Urinary and Elimination
Urinary Elimination depends on the function of the kidneys, ureters, bladder, and urethra. Kidneys remove wastes from the blood to form urine. Ureters transport urine from the kidneys to the bladder. The bladder holds urine until the urge to urinate develops. Urine leaves the body through the urethra. All organs of the urinary system must be intact and functional for successful removal or urinary wastes.
The kidneys lie on either side of the vertebral column behind the peritoneum and against deep muscles of the back. The kidneys extend from the twelfth thoracic to the third lumbar vertebrae. Normally, the left kidney is higher than the right because of the anatomical position of the liver.
Waste products of metabolism that collect in the blood are filtered in the kidneys. Blood reaches each kidney by a renal (kidney) artery that branches from the abdominal aorta. Approximately 20 to 25% of the cardiac output circulates each minute thru the kidneys. The nephron, the functional unit of the kidney, forms the urine. The nephron is composed of the glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal tubule, and collecting duct.
The kidneys are responsible for maintaining a normal RBC volume by producing erythropoietin. Erythropoietin functions within the bone marrow to stimulate red blood cell production and maturation and prolongs the life of mature RBCs. Clients with chronic alterations in kidney function cannot produce sufficient quantities of this hormone; therefore they are prone to anemia.
Renin is another hormone produced by the kidneys. Its major role is the regulation of blood flow in times of renal ischemia. Renin is released form juxtaglomerular cells.
Renin functions as an enzyme to convert angiotensinogen ( a substance synthesized by the liver) into angiotensin I. Angiotensin I is converted to angiotensin II in the lungs. Angiotensin II causes vasoconstriction and stimulates aldosterone release from the adrenal cortex. Aldosterone causes retention of water, which increases blood volume. Both of these mechanisms increase arterial blood pressure and renal blood flow.
The kidneys also play a vital role in calcium and phosphate regulation by producing a substance that converts Vitamin D into its active form. Clients with alterations in kidney function are prone to develop renal bone disease resulting in demineralization of bone caused by impaired calcium absorption.
Urine enters the renal pelvis from the collecting ducts and travels to the bladder through ureters. The ureters are tubular structures that enter the urinary bladder in the pelvic cavity at the ureterovesical junction. Urine draining from the ureters to the bladder is usually sterile.
Three layers of tissue form the wall of the ureter. The inner layer is a mucous membrane continous with the lining of the renal pelvis and urinary bladder. The middle layer consists of smooth muscle fibers that transport urine by peristaltic waves. An outer layer of fibrous connective tissue supports the ureters.
Peristaltic waves cause the urine to enter the bladder in spurts rather than steadily. The ureters enter obliquely through the posterior bladder wall. This arrangement normally prevents the reflux of urine from the bladder into the ureters during the act of micturition by the compression of the ureter at the ureterovesical junction (the juncture of the ureters with the bladder). An obstruction within a ureter, such as a kidney stone (renal calculus), results in strong peristaltic waves that attempt to move the obstruction into the bladder. These strong peristaltic waves result in pain often referred to as renal colic.
The urinary bladder is a hollow, distensible, muscular organ that stores and excretes urine. The sphincter prevents escape of urine from the bladder and is under voluntary control.
Urine travels from the bladder thru the urethra and passes outside of the body thru the urethral meatus. In women the urethra is approximately 1 ½ to 2 ½ inches long. The short length of the urethra predisposes women and girls to infection. Bacteria can easily enter the urethra from the perineal area. In men the urethra, which is both a urinary canal and a passageway for cells and secretions from reproductive organs, is about 8 inches long. The male urethra has 3 sections: the prostatic urethra, the membranous urethra, and the penile urethra.
Act of Urination
Several brain structures influence bladder function, including the cerebral cortex, thalamus, hypothalamus, and brain stem. Together they suppress contraction of the bladder’s detrusor muscle until a person wishes to urinate or void. Once voiding occurs, the response is a contraction of the bladder and coordinated relaxation of pelvic floor muscles. The bladder normally holds as much as 600ml of urine, however, the desire to urinate can be sensed when the bladder contains smaller amounts of urine. (150 to 200ml for adults and 50 to 100ml for kids)
*Damage to the spinal cord above the sacral region causes loss of voluntary control of urination, but the micturition reflex pathway may remain intact, allowing urination to occur reflexively. This condition is called a reflex bladder. If bladder emptying is hindered by chronic obstruction such as prostate enlargement, over time the micturition reflex become nonfunctional and severe urinary retention occurs.
Disease processes that affect urine elimination may affect renal function (changes in urine volume or quantity), the act of urine elimination, or both. Those conditions that affect urine volume and quality are generally categorized as prerenal, renal, or postrenal in origin.
Prerenal alterations decrease circulating blood flow to and thru the kidneys with resulting decreased blood flow to renal tissue. In other words, the alterations occur before the urinary system. The decrease in renal blood flow leads to oliguria-diminished capacity to form urine or, less commonly anuria- inability to produce urine. Selected causes include dehydration, hemorrhage, and congestive heart failure.
Renal alterations result form factors that cause injury directly to the glomeruli or renal tubule, interfering with their normal filtering, reabsorptive, and secretory functions. Selected causes include transfusion reactions, diseases of the glomeruli, and systemic diseases such as diabetes mellitus.
Postrenal alterations result from obstruction to the flow of urine in the urinary collecting system caused by calculi, blood clots, or tumors anywhere from the calyces (drainage structures within the kidney) to the urethral meatus. Urine is formed by the urinary system but cannot be eliminated by normal means.
Any disease can affect the ability to micturate. For example, diabetes mellitus and multiple sclerosis cause neuropathic conditions that alter bladder function. Clients with cognitive impairments, such as Alzheimer’s disease, may lose the ability to sense a full bladder or be unable to recall the procedure for voiding.
Dialysis and organ transplantation are 2 methods of renal replacement.
Peritoneal dialysis is an indirect method of cleansing the blood of waste products using osmosis and diffusion. Drained with a catheter by gravity.
Hemodialysis uses a machine equipped with semi permeable filtering membrane (artificial kidney) that removes accumulated waste products and excess fluids from the blood. Blood is basically pumped thru a machine and cleansed and put back into patients body.
North Americans expect toilet facilities to be private. Social expectations such as school recess influence the time of urination.
Men generally urinate best in a standing position, whereas women generally sit on a toilet. In some cultures the client would squat over a receptacle rather than sit on one.
Anxiety and emotional stress may cause a sense of urgency and increased frequency of urination.
Attempting to void in a public restroom may result in temporary inability to void. Privacy and adequate time to urinate are usually important to most people.
Weak abdominal and pelvic floor muscles impair bladder contraction and control of the external urethral sphincter. Poor control of micturition can result from muscle wasting caused by prolonged immobility, stretching of muscles during childbirth, menopausal muscle atrophy, or traumatic damage to muscles.
The kidneys maintain a sensitive balance between retention and excretion of fluids. If fluids and the concentration of electrolytes and solutes are in equilibrium, an increase in fluid intake causes an increase in urine production. Ingested fluids increase the body’s circulating plasma and thus increase the volume of urine excreted.
Terms to know:
Anuria- Inability to produce urine
Dysuria- Pain or burning during urination
Frequency- voiding at frequent intervals. Less than 2 hours apart
Urgency- Feeling of need to void immediately.
Hematuria- Blood tinged urine. (Results from irritation to bladder and urethral mucosa)
Nocturia- Excessive urination at night.
Oliguria- Diminished capacity to form urine. (Diminished urinary output relative to intake. Usually 400ml/24hr.)
Proteinuria- The presence of large proteins in the urine. It is a sign of glomeluar injury.
Polyuria- An excessive/large output of urine.
Retention- Accumulation of urine in the bladder, with inability of bladder to empty completely.
The surgical formation of a urinary diversion temporarily or permanently bypasses the bladder and urethra as the exit routes for urine. Permanent urinary diversions may be needed in the client with cancer of the bladder. The client with a urinary diversion has a stoma (artificial opening) of the bladder.
Phenazopyridine (Pyridium) colors the urine bright orange to rust; amitripyline causes a green or blue discoloration, whereas levodopa may discolor the urine to brown or black.
Procedures such as an intravenous pyelogram may require that the client limit fluids before the test.
Alterations in Urinary Elimination:
Urinary retention is the marked accumulation of urine in the bladder as a result of the inability of the bladder to empty.
As retention progresses, retention with overflow may develop. Pressure in the bladder builds to a point where the external urethral sphincter is unable to hold back urine. The sphincter temporarily opens to allow a small volume of urine (25 to 60ml) to escape. As urine exits, the bladder pressure falls enough to allow the sphincter to regain control and close. With retention overflow the client voids small amounts of urine 2 or 3 times an hour with no real relief of discomfort. *The nurse should be aware of I&O and frequency.
Urinary Tract Infections:
The most common hospital-acquired (nosocomial) infection in the U.S., accounting for 40% of the total is UTI’s
Although several different microorganisms may cause UTI’s, Escherichia coli remains the most common causative pathogen, responsible for 80% of uncomplicated infections.
Clients with lower UTI’s complain of dysuria or pain and burning during urination. Irritation to the bladder and urethral mucosa results in blood-tinged urine also known as hematuria. If infection spreads to the upper urinary tract (kidneys-pyelonephritis) flank pain, tenderness, fever, and chills are common.
This is the involuntary loss of urine that is sufficient to be a problem. It may be temporary or permanent. Leakage of urine may be continous or intermittent. Urinary incontinence can be identified as functional, overflow, reflex, stress, or urge.
A urinary stoma to divert the flow of urine from the kidneys directly to the abdominal surface is created for several reasons (e.g. cancer of the bladder, trauma, radiation injury to the bladder, fistulas, and chronic cystitis.) Such a urinary diversion may be temporary or permanent.
Nursing Process and Alterations in Urinary Function:
Nursing History: The nursing history includes a review of the client’s elimination patterns and symptoms of urinary alterations and an assessment of other factors that may be affecting the ability to urinate normally.
Patterns of Urination: RN asks about daily voiding patterns, including frequency and times of day, normal volume at each voiding, and any recent changes.
Symptoms of Urinary Alterations:
All symptoms are covered that are listed as terms to know above. If client answers yes to any the RN should note what the patient does when they occur.
Factors Affecting Urination: RN summarizes factors in the client’s history that is pertinent such as age, environmental factors, medication, muscle tone etc.
Skin and mucosal membranes: The RN assesses the condition of the skin. Problems with urinary elimination are often associated with fluid and electrolyte disturbances. By assessing skin turgor and the oral mucosa the RN assesses the client’s hydration status. Urinary incontinence increases the risk of skin breakdown.
Kidneys: If the kidneys become infected or inflamed, flank pain typically develops.
Bladder: Bladder should not be able to be felt. If it is felt it is either swollen or distended b/c it may be full of urine. Percussion of a full bladder yields a dull percussion note.
Urethral Meatus: RN assesses for discharge, inflammation, and lesions.
Assessment of Urine
Characteristics of Urine: The RN will inspect urine for color, clarity, and odor.
Color: Normal urine ranges from a pale, straw color to amber, depending on its concentration. Urine is usually more concentrated in the morning.
Odor: Urine has a characteristic odor. The more concentrated the urine, the stronger the odor. Fruity or sweet smelling urine occurs from acetone or acetoacetic acid (by-products of incomplete fat metabolism) seen with diabetes mellitus or starvation.
Common Urine Test:
Urinalysis-The lab performs urinalysis on a specimen obtained by any of the previously described methods. Table 44-3 lists normal values:
Specific Gravity is the weight or degree of concentration of a substance compared with an equal volume of water.
Common Responsibilities of RN before Diagnostic Examination of the Urinary System:
-Obtain a signed consent form (if agency policy)
-Assess client for history of shellfish (iodine) allergy, which predicts allergy to dye commonly used.
-Administering bowel cleansing medications (check agency policy)
-Ensuring client receives appropriate pretest diet (clear liquids or NPO) as needed.
Common post procedure actions:
-Observing characteristics of urine. (color, clarity, and presence of blood.)
Some Common Nursing Diagnosis of clients with urine elimination alterations:
Disturbed body image
Urinary incontinence (functional, reflex, stress, urge)
Pain (acute, chronic)
Risk for infection
Self-care deficit, toileting
Impaired skin integrity
Impaired urinary elimination