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Comparison of Tuberculous and Pyogenic Epididymal Abscesses

Clinical, Gray-Scale Sonographic, and Color Doppler Sonographic Features

¹ Department of Radiology, Gachon Medical College, Gil Medical Center, 1198, Guwol-Dong, Namdong-Gu, Inchon, 405-760, South Korea.
² Department of Urology, Gachon Medical College Gil Medical Center, Inchon, 405-760, South Korea.
³ Department of Preventive Medicine, Gachon Medical College, Gil Medical Center, Inchon, 405-760, South Korea.

Received December 15, 2000; accepted after revision May 29, 2001.

 
Address correspondence to D. M. Yang.

Abstract

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OBJECTIVE. The purpose of this study was to evaluate the capability of clinical, gray-scale sonographic, and color Doppler sonographic features for differentiating tuberculous and pyogenic epididymal abscesses.

MATERIALS AND METHODS. Retrospective analysis was performed in 10 cases of tuberculous epididymal abscess and in 13 cases of pyogenic epididymal abscess. The following clinical, gray-scale sonographic, and color Doppler sonographic features were analyzed: patient's age; duration of symptoms; scrotal tenderness; presence of sinus tract; concurrent tuberculosis in other organs; location, size, and echogenicity of the abscess; hyperechoic rim; testicular involvement; hydrocele; and blood flow in the epididymal lesion.

RESULTS. Tuberculous epididymal abscess had a longer duration of symptoms (p = 0.0001) and a lower frequency of scrotal tenderness (p = 0.0048) than pyogenic epididymal abscess. The size of the abscess was larger in tuberculous epididymal abscess than in pyogenic epididymal abscess (p = 0.0002). The degree of blood flow in the peripheral portion of the abscess was lower in tuberculous epididymal abscess (p = 0.001). The patient's age, location and echogeninicity of the abscess, presence of sinus tract, hyperechoic rim, testicular involvement, and hydrocele did not differ between the tuberculous and pyogenic epididymal abscesses.

CONCLUSION. Some clinical findings, gray-scale sonography, and color Doppler sonography were useful in differentiating tuberculous epididymal abscess from pyogenic epididymal abscess. The presence of long-term scrotal swelling without tenderness and a lower degree of blood flow in the peripheral portion of a large abscess are suggestive of tuberculous epididymal abscess.

Introduction

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Epididymitis is a common intrascrotal inflammatory disease that usually results from retrograde spread of urethral pathogens via the ejaculatory ducts and the vas deferens [1]. Neisseria gonorrhoeae, Chlamydia trachomatis, Escherichia coli, and Proteus mirabilis are common pathogens [2]. Epididymal abscesses are an uncommon complication of epididymitis [1] and may develop when epididymitis is severe or goes untreated [3]. Tuberculous epididymitis is caused by Mycobacterium tuberculosis and can occur not only from retrograde spread from the prostate and seminal vesicles but also from hematogenous dissemination [4]. Pathologically, the characteristic finding of tuberculous epididymitis is caseating granuloma, which may form the abscess cavity and contain yellow—green caseous materials [5, 6].

Although antituberculous chemotherapy must be the initial course of action in tuberculous epididymitis, surgery is required when an intrascrotal abscess is identified because this condition does not respond to antituberculous chemotherapy [6,7,8]. In contrast, pyogenic epididymal abscess usually responds to antibiotic therapy [9]. Therefore, the differentiation of tuberculous epididymal abscess and pyogenic epididymal abscess is important in determining the appropriate treatment.

Most reports describing the sonographic findings of pyogenic epididymal abscess [1,2,3, 10, 11] are limited to a small number of cases, and the clinical and sonographic findings of epididymal abscess have not been sufficiently analyzed. Furthermore, to our knowledge, the differentiation of tuberculous and pyogenic epididymal abscesses has not been described.

We undertook a retrospective review of the gray-scale and color Doppler sonographic findings and medical charts of nine patients with tuberculous epididymal abscess and 13 patients with pyogenic epididymal abscess in an attempt to compare clinical, gray-scale sonographic, and color Doppler sonographic findings in the two diseases.

Materials and Methods

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From May 1998 to August 2000, 340 scrotal sonographic examinations were performed at our institution. Of these, 10 cases of tuberculous epididymal abscess in nine patients and 13 cases of pyogenic epididymal abscess in 13 patients were studied retrospectively. One patient with tuberculous epididymal abscess showed bilateral involvement. All cases of tuberculous epididymal abscess were confirmed pathologically by epididymectomy in four cases and epididymoorchiectomy in six. Pyogenic epididymal abscesses were diagnosed by epididymoorchiectomy (n = 1), percutaneous needle aspiration (n = 3), or clinical improvement after antibiotic therapy (n = 9). In the case of tuberculous epididymal abscess, the abscess cavity was noted to contain pus on the cut surface, and granulomas with caseation necrosis were observed on microscopic examination. In the case of pyogenic epididymal abscess, abscess with fibrous capsule was identified at microscopy, and Gram's and acid-fast bacillus stains and cultures were negative for pus.

All sonographic procedures were performed with a 5- to 10-MHz linear array transducer (HDI 3000; Advanced Technology Laboratory, Bothell, WA) or an 8- to 15-MHz linear array transducer (Sequoia; Acuson, Mountain View, CA). Color Doppler and power Doppler studies were performed with optimized color Doppler parameters. The power level, threshold, persistence, and wall filter were individually adjusted to maximize the detection of blood flow through the field of view.

We reviewed the clinical charts of 22 patients and recorded each patient's age, duration of symptoms, complaints of scrotal tenderness, presence of sinus tract to the scrotal skin, and concurrent tuberculosis in other organs. The location of the epididymal abscess was determined by gross pathologic findings in 11 cases and sonographic findings in the 12 remaining cases.

To compare the distribution of the anatomic location of the epididymal abscess between the tuberculous and pyogenic epididymal abscesses, the location of the epididymal abscess was categorized as head, body, or tail. Of the 23 cases in 22 patients, one case of tuberculous epididymal abscess (head and body) and two cases of pyogenic epididymal abscess (head and tail) showed two separate lesions. In two patients with tuberculous epididymal abscess involving the entire epididymis, we considered the disease as involving the head, body, and tail individually. Therefore, the number of tuberculous epididymal abscess cases totaled 15 and pyogenic epididymal abscess cases, 15; five lesions were found in the head, three in the body, and seven in the tail in tuberculous epididymal abscess and two in the head and 13 in the tail in pyogenic epididymal abscess.

The gray-scale sonographic and color Doppler sonographic images were interpreted by consensus of two radiologists who measured the size of the epididymal abscess and determined its echogenicity, hyperechoic rim, testicular involvement, hydrocele, and degree of blood flow in the peripheral portion of the abscess. In one case of tuberculous epididymal abscess and two cases of pyogenic epididymal abscess, two lesions were seen. In diffuse involvement of epididymis in two cases of tuberculous epididymal abscess, we considered this to be a single lesion. The measurement of the abscess was performed with an axial scan. We analyzed 11 lesions in tuberculous epididymal abscess and 15 in pyogenic epididymal abscess using gray-scale sonography and color Doppler sonography. The grade of vascularity was classified using a three-point scale: 1, a few spotty signals in the peripheral portion of the abscess; 2, moderate signals in the peripheral portion of the abscess; and 3, marked signals in the peripheral portion of the abscess.

We performed a statistical analysis to compare the tuberculous epididymal abscess with pyogenic epididymal abscess using the Wilcoxon's rank sum test, Fisher's exact test, and chi-square test for trend. Probability values less than 0.05 were considered statistically significant. The data were analyzed using a statistical software package (SAS Institute, Cary, NC).

Results

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The comparison of clinical parameters of tuberculous and pyogenic epididymal abscesses is shown in Table 1. The age of the patients ranged from 22 to 81 years (mean, 48 years) in pyogenic epididymal abscess and from 20 to 76 years (mean, 46 years) in tuberculous epididymal abscess (p = 0.789, Wilcoxon's rank sum test). The duration of symptoms ranged from 3 to 9 days (mean, 5 days) in pyogenic epididymal abscess and from 15 to 150 days (mean, 73 days) in tuberculous epididymal abscess (p = 0.0001, Wilcoxon's rank sum test). The presenting symptom was a painful scrotal swelling in all cases of pyogenic epididymal abscess (n = 13) and a scrotal swelling with tenderness (n = 4) or without tenderness (n = 5) in tuberculous epididymal abscess (p = 0.0048, Fisher's exact test). The pus discharge from the draining sinus was seen in two cases of tuberculous epididymal abscess. In the case of pyogenic epididymal abscess, the sinus tract was not found along the scrotum. However, no statistically significant difference was noted between tuberculous and pyogenic epididymal abscesses in terms of the presence or absence of the sinus tract (p = 0.156, Fisher's exact test). In the case of tuberculous epididymal abscess, concomitant renal tuberculosis was seen in one patient and inactive pulmonary tuberculosis in four patients.

The tail of the epididymis was the most commonly involved location in both tuberculous and pyogenic epididymal abscesses. Seven of 15 lesions were found in the tail in tuberculous epididymal abscess and 13 of 15 lesions in pyogenic epididymal abscess. In addition, the anatomic location of the epididymal abscess was not statistically significant in distinguishing tuberculous epididymal abscess from pyogenic epididymal abscess (p = 0.067, Fisher's exact test).

The comparison of gray-scale sonographic and color Doppler sonographic features of tuberculous and pyogenic epididymal abscesses is shown in Table 2. The size of the abscess was larger in tuberculous epididymal abscess than in pyogenic epididymal abscess (p = 0.0002, Wilcoxon's rank sum test) (Figs. 1,2,3,4). All lesions with tuberculous and pyogenic epididymal abscesses were heterogeneously hypoechoic (Figs. 1,2,3,4). No statistically significant difference was noted with respect to hyperechoic rim (p = 0.428, Fisher's exact test), testicular involvement (p = 0.604, Fisher's exact test), or hydrocele (p = 1.000, Fisher's exact test). The degree of blood flow in the peripheral portion of the abscess was lower in tuberculous epididymal abscess (p = 0.001, chi-square test for trend). A few spotty signals in the peripheral portion of the epididymal abscess were observed only in tuberculous epididymal abscess (Figs. 1 and 2), and a marked vascularity was observed only in pyogenic epididymal abscess (Fig. 3).

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1. —52-year-old man with tuberculous epididymal abscess and 4-month history of non-tender scrotal swelling. Longitudinal color Doppler sonogram shows large abscess measuring approximately 1.6 cm in diameter with heterogeneously low echogenicity in epididymal tail, with few spotty flow signals in peripheral portion of abscess (large arrows). Epididymal abscess is surrounded by hyperechoic rim (small arrows).

View larger version (137K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2. —63-year-old man with tuberculous epididymal abscess and 15-day history of painful scrotal swelling. Longitudinal power Doppler sonogram shows heterogeneously hypoechoic abscess measuring about 1.1 cm in epididymal body. Few flow signals are seen in peripheral portion of epididymal abscess (arrows). Note heterogeneous echogenicity with ill-defined hypoechoic areas and slightly increased flow signals in testis (T).

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3. —34-year-old man with pyogenic epididymal abscess and 3-day history of painful scrotal swelling. Longitudinal power Doppler sonogram shows heterogeneously hypoechoic abscess with peripheral hyperechoic rim in epididymal tail. Increased flow signals are seen in peripheral portion of abscess.

View larger version (146K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 4. —49-year-old man with pyogenic epididymal abscess and 4-day history of painful scrotal swelling. Longitudinal power Doppler sonogram shows small heterogeneously hypoechoic abscess measuring approximately 0.6 cm in diameter with peripheral hyperechoic rim (arrows) in epididymal tail. Moderate flow signals are seen in peripheral portion of abscess.

Discussion

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Epididymitis occurs most frequently by a retrograde or lymphatic route and more rarely by hematogenous spread. Histologically, pyogenic epididymitis is characterized by vascular congestion and interstitial edema associated with a mixed leukocyte infiltrate [12]. In severe cases, the epididymal tubules are sometimes completely destroyed by abscess formation, which involves a pooling of purulent material [12].

Urogenital tuberculosis is primarily a disease of adults, and approximately 30% of cases of extrapulmonary tuberculosis involve the urogenital tract [5]. The kidneys are often the primary site of urogenital tuberculosis. Tuberculous bacilli reach the epididymis by hematogenous spread, lymphatic route, or descent from the kidney [4, 5]. The pathologic findings of the tuberculous epididymitis are caseation necrosis, fibrosis, and granulation tissues [4]. Tuberculous epididymitis may have an abscess cavity that contains caseous materials [5, 6]. The presence of an abscess in the epididymis indicates advanced scrotal disease that does not respond to antituberculous chemotherapy [6, 7]. In the course of tuberculous epididymal abscess, walling off with fibrosis and calcification is a favorable outcome, whereas the formation of fistula is an unfavorable outcome [12].

In Korea, tuberculosis remains a serious public health problem, and tuberculous epididymitis is not rare [4, 6, 7]. Therefore, some problems are experienced in differentiating tuberculous epididymitis from pyogenic epididymitis when scrotal swelling is present. In the clinical findings, although fever, pyuria, swelling, redness, and tenderness of the scrotum are observed in pyogenic epididymitis [13], these findings may also be present in tuberculous epididymitis [14]. Gray-scale and color Doppler sonography may be useful in differentiating tuberculous epididymitis from pyogenic epididymitis [2, 4, 6]. However, when an abscess is formed in tuberculous epididymitis and pyogenic epididymitis, it becomes difficult to distinguish between the two diseases. The grayscale and color Doppler sonographic findings may be similar—both abscesses are heterogeneously hypoechoic on gray-scale sonography [4, 6, 10, 11, 13, 14], and an absence of blood flow in both is shown on color Doppler sonography [6, 9,10,11].

This study showed that the following statistically significant differences existed between tuberculous epididymal abscess and pyogenic epididymal abscess in some clinical, gray-scale sonographic, and color Doppler sonographic features: long duration of symptoms and absence of scrotal tenderness in tuberculous epididymal abscess on clinical features compared with pyogenic epididymal abscess; large size of tuberculous epididymal abscess on gray-scale sonography compared with pyogenic epididymal abscess; and a lower degree of blood flow in the peripheral portion of tuberculous epididymal abscess compared with pyogenic epididymal abscess on color Doppler sonography.

These clinical features are related to the differing course of the disease in tuberculous epididymal abscess and pyogenic epididymal abscess. Although tuberculous epididymitis may have an acute form, it usually presents as a chronic disease. In contrast, pyogenic epididymitis is an acute inflammatory condition, and abscesses may develop when epididymitis is severe. Therefore, in predicting the difference between tuberculous and pyogenic epididymal abscesses, the duration of symptoms is helpful in some instances. Tenderness in the scrotum is another valuable clinical feature that can help to distinguish tuberculous and pyogenic epididymal abscesses. In pyogenic epididymal abscess, scrotal tenderness was present in all cases, but it was recorded in less than half in tuberculous epididymal abscess (p = 0.0048). However, no differences were noted in age, presence of sinus tract, and location of the abscess in either the tuberculous epididymal abscess group or the pyogenic epididymal abscess group.

The characteristic gray-scale sonographic findings of tuberculous epididymal abscess were an enlarged epididymis and a heterogeneously decreased echotexture of the lesion [4,5,6]. Pyogenic epididymal abscess has been described in the literature as having a cystic, hypoechoic, or complex echogenicity [10, 11, 14]. Inflammatory cells, fibrosis, and pus may contribute to these findings [1]. In our study, all cases of tuberculous and pyogenic epididymal abscesses were heterogeneously hypoechoic. Thus, the echogenicity of the abscess is not useful in differentiating tuberculous epididymal abscess from pyogenic epididymal abscess. An interesting result of our study was the difference in abscess size between the two diseases. Tuberculous epididymal abscess is larger than pyogenic epididymal abscess. This result is related to the difference in the duration of the two diseases. Pyogenic epididymal abscess was usually detected before the formation of a large abscess because the patient was admitted early to the hospital as a result of scrotal tenderness. However, tuberculous epididymitis usually has a chronic course, and patients with tuberculous epididymitis were admitted after the formation of a large abscess presenting as a large indurated mass, which occurred because of its minimal tenderness. Another interesting gray-scale sonographic finding was a hyperechoic rim of the peripheral portion of the abscess. We believe this is revealed as an abscess wall. However, this finding does not contribute to the differentiation of tuberculous and pyogenic epididymal abscesses (p = 0.428). In addition, we observed no statistically significant differences between the two groups in testicular involvement and hydrocele.

In the case of tuberculous epididymitis, the involvement of tuberculosis in another organ is common [4, 7], and concomitant tuberculous infection in the genitourinary tract may be helpful in differentiating other causes of epididymitis [7]. In our study, the involvement of another organ was noted in 56% of patients with tuberculous epididymal abscess, and the urogenital tract was found to be involved in 11% of patients with tuberculous epididymal abscess. However, a comparison between tuberculous and pyogenic epididymal abscesses was not possible in terms of the incidence of concomitant tuberculous infection in other organs because the infection was not investigated in patients with pyogenic epididymal abscess.

In epididymal abscess, blood flow is not seen in the center but is increased in the peripheral portion on color Doppler sonography [10, 11, 14]. However, the usefulness of color Doppler sonography in differentiating tuberculous and pyogenic epididymal abscesses has not been described. Although our results showed no blood flow in the center of the lesion in either disease, the degree of blood flow in the peripheral portion was lower in tuberculous epididymal abscess. We believe this finding is related to the lower degree of vascularity revealed by chronic inflammation and fibrosis on microscopy and to the small amount of residual parenchyma in the epididymis resulting from the larger abscess size compared with pyogenic epididymal abscess. We suggest that an observation of blood flow at the peripheral portion of the abscess on color Doppler sonography is valuable in differentiating tuberculous epididymal abscess from pyogenic epididymal abscess.

Our study has several important limitations. First, our study was a retrospective analysis with a small study population. Despite this limitation, we found that some of the clinical, gray-scale sonographic, and color Doppler sonographic findings were valuable in distinguishing tuberculous epididymal abscess from pyogenic epididymal abscess. Second, tuberculous epididymal abscess was pathologically confirmed in all cases, although only four cases of pyogenic epididymal abscess were pathologically confirmed. However, we believe that the remaining nine cases are pyogenic epididymal abscess because of their clinical improvement after antibiotic therapy. Third, the subjective grading of vascularity of the abscesses by our reviewers was another limitation, which we tried to reduce.

In conclusion, in differentiating tuberculous and pyogenic epididymal abscesses, some clinical, gray-scale sonographic, and color Doppler sonographic features are useful, including the presence of long-term scrotal swelling without tenderness and a lower degree of blood flow in the peripheral portion of the large abscess seen on gray-scale and color Doppler sonography, which are suggestive of tuberculous epididymal abscess. These findings may be helpful for potentially obviating inappropriate antibiotic treatment of tuberculous epididymal abscess.

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