A swollen, painful right testicle has several possible causes, ranging from infections that need antibiotics to testicular torsion, which requires emergency surgery within hours. The side doesn’t matter much diagnostically, as most conditions can affect either testicle. What matters far more is how quickly the pain started, how severe it is, and whether you have other symptoms like nausea, fever, or trouble urinating.
Testicular Torsion: The Emergency to Rule Out First
Testicular torsion happens when the testicle twists on the spermatic cord, cutting off its blood supply. It causes sudden, severe pain that typically comes on without warning. If the blood supply isn’t restored surgically, the testicle dies. This is the most time-sensitive possibility, and it’s why sudden testicular pain warrants an emergency room visit.
The numbers here are stark. When surgery happens within the first 6 hours, the testicle is saved about 97% of the time. By 7 to 12 hours, that drops to 79%. Between 13 and 24 hours, survival falls to 54%. Beyond 48 hours, only about 7% of testicles can be saved. A systematic review of over 1,200 patients confirmed this steep decline, which is why urologists treat torsion as a true surgical emergency.
Torsion is most common in adolescents and young men, but it can happen at any age. The hallmarks are sudden onset of severe pain, swelling, and sometimes a testicle that sits higher than normal or at an unusual angle. Nausea and vomiting are strong clues. In one study of 101 scrotal explorations, nearly all patients who had nausea, vomiting, or abdominal pain alongside scrotal pain turned out to have torsion rather than an infection. Only one patient with vomiting had a non-torsion diagnosis.
Epididymitis and Orchitis: Infection-Related Swelling
Epididymitis, an infection or inflammation of the coiled tube behind the testicle, is the most common cause of testicular pain in adult men. The pain tends to build gradually over days rather than striking all at once. You’ll typically feel tenderness toward the back of the testicle that may spread to the entire testicle over time. Swelling, warmth, and sometimes a small fluid collection around the testicle are common. When the infection spreads to the testicle itself, it’s called epididymo-orchitis.
The cause depends largely on your age and sexual activity. In sexually active men under 35, the infection is most often caused by sexually transmitted bacteria like chlamydia or gonorrhea. In older men, the culprit is more commonly a urinary tract organism, particularly in those with prostate enlargement or other bladder issues. Fever, burning with urination, and discharge are supporting signs that point toward infection rather than torsion.
The distinction between torsion and epididymitis is one of the most important calls in emergency medicine, and no single physical exam finding can make it reliably. The Prehn sign, where lifting the testicle relieves pain, has traditionally been taught as a way to identify epididymitis versus torsion. But research shows it’s unreliable. In one study, a third of patients with confirmed torsion had a positive Prehn sign. Imaging with ultrasound helps but isn’t perfect either, with sensitivity for torsion reported between 60% and 75% depending on the equipment used. This is why doctors often take patients to surgery if torsion can’t be confidently ruled out.
Varicocele and Hydrocele
A varicocele is a cluster of enlarged veins within the scrotum, similar to varicose veins in the leg. It often feels like a “bag of worms” above or behind the testicle and tends to be more noticeable when standing. Varicoceles are more common on the left side but can occur on the right. They typically cause a dull ache or heaviness rather than sharp pain, and the discomfort often worsens after prolonged standing or physical activity. Most varicoceles don’t need treatment unless they’re causing significant pain or fertility problems.
A hydrocele is a collection of fluid around the testicle that causes painless or mildly uncomfortable swelling. The scrotum may look larger than normal and feel heavy. A doctor can often identify a hydrocele by shining a light through the scrotum: fluid lets light pass through, while solid masses do not. Hydroceles are common, often harmless, and sometimes resolve on their own.
Trauma and Injury
A direct blow to the testicle from sports, an accident, or any impact can cause bruising, swelling, and significant pain. Most minor injuries heal on their own with rest, ice, supportive underwear, and over-the-counter pain relief. The concern is testicular rupture, where the tough outer covering of the testicle (the tunica albuginea) tears and testicular tissue pushes through.
Rupture requires surgery. When operated on within 72 hours, the testicle can be saved 80 to 90% of the time. Delays beyond that window drop the salvage rate to 45 to 55%, and the chance of losing the testicle entirely rises significantly. If you’ve had a testicular injury and the pain isn’t improving, or the swelling keeps getting worse, that warrants urgent evaluation with an ultrasound.
Inguinal Hernia
Sometimes what feels like testicular swelling is actually caused by an inguinal hernia, where a loop of intestine pushes through a weak spot in the abdominal wall and descends into the scrotum. The key difference is that hernia-related swelling tends to worsen with coughing, straining, bending over, or lifting heavy objects. You may notice a bulge in your groin that becomes more prominent when standing and disappears when lying down. The pain is typically more of a pressure or aching sensation rather than the sharp, localized pain of torsion or infection.
Testicular Cancer
Testicular cancer most commonly presents as a painless, hard lump on or within the testicle. However, about 13% of men with testicular cancer do experience pain as a presenting symptom, so pain alone doesn’t rule it out. A study of nearly 1,400 testicular cancer cases found that testicular pain had a positive predictive value of only 0.4%, meaning the vast majority of men with testicular pain don’t have cancer. Still, any hard lump or mass that doesn’t go away within a couple of weeks deserves an ultrasound.
Testicular cancer is most common in men between 15 and 45. It’s one of the most treatable cancers even when caught at later stages, but earlier detection makes treatment simpler.
How to Tell What’s Urgent
The single most important factor is how the pain started. Sudden, severe pain that came on within minutes strongly suggests torsion, and you should go to an emergency room immediately. Gradual pain that’s been building over a day or more, especially with fever or urinary symptoms, points more toward infection.
Certain combinations of symptoms are particularly telling. Nausea or vomiting with testicular pain is strongly associated with torsion. In one surgical study, abdominal pain alongside scrotal pain was almost exclusively seen in torsion cases, not infections. Fever, painful urination, and a gradual onset all lean toward epididymitis.
Swelling that comes and goes with physical activity, especially with a visible groin bulge, suggests a hernia. A painless, firm lump that you notice in the shower and doesn’t change with position raises concern for cancer. Dull achiness that worsens throughout the day and feels like a heavy bag may be a varicocele.
No self-exam or symptom checklist replaces a proper evaluation. Ultrasound is the standard imaging tool for sorting out scrotal swelling, and it’s quick, painless, and widely available. If your pain is severe, sudden, or accompanied by nausea, treat it as an emergency. The difference between a saved and lost testicle often comes down to a few hours.