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Pelvis » Scrotum And Testicles
Uncomplicated acute epididymo-orchitis
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Presentation A 25-year-old male, presents with a 1-day history of acute left-sided scrotal pain. He has no history of trauma.
Caption: Transverse view comparing right and left testes.
Description: Transverse sonogram of scrotum, demonstrating an enlarged, and slightly less echogenic left testis as compared to the contralateral side.
Caption: Sagittal view of the left testis.
Description: Sagittal sonogram, depicting an enlarged [5.2x3.0x3.2 cms], and slightly heterogeneous left testis.
Caption: Transverse sonogram of left scrotum.
Description: Transverse sonogram revealing an enlarged [1.4x1.1x2.2 cms] and heterogeneous epididymis.
Caption: Color Doppler study of left scrotum.
Description: Color Doppler study, showing markedly increased flow throughout the left testis and epididymis.
Caption: Power Doppler study of left scrotum.
Description: Power Doppler study revealing markedly increased flow throughout the testis and epididymis on the affected side.
Caption: Transverse color Doppler study.
Description: Transverse view, comparing the color flow through both testes. The affected side shows obvious increase in flow, compared to the normal right testis.
Differential Diagnosis Acute uncomplicated epididymo-orchitis
Final Diagnosis Acute uncomplicated epididymo-orchitis
Discussion Although the scrotum is a superficial structure, clinical examination is frequently not enough for making a specific diagnosis. The differential diagnosis in a patient presenting with acute scrotal pain may pose a diagnostic dilemma, and ultrasound can play a key role in effectively narrowing down the differentials and distinguishing acute epididymitis, acute epididymo-orchitis and testicular torsion.

Epididymo-orchitis can occur with Neisseria and Chlamydial infections, which are sexually transmitted and can also occur with E.coli or Pseudomonas. The epididymis is the organ initially more severely affected in epididymo-orchitis, with testicular involvement occurring in about half the cases due to contiguous spread. Systemic infections and trauma are uncommon causes of acute epididymo-orchitis. Primary orchitis occurs very rarely and may be due to viral infections such as mumps, where it can present with bilateral testicular swelling.

Gray scale imaging depicts an enlarged epididymis and testis. Secondary findings such as scrotal wall thickening or pyocele may be seen. With epididymitis, the epididymis may be significantly enlarged and shows altered echotexture, usually hypoechoic, but may sometimes be hyperechoic. With testicular involvement, change in the echogenicity is also noted, with the testis usually becoming hypoechoic. Testicular edema in a rigid tunica albuginea is responsible for a heterogeneous appearance. The testicular involvement may be diffuse or focal; if the latter it may present as patchy hypoechoic lesions in the testis. This appearance of testicular involvement is non- specific, and if the acute clinical scenario is not present, it needs to be differentiated from neoplastic conditions involving the testis such as leukemia and lymphoma.

Increased blood flow throughout the affected testis and epididymis is an established criterion for the diagnosis of epididymo-orchitis. The sensitivity of color Doppler in diagnosing inflammation is almost 100%. In acute epididymitis, the epididymis demonstrates an increased number of vessels, which show low resistance and high velocity flow. Studies have shown that in 20% of cases of epididymitis and 40% of cases of orchitis, only the color Doppler findings are abnormal with normal gray-scale ultrasound findings. Therefore, in all cases of suspected epididymo-orchitis, it is important to image the scrotum in both gray scale and color Doppler mode.

The aim of ultrasonography in a patient presenting with an acute painful scrotum is to rule out testicular torsion from acute epidiymo-orchitis, as the former needs emergent surgery to prevent permanent damage. Gray scale findings may be completely normal in the early stages of torsion; however, the absence of color flow on Doppler favors the diagnosis of testicular torsion. Findings of hyperemia in the epididymis and testis are diagnostic for inflammatory pathology. Ultrasound also helps in detecting the complications of acute epididymo-orchitis which includes:
1. Progression to chronic stage
2. Abscess formation [click here to view]
3. Infarction [click here to view]
4. Pyocele
5. Infertility and
6. Atrophy
Case References 1. Hawtrey CE. Assessment of acute scrotal symptoms and findings. A clinician`s dilemma. Urol Clin North Am 1998 Nov; 25(4): 715-23.
2. Dogra VS, Gottlieb RH, Oka M, Rubens DJ. Sonography of the scrotum. Radiology. 2003 Apr; 227(1): 18-36. Epub 2003 Feb 28.
3. WG Horstman, WD Middleton, GL Melson and BA Siegel. Color Doppler US of the scrotum. RadioGraphics.1991 Vol 11, 941-957.
4. Pavlica P, Barozzi L. Imaging of the acute scrotum. Eur Radiol. 2001; 11(2): 220-8.
5. Ralls PW, Jensen MC, Lee KP, Mayekawa DS, et al. Color Doppler sonography in acute epididymitis and orchitis. J Clin Ultrasound. 1990 Jun; 18(5): 383-6.
Follow Up The patient responded well to antibiotic treatment, and subsequent ultrasound imaging showed complete resolution.
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