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 nephron

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 functions of the kidneys are to maintain homeostasis by:

In carrying out these functions the kidneys excrete urine.

Formation of urine

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.


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:


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.


Term Definition
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

Problems with urination include those outlined below.


Incontinence is the inability to control the excretion of urine and may result from a variety of local or generalised conditions that include:


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.

Measures to induce micturition

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:

Nursing actions that may be implemented to induce micturition include:

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:


Action Rationale
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

* This procedure is only performed by an RN or a medical officer

If the catheter is to be indwelling, the following are also needed:

Feb 12, 2017 | Posted by in NURSING | Comments Off on URINARY ELIMINATION
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