Case report

CASE  REPORT

136

Acta Medica Indonesiana - The Indonesian Journal of Internal Medicine

Giant Primary Psoas Abscess: Masquerading Peritonitis- 

for Diagnosis and Treatment

Rikki Singal

1

, Amit Mittal

2

,

 

Samita Gupta

2

, Bikash Naredi

1

, Maihail Singh

1

1

 Department of Surgery, Maharishi Markandeshwer Institute of Medical Sciences and Research, Mullana, (Distt-

Ambala) Pin code–133201, Haryana, India. 

2

 Department of Radiodiagnosis and Imaging, Maharishi Markandeshwer 

Institute of Medical Sciences and Research, Mullana (Distt-Ambala) Pin code–133201, Haryana, India.

Correspondence mail: 

dr. Kundan Lal Hospital, Ahmedgarh, Distt-Sangrur, Pin code-148021, Punjab, India. email: [e-mail].

ABSTRAK

Abses primer otot psoas merupakan kesatuan klinis tersendiri dengan gambaran klinis dan patogenesis 

yang masih samar dan belum jelas. Kepustakaan tentang hal ini pun masih sangat sedikit. Abses otot psoas 

merupakan fenomena klinis yang jarang terjadi, sangat sulit didiagnosis dan perlu pemeriksaan yang teliti. 

Artikel ini menekankan pada pentingnya pemeriksaan ultrasonografi dan tomografi komputer serta peranan 

pengobatan dalam kasus ini. Pada kasus ini, seorang pasien perempuan berusia 15 tahun datang dengan nyeri 

dan kembung di bagian perut. Kami melaporkan suatu kasus yang sangat jarang terjadi, yakni abses psoas 

raksasa bilateral yang didiagnosis sebagai peritonitis. Pemeriksaan ultrasonografi menunjukkan bahwa abses 

pada otot psoas kiri ternyata mengalami ruptur ke arah anterior dalam rongga peritoneum dan menyebabkan 

abses intraperitoneal, tetapi pemeriksaan tomografi komputer menunjukkan gambaran yang berbeda. Pada 

kasus ini, pemeriksaan tomografi komputer memiliki peranan penting dalam tatalaksana abses psoas. Kasus 

ini ditatalaksana dengan baik secara konservatif, yakni dengan drainase dan pengobatan antibiotik. Pasien 

pulang dari rumah sakit dalam kondisi yang baik dan memuaskan. Pada evaluasi lanjut 9 bulan kemudian, 

kondisi pasien baik dan tidak mengalami gejala lagi.

Kata kunci: peritonitis, bilateral, ultrasonografi, tomografi komputer, drainase pembedahan.

ABSTRACT

Primary psoas abscess is a distinct clinical entity with vague clinical presentation and obscure pathogenesis, 

although the literature regarding it is sparse. Psoas muscle abscess is an uncommon clinical phenomenon, 

extremely difficult to diagnose and needs to be investigated with considerable thoroughness. We emphasize 

the importance of ultrasonography and computed tomography along with role of the treatment. A 15-year old 

female presented with pain and distention of the abdomen. We report an extremely rare case of bilateral giant 

psoas abscess diagnosed as peritonitis. Ultrasonography showed abscess of the left psoas muscle which ruptured 

anteriorly into the peritoneal cavity and caused intraperitoneal abscess but computed tomography revealed 

different picture. In our case, computed tomography has the main role in the diagnosis/management of the psoas 

abscess. Conservative treatment was given using antibiotics and drainage. The patient was discharged in good 

condition. In follow-up period of 9 months, she remained well and asymptomatic.

Key words: peritonitis, bilateral, ultrasonography, computed tomography, surgical drainage.

Vol 45 • Number 2 • April 2013                                          Giant primary psoas abscess: Masquerading peritonitis

INTRODUCTION 

Primary psoas abscess (PPA) potentially 

carries high mortality and morbidity, if diagnosis 

is delayed.

1

 It carries a good prognosis provided 

early drainage is performed and parenteral 

antibiotic therapy is administered to the patient. 

The worldwide incidence was 12 cases per 

100,000 per year in 1992, but the current 

incidence is unknown.

The psoas muscle has a rich vascular supply 

that is believed to predispose it to hematogenous 

spread from sites of occult infection. Psoas abscess 

(PA) can also be secondary to gastrointestinal 

or renal pathology through direct infection of 

adjacent structures. The most common causes 

are appendicitis, diverticulitis, Crohn’s disease 

and carcinoma. The organisms responsible for 

infection are Gram-negative germs (Escherichia 

coli, Klebsiella spp., Pseudomonas aeruginosa, 

Proteus mirabilis, Enterobacter spp.) and 

Gram-positive  cocci (Staphylococcus aureus, 

Staphylococcus epidermidis, Streptococcus 

agalactiae, α-hemolytic streptococci, especially 

Streptococcus mitis). It can also be of tuberculous 

etiology and associated with cold abscesses of 

lower thoracic and upper lumbar vertebral bodies, 

as the psoas is attached to these vertebrae.

2

Psoas muscle abscess is an uncommon clinical 

phenomenon, which needs to be investigated 

thoroughly for the proper management. Modern 

imaging techniques such as ultrasonography, 

computed tomography (CT), magnetic resonance 

imaging (MRI) and radionuclide scans allow 

more rapid diagnosis and decrease the morbidity 

and mortality of patients with PA.

3

 However, at 

the initial stage of the disease, the negative results 

of image studies often make the physicians 

ignore the possibility of psoas pathology.

PPA carries a good prognosis, if early 

drainage is performed and parenteral antibiotic 

therapy administered which provide a safe 

alternative to more invasive surgical drainage 

in most of patients. High index of clinical 

suspicion is required for the diagnosis of psoas 

abscess. Rarely, psoas abscess can extend to the 

abdominal compartment presenting as peritonitis 

as giant abscess bilaterally, as seen in our patient. 

Awareness of this disease entity, careful physical 

examination and appropriate imaging studies 

such as ultrasonography, computed tomography 

and magnetic resonance imaging are the key to 

make a correct diagnosis.

CASE ILLUSTRATION

A 15 year-old female presented with pain in 

the abdomen, fever, vomiting. The pain was more 

present in the right pelvic region and limping 

occured of a few days duration. There were no 

history of diarrhea or any urinary symptoms. 

She complained of tenderness on palpation or 

percussion of his lumbar vertebrae. She had 

taken treatment from in the form of analgesics 

and antibiotics but her condition was worsened 

and reported to our institute in emergency. She 

also gave a past history of lung tuberculosis 2 

years back for which she took complete course. 

Physical examination revealed a temperature 

of 38°C, a pulse rate of 110/minute and a 

blood pressure of 110/70 mm Hg. She was 

pale and toxic. The chest X-ray was clear with 

normal heart sounds. Abdominal examination 

revealed generalized tenderness and swelling in 

bilateral lumber region. The swelling was larger 

approximately 8x10 cm in size on the left side 

compared to the right side. She had physical 

signs of psoas inflammation. Bowel sounds were 

absent. Diagnosis was kept as peritonitis.

On blood tests, the white cell count was 

16.3x109/l, and his urine was clear. The ESR 

was 81 mm/hour. Liver enzymes, serum 

creatinine, blood urea, and nitrogen values 

were normal. Plain X-ray of the abdomen 

showed obliteration of the right psoas shadow. 

Radiography of the lumbar spine and hip was 

normal. Ultrasonography (USG) revealed 

evidence of large abscess seen in left psoas 

muscle ruptured anteriorly in the peritoneal 

cavity and caused intraperitoneal abscess. 

Abscess was also present over right psoas 

muscle but was less as compared to left. Bilateral 

hydronephrosis was present due to psoas abscess. 

Contrast enhanced computed tomography 

(CECT) scan of the abdomen and pelvis showed 

bilateral psoas abscess with huge collection on 

left side of psoas region as dimensions could be 

possible to measure. The collection extends in 

the bilateral retroperitoneal areas of the abdomen 

superiorly from hypochondrium to inferiorly 

137

Rikki Singal                                                                                                   Acta Med Indones-Indones J Intern Med

extending in the pelvic area. There are also 

posteriorly extensions in the posterior abdominal 

wall muscles and paravertebral muscles with 

evidence of air in the collection also. 

The patient was resuscitated and third 

generation cephalosporin antibiotics were 

started. An oblique incision was given on 

bilateral sides. Abscess was drained of 2 liter 

on left side and 1 liter on right sided which was 

foul smelling. Pus was sent for tubercular and 

culture sensitivity tests, which came as negative. 

She went into renal failure in early stage but 

managed with antibiotics and dressings. She was 

discharged in a satisfactory condition after two 

weeks of the treatment.

iliopsoas muscle compartment. Mynter first 

described psoas abscess in 1881 referring as 

psoitis.

4

 A review of worldwide literatures 

published from 1881 through 1990 has revealed 

that the incidence of PPA is around 4 cases per 

year.

5

 PPA is most prevalent in older patients. 

In Taiwan, 2 retrospective reviews were carried 

out, and 20 percent (8 out of 40 patients) were 

classified as having primary abscesses.

6

 A recent 

endemic study in Taiwan reported that the rate 

of occurrence was 2.5 cases annually.

6

The psoas muscle is a fusiform muscle 

which blends with those of the iliacus muscle in 

30% of cases to form the iliopsoas, due to their 

common insertion and actions. The muscle takes 

origin from transverse processes, intertubercular 

processes and intervertebral discs of vertebrae 

T12 to L5 and inserts at the tip and medial part 

of the anterior surface of the lesser trochanter 

of the femur.

PPA can be classified as either primary 

infection of the psoas muscle or secondary 

abscess from the direct extension of infection 

from adjacent organs.

7

 The etiology of psoas 

abscess remains uncertain. It results from either 

hematogenous spread from occult infection 

or local trauma with resultant intramuscular 

hematoma formation which predisposes to 

abscess formation. PPA occur most commonly 

in patients with history of diabetes, injection 

drug use, alcoholism, AIDS, renal failure, 

immunosuppresion or malnutrition. Low 

Figure 1. Bilateral retroperitoneal psoas abscess and huge 

size on left side marked by arrow

Figure 2. Contrast enhanced computed tomography (CECT) 

showing site of rupture on left side marked by dotted arrow

DISCUSSION

PPA is a rare condition with an often vague 

and  non-specific  clinical  presentation,  which 

may be classified as primary or secondary, 

depending on the presence or absence of 

underlying disease. PPA occurs primarily in 

young males; secondary abscesses are observed 

in a somewhat older age group. A psoas (or 

iliopsoas) abscess is a collection of pus in the 

Figure 3. Axial CECT and coronal multiplanar reconstruction 

(MPR) images are showing bilateral psoas abscesses (solid 

arrows) with rupture seen on left side (dotted arrow) with 

formation of large bilateral retroperitoneal collections

138

Vol 45 • Number 2 • April 2013                                          Giant primary psoas abscess: Masquerading peritonitis

socioeconomic status males under 20 years 

of age are more succeptible although psoas 

abscess can occur in any age group. The 

predominant organism in primary psoas abscess is 

Staphylococcus aureus followed by Escherichia 

coli and Streptococcus. Secondary abscess is 

caused by a mixed flora of enteric bacteria, 

commonly E.coli and Bacteroides.

Historically, psoas abscess was most 

commonly seen in patients with spinal 

tuberculosis also known as Pott’s disease. 

Today, it is associated with infections of the 

bowel, kidney and spine. Though in developing 

countries,  Mycobacterium tuberculosis is the 

most frequent cause of secondary abscess. The 

typical triad of fever, flank pain, and limitation 

of hip movement is present only in 30% of cases. 

Other symptoms include malaise, anorexia, 

lower back pain, a palpable mass, or pyrexia of 

unknown origin.

8,9

Laboratory tests such as raised leucocytes 

count and inflammatory markers are useful in 

the evaluation of suspected psoas abscess, but 

none are universal findings. As in most clinical 

scenarios,  diagnosis  is  aided  (confirmed)  by 

appropriate radiological investigations. CT 

scanning has proved superior to ultra sound 

scanning and is considered the radiological 

investigation of choice.

1,10

 USG of the abdomen 

may demonstrate a hypoechoic mass suggestive 

of PA, but cannot identify the cause of the 

abscess. CT scan of the abdomen with contrast 

is the most efficient and accurate imaging study 

in diagnosing a psoas abscess as in our case. 

CT  scanning  is  now  used  as  the  first  line  of 

investigation. CT scan of the abdomen not only 

helps  in  diagnosis,  but  also  in  identification 

of the etiology, for therapeutic purposes, and 

postoperative follow-up.

11

Abscess can be drained radiologically 

or surgically. Percutaneous drainage may be 

difficult in some patients because of the location 

of the abscess, but whenever possible it should 

be employed. Even in patients with complex, 

multiloculated abscesses, percutaneous drainage 

should be attempted and open surgical drainage 

should be reserved if percutaneous drainage 

fails.

4

 We have done extraperitoneal drainage 

which is a safe and effective method for these 

abscesses. We are agreed with the author that 

with open drainage is a better option than 

percutaneous drainage because debridement and 

biopsy of adjacent tissues can be done with open 

process, which may help in shortening recovery 

time.

4

 The prognosis of PPA is better compared to 

secondary abscess.

4

 With appropriate treatment 

the prognosis is generally good. Primary psoas 

abscess has a better prognosis, the mortality rate 

being only 2.4%.

CONCLUSION

Ultrasound, CT, and MRI helped to make a 

definitive diagnosis. Psoas muscle abscess is a 

rare condition with vague clinical presentation, 

which presents a diagnostic challenge requiring a 

high index of suspicion. The role of CT scan was 

very important in this case. If patients are treated 

with USG basis then incision site could have 

been different, thus CT has helped us to remain 

in retroperitoneal space only. The patient was 

treated successfully with open surgical drainage 

and antibiotic therapy.

REFERENCES

1.  Korenkov M, Yucel N, Schierholz JM, Goh P, Troidl 

H. Psoas abscesses. genesis, diagnosis, and therapy. 

Chirurg. 2003;74:677-82.

2.  Alexandru C, Emilia N, Karina B, Doru B. Primary 

psoas abscess. TMJ. 2004;54:374-6.

3.  Hsin-Pei Yin, Yun-An Tsai, Su-Fen Liao, Pei-Hisn Lin, 

Tien-Yow Chuang. The challenge of diagnosing Psoas 

abscess. J Chin Med Assoc. 2004;67:156-9.

4.  Bagul  NB, Abeysekara AMS,  Jacob  S.  Primary 

psoas abscess due to Streptococcus milleri. Ann Clin 

Microbiol Antimicrobials. 2008;7:7.

5.  Gruenwald I, Abrahamson J, Cohen O. Psoas abscess: 

case report and review of the literature. J Urol. 1992; 

147:1623-6.

6.  Huang JJ, Ruaan MK, Lan RR, Wang MC. Acute 

pyogenic iliopsoas abscess in Taiwan: clinical features, 

diagnosis, treatments and outcome. J Infect. 2000; 

40:248-55.

7.  Mallick IH, Thoufeeq MH, Rajendran TP: Iliopsoas 

abscesses. Postgrad Med J. 2004;80:459-62.

8.  R Zissin, E Kots, G Tykochinsky, M Hertz. A psoas 

abscess complicating an infected ureteral stump: CT 

diagnosis. Eur J Radiol. 2003;45:30-2.

9.  Lee YT, Lee CM, Su SC, Liu CP, Wang TE. Psoas 

abscess: a 10 year review. J Microbiol Immunol Infect. 

1999;32:40-6.

139

Rikki Singal                                                                                                   Acta Med Indones-Indones J Intern Med

10.  Cordoba J, Pigrau C, Pahissa A, Almirante B, Gasser 

I, Maartinez -Vazequez JM. Psoas abscess: diagnostic 

and therapeutic usefulness of echography and 

computerized tomography. Med Clin. 1992;99:568-70.

11.  Cantasdemir M, Kara B, Cebi D, Selcuk ND, Numan F. 

Computed tomography-guided percutaneous catheter 

drainage of primary and secondary iliopsoas abscesses. 

Clin Radiol. 2003;58:811-5.

140