Mortality After Groin Hernia Surgery

Groin hernia surgery is a common procedure. The lifetime risk of having an inguinal or femoral hernia repair has been estimated to 27% for men and 3% for women.¹ Whereas elective groin hernia repair is considered a low-risk procedure, emergency procedures have been associated with appreciable mortality. In the Swedish Hernia Register (SHR),² each hernia operation is prospectively followed with 2 endpoints: reoperation in the same groin or death of patient. The aim of this study is to analyze mortality after hernia repair, considering age, gender, mode of admission (emergent or elective), and hernia anatomy.

PATIENTS AND METHODS

The study comprises all patients 15 years or older who had a groin hernia repair (inguinal and femoral) between January 1, 1992 and December 31, 2004 at surgical units participating in the SHR. After each hernia operation, surgeons record data according to the SHR protocol, which includes time on waiting list, mode of admission, patient characteristics (ASA score included in registration from 2003), hernia (primary/recurrent, anatomy), method of repair, anesthesia, complication within 30 days of surgery, and reoperation for recurrence. Clinical follow-up is not mandatory, but any complication observed by the operating unit up to 30 days after surgery has to be recorded. The register has permission to use personal identification number unique for each Swedish citizen, which enables life tables to be adjusted for death of patients and to link recurrent hernias to previous operation(s). The number of aligned units and annual operations recorded have increased from 8 to 90 and from 1689 to 16,783, respectively, from 1992 through 2004. In 2004, approximately 95% of all hernia operations performed in Sweden were documented in the SHR.

Each year an external reviewer visits some of the aligned units and compares register data with a sample of operative records and patient files to check the validity of register data. The register has been found to include some 98% of eligible operations.

For the present study, any combination of hernias that includes a femoral hernia is classified as femoral hernia. Combined hernias of other types or hernias not classified as femoral, direct, or indirect inguinal hernia are grouped as “other hernias” and included among inguinal hernias. Operation within 24 hours after emergency admission for groin hernia is classified as “acute or emergency operation.”

Postoperative mortality risk is defined as standardized mortality ratio (SMR), ie, ratio between observed and expected deaths within 30 days of surgery (irrespective of whether death occurred within or outside hospital) considering age and sex of the population in Sweden. Information concerning mortality of patients was reached by linking vital statistics and SHR. Vital statistics were obtained from Statistics Sweden, www.scb.se (Table 1; death rates by sex and age, 1994–2003); 2001 was chosen as reference year. Statistical analyses were performed using the SPSS version 12.0.1 (SPSS, Chicago, IL). Ninety-five percent confidence intervals (CI) were calculated assuming a Poisson distribution of the number of events and given within parentheses. χ² test was used for comparison between groups.

The study was approved by the Ethics committee of Linköping university, Sweden.

RESULTS

Table 1 illustrates anatomy of all 107,838 hernias as classified by Swedish surgeons. For all of hernias combined and for all hernia types considered separately emergency operations were more common among women than men. Thus, 40.6% of femoral hernias in women and 29.8% in men versus 8.1% and 5.3% of indirect hernias were treated emergently. For both genders combined, an emergency operation was required for 36.5% of femoral hernias in contrast to 5.0% of inguinal hernias (P < 0.001).

Both men and women undergoing an emergent hernia operation are significantly older than patients treated electively, and femoral hernia patients are older than inguinal hernia patients (Tables 2 and 3). After adjustment for gender, the mean age of patients with an emergency operation is 70.0 years (69.5–70.5 years) compared with 57.8 years (57.6–58.0 years) for patients with elective hernia repair and 63.7 years (63.1–64.3 years) for patients with femoral hernia repair compared with 58.8 years (58.6–59.0 years) for inguinal hernia patients.

As demonstrated in Table 4, surgery for all types of hernia with the exception of direct hernia in men is associated with an increased mortality risk. The 30-day SMR after a femoral hernia operation is raised 7-fold for both genders, whereas SMR following an inguinal hernia operation is increased only modestly compared with the death risk of the background population for both men (SMR, 1.29; 1.13–1.48) and women (SMR, 2.82; 1.88–4.08). An emergency femoral hernia operation is associated with SMR 9.71 (7.13–12.91). In contrast, SMR following an elective operation for a femoral hernia does not exceed that of the general population 1.49 (0.41–3.91). For inguinal hernia operations, SMR after emergency and elective operations are 5.94 (4.99–7.01) and 0.63 (0.52–0.76).

Overall mortality within 30 days after groin hernia operations is increased above that of the background population for all men and women (SMR, 1.40; 1.22–1.58 and 4.17; 3.16–5.40, respectively). This is due to the excess mortality following emergency operations, which constitute 4915 of 95,692 (5.1%) of operations on men and 1362 of 8018 (17.0%) of operations on women. The mortality risk following emergency operations for groin hernia is increased 6- to 9-fold compared with the mortality of the general population (Table 5). If bowel resection is undertaken, the risk is raised 20-fold. Bowel resection is undertaken in 226 of 1062 (21.3%) emergency femoral hernia operations compared with 268 of 4947 (5.4%) emergency inguinal operations (P < 0.001). Following an elective operation, 30-day mortality is lower than expected for both genders, significantly so for men, 0.67 (0.55–0.82), but not for women, 0.85 (0.34–1.75). It should be noted in Table 6 that the mortality risk after elective procedures tends to fall below unity even for patients aged 70 years or older.

Table 7 illustrates that patients with ASA score I and II have a very low risk for postoperative mortality, whereas the mortality risk is raised significantly above that of the background population for both men and women with ASA score III to V. The notation of at least one complication raises the mortality risk, whereas primary or recurrent hernia operation does not affect the risk.

Local anesthesia carries a low risk compared with general and regional anesthesia in both elective and emergency operations (Table 8). The mortality risk is low following both open and laparoscopic elective operations but significantly increased above the expected level after emergency surgery.

DISCUSSION

Elective hernia surgery is a low-risk procedure. Patients with emergency operations are approximately a decade older than patients treated electively. Emergency operations are 3 times more common in femoral than in inguinal hernia, and they carry a substantial mortality risk especially if bowel resection is performed. The excess postoperative mortality in women compared with men is due both to their high proportion of femoral hernia and to an increased risk for emergency procedure in all types of hernia. High ASA score and postoperative complication are associated with increased mortality risk, whereas primary or recurrent operation does not affect the risk.

Our study population is large, coverage nearly complete, and all data are prospectively recorded. Through personal identification number and linkage to official vital statistics, we have robust information on patients' death. The risk of death is given in relation to the death of the background population. We have, however, limited data on patient morbidity except ASA scores for 2 years.

The safety of local anesthesia makes it a favorable alternative whenever feasible.^3–6 In the present study, methods of surgery did not significantly affect mortality. This should, however, be interpreted cautiously, as techniques are chosen with respect to morbidity of patients.

Our finding that the mortality following elective operations in men is lower than expected from death rates in the general Swedish population agrees with conclusions reached in a previous report from SHR⁷ and indicates that healthy patients are selected for planned hernia surgery. In accordance with previous studies,^8–11 we found that also elective femoral hernia repair is associated with a very low mortality risk. Thus, the mortality risk in elective groin hernia surgery should not be a major issue when discussing indication for operation with a patient having a symptomatic hernia. Among symptomatic patients, those with a short duration of symptoms have a higher risk of requiring emergency surgery.^12,13 It has been suggested that patients with vague symptoms and unfavorable medical conditions should be recommended elective hernia repair to avoid the high mortality associated with emergency repair.¹⁴ The present study support this view as elective hernia surgery, even at high age, does not raise the mortality risk above that of the general population, whereas emergency hernia surgery is associated with a substantial mortality risk.

As femoral hernias are more frequent among recurrent hernias than among primary hernias, it has been suggested that femoral hernias may be overlooked during repair of an inguinal hernia.^8,15–17 (This is one possible explanation for the high proportion of female direct hernia in the present study, 17% of acute hernia and 23% elective hernia, although direct hernia is considered very rare in women.¹⁸) Hence, it may be appropriate to examine the femoral canal in inguinal hernia operations in order not to overlook a femoral hernia with its particular risk for emergency surgery, bowel resection, and postoperative mortality. This can be done by palpation through the hernia sac or by observing the femoral canal during a Valsalva maneuver if the repair is done in local anesthesia.

The high age of patients in need of emergency repair of groin hernia has been noted previously.¹⁹ Possible reasons for the high rate of emergency operation in femoral hernia found in this and earlier surveys^8–11 are: no or vague symptoms prior to incarceration, diagnostic difficulties even at incarceration, and anatomic considerations that are outside the scope of the present study. Hjaltason²⁰ reported that 15 of 46 patients with incarcerated femoral hernia were unaware of their hernias prior to hospital admission. Similarly, acute hospital admission was the first indication of hernia for 15 of 24 patients presenting with incarcerated femoral hernia in a recent survey.²¹ Diagnostic delay in incarcerated (femoral) hernia is associated with worse prognosis.^9,22 In one report, strangulated hernias were misdiagnosed by the general practitioner in 33% of the patients and by the hospital registrar in 15%.²³

There is an embarrassing lack of available information concerning the prevalence of groin hernia in the general population, in particular among women. The well-known study from Jerusalem²⁴ addressed hernia prevalence in men exclusively. A more recent case-control study was concerned with potential risk factors in women undergoing elective inguinal hernia only.²⁵ For men with ASA score I to III and minimally symptomatic inguinal hernia, watchful waiting is an acceptable option because of a low risk for hernia incarceration.²⁶ As discussed above, the situation is quite different for femoral hernia due to its high rate of emergency surgery. Further epidemiologic studies concerning the prevalence of inguinal and femoral groin hernia among elderly individuals would be of value for healthcare planning.

Hernia is considered an avoidable cause of death,^1,13,27 and this applies in particular to femoral hernia. The present findings have important consequences for populations of increasing age.²⁸ During inguinal hernia repair, we should try to identify any concomitant femoral hernia. We should intensify our efforts to improve early diagnosis and treatment of patients with incarcerated and or strangulated hernia, and we must aim for optimizing perioperative care. Further, we should openly discuss elective operation with old and frail hernia patients and offer patients with femoral hernia early planned surgery, even if symptoms are vague or absent.

ACKNOWLEDGMENTS

The authors thank Lennart Gustafsson who provided invaluable help with statistics.