Answer to case
This Figure shows marked localised dilatation of the lower third of the left
ureter, with mild prominence of the collecting system proximally. The differential
diagnosis includes chronic ureteric obstruction, vesicoureteric reflux, diabetes
insipidus, psychogenic polydipsia or primary megaureter. This is primary
megaureter, which is a congenital condition and is typically a unilateral process,
occurring more frequently on the left and in males. The etiology is abnormal
muscle development within a segment of ureter near to the vesicoureteric junction.
This leads to reduced peristalsis and subsequent dilatation of the distal ureter
which tapers smoothly just proximal to the vesicoureteric junction. In rare
cases the whole ureter and pelvicalyceal system may be dilated, i.e. megaureter
with megacalycosis.