Mono is a typical cause in that age group, but you should contact your health care provider for information specific to your son's situation.
I am an anesthesiologist, so I do not possess a subspecialist's knowledge of either the kidney or the spleen. However, based on the medical knowledge I do have, I would say that it would be highly unlikely that a kidney infection would result in an enlarged spleen.
Lungs, heart, liver, pancreas, gall bladder...
Normal is around 4" or 8cm give or take a bit. Abnormal or enlarged is 6" plus.
Answer... The liver and spleen are part of the PORTAL system. It appears that you have some degree of liver failure [because you are undergoing liver/spleen dialysis]. The PORTAL system is a separate blood system for the digestive-related organs. You apparently are being treated for kidney failure as well. Did you get into some sort of toxic chemical? Another cause of liver failure is chronic alcohol abuse.
If your spleen hurts, you need to go see your doctor as soon as you can. There are a few diseases that can cause your spleen to become painful, and you need to get it checked out. Some of these diseases are very serious.
That might explain her stomach, but what would explain the reason for the enlarged rear end?
That would take some pretty violent throwing up, one symptom of mono is an enlarged spleen and at that time the spleen could rupture or tear just from the swelling caused by infection. Normally a ruptured spleen is caused by blunt force trauma, the type you would be susceptible to from a blow, contact sports or a car accident. Pain in the upper left abdomen after injury, with local tenderness to touch and mental confusion should be treated as an emergency.
If the condition is harmful to your health, then a splenectomy would be performed. Either laparoscopically ( through small incisions and using a camera, also known as minimally invasive ), or open.
http://www.tigerhomes.org/animal/spleen-intestines.cfm
It can, but the person would have to have regular medical checks. The spleen usually is removed because it has ruptured, and it is a life saving procedure. If the spleen is removed due to the above its functions can be taken over by the liver and the red bone marrow so blood can still be stored and filtered.
The right kidney sits under the liver, the largest internal organ. So it's lower down (2-8cm lower) than the left kidney which is under the spleen, a much smaller organ. The tops of the spleen and liver are pretty much in line due to the diaphragm, which is why where their lower borders are makes such a difference.
IF, and I mean IF I'm not mistaken, I think that that would have to be your liver. I'm not one hundered percent sure, but 10th grade Biology gets you somewhere.