Discussion
NCS is an uncommon condition that presents in varied ways. However, this
review demonstrates that commonalities exist among NCS patients, which
should raise suspicion among clinicians. The majority of patients were
young, female, and present with left flank pain and/or hematuria, which
is likely due to the rupture of thin-walled varices formed from renal
hypertension into the collection system. [3] Features of pelvic
congestion, such as dyspareunia, dysmenorrhea, scrotal or testicular
pain, or urinary issues, might also evince NCS. Even refractory
headaches can be related to LRV compression. Any of these symptoms in
this patient population should raise suspicion of NCS in the absence of
a more obvious diagnosis. Additionally, a normal to low BMI also appears
to be associated with NCS. Not enough reports in this review included
BMI information for us to include this data, but anecdotally, most
reports of NCS occur in normal or underweight patients. A decreased
aortomesenteric angleāor the angle between the SMA and aorta, risks
compression of the LRV as it does to the duodenum in SMAS. [19, 45]
This is more likely to be found in underweight patients, who have
decreased retroperitoneal and mesenteric fat.
There are multiple imaging modalities that can be used to diagnose NCS.
While the gold standard is retrograde venography, this invasive
procedure is not always necessary. It is established that a pressure
gradient between the LRV and inferior vena cava less than 1 mm Hg is
normal, whereas greater than 3 mm Hg evinces nutcracker phenomenon and
NCS with symptoms. [19, 46]. It has been suggested that this
pressure gradient can be estimated fairly accurately from Doppler
ultrasound, by measuring differences in flow velocities. [46]
Additionally, the size of the LRV can similarly be measured with Doppler
ultrasound, to demonstrate a stenosis. [15, 39, 46]. CT imaging can
also show a decreased aortomesenteric angle, which when less than 38 to
45 degrees is considered abnormal. [45, 46] CT imaging can also show
LRV compression. CT venography is preferable but not necessary in many
of the studies we reviewed, which used CT of the abdomen pelvis or CT
angiography to arrive at an NCS diagnosis. Overall, when NCS is
suspected, invasive procedures are not necessary to arrive at a
diagnosis. Relatively low risk procedures such as Doppler ultrasound and
CT are available and should be used.
Regarding treatment, endovascular stenting was predominant. Some
therapies aim at alleviating specific symptoms without disturbing the
renal vein, such as gonadal vein transposition for pelvic congestion
syndrome or lumbar vein embolization for headaches. Unfortunately, there
was also not enough information in the reports regarding post-treatment
course to determine if any of the treatment modalities are effective in
the long term, and which would be preferable. More research is needed to
determine the best methods of treatment. Future studies might directly
compare the long-term effectiveness of conservative modalities, such as
nutritional support, with endovascular or surgical options. There is
still significant variation in treatment modalities. It may be that
these should be adjusted to individual cases.
Our study was deficient in several ways. As stated, we did not include
statistics on BMI. We also were unable to include information on
outcomes of therapy, as most records did not state this. This study is
retrospective in nature. Overall this was a small study population. It
also included numerous institutions in different countries, which likely
have different standards of practice. We did not include pediatric
patients in this review.