ACMT Toxicology Visual Pearl: A “Purplexing” Finding

2. Medication effect

Background

Medications often cause benign changes in urine color, such as rifampin’s well-known orange-hued body fluids. In this case, the patient suffered calcium channel blocker toxicity and was administered both hydroxocobalamin and methylene blue to treat refractory hypotension. Hydroxocobalamin, typically used to manage cyanide toxicity, causes red discoloration in urine while methylene blue, classically used to manage methemoglobinemia, causes blue-green urine [1-3].  The combination of both can result in purple urine as above [3].

What else causes purple or purple-like urine?

• Purple Urine Bag Syndrome is a condition associated with chronic catheter use and constipation thought to be caused by a byproduct of bacterial metabolism interacting with the catheter bag and/or tubing [4,5].
• Beets contain a red pigment called betacyanin, which discolors urine anywhere from pink to deep red [6].
• Porphyria can produce a red-to-brown spectrum of urinary discoloration due to the content of porphyrin intermediates [7].

Bedside Pearls: A rainbow differential of urine colors [7]

• Reds: Hematuria/hemoglobinuria, myoglobinuria, some UTIs (e.g., serratia), beeturia, hydroxocobalamin
• Oranges: rifampin, uric acid (urate crystals produce an orange-spectrum precipitate, such as in Lesch-Nyhan Syndrome)
• Yellows: urobilinogen/bilirubin content, vitamin B
• Greens: phenol-containing compounds (e.g., propofol), indole production (Hartnup disease, blue diaper syndrome), pyocyanin/pyoverdin production from Pseudomonas
• Blues: methylene blue, Familial indicanuria (Familial Benign Hypercalcemia)
• Brown/black: severe hemolysis/rhabdomyolysis, paraphenylene diamine poisoning (hair dye), malignant melanoma