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Infectious Disorders - Drug Targets
Year 2020
ISSN: 2212-3989 (Online)
ISSN: 1871-5265 (Print)
Methicillin-Sensitive Staphylococcus Aureus Pyogenic Iliopsoas Abscesses:
A case series from Jodhpur, India.
1
Parag Vijayvergia1, Neeraja Vijayan1, Naresh K Midha1, Deepak Kumar1, Maya Gopalakrishnan1,
Sarbesh Tiwari2, Mahendra K Garg1
1
Department of Medicine, All India Institutes of Medical Sciences Jodhpur, Rajasthan, India; 2Department of Diagnostic
and Interventional Radiology, All India Institute of Medical Sciences, Jodhpur, India
Abstract: Early recognition of iliopsoas abscess is important for limiting morbidity and mortality. Mycobacterium tuberculosis remains an important cause of iliopsoas abscess in developing countries and most patients are initiated on empirical anti-tubercular therapy. In this context, methicillin-sensitive Staphylococcus aureus (MSSA) as a cause of iliopsoas abscess is
rare in India. Four cases were diagnosed with pyogenic iliopsoas abscesses caused by MSSA. Half of the patients had typical clinical triad of fever, difficulty in walking and backache. Primary iliopsoas abscesses was present in three patients. All
patients were managed with percutaneous drainage and antibiotics with favourable outcome. MSSA as a cause of primary
iliopsoas abscesses is rare in India. Early diagnosis of microbial aetiology also minimizes undesirable use of antibiotics and
anti-tubercular therapy.
Keywords:Pyogenic Iliopsoas Abscesses, Psoas sign, Sacroiliitis,
Mycobacterium Tuberculosis, Gram Positive Bacterial Infection
Methicillin-Sensitive
Staphylococcus
Aureus,
1. INTRODUCTION
Pyogenic iliopsoas abscess is pus collection in the iliopsoas compartment, which extends from the lateral borders of the
vertebral bodies T12–L5, to the iliacus and the insertion of psoas muscle into the lesser trochanter of the femur [1]. Psoas
abscess may be primary and secondary. Primary iliopsoas abscess is thought to develop as a result of unrecognized bacteraemia
whereas secondary occurs from local spread like vertebrae, gastrointestinal or genitourinary tract infections [2, 3].
The common microbiological aetiology of the primary psoas abscess in tropics is Mycobacterium tuberculosis [4, 5]. The
culture yield in iliopsoas abscess is less than 50% and hence most of the patients are treated with empirical anti-tubercular
therapy [4]. Pyogenic iliopsoas abscesses are uncommon disease and Staphylococcus aureus (S. aureus) followed by
Escherichia coli have been reported as common microbial causes [6]. In contrast to tuberculosis, risk factors and outcomes for
_______________________________________________
*Address correspondence to this author at the Department of Medicine, All India Institutes of Medical Sciences Jodhpur, Rajasthan (India); Tel: 9116396922;
E-mail: deepak1007sharma@gmail.com
S. aureus pyogenic iliopsoas abscess are not well studied in developing nations [7]. Here, we report four cases of MSSA
pyogenic iliopsoas abscess from our centre who presented over a period of one year and discuss risk factors and implications
for management.
2. CLINICAL CASE SERIES
2.1. Patient A
A 22-year female presented with complaints of fever, shortness of breath, pain in sacral area with difficulty in walking for 10
days. The pain was sharp, radiated to the lower back, and aggravated by hip movement. Left flank and gluteal region were
tender on palpation. There was restriction of movement of left hip joint. On systemic examination, pansystolic murmur was
heard on left parasternal area and crepitations were present in both lung fields. Laboratory investigations are mentioned in
Table 1. Chest X-ray was suggestive of left lower lobe consolidation and echocardiography revealed Tetralogy of Fallot (TOF).
Ultrasonography abdomen and pelvis revealed heteroechoic area probably iliopsoas abscess. Magnetic Resonance Imaging
(MRI) was consistent with bilateral sacroiliitis and left psoas abscess (Figure 1a & 1b). Because of high erythrocyte
sedimentation rate (ESR) and high sensitive C-reactive protein (hsCRP), tuberculosis was strongly suspected, however, blood
and ultrasound guided pus (drainage) culture showed the growth of MSSA.
Figure 1: Short TI inversion recovery (STIR) coronal image of lumbosacral image (Fig 1a) shows abnormal collection along
the left psoas muscle and the iliacus with associated muscle edema (red arrow). The axial fat-saturated T2 weighted (T2FS)
image (Fig 1b) shows the abscess along left iliacus muscle (white arrow). Note hyperintensity and collection along bilateral
sacro-iliac joint (green arrow) suggestive of sacroiliitis.
2.2. Patient B
A 40-year-old female presented to the emergency department with complaints of pain in left hip joint for last 8 days,
breathlessness, dry cough, and fever for last 4 days. The patient had tenderness on left hip joint extension. On chest
auscultation, air entry was reduced in bilateral basal zones. Laboratory evaluation was suggestive of neutrophilic leucocytosis
with raised markers of inflammation (Table 1). Chest X-ray showed obliteration of bilateral costophrenic angles. Patient was
initially treated with intravenous piperacillin-tazobactam empirically and planned for further workup. Computed Tomography
(CT) of thorax and abdomen found bilateral psoas abscess (Left>Right) with bilateral pleural effusion (left>Right) (Figure 2a
and 2b). The abscess was drained with ultrasound guided drainage. Microbiological culture and sensitivity of pleural fluid, pus
as well as blood revealed MSSA.
Figure: 2. The contrast enhanced abdomen CT coronal (Fig 2a) and axial (Fig 2b) image shows peripherally enhancing abscess
along bilateral psoas muscles (red arrow). Note associated bilateral pleural effusion. Axial contrast image at the level of L2
vertebra (Fig 2b) also shows the presence of subcutaneous abscess along the left paraspinal region ( white arrow).
Table 1. Demographic variables, laboratory parameters and outcome of patients with iliopsoas abscess
Variables
Patient A
Patient B
Patient C
Patient D
Age (years)
22
40
40
50
Sex
Female
Female
Male
Male
Duration of illness
10 days
10 days
15 days
15 days
Psoas involvement
Unilateral (left)
Bilateral (left >right)
Bilateral
Unilateral (right)
Co-morbidities
TOF physiology
Bronchiectasis
-
T2DM,
DKD
B/L pyelonephritis
Probable Source
Sacroiliitis
Sacroiliitis
Diskitis
Genitourinary tract
Total Leucocyte
13.4
37.6
19.6
25.59
N81, L12,M5
N89, L6, M4
N87, L6,M7
N91 L3 M6
ESR (mm/1st hour)
111
80
89
87
HsCRP (mg/dL)
187
260.6
94.5
240
Ferritin (ng/mL)
1160
310
400
1082
Urea (mg/dl)
56
56
35
93
Creatinine (mg/dl)
1.64
0.77
0.95
2.58
AST/ALT (U/L)
61/21
20/28
63/82
27/20
Blood culture
MSSA
MSSA
MSSA
MSSA
Pus culture
MSSA
MSSA
MSSA
MSSA
Mycobacterium
No growth
No growth
No growth
No growth
Favourable
Favourable
Favourable
Favourable
3
Counts (x10 /cumm)
Differential
Leucocyte
Counts (%)
culture
Outcome
2.3. Patient C
A 40-year male farmer patient presented with complaints of low backache for 15 days and fever for last 10 days. The patient
was febrile, and there was local tenderness in lower dorsal and upper lumbar vertebrae with pitting edema on both lower limbs.
Laboratory investigations were found raised inflammatory markers (Table 1). MRI spine and hip were suggestive of
infective/inflammatory pathology of D11-12 spine level and intramuscular collections in bilateral iliopsoas compartment with a
paraspinal extension (Figure 3a, 3b & 3c). Pus was aspirated and sent for culture and sensitivity which yielded MSSA. The
patient clinically improved with resolution of pain and swelling. The patient was discharged with diagnosis of MSSA
septicaemia, with pyomyositis and psoas abscess.
2.4. Patient D
A 50-year male with type-2 diabetes mellitus and diabetic kidney disease presented to emergency department with complaint of
right hip pain with difficulty in walking for last 15 days and fever of 2 days. It was associated with decreased appetite,
drowsiness, and nausea for last 2 days. Patient had a history of left pyelonephritis two months back along with left renal stone
for which Ureteral double J (DJ) stenting was performed. Physical examination was unremarkable except for moderate
tenderness in the right loin. He also had evidence of intense inflammation (Table 1). Ultrasonography of abdomen and pelvis
was suggestive of bilateral pyelonephritis with right psoas abscess. Non-contrast (because of underlying diabetic kidney
disease) MRI abdomen and pelvis revealed bilateral pyelonephritis with right psoas abscess. USG guided pigtail insertion was
placed. Blood and pus culture and sensitivity showed MSSA.
Figure 3. The axial T2 images at level D10 (Fig 3a) & D11 ( Fig 3b) shows multiple abscess along bilateral paraspinal muscles,
right psoas muscle. A small subcutaneous abscess (red arrow) is also noted along right paraspinal region. The sagittal T2FS
image (Fig 3c) shows hyperintensity of D12 vertebra with posterior epidural abscess extending from D10 to D12 vertebra
(green arrows).
Demographic data, laboratory investigations, co-morbidities and outcome of these cases are depicted in Table 1.
All patients were treated with appropriate antibiotics according to sensitivity pattern. Mean duration of hospital stay was 9 ± 3
days.
3. DISCUSSION
The iliopsoas abscess is relatively uncommon infectious syndrome presents with fever, difficulty in walking, and back pain [8].
This clinical triad is present in fewer than half of the patients and it makes the diagnosis delayed and often difficult. In our case
series, 50% of the patients had this clinical triad. The psoas sign (passive extension of the thigh leads to a worsening of lower
abdominal pain on the affected side in supine position) is present in only up to 24% cases with iliopsoas abscess [6]. The psoas
sign was present in 50% of patients in our study. The male female ratio is equal (1:1) and the mean age was 38 ± 11.7 years
with no mortality in our case series. A number of previous case series also showed higher age associated with increased
mortality (mean age ≥ 60 years) [6, 9], while younger age had good prognosis [10].
A Study by Ricci et al in 1986 showed around 90% iliopsoas abscess were primary [11]. While later studies found that
secondary iliopsoas abscess is more common than primary [12, 13]. This may be due to increased use to immunosuppressant
drugs in treatment of diseases associated with secondary iliopsoas abscess like Crohn’s disease. In developing countries like
India where the tuberculosis is still an endemic disease, iliopsoas abscess secondary to Pott’s spine (vertebral tuberculosis) is
common [14]. This is spread by hematogenous or direct extension from thoraco-lumber vertebral osteomyelitis [15]. Primary
iliopsoas abscess is often bacterial in aetiology and relatively less common in India. Contrary to previous data our case series
has demonstrated primary iliopsoas abscess (75%) caused by MSSA. While in developed countries where tuberculosis is rare,
the secondary psoas abscesses are commonly associated with gastrointestinal inflammatory diseases such as appendicitis,
Crohn’s disease, and renal pathology [6].
The microbial aetiology of iliopsoas abscess is broad which includes a range of bacterial and fungal agents [16, 17]. A study by
Rodrigues et al from Vellore, India found Miycobacterium tuberculosis as the most common cause of iliopsoas abscess
followed by methicillin resistance Staphylococcus aureus (MRSA) [4]. Another report by Gupta et al from India also found
Mycobacterium tuberculosis as the most common cause of iliopsoas abscess [5]. While a large case series from Spain showed
S. aureus as the most common cause of iliopsoas abscess and most were MSSA [13]. Ricci et al concluded that S. aureus was
the most common causative bacteria in 88% cases of pyogenic psoas abscess followed by Streptococcus (5%) and Escherichia
coli (3%) in developed countries [11]. The aetiology of iliopsoas abscess could be ascertained only in less than half of patients
in India and most of the patients had received empirical anti-tubercular treatment [4, 5]. Our case series emphasises MSSA as
an important cause of iliopsoas abscess. We suggest that changing pattern of causative organism and increased sensitivity of
culture techniques in India has led to an increase in the diagnosis of MSSA related iliopsoas abscess. This also highlights the
need to employ rational use of antitubercular therapy in the cases of iliopsoas abscess in India.
A high index of suspicion is required for early diagnosis because delay in diagnosis is associated with high mortality.
Haematological and serological parameters are non-specific like anaemia, leucocytosis and raised inflammatory markers which
are not helpful in early diagnosis [4]. Early imaging should be planned in all suspected cases of iliopsoas abscess. Most of
psoas abscesses are diagnosed with the help of ultrasound, computed tomography, and/or magnetic resonance imaging. CT is
more accurate than ultrasound for the correct diagnosis of psoas abscess [18]. MRI is helpful for assessing early or infiltrating
tumours and it is extremely sensitive in the detection of tumour or infection spreading into the adjacent vertebrae, discs or
canals [2]. In our series, two patients were diagnosed by contrast CT and two were by non-contrast MRI (because of deranged
renal function). Percutaneous drainage of iliopsoas abscess with adjuvant appropriate antibiotic therapy is preferred modality of
treatment. Surgical drainage is associated with significant mortality and recurrence as compared to percutaneous drainage [19].
In our case series, all cases were treated with ultrasound guided percutaneous drainage with adjuvant appropriate antibiotic
therapy and improved without complication.
CONCLUSION
Tuberculosis is the most common reported cause of iliopsoas abscess in developing countries while MSSA as a cause of
iliopsoas abscess has been infrequently reported in India. The clinician in tropics should be aware of this rare iliopsoas abscess
aetiology. The antibiotic of choice for MSSA iliopsoas abscess is flucloxacillin or clindamycin. Early diagnosis of microbial
aetiology also minimizes undesirable use of antibiotics and anti-tubercular therapy.
ETHICS APPROVAL AND CONSENT TO PARTICIPATE
Not applicable.
HUMAN AND ANIMAL RIGHTS
Not applicable.
CONSENT FOR PUBLICATION
Not applicable.
STANDARD OF REPORTING
CARE guidelines and methodology have been followed in this study.
FUNDING
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
CONFLICT OF INTEREST
The authors declare no conflict of interest, financial or otherwise.
ACKNOWLEDGEMENTS
Declared none.
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