16.2 Basic Concepts
Open Resources for Nursing (Open RN)
Let’s begin by reviewing the basic anatomy and physiology of the urinary and gastrointestinal systems.
Urinary System
The urinary system, also referred to as the renal system or urinary tract, consists of the kidneys, ureters, bladder, and urethra. The purpose of the urinary system is to eliminate waste from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites, and regulate blood pH. The kidneys filter blood in the nephrons and remove waste in the form of urine. Urine exits the kidney via the ureters and enters the urinary bladder, where it is stored until it is expelled by urination (also referred to as voiding).[1] See Figure 16.1[2] for an image of the male urinary system. The female urinary system is similar except for a smaller urethra.
A healthy adult with normal kidney function produces 800-2,000 mL of urine per day, depending on fluid intake, as well as the amount of fluid lost through sweating and breathing. The bladder typically holds about 360-480 mL of urine. As the bladder fills, it sends signals to the brain that it is time to urinate. The urinary tract includes two sets of muscles that work together as a sphincter, closing off the urethra to keep urine in the bladder until the brain sends signals to urinate. Urination occurs when the brain sends signals to the wall of the bladder to contract and squeeze urine out of the bladder and through the urethra. Frequency of urination depends on how quickly the kidneys produce urine and how much urine a person’s bladder can comfortably hold.[3]
Normal urine should be clear, pale to light yellow in color, and not foul-smelling. However, some foods or medications may change the smell or color of urine. For instance, phenazopyridine (Pyridium), a common medication prescribed to treat the pain, frequency, and burning associated with urinary tract infections, can cause urine to appear orange.[4]
Nurses frequently monitor and document a client’s urine output as part of the overall plan of care. It can be collected by placing a collection hat in the client’s toilet and then measured in a graduated cylinder. If the client has an indwelling catheter, the urine is emptied every shift from the catheter bag and measured in a graduated cylinder. For infants and toddlers, the number of daily wet diapers provides a general measure of urine output. For more specific measurement of urine output during hospitalization, wet diapers are weighed.
Terms commonly used to document conditions related to the urinary tract are as follows:
- Anuria: Absence of urine output, typically found during kidney failure, defined as less than 50 mL of urine over a 24-hour period.
- Dysuria: Painful or difficult urination.
- Frequency: The need to urinate several times during the day or at night (nocturia) in normal or less-than-normal volumes. It may be accompanied by a feeling of urgency.[5]
- Hematuria: Blood in the urine, ei