Urine Casts: Definition and Development (Nursing)

00:00 Hi, welcome to our video series on interpreting lab values.

00:05 In this portion of the series, we're going to look at a urinalysis microscopic exam, but we're looking specifically at urine casts.

00:13 Now keep in mind, cast in the urine indicate kidney disease versus a lower urinary tract disease.

00:20 So we pay really close attention to these.

00:23 Before I go on, I want to make sure you are crystal clear on that.

00:30 Cast in the urine indicate we've got a kidney problem.

00:34 It's not a lower urinary tract problem, it's definitely a kidney problem.

00:38 Here's why.

00:39 Casts are formed in the lumen of the nephron of the kidneys, and then they are excreted in the urine.

00:46 That's why we know we got a kidney problem because casts are formed in the specific anatomy of the kidney.

00:53 Now they're made up of these hardened proteins and other cells.

00:58 So identifying the other cells can give us really important information about the conditions in the nephron.

01:05 Okay, I don't want to go on until we're really clear on what this content is.

01:10 Casts, tell me I've got a kidney problem like right in the kidney? Why? Because cast are formed in the lumen.

01:18 And we say lumen, that's the opening of the tube in the nephron, right? So that's why they're shaped kind of like a tube.

01:26 What are they made up of? A hardman protein plus other cells.

01:31 So cast usually have a hardman protein, and other cells.

01:36 So it's those other cells, if we can identify them, they can give us really important information about specific conditions in the nephron.

01:46 So who's most likely to develop a cast? So what type of patients or what things are going on in their body that make them most likely to develop cast? Low renal flow is one of them.

01:59 Now let's think about that.

02:00 Cast, are hard protein.

02:03 Think of them as kind of a mold, and then these other cells get in there.

02:07 So how would low flow make that a problem? Well, if I'm going to make a mold, I would like things to be moving through very slowly, right? If things are whipping through that kidney, you're not likely to have many casts developed.

02:21 What about high salt concentration? Yeah, this helps make an environment that's really friendly, the cast being developed.

02:29 The third piece is low or acidic pH.

02:34 So if a patient has casts, they likely have low renal flow, meaning they've got some kidney damage, probably a high salt concentration, and a low or acidic pH.