Final answer:
The most likely diagnosis is interstitial cystitis, for which a cystoscopy can be ordered to rule out bladder cancer and measure bladder capacity. The first-line medication for relief is pentosan polysulfate sodium (Elmiron).
Step-by-step explanation:
The most likely diagnosis for the patient presenting with pain with bladder filling, relieved by emptying, along with urgency, frequency, dysuria, and nocturia, is cystitis. Cystitis is often caused by a bacterial infection of the bladder. A urinary analysis (UA), cytology, and culture/sensitivity (C/S) tests are negative in this case, which suggests the absence of infection. Hence, the most likely diagnosis is interstitial cystitis, a chronic condition characterized by inflammation of the bladder.
To rule out bladder cancer and measure bladder capacity, a cystoscopy can be ordered. A cystoscopy is a procedure that uses a thin tube with a camera to view the inside of the bladder and urethra. It can help detect any abnormalities or signs of cancer in the bladder.
The first-line medication for relief in interstitial cystitis is pentosan polysulfate sodium (Elmiron). This medication helps reduce bladder inflammation and relieve symptoms. It may take several months for the medication to take effect, and it should be used under the guidance of a healthcare professional.