I'm not a medical person, but I'll try to translate the terms I do understand.
1. "poorly differentiated squamous cell..." this means that the cells that are being made/found in his lungs don't look right and/or don't have the distinctive characteristics that squamous cells in the lung usually have. [A squamous cell is one of three basic types of cells, it's generally flat-looking. The lungs and quite a few other organs have squamous cells.]
2- "Large cell undifferentiated ...colon" - this is pretty similar to . The key word is 'undifferentiated'; large cell refers to a sub-type of this type of colon cancer or carcinoma.
3- "History of esophogeal cancer with re-section and pull through 1998" - Sounds as though this is where it all began - in the esophagus. To get rid of this cancer, your brother's doctors removed the cancerous part [resection] and re-attached the unaffected parts.
Some information about how tissues and cancers:
a- The esophagus, like the colon and lungs has squamous cells.
b- Cancers mostly spread through the blood and/or the lymphatic system.
c- Cancers tend to spread to similar cells - from one squamous cell tissue to another squamous cell tissue.
Because of all of the above, the lungs are often one of the organs affected by the time a cancer has reached Stage 3 or Stage 4 esp. if the cancer started in a similar cell type.
4- "Left hydromephrosis ..." - Sometime during yor brother's therapy, the crown/cup-shaped portion inside his kidneys that helps urine drain from the kidneys into the urethra got blocked or stopped working for some reason. Because it's vital to get rid of the urea [urine] in the blood, the doctors performed a type of bypass [mephrostomy tube] from the functioning part of the kidneys where the urine accumulates to: a) the urethra; b) directly to the bladder; or c) into an external collection bag.
Hope this helps,
P.S. Other Posters - If anyone spots any technical errors, pls feel free to make corrections.