Extra renal

　　Etiology and pathogenesis of extra renal diseases:

　　Etiology
　　The sequential interaction between the formation of the ureteric bud and the development of the metanephric primordium may lead to polydactyly. The development of the metanephric primordium is essential for the normal development of the kidney, with the other branch extending from the ureteric bud being the first step, then the metanephric horn is divided into two metanephric tails, and finally, they differentiate into two independent ureteric buds.

　　Pathogenesis
　　An accessory kidney is an independent实质性 organ that can be completely separated or loosely attached to the main kidney on the same side, usually located in the normal position of the renal pelvis, close to the caudal side of the main kidney. Occasionally, the accessory kidney can be located on the cranial or posterior side of the main kidney, even in front of major blood vessels, between the two kidneys. The accessory kidney generally has a normal appearance but is smaller than the kidney on the same side. The position of the ureter varies greatly, with about 50% of cases showing the two ureters merging into a single trunk. In the remaining cases, there are completely independent ureters. In rare cases, the accessory kidney has a completely ectopic ureter that opens into the vagina.

　　About 1/3 of cases of accessory kidneys have abnormal development of the kidney and its collecting system, and about half of the cases have thinning of the renal parenchyma and expansion of the collecting system, suggesting the presence of ureteral obstruction, which can lead to hydronephrosis. Due to obstruction at the renal pelvis-ureteral junction, the smooth muscle of the renal pelvis gradually proliferates and strengthens peristalsis, trying to expel urine through the distal obstruction. When the increasing peristaltic force cannot overcome the obstruction, it will lead to atrophy of the renal parenchyma.

　　Although accessory kidneys exist in neonates, they do not produce symptoms and are rarely found in childhood. The average age of diagnosis is 36 years. Abdominal pain, fever, urinary tract infection, and palpable abdominal masses are common complaints. If there is concurrent ectopia of the ureteral orifice of the accessory kidney, there may be urinary incontinence, but it is rare.

　　There are no effective preventive measures for accessory kidneys, and early detection and diagnosis are the key to the prevention and treatment of the disease.

　　The main examinations for accessory kidneys include:
　　Urography, ultrasound, CT, and retrograde pyelography can all show the extent of pathological changes.
　　Radionuclide scanning can understand the functional status of the main kidney and the accessory kidney.
　　Whether cystoscopy can detect one or two ureteral orifices on the affected side depends on whether the ureter of the accessory kidney is independent and the degree of ectopia.

　　The dietary注意事项 for accessory kidneys include:

　　Appropriate Diet
　　Eat light, easy-to-digest foods, fresh vegetables, and fruits. Drink water in moderation.

　　Taboos in Diet
　　Avoid overeating and drinking; avoid seafood, beef, and other irritants; avoid taking tonics, supplements, and easily spicy foods such as chili and chocolate.

　　For asymptomatic patients with an accessory kidney, no treatment is needed. In cases with obstruction or infection, in addition to symptomatic treatment and control of infection, consideration can be given to the removal of the accessory kidney.