Urinary Tract Infection (UTI) with Obstruction: This is the most likely diagnosis because kidney stones can cause obstruction in the urinary tract, leading to infection, which presents with fever. The combination of fever and kidney stone is a classic presentation for an infected obstructing stone.

Pyelonephritis: An infection of the kidney, which can be caused by an ascending UTI, especially in the presence of a kidney stone that obstructs the flow of urine, leading to fever and potentially severe illness.
Sepsis due to UTI: While not the initial diagnosis, if a UTI or pyelonephritis is not promptly treated, it can lead to sepsis, a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs.

Xanthogranulomatous Pyelonephritis: A rare form of chronic pyelonephritis that can mimic other conditions, including cancer. It's crucial to consider this diagnosis in patients with long-standing urinary tract obstruction and infection.
Emphysematous Pyelonephritis: A severe, life-threatening infection of the kidney characterized by gas formation, typically seen in diabetic patients. It requires immediate medical attention.
Urosepsis: A condition where a UTI leads to a systemic infection, potentially causing organ failure. It's critical to identify and treat promptly to prevent high mortality rates.

Malacoplakia: A rare inflammatory condition that can affect the urinary tract, among other areas, and is associated with chronic infection and the formation of distinctive plaques.
Tuberculosis of the Urinary Tract: Although rare in many parts of the world, urinary tract tuberculosis can cause chronic infection, obstruction, and potentially mimic other conditions, including kidney stones and UTIs.