Abstract
From 1998 to 2008, six patients with pyogenic psoas abscesses were managed. Pain and fever were the most common presentations. Two patients had primary pyogenic abscesses and four had secondary pyogenic abscesses. The diagnoses were made either by computed tomography scans (50%) or magnetic resonance imaging and pus culture were obtained. The associated conditions included: perinepheric abscess (1); lumbar discitis (2); and infected thrombosed abdominal aortic aneurysm (1). Five patients underwent radiologically-guided percutaneous drainage and one required open surgical drainage of the abscess cavity. Optimal results were achieved in all cases except one who died of acute myocardial infarction.
Introduction
Pyogenic psoas abscesses (PSA) is a rare clinical entity with a varied clinical spectrum. It starts and extends through the retro facial iliopsoas muscle to the inguinal region. Primary PSA is of a haematogenous origin and secondary PSA develops from an adjacent infectious process which frequently arises from the kidney, spine or bowel. 1 , 2 Delayed diagnosis is common because of the rarity of the condition and the insidious nature of the infection. Computed tomography (CT) scans and magnetic resonance imaging (MRI) could, therefore, play an important role in the early diagnosis and management of patients with PSA. 3 , 4 The clinical spectrum, aetiology and treatment of PSA managed at this institution are discussed.
Methods
A retrospective chart review was made of all patients aged >14 years who had been treated at the Aga Khan University Hospital, Karachi, from 1998 to 2008, and who had been diagnosed as having a ‘pyogenic psoas abscess’. The objective of the study was to identify the predisposing factors, microbiology, clinical features, diagnostic modalities and therapeutic outcomes of PSA. The inclusion criteria were psoas abscesses with proven bacterial infection on a pus culture. Patients with tubercular abscesses were excluded from the study. Demographic information, clinical symptoms, signs, radiological investigations, bacteriological examination, therapeutic approach and outcome were recorded in Performa and analyses were done on SPSS-14.
Results
Six cases of PSA were managed over 10 years. The male to female ratio was 2:1. The mean hospital stay was 10.2 days and the mean follow-up was 6 months. All patients presented with abdominal, lower backache or hip pain; five had fever at presentation. Other symptoms and signs were groin swelling (2), vomiting (2) and difficulty in walking (1). Two patients, aged 15 and 21 years, had primary PSA and in four the underlying secondary causes were identified. The average age of patients with secondary abscess was 67.5 years and all were suffering from diabetes mellitus. Two patients had spinal discitis, one had renal pyonephrosis and renal calculus and another had an infected thrombosed abdominal aortic aneurysm. In three patients the diagnoses were made with a CT scan and in the other three with an MRI scan. Five underwent percutaneous drainage of the abscess cavities. Ultra-sound was used for two patients and three had CT-guided drainage of their abscess cavities. One patient with pyonephrosis required extraperitoneal surgical drainage of the abscess cavity along with drainage of pyonephrosis. A pus culture showed a mono-organism in four patients – Staphylococcus aureus (2); β-Hemolytic streptococci (1); Escherichia coli (2) – and poly-organisms in only one patient (candida, streptococcus and E. coli).
We were able to achieve a better outcome for all patients (Table 1) except one 78-year-old woman with primary PSA who died of an acute myocardial infarction during her hospital stay. No recurrence of abscess was noted in any patient during the follow-up period.
Cases summary
MRI, magnetic resonance imaging; CT, computed tomography; US, ultrasound, DM, diabetes mellitus; HTN, hypertension; IHD, ischaemic heart disease; AAA, abdominal aortic aneurysm
Review of the published literature
D, surgical drainage; PCD, percutaneous drainage; C, conservative; P, primary psoas abscess; S, secondary psoas abscess; CT, computed tomography
Discussion
PSA, a rare entity, can present with a wide spectrum of signs and symptoms, often non-specific, leading to a delay in the diagnosis. The clinical triad of fever, flank pain and limited hip movement can be seen in a small proportion of patients with PSA. In this study most of the patients presented with lower abdominal pain radiating to the hip, lower backache and fever.
The CT scan is reported to be the best imaging technique for the detection of psoas abscesses. Nevertheless, it is not sufficiently specific for the differentiation of a psoas abscess from a neoplasm or a haematoma. 5 Zissin et al. reported that the CT scan was an effective imaging modality for diagnosing iliopsoas abscess, even when classic clinical presentations were not present. The optimal results were achieved with CT-guided percutaneous drainage of PSA (Table 2). 6 The present series proves the importance of the diagnostic and therapeutic role of CT scans in the diagnosis of PSA.
S. aureus (88.4% of cases) were reported to be the most common pathogen present in primary PSA: other pathogens being streptococcus (4.9%) and E.Coli (2.8%). 7 The present case series shows a similar pattern of organism but the noted difference was diabetes mellitus in patients with secondary PSA.
In most cases, treatment is based on the use of the appropriate antibiotics in conjunction with drainage of the abscess. 8 Open drainage is reported to be associated with a significantly high morbidity compared to percutaneous drainage. 9 Similar results were reported by Baier et al. in a series of 40 patients: 32 (80%) underwent open drainage with a reported mortality of 15% and there was a recurrence of abscess in 15 patients who had to be operated on again (Table 2). 10 Radiologically-guided drainage of PSA was reported to be an effective treatment in >95% of patients, with low morbidity and no mortality in a series of 21 cases. 11 We also noted the effectiveness of percutaneous drainage in all cases with desirable outcomes. Surgical drainage may be considered in patients with secondary PSA, due to the spread of the disease from coexisting pathology in adjacent structures such as the bowel or kidney. However, the coexisting underlying pathology should be managed as an interval procedure once the PSA has been managed with radiologically-guided percutaneous drainage. One patient in this series underwent surgical drainage of PSA along with drainage of pyonephrosis. In retrospect, both PSA and pyonephrosis could have been managed with percutaneous drainage. Surgery may also be required if the percutaneous drainage fails because of very thick pus or when it is multiloculated. In the literature, mortality rates of up to 19% have been reported in secondary PSA. 12 In the present series desirable results were achieved in all four patients with secondary abscesses.
Conclusion
PSA is rare and a high level of clinical suspicion and the liberal use of radiological imaging (CT and MRI scan) will enable an early diagnosis. Most of the patients could be managed with radiologically-guided drainage with optimal results. Open surgical drainage should be reserved for failed percutaneous drainage and in patients with secondary PSA. Prolonged catheter drainage, appropriate antibiotics and treatment of the underlying urinary and bowel pathology are essential for the successful treatment of PSA.