Differential Diagnosis for a 70-year-old Female with Suspected UTI and Decreased Kidney Function

Single Most Likely Diagnosis

• Urinary Tract Infection (UTI) with Pyelonephritis: This is the most likely diagnosis given the symptoms of UTI and decreased kidney function. Pyelonephritis, an infection of the kidney, can cause a decline in renal function, especially in elderly patients.

Other Likely Diagnoses

• Chronic Kidney Disease (CKD) with UTI: CKD can predispose to UTIs due to urinary stasis and decreased immune function. The UTI could be exacerbating the underlying CKD, leading to a decline in kidney function.
• Acute Interstitial Nephritis (AIN): AIN can be caused by medications, infections, or other factors and can present with decreased kidney function. In the context of a UTI, AIN could be a consideration, especially if the patient is taking certain medications like NSAIDs or antibiotics.
• Obstructive Uropathy: Obstruction in the urinary tract, such as from kidney stones or tumors, can cause decreased kidney function and increase the risk of UTIs.

Do Not Miss Diagnoses

• Sepsis: Sepsis from a UTI source is a life-threatening condition that requires immediate recognition and treatment. Elderly patients may not always present with typical symptoms of sepsis, making it a critical diagnosis not to miss.
• Emphysematous Pyelonephritis: This is a severe infection of the kidney characterized by gas formation in the renal parenchyma. It is more common in diabetic patients but can occur in anyone with a UTI and requires prompt diagnosis and treatment.
• Papillary Necrosis: This condition involves necrosis of the renal papillae and can be caused by analgesic abuse, diabetes, or severe pyelonephritis. It can lead to significant kidney damage if not recognized and treated.

Rare Diagnoses

• Xanthogranulomatous Pyelonephritis (XGP): A rare form of chronic pyelonephritis characterized by the destruction of renal tissue and the presence of xanthoma cells. It typically presents in patients with long-standing urinary tract obstruction and infection.
• Malakoplakia: A rare inflammatory condition that can affect the urinary tract and is associated with chronic infection, typically E. coli. It can cause obstructive symptoms and decreased kidney function.
• Tubulointerstitial Nephritis and Uveitis (TINU) Syndrome: A rare condition characterized by the combination of tubulointerstitial nephritis and uveitis. While not directly related to UTIs, it can cause decreased kidney function and should be considered in patients with unexplained renal dysfunction and eye symptoms.