Renal - Embryology and Anatomy

Question 1

Kidney embryology

• Pronephros
• Mesonephros
• Ureteropelvic junction

Answer 1

• Pronephros
  
  • Week 4
  • Then degenerates.
• Mesonephros
  
  • Functions as interim kidney for 1st trimester
  • Later contributes to male genital system.
• Ureteropelvic junction
  
  • Last to canalize
  • –>Ž most common site of obstruction (hydronephrosis) in fetus.

Question 2

Kidney embryology:
Metanephros

• Definition
• Ureteric bud
• Metanephric mesenchyme
• Aberrant interaction

Answer 2

• Definition
  
  • Permanent
  • First appears in 5th week of gestation
  • Nephrogenesis continues through32–36 weeks of gestation.
• Ureteric bud
  
  • Derived from caudal end of mesonephric duct
  • Gives rise to ureter, pelvises, calyces, and collecting ducts
  • Fully canalized by 10th week
• Metanephric mesenchyme
  
  • Ureteric bud interacts with this tissue
  • Interaction induces differentiation and formation of glomerulus through to distal convoluted tubule
• Aberrant interaction between these 2 tissues may result in several congenital malformations of the kidney

Question 3

Potter sequence (syndrome)

• Findings
• Due to…
• Associated with…

Answer 3

• Findings
  
  • Oligohydramnios Ž–> compression of developing fetus Ž–> limb deformities, facial anomalies (low-set ears and retrognathia [arrows in (A)]), and compression of chest –>Ž pulmonary hypoplasia (cause of death).
  • Babies who can’t “Pee” in utero develop Potter syndrome.
• Due to…
  
  • Causes include ARPKD, posterior urethral valves, bilateral renal agenesis.
• POTTER syndrome associated with:
  
  • Pulmonary hypoplasia
  • Oligohydramnios (trigger)
  • Twisted face
  • Twisted skin
  • Extremity defects
  • Renal failure (in utero)

Question 4

Horseshoe kidney

• Definition
• Findings

Answer 4

• Definition
  
  • Inferior poles of both kidneys fuse [A].
  • As they ascend from pelvis during fetal development, horseshoe kidneys get trapped under inferior mesenteric artery and remain low in the abdomen.
• Findings
  
  • Kidney functions normally. 
  • Increased risk for ureteropelvic junction obstruction, hydronephrosis, renal stones, and rarely renal cancer (Wilms tumor).
  • Associated with Turner syndrome.

Question 5

Multicystic dysplastic kidney

• Definition
• Findings
• Diagnosis

Answer 5

• Definition
  
  • Due to abnormal interaction between ureteric bud and metanephric mesenchyme.
• Findings
  
  • This leads to a nonfunctional kidney consisting of cysts and connective tissue.
  • If unilateral (most common), generally asymptomatic with compensatory hypertrophy of contralateral kidney.
• Diagnosis
  
  • Often diagnosed prenatally via ultrasound.

Question 6

Kidney anatomy and glomerular structure (524)

Answer 6

• The left kidney is taken during living donor transplantation because it has a longer renal vein.

Question 7

Ureters

• Course
• Gynecologic procedures

Answer 7

• Course
  
  • Ureters pass under uterine artery and under ductus deferens (retroperitoneal).
  • “Water (ureters) under the bridge (uterine artery, vas deferens).”
• Gynecologic procedures involving ligation of the uterine vessels may damage the ureter –>Ž ureteral obstruction or ureteral leak.