B&B Renal: Anatomy & Physiology Flashcards
Germ layer of origin
Kidney Development
Mesoderm
Pronephros
Kidney Development
- 1st embryonic renal structure
- Forms & degenerates by week 4 of gestation
Mesonephros
Kidney Development
- 2nd embryonic renal strucutre
- Acts as interim kidney during 1st trimester
- Contributes to vas deferens in males
Metanephros
Kidney Development
- 3rd embryonic renal structure
- Forms permanent kidney
- Appears during 5th week gestation
- Develops into kidney through weeks 32-26
Kidney Formation
2 key structures
1. Ureteric bud
2. Metanephric mesenchyme
Ureteric bud
Kidney Formation
- Outgrowth of mesonephric (Wolffian) duct
- Forms ureter, renal pelvis & calyces, collecting ducts
Metanephric mesenchyme
Kidney formation
- Mesoderm tissue around ureteric bud
- Interacts with ureteric bud to form glomerulus through distal tubule of nephron
Most common renal malignancy in young children
Wilm’s tumor
Abnormal proliferation of metanephric mesenchyme
* Produces embryonic glomerular structures
* Associated with WT1 mutations
* WT1 is expressed in metanephric mesenchyme
Pathophysiology
Wilms’ tumor
Absence of one or both kidneys at birth
* Unilateral: remaining kidney compensates
* Hypertrophy
* Hyperfiltration
* Risk of FSGS
* Risk of renal failure after decades
* Bilateral:
* Oligohydramnios
* Potter’s syndrome
FSGS: focal segmental glomerular sclerosis
Renal Agenesis
Congenital Anomaly
Renal Agenesis
Pathophysiology
- Ureteric bud fails to develop
- Lack of signals to mesenchyme to trigger differentiation
Renal dysplasia resulting in replacement of kidney with cysts
* No / little functioning renal tissue
* Usually unilateral
Multicystic Dysplastic Kidney
Congenital Anomaly
Multicystic Dysplastic Kidney
Pathophysiology
Abnormal ureteric bud-mesenchyme interaction
- Common cause of single kidney obstruction
- Narrowing in proximal ureter at UPJ
- Often detected in utero
- Can be treated surgical after birth
Ureteropelvic junction (UPJ) obstruction
UPJ obstruction
Complications
- Hydronephrosis
- Poor urinary flow –> kidney stones, UTIs
Duplex Collecting System
Duplicated Ureter
- Occurs when 2 ureteric buds form on right / left side or if a ureteric bud bifurcares during development
- Results in formation of upper / lower kidneys
Duplicated Ureter
Complications
- May lead to poor urinary flow; UTIs
- Hydronephrosis
- Associated with vesicoureteral reflux
- Backward urine flow from bladder to kidneys
- Leads to recurrent UTIs
Vesicoureteral reflux
Abnormal closure of UVJ
* Occurs in children
* Associated with duplex ureters
UVJ = ureterovesical junction; where ureter inserts into bladder
Primary vesicoureteral reflux
Retrograde flow of urine due to high bladder pressure
* Associated with posterior urethral valves
Secondary vesicoureteral reflux
Retrograde flow of urine due to high bladder pressure
* Associated with posterior urethral valves
Secondary vesicoureteral reflux
Loss of fetal cushioning to external forces resulting from decreased / absent amniotic fluid
* External compression of fetus: abnormal face / limb formation
* Alteration in lung liquid movement: abnormal lung formation
* Often fatal
Potter’s syndrome
Potter’s syndrome
Pathophysiology
- Amniotic fluid = fetal urine
- Severe fetal renal malfunction = decreased amniotic fluid
- Limb deformities
- Flat face
- Pulmonary hypolasia
- Often fetal death
Signs
Potter’s syndrome
- Limb deformities
- Flat face
- Pulmonary hypolasia
- Often fetal death
Signs
Potter’s syndrome
Low amniotic fluid levels
Oligohydramnios
Oligohydramnios
Etiology
Causes vary by trimester
* 1st trimester: rare
* 2nd trimester: low fetal urine production
* 3rd trimester: rupture of membranes
1st: 1-12 weeks; 2nd: 13-27 weeks; 3rd: 28 weeks - birth
Potter’s syndrome
Etiology
- Bilateral renal agenesis
- Often detected in utero
- U/S: kidneys not seen by 10-12 wks
- Posterior urethral valve
- Occurs in males
- Valve obstructs bladder outflow
- U/S: dilated bladder, kidneys
- Both kidneys are affected
- Autosomal recessive PKD
- Juvenile cystic kidney disease
- Cysts form in kidneys & biliary tree
- Both kidneys are affected
- Severe: oligohydramnios
- Less severe: renal failure & HTN in childhood
PKD = polycystic kidney disease
Fused inferior poles of kidneys
* Kidneys cannot ascend from pelvis to retroperitoneum
* Trapped by inferior mesenteric artery
Horseshoe kidney
Horseshoe kidney
Presentation
- Most pts are asymptomatic
- A/w Turner & Down syndromes
- A/w vesicoureteral reflux
- Embryologic structure that connects dome of bladder to umbilicus
- Becomes obliterated at birth & becomes median umbilical ligament
Urachus
Urachal remnants
Failed / incomplete obliteration of urachus
* Patent urachus: urine can leak from umbilicus
* Failed obliteration of urachus
* Urachal cyst / sinus / diverticulum
* Incomplete obliteration of urachus
* Can lead to infections
Urachal remnants
Complications
Can lead to adenocarcinoma of the bladder
* Key feature: tumor at dome of bladder
* Presentation: adult with painless hematuria
Kidney
Anatomy
3 major regions
1. Cortex: outer region
2. Medulla: middle region
3. Collecting system: inner region