Time to play! : the answer
This is the answer to our quiz Time to play! 
The video clip started by the bladder (on the left side of the abdomen as the dog is slightly rotated) that was normal.
Even for an intact male, the prostate is enlarged, highly echogenic, inhomogeneous with numerous variable size cysts. The prostate appears irregular in contour, this is especially obvious on the transverse plane. The urethra is a poorly echogenic structure barely distinguished in the prostate; an indwelling urinary catheter would help in better visualizing the urethra (if an intervention is planned). The appearance of the prostate support benign cystic hyperplasia. A concurrent prostatitis is possible.
When the operator is scanning the right caudal abdomen, a large cavitary structure (resembling the bladder)with a thin wall is seen, it contains echogenic sediment that is gravity dependent.
At the end of the clip, this fluid filled cystic structure appears to originate from the right side of the prostate; this is a paraprostatic cyst.
Initially, the dog has been placed on antibiotics by the referral veterinarian and responded well to the treatment as his clinical signs resolved. What to do next is often multifactorial. Your responses on management varied and are all good suggestions. Our choice was to recommend surgery to neuter the dog and marsupialize the large paraprostatic cyst. The option of performing a fine-needle aspirate of the paraprostatic cyst is reasonable but the wall being thin, there may be a higher chance for leakage. Additionally, the outcome of the FNA would not really affect the need for surgery.
The dog recovered uneventfully after surgery.
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