A buttonhole tear is a laceration of rectal mucosa and vagina which rarely occurs during delivery. It is usually an isolated incident and doesn’t involve anal sphincter (1-3). However, it may be associated with sphincter injury in some cases. The overall incidence of OASI (obstetric anal sphincter injuries) in the UK is 2.9%, with a higher incidence in primiparity (6.1%) compared to multiparity (1.7%); although the exact incidence of rectal button hole tears is not known, these injuries are rare (4,5).
Searching literatures showed very limited studies and there was no comprehensive statistics on grade 3 and 4 obstetric injuries in Iran. In the study in Mashhad which examined 7 cases, four (57.2%) were multiparous and three cases were primiparous. The most risk factors associated with perineal lacerations included 6 cases of induction by oxytocin, 3 cases of gestational diabetes, 3 cases of postdate pregnancy and 2 cases of macrosomia (6).
If a thorough rectal examination is performed, this damage will be identified immediately after delivery. Otherwise, it is diagnosed late with abnormal discharge and eventually rectovaginal fistula. Here, we reported a case of rectal buttonhole injury following vacuum delivery.
This A 31-year-old primigravid woman was admitted to the Maternity ward of a teaching hospital of Mashhad University of Medical Sciences, Mashhad, Iran, for pregnancy termination. The primary general consent form was completed by the patient at the time of admission. She had a history of non-severe gestational hypertension since 20th week. At admission, vital sign was stable and blood pressure was 140/90 mmHg. Laboratory evaluation showed normal values. Labor induction was started with low dose oxytocin regiment. First stage of labor progressed normally. With regard of labor arrest in the second stage of labor for 2 hours in occiput posterior position and non-reassuring fetal heart rate tracing, operative vaginal delivery was performed using the silastic cup at the fetal head station of +2 by an experienced professor. To rule out the included vaginal epithelium, cup was completely checked. A left mediolateral episiotomy was also done.
After just once trying, vaginal delivery occurred successfully and a female neonate (3350 gr) was born with Apgar score of 9 -10. The placenta and membranes were completely delivered.
Vaginal and rectal examinations were performed immediately after delivery. Rectovaginal examination revealed a 2 cm button-hole laceration in the rectovaginal septum, 5 cm above the anal canal and medial to the episiotomy incision with regular edges (Figure 1). The external sphincter appeared intact, but the internal sphincter was injured.
The patient was transferred to the operation room. The laceration was repaired under spinal anesthesia in dorsal lithotomy position. First, the rectal mucosa was sutured with continuous Monocryl 2-0, the internal sphincter was repaired by continuous 2-0 vicryl suture, and then the rectovaginal septum and the vaginal mucosa were repaired by the same suture, respectively.
Prophylactic intravenous antibiotic (Cephazolin 2g) was given intraoperative and oral metronidazole continued for 5 days. Low residue regimen was started postoperatively and the analgesic medication added to oral antibiotics. She was discharged on the 3rd day after the assurance of normal defecation and normal vital sign. Magnesium hydroxide also was continuing as a stool softener. In the follow-up visit of 6 weeks, the patient had no complaint of perineal pain or anal incontinence, also the rectovaginal examination showed normal anal sphincter tonicity.
Perineal tears are divided into four degrees (sultan's classification) according to the extent of the injury (Table 1) (2,3,7).
Risk factors for OASIS include assisted vaginal delivery, birth weight > 4 kg, persistent occipitoposterior presentation, nulliparity, tissue factors, and second stage >1 hour (8). Operative vaginal delivery is an important risk factor for 3rd and/or 4th degree perineal tears. However, the risk is reduced by vacuum than that forceps (9). In the present case, nulliparity and vacuum assisted delivery were the main risk factors for buttonhole rectal laceration.
There is no separate classification for isolated obstetrical rectal tears (known as button hole) without injury to the sphincter. There are few reports for this type of injury. It seems that the most important reason for the rarity of this complication is underdiagnoses and underreporting (10,11). OASIS and isolated rectal buttonhole tears should always be excluded after all vaginal deliveries regardless of perineal injury (3). The guideline published by the RCOG (2015) states that following vaginal delivery, anal sphincter injury and anorectal mucosal injury cannot be excluded without performing a rectal examination. The American College of Obstetricians and Gynecologists emphasized this guideline ([ACOG], 2018) (4,12).
In the present case, despite the normal weight of the neonate and performing episiotomy, this happened unexpectedly, which shows the importance of rectovaginal examination after delivery. Actually in the current case, the isolated rectal laceration was diagnosed only after precise digital rectal examination and was not observed at the first visual inspection. NICE and RCOG both recommend to conduct a rectal examination before and after suturing perineal tears (RCOG, 2015; NICE, 2017). The rectal examination is performed before repair to classify the tear accurately and is performed after repair to check that the repair is complete and ensure that no sutures are penetrating the anorectal mucosa (4,13).
There are two types of missed tears; one where the tear is missed completely and recorded as a first or second degree tear, and the other where it is under-classified. Both of these can impact the clinical outcome and quality of life. The evidence showed that tears identified during delivery and repaired appropriately at the same time have improved patient's outcomes, including anal incontinence, perineal pain, dyspareunia and levatorani injuries, compared to when they are remaining undiagnosed (14,15).
In a review of literature, Roper and coworkers (11) reported case series of this type of injury. They reviewed nine published case reports (four instrumental deliveries (9,16,17), two vaginal breech and three normal vaginal deliveries). They also reported 3 cases of buttonhole tears following vaginal delivery from April 2012 to January 2020 in their center. All three cases had an associated episiotomy. Of which, one was a vacuum delivery and two were forceps delivery. In all cases, post-operative antibiotics and laxatives were prescribed for a minimum of 3 days (11).
The type of the suture material, operator skills and the technique used for repair are the three main factors which influence the short and long term outcomes of perineal repair. In most institutions, chromic catgut has been largely replaced by synthetic, delayed-absorbable materials, such as polyglactin 910 and polyglycolic acid, as use of chromic catgut appears to be associated with more postpartum discomfort (18). The continuous technique is faster and uses the smallest amount of suture material (19). In the present case, 2-0 vicryl suture with continues technique repair was used and no wound dehiscence or infection occurred. Postoperative management including appropriate antibiotics, low residue regimen, analgesics, laxatives and precise perineal cleaning with water are the most important postoperative care after perineal repair (20).
We considered all the mentioned postoperative management for the present case, so prophylactic intravenous antibiotic (Cephazolin 2g) was given intraoperative and oral metronidazole continued for 5 days. Low residue regimen was started postoperatively and the analgesic medication and laxative were added to oral antibiotics. The common practice is to schedule women with OASIS repair for a 6 weeks postpartum follow-up visit (21). In the follow-up visit, the present patient had no perineal pain, discomfort or anal incontinence. The rectovaginal examination showed normal anal sphincter tonicity.
Precise evaluation and using the optimal surgical technique are the main points to achieve the best consequences after obstetrics perineal lacerations repair.
We appreciate the Maternity ward of the hospital to provide the resources needed for this report.
Conflicts of interest
Authors declared no conflicts of interest.