What is the most commonly observed sign of prostatic hypertrophy?

The most commonly observed sign of prostatic hypertrophy, or benign prostatic hyperplasia (BPH), is difficulty in starting to urinate. As the prostate gland enlarges, it can press against the urethra, leading to a variety of urinary symptoms. This compression often causes a weak urine stream and difficulty initiating urination. Patients frequently experience a sense of urgency and may struggle with delay in the starting of the urine flow.

Frequent urination at night is also a symptom associated with BPH, known as nocturia, but it is not as primary or defining as the difficulty in initiating urination. Blood in urine can indicate more severe complications or other conditions such as infections or prostate cancer but is not commonly associated directly with benign prostatic hypertrophy. Increased libido is unrelated to BPH; rather, sexual function can be affected by the condition in various ways, but it is not a primary symptom. Hence, the correct answer highlights a key characteristic directly related to the physical changes wrought by prostatic hypertrophy.