Principles of elimination management
Micturition and catheterization
Learning outcomes
Having read this chapter, the reader should be able to:
Care of the urinary tract, supporting normal micturition, or using a catheter is an important aspect of care for the childbearing woman. This chapter reviews the factors that influence micturition, the direct effects of childbearing on the urinary tract, the safe use of bedpans, urinary catheterization, and correct (short-term) indwelling catheter care.
Micturition
Micturition is the voiding of urine from the bladder via the urethra. It requires a correctly functioning renal system as well as coordination between the brain and the nervous system. Inability (for whatever reason) to pass urine is an acute emergency, acute urinary retention is very painful and can cause complications such as renal failure. The urinary system consists of the bladder (a pelvic organ but displaces out of the pelvis when full), two ureters that connect the bladder to the kidneys, two kidneys that (among other things) are responsible for urine formation and filtration and one urethra that carries urine out of the body from the bladder. The bladder fills at approximately 0.5 mL/kg/hr, the sensation of needing to empty the bladder occurs in adults at a 200–400 mL volume. An adult normally voids 800–2000 mL per day. An understanding of fluid balance (Chapter 48) is also fundamental to appreciating elimination care.
Various factors influence micturition, these include:
• personal habits: distraction (e.g. reading), privacy, time, etc.
• poor muscle tone due to damage or increasing age
• pain
• position
• disease
• obstruction: e.g. compression from the enlarging uterus, presenting part, faecal impaction
• damage to the nervous pathway due to trauma, disease, or age
• surgery
• childbirth (discussed below) (Dolman 2007), particularly poor bladder care in labour (Blackburn 2013)
Changes related to childbirth
Pregnancy
During pregnancy, a number of structural and functional changes occur within the renal system, some of which continue into the postnatal period. Blackburn (2013) summarizes the changes, some of which are discussed below.
Early in pregnancy there is an increase in blood flow to the kidneys, this results in an increase in urine production (and therefore voids per day) and an increase in the ability of the kidneys to remove products of metabolism from the circulation (Doyle & Birch 2011). Also during the first trimester, the renal calyces, renal pelvis and ureters begin to enlarge, resulting in physiological hydroureter and hydronephrosis becoming more pronounced during the second half of the pregnancy. During the last trimester, the enlarging uterus displaces the ureters laterally; they elongate, becoming more tortuous. The volume of the ureters increases, possibly up to 25 times, resulting in up to 300 mL of urine being stored in the ureters (Blackburn 2013). This has implications for the accuracy of 24-hour urine collections and increases the risk of urinary tract infection (UTI).
Progesterone relaxes the smooth muscle of the bladder, resulting in decreased tone, oestrogen predisposes vesicourethral valve incompetence (and therefore reflux of urine) and the glomerular filtration rate increases by 40–60% (Blackburn 2013). Bladder capacity doubles by term, holding up to 1000 mL. The bladder mucosa becomes more oedematous, predisposing it to trauma or infection. McCormick et al (2008) cite that the incidence of UTI in pregnancy is 8%. NICE (2008) suggest all women should be routinely offered midstream specimen of urine (MSU) screening in early pregnancy (initial booking visit) to screen for asymptomatic bacteriuria. UTI in pregnancy affects morbidity and can lead to premature rupture of membranes and preterm labour (SIGN 2012).
The enlarging uterus in the first trimester compresses the bladder, increasing the desire to micturate, resulting in urinary frequency. During the second trimester, the bladder is displaced upwards, allowing bladder capacity to return to normal. However, during the third trimester, pressure from the presenting part, particularly following engagement, can once again result in urinary frequency or stress incontinence. As the bladder is displaced into the abdomen the urethra is elongated and bladder emptying is affected. Nocturia may also occur during pregnancy due to increased excretion of sodium and water occurring when the woman lies down (Blackburn 2013).
Labour
Pressure may be exerted on the sacral plexus by the presenting part during its descent through the pelvis, resulting in increased frequency or retention of urine; this is contributed to by carrying the fetus in an occipitoposterior position.
Retention of urine occurs when the pressure on the sacral plexus results in inhibition of impulses. The bladder fills but there is no associated desire to void urine, compounded by the distension-inhibiting nerve receptors within the bladder wall. Pressure from the descending presenting part is exerted on the bladder and urethra, particularly at their junction. The resulting compression prevents the passage of urine, even with the desire to void. Lack of privacy and poor posture also contribute to retention of urine. Women should be encouraged to void urine every 1–2 hours during labour to minimize these risks, and particularly at the onset of second stage. The bladder is displaced upwards in labour making it physiologically an abdominal organ. This means that palpation of the bladder is an unreliable sign of the presence of urine (Doyle & Birch 2011).
Decreased awareness of the need to void urine occurs if regional anaesthesia is used (e.g. epidural or pudendal block), as the drugs temporarily block the nerves supplying the bladder.
A full bladder may be traumatized in labour and may also affect the course of labour in several ways:
• delayed descent of the presenting part (Simkin & Ancheta 2011)
• reduced efficiency of uterine contractions (Walsh 2004) and therefore delayed cervical dilatation. May worsen a postpartum haemorrhage (PPH), preventing the uterus contracting efficiently (Begley 2014)
• increased/unnecessary pain (Simkin & Ancheta 2011)
• dribbling of urine during expulsive second-stage contractions (Verralls 1993)
Postnatal period
During the early postnatal period, a marked diuresis occurs. Between the second and fifth postnatal days, up to 3000 mL of urine may be produced daily, with 500–1000 mL being voided at a time (Blackburn 2013). Proteinuria may be evident as a result of autolysis (Abbott et al 1997). The structural changes that occurred during pregnancy slowly return to normal during the puerperium, although in some women this may take longer (up to 16 weeks).
Women should pass urine within 6 hours following delivery (Blackburn 2013). However, some women may experience a delayed sensation to void urine. The risk of partial or complete inability to void urine is increased in the presence of:
• trauma to the bladder or urethra – sometimes in the form of oedema or sphincter spasm
• haematoma formation within the genital tract (Blackburn 2013).
Incomplete emptying of the bladder and urinary stasis increase the risk of urinary tract infection. NICE (2014a) advocate that if no void has occurred 6-hours post-delivery measures should be taken to assist (see below). If urine has still not been passed, the bladder should be assessed and catheterization considered. A displaced uterus is often caused by a full bladder.
Stress incontinence may also occur following delivery as a result of damage to the perineal branches of the pudendal nerves (Abbott et al 1997). If this persists beyond the puerperium, medical attention should be sought.
An important part of the midwife’s role and responsibilities is record keeping, especially if the woman is experiencing difficulty with micturition (dysuria). Postnatally particularly, records should show the time, amount of urine passed, and the frequency, with any symptoms associated with dysuria, e.g. stinging.
The baby
A baby’s bladder is an abdominal organ, it being too large for the small pelvis to accommodate it. Consequently a full bladder can compress the diaphragm and affect respiration. For the baby, micturition is an involuntary process with no control over when and where to void urine. Babies usually pass urine within the first 48 hours of life, 95% of them in the first 24 hours (Blackburn 2013). It is important the midwife records that the baby has passed urine following birth and helps the parents to understand the expected urine output in the days that follow (Chapter 38). Neonates from mothers who received magnesium sulphate are at higher risk of urinary retention. Urinary output is variable, depending on gestational age, fluid and solute intake, the ability of the kidneys to concentrate urine and perinatal events. It increases during the neonatal period, e.g. breastfed babies pass around 20 mL of urine during the first 24 hours, increasing to 200 mL by the 10th day (Johnston et al 2003).
Facilitating normal micturition (adults)
Given that the changes to the urinary tract and the effects of childbirth are significant, the midwife has a responsibility to ensure good bladder care for all women. Wherever possible the woman should be encouraged to void normally, namely, on the toilet. However, at times the use of a bedpan is indicated and urinary catheters, in particular circumstances, are also used. Catheterization of the bladder is not without risks and so should be used only when there is a clinical indication. The midwife should facilitate normal micturition wherever possible; three factors influence this:
Stimulating the micturition reflex
Position
Use of sensory stimuli
• Thompson (2015) recommends the sound of running water, using the power of suggestion. If the woman is embarrassed by the noise made during micturition, particularly if others are close by, the sound of running water may mask the sound of her passing urine.
• Stroking the inner aspect of the woman’s thigh, placing her hand in warm water, or offering a drink may stimulate the sensory nerves to stimulate the micturition reflex (Thompson 2015).
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