- Email: [email protected]
Retroperitoneal Infections by Community Acquired Methicillin Resistant Staphylococcus Aureus
Infection/Inflammation Retroperitoneal Infections by Community Acquired Methicillin Resistant Staphylococcus Aureus Diego A. Abreu,* Fernando Osorio, Luís G. Guido, Gustavo F. Carvalhal† and Laura Mouro From the Departments of Urology, Hospital de Clínicas (DAA, FO, LGG, LM), Montevideo, Uruguay, and Pontifícia Universidade Católica (GFC), Porto Alegre, Brazil
Purpose: We describe the clinical presentation and response to treatment of community acquired, methicillin resistant Staphylococcus aureus retroperitoneal infections. Materials and Methods: A total of 13 patients with unusual retroperitoneal infections who fulfilled Centers for Disease Control criteria for community acquired, methicillin resistant S. aureus were included in this multicenter study, which was done from May 2004 to June 2005. Distinctive features of these infections were noted and treatment alternatives are proposed. Results: Mean patient age was 32 years and 85% of the patients were male. All 13 patients presented with back pain and fever. Infected skin lesions were the presumed portals of entry for bacteria in all cases. Mean time between skin infection and lumbar pain was 48 days. After lumbar pain was established a retroperitoneal abscess was diagnosed at a mean delay of 11 days. An association of foci (kidney, perinephric tissue and psoas) occurred in 85% of cases. Perinephric tissue was the most affected site. Of note, all patients presented with anemia and low serum prothrombin, and required drainage of the retroperitoneal collection. Open drainage was performed in all except 1 patient, in whom percutaneous drainage and antibiotic treatment were sufficient. In 1 patient nephrectomy was necessary. Specific antibiotics were administered as soon as culture results were obtained. Sensitivity was 100% to vancomycin, trimethoprim-sulfamethoxazole, ciprofloxacin and gentamicin. There were no deaths. Conclusions: Three characteristics shared by our patients should be given special consideration, including an infected skin lesion as the possible portal of entry, anemia plus hypoprothrombinemia and frequent involvement of the perinephric region. Treatment with drainage and antibiotic therapy was effective in all cases. Key Words: Staphylococcus aureus, community-acquired infections, retroperitoneal space, abscess, methicillin resistance
lism, osteomyelitis and visceral abscesses, that may evolve to serious septic complications and even death.1,2,10 CA-MRSA infection is an emerging disease with worldwide distribution that is considered one of the major problems in health care today.1 The first cases were reported in 1990 among Australian native aborigines but subsequently there were reports of infection in New Zealand, Europe, Canada and the United States.11–13 In Uruguay CA-MRSA infection was initially reported in 2001 and it became a massive outbreak in 2004. In accordance with the literature most Uruguayan infections were mild with involvement of the skin, while a minority of patients showed severe, invasive disease requiring admission to the intensive care unit.14,15 Having evaluated a series of patients with retroperitoneal infection due to CA-MRSA to our knowledge we describe for the first time aspects of the epidemiology, clinical findings and response to specific treatments of this disease.
n recent years there has been a substantial increase in the incidence and virulence of reported infections due to methicillin resistant Staphylococcus aureus.1 Since these cases were community acquired, affecting healthy children and young adults who did not have predisposing risk factors for hospital acquired infections, they were named CA-MRSA.1,2 Multiple factors favor the spread of CA-MRSA infections, such as confinement, poor hygiene, close contact, and sharing of clothes and other objects of personal use.3– 6 Sexual contact is also associated with these infections, especially among male homosexuals.7,8 Recent investigations aimed at characterizing the strains of CA-MRSA revealed striking differences in epidemiology, genetic signature, clinical presentation, virulence and antibiotic sensitivity compared to those of the hospital acquired variety.9,10 Most cases of CA-MRSA are mild, affecting predominantly skin and soft tissues. However, there are invasive forms, including pneumonia, septic pulmonary embo-
I
MATERIALS AND METHODS Submitted for publication April 24, 2007. * Correspondence: Catedra de Urologia, Oscar Gestide 2786, Apt. 5, Montevideo, Uruguay 12600. † Financial interest and/or other relationship with Novartis and AstraZeneca.
0022-5347/08/1791-0172/0 THE JOURNAL OF UROLOGY® Copyright © 2008 by AMERICAN UROLOGICAL ASSOCIATION
We performed a multicenter, retrospective study from May 2004 through June 2005. Included were 13 patients with a positive culture for CA-MRSA in retroperitoneal infections who were treated at 3 hospitals, that is Hospital de Clínicas
172
Vol. 179, 172-176, January 2008 Printed in U.S.A. DOI:10.1016/j.juro.2007.08.134
RETROPERITONEAL INFECTIONS BY STAPHYLOCOCCUS AUREUS
173
TABLE 1. Patient characteristics Pt No.—Age—Sex 1—17—M 2—31—M 3—38—M 4—65—M 5—23—M 6—21—M 7—30—M 8—36—F 9—21—M 10—37—F 11—25—M 12—30—M 13—32—M Mean 32
Delay (days) Comorbidity
Lesion–Clinic Visit
Visit–Diagnosis
Diagnosis–Treatment
No No No Diabetes mellitus No No No No No No No No No
30 45 90 90 50 20 12 90 90 10 45 30 24 48
3 7 35 30 7 3 2 30 15 0 0 14 1 11
2 1 0 1 0 2 0 0 0 0 2 0 7 1
Of the 13 patients 11 (84.6%) were male and 1 (7.7%) had a comorbid condition.
and Hospital Pasteur in Montevideo, and Hospital de Paysandú (7, 5 and 1 patients, respectively). Inclusion criteria for CA-MRSA infection were those proposed by the Centers for Disease Control and Prevention, including ambulatory patients with cultures positive for MRSA or hospitalized patients with positive cultures obtained within the first 48 hours of admission and without a history of infection by MRSA or hospitalizations in the last 12 months.7 Exclusion criteria were institutionalized patients, patients on chronic dialysis, those using permanent catheters or percutaneous devices and recently operated patients. None of the patients met the exclusion criteria. In the study the variables were demographic data, the portal of entry for the CA-MRSA infection, clinical presentation, mean time between the skin lesion and the onset of specific symptoms, mean time between initial presentation and diagnosis, and mean time between initial presentation and specific treatment. We also evaluated imaging findings, such as the affected retroperitoneal structures and the association of foci, when present. Multi-organ dysfunction, microbiological data, the sensitivity profile to antibiotics, the treatment received and hospital stay were also studied. All collected data were stored in a computerized Microsoft® Excel® database and descriptive statistics were produced using the same software.
than 1 retroperitoneal structure (table 2). The perinephric space was the most commonly affected site (12 of 13 patients or 92.3%). In 2 cases (15.4%) there was associated lung and pleural compromise, which required admission to the intensive care unit. Relevant laboratory findings included anemia and low serum prothrombin time in all cases. Hemoglobin was 6.3 to 11.8 gm/dl (normal 12 to 16) and serum prothrombin was 52% to 68% (normal 70% to 100%). CA-MRSA was confirmed in all patients by culture of the retroperitoneal foci. However, blood cultures were only positive in 23% of cases. Urine cultures were negative in all patients. The antibiotic sensitivity profile was 100% for vancomycin, trimethoprim-sulfamethoxazole, ciprofloxacin and gentamicin (table 3). Specific antibiotic therapy was begun by combining intravenous antibiotics for at least 15 days, followed by oral antibiotics for at least 4 more weeks. After image diagnosis was established the drainage procedure had an average delay of 1 day. All patients required
RESULTS Of the 13 patients 11 were male (84.6%). Mean patient age was 32 years (range 17 to 65). Except for 1 patient with diabetes there were no associated comorbidities in the patients studied (table 1). All patients presented with a history of a suppurated skin lesion, of which 2 were confirmed CA-MRSA infections. All patients presented with fever and lumbar pain, 2 (15.4%) showed symptoms of psoas inflammation and 1 (7.7%) presented with respiratory symptoms. Mean time between the finding of the skin lesion and lumbar pain was 48 days (range 10 to 90). Mean time between the first office or emergency room medical visit and the diagnosis of retroperitoneal infection was 11 days. In all 6 patients in whom ultrasound was used for diagnosis retroperitoneal involvement was confirmed. Abdominal CT, which was performed in all cases, also identified retroperitoneal involvement in all (figs. 1 and 2). When analyzing CT findings, we found that in 85% of cases there was compromise of more
FIG. 1. CT of 31-year-old man reveals CA-MRSA abscess in upper pole of right kidney. Surgical drainage was performed and nephrectomy was unnecessary.
174
RETROPERITONEAL INFECTIONS BY STAPHYLOCOCCUS AUREUS
FIG. 2. CT of 37-year-old man shows left perinephric and psoas CA-MRSA abscess. Percutaneous drainage of collections was performed with 12Fr pigtail catheters and open surgery was unnecessary.
drainage of the retroperitoneal abscesses, which had a mean size of 7.8 cm. All abscesses were drained by open surgery except 1, which was treated percutaneously. Three patients initially underwent percutaneous drainage under CT guidance but they required additional open surgical drainage. In 1 patient nephrectomy was required. None of the patients died. Mean hospitalization was 20 days and all patients recovered after hospital discharge. DISCUSSION Retroperitoneal (kidney/perinephric) abscesses are infrequent nowadays, mainly due to the widespread and prompt use of broad-spectrum antibiotics to manage urinary and skin infections.16 Of retroperitoneal abscesses perinephric ones are more prevalent since they are generally secondary to renal primary infection.17,18 In the pre-antibiotic era most retroperitoneal abscesses were secondary to the hematogenous spread of Staphylococcus infections. In recent decades the incidence of retroperitoneal abscesses due to gram-positive organisms decreased and gram-negative organisms, especially Escherichia coli, became the predominant cause, whether or not associated with urinary lithiasis.18,19 In our series of 13 cases of retroperitoneal abscesses due to CA-MRSA demographic characteristics were similar to those in previous studies performed in our country and abroad concerning CA-MRSA infections.1,2 The possible por-
tals of entry identified in our patients were skin lesions, which were easily remembered due to their severity. Many lesions were multiple, had severe inflammatory signs and had been drained digitally. All required a long time to improve. Additionally, all patients presented with a history of personal contact with other individuals with skin infections, of which most were due to CA-MRSA, during a major CAMRSA outbreak in Uruguay. Although the precise etiology of the skin lesions was not confirmed in most patients and the mean time between the skin lesions and the onset of symptoms was prolonged, we must consider the skin as the possible entry site. This was further corroborated by the absence of other foci of infection and by the fact that the patients were young, healthy and had a normal urinary tract. Thus, it is important to investigate previous skin infections, which may not be routinely evaluated during anamnesis and physical examination. The delay in diagnosis was more likely associated with a lack of clinical suspicion than with the nonspecific clinical symptoms. We observed that it was considerably decreased in the last cases due to the previous knowledge about the possibility of retroperitoneal abscesses related to CA-MRSA. The frequent finding of multiple sites of involvement, eg the perinephric space and psoas muscle, reveals the ability to disseminate and the impressive virulence of CA-MRSA. In most cases this caused large, suppurated collections, of which many were multiloculated and required invasive therapies. Another characteristic finding that differentiates these infections from classic Staphylococcus infections is the fact that CA-MRSA forms collections in the perinephric space instead of in the renal cortex. Regarding imaging, CT had 100% diagnostic sensitivity. Therefore, we consider that CT should be the imaging study of choice when there is clinical suspicion for a retroperitoneal CA-MRSA infection. Anemia and hypoprothrombinemia are not specific to CAMRSA infections. Nevertheless, we believe that these hematological findings may serve as aids in the diagnostic process since their presence was constant in our patients. Additionally, these hematological abnormalities are not consistently described in the literature about renal and perinephric abscesses.17–19 Based in the findings of our series, we suggest that a diagnostic algorithm should be used in the clinical suspicion of CA-MRSA retroperitoneal infections (fig. 3). Regarding medical therapy, we acknowledge that our criteria for establishing the treatment duration was entirely empirical, although we considered parameters such as clinical progress and laboratory markers of infectious activity. An extensive range of antibiotics has been suggested for
TABLE 3. CA-MRSA retroperitoneal infection antibiotic sensitivity profile in 13 patients TABLE 2. Retroperitoneal structures affected by CA-MRSA abscesses Abscess Focus Isolated renal Isolated perinephric Isolated psoas muscle Renal ⫹ perinephric Renal ⫹ perinephric ⫹ psoas Perinephric ⫹ psoas
No. Pts (%)
Antibiotic
No. Pts
1 (7.7) 1 (7.7) 0 1 (7.7) 4 (31) 6 (46)
Oxacillin Erythromycin Clindamycin Trimethoprim-sulfamethoxazole Vancomycin Ciprofloxacin Gentamicin Rifampin
13 9 10 13 5 10 10 1
13
No. Sensitivity (%)
No. Resistance (%)
0 5 (55) 6 (60) 13 (100) 5 (100) 10 (100) 10 (100) 1 (100)
13 (100) 4 (45) 4 (40) 0 0 0 0 0
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175
FIG. 3. Suggested diagnostic algorithm of retroperitoneal infections by CA-MRSA
invasive infections and to our knowledge the optimal therapy for this condition is unknown. However, our choice of antibiotics is accepted by most investigators. For example, the Centers for Disease Control and Prevention stated that the first line antibiotic therapy for severe infections caused by CA-MRSA is vancomycin alone or combined with trimethoprim-sulfamethoxazole, gentamicin or clindamycin.20 Due to its rarity there are no definite guidelines for the treatment of retroperitoneal infections caused by CA-MRSA. The fact that none of our patients died and only 1 required nephrectomy before specific antibiotic therapy may indicate that our treatment options were reasonable. CONCLUSIONS A major challenge in the treatment of retroperitoneal infections is the diagnosis since the clinical presentation is often misleading, and considering that delays in the initiation of treatment may be potentially dangerous. Some practical conclusions may be drawn from our case series and they are important due to the absence of similar reports on CAMRSA in the retroperitoneum to date.
We believe that the clinical picture of a patient with fever and lumbar pain, and a history of skin infection, anemia and hypoprothrombinemia, and a retroperitoneal collection in the perinephric space shown on imaging should indicate with a high level of suspicion the diagnosis of a retroperitoneal abscess caused by CA-MRSA. These infections seem to be associated with a favorable prognosis provided that antibiotic treatment and appropriate drainage procedures are administered in timely fashion.
Abbreviations and Acronyms CA-MRSA ⫽ community acquired, methicillin resistant Staphylococcus aureus CT ⫽ computerized tomography
REFERENCES 1.
Deresinski S: Methicillin-resistant Staphylococcus aureus: an evolutionary, epidemiologic, and therapeutic odyssey. Clin Infect Dis 2005; 40: 562.
176 2.
3.
4.
5.
6.
7.
8.
9.
10.
RETROPERITONEAL INFECTIONS BY STAPHYLOCOCCUS AUREUS Zetola N, Francis JS, Nuermberger EL and Bishai WR: Community-acquired methicillin-resistant Staphylococcus aureus: an emerging threat. Lancet Infect Dis 2005; 5: 275. Guía para el manejo global de las infecciones por Staphilococcus aureus meticilino resistente de origen comunitario (SAMR-com). Uruguay: Ministerio de Salud Publica, August 2004. Groom AV, Wolsey DH, Naimi TS, Smith K, Johnson S, Boxrud D et al: Community-acquired methicillin-resistant Staphylococcus aureus in a rural American Indian community. JAMA 2001; 286: 1201. Salgado CD, Farr BM and Calfee DP: Community-acquired methicillin-resistant Staphylococcus aureus: a meta-analysis of prevalence and risk factors. Clin Infect Dis 2003; 36: 131. Zinderman CE: Community-acquired methicillin-resistant Staphylococcus aureus among military recruits. Emerg Infect Dis 2004; 10: 941. Community-Associated MRSA Information for Clinicians. Centers for Disease Control and Prevention. Division of Health Care Promotion. Available at www.cdc.gov/ncidod/dhqp/ ar_mrsa_ca_clinicians.html. Accessed July 21, 2007. Lee NE, Taylor MM, Bancroft E, Ruane PJ, Morgan M, McCoy L et al: Risk factors for community-associated methicillinresistant Staphylococcus aureus skin infections among HIV-positive men who have sex with men. Clin Infect Dis 2005; 40: 1529. Hiramatsu K, Cui L, Kuroda M and Ito T: The emergence and evolution of methicillin-resistant Staphylococcus aureus. Trends Microbiol 2001; 9: 486. Naimi TS, LeDell KH, Como-Sabetti K, Borchardt SM, Boxrud DJ, Etienne J et al: Comparison of community and health care-associated methicillin-resistant Staphylococcus aureus infection. JAMA 2003; 290: 2976.
11.
Udo EE, Pearman JW and Grubb WB: Genetic analysis of community isolates of methicillin-resistant Staphylococcus aureus in Western Australia. J Hosp Infect 1993; 25: 97. 12. Gosbell IB, Mercel JL, Neville SA, Crone SA, Chant KG, Jalaludin BB et al: Non-multiresistant and multiresistant methicillin-resistant Staphylococcus aureus in communityacquired infections. Med J Aust 2001; 174: 627. 13. Kowalski TJ, Berbari EF and Osmon DR: Epidemiology, treatment, and prevention of community-acquired methicillinresistant Staphylococcus aureus infections. Mayo Clin Proc 2005; 80: 1201. 14. Pedreira W and Galiana A: Samr-C. Artículos. 2004. Available at http://www.smu.org.uy/emc/novedades/samr/index.html; Accessed July 10, 2007. 15. Soca A, Constela I and Pontet J: Staphilococcus aureus meticilino resistente comunitario en Cuidados Intensivos. Buenos Aires: Congreso Mundial de Cuidados Intensivos, August 2005. 16. Lopez E, Arlandis S and Montserrat J: Abscesos renales y perirrenales. Actas Urol Esp 1999; 23: 135. 17. Meng M, Mario L and McAninch J: Current treatment and outcomes of perinephric abscesses. J Urol 2002; 168: 1337. 18. Capitan C, Tejido A and Piedra JD: Retroperitoneal abscesses: analysis of a series of 66 cases. Scand J Urol Nephrol 2003; 37: 139. 19. Shu T, Grenn J and Orihuela E: Renal and perirenal abscesses in patients with otherwise anatomically normal urinary tracts. J Urol 2004; 172: 148. 20. Strategies for Clinical Management of MRSA in the Community: Summary of an Experts’ Meeting Convened by the Centers for Disease Control and Prevention. March 2006. Available at http://www.cdc.gov/ncidod/dhqp/pdf/ar/ CAMRSA_ExpMtgStrategies.pdf. Accessed July 10, 2007.
Purpose: We describe the clinical presentation and response to treatment of community acquired, methicillin resistant Staphylococcus aureus retroperitoneal infections. Materials and Methods: A total of 13 patients with unusual retroperitoneal infections who fulfilled Centers for Disease Control criteria for community acquired, methicillin resistant S. aureus were included in this multicenter study, which was done from May 2004 to June 2005. Distinctive features of these infections were noted and treatment alternatives are proposed. Results: Mean patient age was 32 years and 85% of the patients were male. All 13 patients presented with back pain and fever. Infected skin lesions were the presumed portals of entry for bacteria in all cases. Mean time between skin infection and lumbar pain was 48 days. After lumbar pain was established a retroperitoneal abscess was diagnosed at a mean delay of 11 days. An association of foci (kidney, perinephric tissue and psoas) occurred in 85% of cases. Perinephric tissue was the most affected site. Of note, all patients presented with anemia and low serum prothrombin, and required drainage of the retroperitoneal collection. Open drainage was performed in all except 1 patient, in whom percutaneous drainage and antibiotic treatment were sufficient. In 1 patient nephrectomy was necessary. Specific antibiotics were administered as soon as culture results were obtained. Sensitivity was 100% to vancomycin, trimethoprim-sulfamethoxazole, ciprofloxacin and gentamicin. There were no deaths. Conclusions: Three characteristics shared by our patients should be given special consideration, including an infected skin lesion as the possible portal of entry, anemia plus hypoprothrombinemia and frequent involvement of the perinephric region. Treatment with drainage and antibiotic therapy was effective in all cases. Key Words: Staphylococcus aureus, community-acquired infections, retroperitoneal space, abscess, methicillin resistance
lism, osteomyelitis and visceral abscesses, that may evolve to serious septic complications and even death.1,2,10 CA-MRSA infection is an emerging disease with worldwide distribution that is considered one of the major problems in health care today.1 The first cases were reported in 1990 among Australian native aborigines but subsequently there were reports of infection in New Zealand, Europe, Canada and the United States.11–13 In Uruguay CA-MRSA infection was initially reported in 2001 and it became a massive outbreak in 2004. In accordance with the literature most Uruguayan infections were mild with involvement of the skin, while a minority of patients showed severe, invasive disease requiring admission to the intensive care unit.14,15 Having evaluated a series of patients with retroperitoneal infection due to CA-MRSA to our knowledge we describe for the first time aspects of the epidemiology, clinical findings and response to specific treatments of this disease.
n recent years there has been a substantial increase in the incidence and virulence of reported infections due to methicillin resistant Staphylococcus aureus.1 Since these cases were community acquired, affecting healthy children and young adults who did not have predisposing risk factors for hospital acquired infections, they were named CA-MRSA.1,2 Multiple factors favor the spread of CA-MRSA infections, such as confinement, poor hygiene, close contact, and sharing of clothes and other objects of personal use.3– 6 Sexual contact is also associated with these infections, especially among male homosexuals.7,8 Recent investigations aimed at characterizing the strains of CA-MRSA revealed striking differences in epidemiology, genetic signature, clinical presentation, virulence and antibiotic sensitivity compared to those of the hospital acquired variety.9,10 Most cases of CA-MRSA are mild, affecting predominantly skin and soft tissues. However, there are invasive forms, including pneumonia, septic pulmonary embo-
I
MATERIALS AND METHODS Submitted for publication April 24, 2007. * Correspondence: Catedra de Urologia, Oscar Gestide 2786, Apt. 5, Montevideo, Uruguay 12600. † Financial interest and/or other relationship with Novartis and AstraZeneca.
0022-5347/08/1791-0172/0 THE JOURNAL OF UROLOGY® Copyright © 2008 by AMERICAN UROLOGICAL ASSOCIATION
We performed a multicenter, retrospective study from May 2004 through June 2005. Included were 13 patients with a positive culture for CA-MRSA in retroperitoneal infections who were treated at 3 hospitals, that is Hospital de Clínicas
172
Vol. 179, 172-176, January 2008 Printed in U.S.A. DOI:10.1016/j.juro.2007.08.134
RETROPERITONEAL INFECTIONS BY STAPHYLOCOCCUS AUREUS
173
TABLE 1. Patient characteristics Pt No.—Age—Sex 1—17—M 2—31—M 3—38—M 4—65—M 5—23—M 6—21—M 7—30—M 8—36—F 9—21—M 10—37—F 11—25—M 12—30—M 13—32—M Mean 32
Delay (days) Comorbidity
Lesion–Clinic Visit
Visit–Diagnosis
Diagnosis–Treatment
No No No Diabetes mellitus No No No No No No No No No
30 45 90 90 50 20 12 90 90 10 45 30 24 48
3 7 35 30 7 3 2 30 15 0 0 14 1 11
2 1 0 1 0 2 0 0 0 0 2 0 7 1
Of the 13 patients 11 (84.6%) were male and 1 (7.7%) had a comorbid condition.
and Hospital Pasteur in Montevideo, and Hospital de Paysandú (7, 5 and 1 patients, respectively). Inclusion criteria for CA-MRSA infection were those proposed by the Centers for Disease Control and Prevention, including ambulatory patients with cultures positive for MRSA or hospitalized patients with positive cultures obtained within the first 48 hours of admission and without a history of infection by MRSA or hospitalizations in the last 12 months.7 Exclusion criteria were institutionalized patients, patients on chronic dialysis, those using permanent catheters or percutaneous devices and recently operated patients. None of the patients met the exclusion criteria. In the study the variables were demographic data, the portal of entry for the CA-MRSA infection, clinical presentation, mean time between the skin lesion and the onset of specific symptoms, mean time between initial presentation and diagnosis, and mean time between initial presentation and specific treatment. We also evaluated imaging findings, such as the affected retroperitoneal structures and the association of foci, when present. Multi-organ dysfunction, microbiological data, the sensitivity profile to antibiotics, the treatment received and hospital stay were also studied. All collected data were stored in a computerized Microsoft® Excel® database and descriptive statistics were produced using the same software.
than 1 retroperitoneal structure (table 2). The perinephric space was the most commonly affected site (12 of 13 patients or 92.3%). In 2 cases (15.4%) there was associated lung and pleural compromise, which required admission to the intensive care unit. Relevant laboratory findings included anemia and low serum prothrombin time in all cases. Hemoglobin was 6.3 to 11.8 gm/dl (normal 12 to 16) and serum prothrombin was 52% to 68% (normal 70% to 100%). CA-MRSA was confirmed in all patients by culture of the retroperitoneal foci. However, blood cultures were only positive in 23% of cases. Urine cultures were negative in all patients. The antibiotic sensitivity profile was 100% for vancomycin, trimethoprim-sulfamethoxazole, ciprofloxacin and gentamicin (table 3). Specific antibiotic therapy was begun by combining intravenous antibiotics for at least 15 days, followed by oral antibiotics for at least 4 more weeks. After image diagnosis was established the drainage procedure had an average delay of 1 day. All patients required
RESULTS Of the 13 patients 11 were male (84.6%). Mean patient age was 32 years (range 17 to 65). Except for 1 patient with diabetes there were no associated comorbidities in the patients studied (table 1). All patients presented with a history of a suppurated skin lesion, of which 2 were confirmed CA-MRSA infections. All patients presented with fever and lumbar pain, 2 (15.4%) showed symptoms of psoas inflammation and 1 (7.7%) presented with respiratory symptoms. Mean time between the finding of the skin lesion and lumbar pain was 48 days (range 10 to 90). Mean time between the first office or emergency room medical visit and the diagnosis of retroperitoneal infection was 11 days. In all 6 patients in whom ultrasound was used for diagnosis retroperitoneal involvement was confirmed. Abdominal CT, which was performed in all cases, also identified retroperitoneal involvement in all (figs. 1 and 2). When analyzing CT findings, we found that in 85% of cases there was compromise of more
FIG. 1. CT of 31-year-old man reveals CA-MRSA abscess in upper pole of right kidney. Surgical drainage was performed and nephrectomy was unnecessary.
174
RETROPERITONEAL INFECTIONS BY STAPHYLOCOCCUS AUREUS
FIG. 2. CT of 37-year-old man shows left perinephric and psoas CA-MRSA abscess. Percutaneous drainage of collections was performed with 12Fr pigtail catheters and open surgery was unnecessary.
drainage of the retroperitoneal abscesses, which had a mean size of 7.8 cm. All abscesses were drained by open surgery except 1, which was treated percutaneously. Three patients initially underwent percutaneous drainage under CT guidance but they required additional open surgical drainage. In 1 patient nephrectomy was required. None of the patients died. Mean hospitalization was 20 days and all patients recovered after hospital discharge. DISCUSSION Retroperitoneal (kidney/perinephric) abscesses are infrequent nowadays, mainly due to the widespread and prompt use of broad-spectrum antibiotics to manage urinary and skin infections.16 Of retroperitoneal abscesses perinephric ones are more prevalent since they are generally secondary to renal primary infection.17,18 In the pre-antibiotic era most retroperitoneal abscesses were secondary to the hematogenous spread of Staphylococcus infections. In recent decades the incidence of retroperitoneal abscesses due to gram-positive organisms decreased and gram-negative organisms, especially Escherichia coli, became the predominant cause, whether or not associated with urinary lithiasis.18,19 In our series of 13 cases of retroperitoneal abscesses due to CA-MRSA demographic characteristics were similar to those in previous studies performed in our country and abroad concerning CA-MRSA infections.1,2 The possible por-
tals of entry identified in our patients were skin lesions, which were easily remembered due to their severity. Many lesions were multiple, had severe inflammatory signs and had been drained digitally. All required a long time to improve. Additionally, all patients presented with a history of personal contact with other individuals with skin infections, of which most were due to CA-MRSA, during a major CAMRSA outbreak in Uruguay. Although the precise etiology of the skin lesions was not confirmed in most patients and the mean time between the skin lesions and the onset of symptoms was prolonged, we must consider the skin as the possible entry site. This was further corroborated by the absence of other foci of infection and by the fact that the patients were young, healthy and had a normal urinary tract. Thus, it is important to investigate previous skin infections, which may not be routinely evaluated during anamnesis and physical examination. The delay in diagnosis was more likely associated with a lack of clinical suspicion than with the nonspecific clinical symptoms. We observed that it was considerably decreased in the last cases due to the previous knowledge about the possibility of retroperitoneal abscesses related to CA-MRSA. The frequent finding of multiple sites of involvement, eg the perinephric space and psoas muscle, reveals the ability to disseminate and the impressive virulence of CA-MRSA. In most cases this caused large, suppurated collections, of which many were multiloculated and required invasive therapies. Another characteristic finding that differentiates these infections from classic Staphylococcus infections is the fact that CA-MRSA forms collections in the perinephric space instead of in the renal cortex. Regarding imaging, CT had 100% diagnostic sensitivity. Therefore, we consider that CT should be the imaging study of choice when there is clinical suspicion for a retroperitoneal CA-MRSA infection. Anemia and hypoprothrombinemia are not specific to CAMRSA infections. Nevertheless, we believe that these hematological findings may serve as aids in the diagnostic process since their presence was constant in our patients. Additionally, these hematological abnormalities are not consistently described in the literature about renal and perinephric abscesses.17–19 Based in the findings of our series, we suggest that a diagnostic algorithm should be used in the clinical suspicion of CA-MRSA retroperitoneal infections (fig. 3). Regarding medical therapy, we acknowledge that our criteria for establishing the treatment duration was entirely empirical, although we considered parameters such as clinical progress and laboratory markers of infectious activity. An extensive range of antibiotics has been suggested for
TABLE 3. CA-MRSA retroperitoneal infection antibiotic sensitivity profile in 13 patients TABLE 2. Retroperitoneal structures affected by CA-MRSA abscesses Abscess Focus Isolated renal Isolated perinephric Isolated psoas muscle Renal ⫹ perinephric Renal ⫹ perinephric ⫹ psoas Perinephric ⫹ psoas
No. Pts (%)
Antibiotic
No. Pts
1 (7.7) 1 (7.7) 0 1 (7.7) 4 (31) 6 (46)
Oxacillin Erythromycin Clindamycin Trimethoprim-sulfamethoxazole Vancomycin Ciprofloxacin Gentamicin Rifampin
13 9 10 13 5 10 10 1
13
No. Sensitivity (%)
No. Resistance (%)
0 5 (55) 6 (60) 13 (100) 5 (100) 10 (100) 10 (100) 1 (100)
13 (100) 4 (45) 4 (40) 0 0 0 0 0
RETROPERITONEAL INFECTIONS BY STAPHYLOCOCCUS AUREUS
175
FIG. 3. Suggested diagnostic algorithm of retroperitoneal infections by CA-MRSA
invasive infections and to our knowledge the optimal therapy for this condition is unknown. However, our choice of antibiotics is accepted by most investigators. For example, the Centers for Disease Control and Prevention stated that the first line antibiotic therapy for severe infections caused by CA-MRSA is vancomycin alone or combined with trimethoprim-sulfamethoxazole, gentamicin or clindamycin.20 Due to its rarity there are no definite guidelines for the treatment of retroperitoneal infections caused by CA-MRSA. The fact that none of our patients died and only 1 required nephrectomy before specific antibiotic therapy may indicate that our treatment options were reasonable. CONCLUSIONS A major challenge in the treatment of retroperitoneal infections is the diagnosis since the clinical presentation is often misleading, and considering that delays in the initiation of treatment may be potentially dangerous. Some practical conclusions may be drawn from our case series and they are important due to the absence of similar reports on CAMRSA in the retroperitoneum to date.
We believe that the clinical picture of a patient with fever and lumbar pain, and a history of skin infection, anemia and hypoprothrombinemia, and a retroperitoneal collection in the perinephric space shown on imaging should indicate with a high level of suspicion the diagnosis of a retroperitoneal abscess caused by CA-MRSA. These infections seem to be associated with a favorable prognosis provided that antibiotic treatment and appropriate drainage procedures are administered in timely fashion.
Abbreviations and Acronyms CA-MRSA ⫽ community acquired, methicillin resistant Staphylococcus aureus CT ⫽ computerized tomography
REFERENCES 1.
Deresinski S: Methicillin-resistant Staphylococcus aureus: an evolutionary, epidemiologic, and therapeutic odyssey. Clin Infect Dis 2005; 40: 562.
176 2.
3.
4.
5.
6.
7.
8.
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