CONGENITAL ANOMALIES OF UPPER URINARY TRACT INTRODUCTION Abnormalities of kidneys & ureters occur in 3 – 4 % of the new born infants Anomalies occur in number, shape & position Abnormalities can be detected by foetal ultrasound Congenital anomalies occur more frequently in kidney than in any other organ Significant incidence of renal anomalies are associated with congenital anomalies of other organs DEVELOPMENT OF KIDNEYS The urogenital system develops from intermediate mesoderm (extending along the dorsal body wall of the embryo. Urogenital ridge forms on each side of the dorsal Aorta. Nephrogenic cord is the part of urogenital ridge that gives rise to the urinary system. Genital/Gonadal ridge is the part of the urogenital ridge that give rise to genital system. Contd. Urinary system begins to develop before genital system Urinary system consists of: Kidneys Ureters Urinary bladder Urethra Three slightly overlapping kidney systems are formed during intra uterine life, these are : Pronephros Mesonephros metanephros METANEPHROS Permanent kidney develops from 2 sources Metanephric diverticulum or Ureteric bud Metanephric mass of intermediate mesoderm ( metanephrogenic blastema) Ureteric bud is an outgrowth from the mesonephric duct near its entrance into the cloaca METANEPHROS contd. Collecting ducts develop from the ureteric bud Bud penetrates metanephric tissue which is moulded over its distal end as a cup Bud dilates forming primitive renal pelvis Renal pelvis splits into cranial & caudal portions (future major calyces) Each major calyx forms 2 new buds These buds subdivide until 12 or more generations of tubules have formed METANEPHROS contd. At the periphery more tubules form. Tubules of 2nd order enlarge & absorbs the 3rd & 4th generation forming minor calyces Collecting tubules of 5th & successive generations elongate & converge on minor calyx forming renal pyramid In short, ureteric bud forms: Ureter Renal pelvis Major & minor calyces Collecting tubules (1 – 3 million) ASCENT OF KIDNEY Originally a pelvic organ, kidneys later shift to higher position in the abdomen Caused by diminution of body curvature & by growth in lumbar & sacral regions In the pelvis, metanephros receives blood supply from pelvic branch of Aorta At abdominal level it is vascularised by arteries originating from Aorta at higher levels Lower vessels usually degenerate but some may remain. RENAL ANOMALIES Anomalies of Number Anomalies of Ascent Anomalies of Form and Fusion Anomalies of Rotation Anomalies of Renal Vasculature Anomalies of Collecting System Anomalies of structure ANOMALIES OF NUMBER Bilateral renal agenesis Unilateral renal agenesis Supernumerary kidney ANOMALIES OF ASCENT Simple renal ectopia Cephalad renal ectopia Thoracic kidney ANOMALIES OF FORM AND FUSION Crossed renal ectopia with or without fusion Types Crossed renal ectopia with fusion Crossed renal ectopia without fusion Solitary crossed renal ectopia Bilaterally crossed renal ectopia Contd. Forms of Crossed Renal Ectopia Inferior ectopic kidney Sigmoid or S-shaped kidney Lump kidney (Cake kidney) L – shaped kidney Disc kidney Superior ectopic kidney Horseshoe kidney ANOMALIES OF ROTATION Malrotated kidney Ventral position Ventromedial position Dorsal position Lateral position ANOMALIES OF RENAL VASCULATURE Aberrant, accessory or multiple vessels Renal artery aneurysm Renal arteriovenous fistula ANOMALIES OF COLLECTING SYSTEM CALYX & INFUNDIBULUM Calyceal diverticulum Hydrocalycosis Megacalycosis Extrarenal calyces Anomalous calyx Infundibulopelvic dysgenesis PELVIS Pelviureteric junction (PUJ) obstruction Extrarenal pelvis Bifid pelvis ANOMALIES OF STRUCTURE Polycystic kidneys Autosomal recessive (infantile type) Autosomal dominant (adult type) Multicystic dysplastic kidney Simple renal cysts Medullary sponge kidney URETERAL ANOMALIES Anomalies of termination Anomalies of structure Anomalies of number Anomalies of position ANOMALIES OF TERMINATION Ectopic ureter ANOAMLIES OF STRUCTURE Ureteral atresia Ureterocoele Ureteral stenosis and stricture Ureteral valves Ureteral diverticula Megaureter ANOMALIES OF NUMBER Duplication of ureter Incomplete complete ANOMALIES OF POSITION Retrocaval ureter Retroileal ureter SIMPLE RENAL ECTOPIA EMBRYOLOGY The ureter bud grows craniad towards the urogenital ridge The developing metanephric tissue & ureteral bud migrate caphalad, rotating medially on its long axis DESCRIPTION Pelvic kidney Lumbar kidney Abdominal kidney Ureteric orifice usually enters the bladder on the same side with normally situated orifice CROSSED RENAL ECTOPIA WITH OR WITHOUT FUSION Kidney is located on the side opposite from which its ureter inserts into a bladder Unilaterally fused kidney with inferior ectopia is the most common. It’s the superior pole of the ectopic kidney that usually joins with the inferior aspect of the normal kidney Types of Crossed Renal Ectopia Crossed renal ectopia with fusion Crossed renal ectopia without fusion Solitary crossed renal ectopia Bilaterally crossed renal ectopia HORSESHOE KIDNEY Most common of all renal fusion anomalies The joining occurs before the kidney have rotated on their long axis Mostly, the kidneys join at the lower pole by an isthmus The calyces are atypical, pointing posteriorly and axis of each pelvis remains in an oblique lateral plane The ureter inserts high on the renal pelvis and lie laterally 60% of patients with horseshoe kidney remain asymptomatic for an average 10 yrs after discovery PELVIURETERIC JUNCTION (PUJ) OBSTRUCTION Most common cause of hydronephrosis in fetal kidney More common in boys with ratio of 5:2 Typically due to intrinsic narrowing in which the ureteral segment has an interruption in the development of the circular musculature of the PUJ Or, an alteration in the collagen fibers in and around the muscular cells Or, an extrinsic narrowing seen in association with aberrant lower pole renal vessel passing anterior to the PUJ ECTOPIC URETER Any ureter whose orifice terminates anywhere other than the normal trigonal position Generally, ectopic ureteric orifice terminates either in urethra or outside the urinary tract TYPES Lateral ectopia Caudal ectopia Contd. If the ureteric bud arises more proximally on the mesonephric duct than normally, the ureteric orifice has less time in the bladder to undergo its normal migration & results in a orifice more medial and caudal than is usual resulting in Caudal Ectopia If ureteric bud arises more distally, the orifice enters the bladder earlier than usual and migrate laterally and cranially resulting in Lateral Ectopia If ureteric bud arises still more proximally on the mesonephric duct, the ureteric orifice may remain on the mesonephric duct resulting in orifice termination outside the bladder MULTICYSTIC DYSPLASTIC KIDNEY Multicystic kidney of the newborn is usually unilateral, nonhereditary,and characterized by an irregularly lobulated mass of cysts The ureter is usually absent or atretic. It may develop because of faulty union of the nephron and the collecting system. At most, only a few embryonic glomeruli and tubules are observed. The only finding is the discovery of an irregular mass in the flank. DUPLICTION OF URETER Complete or incomplete duplication of the ureter is one of the most common congenital malformations of the urinary tract. Incomplete (Y) type of duplication is caused by branching of the ureteral bud before it reaches the metanephric blastema. In complete duplication of the ureter, the presence of 2 ureteral buds leads to the formation of 2 totally separate ureters and 2 separate renal pelves. Contd. Because the ureter to the upper segment arises from a cephalad position on the mesonephric duct, it remains attached to the mesonephric duct longer and consequently migrates farther, ending medial and inferior to the ureter draining the lower segment (Weigert-Meyer law). Thus, the ureter draining the upper segment may migrate too far caudally and become ectopic and obstructed, whereas the ureter draining the lower segment may end laterally and have a short intravesical tunnel that leads to vesicoureteral reflux URETEROCELE A ureterocele is a sacculation of the terminal portion of the ureter . It may be either intravesical or ectopic; Ectopic ureterocele is located at the bladder neck or in the urethra. Intravesical ureteroceles are associated most often with single ureters, whereas ectopic ureteroceles nearly always involve the upper pole of duplicated ureters. Contd. Ureterocele has been attributed to delayed or incomplete canalization of the ureteral bud leading to an early prenatal obstruction and expansion of the ureteral bud prior to its absorption into the urogenital sinus The cystic dilation forms between the superficial and deep muscle layers of the trigone. There is nearly always significant hydroureteronephrosis, and a dysplastic segment of the upper pole of the kidney may be found in association with a ureterocele.
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