2.3\ Hydropyosalpinx

Salpingitis is the most important cause for obliteration of the fimbriated end of the tube, which leads to hydrosalpinx. Other etiologies include fallopian tube tumors, endometriosis, and adhesions from prior surgery. Serous fluid, blood, or pus may accumulate and cause distension of the fallopian tube.

2.3.1\ Imaging Findings

Dilated fallopian tubes appear as fluid-filled tubular structures arising from the uterine fundus and separate from the ipsilateral ovary. The typical finding is a tortuous, cystic tubular structure with interdigitating incomplete mural septa (Fig. 5). These septa are thin and display low signal intensity on T2WI. Distinct septal enhancement on contrastenhanced T1WI or CT may support the diagnosis of pyosalpinx (Tukeva et al. 1999). The nature of fluid within a dilated salpinx is best evaluated on MRI. The signal intensity varies in accordance with the contents, which ranges from water-like simple fluid to proteinaceous or hemorrhagic fluid. Multiplanar imaging and opacification of bowel loops with contrast allows identification of the tubal origin and differentiation from dilated bowel loops.

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2.3.2\ Differential Diagnosis

Tubal diameters can reach up to 10 cm and therefore hydrosalpinx may mimic multiloculated ovarian tumors, especially cystadenomas. Identification of the ovary separate from the lesion using multiplanar imaging helps to differentiate. Any enhancing component within a dilated tube, apart from fine incomplete smooth septations, should suggest the possibility of fallopian tube carcinoma or ectopic pregnancy (Kawakami et al. 1993). Pyosalpinx and hematosalpinx may be differentiated from hydrosalpinx by the signal intensity of the fluid content: a hydrosalpinx contains simple fluid (high on T2, low on T1, with no restricted diffusion, similar to CSF or urine) whereas a pyosalpinx contains pus (typically intermediate on T2, hyperintense on T1 and T1FS, with restricted diffusion); a hematosalpinx contains blood (typically hypointense on T2, hyperintense on T1 and T1FS with restricted diffusion).

2.4\ Tubo-ovarian Abscess

In the majority of cases, tubo-ovarian abscess (TOA) results from PID. Other etiologies include complications of surgery or intra-abdominal

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Fig. 5  Hydrosalpinx on CT and MRI. Transaxial CT (a) and coronal T2WI (b). A multiseptate lesion (arrows) in the left adnexal region is demonstrated on CT (a) and MRI (b): Its tubular nature with widening at the cephalad

end is demonstrated on MRI (b). The thin incomplete, interdigitating septa (small arrows) are a typical finding of a dilated fallopian tube on CT and MRI

inflammatory bowel diseases, such as appendicitis, diverticulitis, or Crohn’s disease. In most cases, TOA is caused by a polymicrobial infection with a high prevalence of anaerobes. Intrauterine contraceptive device (IUCD) users, especially in the first few months after insertion, also have a greater risk of PID. Pelvic actinomycosis is considered to be highly associated with the use of IUCD (Kim et al. 2004).

TOA most commonly occurs in women of reproductive age. Tubo-ovarian abscesses in postmenopausal women are rare, but can be seen in women with diabetes or previous radiation therapy. In postmenopausal women presenting with TOAs, a concomitant pelvic malignancy should be excluded as there is a significant association with malignancy (Protopapas et al. 2004).

The pathway of the inflammatory disease includes direct extension along the fallopian tubes. A hematogenous or lymphatic spread is found in the rare cases of tuberculous involvement of the genital tract (Kim et al. 2004).

2.4.1\ Imaging Findings

On CT and MRI, tubo-ovarian abscesses are thick-walled, multilocular complex heterogeneous fluid-containing adnexal masses that can be unilateral or bilateral (Fig. 6). They may

­contain irregular inner contours, internal septa, gas, fluid, or a fluid-debris level (Sam et al. 2002). Necrosis or loculated fluid areas may resemble serous fluid, but can also be proteinaceous or hemorrhagic with T1 shortening. Tubo-ovarian abscesses most commonly display a heterogeneously intermediate or hyperintense signal on T2WI (Ghiatas 2004). They are surrounded by thick, markedly enhancing outer borders (Fig. 7). Due to dense pelvic adhesions or fibrosis, meshlike strands in the pelvic fat planes are almost always seen; these demonstrate enhancement on CT or contrast-enhanced T1WI, and display a low signal on T2WI. The uterus and omentum usually become adherent. The abscess may enlarge and fill the pouch of Douglas or leak and produce metastatic abscesses and cause local peritonitis.

Involvement of adjacent structures includes thickened bowel loops with or without dilatation. Peritoneal enhancement, especially in the inferior pelvis, and small amounts of ascites are signs of associated peritonitis. Obstruction of the ureters may also be seen. Internal gas locules are the most specific radiologic sign of an abscess but are unusual in tubo-ovarian abscesses (Bennett et al. 2002). In the case of actinomycosis, there may be complex cystic

Fig. 6  Bilateral tubo-ovarian abscesses (arrows) are shown as thick-walled tubular, cystic adnexal masses. The rectum (R) and uterus (U) are also shown

Fig. 7  Bilateral tubo-ovarian abscess on contrastenhanced fat saturation T1WI. Bilateral adnexal cysts with thick walls and septations with avid enhancement (arrows). The uterus is shown for reference (U)

Fig. 8  MRI images in a patient with actinomycosis. An IUCD (arrow) can be seen in the uterine cavity on the axial T2WI. The diffusion-weighted image and ADC map

shows thickening and fibrosis in the presacral space that demonstrates restricted diffusion (star). There is a complex lesion

solid ovarian masses and retroperitoneal thickening which may have the appearance of retroperitoneal fibrosis and a tendency for the inflammatory tissue to invade across tissue planes (Fig. 8) (Ha et al. 1993; Akhan et al. 2008). Appearances may mimic disseminated ovarian cancer with peritoneal deposits (Hildyard et al. 2013). However, presacral thickening is a typical finding and this should raise suspicion of actinomycosis (Hildyard et al. 2013).

2.4.2\ Differential Diagnosis

Endometriomas may sometimes display similar imaging characteristics to TOA, with a thick rim; however, the clinical background is different. Ovarian cancer as well as ovarian

metastases often present also as multiseptate ovarian masses (Willmott et al. 2012). In ovarian cancer, brightly enhancing solid tissue (irregular septae, papillary formations, or mural nodules) is typically found and signs of inflammation of the pelvic fat are absent. Furthermore, ovarian cancer is not frequently associated with tubal dilatation. However, in postmenopausal women with TOA, malignancy is a significant concern (Protopapas et al. 2004). If tubo-ovarian abscesses involve adjacent pelvic organs, the site of origin often cannot be reliably defined. Tuberculous peritonitis involving the adnexa mimics peritoneal carcinomatosis with nodularities along tuboovarian surfaces, and large amounts of ascites (Kim et al. 2004) (Fig. 9).

Fig. 9  MRI of peritoneal tuberculosis. Axial T2WI (a) demonstrates ascites (open arrows), omental thickening (star), and smooth thickening of the peritoneal reflections in the left flank (filled arrows). Axial T1 fat-saturated post-contrast MRI (b, c) confirm that the smooth peritoneal thickening in the mid-abdomen (b) and pelvis (b)

enhances (solid arrows). There is no ovarian mass. There is also enhancement of the thickened omentum (star) and prominent mesenteric vessel enhancement—in keeping with an inflammatory process. The patient also had pleural effusions. A biopsy confirmed tuberculosis

2.4.3\ Value of Imaging

The diagnosis of PID is based on clinical examination and laboratory studies, including assessment of vaginal secretions, and sonographic findings. In cases of nonspecific findings or suspected complications of PID, especially tuboovarian abscess or peritonitis, CT or MRI may serve as adjunct imaging modalities. CT is commonly used to assess complications of PID, especially when a tubo-ovarian abscess or peritonitis

is suspected. Furthermore, it assists in defining the origin of the tubo-ovarian abscess and can differentiate it from inflammatory bowel disease. CT is also especially useful as a guide for surgery or a CT-guided drainage as well as identifying complications such as involvement of other organs (Fig. 10). MRI and CT are both useful in differentiating between an adnexal tumor and an abscess. The imaging findings, however, can only be interpreted in context with the clinical