# Retroperitoneal Abscess and Psoas Abscess > Retroperitoneal and psoas abscess for NEET-PG Surgery: sources, tuberculous cold abscess, psoas sign, imaging, drainage and the reason diagnosis is late. - Canonical URL: https://prepelephant.com/topics/neet-pg/surgery/retroperitoneal-abscess - Exam / course: NEET-PG · Subject: Surgery - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Retroperitoneal Abscess and Psoas Abscess", PrepElephant, https://prepelephant.com/topics/neet-pg/surgery/retroperitoneal-abscess ## Direct answer A retroperitoneal abscess is a collection between the posterior parietal peritoneum and the transversalis fascia that announces itself with weeks of low-grade fever, dull flank or back pain and weight loss rather than an acute peritonitis — the space lacks peritoneal irritation, so diagnosis is late and mortality historically reaches 25-40%. Sources are renal, pancreatic, aortic graft, spinal (Pott's disease) and bowel. The psoas abscess is its classic clinical variant: primary and haematogenous (Staphylococcus aureus) or secondary to tuberculosis of the spine, producing a limp and hip flexion deformity. Treatment is antibiotics plus drainage — percutaneous catheter first, surgery for multiloculated or refractory collections — with antitubercular therapy whenever the pus is tuberculous. ## What you must remember - **Why it presents late:** the retroperitoneum generates no peritoneal signs; malaise, intermittent fever, anorexia and referred hip or knee pain dominate, so patients drift between clinics before imaging. - **Source map:** pyonephrosis and infected renal cysts, infected pancreatic necrosis, aortic graft infection, Pott's spine, diverticular or appendiceal leak, and haematogenous seeding — the source defines both the organisms and the definitive operation. - **Psoas abscess, two types:** primary (S. aureus, haematogenous, common in the young and in tropical settings) versus secondary (spread from lumbar spine tuberculosis — the Indian cold abscess — Crohn's disease or urinary tract). - **Psoas sign:** pain on passive extension of the hip with the patient lying on the opposite side; a flexion deformity or antalgic limp from psoas spasm is the classic bedside clue. - **Grey-Turner sign:** flank ecchymosis is a rare but viva-linked association with retroperitoneal collections and haemorrhage. - **Microbiology discipline:** pus must go for aerobic and anaerobic culture, AFB smear, mycobacterial culture and GeneXpert MTB — empirical antibiotics alone without drainage fail. - **Management ladder:** contrast CT, image-guided aspiration and catheter drainage (8-12 Fr), broad-spectrum antibiotics narrowed to culture, nephrectomy for a destroyed kidney, open drainage for multiloculation or failure; tuberculous cold abscess is drained under antitubercular drug cover. ## A case that explains the delay A 45-year-old farmer reports three weeks of evening fever, night sweats and a 6 kg weight loss; he walks with a limp and holds his right hip flexed. The abdomen is soft — nothing points to it. A chest film is normal, but MRI of the dorsolumbar spine shows a paraspinal collection tracking into the psoas sheath from eroded L1-L2 vertebrae. Ultrasound-guided aspiration yields thick caseous pus: GeneXpert returns Mycobacterium tuberculosis. This sequence — quiet abdomen, limp, spinal erosion, positive GeneXpert — is the standard Indian cold abscess narrative. He receives four-drug antitubercular therapy and the collection is drained through a posterior approach, deliberately avoiding a track that might contaminate the peritoneal cavity. Contrast him with the 30-year-old with a week of fever, no spinal change and staphylococci in blood cultures: a primary psoas abscess needing catheter drainage and antistaphylococcal antibiotics. Same space, same sign, entirely different disease — and the drained pus in both decides everything. ## How the exam frames it Expect the psoas sign question, the primary-versus-secondary psoas abscess comparison, and cold abscess management — drainage under antitubercular cover, never antibiotics alone. The subtle trap is the source: a retroperitoneal abscess in a post-transplant or vascular patient may be graft-related, and simply draining pus without treating the graft or the dead kidney guarantees recurrence. In vivas, quote the absence of peritoneal irritation to explain late presentation, and remember that a tuberculous abscess in the psoas sheath can track down to the thigh below the inguinal ligament — the reason a groin swelling in India sometimes has its origin in the spine. ## Frequently asked questions ### What is the psoas sign? Pain on passive extension of the hip, produced when an inflamed retroperitoneal collection or appendix irritates the psoas muscle beneath. ### Why is retroperitoneal abscess diagnosed late? The space lies outside the peritoneum, so there are no peritoneal signs; fever, weight loss and referred hip pain dominate for weeks. ### How is a tuberculous psoas abscess treated? Antitubercular chemotherapy with image-guided or open drainage under drug cover, addressing the diseased spine as needed. ### Which organism causes primary psoas abscess? Staphylococcus aureus, arriving haematogenously — typical in young patients without any other source. ### When is open surgical drainage preferred? Multiloculated or thick collections, failed catheter drainage, or when the source itself needs surgery — a non-functioning kidney or infected graft.