Fever and blood in urine can be seen in the following cases: a. Urinary tract infection, caused by gram-negative bacilli, is common in acute pyelonephritis, in addition to fever and blood in urine, patients can also develop urinary symptoms such as frequent urination, urinary urgency, painful urination, accompanied by back pain, chills, nausea, vomiting, generalized weakness, and dizziness and other symptoms of systemic infection. Acute glomerulonephritis is mainly caused by the immune response induced by Streptococcus haemolyticus infection. In addition to fever, hematuria, proteinuria, edema, hypertension, and transient renal insufficiency can also occur. Third, IgA nephropathy, patients usually have asymptomatic hematuria, if combined with infections of other tissues and organs at the same time, they will have fever and hematuria. Fourth, secondary infection of urinary tract stones is due to direct damage to the urethral mucosa by the stones, which leads to hematuria, and most patients have microscopic hematuria.