Title: Marathon nephritis and postural proteinuria
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Marathon nephritis and postural proteinuria
When urinary abnormalities don’t indicate renal disease |
From Tom Brown at Oxford (1861) illust Sydney P Hall (1903 edition) |
Richard Bright’s 1827 description of the association of proteinuria with dropsy and serious kidney disease led to doctors of the 1800s kitting up with apparatus to test for proteinuria, long before they could measure blood pressure. Uroscopy (looking at urine) had after all for centuries been a key element of the theatre of medical consultation. But proteinuria was now definitely associated with renal disease, and soon enough it became associated with adverse long term outcomes. This was recognised by insurance companies by the early 1900s, and confirmed in an impressive 37-45 year follow-up study of University of Minnesota entrants from the 1920s (Levitt 1967. 185 of 10,000 male students had persistent proteinuria; all but two were traced).
Inevitably, examples of benign proteinuria, and haematuria, began to be described in the late 1800s.
Proteinuria after exertion was first described in 1878. It was memorably characterised by Collier in 1907 in a systematic report on 156 Oxford rowers training for the ‘Torpids’. 57% of urine samples taken 1-1.5h after vigorous rowing contained protein. Smaller studies in other populations of athletes gave similar results. He compared these results with the historically recorded lifespans of 294 participants in the University Boat Race – they were longer than average. This made it seem unlikely that post-exertional proteinuria conveyed a bad long term prognosis.
‘March Haematuria’, haematuria after exertion, was mentioned in 1881. Red urine, or red cells, or even sometimes red cell casts and fragmented red cells suggestive of glomerular bleeding, have been repeatedly described after sustained running or marching. Th exertion causing it is associated with repeated impacts that might conceivably fragment red cells. So not rowing. A series from Uruguay (Tobal 2008) describes epidemic rusty urine after prolonged hand drumming at carnival, with rare cases of dialysis-requiring acute kidney injury. Marathons and other long-distance running are the most common cause of this in the present day. Some runners see red or rusty urine, while dipsticks may be abnormal in 25%. Reports of this phenomenon are mixed with occasional patients with rhabdomyolysis, and probably some with underlying renal disease, but in most the haematuria resolves within 2-3 days – so more slowly than post-exertional proteinuria.
The alarming combination of red cell casts and proteinuria after severe exertion has given rise to the names such as Athletic Pseudo-nephritis (Gardner 1956).
Postural (orthostatic) proteinuria indicates that proteinuria is normal in first-morning samples, but elevated at later times of day. It is usually encountered in children or young adults. Pavy (1886) gives a wonderful account of how he investigated it by keeping his patients in bed till late in the day, and subjecting one to a cold bath to test whether it was posture or temperature change that caused the protein leak.
Postural proteinuria turns out to be common in young people – the most common cause of proteinuria – and benign. Most grow out of it. So you should always test a first-morning sample in young people with a positive dipstick.
Surprisingly, the mechanism of all of these benign urinary changes is largely unknown. There’s an opportunity for fame.
Further info
Collier W (1907) Functional albuminuria in athletes. Br Med J i:4-6
Gardner KD (1956) “Athletic pseudonephritis” – alteration of the urine sediment by athletic competition. JAMA 161:1613-17
Gilligan DR, Blumgart HL (1941). March hemoglobinuria: Studies of the Clinical Characteristics, Blood Metabolism and Mechanism: with Observations on Three New Cases, and Review of Literature. Medicine (Baltimore) 20:341–395
Levitt, J. I. (1967). The prognostic significance of proteinuria in young college students. Annals Int Med 66:685–696.
Pavy FW (1886) A further contribution on cyclical albuminuria; with observations on the effect of various conditions upon the diurnal appearance of albumen. Lancet 127:437-8
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