Final answer:
Kidney stones are the most common type of obstruction of the upper urinary tract, causing pain and discomfort as they pass through. Benign prostatic hyperplasia is also a significant condition that affects the lower urinary tract, leading to urinary difficulties in men as they age.
Step-by-step explanation:
The most common type of obstruction of the upper urinary tract is caused by kidney stones. Kidney stones are hard mineral deposits that can form within the kidney and travel through the urinary system. These stones can range in size and may cause significant discomfort or pain as they pass through the urinary tract. Kidney stones are responsible for blocking the flow of urine and can be quite painful when they move or cause a blockage.
Another notable cause, though typically associated with lower urinary tract symptoms, is benign prostatic hyperplasia (BPH). BPH is the abnormal growth of the prostate gland which can constrict the urethra. Approximately 40 percent of men by age 60 and as many as 80 percent by age 80 are affected by BPH, which can lead to difficulty in urination due to the pressure exerted on the urethra.