Urinary Tract Infection (UTI): This is often the most common cause of proteinuria and leukocyturia due to the body's immune response to the infection, leading to the presence of white blood cells (leukocytes) and sometimes protein in the urine.

Kidney Stones: The presence of stones can cause irritation and inflammation, leading to leukocyturia and potentially proteinuria if the stones affect kidney function.
Interstitial Nephritis: This condition involves inflammation of the spaces between the kidney tubules and can be caused by drugs, infections, or other diseases, leading to both leukocytes and protein in the urine.
Prostatitis: In men, inflammation of the prostate gland can lead to leukocyturia and potentially proteinuria, especially if the condition affects the urinary tract.

Pyelonephritis: An infection of the kidney itself, which can present with leukocyturia and proteinuria. Missing this diagnosis could lead to severe kidney damage.
Glomerulonephritis: An inflammation of the glomeruli, the filtering units of the kidneys, which can cause proteinuria and sometimes leukocyturia. It's crucial to diagnose and treat to prevent long-term kidney damage.
Tuberculosis of the Urinary Tract: Although rare, it can cause chronic inflammation leading to leukocyturia and proteinuria. Missing this diagnosis could lead to significant morbidity.

Amyloidosis: A condition characterized by the deposition of amyloid proteins in various tissues, including the kidneys, which can lead to proteinuria.
Lymphoma or Leukemia Involving the Kidneys: Malignant infiltration of the kidneys can cause both leukocyturia and proteinuria due to kidney damage and the presence of malignant cells.
Vasculitis Affecting the Kidneys: Conditions like ANCA-associated vasculitis can cause inflammation of the blood vessels in the kidneys, leading to proteinuria and leukocyturia.