This document discusses psoas abscess, which is a collection of pus in the iliopsoas compartment. Psoas abscess can be primary (from hematogenous spread) or secondary (from infection of adjacent organs). Common causes of secondary psoas abscess include gastrointestinal, genitourinary, musculoskeletal, and vascular infections. Clinical features can include fever, back pain, limp, and abdominal or groin pain. Diagnosis involves blood tests and imaging like CT or MRI. Treatment requires appropriate antibiotics and drainage of the abscess, either percutaneously or through open drainage.

2. ANATOMY

3.  Extraperitoneal space
 Psoas major and iliacus
 Psoas major – fusiform muscle from
lower border of T12 to upper border or
L5
 Passes along pelvic brim and beneath
inguinal ligament into thigh
 Attached to lesser trochanter of femur
 L2 , L3, L4

5.  Lies in close proximity to organs such as
the sigmoid
colon, appendix, jejunum, ureters, abdomin
al aorta, kidneys, pancreas, spine, and iliac
lymph nodes
 Psoas fascia ( part of iliac fascia) invests
the surface of the muscle
 Attached to vertebral bodies, fibrous
arches and transverse processes and to
iliopubic eminence
 Retains the pus of psoas abscess

6. Psoas abscess
 Iliopsoas abscess is a collection of pus
in the iliopsoas compartment.
 First described by Mynter in 1881 who
referred it as ‘psoitis’
 Classification
 Primary and secondary

8. Aetiology
 Primary psoas abscess :
 Hematogenous spread from an occult
source of infection
 Occurs in patients with
immunocompromised state
 Diabetes mellitus, AIDS, IV drug
abusers, renal failure

9.  Secondary abscess :
 Due to infection from an adjacent organ
 Can be pyogenic or tuberculous
 Tuberculosis of the spine
 Crohn’s disease

10. SECONDARY PSOAS
ABSCESS
 Gastrointestinal - Crohn’s disease, diverticulitis,
appendicitis, colorectal cancer
 Genitourinary - Urinary tract infection, cancer,
extracorporeal shock wave lithotripsy
 Musculoskeletal - Vertebral osteomyelitis,
septic arthritis, infectious sacroiliitis
 Vascular - Infected abdominal aortic
aneurysm, femoral vessel catheterisation
 Miscellaneous - Endocarditis, intrauterine
contraceptive device, suppurative lymphadenitis

11. BACTERIOLOGY
 Related to cause
 Mycobacterium tuberculosis
 Primary (hematogenous) – usually Staphylococcus aureus
 Renal source – usually monomicrobial ; E. coli, Proteus
mirabilis
 Gastrointestinal – polymicrobial; E. coli, Enterobacter spp.,
enterococci and anaerobes such as bactroides;
 Salmonella, Mycobacterium kansasii and Mycobacterium
xenopi are other rare causative organisms

12.  Common in males than females
 Right > left ; bilateral (3%)
 Mortality
 Secondary > primary
 Untreated – 100%

13. CLINICAL FEATURES
 Classical triad ( 30% )
 Fever
 Back pain
 Limp
Variable and non-specific features
 Abdominal or flank pain
 Malaise
 Weight loss
 Nausea
 Referred pain to the groin or knee
 Painless swelling in the inguinal region
 Duration – usually longer than one week

14.  Position of comfort – supine with knee
moderately flexed, hip mildly externally
rotated
 Spine – gibbus, tenderness, paraspinal
spasm
 Clinical tests – non specific
 Place the hand proximal to ipsilateral knee
and ask the patient to lift the leg  pain
 Patient lying on normal side, hyperextension
of affected hip  pain

16. DIFFERENTIAL
DIAGNOSIS
 Femoral hernia
 Enlarged inguinal nodes
 Tumors arising from the pelvis or lumbar
area
 Iliac artery aneurysm

17. Complications
 Intra peritoneal rupture
 Hydroureteronephrosis
 Deep venous thrombosis
 Septicemia

18. Investigations
 CBC - Raised white cell count, Anaemia
 ↑ ESR
 ↑CRP
 Blood culture, urine culture
 Radiography of abdomen, kidney, spine
 X ray abdomen erect – bulge in psoas
shadow
 USG – operator dependant; gas
shadows obscure retoperitoneum

19. Investigations
 CT abdomen – ‘gold standard’; low density
mass in retroperitoneum; info on location
and relation with adjacent organs
 MRI
 IVP
 Mantoux
 Screening for diabetes, HIV, kidney
disorders
 Pus culture and sensitivity
 Pus for AFB and Gram staining

22. Management
 Appropriate antibiotics and adequate
drainage
 Antibiotics :
 Culture specific
 Primary : empirical anti-staphylococcal
 Anti tuberculous drugs
 Drainage :
 Image guided ( CT ) percutaneous drainage
 Open extraperitoneal drainage:
○ Through lateral loin incision
○ Psoas region reached extraperitoneally
○ Pus drained – drainage tube kept

24.  Relatively uncommon condition
 Vague clinical features
 Insiduous onset and occult nature –
diagnostic delays
 High mortality and morbidity
 High index of suspicion required