Abstract
OBJECTIVES:
We compared the risk of in-hospital mortality and the length of hospital stay between diabetic and non-diabetic patients hospitalized for renal or perinephric abscess.
METHOD:
The data analyzed in this study were retrieved from Taiwan's National Health Insurance claims. The risk of in-hospital mortality and the length of hospital stay were compared between 1,715 diabetic patients, hospitalized because of renal or perinephric abscess in Taiwan between 1997 and 2007, and a random sample of 477 non-diabetes patients with renal or perinephric abscess.
RESULTS:
The in-hospital mortality rates from renal or perinephric abscess for the diabetic patients and the non-diabetic patients were not different, at 2.3% and 3.4%, respectively. However, diabetes was significantly associated with a longer length of hospital stay among patients with renal abscess, by 3.38 days (95% confidence interval [CI]: 1.59-5.17).
CONCLUSIONS:
Diabetes does not increase the risk of in-hospital mortality from renal or perinephric abscess. Nevertheless, appropriate management of patients with diabetes and concurrent renal or perinephric abscess is essential to reduce the length of hospital stay.
Renal Abscess; Diabetes; Mortality; Length of Hospital Stay; Cohort Study
INTRODUCTION
Renal abscess (RA) and perinephric abscess are potentially lethal complications of urinary tract
infections (UTIs). The insidious clinical course and variable symptoms and signs at the time of
clinical evaluation can cause difficulty in the diagnosis of RA, thereby resulting in an increased
case-fatality rate in RA patients (11. Sheinfeld J, Erturk E, Spataro RF, Cockett AT. Perinephric abscess: Current
concepts. J Urol. 1987;137(2):191-4.,22. Dembry LM, Andriole VT. Renal and perirenal abscesses. Infect Dis Clin North Am.
1997;11(3):663-80.). Although progress in imaging studies and the development of percutaneous
drainage techniques for retroperitoneal abscesses have substantially decreased the case-fatality
rate from RA (33. Sundaram M, Wolverson MK, Heiberg E, Pilla T, Vas WG, Shields JB. Utility of CT
guided abdominal aspiration procedures. AJR Am J Roentgenol. 1982;139(6):1111-15,
http://dx.doi.org/10.2214/ajr.139.6.1111.
http://dx.doi.org/10.2214/ajr.139.6.1111...
,44. Meng MV, Mario AL, Mcaninch JW. Current treatment and outcomes of perinephric
abscesses. J Urol. 2002;168(4 Pt 1):1337-440.),
in-hospital mortality rates have remained high, with rates ranging from 5% to 15%, as reported in
several recent studies, including findings from Taiwan (55. Coelho RF, Schneider-Monteiro ED, Mesquita JL, Mazzucchi E, Marmo Lucon A, Srougi
M. Renal and Perinephric Abscesses: Analysis of 65 Consecutive Cases. World J Surg.
2007;31(2):431-6.,66. Lin HS, Ye JJ, Huang TY, Huang PY, Wu TS, Lee MH. Characteristics and factors
influencing treatment outcome of renal and perinephric abscess—a 5-year experience at a
tertiary teaching hospital in Taiwan. J Microbiol Immunol Infect.
2008;41(4):342-50.).
Diabetes is one of the most common endocrine diseases, and its global prevalence for all age
groups worldwide was estimated to be 2.8% in 2000 and is predicted to reach 4.4% in 2030. The total
number of people with diabetes is projected to rise from 171 million in 2000 to 366 million by 2030
(77. Wild S, Roglic G, Green A, Sicree R, King H. Global prevalence of diabetes:
Estimates for the year of 2000 and projections for 2030. Diabetes Care. 2004;27(5):1047-1053,
http://dx.doi.org/10.2337/diacare.27.5.1047.
http://dx.doi.org/10.2337/diacare.27.5.1...
). Diabetes is a serious illness with multiple
complications (88. Stapleton A. Urinary tract infections in patients with diabetes.
Am J Med. 2002;113(Suppl. 1A):80S-84S.,99. Chen HF, Chen P, Su YH, Su HF, Li CY. Age- and sex-specific risks of colorectal
cancers in diabetic patients. Tohoku J Exp Med. 2012;226(4):259-65.)
and premature mortality, and it accounts for at least 10% of the total health care expenditure in
many countries (1010. Hex N, Bartlett C, Wright D, Taylor M, Varley D. Estimating the current and
future costs of Type 1 and Type 2 diabetes in the UK, including direct health costs and indirect
societal and productivity costs. Diabetic Med. 2012;29(7):855-62,
http://dx.doi.org/10.1111/j.1464-5491.2012.03698.x.
http://dx.doi.org/10.1111/j.1464-5491.20...
). Additionally, diabetes has frequently
been found to increase the risk of developing RA (1111. Ko MC, Liu CC, Liu CK, Woung LC, Chen HF, Su HF, et al. Incidence of renal and
perinephric abscess in diabetic patients: a population-based national study. Epidemiol Infect.
2011;139(2):229-35, http://dx.doi.org/10.1017/S095026881000107X.
http://dx.doi.org/10.1017/S0950268810001...
).
Patients with diabetes are at increased risk for infections (1212. Thomsen RW, Hundborg HH, Lervang HH, Johnsen SP, Schønheyder HC,
Sørensen HT. Risk of community-acquired pneumococcal bacteremia in patients with diabetes
mellitus: a population-based case control study. Diabetes Care. 2004;27(5):1143-7,
http://dx.doi.org/10.2337/diacare.27.5.1143.
http://dx.doi.org/10.2337/diacare.27.5.1...
,1313. Casqueiro J, Casqueiro J, Alves C. Infections in patients with diabetes
mellitus: A review of pathogenesis. Indian J Endocrinol Metab. 2012;16 (Suppl.
1):S27-36.), particularly those originating in the urinary
tract (88. Stapleton A. Urinary tract infections in patients with diabetes.
Am J Med. 2002;113(Suppl. 1A):80S-84S.). Diabetes can also cause several changes in the
host defense system, including defects in neutrophil function (1414. Geerlings SE, Meiland R, Hoepelman AI. Pathogenesis of bacteriuria in women with
diabetes mellitus. Int J Antimicrob Agents. 2002;19(6):539-45,
http://dx.doi.org/10.1016/S0924-8579(02)00090-0.
http://dx.doi.org/10.1016/S0924-8579(02)...
), increased bacterial adherence to the uroepithelial cells of diabetic patients (1515. Fünfstück R, Nicolle LE, Hanefeld M, Naber KG. Urinary tract infection in
patients with diabetes mellitus. Clin Nephrol. 2012;77(1):40-8.) and decreased antibacterial activity as a result of glycosuria
(1616. Geerlings SE, Brouwer EC, Gaastra W, Verhoef J, Hoepelman AI. Effect of glucose
and pH on uropathogenic and nonuropathogenic Escherichia coli: studies with urine from diabetic and
non-diabetic individuals. J Med Microbiol. 1999;48(6):535-9,
http://dx.doi.org/10.1099/00222615-48-6-535.
http://dx.doi.org/10.1099/00222615-48-6-...
). As a result, diabetic patients tend to have a higher
incidence and prevalence of bacteriuria (1717. Geerlings SE, Stolk RP, Camps MJ, Netten PM, Hoekstra JB, Bouter PK, et al.
Asymptomatic bacteriuria may be considered a complication in women with diabetes. Diabetes Mellitus
Women Asymptomatic Bacteriuria Utrecht Study Group. Diabetes Care.
2000;23(6):744-9.), and they are at
a higher risk for developing serious consequences, such as emphysematous cystitis, pyelonephritis,
renal papillary necrosis, and abscess (1818. Patterson JE, Andriole VT. Bacterial urinary tract infections in diabetes.
Infect Dis Clin North Am. 1997;11(3):735-50,
http://dx.doi.org/10.1016/S0891-5520(05)70383-4.
http://dx.doi.org/10.1016/S0891-5520(05)...
,1919. Evanoff GV, Thompson CS, Foley R, Weinman EJ. Spectrum of gas within the kidney:
Emphysematous pyelonephritis and emphysematous pyelitis. Am J Med.
1987;83(1):149-154.).
With respect to the prognosis of diabetes-complicated infections, such as bacteremia, sepsis, or
liver abscess, findings from previous studies have been inconsistent (2020. Thomsen RW, Hundborg HH, Lervang HH, Johnsen SP, Schønheyder HC,
Sørensen HT. Diabetes mellitus as a risk and prognostic factor for community-acquired
bacteremia due to enterobacteria: a 10-year, population-based study among adults. Clin Infect Dis.
2005;40(4):628-31, http://dx.doi.org/10.1086/427699.
http://dx.doi.org/10.1086/427699...
21. Thomsen RW, Jepsen P, Sørensen HT. Diabetes mellitus and pyogenic liver
abscess: risk and prognosis. Clin Infect Dis. 2007;44(9):1194-201,
http://dx.doi.org/10.1086/513201.
http://dx.doi.org/10.1086/513201...
22. Foo NP, Chen KT, Lin HJ, Guo HR. Characteristics of pyogenic liver abscess
patients with and without diabetes mellitus. Am J Gastroenterol.
2010;105(2):328-35.-2323. Stegenga ME, Vincent JL, Vail GM, Xie J, Haney DJ, Williams MD, et al. Diabetes
does not alter mortality or hemostatic and inflammatory responses in patients with severe sepsis.
Crit Care Med. 2010;38(2):539-45, http://dx.doi.org/10.1097/CCM.0b013e3181c02726.
http://dx.doi.org/10.1097/CCM.0b013e3181...
). An earlier study (1111. Ko MC, Liu CC, Liu CK, Woung LC, Chen HF, Su HF, et al. Incidence of renal and
perinephric abscess in diabetic patients: a population-based national study. Epidemiol Infect.
2011;139(2):229-35, http://dx.doi.org/10.1017/S095026881000107X.
http://dx.doi.org/10.1017/S0950268810001...
) used a nationally representative diabetic cohort, retrieved
from the National Health Insurance (NHI) database, to investigate the relative risk of RA in
diabetes, and found a significantly increased risk of RA in diabetic patients. Using the same
dataset, the present study further explored whether RA patients with diabetes have an increased risk
of in-hospital mortality and whether they experience an increased length of hospital stay (LOS)
compared to RA patients without diabetes.
MATERIALS AND METHODS
The data analyzed in this study were obtained from our previous study, which investigated the
risk of admission for RA in the diabetic population (1111. Ko MC, Liu CC, Liu CK, Woung LC, Chen HF, Su HF, et al. Incidence of renal and
perinephric abscess in diabetic patients: a population-based national study. Epidemiol Infect.
2011;139(2):229-35, http://dx.doi.org/10.1017/S095026881000107X.
http://dx.doi.org/10.1017/S0950268810001...
). The
previous study, based on Taiwan's NHI claims, used a cohort study design and followed more
than a half million diabetic patients and sex- and age-matched controls from 1997 to 2007.
Briefly, the diabetic cohort consisted of all individuals (n = 500,867) who had an
initial diabetes-related diagnosis (ICD-9: 250 or A code 181) at any time in 1997 and who received
one or more additional diagnoses within the subsequent 12 months. The control subjects
(n = 500,365) were matched to the diabetic cohort according to sex and age and were
identified from the registry of beneficiaries, after the data of the diabetic group were excluded.
Using unique personal identification numbers, we linked the ambulatory claims data of the study
subjects to inpatient claim records (1997-2007) to identify episodes of admission for RA (ICD-9:
590.2). Over 11 years of follow-up, 1,715 diabetic patients were admitted for RA, whereas 477
controls were admitted with the same diagnosis, representing cumulative incidences of 0.34% and
0.10%, respectively. After adjustment for confounders, diabetic patients had a significantly
increased hazard ratio (HR) (3.81) of admission for RA (1111. Ko MC, Liu CC, Liu CK, Woung LC, Chen HF, Su HF, et al. Incidence of renal and
perinephric abscess in diabetic patients: a population-based national study. Epidemiol Infect.
2011;139(2):229-35, http://dx.doi.org/10.1017/S095026881000107X.
http://dx.doi.org/10.1017/S0950268810001...
).
Based on the above-mentioned previous report (1111. Ko MC, Liu CC, Liu CK, Woung LC, Chen HF, Su HF, et al. Incidence of renal and
perinephric abscess in diabetic patients: a population-based national study. Epidemiol Infect.
2011;139(2):229-35, http://dx.doi.org/10.1017/S095026881000107X.
http://dx.doi.org/10.1017/S0950268810001...
), the
present study employed a retrospective cohort design, in which all 1,715 newly diagnosed RA patients
with histories of diabetes were recruited. The control group consisted of 477 newly diagnosed RA
patients without a history of diabetes in 1997. We linked the diabetic and non-diabetic RA patients
to the NHI inpatient claims between the time of their first-time admissions for RA and the last day
of 2007 to examine whether they experienced in-hospital mortality. The information on the LOS of the
study subjects was based on their first-time hospitalization for RA between 1997 and 2007.
To evaluate the effects of diabetes, sex, age, and treatment modality on the risk of in-hospital mortality in RA patients, we applied Cox's multivariate proportional hazard regression analysis, with time to in-hospital mortality as the dependent factor in the model. The index date of follow-up was the RA date of first-time admission between 1997 and 2007. The date of the end of follow-up was the date of discharge from the last hospitalization for individuals who died or the date of termination of the NHI policy or the last day of 2007 for individuals who were censored. The treatment modality included antimicrobials only, percutaneous drainage (International Classification of Disease, 9th version, Clinical Modification [ICD-9-CM], procedure codes: 55.03 or 55.92), surgical drainage (ICD-9-CM procedure codes: 55.01 or 55.02), and nephrectomy (ICD-9-CM procedure codes: 55.51).
We also performed multiple linear regressions to assess the difference in LOS between RA patients with and without diabetes. In addition to diabetic status, age, sex, and treatment modality, we also included geographic area and urbanization level in the multivariate model to account for possible geographic and urbanization variations in cancer incidence and mortality in Taiwan (2424. Chen CJ, You SL, Lin LH, Hsu WL, Yang YW. Cancer epidemiology and control in Taiwan: a brief review. Jpn J Clin Oncol. 2002;32 Suppl:S66-81.). All of the statistical analyses were performed using SAS (version 9.2; SAS institute, Cary, NC). P<0.05 was considered statistically significant. Access to the NHI claims was reviewed and approved by the National Health Research Institutes Review Committee.
RESULTS
The RA patients with diabetes were younger than the control patients (58.2 ±12.4 vs. 64.5 ±9.9 years old). Female patients dominated the samples in both groups. The distributions of geographic areas and urbanization levels were similar in both groups. The treatment modalities used were also similar in both groups (Table 1).
In-hospital mortality, in association with diabetes status, sex, age, and treatment modality, is presented in Table 2). The in-hospital mortality rates for the diabetic RA and non-diabetic RA groups were 2.3% and 3.4%, respectively, which represents a non-significantly reduced covariate-adjusted HR of 0.91 (95% CI: 0.49-1.69, p = 0.759) for RA patients with diabetes. Compared with the female RA patients, male RA patients had a significantly higher hazard rate of in-hospital mortality (adjusted HR = 2.03). Additionally, older age tended to be associated with a higher rate of in-hospital mortality, and the highest adjusted HR (3.86) was noted in the group >64 years old. With regard to treatment modalities, 74.8% of the RA patients received antimicrobial treatment alone, and the corresponding figures for percutaneous drainage, surgical drainage, and nephrectomy were 14.6%, 6.3%, and 4.3%, respectively. The in-hospital mortality rates for RA patients treated with antimicrobials alone, percutaneous drainage, surgical drainage, and nephrectomy ranged from 1.1% to 3.8%, but they were not significantly different across treatment modality.
Table 3) compares the LOS between the two study groups. The mean LOS for RA patients with and without diabetes was 18.89 and 16.19 days, respectively. The covariate-adjusted difference in LOS between the two groups (3.27 days) was statistically significant.
DISCUSSION
Urinary tract infections are among the most common bacterial infections. Renal abscess is a potentially lethal complication of UTIs. Some previous studies have reported the risk factors, clinical presentation, treatment modalities, and outcomes of RA; however, almost all of them were hospital-based (44. Meng MV, Mario AL, Mcaninch JW. Current treatment and outcomes of perinephric abscesses. J Urol. 2002;168(4 Pt 1):1337-440.,55. Coelho RF, Schneider-Monteiro ED, Mesquita JL, Mazzucchi E, Marmo Lucon A, Srougi M. Renal and Perinephric Abscesses: Analysis of 65 Consecutive Cases. World J Surg. 2007;31(2):431-6.,2525. Yen HT, Hu SC, Tsai J, Kao WF, Chern CH, Wang LM, et al. Renal Abscess: Early Diagnosis and Treatment. Am J Emerg Med. 1999;17(2):192-7.,2626. Shu T, Green JM, Orihuela E. Renal and perinephric abscesses in patients with otherwise anatomically normal urinary tracts. J Urol. 2004;172(1):148-50.). To our knowledge, our study is the first to employ a population-based design to investigate the risk of mortality from RA relative to diabetes.
Diabetes and other risk factors for in-hospital mortality among patients hospitalized for RA
Recent hospital-based studies have reported in-hospital mortality rates associated with RA
ranging from 0% to 15% (44. Meng MV, Mario AL, Mcaninch JW. Current treatment and outcomes of perinephric
abscesses. J Urol. 2002;168(4 Pt 1):1337-440.,55. Coelho RF, Schneider-Monteiro ED, Mesquita JL, Mazzucchi E, Marmo Lucon A, Srougi
M. Renal and Perinephric Abscesses: Analysis of 65 Consecutive Cases. World J Surg.
2007;31(2):431-6.,2525. Yen HT, Hu SC, Tsai J, Kao WF, Chern CH, Wang LM, et al. Renal Abscess: Early
Diagnosis and Treatment. Am J Emerg Med. 1999;17(2):192-7.,2626. Shu T, Green JM, Orihuela E. Renal and perinephric abscesses in patients with
otherwise anatomically normal urinary tracts. J Urol. 2004;172(1):148-50.). In
our study, the overall in-hospital mortality rate was estimated at 2.6%, and diabetes did not
increase the risk of in-hospital mortality from RA. Patients with diabetes often have abnormalities
in both cell-mediated and humoral immune responses (2727. Gallacher SJ, Thomson G, Fraser WD, Fisher BM, Gemmell CG, MacCuish AC.
Neutrophils bactericidal function in diabetes mellitus: evidence for association with blood glucose
control. Diabetic Med. 1995;12(10):916-20,
http://dx.doi.org/10.1111/j.1464-5491.1995.tb00396.x.
http://dx.doi.org/10.1111/j.1464-5491.19...
).
Diabetic patients may have an increased risk of dying from an infectious disease, particularly
serious bacterial infections (2828. Shah BR, Hux JE. Quantifying the risk of infectious diseases for people with
diabetes. Diabetes Care. 2003;26(2):510-3,
http://dx.doi.org/10.2337/diacare.26.2.510.
http://dx.doi.org/10.2337/diacare.26.2.5...
). However, evidence obtained
from previous studies has been inconsistent with regard to the prognosis of complicated infections
associated with diabetes.
One population-based epidemiological study suggested that diabetes is an important prognostic
factor for severe Gram-negative infections, including bacteremia, and the authors concluded that
among patients with bacteremia, diabetes was also associated with a poorer prognosis. We speculated
that latent diabetic organ disease would render patients with diabetes particularly vulnerable to
multiorgan failure associated with Gram-negative sepsis. Protracted multiorgan failure promoted by
diabetic organ disease could play a role in the higher mortality among diabetic patients (2020. Thomsen RW, Hundborg HH, Lervang HH, Johnsen SP, Schønheyder HC,
Sørensen HT. Diabetes mellitus as a risk and prognostic factor for community-acquired
bacteremia due to enterobacteria: a 10-year, population-based study among adults. Clin Infect Dis.
2005;40(4):628-31, http://dx.doi.org/10.1086/427699.
http://dx.doi.org/10.1086/427699...
). Another study on the association of diabetes with liver
abscess-related mortality also reported a higher 30-day post-discharge mortality rate in patients
with diabetes. We argue that the harmful effects of hyperglycemia, general diabetic angiopathy, and
decreased immunity may be possible pathophysiological mechanisms (2121. Thomsen RW, Jepsen P, Sørensen HT. Diabetes mellitus and pyogenic liver
abscess: risk and prognosis. Clin Infect Dis. 2007;44(9):1194-201,
http://dx.doi.org/10.1086/513201.
http://dx.doi.org/10.1086/513201...
).
In contrast, Foo et al. (2222. Foo NP, Chen KT, Lin HJ, Guo HR. Characteristics of pyogenic liver abscess
patients with and without diabetes mellitus. Am J Gastroenterol.
2010;105(2):328-35.) demonstrated that in patients
with pyogenic liver abscesses, diabetes was not a predictor of case fatality. We argue that because
the growth of pyogenic liver abscess occurred mostly in immunocompromised patients, other etiologies
of immunodeficiency should be more prevalent in the non-diabetic group (2222. Foo NP, Chen KT, Lin HJ, Guo HR. Characteristics of pyogenic liver abscess
patients with and without diabetes mellitus. Am J Gastroenterol.
2010;105(2):328-35.). Stegenga et al. (2323. Stegenga ME, Vincent JL, Vail GM, Xie J, Haney DJ, Williams MD, et al. Diabetes
does not alter mortality or hemostatic and inflammatory responses in patients with severe sepsis.
Crit Care Med. 2010;38(2):539-45, http://dx.doi.org/10.1097/CCM.0b013e3181c02726.
http://dx.doi.org/10.1097/CCM.0b013e3181...
) also reported that
the outcome of severe sepsis was not influenced by the presence of diabetes. We found no strong
influence of diabetes on the host response to severe sepsis, possibly because sepsis and diabetes
both induced a pro-coagulant state and both interfered with an adequate inflammatory reaction. The
modest effect of pre-existing diabetes on the host response to sepsis may result from disturbances
of the coagulation system and the inflammatory responses caused by severe sepsis being stronger and
more important for outcomes than the relatively smaller derangements attributable to coexistent
diabetes (2323. Stegenga ME, Vincent JL, Vail GM, Xie J, Haney DJ, Williams MD, et al. Diabetes
does not alter mortality or hemostatic and inflammatory responses in patients with severe sepsis.
Crit Care Med. 2010;38(2):539-45, http://dx.doi.org/10.1097/CCM.0b013e3181c02726.
http://dx.doi.org/10.1097/CCM.0b013e3181...
). Along with our earlier report (1111. Ko MC, Liu CC, Liu CK, Woung LC, Chen HF, Su HF, et al. Incidence of renal and
perinephric abscess in diabetic patients: a population-based national study. Epidemiol Infect.
2011;139(2):229-35, http://dx.doi.org/10.1017/S095026881000107X.
http://dx.doi.org/10.1017/S0950268810001...
), the present data indicate that diabetes is associated with a
significantly elevated risk of RA, but diabetes does not increase the risk of in-hospital mortality
from RA.
In our study, 74.8% of patients with RA received antimicrobial treatment alone. We found no differences in the risk of in-hospital mortality among the different treatment modalities. Previous studies have reported that renal abscess can be treated with antimicrobials alone, whereas drainage procedures have always been necessary for perinephric abscess or mixed abscess (55. Coelho RF, Schneider-Monteiro ED, Mesquita JL, Mazzucchi E, Marmo Lucon A, Srougi M. Renal and Perinephric Abscesses: Analysis of 65 Consecutive Cases. World J Surg. 2007;31(2):431-6.,2525. Yen HT, Hu SC, Tsai J, Kao WF, Chern CH, Wang LM, et al. Renal Abscess: Early Diagnosis and Treatment. Am J Emerg Med. 1999;17(2):192-7.,2626. Shu T, Green JM, Orihuela E. Renal and perinephric abscesses in patients with otherwise anatomically normal urinary tracts. J Urol. 2004;172(1):148-50.). Some other studies have also reported that small perinephric abscesses with a diameter <3 cm in clinically stable patients could be treated successfully with antimicrobials alone (44. Meng MV, Mario AL, Mcaninch JW. Current treatment and outcomes of perinephric abscesses. J Urol. 2002;168(4 Pt 1):1337-440.,2929. Siegel JF, Smith A, Moldwin R. Minimally invasive treatment of renal abscess. J Urol. 1996;155(1):52-5.). Compared with previous studies, most of which were conducted in tertiary teaching hospitals or in referral centers, our study found a higher proportion of patients receiving antimicrobials alone as a treatment modality for RA. Patients admitted to tertiary teaching hospitals or referral centers tend to be more severely ill, so drainage procedures are expected to be performed more frequently in such patients. However, our study found no association of treatment modality with the risk of in-hospital mortality, which suggests that the clinical management delivered to RA patients in Taiwan is appropriate.
Although there was no significant association of diabetes or treatment modality with in-hospital mortality from RA, this study did find that male patients and older (>64 years) patients had a significantly higher risk of in-hospital mortality. Yen et al. (2525. Yen HT, Hu SC, Tsai J, Kao WF, Chern CH, Wang LM, et al. Renal Abscess: Early Diagnosis and Treatment. Am J Emerg Med. 1999;17(2):192-7.) reported an in-hospital mortality rate of 14% from RA and found that older age, elevated blood urea nitrogen, and lethargy were all significant risk factors for mortality. Lin et al. reported an in-hospital mortality rate of 8% and noted that age >64 years, thrombocytopenia, and abscess without drainage were risk factors for poor outcome (nephrectomy or mortality); they also found that the patients in the delayed diagnosis group were older than the patients in the early diagnosis group. Delayed diagnosis and co-morbidity in the older patients were found to be responsible for the increased risk of case-fatality from RA (66. Lin HS, Ye JJ, Huang TY, Huang PY, Wu TS, Lee MH. Characteristics and factors influencing treatment outcome of renal and perinephric abscess—a 5-year experience at a tertiary teaching hospital in Taiwan. J Microbiol Immunol Infect. 2008;41(4):342-50.).
It is generally agreed that men with UTIs require thorough urological evaluations to identify
predisposing structural or functional abnormalities, which are common in men with UTIs (3030. Ronald AR. Current concepts in the management of urinary tract infections in
adults. Med Clin North Am. 1984;68(2):335-349.,3131. Schaeffer AJ. Urinary tract infection in men-state of the art. Infection.
1994;22(Suppl 1.):19-21.). Although the
pathogens in men with community-acquired febrile UTIs were similar to those in women, with a
predominance of Escherichia coli (E. coli), and the distributions of E.
coli serotypes were similar between men and women, the distributions of virulence
properties are quite different between men and women (3232. Ulleryd P. Febrile urinary tract infection in men. Int J Antimicrob
Agents. 2003;2(Suppl 2:)2:S89-S93, http://dx.doi.org/10.1016/S0924-8579(03)00228-0.
http://dx.doi.org/10.1016/S0924-8579(03)...
).
Studies have found a higher proportion of hemolytic strains but a lower frequency of P-fimbriated
and aerobactin-producing strains in women, which suggests different host-parasite relationships in
the male and female urinary tracts (3232. Ulleryd P. Febrile urinary tract infection in men. Int J Antimicrob
Agents. 2003;2(Suppl 2:)2:S89-S93, http://dx.doi.org/10.1016/S0924-8579(03)00228-0.
http://dx.doi.org/10.1016/S0924-8579(03)...
). Associated urinary
tract abnormalities and different host-parasite relationships may be responsible for the increased
mortality risk from RA in male patients.
Diabetes-associated length of hospital stay in RA patients
Notably, we found that diabetes increased the LOS by 3.27 days in patients with RA. As the most
common endocrine disease, diabetes was also incorporated into the Charlson Comorbidity Index (CCI),
which takes into account 19 predetermined clinical conditions and is a strong predictor of various
clinical adverse outcomes (3333. Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with
ICD-9-CM administrative databases. J Clin Epidemiol. 1992;45(6):613-9,
http://dx.doi.org/10.1016/0895-4356(92)90133-8.
http://dx.doi.org/10.1016/0895-4356(92)9...
). Yang et al. (3434. Yang Y, Yang KS, Hsann YM, Lim V, Ong BC. The effect of comorbidity and age on
hospital mortality and length of stay in patients with sepsis. J Crit Care.
2010;25(3):398-405.) reported that a higher grade of co-morbidity was significantly
associated with sepsis and therefore with a longer LOS. The longer LOS may have reflected clinical
difficulty in caring for RA patients with diabetes.
Strengths and limitations
Our study had several methodological strengths. First, we used NHI data, which reduced selection or recall bias, and there was little likelihood of non-response and loss to follow-up among the cohort members. Second, the large number of study subjects also made it possible for us to conduct analyses of certain variables of interest, including age, sex, and treatment modality. Third, the advantage of using insurance claims data in clinical research is easy access to longitudinal records for a large sample of geographically dispersed patients, which greatly increases the representativeness of the study sample. Fourth, although we identified RA patients from inpatient claims, most cases of RA in Taiwan are diagnosed by imaging studies, including ultrasound, computed tomography, or magnetic resonance imaging; percutaneous aspiration; and surgical exploration (66. Lin HS, Ye JJ, Huang TY, Huang PY, Wu TS, Lee MH. Characteristics and factors influencing treatment outcome of renal and perinephric abscess—a 5-year experience at a tertiary teaching hospital in Taiwan. J Microbiol Immunol Infect. 2008;41(4):342-50.,2525. Yen HT, Hu SC, Tsai J, Kao WF, Chern CH, Wang LM, et al. Renal Abscess: Early Diagnosis and Treatment. Am J Emerg Med. 1999;17(2):192-7.), which supports the validity of the RA diagnoses.
Several limitations of our study should be noted. First, exclusive reliance on claim data may
have resulted in potential misclassification bias in our study. The accuracy of a single diabetes
diagnosis in the NHI claims data in 2000 was reported to be 74.6% (3535. Lin CC, Lai MS, Syu CY, Chang SC, Tseng FY. Accuracy of diabetes diagnosis in
health insurance claims data in Taiwan. J Formos Med Assoc.
2005;104(3):157-63.). However, we used at least two diabetes-related diagnoses with the first and last visits
more than 30 days apart, which would have largely reduced the likelihood of disease
misclassification. Second, we could not differentiate between type 1 and type 2 diabetes among the
diabetic population included in our study. In Taiwan, type 1 diabetes constitutes only 1.8% of all
types of diabetes (3636. Chuang LM, Tsai ST, Huang BY, Tai TY, DIABCARE (Taiwan) Study Group. The current
state of diabetes management in Taiwan. Diabetes Res Clin Pract.
2001;54(Suppl.1):S55-S65.), and the ratio of newly diagnosed type
2 to type 1 diabetes among school children aged 6 to 18 years old is approximately six to one (3737. Wei JN, Sung FC, Lin CC, Lin RS, Chiang CC, Chuang LM. National surveillance for
type 2 diabetes mellitus in Taiwanese children. JAMA. 2003;290(10):1345-50,
http://dx.doi.org/10.1001/jama.290.10.1345.
http://dx.doi.org/10.1001/jama.290.10.13...
). Therefore, the majority of our young diabetic patients tended
to be type 2 diabetes patients. Third, the study subjects recruited for the current analysis were
originally selected for the investigation of diabetes in predicting RA risk; therefore, the RA
patients analyzed may not be representative of the entire RA population diagnosed during the study
period. To address this issue, we compared characteristics between our study RA patients and other
RA patients hospitalized during the study period. It should be noted that our study RA patients were
older (59.6 vs. 45.4 years). This difference is attributable to our study RA
patients having been selected from the diabetic population and the age- and sex-matched non-diabetic
beneficiaries being older than the general population in general. The in-hospital mortality and
length of hospital stay estimated from our study RA patients were therefore likely to be
over-estimated. Thus, the findings of our analysis should be generalized with caution. Fourth,
Taiwan's NHI claims data do not include laboratory test results, which prevented us from
further evaluating the potential effects of bacterial virulence on the risk of mortality in RA
patients. One study in Taiwan reported that, among the 111 pathogens isolated from abscesses or from
urine samples from RA patients, E. coli was the most common organism (36%),
followed by Klebsiella pneumoniae (20%). Previous studies have also found that the
pathogens of RA are independent of diabetic status, and the RA pathogens did not influence the risk
of mortality (2525. Yen HT, Hu SC, Tsai J, Kao WF, Chern CH, Wang LM, et al. Renal Abscess: Early
Diagnosis and Treatment. Am J Emerg Med. 1999;17(2):192-7.).
Finally, as is the case with most observational studies using linked administrative data, confounding may be a source of concern. We could not determine a comprehensive list of potential risk factors for mortality and LOS in the study subjects, which may also have confounded the study results.
In conclusion, our data show that RA patients with diabetes in Taiwan do not have an elevated risk of in-hospital mortality. However, among the patients hospitalized for RA, male patients and older (>64 years old) patients were at significantly higher risks for in-hospital mortality. Additionally, diabetes may increase the average LOS in RA patients. Given the longer LOS noted in RA patients with diabetes, appropriate clinical management of these patients during their hospital stay is essential to reduce the LOS.
This study was supported by a National Scientific Council grant (NSC100-2314-B-006-052). The interpretation and conclusions contained herein are not representative of BNHI, the Department of Health, or NHRI.
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No potential conflict of interest was reported.
Publication Dates
-
Publication in this collection
2013
History
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Received
18 Mar 2013 -
Reviewed
6 Apr 2013 -
Accepted
6 Apr 2013