Congenital Anomalies of Kidney & Ureter Dr. Muhammad Rafique Anatomy, DIMC Objectives Know the prevalence of congenital anomalies of Kidney & Ureter Discuss the congenital anomalies of Kidney Describe the congenital anomalies of the Renal Vessels Mention the congenital anomalies of Ureter Congenital Anomalies of Kidney Congenital Anomalies of Kidneys & Ureters Some type of abnormality of the kidneys and ureters occurs in 3% to 4% of newborn infants. Anomalies in shape and position are most common. Many fetal urinary tract abnormalities can be detected before birth by ultrasonography. Unilateral Renal Agenesis Unilateral renal agenesis occurs approximately 1in 1000 newborn infants. Males are affected more often than females, and the left kidney is usually the one that is absent. Unilateral Renal Agenesis Unilateral renal agenesis often causes no symptoms and is usually not discovered during infancy because the other kidney usually undergoes compensatory hypertrophy and performs the function of the missing kidney. Unilateral renal agenesis should be suspected in infants with a single umbilical artery Bilateral Renal Agenesis Bilateral renal agenesis is associated with oligohydramnios (small amount of amniotic fluid) because little or no urine is excreted into the amniotic cavity. This condition occurs approximately 1 in 3000 births, and is incompatible with postnatal life because of the associated pulmonary hypoplasia. Bilateral Renal Agenesis These infants have a characteristic facial appearance: the eyes are widely separated and have epicanthic folds, the ears are low-set, the nose is broad and flat, the chin is receding, and there are limb defects. Most infants with bilateral renal agenesis die shortly after birth or during the first months of life. Intravenous Pyelography Etiology of Renal Agenesis Renal agenesis results when the metanephric diverticula fail to develop or the primordia of the ureters degenerate. Failure of the metanephric diverticula to penetrate the metanephrogenic blastema results in failure of kidney development because no nephrons are induced by the collecting tubules to develop from the metanephrogenic blastema. Etiology of Renal Agenesis Renal agenesis probably has a multifactor etiology. There is clinical evidence that complete in utero involution of polycystic kidneys could lead to renal agenesis with a blind ending ureter on the same side. Malrotated Kidney If a kidney fails to rotate, the hilum faces anteriorly, that is, the fetal kidney retains its embryonic position. If the hilum faces posteriorly, rotation of the kidney proceeded too far; if it faces laterally, lateral instead of medial rotation occurred. Abnormal rotation of the kidneys is often associated with ectopic kidneys. Ectopic Kidneys One or both kidneys may be in an abnormal position. Most ectopic kidneys are located in the pelvis but some lie in the inferior part of the abdomen. Pelvic kidneys and other forms of ectopia result from failure of the kidneys to alter position during embryo growth. Pelvic kidneys Pelvic kidneys are close to each other and may fuse to form a discoid ("pancake") kidney. Ectopic kidneys receive their blood supply from blood vessels near them (internal or external iliac arteries and/or aorta). They are often supplied by multiple vessels. Sometimes a kidney crosses to the other side resulting in crossed renal ectopia showing both kidneys on the right side of the abdomen). Pelvic kidneys Sometimes a kidney crosses to the other side, resulting in crossed renal ectopia with or without fusion. An unusual type of abnormal kidney is unilateral fused kidney. In such cases, the developing kidneys fuse while they are in the pelvis, and one kidney attains its normal position, carrying the other kidney with it. Horseshoe Kidney In 0.2% of the population, the poles of the kidneys are fused; usually the inferior poles fuse. The large U- shaped kidney usually lies in the hypogastrium, anterior to the lower lumbar vertebrae. Normal ascent of these fused kidneys is prevented because they are caught by the root of the inferior mesenteric artery. Horseshoe Kidney A horseshoe kidney usually produces no symptoms because its collecting system develops normally and the ureters enter the bladder. If urinary flow is impeded, signs and symptoms of obstruction and/or infection may appear. Approximately 7% of persons with Turner's syndrome have horseshoe kidneys. Cystic Kidney Diseases In autosomal recessive polycystic kidney disease, diagnosed at birth or in utero by ultrasonography, both kidneys contain many hundreds of small cysts, which result in renal insufficiency. Death of the infant usually occurs shortly after birth; however, an increasing number of these infants are surviving because of postnatal dialysis and kidney transplantation. Multicystic Dysplastic Kidney Disease Multicystic dysplastic kidney disease results from dysmorphology during development of the renal system. The outcome for children with multicystic dysplastic kidney disease is generally good because the disease is unilateral in 75% of the cases. In multicystic dysplastic kidney disease, fewer cysts are seen than in autosomal recessive polycystic kidney disease and they range in size from a few millimeters to many centimeters in the same kidney. Multicystic Dysplastic Kidney Disease For many years it was thought that the cysts were the result of failure of the metanephric diverticulum derivatives to join the tubules derived from the metanephrogenic blastema. It is now believed that the cystic structures are wide dilations of parts of the otherwise continuous nephrons, particularly the nephron loops (loops of Henle). Multicystic Dysplastic In the multicystic dysplastic kidney the numerous ducts are surrounded by undifferentiated cells. Nephrons fail to develop and the ureteric bud fails to branch, so that the collecting ducts never form. In some cases, these defects cause involution of the kidneys and renal agenesis. Renal Tumors Wilms’ tumor is a cancer of the kidneys that usually affects children by 5 years of age but may also occur in the fetus. Wilms’ tumor is due to mutations in the WT1 gene on 11p13, and it may be associated with other abnormalities and syndromes. For example, WAGR syndrome is characterized by aniridia, hemihypertrophy, and Wilms’ tumor. Similarly, Denys-Drash syndrome consists of renal failure, pseudohermaphrodism, and Wilms’ tumor. Accessory Renal Arteries The common variations in the blood supply to the kidneys reflect the manner in which the blood supply continually changed during embryonic and early fetal life. Approximately 25% of adult kidneys have two to four renal arteries. Accessory (supernumerary) renal arteries usually arise from the aorta superior or inferior to the main renal artery and follow the main renal artery to the hilum of the kidney. Accessory Renal Arteries Accessory renal arteries may also enter the kidneys directly, usually into the superior or inferior poles. An accessory artery to the inferior pole (polar renal artery) may cross anterior to the ureter and obstruct it, causing hydronephrosis- distention of the renal pelvis and calices with urine. If the artery enters the inferior pole of the right kidney, it usually crosses anterior to the inferior vena cava and ureter. Accessory Renal Arteries It is important to be aware that accessory renal arteries are end arteries; consequently, if an accessory artery is damaged or ligated, the part of the kidney supplied by it will become ischemic. Accessory arteries are approximately twice as common as accessory veins. Congenital Anomalies of ureter Duplications of the Urinary Tract Duplications of the abdominal part of the ureter and the renal pelvis are common. These anomalies result from division of the metanephric diverticulum. The extent of the duplication depends on how complete the division of the diverticulum was. Duplications of the Urinary Tract Incomplete division of the metanephric diverticulum results in a divided kidney with a bifid ureter. Complete division results in a double kidney with a bifid ureter or separate ureters. A supernumerary kidney with its own ureter, which is rare, probably results from the formation of two metanephric diverticula. Ectopic Ureter An ectopic ureter does not enter the urinary bladder. In males, ectopic ureters usually open into the neck of the bladder or into the prostatic part of the urethra, but they may enter the ductus deferens, prostatic utricle, or seminal gland. In females, ectopic ureters may open into the bladder neck, urethra, vagina, or vestibule of the vagina. Ectopic Ureter Incontinence is the common complaint resulting from an ectopic ureter because the urine flowing from the orifice does not enter the bladder; instead it continually dribbles from the urethra in males and the urethra and/or vagina in females. Megaureter Megaureter means abnormally dilated ureter This may be congenital or acquired May be primary due to disease of renal system or secondary to obstruction produce by other organs or vessels near to renal system Usually caused by absence peristaltic movement in smooth muscle of ureter Ectopic Ureter An ectopic ureter results when the ureter is not incorporated into the trigone in the posterior part of the urinary bladder. Instead it is carried caudally with the mesonephric duct and is incorporated into the middle pelvic portion of the vesical part of the urogenital sinus. Ectopic Ureter Because this part of the sinus becomes the prostatic urethra in males and the urethra in females, the location of ectopic ureteric orifices is understandable. When two ureters form on one side, they usually open into the urinary bladder.
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