Q: What could be the underlying renal pathophysiology in cola or tea colored urine?
Answer: Possible glomerular bleeding
An astute physician can quickly differentiate glomerular and nonglomerular bleeding at first sight at the bedside.
Cola or tea-colored or dark brown urine may indicate glomerular bleeding, in which prolonged transit time through the nephron in an acidic urine environment can result in the formation of methemoglobin, giving the urine a smoky brown, tea, or cola color.
Obviously, this is a first glance bedside observation at the bedside. Urine can still appear red or pink in glomerular bleeding if urine is not acidic, or transit time is too fast, but by default, as a rule of thumb, in gross hematuria -
- nonglomerular bleeding appears red or pink, and
- glomerular bleeding appears dark brown (cola colored)
Other caveats are false colorations due to dye, food, drugs, or underlying non-renal pathophysiologies such as rhabdomyolysis or hyperbilirubinemia.
#nephrology
References:
1. Stark A, Kanduri SR, Ramanand A, Rosenbloom S, Varghese V, Chalmers DR, Velez SA, Gonzalez-Fuentes C, Wickman TJ, Mohamed M, Shueib A, Zarm A, Lukitsch I, Velasco-Gonzalez C, Seltzer JR, Velez JCQ. Glomerular Hematuria for the Diagnosis of Glomerulonephritis. Glomerular Dis. 2025 Apr 10;5(1):206-218. doi: 10.1159/000545051. PMID: 40406196; PMCID: PMC12097761.
2. Rose BD. Pathophysiology of Renal Disease, 2nd ed, McGraw-Hill, New York 1987. p.10.
3. Hamadah AM, Gharaibeh K, Mara KC, Thompson KA, Lieske JC, Said S, Nasr SH, Leung N. Urinalysis for the diagnosis of glomerulonephritis: role of dysmorphic red blood cells. Nephrol Dial Transplant. 2018 Aug 1;33(8):1397-1403. doi: 10.1093/ndt/gfx274. PMID: 29156008.
