Pyelophlebitis is an inflammatory condition affecting the renal veins, typically resulting from a pelvic infection, such as appendicitis or pelvic inflammatory disease. It is characterized by the presence of thrombosis and inflammation in the renal veins, which can lead to complications like renal vein thrombosis. Symptoms may include abdominal pain, fever, and renal dysfunction. Diagnosis often involves imaging studies and treatment may require antibiotics and supportive care.