What condition is characterized by posturing and opisthotonus following surgery?

The condition characterized by posturing and opisthotonus following surgery is hypoxic encephalopathy. This condition results from insufficient oxygen supply to the brain, which can occur during surgical procedures, especially if there are complications such as prolonged hypotension or airway obstruction. As a result, the patient may exhibit signs of neurological impairment, including posturing, which is an abnormal body position, and opisthotonus, which refers to a spasm of the muscles causing an arching of the back.

On the other hand, epididymitis, testicular torsion, and hydrocele are primarily related to the urological system and do not typically cause neurological signs like posturing and opisthotonus post-surgery. Epididymitis involves inflammation of the epididymis, testicular torsion is a surgical emergency due to twisting of the spermatic cord, and hydrocele involves fluid accumulation around the testicle, none of which are associated with the specific neurological symptoms described in the question.