Obstetric anal sphincter injuries are serious complications of vaginal birth. Some of the known risk factors for developing obstetric anal sphincter injuries are nulliparity, increased maternal age at first birth and instrument assisted vaginal birth (Gurol-Urganci et al, 2013). The rate of obstetric anal sphincter injuries for primiparous women in the UK has increased from 1.8% to 5.9% between 2000 and 2012 (Gurol-Urganci et al, 2013). The current incidence of obstetric anal sphincter injuries is 5%, meaning 1 in 20 primiparous women will be affected (Royal College of Obstetricians and Gynaecologists (RCOG), 2015). The increasing incidence of obstetric anal sphincter injuries is leading to significant morbidity in otherwise healthy women (Darmody et al, 2020). Darmody et al (2020) commented on the importance of midwifery care, not only in avoiding obstetric anal sphincter injuries and supporting labouring women, but in providing empathetic care to those affected, acknowledging how obstetric anal sphincter injuries can affect daily life.
One significant long-term outcome of obstetric anal sphincter injuries is anal incontinence. This is defined as the involuntary leakage of flatus and/or faeces from the anal canal (National Institute for Health and Care Excellence, 2007). Women who have sustained an obstetric anal sphincter injuries have a 2- to 3-fold greater risk of developing subsequent anal incontinence, with incidence rates ranging from 7—61% (Antonakou, 2018). In a prospective study, patients with obstetric anal sphincter injuries undergoing primary repair reported an incidence of anal incontinence of over 50% (Fernando et al, 2002). This sequela of obstetric anal sphincter injuries results in women with higher rates of negative body image, sexual dysfunction, anxiety and depression. Many women with anal incontinence have been described to develop an ‘obstetric anal sphincter injuries’ syndrome that represent a complex of social, emotional and psychosexual suffering following obstetric anal sphincter injuries (Darmody et al, 2020).
A second significant complication of obstetric anal sphincter injuries (third and fourth degree perineal tears, which include damage to the anal sphincter complex and anal mucosa respectively) (Table 1) is the development of ano-vaginal or recto-vaginal fistula (an abnormal opening connecting the rectum or upper anal canal to the vagina). These can be identified acutely as a defect in the rectovaginal septum following birth or can present later as feculent discharge from the vagina. In a published Norwegian study, the mean time from obstetric anal sphincter injuries to diagnosis of fistula was 40 weeks (Trovik et al, 2016).
Table 1. Grades of obstetric anal sphincter injury
| Grade | Description |
|---|---|
| First | Injury to perineal skin only |
| Second | Injury to perineum involving perineal muscles but not anal sphincter |
| Third | Injury to perineum involving anal sphincter complex: |
| 3a | <50% of external anal sphincter thickness torn |
| 3b | >50% of external anal sphincter thickness torn |
| 3c | Both external and internal anal sphincter torn |
| Fourth | Injury to perineum involving anal sphincter complex (external and internal anal sphincter) and anal epithelium |
Source: Royal College of Obstetricians and Gynaecologists (2015)
Accepted management of third and fourth degree perineal tears post vaginal birth is primary repair. A full thickness repair of the external sphincter is usually done using an overlapping or end-to-end technique, while partial thickness tears are repaired with end-to-end muscle apposition. Internal anal sphincter injuries and mucosa defects are repaired as a separate layer where seen (RCOG, 2015).
While it is widely accepted that lesser degrees of perineal injury (grades 1—3) will not need stoma formation in order to allow healing, stoma formation is occasionally used in the management of significant perineal trauma following birth (Fernando et al, 2002). In obstetric practice, the main indications for stoma formation immediately following birth would be fourth degree tears with large defects in the recto-vaginal septum (Fernando et al, 2002). A stoma would be formed at the same time as a repair of the obstetric injury. The incidence of stoma formation in the acute setting is not well documented and the authors therefore understand it is likely to be very low. An unpublished literature search in the authors’ unit found no papers specifically describing patients who had stomas formed acutely following obstetric injury. An unpublished local audit suggested an incidence of stoma formation in the acute post obstetric anal sphincter injuries period of approximately 1 in every 9000 births. An Australian study describing the experience of a single colorectal surgeon described six stomas formed acutely for obstetric injuries in 10-year period (Giddings et al, 2022).
How a colostomy is formed
Anatomically, a stoma is simply an opening in the body between the skin and a hollow viscus. Common types of intestinal stomas are colostomies and ileostomies. Colostomies are formed from the colon (large bowel) and ileostomies are formed from the ileum (small bowel). Either type can be permanent or temporary, depending on its purpose, and either can be an end stoma (Figure 1) or a loop stoma (Figure 2), depending on whether just one or both ends of divided bowel are brought to the skin surface. End stomas are more effective at completely diverting the bowel contents because of the nature of its formation with a closed distal limb. A colostomy is therefore the connection of the large bowel (colon) to the skin of the abdominal wall to divert faeces and flatus to the surface of the abdomen, which are then collected in an external appliance (stoma bag) (O'Connell, 2018).
One indication for a temporary loop colostomy (Figure 2) is after a traumatic insult to the rectum or anus, to protect the healing area from the passing stream of faeces, reduce infection and allow healing. The traumatic injury may be caused by a cancer, cancer treatment like radiotherapy, acute trauma, obstetric trauma or conditions such as inflammatory bowel disease (Martin and Vogel, 2012). A temporary loop colostomy is the most common form of stoma created following significant obstetric trauma. It is sometimes referred to as a defunctioning loop colostomy, with its intended purpose to bypass the usual function of the rectum and anus. Its formation as a loop allows easy identification of the distal end when the patient is undergoing reversal surgery.
Stoma reversal
The permanency of a stoma depends on many factors, largely the reason for its creation. In the case of obstetric trauma, in an otherwise fit and healthy patient, a stoma would usually be a temporary measure with a plan for a reversal in due course. In patients with obstetric anal sphincter injuries, stomas are usually reversed (the bowel ends joined back together during another operation) some months after their formation. The timing of this procedure depends on healing, other maternal comorbidities and duration of breastfeeding, but could be considered anytime from approximately 6 months after birth. As there are no guidelines, given the rarity of the situation, this procedure is managed on an individual basis, with experience drawn from cancer surgery and trauma, where this is more commonly found.
Given the small number of patients with stomas immediately following obstetric anal sphincter injuries, there are no published data on average time to reversal surgery. Most studies looking at time to stoma reversal describe cancer patients in whom further surgery may be delayed because of post-operative chemotherapy or other medical comorbidities in an older patient group (Kuryba et al, 2016). In cancer groups, the median time to stoma reversal is around 10 months (Kuryba et al, 2016). Stoma reversal post-obstetric anal sphincter injury is likely to take place in less time than this. In the authors’ opinion, reversal surgery is likely to be more difficult in the first 3 months following surgery, as a result of the nature of inflammatory adhesions in the post-operative abdomen. It is usual for any re-do surgery to be performed after this period.
Creation of a stoma
Creation of a stoma is life altering for patients. Ideally, stoma formation requires careful planning, conversation and appropriate support (Hill, 2020). In addition to understanding the anatomy of a patient's abdomen, including scars, skin folds and other characteristics, one must also consider lifestyle, bowel function and employment. The involvement of a stoma nurse specialist is crucial to the successful management of patients with a stoma. Experienced stoma nurses counsel patients pre-operatively, teach stoma care post-operatively and provide help and advice going forward (Carter, 2020). The importance of midwife support in the immediate birth period cannot be overemphasised (Darmody et al, 2020), and research shows that midwives are well-placed to provide counselling to women with distressing birth experiences in the longer term (Gamble and Creedy, 2009).
The operation to create a stoma can be undertaken in an open or laparoscopic manner. Singh et al (2019) compared the outcomes between laparoscopic and open sigmoid colostomy formation for temporary faecal diversion, and found that the laparoscopic cohort had lower post-operative pain requirements, shorter hospital stay and earlier return of bowel function. Many surgeons in the UK will perform this procedure laparoscopically, rather than using an open surgical approach. This widely accepted technique has been used for many years. (Hollyoak et al, 1998).
The surgical principles of stoma formation are (Whitehead and Cataldo, 2017):
- Access to the peritoneal (abdominal) cavity
- The part of bowel that is to be brought to the skin surface is carefully examined for viability, tension or twisting
- Excision of a circular skin disc at the preoperatively marked site
- The bowel is delivered through the inside of the abdominal wall to the external aspect of it, ‘exteriorising’ the bowel
- The incisions used to access the abdominal cavity are closed, to prevent contamination with faeces
- Half the circumference of the bowel wall is divided and the two open ends of the bowel tube are sutured to the skin surface
- A stoma bag is then cut (appropriate to the size of the stoma) and applied around the stoma to collect faeces.
Outside of the immediate post-operative period, a stoma is generally pink, moist and void of sensation to touch. A colostomy will often produce output within the first 48 hours post-operatively (NHS, 2020). The bowel may behave erratically post-operatively, which is expected after any abdominal surgery, but will settle into a routine over time. The content that is produced by a colostomy is mostly solid.
Odour is often a concern for patients (Colostomy UK, 2021), and it is important to remember that passing stool will often be associated with a smell, regardless of the mechanism. However, stoma bags are odour-proof and some come with a filter. Therefore, they do not usually have an odour outside of when the contents are being disposed. The stoma bag is hidden underneath clothes, although the psychosexual impact of a stoma is significant (Black and Notter, 2021).
What evidence is there to help decide on colostomy formation?
There is no evidence or published guidelines to describe which women will benefit from an immediate defunctioning stoma to allow improved healing from an obstetric anal sphincter injuries. The theory is that diverting the bowel contents by making a loop colostomy reduces infection rates in the perineum and improves healing (Kucera and Olson, 2023). In a study of post-surgical rectovaginal fistula healing, those who achieved healing within 6 months were significantly more likely to have had a diverting stoma formed and pelvic sepsis was associated with failure to heal (Barugola et al, 2021). Women with very significant obstetric anal sphincter injuries occasionally need a stoma to allow for healing of obstetric anal sphincter injury repair, but very minor tears will certainly not need a stoma.
In the colorectal surgery community, there are no agreed guidelines regarding which patients and which perineal injuries would benefit from a defunctioning colostomy. A review of national guidelines for obstetric anal sphincter injuries published in 2020, covering 13 countries, did not comment on the indications for stoma formation (Roper et al, 2020).
Data from the Fistula Hospital in Ethiopia show that 38% of women had altered continence following delayed primary repair of their rectovaginal fistula, and none of these women had stomas formed. This compares to Okeahialam et al's (2023) network meta-analysis of nine European studies and one Australian study, which showed that 29% women with repaired fourth degree tears had anal incontinence. It is unknown whether continence would have been improved if a temporary stoma had been formed to allow better healing or even whether a stoma always allows improved healing.
Ramage et al (2017) reported no difference in quality of life measures in women with different grade obstetric anal sphincter injuries and many groups report reasonable quality of life in patients who have had obstetric anal sphincter injuries repairs without stoma formation. A study from Denmark followed 22 women with third or fourth degree tears repaired (either more than 72 hours from injury or less than 14 days) without a stoma for 4 years (Soerensen et al, 2008). The women had slightly worse continence scores (Wexner 4.1 vs 1.1) compared to a control group (women after vaginal birth with no obstetric anal sphincter injuries), but their quality of life was not different. This might suggest that stoma formation should be avoided in any patients unless they develop symptoms at a later date. However, further research from the same Danish group (Barbosa et al, 2020) has shown that 30% patients having an early secondary (within 21 days) surgical repair of obstetric anal sphincter injuries without stoma formation developed a fistula. So there may be a group of patients in which stoma formation will protect against later complications, including fistula formation.
Studies have suggested that specific patient groups are at risk of worse outcomes following obstetric anal sphincter injuries. A Finnish study of more than 300 patients after an acute repair of a third or fourth degree tears showed 27% of women had mild anal incontinence, while 9% had severe anal incontinence (Kuismanen et al, 2018). Impaired continence was more likely in older women, following an instrumental birth and with higher severity of perineal tear. A lower threshold for stoma formation in older women with significant obstetric anal sphincter injuries after an instrumental birth may reduce the burden of future symptoms in specific groups.
The guidelines used for trauma patients (those with traumatic injuries to the pelvis, such as from road traffic accidents, falls, crush injuries and penetrating trauma including stabbings and gunshot injuries) conditionally recommend proximal diversion with a stoma to reduce the incidence of infectious complications in patients with non-destructive, penetrating, extra-peritoneal rectal injuries (Bosarge et al, 2016). These low rectal injuries would be in a similar site to obstetric anal sphincter injuries. However, the population that this guideline covers is often those who have had a major traumatic insult, who maybe haemodynamically unstable. This is a very different physiological group to woman who have just given birth, who are often young and otherwise well, with good blood supply to the injured area. Despite this, the trauma guidelines are one of the few guidelines to discuss defunctioning stoma formation in perineal trauma and therefore have been addressed in this article.
A colorectal surgeon's exposure to acute anal sphincter injuries is reducing. A survey study of obstetricians and colorectal surgeons found that only 10% of responding colorectal surgeons performed five or more acute anal sphincter repairs a year (Fernando et al, 2002). In the emergency setting, when faced with a significant perineal injury, their experience is to form a stoma and prevent contamination (30% of colorectal surgeons recommended colostomy formation for fourth degree tears) (Fernando et al, 2002).
Stoma formation is a common and relatively simple procedure for colorectal surgeons. In contrast, obstetricians manage many more acutely injured perineums (46% of obstetricians undertaking five or more acute repairs of anal sphincter injuries a year) but have less exposure to rectal and anal injuries and stoma formation (none recommended stoma formation) (Fernando et al, 2002). If colorectal consultants are called as an emergency to obstetric operating theatres, the study above indicates that it is more likely for a stoma formation to be offered than if the injury is managed by the obstetric team alone. Senior obstetricians will have more experience than colorectal surgeons and should be the first point of contact in the management of obstetric anal sphincter injuries.
In the authors’ experience, it would be usual, yet rarely seen, practice to recommend stoma formation in patients with very significant obstetric anal sphincter injuries (grade 4 tears with large defects in the rectovaginal septum) immediately following birth and at the same time as a repair of the perineal injury. As described above, there is little evidence for or against this practice. Even the number of women who undergo stoma formation in the acute setting is difficult to ascertain. As such, the consent process for these operations is vital. This patient group is usually young, fit women who have not had time to process the implications of stoma formation. Benefits and risks must be fully explained and the chance to meet with a stoma nurse should be encouraged where possible. This will allow patient counselling as well as ensuring that siting of the stoma on the skin is as accurate as possible (Carter, 2020). Support by care professionals, including midwives, is vital in mediating the emotional distress of traumatic birth experiences. Both emotional and practical support from a midwife who has cared for women with obstetric anal sphincter injuries is important (Baxter, 2020).
Obstetric anal sphincter injuries are ideally repaired as soon as possible and the RCOG (2015) guideline for the management of third and fourth degree perineal tears states that ‘if there is excessive bleeding, a vaginal pack should be inserted and the women taken to theatre as soon as possible’. However, there is evidence that suggests that repair of significant obstetric anal sphincter injuries can be delayed by up to 12 hours (Nordenstam et al, 2008) with no detrimental effect on future anal incontinence symptoms. The Canadian obstetric anal sphincter injuries recommendations state that ‘repair can be delayed for 8 to 12 hours with no detrimental effect. Delay may be required so a more experienced care provider is available for the repair’ (Harvey et al, 2015). As well as allowing time for informed consent, patient discussion and stoma nurse counselling, this would also allow the most experienced clinicians to repair the obstetric anal sphincter injuries and form a stoma if needed.
Conclusions
As with all areas of medicine, there are multiple grey areas when examining obstetric anal sphincter injuries and stoma formation. Few obstetricians, colorectal surgeons, midwives or even patients would argue that a stoma formation is often the most sensible course of action if a very significant obstetric anal sphincter injuries occurs. Equally, in small third and fourth degree defects, stomas should be avoided and patients given the opportunity to heal a repair without the added physical and psychological impact of life with a stoma. The grey areas require detailed discussions with patients as to what risk of complications they would be willing to accept to avoid a stoma. This may be difficult in the emotionally fraught time immediately following birth. The lack of definite evidence of best treatment means it is essential that patients are given a detailed explanation of the options, with the risks and benefits of each, and are supported to make management decisions with their healthcare team. These decisions are likely to be different in each individual case.
There is further scope for an interdisciplinary approach in the management of obstetric anal sphincter injuries between the midwife, obstetrician and colorectal surgical teams. The development of standardised management guidelines, with the inclusion of defunctioning stoma, would help bridge this gap and improve outcomes for women with obstetric anal sphincter injuries.
Key points
- Severe obstetric anal sphinter injury cases are on the rise and lead to significant comorbidities such as anal incontinence, recto-vaginal or ano-vaginal fistulas and psychological distress.
- The formation of a defunctioning colostomy may reduce the incidence of complications of obstetric anal sphincter injuries, although there is a need for more published evidence.
- The complications of vaginal birth and formation of a defunctioning stoma require thorough consultation of the risks and benefits to gain informed consent. Stoma nursing teams should be involved to support patients.
- Development of a management guideline for obstetric anal sphinter injuries, including the use of defunctioning stoma, would help standardise future practice.
CPD reflective questions
- How could you support a woman who experienced a significant obstetric anal sphincter injury during vaginal birth, who is discussing perineal repairs with the obstetrics team? What resources might you be able to offer her to aid decision making?
- How can the midwifery team work more closely with obstetricians and local colorectal surgeons to define a clear pathway for women who have had a significant obstetric anal sphincter injury during vaginal birth?
- How could the midwifery community help collect data on whether a defunctioning stoma following obstetric anal sphincter injury is beneficial? Are you aware of how and where this data is collected in your unit?
- Discuss how your practice adequately prepares women for the possibility of obstetric anal sphincter injury during vaginal birth.