Runners / Cyclists / Walkers : Pay Attention!

The risks of severe renal damage caused by endurance events

Although today’s ultra marathon runners and endurance cycling event participants are very well informed on issues such as training methodology, dietary requirements, hydration, footwear and all the vital do’s and don’ts that a variety of experts have experienced or researched, there are sports people who risk their very lives during endurance events such as the Comrades Ultra Marathon, the Argus cycling tour.
One can have all this information at hand and still end up with serious medical problems after the race.
Why?
Mainly because there are so many variables on race-day that might affect a healthy and well trained athlete such as temperature, humidity, the rate of wind movement across the body, the electrolyte balance in the body, individual susceptibility to various conditions etc.

The main problems related to kidney function during and after a race of this magnitude are:

Bloody urine (haematuria) after excercise

Acute Kidney Failure

Kidney stones

1. Bloody urine is quite common and is often due to repeated impact of the walls of the bladder against each other with subsequent bruising and bleeding. This causes bleeding in the bladder which is evident as the athlete passes urine after the race. This condition should clear within 72 hours as the wall of the bladder is repaired. This can effectively be prevented by trying not to empty the bladder completely just before and also during the race. The half-filled bladder is less likely to get as traumatised as a completely empty one. Although this is a self limiting condition, care must be taken and medical help should be obtained to exclude other, more serious reasons for haematuria. Bleeding in the bladder for periods longer than 48 to 72 hours must be considered as potentially serious and action must be taken.

2. Acute kidney failure is a serious condition and should be treated as such. Although not an uncommon complication of Heatstroke and Dehydration, in a lot of cases endurance athletes developed kidney failure without these predisposing conditions.
Reasons are unclear but seem to indicate that certain individuals might have a specific musculoskeletal defect that causes excessive breakdown of muscle tissues during prolonged exercise, with a resulting leakage of a substance called myoglobin into the blood circulation. This substance ultimately arrives in the kidneys and is filtered but acts as a toxin or poison to the kidneys, causing failure.
This is a variable that is unknown until it happens.
Other reasons for kidney failure on this basis of toxins being filtered are the use of anti-inflammatory drugs or pain killers before and during the race. Popular items are Indomethacin, Ibuprofen, Diclofenac, Aspirin, Naproxen. Athletes take these to prevent pain and reduce inflammation, thus shortening the recovery period. These agents are best left in the medicine cupboard and should not be taken as there is little evidence that they are effective for this application and the risks far outweigh the advantage.

What are the symptoms of acute kidney failure? The first and most obvious one is the inability to pass any significant urine during the first 24 hours after the race. This should immediately trigger the alarm bells and the athlete should seek immediate medical help – preferably a hospital with a renal care unit where dialysis can be, and probably will be performed. Missing this important first sign will cause the person to feel really ill after 36 to 48 hours with severe headaches and nausea. The headache is due to a steep rise in blood pressure as well as the increase in metabolic end-products not being removed from the system. At this stage the failure is well established and will need repeated renal dialysis until the kidneys recover.

Prevention:

Avoid heat stroke

Drink 100 -125ml fluid every 10 to 15 minutes as well as 400 to 500ml before the race.

Sponge frequently and adequately

Do not overestimate your ability, especially near the end of the race (60km and more)

Do not ignore warning signs (weakness, stumbling, headache, nausea, dizziness, apathy)

Abstain from taking anti-inflammatory drugs

Have a test done to determine the general condition of the kidneys well before the race.

Common urine dip tests can exclude kidney infection, certain metabolic disorders.

GFR test (Glomerular Filtration Rate) can determine the rate at which the kidneys filtrate and secrete metabolic waste. This test is available at some pharmacies and also at most pathology labs.

3. There is an abnormally high incidence, about five times normal, of kidney stones among male runners. It must be added that runners most likely to develop stones are those that have been running for the longest time, running the longest distances during training and who are the fastest runners.
Here the message is quite clear:
Always avoid dehydration.
Repeated dehydration can lead to the formation of kidney stones.
Drink optimal volumes of fluid during, but also immediately after the race, especially in hot and humid climates.

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