Urinary Tract Infection (UTI): Given the patient's age and symptoms of frequent urination at night (nocturia) accompanied by pain, a UTI is a highly plausible diagnosis. UTIs are common in elderly women and can cause dysuria (painful urination), frequency, and nocturia.

Overactive Bladder: This condition can lead to urinary frequency, urgency, and nocturia. While it might not directly cause pain, the urgency and frequency can be uncomfortable and distressing.
Benign Prostatic Hyperplasia (BPH) in Men is Common, but in Women, a Similar Condition is Pelvic Organ Prolapse: Though less common, pelvic organ prolapse can cause urinary symptoms including frequency and discomfort, which might be perceived as pain.
Diabetes Mellitus: Uncontrolled diabetes can lead to polyuria (excessive urine production) due to high blood sugar levels, resulting in nocturia and potentially pain if there's an associated UTI or neuropathy.

Kidney Stones: Although less common, kidney stones can cause severe pain and urinary frequency. The pain can be intermittent and severe, often radiating from the flank to the groin.
Interstitial Cystitis: A condition causing bladder pressure, bladder pain, and sometimes pelvic pain. The symptoms can worsen as the bladder fills and may improve with urination.
Bladder Cancer: Though less likely, bladder cancer can cause painful urination, frequent urination, and hematuria (blood in the urine). Given the potential severity, it's crucial not to miss this diagnosis.

Tuberculosis of the Urinary Tract: A rare condition in many parts of the world, but it can cause chronic pain, frequency, and other urinary symptoms.
Bladder Fistula: An abnormal connection between the bladder and another organ (like the bowel or vagina) can cause continuous urinary leakage and potentially pain, though this is less common and usually associated with other symptoms like fecaluria or recurrent UTIs.