Psoas abscess is a rare accumulation of pus in the iliopsoas muscle often diagnosed through imaging techniques like CT or MRI. It can be classified into primary abscesses caused by hematogenous spread, and secondary abscesses resulting from direct infection spread from adjacent structures, with common risk factors and varied microbiological causes. Management typically includes antibiotic therapy and drainage, with percutaneous drainage being preferred for initial treatment before considering surgical intervention in complex cases.

1. Psoas Abscess
& Its management
Sushil Gyawali
MS Resident
General surgery

2. Introduction: IPA or PA
● Psoas (or iliopsoas) abscess is a collection of pus in the iliopsoas
muscle compartment
● The incidence is rare, but the frequency of this diagnosis has
increased with the use of computed tomography, prior to which most
cases were diagnosed at postmortem.

3. Anatomy: Psoas muscle
Fusiform shaped muscle, cover anterio-lateral surface of
lumbar vertebral bodies.
ORIGIN- Lateral surface, intervertebral disc and transverse
process of T12 -L5 •
COURSE- passing inferiorly along pelvic brim and iliacus
muscle beneath inguinal ligament towards anterior thigh.
INSERTION- lesser trochanter of femur
Innervation :L1-L3
Primary flexor of the hip joint.

4. Iliopsoas compartment
● The iliopsoas compartment is an
extraperitoneal compartment, contains the
iliacus and the iliopsoas muscle.
● The iliopsoas muscle : rich blood supply from
the lumbar, iliolumbar, obturator, external
iliac, and common femoral arteries.
● predisposes the iliopsoas to heamatogenous
spread of infection

5. Relation to hip joint
• The tendon is separated from the hip capsule by the
iliopsoas bursa (communication joint space in up to 15 %)
which may facilitate spread of infection between these sites.
• Infection readily spreads to the muscle from contiguous
vertebrae.
• The psoas muscle runs under the inguinal ligament and
attaches to the lesser trochanter of the femur - a psoas
abscess often presents as a mass below the inguinal
ligament.

6. Pathogenesis
According to the pathogenesis divided as:
1. Primary abscess —result of hematogenous or lymphatic seeding from a distant
site (which may be occult)
● Risk factors : Diabetes, IVDU, HIV infection, renal failure, and
immunosuppression.
 Trauma and hematoma formation can predispose to development of psoas
abscess.
 Mostly in children and young adults
 More common in tropical and developing countries.
 In Asia and Africa, 99 % are primary; in Europe and North America, 17-61%are
primary .
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7. Pathogenesis…
2. Secondary abscess —occurs as a result of direct spread of infection to the
psoas muscle from an adjacent structure. (contiguous extension)
● It may be uncertain whether involvement of a contiguous structure is a
cause or a consequence of the psoas muscle abscess.
● Risk factors for secondary abscess include trauma and instrumentation
in the inguinal region, lumbar spine, or hip region.
● Adjacent structures —vertebral bodies and discs, the hip joint, the
gastrointestinal tract, the genitourinary tract, vascular structures, etc

9. Secondary…
● Spread of infection from gastrointestinal
disease is the most common source
● Renal disease :second most common
source.
● Extension from the psoas muscle into
the iliacus muscle is a common sequela.
Tubercular-from potts spine
Pyogenic

10. SECONDARY CAUSES OF PSOAS ABSCESS
1 Gastrointestinal Crohn’s disease, diverticulitis, appendicitis,
colorectal cancer
2 Genitourinary Urinary tract infection, Malignancy, ESWL
3 Musculoskeletal spondylitis or spondylodiscitis, Vertebral
osteomyelitis, TB spine, septic arthritis, infectious
sacroiliitis
4 Vascular Infected AAA, femoral vessel catheterisation
5 Miscellaneous Endocarditis, intrauterine contraceptive device,
suppurative lymphadenitis, epidural anesthesia
Shields et al.Iliopsoas abscess – A review and update on the literature, International Journal of Surgery, 2012

11. MICROBIOLOGY
• Varies with geography and pathogenesis of
infection
• Primary psoas abscesses: mostly single organism
 Most common bacterial cause is Staphylococcus
aureus, including MRSA; followed by streptococci
and E coli
 Mycobacterium tuberculosis where TB is common.
 As a complication of Brucella spondylodiscitis, in
endemic area.
• Secondary psoas abscess may be monomicrobial
or polymicrobial; enteric organisms (particularly in
the setting of abscesses with gastrointestinal tract
origin). Anaerobes too
• Klebsiella pneumoniae especially in
patients with diabetes.
• Other: Streptococcus pneumoniae,
Streptobacillus moniliformis,
Staphylococcus lugdunensis,
Actinomyces israelii, and
disseminated nocardiosis.
• Non-typhi Salmonella, Candida
albicans are rare

12. Rodrigues J et al . Clinical presentation, etiology, management, and outcomes of iliopsoas abscess from a
tertiary care center in South India. J Family Med Prim Care. 2017 Oct-Dec

13. Epidemiology
● First described by Mynter in 1881 who referred it as ‘psoitis’
● M>F
● Median age : 44-58 years in developed countries.
● In <20 years in developing countries
● Rt=Lft side; Bilateral psoas abscesses are uncommon.(5%)
● In western data: hematogenous spread from the gastrointestinal tract is
most common
● In Our: Mycobacterium tuberculosis is commonest
● Mortality rate varies from 5% to 11%
D. Shields et al “Iliopsoas abscess—a review and update on the
literature,” International Journal of Surgery, 2012

14. Delay in diagnosis
● Hamano et al. reported that prediagnosis symptom duration of
patients could vary from 1 day to 63 days, and
● Wong et al. reported that it could vary from 1 day to 3 months.
S. Hamano et al , “Pyogenic psoas abscess: difficulty in early diagnosis,” Urologia Internationalis, 2003
O. F. Wong et al , “Retrospective review of clinical presentations, microbiology, and outcomes of patients with psoas
abscess,” Hong Kong Medical Journal, 2013.

15. ● The classical triad of fever, limp, and back pain is present in <30% of patients.
● NON SPECIFIC
● Pain (up to 91% ) with localization to the back, flank, or lower abdomen rarely mimic inguinal
lymphadenopathy or a femoral hernia.
● Abdominal pain radiating to hip, flank
● Fever (75%) , and can manifest as a fever of unknown origin
● Inguinal mass, limp , anorexia, and weight loss
Position of comfort- supine with knee flexed and hip mildly externally rotated.
Psoas abscesses occasionally extend distally and present as a painful or painless mass below the
inguinal ligament.
Symptoms and signs

16. Other symptoms
● Various nerves of lumbar plexus also pass through the psoas muscle and cause muscle
weakness and sensory deficit
● the abscess may drain inferiorly into the upper medial thigh and present as a swelling in
the region.
● The disc is more susceptible to infection, from tuberculosis and Salmonella discitis. The
infection can spread into the psoas muscle sheath.

17. Signs
1. Pain with thigh flexion (esp against resistance)
2. Lower abdominal pain is often exacerbated when psoas muscle is stretched or extended; the
"psoas sign" is pain brought on by extension of the hip.
● Limitation of hip movement is common, prefer to be in a position of less discomfort that
includes supine with hip flexion and lumbar lordosis.
● Unlike septic arthritis, hip pain in patients with psoas abscesses is usually diminished with hip
flexion.
● When painless (ie, a cold abscess), tuberculosis is a more likely cause than another bacterial
infection.

18. Complications
1. Septic shock (up to 20%)
2. DVT due to extrinsic compression of the iliac and
femoral vein
3. Hydronephrosis due to ureteric compression
4. Bowel ileus
5. Hip septic arthritis including prosthetic joint infection
6. Intraperitoneal rupture

19. Diagnosis Of Psoas abscess
• The diagnosis is suspected on clinical grounds and confirmed on imaging
studies.
• Insidious onset and occult characteristics can cause diagnostic delays
• Identification of the etiological organism requires culture of blood or
aspirated pus or, rarely, surgically obtained tissue.

20. Lab tests
• Leukocytosis (>10,000/mL) up to 83%;
• Anemia <11 g/L is frequent (up to 42%)
• Thrombocytosis less frequently (up to 27%)
• An elevated ESR (>50 in 73%)
• CRP :often elevated
• Elevated AST frequently associated with gram-negative rod
etiology.
• Screening for Diabetes, HIV , Renal disorder
• Urine RE, Urine c/s

21. Imaging
● Computed tomography (CT) is the optimal radiographic modality to evaluate for
psoas abscess though sensitivity may be limited early in the course of disease.
 In most cases, an abscess is obvious; other findings may include a focal
hypodense lesion, infiltration of surrounding fat, and gas or an air fluid level
within the muscle.
 Low density mass in retroperitoneum
 Is the modality of choice/ Gold standard

24. MRI
● Magnetic resonance imaging
(MRI) may allow improved definition
of soft tissues and adjacent structures,
especially visualization of the vertebral
bodies.
● Evidence of bony spinal infection :
suspicion for tuberculosis in the
appropriate epidemiologic
circumstances.
● Advantage: better discrimination of soft
tissues and the ability to visualise the
abscess wall and the surrounding
structures without the need of a
intravenous contrast medium

25. A) Axial T2 MRI image showing the psoas muscle (red arrow) and facet joint lesion spreading to
multifidus muscle (blue arrow). (B) Coronal T1 MRI post gadolinium showing extensive psoas
muscle abscess (red arrow).
MR is more sensitive than CT in diagnosis of intra-abdominal abscesses.

26. Imaging….
● Ultrasound has low sensitivity and specificity (operator dependent) ;
 The retroperitoneal space can be difficult to visualize, obscured by bowel
gas, pelvic bone.
 It is diagnostic in only 60% of cases of psoas abscess, compared with 80%
to 100% for CT.
● Abdominal Xray: may suggest loss of psoas muscle definition, abnormal
soft tissue shadows, bulge in psoas shadow and the presence of gas, But a
poor diagnostic tool
● Chest radiograph may demonstrate elevation of the diaphragm or a
pleural effusion.

27. Imaging…
● However, the sensitivity of CT and MRI was less in the early stages, i.e., only
33% and 50%, respectively, and hence CT and MRI can miss psoas abscess in
the early stages (<5 days).
● A recent case study from Japan has shown that 18F-fluorodeoxyglucose positron
emission tomography-CT (PET-CT) can be used in the diagnosis and follow-up of
a patient with tuberculous psoas abscess.
● PET-CT was also used for assessing the therapeutic response to ATT and
resolution of the disease in this case report

28. Culture
● Culture — Both blood cultures and abscess materials:
● Gram stain
● AFB smear and mycobacterial culture :when TB suspected
● These specimens should be obtained when a diagnosis of psoas abscess is
confirmed and before initiation of antimicrobial therapy, if feasible, to
optimize the culture yield.
● Blood cultures are positive in (41 to 68%) : the most frequent S. aureus
● Psoas abscess with or without vertebral osteomyelitis can be a presentation of
endocarditis. Echocardiography to be done.

29. D/D
● Psoas muscle hematoma –in the setting of anticoagulation or a bleeding disorder.
● Retrocecal appendicitis –"psoas sign“
● Iliopsoas bursitis – Iliopsoas bursitis can occur in the setting of rheumatoid arthritis,
trauma, or overuse injuries.
Infection generally occurs as a result of hematogenous or contiguous spread of infection or, in
rare cases, direct inoculation in the setting of corticosteroid injection. In a minority of patients,
the iliopsoas bursa is in direct communication with the hip joint. Deep septic bursitis is
confirmed by bursa aspiration.
● Septic hip arthritis
● Metastatic disease –mimicking a psoas abscess, including a poorly differentiated
carcinoma and a mucinous adenocarcinoma . In both, the diagnosis was confirmed by
tissue biopsy.

30. TREATMENT
● Management of psoas abscess : prompt antibiotic therapy and
drainage.
● Secondary abscess also requires management of the adjacent infected
focus (such as ruptured viscus, fistula, or infected aortic aneurysm).
● Drainage — percutaneous or surgical intervention.

31. Antibiotic therapy
● In general, directed antimicrobial therapy (based on the results of
cultures and smears) is preferable to empiric therapy.
● Should include activity against S. aureus (including MRSA )and enteric
organisms (both aerobic and anaerobic enteric flora): broad spectrum
antibiotics like clindamycin, antistaphylococcal penicillin, and an
aminoglycoside
● Antimicrobial therapy tailored to culture and susceptibility results.
● Evidence of mycobacterial infection should prompt management(ATT)
● Parenteral antibiotics in conjunction with psoas abscess drainage.

32. Antibiotics: duration
● Antibiotics alone are unlikely to be curative, although some success with
antibiotic therapy alone has been reported in a small number of patients
with abscesses <3 cm.
● The optimal duration uncertain; three to six weeks of therapy following
adequate drainage is likely appropriate; the decision on duration of therapy
may be impacted by the presence of osteomyelitis,
● Follow-up imaging should be performed near the end of the planned course
of antimicrobial therapy to ensure satisfactory response to therapy. Most, if
not all, cases of tuberculous psoas abscesses have associated vertebral
osteomyelitis.

33. Percutanous Drainage (PCD)
● Mueller et al reported first application of PCD in iliopsoas abscesses in 1984.
● Percutaneous drainage (by ultrasound or CT guided) is an appropriate initial approach;
(up to 90%)
● PCD is much less invasive and has been proposed as the draining method of choice
● The Percuteanous Catheter may be removed when drainage has ceased, the patient's
condition has improved, and repeat imaging demonstrates that the drainage has been
satisfactory.
● Sometimes PCD can be a useful initial treatment to improve the patient’s condition
before surgery.

34. Surgical drainage
● In setting of percutaneous drainage failure;
● Indications for surgical drainage include multiloculated abscesses and significant involvement of an
adjacent structure requiring surgical management, the presence of an another intra-abdominal pathology
which requires surgery.
● Open Vs laparoscopic
● If there are strong indications for primary operation, such as ruptured infected aortic
aneurysm, ruptured appendicitis, or epidural abscess with spinal cord compression, surgical
intervention should not be delayed. Furthermore, surgical intervention was preferred when
gas-forming IPA was observed because of the higher failure rate of PCD.
Hsieh, MS et al. Features and treatment modality of iliopsoas abscess and its outcome: a 6-year hospital-based study. BMC Infect
Dis 13, 578 (2013)

35. ● Large series , 61 patients
● Patients with bacteremia and small abscesses (<3.5 cm) responded well
to antibiotic treatment alone. However, we did not find any statistical
correlation between abscess size and treatment success.
● As a safe and minimally invasive alternative to open drainage, PCD is
usually considered a first-line treatment option.
● Most patients with an underlying gastrointestinal tract cause such as
Crohn disease ultimately required operative management
● mortality was 5%
Literature:

36. Literature says:
Hsieh, MS et al. Features and treatment modality of
iliopsoas abscess and its outcome: a 6-year hospital-
based study. BMC Infect Dis 13, 578 (2013)
• In the case of primary psoas abscess, PCD
is indicated for a small, and single
abscess if technically possible;
• however, for large, extensive, or
multiple abscesses, percutaneous
drainage may result in recurrence or
simply be insufficient.
• In this situation, open surgical drainage is
more appropriate
Baier Pket al . The iliopsoas abscess: aetiology,
therapy, and outcome. Langenbecks Arch Surg.
2006,
88 pts
klebsiella

37. Surgical …
1. Laparoscopic: Advantage include the extraperitoneal nature of the procedure, the
capability to break down loculations, and rapid postoperative recovery.
2. Open drainage.
● Open surgical drainage may be warranted in the setting of a multiloculated psoas
abscess, an abscess secondary to bowel disease (eg, Crohn's disease) in which
bowel resection may be necessary, or a psoas abscess with a gas-forming organism
● via an extraperitoneal approach was previously the surgical intervention of choice; in
one series, successful outcomes were described in 97 percent of patients

38. Laparoscopic approach

39. Surgical approach: Open
Open Drainage of abscess :
1. Through lateral loin incision- via Petit’s triangle: retroperitoneal
2. Through anterior incision
3. Ludloffs/Medial approach: When abscess points subcutaneously at
adductor region of thigh.
Although open surgery via the extraperitoneal approach combined with drug treatment has
traditionally been the mainstay of therapy, retroperitoneal or laparoscopic drainage has recently
been used

41. Open extraperitoneal drainage
● Through lateral loin incision
Psoas region reached extraperitoneally .Pus drained – drainage tube kept

42. Anterior approach
● 5-7 cm long vertical incision from ASIS to anterior
thigh.
● Identify Sartorius-dissect medially to it upto AIIS.
● Care of femoral nerve
● Insert an artery along medial side of wing of ilium
under poupart’s ligament
● Drain abscess and close

43. Ludolf’s : Medial approach

44. Tropical doctor
Study from
NEPAL
• 72 pts for surgical drainage
• BPKIHS
• Approach: Lower abdominal, extraperitoneal , muscle splitting incision
• Staph aureus: most common
• Mean duration of drainage: 3.2 +/- 1.4 days (range 1-7 days)
• Mean hospital stay: 9 days (range 3-40)
• 2 pt had recurrence, 10 months and 1 year after operation
• 1 had incisional hernia
• Average cost of treatment : Rs 2800 (US $ 40)

45. Outcome
● Has significant morbidity and mortality.
● In one series, mortality due to primary and secondary abscess was 2.4 and 19 %,
respectively; in untreated cases, mortality may approach 100 percent.
● Risk factors for mortality include
delayed or inadequate treatment,
advanced age, the presence of bacteremia,
cardiovascular disease, and infection due to E. coli.
● Mortality is low with early diagnosis and appropriate treatment.
● Relapse can occur up to one year after initial presentation; 15-36% . Recurrence may be
associated with inadequate drainage or inadequate antimicrobial therapy.
● In addition, presence of hip flexion deformity at clinical presentation may not
completely resolve as a result to fibrosis within the iliopsoas sheath.

46. Take home message
● Psoas abscess : Non specific symptoms/features
● Insiduous onset and occult nature – diagnostic delays
● High morbidity
● High index of suspicion required
● CT : choice of image
● Iliopsoas abscess remains a therapeutic challenge
● Timely Drainage: PCS/surgical
● Multidisciplinary

47. References
● Sabistons 2020
● Management of Psoas abscess , Up To Date, 2021
● Iliopsoas abscess – A review and update on the literature, international
Journal of surgery, 2012
● Review on Iliopsoas abscesses, BMJ, 2004