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Risk of incarceration of inguinal hernia in Cali, Colombia
J Chron Dis Vol 34. pp 561 to 564. 1981 Printed ,n Great Br,!a,n. All nghts reserved
RISK
OF INCARCERATION OF INGUINAL HERNIA IN CALI, COLOMBIA*
RAYMOND NEUTRA, ADOLFO VELEZ, RICARD~ Department of Surgery, Colombian National
FERRADA
and RICARDO
GALAN
Universidad del Valle, Cali, Colombia; Ministry of Health. Cali, Colombia
(Received 2 February
1981)
Abstract-We ascertained 248 cases of incarcerated and strangulated inguinal hernias in the city of Cali. Columbia, for the years 1969-1973. An earlier Colombian national survey of hernia prevalence provided us with age-, sex-specific prevalences of hernia which, when applied to the Cali census data, allowed calculation of the appropriate denominator of herniated persons. We found the prevalence of inguinal hernia in men lo increase steadily with age. Risk of incarceration among boys below age IO was nearly 2% per yr. falling at all ages thereafter to a value around 3 per 1000 per year. Using hfe-table methods, we estimate that a 65yr-old man runs a 3.63;, risk of incarcerating his hernia by age 75.
INTRODUCTION FEW epidemiological studies of inguinal hernia made to date [l-3] have not dealt with the risk of incarceration, so that our only estimates of this risk derive from biased THE
clinical studies [4-71. Columbia provides an opportunity to estimate both prevalence and the risk of incarceration. A national sample survey of health conditions in Colombia [8,9] affords an estimate of the prevalence of hernia by age and sex. Application of these rates to the population figures extrapolated from the 1964 and 1973 census of Cali, Colombia, allows estimation of the herniated persons at risk in that city. Because four hospitals provide 90% of the care in Cali, it is possible to ascertain virtually all hospitalized individuals with incarceration or strangulation of hernias over the 5-yr period 1969-1973. By dividing this ‘numerator’ by the ‘denominator’ of herniated persons, one can estimate age-specific hernia incarceration rates, a first step towards identifying groups at potential high risk. MATERIALS
AND METHODS
The data base for the prevalence data in this study comes from the clinical examinations of the ‘Estudio de Recursos Humanos para la Salud y Educacicjn Mtdica en Colombia (1968, 1969); [S, 93 which was carried out by the Colombian Health Ministry and the Association of Colombian Medical Schools with the support and consultation of the Milbank Memorial Fund and the Pan American Health Organization (PAHO). Among the objectives of the survey was that of describing the health status of the Colombian population. To carry out this investigation, a random stratified sample was taken of the noninstitutionalized civilian population of the country. The information was collected by means of home interviews and by clinical examinations carried out between August, 1965 and *Thisstudy
is part of the research activities of the Program of Simplified Surgery at the Universidad del Valle. Cali. Columbia, and was supported by a grant from the Rockefeller Foundation. Part of the analysis was funded by the Robert Wood Johnson Foundation through the Center foi the Analysis of Health Practices at Harvard University, Boston, Massachusetts. and part by the Milbank Fund through the UCLA Milbank Program in Epidemiology and Health Policy. University of California, Los Angeles, California, 561
RAYMONDNEUTRAet al.
562
June, 1966 under the supervision of public health physicians. The home interviews were conducted by medical students in 8669 families with a total of 51,473 persons. The clinical examinations were done by residents in internal medicine and pediatrics. A subsample of the previously interviewed subjects, numbering 5026, was selected for the clinical examinations, on which the present analysis is based. The sampling procedure has been previously described [S, 91. Use of the diagnostic indices at the University Hospital, the San Juan de Dios Hospital, the Social Security Hospital, and the Club Nijel ( a charity pediatric hospital) enabled us to identify all patients discharged between January 1, 1969 and December 31, 1973 with the diagnosis of incarcerated or strangulated inguinal hernia. There were about 50 such patients a year in the city. Age, sex, diagnosis and place of residence were taken from the medical records. The total metropolitan population for Cali in 1963 and 1973, as well as the age-sex composition, was obtained from the National Census, and interpolations were made for the intervening years. Hernia prevalence rates were applied to the population for each of the 5 yr and summed to provide an estimate of the herniated persons at risk. Incarceration cases of appropriate age and sex were divided by the number of herniated persons in that category to provide estimates of the incidence of incarceration. RESULTS
The prevalence of inguinal hernia in the Colombian National Health Survey is shown by age and sex in Table 1. Several points are worth emphasizing. The prevalence of inguinal hernia in men increases ever more rapidly with age, reaching a level of l&20% after age 60. The prevalence in women is never over 2% and does not rise markedly with age. The risk of incarcerating or strangulating an inguinal hernia is shown in Table 2. A yearly risk of 18 per thousand herniated persons is seen for males below age 10, after which the risk falls to about 3 per thousand per year in subsequent intervals. The high risk below age 10 is not seen among females although subsequent rates are somewhat higher than those of males. DISCUSSION
Although we believe the overall impressions from this study to be reliable, the figures here must be regarded as approximations. For one thing, we have applied hernia prevalence figures from a total national survey in the mid-1960s to the population of one city in the early 1970s. We assumed that we had ascertained most of the incarceration cases
TABLE 1. POINT PREVALENCE OF INGUINALHERNIABY AGE AND SEXIN THE 1966 COLOMBIANNATIONALHEALTHSURVEY Females
Age G-9 l&19 2&29 3&39 4ck49 5&59 60-64 65-69 270 Totals
*rt;, = 0.
t&,
Males 0
0,
Ing&al
IngZinal herniat
Denominator
hernia*
876 614 355 291 225 133 38 29 66
0.34 0.65 0 I .03 0.78 1.50 2.63 0 I .52
2627
0.61
= 83.9, 1 dj.
p < 0.001
Age G9 lo-19 2Ck-29 30-39 4&49 5&59 6Ck-64 65-69 270 Totals
Denominator 882 543 290 258 197 117 42 36 36
0.45 1.47 3.10 3.49 3.55 9.40 9.52 11.11 19.44
2401
2.6
Risk of Incarceration
TABLE
2. ESTIMATED
RISK OF STRANGULATING
of lnguinal
OR INCARCERATING
Hernia
AN INGUINAL
Herniated persons
Events
S-9 IO-19
1807 3118
1 2
2IS-29 3@39 4cL-49 5G-59 6G-64
28290 1501 1854 1064
91 13 8 7
6920
23
13,525
46
65-69 270 Total
HERNIA,
BY AGE AND
SEX
Males
Females
Age
563
Incidence
Age
Herniated persons
0.5/1000 0.5/1000
C9 l&19 2&29 3cL-39 40-49 5C59 6Cb64 65-69 270
2539 1455 10.150 8107 6045 9435 3709 2813 6349
45 13 23 20 20 29 21 12 19
17.7/1000 1.7/1000 2.7/10&I 2.5/1000 3.3/1ooo 3.1/1000 5.7/1000 4.3/1000 3.0/1000
56,602
202
3.6/l 000
3.2,GXl 8.7/1000 4.3/1OcCl 6.711000 4.3,&)0 3.4/1000
Total
Events
Incidence
in the city. To check this assumption, we reviewed the 16 deaths attributed to strangulated hernias during the PAHO adult mortality study in 1962 and 1963 [lo]. Four of these deaths occurred outside of the hospital. If one assumed that the case fatality for strangulations treated at home was close to 100X, these four fatal cases would account for all the unhospitalized incarceration cases over the 2-yr period. Thus, in 5 yr one would expect to miss 10 cases or about 4”/, of the 248 cases ascertained during this 5-yr study period. If, on the other hand, the case fatality at home was equal to that in the hospital, our rates would be too low by 25% and should be increased by a factor of 1.25. Thus, instead of 3 per 1000 the risk of incarceration in adults would be 3.8 per 1000. It is very difficult to standardize the procedure for detecting a hernia, and if the Colombian physicians ‘overdiagnosed’ hernias this would inflate the reported prevalence and make our estimate of the risk of incarceration an underestimate. In personal conversations with clinicians concerned with the study, we were told that such ‘overdiagnosis’ was not likely to have occurred. Furthermore, the prevalence of inguinal hernia found on physical examination in Colombia was of the same order of magnitude as the rate of self-reported hernia in the United States National Center for Health Statistics interview study [2] and that of Belcher et al. in Ghana [3]. Both studies show an increasing prevalence of inguinal hernia with age. We therefore consider the prevalence figures to be accurate. Our estimates of the risks of incarceration agree with some previous extimates, also, The risk of inguinal incarceration in adults observed by Berger [7] in Paris has been adjusted to a yearly figure by Neuhauser [ 1l] and was found to be 3.7 per loo0 per year. It is of the same magnitude as our own estimate. Other figures cited in the literature do not specify time periods [4-61. Inguinal hernia in small boys is another matter. The high risk of incarceration in male infants is well recognized by pediatric surgeons. A high proportion of hernias in this age group are congenital [12] and apparently have a different natural history. The reported rates of incarceration vary from I.6 to 18% [12-l 71. When we separated out the 27 incarcerations in male infants that occurred in the first year of life, we estimated the 1-yr incidence to be 2.8%. From age 1 to 9 the rate falls to 1.6% and after age 9 is about 3 per 1000, with approximate confidence intervals ( + 3 SE:) of 2 per 1000 to 6 per 1000 per year. Because the Colombian National Health Survey was a stratified sample, 3 SE is a good estimate of the 95% confidence limit [lS. 191. Except for this excess risk in little boys, there are no striking age-related trends in hernia strangulation. This is of some interest for elderly men in whom the incidence of inguinal hernia itself is particularly high. This high incidence of new hernias in older men means that the surgeon will often be faced with the decision of whether or not to operate upon individuals in this age group. We estimate that the cumulative risk of strangulating an inguinal hernia between ages 65 and 75 is of the order of 34%. In our series the case fatality from incarceration was 12%; thus, the risk of incarceration with death is only 4
564
RAYMONDNEUTRA et al.
per 1000 between ages 65 and 75. Since this is a fairly low risk when compared to the operative risk of elderly persons with a variety of chronic diseases, the surgeon may well let other considerations besides the risk of strangulation influence his decision to operate. For an extended analysis of this problem the reader is referred to the chapter by Neuhauser in a recent book, Costs, Risks and Benejits of Surgery [ll]. Acknowledgements-The authors are grateful to Drs Carlos Agualimpia, William Bertrand, and Daniel Bermeo, and to Srta Gloria Ynez Giraldo for help at various stages of this project. Particular thanks are due the Colombian National Health Survey and the Directors of Hospital Departamental, San Juan de Dios, Club Niiel, and Seguros Sociales for permission to review their data.
REFERENCES I. 2. 3. 4. 5. 6. 7. 8. 9. 10. Il.
12. 13. 14. 15. 16. 17. 18. 19.
Logan RFL, Ashley JSA et al.: Dynamics of Medical Care. Memoir No. 14, London School of Hygiene and Tropical Medicine, p. 42, 1972. National Center for Health Statistics: Prevalence of Selected Chronic Digestive Conditions, United States, 1968, Series 10, No. 83, DHEW Publ. No. (HRA) 74-1510, Table 3, p. 19, 1974. Belcher DW. Nyame PK, Wurapa FK: The prevalence of inguinal hernia in adult Ghanaian males. Trop Ceogr Med 30: 39-43, 1978. Zihmerman LM: External and internal abdominal hernias. Am J Gastroenterol 40: 405-410, 1963. Maingot R: Abdominal Operations. 4th Edn, p. 899. New York: Appleton-Century-Crofts, 1961. Koontz A: Hernia. New York: Appleton-Century-Crofts, 1963. Berger P: Resultat de l’examen de dix mille observations de hernies. Extrait du Neuvleme Congr& Francais de Chirurgie, 1895, 1896. Minsalud-Ascofame: Estudio de Recursos Humanos para Salud y EducaciC MQdicaen Colombia, Metodos y Resultados. Bogota: Carnal Ramirez, 1969 GOKi
RISK
OF INCARCERATION OF INGUINAL HERNIA IN CALI, COLOMBIA*
RAYMOND NEUTRA, ADOLFO VELEZ, RICARD~ Department of Surgery, Colombian National
FERRADA
and RICARDO
GALAN
Universidad del Valle, Cali, Colombia; Ministry of Health. Cali, Colombia
(Received 2 February
1981)
Abstract-We ascertained 248 cases of incarcerated and strangulated inguinal hernias in the city of Cali. Columbia, for the years 1969-1973. An earlier Colombian national survey of hernia prevalence provided us with age-, sex-specific prevalences of hernia which, when applied to the Cali census data, allowed calculation of the appropriate denominator of herniated persons. We found the prevalence of inguinal hernia in men lo increase steadily with age. Risk of incarceration among boys below age IO was nearly 2% per yr. falling at all ages thereafter to a value around 3 per 1000 per year. Using hfe-table methods, we estimate that a 65yr-old man runs a 3.63;, risk of incarcerating his hernia by age 75.
INTRODUCTION FEW epidemiological studies of inguinal hernia made to date [l-3] have not dealt with the risk of incarceration, so that our only estimates of this risk derive from biased THE
clinical studies [4-71. Columbia provides an opportunity to estimate both prevalence and the risk of incarceration. A national sample survey of health conditions in Colombia [8,9] affords an estimate of the prevalence of hernia by age and sex. Application of these rates to the population figures extrapolated from the 1964 and 1973 census of Cali, Colombia, allows estimation of the herniated persons at risk in that city. Because four hospitals provide 90% of the care in Cali, it is possible to ascertain virtually all hospitalized individuals with incarceration or strangulation of hernias over the 5-yr period 1969-1973. By dividing this ‘numerator’ by the ‘denominator’ of herniated persons, one can estimate age-specific hernia incarceration rates, a first step towards identifying groups at potential high risk. MATERIALS
AND METHODS
The data base for the prevalence data in this study comes from the clinical examinations of the ‘Estudio de Recursos Humanos para la Salud y Educacicjn Mtdica en Colombia (1968, 1969); [S, 93 which was carried out by the Colombian Health Ministry and the Association of Colombian Medical Schools with the support and consultation of the Milbank Memorial Fund and the Pan American Health Organization (PAHO). Among the objectives of the survey was that of describing the health status of the Colombian population. To carry out this investigation, a random stratified sample was taken of the noninstitutionalized civilian population of the country. The information was collected by means of home interviews and by clinical examinations carried out between August, 1965 and *Thisstudy
is part of the research activities of the Program of Simplified Surgery at the Universidad del Valle. Cali. Columbia, and was supported by a grant from the Rockefeller Foundation. Part of the analysis was funded by the Robert Wood Johnson Foundation through the Center foi the Analysis of Health Practices at Harvard University, Boston, Massachusetts. and part by the Milbank Fund through the UCLA Milbank Program in Epidemiology and Health Policy. University of California, Los Angeles, California, 561
RAYMONDNEUTRAet al.
562
June, 1966 under the supervision of public health physicians. The home interviews were conducted by medical students in 8669 families with a total of 51,473 persons. The clinical examinations were done by residents in internal medicine and pediatrics. A subsample of the previously interviewed subjects, numbering 5026, was selected for the clinical examinations, on which the present analysis is based. The sampling procedure has been previously described [S, 91. Use of the diagnostic indices at the University Hospital, the San Juan de Dios Hospital, the Social Security Hospital, and the Club Nijel ( a charity pediatric hospital) enabled us to identify all patients discharged between January 1, 1969 and December 31, 1973 with the diagnosis of incarcerated or strangulated inguinal hernia. There were about 50 such patients a year in the city. Age, sex, diagnosis and place of residence were taken from the medical records. The total metropolitan population for Cali in 1963 and 1973, as well as the age-sex composition, was obtained from the National Census, and interpolations were made for the intervening years. Hernia prevalence rates were applied to the population for each of the 5 yr and summed to provide an estimate of the herniated persons at risk. Incarceration cases of appropriate age and sex were divided by the number of herniated persons in that category to provide estimates of the incidence of incarceration. RESULTS
The prevalence of inguinal hernia in the Colombian National Health Survey is shown by age and sex in Table 1. Several points are worth emphasizing. The prevalence of inguinal hernia in men increases ever more rapidly with age, reaching a level of l&20% after age 60. The prevalence in women is never over 2% and does not rise markedly with age. The risk of incarcerating or strangulating an inguinal hernia is shown in Table 2. A yearly risk of 18 per thousand herniated persons is seen for males below age 10, after which the risk falls to about 3 per thousand per year in subsequent intervals. The high risk below age 10 is not seen among females although subsequent rates are somewhat higher than those of males. DISCUSSION
Although we believe the overall impressions from this study to be reliable, the figures here must be regarded as approximations. For one thing, we have applied hernia prevalence figures from a total national survey in the mid-1960s to the population of one city in the early 1970s. We assumed that we had ascertained most of the incarceration cases
TABLE 1. POINT PREVALENCE OF INGUINALHERNIABY AGE AND SEXIN THE 1966 COLOMBIANNATIONALHEALTHSURVEY Females
Age G-9 l&19 2&29 3&39 4ck49 5&59 60-64 65-69 270 Totals
*rt;, = 0.
t&,
Males 0
0,
Ing&al
IngZinal herniat
Denominator
hernia*
876 614 355 291 225 133 38 29 66
0.34 0.65 0 I .03 0.78 1.50 2.63 0 I .52
2627
0.61
= 83.9, 1 dj.
p < 0.001
Age G9 lo-19 2Ck-29 30-39 4&49 5&59 6Ck-64 65-69 270 Totals
Denominator 882 543 290 258 197 117 42 36 36
0.45 1.47 3.10 3.49 3.55 9.40 9.52 11.11 19.44
2401
2.6
Risk of Incarceration
TABLE
2. ESTIMATED
RISK OF STRANGULATING
of lnguinal
OR INCARCERATING
Hernia
AN INGUINAL
Herniated persons
Events
S-9 IO-19
1807 3118
1 2
2IS-29 3@39 4cL-49 5G-59 6G-64
28290 1501 1854 1064
91 13 8 7
6920
23
13,525
46
65-69 270 Total
HERNIA,
BY AGE AND
SEX
Males
Females
Age
563
Incidence
Age
Herniated persons
0.5/1000 0.5/1000
C9 l&19 2&29 3cL-39 40-49 5C59 6Cb64 65-69 270
2539 1455 10.150 8107 6045 9435 3709 2813 6349
45 13 23 20 20 29 21 12 19
17.7/1000 1.7/1000 2.7/10&I 2.5/1000 3.3/1ooo 3.1/1000 5.7/1000 4.3/1000 3.0/1000
56,602
202
3.6/l 000
3.2,GXl 8.7/1000 4.3/1OcCl 6.711000 4.3,&)0 3.4/1000
Total
Events
Incidence
in the city. To check this assumption, we reviewed the 16 deaths attributed to strangulated hernias during the PAHO adult mortality study in 1962 and 1963 [lo]. Four of these deaths occurred outside of the hospital. If one assumed that the case fatality for strangulations treated at home was close to 100X, these four fatal cases would account for all the unhospitalized incarceration cases over the 2-yr period. Thus, in 5 yr one would expect to miss 10 cases or about 4”/, of the 248 cases ascertained during this 5-yr study period. If, on the other hand, the case fatality at home was equal to that in the hospital, our rates would be too low by 25% and should be increased by a factor of 1.25. Thus, instead of 3 per 1000 the risk of incarceration in adults would be 3.8 per 1000. It is very difficult to standardize the procedure for detecting a hernia, and if the Colombian physicians ‘overdiagnosed’ hernias this would inflate the reported prevalence and make our estimate of the risk of incarceration an underestimate. In personal conversations with clinicians concerned with the study, we were told that such ‘overdiagnosis’ was not likely to have occurred. Furthermore, the prevalence of inguinal hernia found on physical examination in Colombia was of the same order of magnitude as the rate of self-reported hernia in the United States National Center for Health Statistics interview study [2] and that of Belcher et al. in Ghana [3]. Both studies show an increasing prevalence of inguinal hernia with age. We therefore consider the prevalence figures to be accurate. Our estimates of the risks of incarceration agree with some previous extimates, also, The risk of inguinal incarceration in adults observed by Berger [7] in Paris has been adjusted to a yearly figure by Neuhauser [ 1l] and was found to be 3.7 per loo0 per year. It is of the same magnitude as our own estimate. Other figures cited in the literature do not specify time periods [4-61. Inguinal hernia in small boys is another matter. The high risk of incarceration in male infants is well recognized by pediatric surgeons. A high proportion of hernias in this age group are congenital [12] and apparently have a different natural history. The reported rates of incarceration vary from I.6 to 18% [12-l 71. When we separated out the 27 incarcerations in male infants that occurred in the first year of life, we estimated the 1-yr incidence to be 2.8%. From age 1 to 9 the rate falls to 1.6% and after age 9 is about 3 per 1000, with approximate confidence intervals ( + 3 SE:) of 2 per 1000 to 6 per 1000 per year. Because the Colombian National Health Survey was a stratified sample, 3 SE is a good estimate of the 95% confidence limit [lS. 191. Except for this excess risk in little boys, there are no striking age-related trends in hernia strangulation. This is of some interest for elderly men in whom the incidence of inguinal hernia itself is particularly high. This high incidence of new hernias in older men means that the surgeon will often be faced with the decision of whether or not to operate upon individuals in this age group. We estimate that the cumulative risk of strangulating an inguinal hernia between ages 65 and 75 is of the order of 34%. In our series the case fatality from incarceration was 12%; thus, the risk of incarceration with death is only 4
564
RAYMONDNEUTRA et al.
per 1000 between ages 65 and 75. Since this is a fairly low risk when compared to the operative risk of elderly persons with a variety of chronic diseases, the surgeon may well let other considerations besides the risk of strangulation influence his decision to operate. For an extended analysis of this problem the reader is referred to the chapter by Neuhauser in a recent book, Costs, Risks and Benejits of Surgery [ll]. Acknowledgements-The authors are grateful to Drs Carlos Agualimpia, William Bertrand, and Daniel Bermeo, and to Srta Gloria Ynez Giraldo for help at various stages of this project. Particular thanks are due the Colombian National Health Survey and the Directors of Hospital Departamental, San Juan de Dios, Club Niiel, and Seguros Sociales for permission to review their data.
REFERENCES I. 2. 3. 4. 5. 6. 7. 8. 9. 10. Il.
12. 13. 14. 15. 16. 17. 18. 19.
Logan RFL, Ashley JSA et al.: Dynamics of Medical Care. Memoir No. 14, London School of Hygiene and Tropical Medicine, p. 42, 1972. National Center for Health Statistics: Prevalence of Selected Chronic Digestive Conditions, United States, 1968, Series 10, No. 83, DHEW Publ. No. (HRA) 74-1510, Table 3, p. 19, 1974. Belcher DW. Nyame PK, Wurapa FK: The prevalence of inguinal hernia in adult Ghanaian males. Trop Ceogr Med 30: 39-43, 1978. Zihmerman LM: External and internal abdominal hernias. Am J Gastroenterol 40: 405-410, 1963. Maingot R: Abdominal Operations. 4th Edn, p. 899. New York: Appleton-Century-Crofts, 1961. Koontz A: Hernia. New York: Appleton-Century-Crofts, 1963. Berger P: Resultat de l’examen de dix mille observations de hernies. Extrait du Neuvleme Congr& Francais de Chirurgie, 1895, 1896. Minsalud-Ascofame: Estudio de Recursos Humanos para Salud y EducaciC MQdicaen Colombia, Metodos y Resultados. Bogota: Carnal Ramirez, 1969 GOKi