U is for unshaven. I do not see a point in doing this unless the patient needs minimal grafts (less than 500). Otherwise, if you are looking for a hair transplant surgery, it's a surgery. It's going to show for a few days, it will take some time to heal, and it will be noticeable to other people for a few days. In the unshaven technique, you severely restrict the donor zone and cannot harvest the amount of grafts necessary in most cases.
U-FUE stands for Unshaven or Undetectable FUE, where hair is not shaved during the surgery. In the traditional FUE, all hair must be shaved to facilitate extraction and placement of grafts since most of the hair transplant surgery equipment only works with shaven hair. In U-FUE, only the grafts to be extracted are cut and extracted, while the rest of the untouched hair remains intact. Also in the recipient area, recipient sites are made within the existing hair. When healing, scabs and redness can be hidden by the existing hair. This helps make the surgery undetectable since the rest of the hair can cover the traces of the surgery from being noticed. The disadvantages are time, cost and less grafts transplanted. The work load involved in this surgery is more, so it will be more expensive and less grafts can be extracted.
The U most likely stands for 'unshaven'. Traditional FUE is performed with the donor area shaved to have access to the maximum number of hairs possible to harvest. Some doctors promote 'unshaven' FUE to attract people unwilling to shave.
however, FUE without shaving will limit the number of grafts or hairs accessible which in turn limits the result achievable. Alternatively it may take more operations to achieve sufficient numbers if your hair loss requires significant replacement if hairs. This will logically increase ultimate cost as well.
"U" may mean undetectable or unshaven (completely). You still have to shave your head for FUE but the shaved portion is minimal and the shaved portion is covered by the longer surrounding hair. The VIDEO below shows the U-FUE.
I look this up on the internet and it seems that U FUE is done without shaving the donor area as is typically done with FUE. My group has done what we called long-hair FUE where we don't shave the head. This is a tedeous process and less accurate than when you can see the cut ends of the donor hairs so more transection happens with long hair FUE.