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