Diagnose It Answer — April 28, 2026

22-year-old male presents with severe muscle pain, weakness, and swelling in both thighs and lower back after completing a military-style fitness boot camp yesterday — his first day of training. He states he performed over 400 squats as part of initiation. He reports his urine this morning was 'dark brown, like iced tea.' He has not been able to walk without assistance.

Generally healthy, no significant past medical history. No current medications, no supplements beyond a pre-workout powder he took yesterday (containing caffeine and creatine). He denies alcohol and drug use. He had not exercised regularly for the past 3 months before beginning training. His roommate brought him in when he noticed the dark urine and that he was unable to stand from bed without help.

BP 118/74 mmHg, HR 108 bpm, RR 18 breaths/min, Temp 37.3°C, SpO2 99% on room air. Patient is alert and oriented but in significant pain. Bilateral thighs and lower back are swollen, indurated, and extremely tender to palpation. He is unable to fully extend his knees due to pain and swelling.

Urine collected in clear specimen cup — dark brown, mahogany-colored, consistent with myoglobinuria. Point-of-care urine dipstick: 3+ blood, but no red blood cells on microscopy — confirms heme-positive, RBC-negative urine, characteristic of myoglobin. Compartment syndrome evaluated — compartment pressures in bilateral thighs measured: right thigh 28 mmHg, left thigh 32 mmHg — delta pressures (diastolic minus compartment) of 46 and 42 mmHg respectively — above the 30 mmHg safety threshold, no fasciotomy needed. IV access established; aggressive IV fluids initiated: normal saline 1L/hour targeting urine output 200–300 mL/hour to flush myoglobin from renal tubules. Nephrology and orthopedic surgery consulted.

CK (creatine kinase): 142,000 U/L (markedly elevated — normal <200 U/L; values >5,000 carry high risk of renal injury). Myoglobin (serum): 28,400 ng/mL (markedly elevated). Creatinine: 2.4 mg/dL (acute kidney injury from myoglobin-induced tubular toxicity). BMP: K 5.6 mEq/L (hyperkalemia from cell lysis), Ca 6.8 mg/dL (hypocalcemia — calcium deposits in necrotic muscle), phosphate 6.4 mg/dL (elevated from cell release). LDH 2,800 U/L. AST 1,240 U/L, ALT 420 U/L (CK spill into LFTs). Urine microscopy: granular brown casts (myoglobin casts) — no RBCs.