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The role of cross sectional imaging in the management of acute pyogenic inguinal abscess - extrapelvic versus intrapelvic origin
© Hsu et al.; licensee BioMed Central Ltd. 2013
Received: 2 May 2012
Accepted: 22 March 2013
Published: 27 March 2013
Abscesses involving the inguinal region as manifestations of complex soft-tissue infections are rare, and the infectious route is usually unclear. The purpose of this study was to ascertain the importance of imaging study and whether the clinical presentations differ between the extrapelvic and intrapelvic origin.
Patients who presented with inguinal abscess between January 2003 and December 2010 were evaluated retrospectively. All patients received broad-spectrum antibiotic therapy and debridement. Imaging studies, including computed tomography or magnetic resonance imaging, were performed in all patients to elucidate the origin and extent of infectious disease, and the results were reviewed. Clinical data, laboratory examination findings, and culture results were analyzed.
Twenty-eight patients were enrolled in the study: 13 patients whose infections were of extrapelvic origin (Group 1) and 15 patients of intrapelvic origin (Group 2). Imaging studies yielded information that helped guiding the treatment. Gram-positive coccus infection was more frequent in Group 1 (p < 0.001), while mixed pathogen and anaerobic bacterial infection were more frequent in Group 2 (p = 0.002 and p = 0.006, respectively). Group 2 had a higher incidence of history of malignancy and chronic renal failure (p = 0.044 and p = 0.038, respectively).
Computed tomography and magnetic resonance imaging are helpful in diagnosing cases of inguinal abscess and determining the extent of infection. In patients presenting with acute pyogenic inguinal abscess, a higher prevalence of chronic renal failure and history of malignancy were found in those with an intrapelvic, as compared with an extrapelvic, origin of infection.
Inguinal abscesses as manifestations of deep soft-tissue infections are complex and rare, and the infectious route is usually unclear. The inguinal region communicates with the peritoneal or retroperitoneal space and thigh through several routes, including the psoas sheath, femoral canal, sacrosciatic notch, pudendal canal, and obturator foramen [1, 2]. It has been reported that inguinal abscesses may arise from peritoneal or retroperitoneal abscesses, such as ruptured appendicitis, colonic diverticulitis, and pyelonephritis [3–5]. Hence, the infection may be of extrapelvic or intrapelvic origin [6–11]. Understanding the etiology of the inguinal abscess is helpful in guiding definitive treatment and the prescription of empiric antibiotics. Inguinal abscesses resulting from extrapelvic pyomyositis usually appear as well-defined cavities, while those resulting from intrapelvic infection may be complicated by underlying bowel disease, infective spondylodiskitis, or urinary tract infection [9–20]. Empiric antibiotics and surgical planning should be guided by the pathophysiology of the disease. Computed tomography (CT) and magnetic resonance imaging (MRI) are valuable diagnostic tools. It is currently unclear whether the presentation and prognosis for patients with acute pyogenic inguinal abscess differ according to whether the infection is of extrapelvic versus intrapelvic origin.
A retrospective study was performed to investigate the clinical manifestations and outcomes in patients who presented with acute pyogenic inguinal abscess. Such information may facilitate more accurate prediction of the outcome for patients as well as guide better management of this disease. Approval for this study was obtained from the institutional review board of Chang Gung Memorial Foundation.
Under the approval of institutional board review of Chang Gung Memorial Foundation (100-0667B), the medial records of three hundred and forty six patients diagnosed with the ICD code 6822 (cellulitis and abscess, trunk) from Chang Gung Memorial Hospital at Chia Yi were comprehensively reviewed between January 2003 and December 2010. The inclusion criteria were a presentation groin mass associated with fever greater than 38.3 degree at emergency department that demanded surgical treatment. Twenty-eight patients diagnosed with inguinal abscess and treated with surgical debridement were included in the current study. Medical records, laboratory examination results, and imaging findings were retrospectively reviewed and analyzed. Patients with inguinal abscess presented with a swollen, erythematous, and tender inguinal mass. Most patients experienced a gradual onset of a limping gait, fever, and chills. Inguinal abscess was confirmed by CT or MRI, along with surgical findings. The CT or MRI features in patients with inguinal abscess included the following: (1) asymmetrical enlargement of the underlying affected muscle, (2) “ring sign,” or rim enhancement of the abscess wall with lower central attenuation, and (3) air bubbles.
Upon diagnosis of an inguinal abscess, the treatment strategy included broad-spectrum antibiotic therapy, aggressive resuscitation, and adequate debridement. Microbial infection was confirmed by culture results from soft tissue or blood collected in the emergency department (ED) and during surgery. The antibiotic regimen was modified appropriately after the microbial culture results were obtained. Intensive care and aggressive resuscitation, including fluid challenge and inotropic drugs, were administered to maintain mean arterial pressure above 65 mm Hg. Surgical planning was based on imaging findings. If an extrapelvic origin of infection was identified, debridement of the inguinal abscess along with the extrapelvic site was performed by an orthopedic surgeon. If the imaging findings showed an intrapelvic origin of infection, combination surgery involving colorectal or urologic surgeons was performed.
The patients were divided into two groups for further analysis: those with an extrapelvic origin of infection (Group 1) and those with an intrapelvic origin of infection (Group 2). Extrapelvic origin was defined as that thigh represented the primary infectious focus. On the other hand, when the infectious focus was located within the pelvic cavity including intraperitoneal, retroperitoneal and genitourinary pathology, it was defined as intrapelvic origin.
Clinical parameters including age, gender, comorbidities, clinical manifestations, laboratory findings at the time of admission, bacteriologic findings, APACHE II score, length of hospital stay, and mortality were recorded and compared.
All statistical analyses were performed using SPSS, version 10.0 (SPSS Inc, Chicago, IL). The Wilcoxon rank sum test was used for discontinuous variables, and the Fisher exact test was used for continuous variables. Statistical significance was set at a p value of <0.05.
Clinical and demographic data of patients with inguinal abscess
This series consisted of 28 patients. The median patient age was 60.5 years. Nineteen patients (67.9%) were male. Most patients were immunocompromised (78.6%). Diabetes mellitus (77.3%) was the leading disease in immunocompromised patients. Computed tomography and MRI constituted good diagnostic tools in all patients.
Group comparison of clinical characteristics
Group comparison of clinical characteristics
57.8 (23, 89)
62.9 (52, 75)
4.4 (2, 28)
6.2 (2, 30)
27.3 (5, 144)
9.4 (3, 25)
Chronic renal insufficiency
Chronic viral hepatitis
ICU stay(patient number)
APACHE II score
16.6 (11, 26)
20.6 (13, 27)
38.2 (5, 126)
Soft tissue reconstruction
STSG or FTSG
Group comparison of laboratory data and microbiology
Group comparison of laboratory data
Leukocytosis or leutropenia
12.2 (8.0, 15.3)
10.2 (6.7, 14.2)
C-reactive protein (mg/dL)
205.6 (15.7, 458)
262.9 (120, 412)
153.8 (91, 249)
220.3 (81, 497)
137.6 (124, 149)
131.7 (122, 137)
48.9 (15, 85)
34.6 (14, 187)
Hypoalbuminemia (<2 g/dL)
Positive blood culture
Positive wound culture
Positive blood and wound culture
Summary of microbiology
Extraplevic origin (n=13)
Intrapelvic origin (n=15)
Gram positive pathogen
-Group B Streptococcus
Gram negative pathogen
One patient in each group died in severe sepsis and multi-organ failure despite of broad spectrum antibiotics and surgical debridment.
Patients with pyogenic inguinal abscess of extrapelvic origin presented with different predisposing comorbidities as compared with patients with abscess of intrapelvic origin. Patients with an intrapelvic origin of infection were more likely to have chronic renal failure and history of malignancy than patients with an extrapelvic origin of infection. This finding was consistent with previous reports that immunodeficiency, chronic renal insufficiency, and malignancy predisposed patients to intrapelvic infection [12, 21]. Patients with an intrapelvic origin of infection had higher incidences of anemia and hyponatremiam, which might result from intra-abdominal or pelvic abscesses [22–24]. Decreased hemoglobin and serum sodium were found to be factors in poor prognosis in cases of pelvic infection [25, 26]. More aggressive resuscitation, intensive care, and debridement are therefore recommended when an inguinal abscess of intrapelvic origin is suspected based on coexisting disease, clinical manifestations, and laboratory findings.
Treatment includes antibiotic therapy and surgical drainage of the abscess. Broad-spectrum antibiotic therapies should be chosen based on clinical presentation and cross sectional images in the ED. Penicillin or ampicillin plus an aminoglycoside is the typical antibiotic regimen . Anaerobic coverage (metronidazole or clindamycin) is added when infection of intrapelvic origin is suspected. Computed tomography and MRI are helpful in diagnosing cases of possible abscess and determining the extent of infection [12, 28].
The present study was limited by the small number of patients and the retrospective design. However, the occurrence of inguinal abscess was not common, with only 28 patients over an 8-year period.
Computed tomography or MRI is helpful in determining the extent of the abscess and guiding the treatment plan. Higher APACHE II scores within 24 hours of hospital admission, higher incidences of anemia and hyponatremia, and a higher prevalence of chronic renal failure and history of malignancy were observed in patients with abscess of intrapelvic, as compared with extrapelvic, origin. Treatment protocols including aggressive resuscitation, rapid administration of antibiotics, and immediate surgical intervention are recommended for all patients presenting with acute pyogenic inguinal abscess.
Sources of funding
There are no external funding.
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