1. The sudden, rhythmic waves of pain probably is a colic pain. Colic pain happens because of obstruction in moving organs like intestine or the urinary tract. Pain from urinary tract will be felt in the groin area. Obstruction also decreases the urine output.
From this information, you can conclude that the condition is bruce suffering urinary tract obstruction. More specific diagnosis would be urolithiasis because a stone is the most probable cause.
2. how is it treated?
Urinary tract obstruction can be treated by introducing catheter. If the obstruction is caused by a stone, you can break the stone with various modality based on the stone size. Imaging test would be needed to confirm it beforehand.
3. how can he prevent future episodes?
Kidney stone formed because the urine is saturated that cause some of the substance to make sediment. It can be prevented by increasing urine volume by drink more water. If there is more water in the urine, it won't be saturated easily, thus the risk of forming stone is decreased.