Interstitial Cystitis: This condition is characterized by chronic pelvic pain, pressure, or discomfort related to the bladder, often accompanied by at least one other urinary symptom like persistent urge to urinate or frequency, in the absence of a urinary infection or other pathology. The negative bacterial culture, normal cystoscopy, and symptoms of chronic pain limited to the front lower pelvic area, along with gross hematuria, could be indicative of interstitial cystitis, especially considering the patient's postmenopausal status which might affect bladder health.

Overactive Bladder: Although primarily associated with symptoms of urgency, frequency, and nocturia, some patients with overactive bladder may experience pain, especially if there's an associated condition like detrusor overactivity. The absence of infection and normal cystoscopy keep this in the differential.
Pelvic Floor Dysfunction: This encompasses a range of disorders affecting the muscles and tissues that support the pelvic organs. Symptoms can include chronic pain, which might be localized to the front lower pelvic area, and could potentially cause or contribute to urinary symptoms.
Endometriosis: Although less common in postmenopausal women, especially if they have undergone hysterectomy, endometriosis can cause chronic pelvic pain and could potentially lead to hematuria if endometrial implants involve the urinary tract.

Bladder Cancer: Although less likely given the normal cystoscopy, bladder cancer can present with gross hematuria and pelvic pain. It's crucial not to miss this diagnosis due to its significant implications for treatment and prognosis.
Kidney Stones: While the pain from kidney stones typically radiates from the flank to the groin, in some cases, it could be perceived as lower pelvic pain. The absence of infection and normal cystoscopy do not rule out kidney stones, especially if they are causing obstruction or irritation leading to hematuria.
Gynecologic Malignancies: Cancers of the uterus, cervix, or ovaries can cause pelvic pain and, in advanced stages, could lead to hematuria if they invade the urinary tract.

Eosinophilic Cystitis: A rare condition characterized by an eosinophilic infiltration of the bladder wall, which can cause symptoms similar to interstitial cystitis, including pelvic pain and hematuria.
Malacoplakia: A rare inflammatory condition that can affect the bladder and cause symptoms including hematuria and pelvic pain, though it's more commonly associated with immunocompromised states or chronic infection.
Arteriovenous Malformation (AVM) of the Bladder: A rare vascular anomaly that could potentially cause hematuria and pelvic pain due to the abnormal blood flow within the bladder wall.