GUT 00
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The document summarizes the development of the urinary tract in the fetus. It discusses the three sets of excretory organs during intrauterine life - the pronephros, mesonephros, and metanephros. It describes the normal development and regression of each. It also discusses abnormalities that can occur in renal number, location, size, urinary tract dilatation, and various genetic and non-genetic diseases that affect the urinary tract development.
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GUT 00
- 1. CIELO B. FLORES-DE GUZMAN, MD
- 2. 3 sets of excretory organs during intrauterine life: 1. Pronephros 2. Mesonephros 3. Metanephros
- 3. Pronephros - Seen in the 3rd week of development - Completely degenerates by the start of the 5th week
- 4. I Mesonephros - Eventually regresses during the 4th month - Serves as the excretory organ of the embryo while the definitive kidney begins its development - Certain elements are retained as part of the reproductive tract
- 5. Metanephros - Definitive kidney - Appears in the 5th week - Its excretory units develop from the metanephric messoderm
- 6. Collecting Duct - Formed from the ureteric bud - Gives rise to the: - Ureteter - Renal pelvis - Major and minor calyces - Collecting tubules
- 8. Nephron - A.k.a. excretory units - formed by the proximal tubules, glomeruli, Loop of henle and distal tubules
- 12. The Normal Urinary Tract
- 13. Bladder
- 14. Bladder
- 15. Kidneys - TVS: 11 weeks AOG - TAB: 12 weeks AOG - 1st Trimester: appear as hyperechoic oval structure at both sides of the spine - 3rd Trimester: decreased hyperechogenecity Corticomedullary Differentation (CMD): - start to appear at approximately 14-15 weeeks
- 16. The Abnormal Urinary Tract
- 17. Abnormal Renal Number Bilateral Renal Agenesis - a. k. a Potter’s Syndrome - Incompatible with extrauterine life - Results in pulmonary hypoplasia and musculoskeletal abnormalities - Diagnosis: - Anhydramnios after 15 weeks - non visualization of normal renal structures - Empty bladder
- 18. Abnormal Renal Number Unilateral Renal Agenesis - Incidence: 1/500 pregnancies) - compatible with extrauterine life - “lying down adrenal sign” on ipsilateral side of the missing Kidney
- 19. Renal Duplication - Benign - Normal variant - Differential diagnosis for Urinary Tract Dilatation - Length of the Kidney >95th percentile - Cystic like structure surrounded by a rim of renal parenchyma in the upper lobe of the kidney - Kidney with 2 separate non communicating renal pelvises - Dilated ureters usually draining the upper pole The fetus.net. Sonoworld.com. Duplex Kidney. 3-17-2011
- 20. Abnormal Kidney Location - Kidney located outside the renal fossa and within the pelvis - Due to failed migration of the ureteral bud and developing metanephric blastema to the renal fossa - Incidence 1:900 - Known abnormal positions: - Iliac - Abdominal - Pelvic - Thoracic - crossed
- 21. Abnormal Kidney Location - Other locations: 1. Horseshoe kidney 2. Cross fused ectopia
- 22. Abnormal Kidney Size Small Kidneys - below -2 SD - may result from maldevelopment, obstruction or when an ischemic phenomenon is present - Prognosis depends on the remaining renal function Enlarged Kidneys - Above +2 SD - Differential diagnosis: renal dilatation, cystic kidneys, organomegaly, renal tumor
- 23. Urinary Tract Dilatation - Best criterion: measurement of the anteroposterior diameter of the pelvis in a transverse scan Normal Values: - < 4 mm 2nd trimester - < 7mm 3rd trimester
- 24. Urinary Tract Dilatation Pyelectasis 7 mm – Mild Dilatation 7-15 mm – Mod Dilatation >15 mm – Marked Dilatation - May be affected by maternal hydration - May signify as a soft marker for chrosomal anomaly - The more dilated, the more likely that there is a decrease in renal function - Monitoring: one sonographic examination each trimester for confirmation
- 25. Ureteropelvic Junction Obstruction - hallmark: dilated renal pelvis and calyces without dilatation of the ureters - More common in male fetuses - Differential diagnosis: - Reflux - Transient dilatation - Multicystic dysplastic kidney - Ureterovesical junction obstruction
- 26. The Abnormal Urinary Tract - When detected, complete anatomical scan should be done to look for: Associated anomalies Polymalformative syndromes WORSENS PROGNOSIS
- 27. The Abnormal Urinary Tract - When detected, complete anatomical scan should be done to look for: Associated anomalies Polymalformative syndromes WORSENS PROGNOSIS
- 28. Diseases with Known Genetic Transmission
- 29. AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE (ARPKD) - Most frequently caused by a mutation in PHKD-1 gene - Marked elongation of the tubules that expand into multiple small cysts - Cystic dilatation of the tubules, predominantly in the medulla with cortical sparing - Incidence is 1:20,000 - With associated biliary dysgenesis and hepatic fibrosis - Differential Diagnosis: Glomerulocystic disease Bardet-Biedl Syndrome (BBS)
- 30. AUTOSOMAL RECESSIVE POLYCYSTIC KIDNEY DISEASE (ARPKD) - Sonologic Features: Markedly enlarged hyperechoic kidneys No CMD Hypoechoic outer cortical rim Cysts may become apparent in the 3rd TM but is not specific Oligohydramnios due to renal failure
- 31. AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD) - Incidence 1:800 livebirths - Inherited condition - Autosomal dominant w/ 100% penetrance - 3 gene mutations: PKD1, PKD2, PKD3 - Cyst formation both in cortex and medulla - Rarely seen in utero
- 32. AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD) - Sonologic Features: Moderately enlarged (+4-+8 SD) Diffusely hyperechoic kidneys Hyperechoic cortex, hypoechoic medulla Normal Amniotic fluid Volume
- 33. AUTOSOMAL DOMINANT POLYCYSTIC KIDNEY DISEASE (ADPKD)
- 34. Autosomal Dominant Polycystic Kidney Disease (ADPKD) Autosomal Recessive Polycystic Kidney Disease (ARPKD) 3 gene mutations: PKD1, PKD2, PKD3 Mutation in PKHD1 gene Incidence: 1:800 live births 1: 20,000 live births Cystic dilatation in cortex and medulla Cystic dilatation predominate in the medulla (cortical sparing) Moderately enlarged kidneys (1-2SD above the mean) Markedly enlarged kidneys (+4-+15SD above the mean) Hyperechoic cortex Hypoechoic outer cortical rim Hypoechoic medulla Hyperechoic medulla
- 36. Multicystic Dysplastic Kidney (MCD) - Most common among the non hereditary group - normal renal parenchyma replaced by multiple, Non communicating cysts of varying sizes - Renal outline becomes irregular - Cysts may decrease in utero or may resolve spontaneously - Good prognosis: unilateral involvement - Poor Prognosis: Bilateral Severe oligohydramnios
- 37. Obstructive Dysplasia - Dilatation of the upper and lower Urinary tract associated w/ hyperechogenecity of the renal parenchyma - Cysts in variable sizes form in the renal cortex - Impaired renal
- 38. Simple Renal Cyst - Uncommon in the fetus - Usually solitary and localized in the upper pole of a normal kidney - Good prognosis
- 39. Renal Tumors Mesoblastic Nephroma Wilms Tumor Nephroblastomatosis - Most sommon renal tumor in the fetus - Less common - Less common - Solid or partially cystic - Solid or partially cystic - Solid partially cystic - Commonly associated with oligohydramnios - Good prognosis - Bilateral involvement
- 41. - Identical in both sexes until 11 weeks of gestation - Rapid growth of penis occurs after 14 weeks AOG - Penis points upward while clitoris points downward Baby Boy Baby Girl
- 42. Male Fetus genital tubercle elongates, to form the penis urogenital folds fuse together enclosing to become the spongy urethra.
- 43. Female Fetus Phallus continues to grow to become the clitoris Urogenital folds fuse only at the most posterior Aspect To form the labia minora and labia majora And the fourchette
- 44. Ambiguous Genitalia - Difficulty to assign the fetal gender during UTZ examination in 2nd or 3rd trimester - May be isolated or part of various syndromes - Detailed sonogram should be done - Chromosomal analysis should be obtained - May be associated or may serve as a clue for the diagnosis of Adrenogenital syndrome (AGS)
- 46. Hypospadias/Epispadias - More common malformation - Penis appears shorter and broadened - Urethral meatus abnormally positioned (proximally and ventrally) to its normal position Sonographic Findings: - anomalous distal morphology of the penis - Small penis - Ventral incurving (chordee) - Anomalous urinary stream
- 48. Ovarian Cysts - Commonest cause of cystic mass in the female fetus - Results from maternofetal hormonal influence - May be small or large (>8cm) - May be unilateral or bilateral - Usually completely cystic
- 49. Hydrocolpos
- 50. THANK YOU FOR LISTENING!!!
Editor's Notes
- Functionally the urogenital system can be divided into 2 entirely different components: urinary system and genital system Embryologically, both develop from a common mesodermal ridge, Renal development passes through three stages: the pro- and mesonephros (both transitory), and the metanephros, which develops into the definitive kidney.
- The most basic of the 3 excretory organs, its composed of excretory units called nephrotomes that eventually regress before more caudal ones are formed.
- Greek: middle kidney Functions on the 6th week to the 10th fetal life It atrophies and for the most part disappears rapidly as the permanent kidney (metanephros) develops beginning during the sixth or seventh week, so that by the beginning of the fifth month only the ducts and a few of the tubules of the mesonephros remain.
- The embryonic precursor of the adult kidney. (click) It develops caudal to the mesonephros while the mesonephros regresses.
- The development of the duct system differ from that of the other kidney systems… Collecting duct, develops from the ureteric bud as an outgrowth of the mesonephric duct close to its entrance to the cloaca, (click) The bud penetrates the metanephric tissue (which is molded as a cap at its distal end, and will subsequently dilate forming the primitive renal pelvis at the end of the 6th week (click)
- That will split into cranial and caudal portions to form the future major calyces (at the end of the 6th week) Each calyx will will form new buds until new generation of collecting tubules are formed (7th week) The tubules continue to form until the end of the the fifth month wherein the latter tubules enlarge and are absorbed forming the minor calyces The collecting tubules merge into the minor calyces forming the (click) renal pyramid
- During 4th to 7th week of fetal development, (click) the cloacal membrane is divided by the urorectal septum into cranial and caudal portion
- Anterior portion forms the (click) Urogenital sinus (click) posterior portion forms the (click) the rectum
- The urogenital sinus forms the urinary bladder (click) the urethra (click) the lower vagina and vaginal vestibule (click) in female embryo or the phallic urethra in male embryos
- Urine first produced 9th week of fetal life. Urine in the bladder visualized as fluid filled structure within the fetal pelvis. 2nd & 3rd TM: bladder empties and refills every 25-30 mins
- Position of the fetal bladder visually identified because it lies between the Umbilical arteries which is readily seen by Color doppler imaging.
- With the use of transvaginal probe, fetal kidneys can be seen at 11 weeks, by transabdominal probes, at 12 weeks fetal life. (click) During the first trimester, the fetal kidneys are seen as hyperechogenic structures situated below, but on the sides of the fetal spine. (click) This hyperechogenicity can be described comparing that to the adjacent liver and spleen echogenecity. This echogenicity decreases by the third TM. (click) CMD starts to be apparent by 14-15 weeks of gestation, (click) however becomes more pronounced by the 3rd TM.
- Lethal condition with an incidence of 1/4,000 pregnancies (Potter, 1965). Ultrasound features are early anhydramnios from 16 weeks of gestation onwards, absence of bladder filling therefore an empty baldder Renal artery color Doppler and Magnetic Resonance Imaging (MRI) may be helpful in confirming the diagnosis. Confirmation of absent Kidneys: Fetal MRI
- Rare Compatible with extrauterine life when no other assoc. complications seen The adrenals on the side where the kidneys are missing becomes elongated (click) hence the lying down adrenal sign
- Benign…. Etc (click) Length of the kidney in the sagittal view > 95° percentile (see the table below) Cystic-like structure surrounded by a rim of renal parenchyma in the upper pole of the kidney (second pelvis) Kidney with two separate non communicating renal pelvises Dilated ureter usually draining the upper pole. Normally, the fetal ureters are too narrow to image (1-2 mm) and they are considered dilated if their diameter is ≥3 mm. Echogenic cystic structure in the bladder (ureterocele)
- AKA ectopic kidney Easily recognizeable especially in the third trimester due to its CMD
- Horsesoe kidney (click) this is rarely diagnosed in utero. Continous parenchyma across the midline, (the fused isthmus) is its conclusive finding (click) Cross fused ectopia, wherein both kidneys lie on the same side. It has a somewhat male predilection, and incidence is unknown due to it being asymptomatic and is usually an incidental finding
- The kidneys must be systematically measured whenever their echogenecity is abnormal or whenever the amniotic fluid volume is reduced. Kidney measurements should be compared to an established nomogram. Cases with oligohydramnios has the poorest prognosis Enlarged kidney: Organomegaly (i.e. Beckwith wiedemann syndromes The kidneys must be measured in a sagittal or coronal plane. Measured from the anterior pole to the posterior pole to get the renal length Kidney length is measured at a sagittal plane, with full length and renal pelvis visible.
- through a transverse slice of the fetal abdomen, a hypoechoic image can be indentified on each side of the spine, corresponding to the kidneys. The renal pelvis appears as an anechoic image on the medial edge of the kidneys. The image obtained is then frozen, and the greatest anterior-posterior distance, parallel to the spine, is measured, as shown in the image and in the schematic drawing. There is a positive correlation between gestational age and renal pelvic anteroposterior diameter.
- Mild pyelectasis is a common finding which is often incidental, with no significant long term sequelae. However, there is a small association with aneuploidy, in particular the trisomy 21 and postnatal renal pathology.
- Ultrasound image at 33 weeks’ gestation demonstrating the most common sonographic appearance of autosomal dominant polycystic kidney disease. The fetal kidney is enlarged (+ 3 SD) and presents a hyperechoic cortex relative to the liver (L). The corticomedullary differentiation is increased.
- Ultrasound image of a fetus with autosomal dominant polycystic kidney disease showing visible cysts in utero (32 weeks). The kidney (between calipers) is enlarged (+ 2.5 SD) and cortical cysts are visible (arrowheads).
- Most common among …. developmental disorder of the kidney, (click) in which the normal renal parenchyma is replaced by multiple, non- communicating cysts of varying size. The renal outline is difficult to delineate and can be irregular No nomal CMD No identifiable collecting system
- lower or upper urinary tract obstruction in asso- ciation with a hyperechoic appearance of the renal cortex and eventually the presence of cysts variable in size
- Simple renal cysts are rather uncommon in the fetus. They are usually solitary and localized in the upper pole of a normal kidney. There is no associa- tion with other malformations and the prognosis is good. A follow up ultrasound is usually recom- mended to exclude a more diffuse distribution or other cystic renal diseases.
- Simple renal cysts are rather uncommon in the fetus. They are usually solitary and localized in the upper pole of a normal kidney. There is no association with other malformations and the prognosis is good. A follow up ultrasound is usually recom- mended to exclude a more diffuse distribution or other cystic renal diseases.
- At the sixth week the site of the genitals is a small bud, called the genital tuber. Until the ninth week to 11th weeks of development, the embryonic reproductive apparatus is the same one for the two sexes. 1. Anus 2. Labioscrotal folds 3. Legs 4. Genital tuber 7. Urethral groove 8. Urogenital folds At the ninth week, there are not yet any notable differences. The boy is on the left and the girl on the right. You find the same structures on both fetus.
- Development dependent upon Dihydrotestosterone which is produced by the testes on the 11-13 weeks of gestation, With a boy, the genital tuber will form the glans penis (4). The body of the penis will be formed by the fusion of the urogenital folds, this fusion is not yet completely finished (7). The scrotum (6) is formed by the fusion of the labioscrotal folds (2). The Raphe [line] of the scrotum (5) corresponds to the zone of fusion of the labioscrotal folds. ventral side of the developing
- In the absence of the SRY gene, of the Y chromosome, a female embryo will develop. The development promoted by the presence of estrogen and other hormones within the maternal system. T The phallus/ genital tuber continues to grow to become the clitoris. urogenital folds are developing into the labia minora. Their devThey grow up along side the phallus except that in the female, they fuse only at the most posterior aspect (bottom) to form the frenulum labiorum pudendi or fourchette.
- The urethral meatus is abnormally positioned in this condition, opening proximally and ventrally to its normal position. The sonographic findings of hypospadias are: anomalous distal morphology of the penis (it loses its pointed end, which becomes blunter or straighter, in the form of a squashed cone) , small lateral folds seen as longitudinal echogenic lines (dermal remains of the prepuce), small penis, ventral incurving (chordee) due to a fibrous band along the normal span of the spongy body and anomalous urinary stream (due to an anomalous opening of the urethra on the ventral surface of the penis)
- 34 weeks of pregnancy; Images show the ovarian cyst localized in the left lower part of the abdomen with intracystic round structure "daughter cyst sign".
- Hydrocolpos is congenital cystic dilatation of the vagina caused by obstruction of the distal genital tract, with accumulation of fluid and mucus secretions. The clinical and ultrasound features of neonatal presentation have been well described, but diagnosis of fetal hydrocolpos on prenatal ultrasound is still rare. (A) Sagittal ultrasonography of the fetal pelvis shows a pear-shaped mass (arrow) presenting as a blind pouch at the distal end of the fetal vagina (arrowhead). (B) Transverse ultrasonography demonstrates a fluid-filled mass (arrow) behind the urinary bladder (arrowhead).