How can a big left sided varicocele(grade 3) increase pressure to right renal vein and cause some pain in right testis? (anatomical question)

Nutcracker phenomena: Pressure to the renal Vien upon being erect causes compression by the varicolcele.

Varicocele: The varicocele can cause pain in the testis. Increased pressure in the renal vein can cause a varicocele,not the other way around.

Unlikely: Varicoceles are common in adolescents 7-15 %. 95% occur on the left side only. This condition is usually without symptoms of discomfort. A grade 3 varicocele may be considered for repair as they can lead to low sperm counts and infertility. If your symptoms are on the right side you should see a PCP or urologist to assess further