Last revised by Jeremy Jones on 6 Apr 2023

Epididymitis refers to inflammation of the epididymis and may be associated with inflammation extending to the testis, in which case the term epididymo-orchitis is used. This should be distinguished from isolated orchitis, which is, by comparison, much less common. 

Epididymitis is most prevalent in those under the age of two and over the age of six.

The clinical spectrum ranges from mild tenderness to a severe febrile process with acute unilateral scrotal pain. 

The infection usually originates in the bladder or prostate gland, spreads through the ductus deferens and the lymphatics of the spermatic cord to the epididymis, and finally reaches the testis, causing epididymo-orchitis. Due to this progression, infection starts in the tail of the epididymis.

The epididymal tail is the most affected region, and reactive hydrocele and scrotal wall thickening are frequently present. As the infection spreads, it can ascend the body and later the head of the epididymis.

Increased size and, depending on the time of evolution, decreased, increased, or heterogeneous echogenicity of the affected organ are usually observed.

The inflammation produces increased blood flow within the epididymis, testis, or both. Pulsed wave Doppler interrogation yielding an epididymal peak systolic velocity (PSV) greater than 15 cm/sec is highly suggestive of epididymitis, especially when the PSV on the affected side is significantly higher than the unaffected (with a ratio >1.7) 4.

Analysis of the epididymal waveform may reveal a low-resistance pattern as compared with the normal pattern. In epididymitis, a resistive index (RI) <0.5 is frequently present 5.

Pertechnetate scintigraphy can be used in evaluating acute scrotum. Increased perfusion and uptake of the scrotal contents are characteristic of epididymo-orchitis. In isolated epididymitis increased curvilinear activity is seen laterally, corresponding to the inflamed epididymis. 

The vast majority of patients are managed with simple analgesia and oral antibiotics.

Complications of epididymo-orchitis include:

Differential considerations include

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Cases and figures

  • Case 1
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  • Case 2: with epididymal abscess formation
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  • Case 3
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  •  Case 4
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  • Case 5: on right side
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  • Case 6
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  • Case 7
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  • Case 8
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  • Case 9: tuberculous epididymo-orchitis
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  • Case 10: complicated with testicular infarction
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