Let me paint you a scene: a young man from Mashkel, fit and otherwise healthy, walks into the ER clutching his flank like he’s auditioning for a kidney stone commercial. CT KUB? Boom — radiopaque stones. Urine amino acid chromatography? Positive for cystine. Welcome to cystinuria, folks — a rare, autosomal recessive disorder with a memorably rebellious renal tubule.
And the guilty amino acids? COAL. Yes, just like what your nephrologist would give you for being naughty.
🧠 Mnemonic: “C.O.A.L”
These are the four dibasic amino acids that aren’t reabsorbed by the proximal convoluted tubule in cystinuria:
| Letter | Amino Acid |
|---|---|
| C | Cystine |
| O | Ornithine |
| A | Arginine |
| L | Lysine |
🩺 Real Case from the Ward
A 20-something patient from Tump came to our OPD at Sheikh Khalifa Bin Zayed Hospital with recurrent renal stones. Dr. Danish Ramzan had already ruled out hyperparathyroidism and uric acid stones. Eventually, a positive cyanide-nitroprusside test sealed the deal: cystinuria.
“Why do I keep making stones?” the poor guy asked.
Dr. Basit Khan explained, “Your kidneys aren’t fans of recycling certain amino acids. They dump them into your urine, and cystine forms stones faster than we get calls during night duty.”
We started him on hydration, urinary alkalinization, and dietary changes. No more cola — only COAL for him. 🚱
