension, diet-controlled type 2 diabetes mellitus, and hypothyroidism. Current medications include lisinopril and levothyroxine. His temperature is $38.4^\circ\text{C}$ ( $101.1^\circ\text{F}$ ), blood pressure is $138/86\text{ mmHg}$ , and pulse is $98/\text{min}$ . Cardiopulmonary examination is unremarkable. His abdomen is soft and non-tender, and the surgical incisions are clean and intact. Examination of the right knee reveals marked erythema, warmth, and a large effusion. The joint is exquisitely tender to palpation and passive range of motion. Laboratory studies show a leukocyte count of $13,500/\text{mm}^3$ and a thyroid-stimulating hormone (TSH) level of $5.5\text{ mIU/L}$ . Arthrocentesis of the right knee yields $3\text{ mL}$ of cloudy synovial fluid. Analysis of the fluid reveals a leukocyte count of $28,000/\text{mm}^3$ with $80\%$ neutrophils. Polarized light microscopy demonstrates rhomboid-shaped crystals with weak positive birefringence. Gram stain of the synovial fluid reveals no organisms. Which of the following is the most appropriate next step in the management of this patient?

A
Intravenous vancomycin and ceftriaxone
B
Computed tomography scan of the abdomen and pelvis
Intra-articular triamcinolone injectionAnswer
D
Obtain a serum uric acid level
E
Increase the daily levothyroxine dosage

Answer

The correct answer is intra-articular triamcinolone injection.

The correct answer is an intra-articular triamcinolone injection. This patient is experiencing an acute flare of calcium pyrophosphate dihydrate (CPPD) crystal arthritis, commonly referred to as pseudogout. Acute crystal arthropathies are frequently triggered by the physiological stress of surgery or severe medical illness. The diagnosis is confirmed by the synovial fluid analysis revealing rhomboid-shaped, weakly positively birefringent crystals. The synovial white blood cell count is highly inflammatory (

28,000/\text{mm}^3

) and can sometimes overlap with the septic range, but the identification of crystals and a negative Gram stain point to CPPD as the primary etiology. The fever is a systemic manifestation of the intense autoinflammatory response induced by the crystals. For a localized, monoarticular flare in an elderly postoperative patient, an intra-articular glucocorticoid injection is the most appropriate first-line therapy. It provides rapid relief while avoiding the systemic adverse effects associated with NSAIDs (e.g., acute kidney injury, gastrointestinal bleeding) and colchicine, which are less ideal in the immediate postoperative period.

Step-by-Step Solution

Analyze the patient's clinical presentation and setting.

An elderly patient on postoperative day 3 presents with an acute, severe monoarticular arthritis (hot, swollen, tender right knee) accompanied by a fever.

Postoperative status is a major physiological stressor that frequently triggers acute flares of crystal arthropathies.

Interpret the synovial fluid analysis.

The fluid shows

28,000\text{ WBCs/mm}^3

(inflammatory range), a negative Gram stain, and rhomboid-shaped crystals with weak positive birefringence.

These findings are strictly diagnostic for calcium pyrophosphate dihydrate (CPPD) crystal deposition disease, commonly known as pseudogout.

Determine the optimal acute management for monoarticular pseudogout in this specific patient.

Intra-articular glucocorticoid injection is selected.

In an elderly patient recovering from surgery, systemic therapies like NSAIDs (risk of AKI, bleeding) and colchicine (gastrointestinal toxicity, dosing adjustments) carry significant risks. An intra-articular injection provides rapid, localized relief with minimal systemic side effects.

Key Concept

Diagnosis and management of acute calcium pyrophosphate dihydrate (CPPD) crystal arthritis (pseudogout) in the postoperative setting.

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