Self-compressing tronc-rénorachidièn causing extreme pain after a meal
Vascular compression syndromes of the abdomen and pelvis are a common cause of pain that radiates from the abdomen and pelvis to the chest, back and legs.
Circulatory bypasses (collaterals)are of particular importance to those affected, as they divert blood to the heart despite the pinching of important veins.
A little-known but very important bypass circuit of the left renal vein is the tronc réno-rachidièn, which develops in these patients and is not normally found. It connects the left renal vein with the veins of the spinal column and the spinal canal.
In the present case, a very strongly developed tronc réno-rachidiè was the only effective bypass circuit of the left renal vein, as the ovarian vein was unable to participate in the diversion of renal vein blood from the kidney into the pelvis due to an obstruction of the pelvic veins (May-Thurner syndrome).
The patient in this case regularly developed unbearable pain in the epigastric angle slightly to the left of the midline at the base of the epigastric triangle and in the left flank and left below the ribs after eating.
The cause in this case was the spatial constriction in the upper abdomen, which had initially led to compression of the left renal vein. Such situations always arise due to the elevation of the aorta with pronounced lordosis of the lumbar spine, whereby the left renal vein can be displaced by various structures. In rare cases from the superior mesenteric artery, frequently from the right renal artery, but in this case from the stomach. After eating and the associated filling of the stomach with simultaneous compression of the gastric outlet between the aorta and the abdominal wall, the large gastric curvature bulges particularly strongly. This further compresses the already very stretced, congested left renal vein. However, this is precisely when a well-functioning bypass circulation is important. Although this patient had developed a strong bypass circulation in the form of a tronc réno-rachidièn, it was folded up like an accordion by the stomach as soon as the patient ate. The tronc réno-rachidièn had developed a tortuosity that can be compressed particularly easily.
The following video demonstrates the special conditions in order to draw attention to the fact that the presence of collateral circulation alone is not able to guarantee adequate function of the kidney and renal circulation in all cases and under all circumstances.
Only a functional ultrasound examination with close observation of the vascular conditions before, during and after food intake as well as changes in posture can help in such complicated cases.
The effect of vascular compression is exacerbated by the physiological increase in renal perfusion after a meal.
The additional renal flow increases the pressure in the left renal vein. However, instead of increasing blood flow, this only increases the pressure within the renal vasculature – causing the pain, but reduces the total flow volume in contrast to the right side, as shown in the diagram below. A twofold increase in the flow volume of the right kidney is mirrored by a 10% decrease in flow in the left kidney, despite an increase in pressure.

PixelFlux-measurementes of the renal perfusion
The functional reserve of the kidneys is mobilised to excrete waste products (including urea and ammonium) after a meal. This is reflected in the increased perfusion of the peripheral parenchyma of the kidney. This area is dominated by smaller vessels that are less perfused than the more central vessels. After a meal, the perfusion of the peripheral vessels increases to mobilise the reserve capacity of the kidneys to improve post-prandial detoxification.
The following diagram illustrates the severely reduced ability of the congested left kidney to increase peripheral perfusion in response to food intake. The reserve capacity of the left kidney is exhausted and cannot respond to additional demand. This is due to the increasing back pressure from the congested left renal vein. As the congestion is massively increased by the kinking of the main collateral, the tronc réno-rachidièn, the counter-pressure against the venous outflow increases further after a meal due to the squeezing of this zigzag-like vessel in this particular patient. This prevents an increase in peripheral perfusion, in contrast to the unaffected right kidney.

PixelFlux-measurementes of the renal perfusion
see:
- Chan AY, Cheng ML, Keil LC, Myers BD. Functional response of healthy and diseased glomeruli to a large, protein-rich meal. J Clin Invest. 1988 Jan;81(1):245-54. doi: 10.1172/JCI113302. PMID: 3275694; PMCID: PMC442500.
- Bankir L, Roussel R, Bouby N. Protein- and diabetes-induced glomerular hyperfiltration: role of glucagon, vasopressin, and urea. Am J Physiol Renal Physiol. 2015 Jul 1;309(1):F2-23. doi: 10.1152/ajprenal.00614.2014. Epub 2015 Apr 29. PMID: 25925260.