Kalabhavi Srinivas K.pdf

2. Extrinsic causes:
Proforma
An aberrant, accessory, or early branching lower pole vessel is the most
common cause of extrinsic UPJ obstruction. This is a major case of UPJ obstruction
in adults.
These vessels pass anteriorly to the UPJ or proximal ureter and contribute to
mechanical obstruction. Nixon (1953) reported that 25 of 78 cases of UPJ
obstruction were secondary to vascular compression. Other reported incidences have
varied between 15% and 52% (Ericsson et al, 1961; Williams and Kenawi, 1976,
Johnson et al, 1977; Stephens, 1982; Lowe and Marshall, 1984). Whether the
aberrant vessel causes obstruction or is a co-variable that exists along with an
intrinsic narrowing is unclear.
Stephens (1982) theorized that when an aberrant or accessory renal artery to
the lower pole of the kidney is present and the ureter courses behind it, the ureter may
angulate at both the UPJ and the point at which it traverses over the vessel as the
pelvis fills and bulges inferiorly. Further angulations of the ureter occurs as it
becomes adherent to the UPJ secondary to an inflammatory process. A two-point
obstruction ensues, with kinking of the ureter at the UPJ and at the point where the
ureter drapes over the vessel. Stephens (1982) could find no evidence of stricture or
fibrosis at these points when the ureter was freed of its adhesions and lifted off the
vessel. However, he suggested that over time, these areas may become ischemic,
fibrotic, and finally stenotic 16 .