Postpartum overdistention of the bladder and urinary retention can lead to which complication?

Overview

Introduction
Bladder care is an important aspect of management in the postpartum period. Postpartum voiding dysfunction occurs in a significant number of women, which can potentially cause permanent damage to the detrusor muscle and long-term complications when left undetected or untreated. Hospitals have varying guidelines for postpartum bladder care. In the absence of a universal protocol, many cases are missed or mismanaged. It is important to consider the implications of poor bladder care in the puerperal period and to try and avoid such cases occurring as far as possible.

Definitions
Urinary retention is a complaint of the inability to pass urine despite persistent effort.1 Acute urinary retention is defined by the International Continence Society as a painful, palpable, or percussable bladder, with the patient unable to pass any urine when the bladder is full,2 although it should be recognised that pain may not be present in the post partum woman especially following epidural analgesia.

Post-partum urinary retention (PUR) also known as insidious urinary retention after vaginal delivery or puerperal urinary retention is a relatively common condition. Traditionally post-partum urinary retention is described as the absence of spontaneous micturition within six hours of vaginal delivery,3 however, there is no research base to this definition.

Acute, also know as overt, retention presents with ‘the sudden onset of the inability to void’ leaving a significant amount of residual urine in the bladder. Post-void residual (PVR) is ‘the volume of fluid remaining in the bladder immediately following the completion of micturition’.2 In the literature, varying volumes of residual urine are regarded as significant ranging from 40ml-200ml.4 These ranges may reflect the timing and methods used to measure PVR. They are most accurate if measured immediately, within 60 seconds of micturition.5 A recent study using transvaginal ultrasound as a method of measuring immediate PVR suggest an upper limit of normal of 30ml.6 An isolated finding of a raised PVR requires confirmation before being considered significant.

Chronic retention of urine is defined as a non-painful bladder, where there is a chronic high PVR.6 Postpartum chronic, also known as covert, retention is considered when there is PVR of over 150mls or more. It is usually a self-limiting condition, which often resolves within a week. Patients with covert bladder retention may present with frequency, passing less than 150ml with feeling of incomplete emptying.

Incidence
The reported incidence of postpartum voiding dysfunction varies due to inconsistencies in the definitions and method of diagnosis. Furthermore, figures may also vary depending on whether studies focus on acute or chronic retention. Estimated ranges of incidence vary from 0.05% to 37%.7 It would be reasonable to quote that 10-15% of women have voiding dysfunction to some degree and for some time following delivery.

Up to 5% of these women may have significant and longer lasting dysfunction, which if not recognised in the early peripartum period, may lead to bladder distension and overflow incontinence with significant long-term bladder dysfunction.

Current Practices
There are no set national guidelines for the management of postpartum bladder care as yet. In the guideline for “Routine Postnatal Care of Women and their Babies” produced by the National Institute of Clinical Excellence (NICE), it is recommended that conservative measures be taken to encourage those women that have been unable to void within six hours of delivery. If unsuccessful, bladder volume should be assessed and the patient should be catheterised if necessary. In the Royal

College of Obstetrics and Gynaecology (RCOG) Green Top Guidelines it is recommended that a woman who is post instrumental delivery and has had a spinal anaesthetic or an epidural that has been topped up for a trial, may be at increased risk of retention and should have an indwelling catheter for at least 12 hours post-delivery.

There is little evidence on the management of postpartum urinary retention and many hospitals have implemented their own postpartum bladder care protocols. Zaki et al investigated postpartum bladder care by means of a postal questionnaire in 189 maternity units in England and Wales. The results of which showed huge variations in diagnosis, management and compliance with the RCOG recommendations on postpartum bladder care.8

Risk Factors
Although it is not possible to accurately predict who will develop post partum urinary retention various risk factors are suggested.9, 10

Risk factors include:

• Nulliparous women,
• Prolonged labour, especially a prolonged second stage,
• Assisted/instrumental delivery.
• Perineal injury.
• Caesarean section
• Regional analgesia

Many women with voiding dysfunction peri and postpartum may have no apparent risk factors and all women should be regarded as at risk and managed accordingly.

Pathophysiology
The pathophysiology of postpartum urinary retention is not clearly understood but various mechanisms have been suggested.

The bladder is a hormone-responsive organ and it’s functions may be subject to the fluctuation of hormones during pregnancy and in the postpartum period.4 The postpartum bladder is hypotonic, remaining so for a number of days post delivery. Pregnancy causes reduced muscle tone in the bladder from the third month with the bladder gradually increasing in capacity as the pregnancy progresses.11

This may be as a result of physiological hormonal changes such as elevated progesterone levels during normal pregnancy. In the absence of the weight of the pregnant uterus limiting the size of the bladder, as well as possible trauma to the bladder, pelvic floor muscles and nerves during delivery, the bladder becomes susceptible to retention.

One of the most common causes of postpartum urinary retention is the use of regional anaesthesia due to afferent neural blockade which supresses the sensory stimuli from the bladder to the pontine micturition centre. As a result, the reflex mechanism that induces micturition is blocked which may result in reduced contractility of bladder and urinary retention.12

Urinary retention may also be the result of nerve injury during delivery. A number of studies have shown that the pudendal nerve, with afferent nerve branches (S2-4) supplying the bladder, is damaged during pelvic surgery and vaginal delivery. Using electrophysiological tests, some studies have shown the damaging effect of a vaginal delivery to the pudendal nerve. There is a significant increase in pudendal nerve terminal motor latencies, which may take a few months to recover post delivery.13-15

This is thought to be due to pelvic floor tissue stretching during delivery resulting in pudendal nerve damage. Both instrumental delivery and prolonged labour can be predisposing factors to this damage.

Another possible explanation of postpartum urinary retention is a transient phenomenon caused by tissue oedema around the urogenital area, resulting in a transient mechanical obstruction to urine outflow. The tissue oedema could be due to a prolonged labour process with compression of the fetal presenting part onto the birth canal or other factors such as instrumental/assisted delivery or extensive vaginal and perineal laceration. Within days of delivery, as the tissue oedema improves, the urinary retention gradually returns to normal.

It is well known that in a non-pregnant population, chronic changes in the detrusor muscle can result from a single episode of massive over-distension. The bladder can retain up to a litre of urine, although residual volumes of between 500ml and 800ml are enough to stretch the bladder walls and cause detrusor damage. Significant bladder over-distension can lead to denervation and detrusor atrophy. This may result in long-standing voiding dysfunction with persistent urinary retention and overflow incontinence.

Symptoms
Symptoms of acute retention are much more obvious as women are not able to void and suffer an associated painful bladder.

However, the pain should not be misdiagnosed as caesarean wound pain.

Symptoms of incomplete empting/ chronic retention of the bladder in post partum period include:

• Difficulty in initiating a void after birth
• The feeling of bladder fullness after voiding
• Dribbling of urine post micturition
• Frequency with small void volumes
• Poor flow rate with straining to void
• Nocturia >2 times which is not related to baby feeding

It needs to be emphasised that symptoms may be masked or a patient may be asymptomatic, especially if they have had an epidural. In some cases they may have overflow incontinence due to bladder over distension, displaying symptoms of stress incontinence.

Diagnosis
Diagnosis of postpartum urinary retention can be difficult especially if a woman is asymptomatic. In order to diagnose urinary retention, the post void residual volume needs to be determined. Initially women are asked to void and immediately after PVR should be measured. This is important as a long delay in measurements can give an inaccurate PVR due to renal diuresis.

Bladder distension may be felt by abdominal palpation but this is inaccurate and bladder volumes of less than 300ml may not be identified.

Catheterisation is the most accurate PVR measurement in the first few weeks of the post partum period. Catheterisation can be uncomfortable and potentially increases the risk of urinary tract infection. Most authors recommend in/out catheterisation as an ideal method.

Bladder scanning is a popular non-invasive method of measuring PVR. Many question the accuracy of scanning in post-natal women. A standard bladder scanner may measure echogenic uterine debris as bladder volume. However, some authors believe that ultrasound assessment is accurate, even in the post partum period, as the bladder maintains an ellipsoid shape.16 It may be logical to use a bladder scanner as a guide for the amount of post-void residual. If a significant residue is measured by ultrasound then it should be confirmed with an in/out urethral catheter.

Management
The recommendations for management in the literature vary between different authors. Summarised below are the most common suggestions.

1. Intrapartum
The most important part of management of PUR is prevention which starts with the labouring woman. Voiding should be encouraged every three hours whilst in labour and if unable to void, there should be a low threshold for catheterisation. Women should also be catheterised if the bladder is palpable or there is a sensation of incomplete empting.

Women who have had an epidural for normal labour, especially with a heavy block, should be offered an indwelling catheter that should remain insitu for a minimum of six hours postpartum or until full sensation has returned. A catheter balloon should be deflated or removed prior to pushing to reduce the risk of urethral damage with extrusion of the inflated catheter during delivery of the baby.

Women who have had spinal anaesthesia or epidural anaesthesia that has been topped up for a trial of Instrumental delivery with or without Caesarean section are at increased risk of retention and should have an indwelling catheter which should be kept in place for at least 12 hours following delivery to prevent asymptomatic bladder overfilling.

2. Postpartum
In the postpartum woman the timing and volume of the first voided urine should be monitored. Voiding should be encouraged every 2-3 hours in the immediate postpartum period. Women should not be left for over 6 hours without voiding or being catheterised post delivery. A fluid balance chart can be helpful in monitoring input and output, especially in the first 24 hours post delivery.

Normal sensation, difficulty initiating micturition, sensation of incomplete emptying, volume voided and timing and frequency of voids needs to be documented in the clinical records and PUR diagnosed as explained previously.

Measures to aid voiding
Yip et al advocates conservative, ‘helping measures’, such as oral analgesia, helping the patient mobilise and offering them privacy as well as techniques such as bathing in a warm bath and immersing their hands in cold water.4 It is suggested that these practical measures, which hold low risk to the postpartum woman, may be attempted prior to less conservative management. The importance of preventing constipation should not be forgotten.

What to do if PUR is suspected or confirmed?
If the volume voided is less than 150ml or the residual volume assessed by ultrasound is more than 150ml the patient should be managed with in/out catheterisation. With the urine residue accurately measured, an arbitrary residual volume of 150ml may imply a degree of dysfunction. At this stage a fluid balance chart is mandatory.

Most authors recommend that if the patient is not able to void well after a further six hours, an indwelling catheter, such as Foley’s catheter, should be inserted and remain so for 24/48 hours. Some even advocate for it to remain insitu for one week.7 A midstream or catheter sample of urine needs to be sent for microbiology to rule out an infection. If positive, the patient should be treated with appropriate antibiotics as per local guidelines. However, as there is high risk of infection prophylactic antibiotics is advocated.17

In the absence of infection and a failed trial without catheter or persistent high PVR, intermittent self-catheterisation (ISC) or another indwelling catheter is recommended. The volume of urine drained initially can be a predictor of repeat catheterisation. A study by Burkhart et al found that if the initial volume of PVR was less than 700 in their cohort of patients, none required repeat catheterisation. However, if there was over a litre PVR then 20% required repeat catheterisation.18

Some obstetric units support the use of suprapubic catheterisation rather than ISC. This is more justified for women who have had a repeated failed trail with an in/out catheter or massive retention of urine with possible irreversible bladder damage.

There is no evidence that pharmacological interventions have any place in the management of PUR .

Complications and long-term implications
Early detection of urinary retention is very important as the over-distended bladder may result in irreversible bladder damage. There is very limited data on short sequelae of PUR. The data available suggests that the majority of PUR are self-limiting cases with a return to normality within the first week post partum. Postpartum urinary retention that remains unrecognised or poorly managed may lead to long-term voiding difficulty with recurrent urinary tract infection and ureteric reflux. This may lead to upper urinary tract damage and even renal failure. There are also case reports of bladder ruptures in a few unrecognised cases. As a result, long-term follow up for patients is always advisable.

Conclusions
Intrapartum bladder care and the prevention and management of postpartum urinary retention are of great clinical importance. It is far more beneficial to prevent acute bladder distension by taking reasonable measures, where possible, to avoid it, than to treat cases once symptoms have developed. The implementation of regular screening protocols is advisable as cases recognised, diagnosed and treated promptly can prevent long term, irreversible damage to the detrusor muscle that can have a permanent impact on a woman’s quality of life.

References

1. Haylen BT, de Ridder D, Freeman RM, Swift SE, Berghmans B, Lee J, et al. An International Urogynecological Association (IUGA)/International Continence Society (ICS) joint report on the terminology for female pelvic floor dysfunction. International urogynecology journal. 2010;21(1):5-26. Epub 2009/11/26.
2. Abrams P, Cardozo L, Fall M, Griffiths D, Rosier P, Ulmsten U, et al. The standardisation of terminology of lower urinary tract function: report from the Standardisation Sub-committee of the International Continence Society. Neurourology and urodynamics. 2002;21(2):167-78. Epub 2002/02/22.
3. Saultz JW, Toffler WL, Shackles JY. Postpartum urinary retention. The Journal of the American Board of Family Practice / American Board of Family Practice. 1991;4(5):341-4. Epub 1991/09/01.
4. Yip SK, Sahota D, Pang MW, Chang A. Postpartum urinary retention. Acta obstetricia et gynecologica Scandinavica. 2004;83(10):881-91. Epub 2004/09/30.
5. Haylen BT, Lee J. The accuracy of post-void residual measurement in women. International urogynecology journal and pelvic floor dysfunction. 2008;19(5):603-6. Epub 2008/02/28.
6. Haylen BT, Lee J, Logan V, Husselbee S, Zhou J, Law M. Immediate postvoid residual volumes in women with symptoms of pelvic floor dysfunction. Obstetrics and gynecology. 2008;111(6):1305-12. Epub 2008/06/03.
7. Lim JL. Post-partum voiding dysfunction and urinary retention. The Australian & New Zealand journal of obstetrics & gynaecology. 2010;50(6):502-5. Epub 2010/12/08.
8. Zaki MM, Pandit M, Jackson S. National survey for intrapartum and postpartum bladder care: assessing the need for guidelines. BJOG : an international journal of obstetrics and gynaecology. 2004;111(8):874-6. Epub 2004/07/24.
9. Carley ME, Carley JM, Vasdev G, Lesnick TG, Webb MJ, Ramin KD, et al. Factors that are associated with clinically overt postpartum urinary retention after vaginal delivery. American journal of obstetrics and gynecology. 2002;187(2):430-3. Epub 2002/08/24.
10. Ching-Chung L, Shuenn-Dhy C, Ling-Hong T, Ching-Chang H, Chao-Lun C, Po-Jen C. Postpartum urinary retention: assessment of contributing factors and long-term clinical impact. The Australian & New Zealand journal of obstetrics & gynaecology. 2002;42(4):365-8. Epub 2002/10/31.
11. Iosif S, Ingemarsson I, Ulmsten U. Urodynamic studies in normal pregnancy and in puerperium. American journal of obstetrics and gynecology. 1980;137(6):696-700. Epub 1980/07/15.
12. Teo R, Punter J, Abrams K, Mayne C, Tincello D. Clinically overt postpartum urinary retention after vaginal delivery: a retrospective case-control study. International urogynecology journal and pelvic floor dysfunction. 2007;18(5):521-4. Epub 2006/08/24.
13. Sultan AH, Kamm MA, Hudson CN. Pudendal nerve damage during labour: prospective study before and after childbirth. British journal of obstetrics and gynaecology. 1994;101(1):22-8. Epub 1994/01/01.
14. Tetzschner T, Sorensen M, Lose G, Christiansen J. Pudendal nerve recovery after a non-instrumented vaginal delivery. International urogynecology journal and pelvic floor dysfunction. 1996;7(2):102-4. Epub 1996/01/01.
15. Tetzschner T, Sorensen M, Lose G, Christiansen J. Pudendal nerve function during pregnancy and after delivery. International urogynecology journal and pelvic floor dysfunction. 1997;8(2):66-8. Epub 1997/01/01.
16. Yip SK, Sahota D, Chang AM. Determining the reliability of ultrasound measurements and the validity of the formulae for ultrasound estimation of postvoid residual bladder volume in postpartum women. Neurourology and urodynamics. 2003;22(3):255-60. Epub 2003/04/23.
17. Harris RE. Postpartum urinary retention: role of antimicrobial therapy. American journal of obstetrics and gynecology. 1979;133(2):174-5. Epub 1979/01/15.
18. Burkhart FL, Porges RF, Gibbs CE. Bladder Capacity Postpartum and Catheterisation. Obstetrics and gynecology. 1965;26:176-9. Epub 1965/08/01.

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