Reddish urine and back pain may be caused by acute glomerulonephritis, pyelonephritis, urinary stones, pyelonephritis and so on. 1. Acute glomerulonephritis: the infection of streptococcus and other pathogenic microorganisms causes immune reaction, and the immune complexes formed are deposited locally in the glomerulus, leading to renal function damage, symptoms such as hematuria, edema, proteinuria, etc. A few of them may have symptoms of low back pain. 2. Pyelonephritis: most of them are caused by retrograde bacterial infection through the urethra, and will have systemic symptoms of infectious diseases such as fever, chills, fatigue, etc. In addition, there are symptoms such as frequent urination, urgency, pain in urination, lumbago, hematuria, and so on. 3. Urinary tract stones: in the case of kidney stones, ureteral stones, etc., the friction of the stones stimulates the local mucous membrane, resulting in tiny breakage of the mucous membrane and the symptoms mentioned above. 4. Renal pelvis kidney cancer: local invasion after malignant lesion in renal pelvis, rupture of tumor in middle or late stage, causing blood in urine, and the enlarged tumor stimulates the nerves of renal peritoneum and causes lumbago. Reddish urine and back pain may be related to many factors, so it is recommended to consult doctor for clear diagnosis.