Chapter 32 URINARY ELIMINATION
The urinary system is responsible for maintaining homeostasis as well as eliminating some waste products of body metabolism. Many factors can affect voiding and result in alteration to this system. Nursing management of clients with urinary elimination disorders requires sensitivity and maintenance of client dignity as well as specific nursing skills.
It is so embarrassing going to a urologist and having him examine me. The tests were even worse, as I had to have X-rays taken while I was passing urine. The nursing staff were sensitive and caring; one in particular, Joan, really helped me through what is still one of the worst experiences of my life.
As a result of cellular metabolism, various waste products are produced. The urinary system plays a major role in the elimination of metabolic waste products and toxic substances and in regulating the rates of elimination of water and electrolytes from the body. By regulating the volume of the body fluid, the urinary system helps maintain blood pressure and the electrolyte content and pH of the blood. Because of this role, the kidneys are considered to perform one of the major homeostatic functions of the body. The urinary system (Figure 32.1) consists of the kidneys, which filter blood; the ureters, which transport urine to the bladder; and the bladder, which stores the urine until it is excreted through the urethra.
The kidneys are two bean-shaped organs situated behind the peritoneum on the posterior wall of the abdominal cavity, on either side of the vertebral column. The kidneys extend from about the twelfth thoracic vertebra to the third lumbar vertebra. The right kidney is situated a little lower than the left because of the space occupied by the liver.
A kidney (Figure 32.2) weighs 120–170 g, is 10–13 cm in length, 5–6 cm wide and 3–4 cm thick. The kidneys are protected and supported by renal fascia and by layers of perirenal fat. Three layers of tissue surround each kidney:
A deep indentation, the hilus, is present on the medial border of the kidney. It is from the hilus that the ureter emerges. The renal vein and the renal artery also pass through the hilus. The renal artery branches from the aorta to transport oxygenated blood to the kidney. The renal vein transports deoxygenated blood from the kidney to the inferior vena cava.
Each kidney contains at least 1 million nephrons, together with their collecting tubules or ducts. The nephron is the functional unit of the kidney. Each nephron (Figure 32.3) is composed of a vascular and tubular system that allows for the formation of urine. The nephrons are located in the renal tissue, with most in the cortex and some extending deep into the medulla of the kidney. A nephron consists of several anatomically distinct regions:
Division of the efferent vessels (the arterioles that carry blood away from the capillaries) forms a second set of capillaries. The veins that collect blood from these capillaries unite to eventually form the renal vein.
The formation of urine occurs in three phases: simple filtration, selective reabsorption, and secretion. Filtration occurs through the semi-permeable walls of the glomerulus and Bowman’s capsule. Blood enters the glomerular capillaries under relatively high pressure and is forced into the lumen of the Bowman’s capsule. Water and small molecules pass through the semi-permeable walls, while blood cells, plasma proteins, and other large molecules are unable to pass through healthy capillary walls. The resultant glomerular filtrate is thus plasma minus the plasma proteins.
The major factor assisting filtration is the difference between the blood pressure in the glomerulus and the pressure of filtrate in the glomerular capsule. A capillary hydrostatic pressure of about 70 mmHg builds up in the glomerulus because the calibre of the efferent arteriole is less than that of the afferent arteriole. The capillary pressure is opposed by the lower osmotic pressure of the blood and the lower filtrate hydrostatic pressure in the glomerular capsule. The amount of dilute filtrate formed in 24 hours is about 100–150 L. The amount actually excreted as urine in 24 hours is about 1–1.5 L, so most of the volume of the filtrate is reabsorbed.
Selective reabsorption occurs as the filtered fluid flows through the renal tubules. During this phase, substances such as glucose, amino acids, hormones, mineral salts, vitamins and most of the water are reabsorbed into the blood. Not reabsorbed are some of the water, substances in excess of body needs, and wastes, including drugs and toxic substances. Thus selective reabsorption helps to maintain fluid and electrolyte balance and blood pH.
Secretion is the process by which substances such as hydrogen and potassium ions move from the blood of the peritubular capillaries or from the tubule cells into the filtrate to be eliminated in urine. The fluid (urine) that flows from the collecting tubules contains substances not needed by the body. Urine flows into the pelvis of the kidneys for transport, via the ureters, to the urinary bladder.
Urine is a clear, amber-coloured slightly acidic fluid composed of 96% water, 2% urea and 2% mineral salts, uric acid and creatinine. Urea, uric acid and creatinine are waste products of protein metabolism. Mineral salts are excreted in the urine to maintain their normal level in the blood and to regulate the pH of the blood.
The ureters are two narrow, thick-walled muscular tubes, 25–30 cm long, which originate in the renal pelvis of each kidney. They pass down the posterior abdominal wall and into the pelvic cavity to enter the posterior base of the bladder. The ureters enter the bladder at an oblique angle so that, as the bladder fills and contracts, urine is not forced back towards the kidneys. The walls of the ureters consist of an outer fibrous coat that is continuous with the renal capsule, a middle coat of involuntary muscle, and a lining of transitional epithelium. The function of the ureters is to carry urine from the kidneys to the bladder, by means of peristaltic action. The involuntary muscle layer in the walls of the ureters contract from 1–5 times per minute to force urine into the bladder.
The urinary bladder is a hollow muscular organ that acts as a reservoir for urine. It sits in the pelvic cavity behind the symphysis pubis. In the female it is in front of the uterus and in the male it sits in front of the rectum. The walls of the bladder consist of:
The trigone of the bladder is a triangle formed by the two ureteric orifices, where the ureters enter the bladder, and the urethral orifice, where the urethra leaves. Below the neck of the bladder lies the striated muscle that constitutes an external sphincter.
The urethra (Figure 32.4) is a muscular tube extending from the neck of the bladder to the external meatus. In the female the urethra is about 2.5–4 cm long and opens at the external urethral orifice in front of the vaginal opening. The external sphincter guards this opening. In the male, the urethra is about 15–20 cm long and opens at the tip of the penis. The male urethra has a double function: it forms a passage for urine as well as semen. It is guarded by an external sphincter immediately below the prostatic portion of the urethra. Near to the bladder, the urethra is lined with transitional epithelium that gives way to squamous epithelium. The function of the urethra is to provide a passage for urine from the bladder, out of the body.
Micturition (or voiding) is the act of passing urine. Urine is carried down the ureters by peristaltic waves, each of which sends a spurt of urine into the bladder. While the normal capacity of the adult urinary bladder is about 450 mL, the bladder is capable of expanding to hold larger amounts. The bladder fills slowly over a period of time and, when it holds about 300–500 mL, a desire to empty the bladder is experienced. A reflex initiated by impulses from stretch receptors in the bladder wall regulates the process of micturition. The sensory neurons transmit the impulses to the spinal cord, where they are relayed to the brain, which in turn stimulates parasympathetic neurons that innervate the bladder wall. When a client is ready to pass urine, these impulses cause the bladder muscles to contract, the urethral sphincters relax and urine is voided into the urethra and excreted. Urine is excreted in amounts of 1–2 L in 24 hours. Micturition is normally under voluntary control by about 2–3 years of age.
Metabolism produces wastes that must be eliminated regularly to maintain effective body function. Observation of urine and the client’s ability to eliminate it provides the nurse with an objective assessment of the client’s elimination status. As a result, appropriate nursing actions may be planned and implemented.
The nurse may be required to collect urine for observation or testing in the ward, or so that a specimen can be sent to the pathology laboratory for analysis. Key aspects related to the collection of urine include:
If urine is to be collected for observation or testing in the ward, the client is requested to void into a clean bedpan or urinal (Figure 32.5). The urine should not be contaminated by faeces or menstrual blood, as a false assessment may result. The urine is transferred from the toilet utensil into a clean container in preparation for observation or testing. (For more detail regarding performing a urinalysis, see Chapter 22.)
Figure 32.5 Positioning a bedpan A: Another method of placing a bedpan is used when the client is unable to help. The client lies on one side and the bedpan is placed firmly against the buttocks B: The nurse pushes down on the bedpan and towards the client C: The client is positioned on the bedpan so that the urethra and anus are directly over the opening
All urine excreted during a timed collection, for example, during a 24-hour period, is collected and sent for laboratory analysis to measure the quantity of various substances present, such as specific hormones. A suggested method of collecting a 24-hour specimen is outlined in Table 22.1.
This method of collection is used to obtain a sample of urine that is not contaminated by microorganisms from outside the urinary tract. The urine is sent to the laboratory to be tested for the presence of microorganisms and their sensitivity to antibiotics. The aim is to collect the middle portion of the stream of urine. A suggested method of collection is outlined in Table 22.2.
A urine collection bag may be used to obtain a specimen from a client who is unable to control the flow of urine, such as an infant or a client who is incontinent, unconscious or confused. A suggested method of collecting a sample of urine using a collection bag is outlined in Table 22.3.
A culture medium is sometimes used when the urine is to be tested for bacteria. Urine is first collected in a sterile container, then a slide containing culture medium is dipped into the urine. The culture slide is returned to its original container and despatched to the laboratory together with the urine in its separate sterile container. This method of collection may be necessary if there is a delay in despatch of the specimen and refrigeration is not practicable.
A catheter specimen of urine is obtained from a client who has an indwelling catheter. The insertion of a catheter for the sole purpose of obtaining a urine specimen is generally avoided because of the risk of introducing microorganisms into the urinary tract. Collecting a specimen from the end of the catheter that is connected to the drainage tubing should be avoided and the urine should be aspirated using a sterile syringe and needle through the sampling port (see Figure 22.1). The recommended method for obtaining a catheter specimen is outlined in Table 22.4.
This procedure is not commonly performed but, when necessary, it is performed by a medical officer, using sterile equipment and aseptic technique. It involves the insertion of a needle through the skin over the suprapubic area into the bladder. A quantity of urine is aspirated, placed in a sterile container and despatched to the laboratory. After this procedure the nurse should observe the puncture site for bleeding, and the urine for the presence of blood.
Stones, or calculi, are insoluble substances formed of mineral salts that may develop in the kidneys. They can range in size from microscopic, through resembling grains of sand or gravel, to several centimetres in diameter. If it is known or suspected that a client has developed renal calculi, careful observation of the urine is achieved by straining it to detect the passage of stones. Any stones collected are sent for laboratory examination, which reveals their exact composition and helps to identify their cause. The urine is strained by pouring it through a fine substance such as gauze or filter paper.
Problems associated with micturition may result from several factors, including a change of routine or environment, or as a consequence of certain disease states. Any alteration in a client’s normal pattern of voiding (Table 32.1) must be recognised and reported immediately, so that appropriate actions can be planned and implemented.
|Anuria||The absence of urine production, or a urinary output < 100 mL/day (< 30 mL/hour)|
|Dribbling||Dribbling of urine from the urethra despite voluntary control of micturition. It may be at the end of micturition or continuous|
|Dysuria||Pain and burning on micturition, usually as a result of an infection or obstruction|
|Frequency||Voiding at frequent intervals, i.e. < 2-hourly|
|Haematuria||The presence of blood in the urine|
|Hesitancy||Difficulty starting micturition|
|Incontinence||The inability to control the passage of urine|
|Nocturia||Excessive or frequent urination at night|
|Oliguria||A decreased urine production resulting in an output < 500 mL/day|
|Polyuria||The excretion of an abnormally large volume of urine|
|Retention||The accumulation of urine in the bladder as a result of being unable to fully empty the bladder|
|Residual urine||The volume of urine remaining after voiding|
|Urgency||The feeling of needing to void immediately|
The term oliguria is used to describe decreased urine output of below 500 mL/day. This condition is caused by fluid and electrolyte imbalances, kidney dysfunction or urinary tract obstruction. Polyuria is the term used to describe the excretion of greatly increased amounts of urine, for example, over 2500 mL/day. It may occur as a result of a large fluid input, diuretic medications, or certain disease states such as diabetes insipidus.
When there is an accumulation of urine in the bladder and the client is unable to void, the condition is referred to as retention of urine. Retention of urine is commonly due to an obstruction of the bladder outlet or urethra, and it may also occur as a result of tension in the urethral sphincter, caused by anxiety or pain. Retention of urine with overflow occurs when the accumulation of urine in the bladder leads to stretching of the urethral orifice and, although small amounts of urine dribble away, the bladder remains full and distended.
CLINICAL INTEREST BOX 32.1 Incontinence and the client with dementia
Frequency of micturition is when a client experiences the need to void more often than normal and commonly voids small amounts of urine each time. This condition is commonly associated with a UTI or may occur as a result of anxiety or stress.
When a client is experiencing difficulty in passing urine, the cause must be identified and treated. Difficulty in passing urine may result from an obstruction to the outflow of urine but may also be caused by other factors such as:
If these actions fail to induce micturition and the client is uncomfortable because of a distended bladder, it may be necessary to implement further actions, such as inserting a urinary catheter. This is ordered by a medical officer and performed by an RN.
A catheter is a tube that is inserted into the bladder to drain urine. It is inserted through the urethra or, less commonly, through a small incision in the suprapubic area. A catheter may be inserted to empty the bladder then removed immediately, or it may be left in the bladder. A catheter that remains in the bladder may either be clamped and released at specified intervals, or connected to tubing and a bag to enable continuous drainage. A catheter that remains in the bladder is referred to as indwelling. A self-retaining catheter is used for this purpose. It has a small balloon that is filled with sterile water after the catheter is inserted, which stops the catheter falling out. Reasons for inserting a urinary catheter include to:
Catheters are made from materials that cause minimal reaction when in contact with body tissues and are available in a variety of styles and sizes. Some of the materials from which catheters are made include: polyvinylchloride (PVC), which softens at body temperature and is commonly used for short-term purposes; silicone elastomer, which is a physiologically inert material causing few local reactions when in contact with body tissue and which can therefore remain in the bladder for long periods; and latex coated with silicone, which is not as inert as silicone, but may remain in the bladder for up to 10 days. Catheters are graded according to the French scale, and the larger the number the larger the lumen of the catheter. Sizes range from 1 to 30 French gauge (Fg), and the size is selected to suit the client’s needs. It is important that a suitable size is selected to avoid leakage of urine around the catheter, or trauma to the urethra or bladder.
The procedure of catheter insertion is called catheterisation and is performed using sterile equipment and aseptic technique. As a catheter can cause trauma to the urethral or bladder mucosa and is a potential source of UTI, it is inserted only when absolutely necessary and only by an RN or a medical officer. Because the male urethra is longer and more curved than the female urethra and catheterisation is often more difficult, male clients are usually catheterised by a health worker skilled in this procedure. A suggested procedure for female catheterisation is outlined in Table 32.2. Nurses should be aware of their role and responsibilities regarding catheter insertion in the workplace. The basic requirements are:
|Review and carry out the standard steps in Appendix 1|
|Ensure adequate lighting||Visualisation of the urethral meatus is essential|
|Place the client in the dorsal position, with knees flexed and separated, and feet slightly apart on the bed||Provides a clear view of the urethral meatus|
|Ensure that the client is adequately draped||Reduces embarrassment|
|Place all the equipment in a convenient location||Facilitates easy access to it throughout the procedure|
|Wash and dry hands. Don gloves and goggles||Prevents cross-infection|
|Use sterile towels to create a sterile field around the genital area||Reduces risk of equipment becoming contaminated during the procedure|
|Cleanse genital area and urethral meatus, wiping from front to back||Reduces risk of introducing microorganisms from the genital/anal area into the urinary tract|
|Before inserting a self-retaining catheter, inflate and deflate the balloon||Necessary to check balloon for leakage before insertion|
|With forceps, hold the catheter about 7 cm from its tip||Assists in controlling the direction of the catheter|
|Dip tip of catheter into the water-based lubricant||Facilitates easier and more comfortable insertion|
|Place distal end of catheter into a sterile receptacle positioned between the client’s legs||Urine will flow into the receptacle, not onto the bed|
|Keeping the client’s labia separated, insert the catheter tip into the urethral orifice. Advance the catheter until 4–7 cm have been inserted||Length of catheter inserted must be in relation to the anatomical structure of the urethra. The average female urethra is about 3.8 cm long|
|If catheter is not to be left in, remove it gently when urine ceases to flow, or the required amount of urine has drained||Catheters are not left in any longer than necessary, and are removed gently to avoid discomfort|
|If a self-retaining catheter is being used, inflate the balloon, having first ensured that the catheter is draining adequately||Inflated balloon keeps the catheter in the bladder. Inadvertent inflation with the balloon in the urethra causes trauma and pain|
|Connect the indwelling catheter to the drainage bag and support the bag in a holder at the side of the bed. Alternatively, a clamp is placed on the end of the catheter||Urine flows from catheter, along the tubing and into the bag. Intermittent drainage may be prescribed|
|Attach the catheter to the client’s inner thigh with hypoallergenic tape, and pass the catheter over the thigh||Prevents in–out movement of the catheter and prevents tension on the urethra|
|Position the tubing so that it is not obstructed by the client’s weight or by tight bedclothes||Avoids blocking the flow of urine through the tubing|
|Remove excess lubricant from the client’s genital area. Replace bedding and assist client into a comfortable position||Helps promote comfort|
|Remove and attend to the equipment in the appropriate manner. Wash and dry hands||Prevents cross-infection|
|Document the procedure, including the amount of water instilled into the balloon, and colour and characteristics of the urine||Appropriate care can be planned and implemented. When the catheter is to be removed, it is important that the water is first withdrawn and the balloon deflated to prevent trauma to the urethra|