Congenital anomalies of the kidneys and urinary tract

Difference between bilateral renal agenesis and unilateral renal agenesis

bilateral: incompatible with life

unilateral: usually asymptomatic + remaining kidney is hypertrophic

How does renal agenesis occur?

Failure of the ureteral bud to develop from the mesonephric duct
Failure of the metanephric blastema to develop in the absence of inductive signals from the ureteric bud

What causes renal hypolasia?

inadequate branching of the ureteric bud or arrested development of the metanephric blastema

what is the name of renal hypoplasia with a decreased n.o of nephrons?

oligomeganephronia

What is the name for having more than 2 kidneys and how are the kidneys found/ interacting with the body?

Supernumerary kidney

has own collecting system, blood supply and distinct encapsulated parenchymal mass
may be totally separate from the normal kidney or connected to it by loose tissue

What happens in Renal ectopia?

Mature kidney fails to reach its normal location (pelvic kidney is most common) 

** kidneys usually fuse

** Axis of the kidney frequently affected (malrotation)

What is cross renal ectopia?

kidney crosses to the other side and is lower down

What is the condition called where the kidneys fuse during their ascent from the pelvis and how does this effect the patient?

Horseshoe kidney

Increased incidence of kidney stone disease

What are the different ways the ureter can duplicate?

Complete duplication of ureter: 2 ureteral buds, one in the normal location and the other lower

Partial duplication of ureter (bifid): premature bifurcation of the ureteric bud before entering the metanephric blastema

** Unilateral duplication is more common than bilateral

Describe the different anomalies of renal vasculature

Multiple renal arteries: kidney supplied by more than one vessel originating from the aorta

Aberrant renal artery: originating from vessels OTHER THAN the aorta or main renal artery

How do accessory renal arteries happen?

Result from the failure of transient renal arteries to regress during the ascent of the kidneys

What mutation causes ADPKD and how does it do it ?

mutations in the genes PKD1 (chromosome 16p13.3)

→ PKD1 encodes polycystin-1,an integral membrane protein thought to play a role in cell-cell and cell-matrix interactions

or PKD2 (chromosome 4q21)

→ PKD2 encodes polycystin-2, involved in calcium channel regulation

** lead to structural changes in renal cells, resulting in increased rates of cell proliferation, apoptosis and remodelling of the ECM

What is ADPKD?

Autosomal dominant polycystic kidney disease

leads to the development of multiple bilateral cysts on the kidneys → progressive loss of functional renal tissue

How do cysts form in Autosomal dominant polycystic kidney disease?

1. Renal cysts originate as outpouchings of tubules

2. They expand and eventually separate from the parent tubules, yielding cysts.

3. Cyst grow due to proliferation of the cyst lining cells and abnormal fluid accumulation.

4. Cyst expansion and fibrosis causes compression and obstruction of normal tubules, resulting in upstream tubular dilation.

5. Kidneys become massively enlarged, and kidney function progressively declines

How do you diagnose Autosomal dominant polycystic kidney disease (ADPKD)?

History:

• family history

• age 30-40

• flank pain and haematuria

Extrarenal manifestations

• Hypertension

• Hepatic cysts

Diagnosis

• Renal ultrasound: shows renomegaly and cysts

• genetic testing (to make sure)

Why is haematuria a symptom for ADPKD?

due to traumatic or atraumatic cyst rupture or infection

How does ADPKD progress?

Progressive increase in the number and size of cysts and enlargement of the kidneys

May develop renal failure 

Treatment of of ADPKD

no proven treatment

Tolvaptan (selective vasopressin antagonist)

Kidney transplant

How can Tolvaptan help in ADPKD?

Tolvaptan (selective vasopressin antagonist)
inhibits the binding of vasopressin to the V2 receptors → reduces cell proliferation, cyst
formation and fluid excretion → reduces kidney growth and protects kidney function