This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
This elderly male came with a history of recurrent attacks of pain and swelling in the great toe in the past. This is the present x-ray of the hands. The diagnosis can be confirmed by 
Select and explain. 
A. Anti CCP antibodies, B. Polarised microscopy of tissue fluid aspirate, C. Xray of lumbosacral spine, D. HLA B27
B: Polarised microscopy of tissue fluid aspirate
Answer: B: Polarised microscopy of tissue fluid aspirate 
Explanation: Radiological features in GoutSoft tissue findingsCalcific deposits in gouty tophi in 50% (only calcium urate crystals are opaque)Eccentric juxta-aicular lobulated soft-tissue masses (hand, foot, ankle, elbow, knee)Bilateral olecranon bursitisAural calcificationJoint findingsPreservation of joint space initiallyAbsence of periaicular demineralizationErosion of joint margins with sclerosisCailage destruction late in course of diseasePeriaicular swelling (in acute monaicular gout)Chondrocalcinosis (menisci, aicular cailage of knee) resulting in secondary osteoahritisBone findings"Punched-out" lytic bone lesion +- sclerosis of margin"Mouse / rat bite" from erosion of long-standing soft-tissue tophus"Overhanging margin" (40%)Ischemic necrosis of femoral/humeral headsBone infarctionDiagnosis of gout relies on the identification of MSU crystals under a compensated polarized light microscope (CPLM) in synol fluid aspirated from the patient's joint.