A 30-year-old woman presented to her primary-care physician with a 2-year history of intermittent right ﬂank pain. The pain typically occurred on weekends after episodes of binge drinking. A urine dipstick was negative for blood. Her creatinine level was 0.9 mg/dL, and her blood pressure was mildly elevated.
Shawn Corey, MD, PhD, Robert Bechtold, MD,
Raymond Dyer, MD,
Department of Radiology, Wake Forest Baptist Medical Center,
A 30-year-old woman presented to her primary-care physician with
a 2-year history of intermittent right flank pain. The pain
typically occurred on weekends after episodes of binge drinking. A
urine dipstick was negative for blood. Her creatinine level was 0.9
mg/dL, and her blood pressure was mildly elevated.
Ureteropelvic junction obstruction in the lower moiety of an
incompletely duplicated collecting system secondary to an accessory
precaval renal artery
This patient's repeated episodes of right flank pain suggested
partial obstruction of the right renal collecting system. Standard
radiographs obtained after intravenous administration of contrast
material for computed tomography (CT) revealed incomplete
duplication of the right renal collecting system (Figure 1). The
lower moiety collecting system was dilated, whereas the upper
moiety collecting system was normal (Figure 1A). During
fluoroscopy, arterial pulsations were observed at the ureteropelvic
junction (UPJ) of the lower moiety, which suggested that a crossing
vessel was contributing to the UPJ obstruction. In the supine
position, little contrast material passed from the lower moiety
collecting system into its ureter. Instead, contrast material
refluxed from the shared right ureter into the lower moiety
collecting system, indicative of yo-yo reflux (Figure 1B).
An oblique coronal CT reconstruction showed 2 right renal
arteries (Figure 2A). The right upper pole artery (RUPA) crossed
posterior to the inferior vena cava (IVC), whereas the right lower
pole artery (RLPA) crossed anterior to the inferior vena cava
(IVC). Three-dimensional (3D) volume-rendered images verified this
finding and the spatial relationships (Figures 2B, C, and D). Axial
imaging confirmed the location of the renal arteries relative to
the IVC (Figure 3). The right lower pole renal artery and two renal
veins crossed the UPJ at the site of obstruction (Figure 3D). This
was also the site where vascular pulsations were noted at
fluoroscopy. Surgical correction for partial UPJ obstruction
secondary to a precaval right renal artery was recommended.
Currently, the patient has opted for conservative management.
In adults, partial obstruction of a ureter or renal collecting
system often presents as intermittent flank pain exacerbated by the
consumption of large volumes of fluids. The condition that occurs
with binge beer drinking, as was the case for this patient, has
been coined "beer drinker's hydronephrosis." In children, typical
symptoms of partial obstruction include pain, nausea, vomiting,
hematuria after trauma, or an abdominal mass.
The exact incidence of UPJ obstruction in the setting of incomplete
ureteral duplication is uncertain but is considered exceedingly
rare. Obstruction in duplex systems was originally described at the
lower pole UPJ; however, it is now known to occur at the upper pole
UPJ as well.
Renal vascular variations are becoming increasingly easy to
recognize with advances in CT and contrast-enhanced ultrasound.
Renal artery duplication occurs in approximately 25% of the
population. On the other hand, precaval renal arteries are rare and
occur in approximately 0.8% of the population.
Precaval renal arteries have been reported with normal renal
position and rotation, fused enlarged kidneys, and bifid collecting
The precaval artery often feeds the lower pole, has a similar
caliber to the main renal artery, and is found dorsal to the
Precaval renal arteries are important to recognize, because they
can be mistaken for an aberrant hepatic artery during sonography
and are relevant to surgical planning for nephrectomy and aortic
In approximately 50% of patients with UPJ obstruction, a
crossing vessel plays a contributing role.
Both crossing arteries and veins can lead to obstruction.
CT is highly accurate both in detecting an obstruction and in
determining whether there is an associated crossing ves-sel.
Correction of UPJ obstruction can be accomplished by either
endourologic or surgical approaches. Endourologic approaches
involve inserting a cutting device into the ureter across a
stenotic segment. A vertical incision is made at the site of
obstruction, which is then supported with a stent. In laproscopic
or open surgical pyeloplasty, the renal pelvis and proximal ureter
are surgically reconstructed. During the endourologic approach,
failure to recognize a crossing vessel can lead to vascular injury.
In addition, endopyelotomy success rates drop from 82% to 33% in
the presence of a crossing vessel
(others report slightly better rates of 42% to 64%
). On the other hand, laparoscopic pyeloplasty has been reported to
be 86% to 100% successful in cases with a crossing vessel and
seldom leads to vascular injury.
Thus, in the presence of a crossing vessel, a laparoscopic or open
approach is preferred over endopyelotomy because of increased
safety and efficacy. Many medical centers have deemed it worthwhile
to adopt special imaging protocols in order to detect vascular
variations prior to surgery. Often, these protocols include
high-resolution CT followed by 3D volume rendering.
CT is highly accurate at depicting renovascular anatomy,
detecting UPJ obstructions, and determining whether a crossing
vessel is playing a contributing role. Recognition of crossing
vessels prior to surgery can decrease the risk of vascular injury,
improve surgical outcomes, and alter the surgical approach.
Although precaval renal arteries occur rarely, they are important