Acute Appendicitis Risks of Complications: Age and Medicaid Insurance

Acute Appendicitis Risks of Complications: Age and Medicaid Insurance

Susan L. Bratton

ABBREVIATIONS. LOS, length of stay; HMO, health maintenance organization; OR, odds ratio; CI, confidence interval.

Appendicitis is the most common surgical emergency of childhood. Although there has been a general decline in the incidence of acute appendicitis,[1,2] the percentage of children with perforation-complicating acute appendicitis has not changed.[2-4] The incidence of complicated pediatric appendicitis (perforation or peritoneal abscess) ranges from 30% to 74% depending on age,[3,5-10] and morbidity and mortality are increased in patients with these complications.[3,6,11]

Duration of symptoms has been shown to be associated with rupture,[7,9,12,13] and delay of surgical treatment after onset of symptoms is the strongest predictor of perforation.[12-14] Hence, rapid surgical management is essential. Low socioeconomic status, poor access to primary care,[15] and lack of medical insurance[16] may contribute to delays in definitive surgical management, increase the risk of perforation, prolong hospital length of stay (LOS), and increase medical costs.[16,17]

Results from a large study of adults with acute appendicitis reported that patients without insurance and those with Medicaid coverage had a higher risk of perforation or peritoneal abscess than did patients who received care under a health maintenance organization (HMO).[16] Likewise, investigators from a single pediatric institution reported that children with Medicaid coverage had longer duration of symptoms before care and a higher rate of perforation, compared with patients with either HMO coverage or fee-for-service insurance.[17]

Increasing proportions of young children in the United States rely on Medicaid coverage. We speculated that children with Medicaid insurance would have increased risk of complicated disease during acute appendicitis. We examined all cases of acute appendicitis in children from Washington State over a 10-year period to evaluate medical insurance as a potential risk factor for complications of acute appendicitis. Changes in the annual incidence of acute appendicitis among children, the proportion of children with perforation, and LOS were also examined and analyzed by medical insurance coverage.


After institutional review board approval by the University of Washington and the State of Washington Health and Human Services Department, we obtained computerized information that is available for all persons hospitalized in Washington State from 1987 through 1996. Subjects were included if they had a principal diagnosis code for acute appendicitis (International Classification of Diseases codes 540.0, 540.1, or 540.9[18]) and if they were [is less than] 17 years old. Uncomplicated acute appendicitis was defined as acute appendicitis without peritonitis, abscess, or rupture (code 540.9). Complicated cases of acute appendicitis were defined as appendiceal rupture (code 540.0, acute appendicitis with peritonitis reflecting gross perforation), or acute appendicitis complicated by peritoneal abscess (code 540.1, reflecting microperforation). The total complications were the sum of cases with gross perforation and abscess formation.

Variables that were examined in the analysis included age, gender, zip code of residence, source of hospital admission (emergency department, physician’s office, or inpatient hospital transfer), and hospital of admission. A maximum of 6 International Classification of Diseases diagnosis codes and 6 procedure codes were examined, as well as LOS and survival. Specific diagnosis codes for prematurity, cerebral palsy, and mental retardation were identified because they might be associated with increased risk for perforation attributable to impaired ability to communicate symptoms. Primary payer codes were identified. Patients without a primary payer code and those in relatively small payer groups such as Medicare were excluded from the analysis.

The annual incidence of acute appendicitis was determined using census data from Washington State. When calculating the rate for the 15- to 16-year-olds, the Washington State census data for 15- to 19-year-olds were assumed to be evenly distributed within the age bracket.

Patient age was categorized as: 0 to 4 years, 5 to 9 years, 10 to 14 years, and 15 to 16 years old. Hospitals were indexed to the number of annual pediatric admissions, based on information from the State of Washington Health and Human Services defining a child as a person who is [is less than] 17 years old. Number of pediatric admissions were categorized as 0 to 500, 501 to 1000, 1001 to 3500, 3501 to 10 000, and [is greater than] 10 000 annual admissions in 1996. Children who were transferred from another inpatient facility were only counted once and were assigned to the final hospital of care for analysis.

Normally distributed continuous data were compared using Student’s t test and 1-way analysis of variance. The Tukey-B test was used to adjust for multiple pair-wise comparisons. The Kruskal-Wallis H test was used to compare skewed continuous data. Categorical data were examined using the [chi square] test. The relationship of payer status with complications of acute appendicitis in children was examined by calculating adjusted odds ratio (OR) using multiple logistic regression (SPSS 7.5 for Windows, SPSS Inc, Chicago, IL) to control for potential confounding variables, such as gender and age. The adjusted OR was reported with 95% confidence intervals (CIs). Analyses were performed for gross perforation and peritoneal abscess formation separately and then combined as total complicated cases. Statistical significance was defined as P [is less than] .05.


There were 13 532 children with acute appendicitis in Washington State from 1987 to 1996. Five (.04%) died. Appendicitis was more common in boys of all ages (Table 1). The annual incidence was greatest for boys 10 to 14 years old and girls 15 to 16 years old. Subjects for whom the primary payer was not recorded (n = 240) and for those patients covered by Medicare (n = 29), Worker’s Compensation (n = 5), and Indian Health Services or Champus (n = 206) were excluded from additional analysis because of small group size.

TABLE 1. Age- and Gender-Specific Incidence of Acute Appendicitis From 1987 to 1996 in Washington State

Age (in Years) Incidence/100 000/Year

Boys Girls

0-4 18.4 13.4

5-9 105.4 82.5

10-14 226.1 149.2

15-16 212.5 180.5

Clinical characteristics for the remaining 13 052 children are shown in Table 2. Sixty percent of children with acute appendicitis were boys. Twenty-four percent of children with acute appendicitis had gross perforation, while 8% had acute appendicitis complicated by peritoneal abscess. The perforation rate was highest in young children (Table 2). Forty-six percent of children [is less than] 5 years old had gross perforation and 19% had abscess formation, compared with 19% and 6%, respectively, in 15- to 16-year-olds. Complication rates did not differ between girls and boys. Only 21 children with acute appendicitis had diagnosis codes for cerebral palsy, mental retardation, or prematurity; 11 of these (52%) had perforation. The total complication rate varied only slightly by hospital annual pediatric admission volume (30%-32%) except for a single center with [is greater than] 10 000 annual pediatric admissions (47%). The total complication rate was 30% for children referred from an emergency department, 35% for children referred from a physician’s office, and 48% for children from another inpatient facility.

TABLE 2. Clinical Characteristics of Children With Acute Appendicitis

Uncomplicated Appendicitis With

Appendicitis Gross Perforation

(570.9) (570.0)

n = 8816 n (%) n = 3143 n (%)


0-4 y 210 (34) 283 (46)

5-9 y 2218 (63) 994 (28)

10-14 y 4555 (71) 1394 (22)

15-16 y 1833 (75) 472 (19)


Male 5282 (68) 1884 (24)

Female 3534 (67) 1259 (23)

Volume: pediatric

hospital admissions(*)

0-500 1155 (70) 351 (21)

501-1000 1196 (69) 410 (24)

1001-3500 4700 (67) 1705 (24)

3501-10 000 1284 (71) 359 (20)

>10 000 440 (53) 306 (37)

Source of referral

Emergency department 5491 (70) 1868 (24)

Office 3190 (65) 1219 (25)

Inpatient transfer 62 (62) 38 (37)

Other source 73 (70) 18 (17)


HMO 1419 (69) 483 (23)

Commercial 5233 (69) 1729 (23)

Self-pay 579 (67) 216 (25)

Medicaid 1585 (62) 715 (28)

LOS (d, mean, SD) 2.3 (2.2)([dagger]) 5.5 (5.3)([double



With Abscess


n = 1093 n (%)


0-4 y 116 (19)

5-9 y 323 (9)

10-14 y 502 (8)

15-16 y 152 (6)


Male 631 (8)

Female 462 (9)

Volume: pediatric

hospital admissions(*)

0-500 146 (9)

501-1000 123 (7)

1001-3500 566 (8)

3501-10 000 176 (10)

>10 000 79 (10)

Source of referral

Emergency department 533 (7)

Office 528 (11)

Inpatient transfer 19 (19)

Other source 13 (13)


HMO 160 (8)

Commercial 599 (8)

Self-pay 70 (8)

Medicaid 264 (10)

LOS (d, mean, SD) 7.0 (4.4)

SD indicates standard deviation.

(*) 1996 data, hospital identity not recorded in 56 cases.

([dagger]) Less than appendicitis with gross perforation and appendicitis with abscess.

([double dagger]) Less than appendicitis with abscess.

The total complication rate was 31% for children with commercial insurance or HMO coverage, although the total complication rate for children receiving Medicaid was significantly higher (38%). At the same time, Medicaid was the primary payer for 36% of children [is greater than] 5 years old, compared with 16% of 15- to 16-year-olds with acute appendicitis.

The relationship of payer status and age with complications did not differ for children with gross perforation or peritoneal abscess formation, so the 2 groups were combined as complicated disease for the adjusted analysis presented in Table 3. The risk of complicated disease among children with Medicaid as the primary payer was 1.3 (OR: 1.3; 95% CI: 1.2-1.4) after adjustment for other potential confounding features, such as age. The risk of complicated disease for children without any medical insurance was 1.1; however, this increased risk was not statistically significant (OR: 1.1; 95% CI: 1.0-1.3). Children [is less than] 5 years old had a 5-fold greater risk of complicated disease, compared with teenagers 15 to 16 years old (OR: 4.9; 95% CI: 4.0-5.9). Children who received care in a center with [is greater than] 10 000 annual admissions had a 1.8-fold increased risk of perforation, compared with children treated at smaller facilities (OR: 1.8; 95% CI: 1.5-2.0). Patients initially managed in the emergency department were less likely to have complicated disease, compared with children who were referred to the hospital from an office practice (OR: .7; 95% CI: .7-.8).

TABLE 3. Risk Factors Associated With Complicated Acute Appendicitis

Characteristic Adjusted OR(*) 95% CI


0-4 y 4.9 4.0-5.9

5-9 y 1.6 1.4-1.8

10-14 y 1.2 1.1-1.3

15-16 y 1 Reference group

Male 1.0 .9-1.1

Pediatric referral

center([dagger]) 1.8 1.5-2.0

Referral source

Emergency department .7 .7-.8

Other sources 1.0 Reference group

Hospital transfer 1.4 .8-2.3


Medicaid 1.3 1.2-1.4

Self-insured 1.1 1.0-1.3

HMO 1.0 .9-1.1

Commercial insurance 1 Reference group

(*) Values indicate the likelihood of perforation given all the other variables are in the model.

([dagger]) Greater than 10 000 annual pediatric admissions.

Overall, average LOS over the 10-year period significantly decreased for all acute appendicitis diagnosis codes (LOS data not shown). The mean LOS for uncomplicated acute appendicitis in 1987 was 2.7 days, compared with 2.1 days in 1996. Likewise in 1987, the LOS for appendicitis with gross perforation and peritonitis was 6.5 days, compared with 4.6 days in 1996. The average LOS for children with commercial insurance (3.3 [+ or -] 4.0 days) or HMO insurance (3.5 [+ or -] 3.1 days) was significantly shorter than LOS for self -insured children (3.7 [+ or -] 5.8 days) or children with Medicaid insurance (4.0 [+ or -] 3.7 days). Among children with uncomplicated disease, Medicaid patients had statistically significant longer mean stays (2.5 [+ or -] 1.9 days) than did children with commercial insurance or HMO coverage (2.3 [+ or -] 2.1 and 2.3 [+ or -] 1.3 days, respectively). Medicaid patients with complicated disease also had statistically significant longer mean stays (6.3 [+ or -] 4.2 days) than did children with commercial insurance (5.7 [+ or -] 5.7 days). Children with HMO medical insurance and complicated disease had shorter mean stays (6.0 [+ or -] 6.7 days) than did children with Medicaid insurance; however, this difference was not statistically significant.


We found that the proportion of children with complicated disease did not change during the 10-year period. Young children had the lowest incidence of acute appendicitis, but they had a 5-fold greater risk of complicated disease than 15- to 16-year-old teenagers. Children who were covered by Medicaid insurance had increased risk of complicated appendicitis, compared with children with commercial insurance or HMO coverage after adjustment for potential confounding variables, such as age. Finally the LOS for uncomplicated and complicated disease significantly decreased over the study.

We confirmed that young children experience the greatest risk for perforation.[6,10,13] Several factors may account for this finding. First, the lower incidence of acute appendicitis in infants and young children may render physicians less suspicious of appendicitis when they examine a small child with acute abdominal pain. Second, limited ability of infants and small children to communicate their symptoms may contribute to delays in care. Finally, the findings of our study suggest that disproportionately high Medicaid coverage in this group may be associated with delays in care and increased risk of complications in acute appendicitis.

We found that medical coverage by Medicaid was associated with an increased risk of complicated disease. Our results are similar in magnitude to the risk reported by Braveman et al.[16] in adult Medicaid patients with acute appendicitis. In addition, we found that children with acute appendicitis and Medicaid coverage had statistically significant longer hospital stays than did children with commercial insurance, although this difference may not be clinically significant. We did not demonstrate a significantly increased risk of advanced disease in children who had no medical coverage. The relatively small number of children in our study without any medical coverage (7%) may have limited our ability to detect a statistically significant association. Also, children without medical insurance may represent a somewhat diverse group that includes very poor families who are eligible for Medicaid, poor families who are Medicaid ineligible, working class families who have lost insurance coverage as a work benefit,[19] and relatively well-to-do families who have chosen self-insurance. Other studies have demonstrated that uninsured patients and those covered by Medicaid use less health services than do patients with insurance[20,21]; therefore, they may have a higher risk for delay in diagnosis and complications. This finding is particularly compelling because 21% of American children are currently insured by Medicaid and 15% have no health insurance.[22]

Like Braveman et al,[16] we found that patients who were referred from an emergency department for hospital admission experienced a decreased risk of complicated disease. This association may be attributable to expedited medical care for patients in emergency departments, compared with patient referred from other care providers. However, our study could not evaluate this potential explanation. We also found that children who were treated at a very large center had an increased risk of complicated disease even after adjustment for hospital transfer. The higher risk of complicated disease at the largest center probably reflects a selection bias for sicker patients.

Our study has several limitations. First, the discharge codes are based on surgical not pathologic diagnoses, and the diagnosis codes recorded in the discharge data were not verified. However, the State of California audited the codes for acute appendicitis and reported that they are reported reliably in discharge data.[23] Second, we could not confirm all comorbidity diagnosis codes, which may be associated with either poverty or impaired patient ability to communicate symptoms leading to increased risk of perforation. Third, we did not have information about children from Washington State who received inpatient care for acute appendicitis in other states. Finally, our study did not have information concerning patient race and ethnicity, factors that have been associated with an increased risk of perforation? However, Washington State is a relatively homogenous state with 91% white Americans, 3% black Americans, 4% Asian or Pacific Islanders, and 2% Native Americans in 1990.

Our findings indicate that children in Washington State with Medicaid insurance coverage had increased risk of complicated acute appendicitis and longer hospital LOS. Given the relatively common occurrence of acute appendicitis nationwide and the high proportion of children covered by Medicaid, this finding has significant public health and financial implications. Future investigations are needed to identify specific factors that may account for this finding and may be amenable to change.


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[20.] Braveman PA, Egerter S, Bennett T, Showstack J. Differences in hospital resource allocation among sick newborns according to insurance coverage. JAMA. 1991;226:3300-3308

[21.] Hafner-Eaton C. Physician utilization disparities between the uninsured and insured: comparisons of the chronically ill, acutely ill, and well nonelderly populations. JAMA. 1993;269:787-792

[22.] Medical Expenditure Panel Survey (MEPS). Available at: http:// Accessed June 2, 1996

[23.] California Hospital Facilities Commission, Health Facility Data Division. Draft Report of a Reliability Study of California Discharge Data Set for Calendar Year 1983. Sacramento, CA: California Hospital Facilities Commission; 1987

Susan L. Bratton, MD, MPH(*)([sections]); Charles M. Haberkern, MD, MPH(*)([sections]); and John H. T. Waldhausen, MD:([double dagger])([parallel])

From the Departments of (*)Anesthesiology and Pediatrics and ([double dagger])Surgery, University of Washington School of Medicine; and Departments of ([sections]) Anesthesia and Critical Care and ([parallel])Surgery, Children’s Hospital and Regional Medical Center, Seattle, Washington.

Received for publication Jul 12, 1999; accepted Oct 26, 1999.

Reprint requests to (S.L.B.) Oregon Health Sciences University, 3181 SW

Sam Jackson Park Rd, Portland, OR 97201. E-mail:

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