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Pelvic congestion is very common in patients with vascular compression syndromes. The reason for this is that lordotic compression of the left renal vein and the left common iliac vein retains blood in the legs and pelvis.

Compression of the left renal vein is the main cause of pelvic congestion. The kidney receives large amounts of blood that far exceed the transport capacity of the left common iliac vein, which is mainly fed by the pelvic organs via the internal iliac vein and by the leg via the external iliac vein. Both then unite to form the common iliac vein, which is often compressed in front of the fifth lumbar vertebra, as this is extremely prominent in most patients with compression syndromes due to the exaggerated lumbar lordosis.

As a rule, compression of the left renal vein is the first compression syndrome to develop during puberty. The natural bypass for the congested blood that cannot easily leave the left kidney is the left ovarian vein. The ovarian vein connects the left ovary with the left renal vein and thus serves as an escape route when the pressure in the left renal vein rises. The blood flow then changes direction and flows caudally (downwards), with large amounts of blood that cannot be transported via its normal direction, the left renal vein, flowing into the left side of the pelvis.

The blood first reaches the left ovary and from there can enter the network of veins around and in the uterus via the veins in the left fallopian tube. Once in the uterus, the blood tries to cross the myometrium (the muscle layer of the uterus). This is not easy as the uterus is a dormant muscle with only relatively small veins. The uterus is the home of the fetus and only develops larger veins during pregnancy. Therefore, the non-pregnant uterus exerts a high counterpressure against the flow of blood through the myometrium. If the blood nevertheless manages to cross the uterine lining, it is absorbed by the right-sided veins of the uterine plexus and the veins of the right fallopian tube. Once it has reached the right ovary, it usually passes via the right ovarian vein into the cranial section of the inferior vena cava and from there directly into the right atrium of the heart.

The more common route of congested blood from the left renal vein after entering the left ovary and the many parauterine and perivesical veins, which form a wide venous network in the pelvis, leads to the natural outflow vein of these venous plexuses – the left internal iliac vein. The most common drainage route of an obstructed left renal vein therefore leads via the left internal iliac vein into the left common iliac vein, which crosses the promontory and discharges its blood into the origin of the inferior vena cava.

However, this collateral route is associated with 2 major obstacles.

1. The first mechanical problem is the discrepancy in blood flow volume in the flooded left internal iliac vein, which is in addition to the normal flow volume of the left common iliac vein. The left common iliac vein must therefore expand to accommodate the additional renal blood. This dilation can be the source of pain in the left pelvis, left groin, left leg and genitals, but is also the source of the increasing pressure pushing blood across the uterus into the above pathway. The result is deep pelvic pain that originates from the uterus itself, but also causes congestion in the neighboring pelvic organs. These are the vagina, the urethra, the bladder and the rectum. Varicose veins can form in all of these organs, causing swelling of the mucous membrane of these hollow organs, constriction and pain. The pain is caused by chronic inflammation of the venous wall in the dilated veins. As increased venous pressure is the main reason for the development of chronic venous inflammation, sudden changes in pressure (lifting a weight, laughing, jumping or defecation) are particularly painful in the vagina, bladder and other organs that receive blood.
2. The second obstacle is increasing lordosis as patients get older and lordosis increases due to a higher spine, increasing body weight and increasing laxity of the (female) connective tissue. As a result, the fifth lumbar vertebra is pushed ventrally (towards the abdominal wall). Sometimes only a tiny gap of a few millimeters to less than 2 cm remains, which is insufficient to allow food in the small intestine and blood from the left side of the pelvis to pass simultaneously. Normally, 3 cm is the minimum requirement for pain-free coexistence of intestinal loops and veins in this region. The continuous ventral (forward) displacement of the fifth lumbar vertebra usually compresses the crossing left common iliac vein at the point of contact with the right common iliac vein. This condition is known as May-Thurner syndrome.

The higher volume and the compression of the left common iliac vein therefore both contribute to pelvic congestion.

Pelvic congestion is usually associated with pain in the genitals – which is basically true.

However, urethral obstruction causes specific problems that are often associated with pelvic congestion. They begin with impaired voiding behavior. Patients have to empty their bladder frequently, produce only small amounts of urine per voiding, emptying the bladder becomes painful, blood can be detected visually or with a dipstick and more force is required to get rid of the urine. This may even lead to incomplete voiding and may require catheterization of the bladder.

I therefore present the case of a 15-year-old girl who was the victim of multiple vascular compressions and who was treated very successfully with a simultaneous decompression operation (by Professor Sandmann) of the left renal and left common iliac vein. In addition, a coexisting median arcuate ligament syndrome and a compression of the duodenum (SMA-syndrome / Wilkie-syndrome) was corrected during the same operation.

Her main problem was the inability to empty her bladder. After a period in which she required increased abdominal pressure to empty her bladder, she developed a larger residual bladder volume after micturition, which forced her to catheterize herself several times a day. Further symptoms were chronic and postprandial accentuated, mostly epigastric and left-sided abdominal pain as well as weakness in the left leg.

In the words of the patient:

The retention started in March 2023 after a cystoscopy (to check for a PUJ obstruction), and it became worse and worse until in 2024 I had to go to ED often 2-3 times a week for catheters. I was told that going to ED was the best the paediatricians could offer me. They had done a spine MRI early on to check for cauda equina. When it was negative, I was told nothing was wrong with me and even that this was all in my head.

A few months and several ED visits and hospital stays for catheters later, I had a voiding study, which showed that I couldn’t empty my bladder fully. At the end of the day, I had over 1 litre of urine in my bladder and the nurse was very concerned. Yet, the paediatric surgeon (where we live paeds surgeons are in charge of children’s urology) refused to see me and sent me home, even though I was very uncomfortable. The next morning, I had to go to ED and had 2 litres in my bladder.

I was privately diagnosed with hEDS in August but the doctors in my public hospital insisted the retention was unrelated (and they said they didn’t believe in EDS, in any case).

As I needed an ultrasound anyway, my mother asked the paediatric surgeon, if at the same time, they could please check for Nutcracker Syndrome. The paediatric surgeon condescendingly told us that this wasn’t Nutcracker but, as my mother insisted, included it in the ultrasound. Unfortunately, they were not able to look for it during the ultrasound.

In early November 2023, I had a urodynamics study as the paeds surgeon thought this was Fowler’s Syndrome. The urologist who did the urodynamics study did not agree, but, as I was in retention and could not pass urine, the study was inconclusive, and I was told again this was in my head. During this time, I was an inpatient for 7 weeks (and, after a short break) for another 4 weeks in the children’s hospital for malnutrition and medical instability with a very low heart rate, as since April I had been vomiting up my food and drink – up to 15 times a day.

Later that November, I was (privately) diagnosed with AVCs [Abdominal Vascular Compressions – TS]. The radiologist commented that from the pelvic congestion, blood vessels were enlarged around the urethra which could cause the urinary retention, but the paediatricians in our public hospital did not believe this was true. They told us also that they don’t believe in AVCs, as they cannot treat them in our country.

The constant ED visits were taking a toll on me and my family, especially as the nurses who placed my catheters were often very rough and kept complaining that I was coming to ED so often for catheterisation (each time with 1.5-2 litres in my bladder and in terrible pain). As we did not get help where we live and I had some problems with hydronephrosis, we saw a urologist privately in another city, whom our vascular surgeon had recommended to us. He was shocked how long the paediatricians had been ignoring the issue and how I was treated in ED in our hospital. He told us the retention was because of the EDS and that I should learn to self-catheterise to protect my bladder and kidneys from further damage.

We travelled there to see his nurse so I could learn to self-catheterise, which I needed to do three times a day. The self-catheterisation was much better (and less painful) than going to ED and dealing with the terrible treatment there but still had a huge impact on my day-to-day life.

In October 2024, I had vascular decompression surgery in Düsseldorf. Since then, I have been able to pass urine without needing to self-catheterise.

The reason for the inability to void her bladder was a massive congestion of the urethra. The enlarged veins encircling the urethra formed a cuff which compressed the urethra. The increasing pressure in these urethral veins finally reached a point where the patient was not able to overcome this pressure with her abdominal and bladder muscles. This was the beginning of her self-catheterization.

The colour Doppler ultrasound videos and the PixelFlux measurement of the urethral congestion are the basis of understanding of this condition.

Only by PixelFlux measurements this urethral congestion can be quantified non-invasively. If this is missed and no other reason, either neurological or obstructive can be found, catheterization is the only way to prevent severe renal damage due to urinary reflux.

The main problem is often a severe compression of the left renal vein as demonstrated below. MRI and CT not rarely fail to evaluate the impact of the venous narrowing properly. Functional color Doppler ultrasound however with PixelFlux measurements can not only show even very short compressions due to its unrivaled spatial resolution but more importantly can quantify the volume burden for the collaterals, namely the left ovarian vein.

So the frequent misinterpretation of a pelvic congestion as an insufficiency of the left ovarian vein is avoided.  The left ovarian vein is not insufficient but needs to dilate to maintain a normal left renal function. If wrongly assumed that the main problem is the left ovarian vein then the fatal conclusion to coil or foam or ligate this vessel is drawn.

This reduces the pelvic congestion for 4 to 12 weeks at the expense of increasing pain in the left flank until new but more painful collaterals have formed, which direct the blood from the left kidney back into the left pelvic venous circulation.

The high flow velocity points to the high pressure in the left kidney that is felt as left flank of left lower thoracic pain.

After decompression of the left renal vein by wrapping it into a tunnel made of a PTFE-sheath the renal venous pressure and thus also the flooding of the left ovarian vein drops.

The congestion of the pelvis disappears as does the urethral congestion.  The patient can urinate again.

After decompression of the left renal and left common iliac vein the volume return was higher and the collapse of the vena cava disappeared as the dropping flow velocity confirms.