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Totally extra-peritoneal (TEP) inguinal hernia repair allows identification and repair of incidental non-inguinal groin hernias. We assessed the prevalence of incidental hernias during TEP inguinal hernia repair and identified the risk factors for incidental hernias.
Consecutive patients undergoing TEP repair from May 2005 to November 2012 were the study cohort. Inspection for ipsilateral femoral, obturator and rarer varieties of hernia was undertaken during TEP repair. Patient characteristics and operative findings were recorded on a prospectively collected database.
A total of 1,532 TEP repairs were undertaken in 1,196 patients. Ninety-three patients were excluded due to incomplete data, leaving 1,103 patients and 1,404 hernias for analyses (1,380 male; 802 unilateral and 301 bilateral repairs; median age, 59 years). Among the 37 incidental hernias identified (2.6% of cases), the most common type of incidental hernia was femoral (n=32, 2.3%) followed by obturator (n=2, 0.1%). Increasing age was associated with an increased risk of incidental hernia, with a significant linear trend (p<0.01). The risk for patients >60 years of age was 4.0% vs 1.4% for those aged <60 years (p<0.01). Incidental hernias were found in 29.2% of females vs 2.2% of males, (p<0.0001). Risk of incidental hernia in those with a recurrent inguinal hernia was 3.0% vs 2.6% for primary repair (p=0.79).
Incidental hernias during TEP inguinal hernia repair were found in 2.6% of cases and, though infrequent, could cause complications if left untreated. The risk of incidental hernia increased with age and was significantly higher in patients aged >60 years and in females.
Inguinal hernia repair is one of the most commonly undertaken surgical procedures, with >73,000 procedures carried out in England each year. 1 The most frequently utilised method is open tension-free mesh repair (Lichtenstein method). Laparoscopic methods include the trans-abdominal pre-peritoneal (TAPP) and totally extra-peritoneal (TEP) approaches. TEP hernia repair avoids the need to open the peritoneum and reduces the risk of intraperitoneal complications. 2
Advantages of the laparoscopic method include: quicker return to normal physical activities;3,4 reduced postoperative pain and lower risk of chronic pain in the groin;5,6 the potential to repair bilateral hernias using the same three ports; avoidance of scarred tissue planes in recurrent hernias. However, laparoscopic procedures mandate general anaesthesia, and are associated with slightly longer operating times and higher short-term costs. 7
Laparoscopic repair of inguinal hernias allows direct visualisation of other myofascial defects in the groin and pelvis. This feature enables inspection and repair of hernias (ipsilateral, direct, indirect, femoral, obturator) (Fig 1).8,9
These small incidental hernias in the groin may be difficult (or impossible) to detect by physical examination. Hence, additional hernias identified at laparoscopic repair of inguinal hernias are frequently unexpected. 10 Repair of these defects prevents their progression and subsequent associated complications. Accurate knowledge of the frequency of ipsilateral incidental hernias in patients undergoing TEP inguinal hernia repair (and any risk factors that make incidental hernias more likely) may inform clinical decisions regarding operative approach, and assist intraoperative decisions about the extent of dissection (eg of the obturator canal to visualise other potential myofascial defects).
Herein, we report the prevalence of incidental hernias upon TEP repair from a large cohort of patients at a single Hernia Centre. Also, we evaluate the factors associated with an increased risk of finding unsuspected hernias at TEP repair.
Consecutive patients undergoing elective TEP repair of an inguinal hernia at a single Hernia Centre were the study cohort. Each patient undergoing a TEP procedure from May 2005 to November 2012 was included, with bilateral procedures recorded as two cases. The preoperative diagnosis was determined by clinical examination alone, or by ultrasonography if clinical examination was inconclusive.
Demographic data and operative findings were recorded prospectively on a clinical database. The information documented was: age; sex; side of hernia; whether the hernia was primary or recurrent, unilateral or bilateral; need for conversion to open surgery; incidental hernias; intraoperative complications. Patients with incomplete datasets were excluded from the analyses.
The procedure was carried out by one of three experienced surgeons at our institution as the primary surgeon or supervising a senior trainee surgeon. A standard three-port method was used.
The pre-peritoneal space (PPS) was entered inferiorly to the umbilicus and insufflation with carbon dioxide commenced. During the early part of the study (May 2005–July 2009), an expandable balloon was used routinely to enlarge the PPS. From July 2009 onwards, most procedures were carried out without balloon dissection: direct telescopic dissection was used instead. In this method, the PPS was enlarged by gentle movement of the camera through the loose areolar tissue in the PPS. Once sufficient space was created, further 5mm ports were inserted in the midline between the umbilicus and symphysis pubis under direct vision. Then, further dissection was undertaken to enlarge the PPS and identify key anatomical structures.
Full dissection of the inguinal hernia sac was done to reduce the hernia and define the myofascial defect. All groin orifices on the ipsilateral side were examined to identify occult hernias. The contralateral groin was not explored routinely if asymptomatic because we felt that the risks of contralateral dissection outweighed the benefits of exploration. Incidental hernias were defined as any tissue protruding through a well-defined myofascial defect (ie all grades of hernia were included).
Once the hernia(s) was fully reduced, a polypropylene mesh was inserted and positioned in the pre-peritoneal plane, ensuring the medial border was covering the midline and all hernia orifices. A tacking device was not used routinely to secure the mesh.
Possible risk factors for incidental hernias were explored: age; sex; primary vs recurrent hernias; unilateral vs bilateral hernias. The chi-square test was used for qualitative data and for trend (if appropriate). p<0.05 was considered significant.
A total of 1,532 TEP inguinal hernia repairs were undertaken in 1,196 patients. Owing to incomplete data, 93 patients were excluded from further analyses, leaving 1,404 repairs in 1,103 patients. The male:female ratio was 1,380:24. The median age was 59 (range, 15–88) years. Of the 1,404 repairs, 802 were unilateral and 301 bilateral, with 1,270 primary and 134 recurrent hernias (Table 1).
Overall, incidental hernias were identified in 37/1404 (2.6%) cases. The most common type of incidental hernia was femoral (n=32, 2.3%) followed by obturator (n=2, 0.1%), with one spigelian, one pre-vascular and one intermuscular hernia.
The risk of incidental hernia for patients aged >60 years (n=672) was 4.0%, compared with 1.4% for those aged <60 years (n=732) (p<0.01; two-sided chi-square test; odds ratio (OR), 3.0; 95% confidence interval (CI), 1.5–6.3). Increased risk with age was also seen by an incremental rise in the frequency of incidental hernias per decade (Figure 2), which showed a significant linear trend (p<0.01; chi-square test for trend).
Incidental hernias were found in 29.2% of females compared with 2.2% of males, (p<0.0001; two-sided chi-square test; OR, 18.5; 95% CI, 7.2–48.0) (Fig 3).
The risk of incidental hernia in those with a recurrent inguinal hernia was 3.0% vs 2.6% for primary repair, though this difference was not significant (p=0.79; two-sided chi-square test; OR, 1.2; 95% CI, 0.40–3.3).
This study was the largest reported case series to date. We found the overall prevalence of occult hernias at TEP hernia repair to be 2.6%. Smaller series have reported varying results of the prevalence of incidental hernias seen at laparoscopic inguinal hernia repair. Studies9–14 have shown a prevalence of 3.7–5.3% with the exception of the study by Dulucq et al, 9 which recorded incidental hernias in 16.7% of cases, with obturator hernias identified in 7.2% of patients.
There are several explanations for the lower prevalence seen in the present study, including relatively lower proportions of ‘high risk’ groups for incidental hernias. Females had a higher prevalence of incidental hernias than males based on our findings. The proportion of female patients in our study (1.7%) was lower than that in the studies by Crawford et al (4.0%), 11 Ramshaw et al (9.6%), 12 Messenger et al (2.5%), 13 Dulucq et al (17%), 9 Putnis et al (3.9%), 14 and Henriksen et al (5.6%). 10 Similarly, the relatively low proportion of recurrent hernias (9.5%) in our study population may also have accounted for the lower prevalence of incidental hernias than in some reported series (as could the age of the study population if other study groups had a higher mean age).
Another factor that could explain the lower frequency of incidental hernias seen in the present study was the extent of dissection carried out during hernia repair (particularly with regard to obturator hernias). More extensive dissection of the obturator canal in each patient may have identified small hernias containing pre-peritoneal fat that may otherwise have been missed. This feature is difficult to compare between studies, and further compounded by variation in the method of dissection. Our dissection method changed during the study period from use of an expandable balloon to direct telescopic dissection (though, in our study, there was no significant difference between the prevalence of hernia detection in the series of consecutive cases before and after the change in method). Furthermore, the frequency of detection of incidental hernias increased during the study period, suggesting the influence of surgeon experience, either through more extensive dissection, or more thorough search for incidental hernias having identified such hernias previously.
As stated above, in our institution, the contralateral side is not dissected and inspected routinely. In studies quoting data in which a TAPP approach has been used,10,12 both groins will have been inspected, even in cases of unilateral hernias. Some institutions undertaking TEP repair explore both groins routinely for unilateral hernias (eg Messenger et al) 13 . If two groins are inspected for each unilateral hernia repaired, the chances of finding a contralateral, non-inguinal incidental hernia will be higher per case: this may lead to a higher proportion of patients with unsuspected hernias quoted per case. Data in the present study give a true reflection of the proportion of hernias per groin inspected, and may explain the lower prevalence recorded in the present study than reported in other studies.
We found that females had a much higher prevalence of incidental hernias than males, with 29.2% of females having an additional hernia identified at TEP repair. Henriksen et al and Putnis et al found a higher prevalence of femoral hernias at TEP repair among small cohorts of female patients.10,14 Putnis et al found an overall prevalence in female patients of 37%, whereas Henriksen et al found a prevalence of 38.1% in females with recurrent hernias.10,14
Femoral hernias are more common in females than males, comprising approximately one in six of all elective groin hernias in women, compared with <1% of elective hernias in males. 15 Of those groin hernias requiring emergency surgery, >50% are femoral hernias in females, compared with ≈6% in males. 15 The higher prevalence of femoral hernias in females undergoing TEP repair is likely to be a consequence of the higher overall prevalence of femoral hernias in females, which is thought to result primarily from the different pelvic anatomy of females.
A further factor in the high prevalence of unsuspected hernias in females may be preoperative misdiagnosis of inguinal hernias. Although this factor was not the case in our series, Schouten et al found misdiagnosis in 18.3% of females undergoing surgery for a groin hernia. 16 This result has led some authors to argue that a laparoscopic approach should be the method of choice for treating female patients with groin hernias because of the high prevalence of unsuspected additional ipsilateral hernias,10,14 and because of inaccurate preoperative diagnosis of inguinal vs femoral hernias. 16
In the present study, the prevalence of incidental hernias increased steadily with age and showed a significant linear trend. The risk of incidental hernia for patients aged >60 years was significantly higher than that for younger patients. This observation corroborates the findings of Henriksen et al, who found that men with unsuspected femoral hernias at laparoscopic hernia repair were significantly older than those with inguinal hernias alone. 10 This increase in the prevalence of additional hernias with age may reflect the greater prevalence of hernias in general in older patients, which in turn may be caused by altered collagen synthesis in elderly patients10,17 or other comorbidities.
In the present study, the prevalence of incidental hernias in those undergoing TEP repair for a recurrent inguinal hernia was higher than for those undergoing primary repair, but this difference was not significant. Among one cohort studied by Henriksen et al, the prevalence of incidental hernias in those undergoing recurrent repair was significantly higher than for primary repair. 10 One explanation for the higher prevalence seen in the study by Henriksen et al was the higher proportion of female patients (5.6%) than in our study (1.7%). Henriksen et al postulated three explanations for the higher risk of incidental femoral hernias in those with recurrent hernias: (i) the primary procedure may facilitate a femoral hernia through altered local structural mechanics in the groin; (ii) these patients may be predisposed to hernia formation possibly because of altered metabolism or altered quality of collagen; (iii) failure to recognise femoral hernias at the primary procedure.
The study by Henriksen et al gave an estimate of the prevalence of occult hernias, but the clinical significance of such hernias is unclear. It is likely some of the hernias identified would have gone on to cause morbidity in the future, however, this effect cannot be quantified accurately from the current study. This is particularly the case for obturator hernias containing pre-peritoneal fat only: many such hernias may never otherwise have become clinically apparent. Indeed, whether a fat body in the obturator canal is a pathological entity or serves a protective anatomical function is controversial 18 because cadaver studies have found such tissue to have a prevalence of 2–36%.19–21
The ability to detect and repair unsuspected hernias at TEP inguinal hernia repair is a further advantage of this method over an open anterior approach. The prevalence of incidental femoral hernias observed in the present study justifies thorough ipsilateral dissection at TEP repair. We found a lower prevalence of obturator hernias than that reported previously. For females with a groin hernia, the high risk of unsuspected hernias should be considered and discussed when choosing the operative approach. Similarly, in patients aged >60 years, the higher risk of unsuspected hernias should be taken into account, but this must be weighed against the requirement for general anaesthesia and its concomitant risks in elderly patients with comorbidities.