Question

A friend travelling with you on the kayak trip drank a lot of sports drink before she was blown off course. She decides to collect her urine in a bottle. She collects 250 mL of 300 mOsM urine over the course of the day. After collecting her urine, she has a normal body volume of 30 L and a normal body concentration of 300 mOsM. She begins to sweat and loses 100 mL of 100 mOsM sweat. As revolting as it is, she drinks all of her urine. If the kidnet can concentrate urine over a range of 50-1400 mOsM, can the kidneys use the urine she drank to return her to her normal volume and concetration? Use calculations to explain and briefly state yes or no.

Answer 1

Ans.) Urine osmolality is used to measure the number of dissolved particles present in urine. If the value is less then 265 mOsM and more then 320 mOsM, it indicates critical value. Osmolality is important in evaluating the concentrating ability of kidney.

In this case, the girl has a normal body volume of 30 L and a normal body concentration of 300 mOsM. But after sweeting, volume and concentration is decreased. Yes, here, kidney can use the urine she drank to return her to her normal volume and concentration.

Urine is 95 percent water and sterile, hence in the short term it's safe to drink and does replenish lost water. The girl can survive on her own urine for a while but for a longer period she needs water. Because the other 5 percent of urine comprises a diverse collection of waste products which includes nitrogen, potassium, and calcium. So, when urine is consumed for a longer period, it become highly concentrated with dangerous waste products and drinking it can cause symptoms similar to those brought on by total kidney failure.