Differential Diagnosis for Pain on Urination and Increased Frequency

Single Most Likely Diagnosis

• Urinary Tract Infection (UTI): This is the most common cause of painful urination (dysuria) and increased frequency, especially in women. Bacteria such as E. coli are often the culprit, leading to inflammation of the bladder (cystitis) or kidneys (pyelonephritis).

Other Likely Diagnoses

• Sexually Transmitted Infections (STIs): Infections like chlamydia, gonorrhea, and herpes can cause dysuria and frequent urination. These are particularly considered in sexually active individuals.
• Prostatitis: In men, inflammation of the prostate gland can cause pain during urination, frequent urination, and sometimes pain in the pelvic area.
• 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.

Do Not Miss Diagnoses

• Kidney Stones: While not the most common cause, kidney stones can cause severe pain (renal colic) and may lead to frequent urination if they obstruct the flow of urine. Missing this diagnosis can lead to severe complications, including kidney damage.
• Tuberculosis of the Urinary Tract: Though rare in many parts of the world, urinary TB can cause chronic symptoms including frequent and painful urination. It's crucial not to miss this diagnosis due to its potential for severe consequences if left untreated.
• Cancer of the Urinary Tract: Including bladder, kidney, or prostate cancer, which can present with similar symptoms. Early detection is key to effective treatment.

Rare Diagnoses

• Sickle Cell Disease: Can cause urinary tract issues due to sickling in the low oxygen environment of the kidney medulla, leading to ischemia and potentially painful urination.
• Sjögren's Syndrome: An autoimmune disorder that can affect exocrine glands, including those in the urinary system, potentially leading to symptoms of urinary frequency and pain.
• Foreign Body in the Urinary Tract: Though rare, the presence of a foreign object in the urinary tract can cause irritation, pain, and frequent urination. This might be considered in cases where other diagnoses have been ruled out and there's a history suggestive of such an event.