Results from failure of connection between the metanephric blastema and the ipsilateral ureteric bud
Autosomal dominant trait with incomplete penetrance
Typically, absent ipsilateral ureter
Remaining kidney usually hypertrophic
Ipsilateral testis and vas deferens/ovary and fallopian tube are usually absent, and sometimes adrenal gland
Bilateral renal agenesis
Incomplatible with life
Multicystic disease
Results from congenital severe renal dysplasia
If bilateral, incompatible with life
Mostly diagnosed on prenatal USS
Previously excised, but nowadays treated conservatively - cystic kidney tends to regress
Ectopic kidney
Failure of kidney to ascend from the pelvis to its normal position
Commonly, the renal pelvis also faces more anteriorly, as it starts off this way embryologically - the more ectopic the kidney, the more severe the rotational abnormality
In most cases of ectopia, the kidneys are fused together
In 'crossed renal ectopia', the kidneys are fused and are on the same side - one of the ureters crosses the midline to enter the bladder on the correct side
Horseshoe kidney
The two renal units are low-lying and the lower poles fuse to form an isthmus. Further ascent of the fused kidneys is prevented by the IMA.
1 in 1,000, with a 2:1 male predominance
Unpredictable vascular supply
Prone to reflux, obstruction and stone formation
Duplex renal pelvis and ureter
1 in 150
Mostly unilateral
Left side more common
Genetic basis
Children with it often have VUR
Generally asymptomatic when detected in adults
Incomplete duplex - Y ureter
Complete - a normal bud, which ends in the usual place, and a lower bud, which drains the lower pole of the kidney, and the lower bud often gets VUR
In females - opens into the urethra below the sphincter or the vagina. Typical history is of dribbling for as long as she can remember.
In males - the opening is above the external urethral sphincter so the patient is continent. Infection is common, since they are likely to be functionally abnormal.
Refluxing ureters might need reimplantation
Ectopic ureters in females often drain chronically infected renal tissue - best excised
Ureterocoele
Cystic enlargement of the intramural ureter, probably due to atresia of the ureteric orifice
Usually present with infection in childhood
In adults, typically present with stones in the lower ureter
Endoscopic incision can release a stone stuck in a ureterocoele
Nephrectomy may be required for hydronephrosis and severe cases
Congenital megaureter
Ureteric dilation with or without obstruction
Mostly presents in childhood with severe infections
Stones can form
Retrocaval ureter
Can lead to obstruction and the need to surgically move the IVC
