Designing stress studies, part 3: how do you get the pee?

Having discussed how to choose what substance to test for cortisol (blood, saliva, urine, feces, hair), and how to get the blood or saliva, I now move on to how to collect the —

Urine

I don’t have any personal experience with collecting urine for stress studies. How hard can it be, though, right? I certainly was sent to collect urine from patients fairly frequently as a vet student, and have fond memories of chasing male dogs around a yard with a cup while they would spray just two or three drops at a time. The best vet clinics have long-handled soup ladles which you can use to collect the pee. I have certainly never used my own soup ladle to collect pee from my own dogs to take in for analysis when they were doing poorly.

One of my professors this past semester analyzed estrogen in baboon urine. Apparently one waits on the ground while the baboon is in a tree and watches. Eventually the baboon pees out of the tree. It falls on the ground and voila. Confused, I asked, “But doesn’t it soak into the ground? How do you collect it?” She explained that usually it fell onto a leaf and you could use a syringe to get it from there. I thought to myself: your world is not my world.

Getting pee from cats is a whole separate story. You provide them with a litter box with nonabsorbable pellets, and collect the pee from that. It sounds simple in practice, but in my experience many cats will refuse to pee on a non-absorbable surface.

Of course, if all else fails, you can extract urine directly from the bladder of a dog or cat using a needle. This procedure, called a cystocentesis, obviously requires trained personnel, who may not be available to all studies.

No post on pee would be complete without input from the queen of pee, Julie Hecht. When asked, Julie had quite a bit of advice about urine collection in dogs. She pointed out that when the study in question is being performed using laboratory animals rather than pets, you can teach the dogs to pee on command. This is super convenient, but you’re less likely to have that option with pet dogs. She listed some pitfalls that she found with colleting pee from pet dogs:

• Timing! If you need to collect pee before and after the particular event that you’re studying, it is problematic if the animal doesn’t feel the need to go at the right time.
• If you are out walking with the owner and the dog, try not to act weird. Dogs notice when you act weird. Then they don’t feel like peeing. So make casual conversation, even though all you are thinking about is collecting that lovely, lovely pee.
• Wind sucks. Wear plastic gloves.
• If a dog has a lot of fur, finding the urine stream can be hard. She says succinctly: “That stinks.”

So that is the lowdown on pee collection, and the conclusion of my series on designing stress studies!