Scrotal swelling refers to any enlargement, mass, lump, or noticeable discomfort within the pouch of skin that contains the testicles. This physical change represents a wide spectrum of underlying conditions, ranging from common, relatively minor fluid collections to sudden, time-sensitive medical emergencies. Because the scrotum houses the testicles, any new or persistent swelling requires professional evaluation. Understanding the different categories of causes is important for recognizing potential urgency, but self-diagnosis should never replace consultation with a healthcare provider.
Structural Causes Related to Fluid and Blood Flow
Many instances of scrotal enlargement result from mechanical or structural issues involving the movement of fluid, blood, or tissue.
Hydrocele
A hydrocele is a collection of serous fluid that accumulates in the thin sheath surrounding the testicle, often presenting as a smooth, painless, and sometimes sizable swelling. This fluid buildup occurs either because the body produces too much fluid or because the drainage system is unable to absorb it efficiently. In infants, a hydrocele can be communicating, meaning a small channel from the abdomen remains open, allowing fluid to pass into the scrotum, though this often closes naturally.
Varicocele
Another common structural cause is a varicocele, which involves the abnormal dilation and enlargement of the pampiniform venous plexus, a network of veins that drain blood from the testicle. This condition is caused by a backup of venous blood flow, often due to faulty valves. A large varicocele is sometimes described as feeling like a “bag of worms” above the testicle and may cause a dull ache or feeling of heaviness. Varicoceles occur more frequently on the left side due to the anatomical angle at which the left testicular vein connects to the renal vein.
Inguinal Hernia
Inguinal hernias contribute to scrotal swelling when a section of the intestine or fatty tissue pushes through a weak spot in the abdominal wall. This tissue then descends along the spermatic cord, creating a bulge that can fluctuate in size. The swelling may become more noticeable when a person coughs, strains, or stands up, and it can cause associated discomfort or pain in the groin area.
Swelling Caused by Infection and Inflammation
Inflammation due to infection is a frequent cause of scrotal swelling, typically accompanied by other signs of the body’s immune response.
Epididymitis
Epididymitis is the inflammation of the epididymis, the coiled tube located at the back of the testicle that stores and transports sperm. This condition is most often caused by a bacterial infection, which can travel backward from the urinary tract or be a result of sexually transmitted infections like chlamydia or gonorrhea. The infection causes localized swelling and tenderness that usually develops gradually over hours or days. Symptoms often include warmth and redness of the scrotum, pain upon urination, or a penile discharge.
Orchitis
Orchitis is the inflammation of the testicle itself and can occur simultaneously with epididymitis, a combined condition called epididymo-orchitis. Orchitis is less common than epididymitis and is sometimes caused by a viral infection, such as the mumps virus, particularly in males who contract mumps after puberty. Both conditions involve a localized inflammatory process that can lead to fever and a general feeling of illness.
Acute Conditions Requiring Emergency Care
Certain causes of scrotal swelling represent time-sensitive emergencies that necessitate immediate medical attention to prevent permanent damage.
Testicular Torsion
Testicular torsion occurs when the spermatic cord—which contains the blood vessels supplying the testicle—twists upon itself. This twisting immediately cuts off the blood supply, leading to rapid tissue death if not corrected quickly, ideally within six hours of symptom onset. The primary symptom is the sudden onset of severe, excruciating pain in one testicle, often waking the patient from sleep. The affected testicle may appear higher than the other due to the cord shortening, and the pain is frequently accompanied by nausea and vomiting.
Trauma and Strangulation
Trauma, such as a direct blunt force injury to the groin, can cause rapid swelling through the formation of a hematoma, which is a collection of blood outside the blood vessels. A complication of an inguinal hernia known as a strangulated hernia is also an emergency. This occurs if the trapped segment of intestine loses its blood supply, resulting in a sudden worsening of pain, fever, and a change in the color of the bulge.
Identifying Malignancy and When to See a Doctor
While less common than other causes, malignancy must be considered, as testicular cancer often presents differently than inflammatory or mechanical issues. Testicular cancer typically manifests as a firm, painless lump or a general enlargement of one testicle that cannot be separated from the testicle itself. Patients may notice a feeling of heaviness or a dull ache in the lower abdomen or groin, but acute, severe pain is usually not the primary symptom.
Swelling can also be a manifestation of systemic conditions, rather than a problem originating in the scrotum itself. Generalized edema, or total body fluid retention, caused by conditions like congestive heart failure or kidney failure, can result in fluid accumulating in the dependent areas of the body, including the scrotum.
Given the wide range of causes, any new or persistent scrotal swelling should prompt a medical consultation. Red flags that require immediate emergency evaluation include the sudden, severe onset of pain, a rapid change in scrotal color, or swelling accompanied by fever, nausea, or vomiting. A healthcare provider will perform a physical examination and may use imaging tools like ultrasound to accurately assess blood flow and determine the exact cause of the swelling.