Peeeeeeeee. We all do it. What happens when we do not? Bad things. Very bad things actually. I was astounded to learn the importance of a seemingly tertiary bodily activity. And so I present a quick look at renal function.
As Jeffrey Guy, MD put it, “Our bodies are basically large bags of saltwater”. An adult man, weighing 80 kg, has approximately 48 kg of H2O within his body (ref: IV Therapy Podcast). The human body has two kidneys which produce urine for various homeostatic purposes. These include regulating the amount of saltwater within the body as well as the components of the saltwater.
If an adult Px is discharging less than half a litre of urine a day they are considered to be oliguric. Oliguria is a symptom of renal failure, either acute or chronic. The latter, chronic renal failure (CRF), develops slowly over a period of months and is less of a pre-hospital concern. Acute renal failure (ARF) is more common and is secondary to many conditions we may find in the pre-hospital Px.
ARF can cause numerous pathologies the most critical of which are pulmonary oedema and hyperkalaemia. If the body loses its ability to shed water a build-up of fluid can occur (known as oedema). A rapid build-up can cause fluid to accumulate within the lungs known as pulmonary oedema (ref: Merck). A quick rise in the potassium levels of blood, known as hyperkalaemia, can cause the gruesome sounding ‘cardiac toxicity’ (ref: Merck). When I asked one of my previous physicians about hyperkalaemia she responded with, “You ever wonder how a doctor would commit suicide…”
Alright I understand that pee is important. What stops peeing in the first place? Consider pee problems within three categories: problems before the kidney, problems of the kidney and problems after the kidney. In medicalese these are termed pre-renal, renal and post-renal.
Pre-renal conditions represent the causal majority, approx 50-80%, of ARF cases. The two most common causes are related to perfusion of the kidneys: hypoperfusion and hypertension. Hypertension is damage incurred from chronic high blood pressure. Hypoperfusion, also known as shock, is poor oxygenation of bodily tissues. Because the brain has no metabolic reserve it will begin to shut down “unneccesary” areas of the body if it feels threatened (ref: Merck). This is why many Px in shock are cool to the touch, their brain chooses to feed itself over the skin. If hypoperfusion is not reversed the brain will continue this triage process for every organ other than the heart. At around four hours the kidneys are on the chopping block (ref: PodMedics).
Renal causes of ARF arise from problems with parts of the kidney itself. For a good introduction take a look at this video podcast. Simplified though, there are three components that can fail within the kidneys: the glomeruli, the tubules and the interstitium (ref: Merck). If a Px reports their urine is the colour of Coca-Cola think ARF. Especially in the presence of some form of oedema (pulmonary or peripheral). The colour is caused by blood in the urine (haematuria) and can be indicative of nephritic syndrome.
Finally if the kidneys are well perfused and functioning properly there must be a clog in the drain. Post-renal causes are also known as outflow-tract diseases. The three most common are infections, kidney stones and various tumours.