I'm not sure about your knowledge level of lymphatics, so I will give you a quick primer from what I can remember. The adjacent lymphatic vessels which "serve" the GI tract (mesenteric, femoral, and inguinal I believe would be primary ones) receive extracellular fluid that is exchanged in the peritoneum from the intestines. This fluid will be rich with dead cells that originate in the GI tract, including many components which are toxic and illicit an immune or inflammatory response, which are largely interconnected. There are pressure gradients between the lymphatic vessels and interstitial fluid that allows for the lymphatic vessels to be filled. This occurs via a process that involves a number of different kinetic mechanisms, but the point to understand is that once the fluid passes the epithelium of the lymphatic vessel, it stays inside the lymphatic system; the fluid does not pass back into the interstitial space.
Once inside the lymphatic system the flow is also unidirectional and there are bicuspid valves, which keep the fluid from flowing backward. The fluid gets moved by a number of forces including the contraction of skeletal muscle, and the contraction of the smooth muscle within the valves. Propulsion is also chemically mediated, and this is the important part, the force of these smooth muscle contractions inside the vessels is influenced by the adrenergic system but also by factors humoral immunity. What has been discovered, and something that I have never heard discussed on a message board, is that general inflammatory processes stimulate lymphatic drainage by increasing contractility, but this is not true for endotoxins,which have the opposite effect. Alternatively said, many of the toxins that are filtered through the lymphatic system have the effect of stimulating greater motility; however, the toxic components of gram-negative bacterial cell walls slow down the flow of lymphatic fluid. Endotoxins inhibit the flow of lymph fluid by descreasing the contractility.
The presence of endotoxins from the bowel is what I believe principally accounts for the lymphatic "stagnation" or lymph pain that many report. Many will never experience this because they do not "challenge" the bowels with the requisite organisms to displace gram negative pathogenic bacteria, their immunocompromised status inhibits any significant bacterial displacement, their intestinal permeability is minimal and the endotoxins remain in the bowel, or perhaps they just don't have an abundance of gram negative pathogens. One of the things I have been trying to do over the last year is find a better way to neutralize the endotoxins in the bowel, and I think this is where RS and SCFA's enter the picture.
One other thing to understand is that the lymphathic system is acting as a reservoir to process the endotoxins at a rate that the liver can handle. The lymphatic fluid is ultimately drained into systemic blood circulation where they will quickly be available to the liver. Keeping the lymphatic fluid, with all of the accumulated toxins, out of circulation is seemingly protective. In effect, the rate of propulsion limits the more robust effect that is going to occur if when the lymph fluid enters circulation and the liver cannot effectively process the endotoxins. This is where glutathione depletion occurs to a very large extent, I think. When GSH in the liver is so thoroughly oxidized there is little to export to the other tissues and muscles. (Of course there are issues of synthesis as well, but I see this as largely a protective response, and I am getting way off point).
You should know that the lymphatic network is not a static system, while the fluid is in place there are enzymatic reactions throughout the vessels and nodes that participate in neutralization of the toxins. Chemical process, principally hydrolase enzymes, participate in this chemical neutralization of LPS. These enzymes are one of the "antidotes" to LPS, however, hydrolysis is an energy dependent process. These enzymatic reactions are fueled by ATP, something those with chronic inflammatory illnesses don't have in abundance. Studies of LPS propulsion have also demonstrated that the endotoxins can remain in the vessels for weeks. I would venture a guess that many have experienced the effects of these endotoxins, but they don't realize it. They induce NOS and OS that produce fatigue, stimulate TNF-a and pro-inflammatory cytokines, cause irritability of muscle tissue, etc.
So, it sounds like you have some lymphatic pain or soreness in your groin/hip area. I experience soreness, which I assume relates to the inflammatory nature of the endotoxins, and pain caused by swelling when the propulsion of the lymphatic fluid slows down. Over time I have learned that if I experience painful lymph swelling in a node (I can't see swelling, I can only feel this) I have to put on the brakes and stop stimulating the immune response. That is, I am slowing down the displacement of pathogens. The pattern that I established is that when I use Bifidobacteria at sufficient concentrations (& the right strains), which colonizes the large intestine, I experience more prominent lymphatic symptoms in my lower extremities. The femoral and inguinal vessels which pass through the anterior thigh and groin are clearly effected, but I seem to experience more pain in my legs and feet. Conversely, when I take LAB, the lymphatic involvement more prominently involves the nodes along the outside of the rib cage up to the axilla. When you visualize the lymphatic network you can see how the distribution of vessels would be effected depending upon the segment of the GI tract that is involved. Stagnation resultant from small bowel lymphatic engagement would more directly effect those vessels in the trunk versus the distally located large intestines, which influences the groin, thighs, legs, etc, because if the propulsion adjacent to the lower intestine slows down, so does everything below it.
Some of the more reliable indicators of lymphatic involvement mediated by endotoxins are pain in the lymph node behind the knee and the node in the grove between the distal tibia/fibula (this is ST36 in accupuncture and is perhaps one of the most important accupressure points in Chinese Medicine). Also, sore spots along the left and right sides of the spinal column, and most acutely, soreness adjacent to the spine, on the left side just under the shoulder blade.