The main gynecological conditions causing acute abdominal pain are functional ovarian cysts, ovarian torsion, and hydrometrocolpos. Transabdominal US will commonly show the lesion. Transvaginal US should not be routinely done as a primary investigation in adolescent girls, but may supplement the abdominal examination in sexually active patients.
Ovarian cysts usually result from failure of involution during the normal menstrual cycle. They may cause acute lower abdominal or pelvic pain in pre-pubertal and pubertal girls if they are complicated by rupture, torsion, or hemorrhage, or if they become significantly enlarged. Transabdominal US in uncomplicated cysts usually show a thin-walled, well-defined, echo-free ovarian mass, and excellent through-transmission (CARtY 2002). Simple cysts may be quite large, but most of them resolve spontaneously, only requiring clinical and sonographic follow-up. Rarely, there is a complication, the most common being ovarian torsion. Functional cysts may also rupture and result in free fluid in the pelvis. Despite the high frequency of presentation of these cysts, they should not be assumed to be the cause of the acute symptoms until other pathologies, especially appendicitis, have been excluded.
Functional cysts may develop internal hemorrhage. Hemorrhagic ovarian cysts typically present with sudden and severe lower abdominal pain. On US, they may appear echogenic or hypoechoic, but never anechoic (Fig. 1.84). Most of them are heterogeneous in echogenicity and show through-transmission due to their underlying cystic nature. They may contain internal clots, septations, as well as fluid-debris levels. The cyst wall may be thin or thick and irregular. A changing US appearance over time can help make the diagnosis. The initial bright echogenicity of acute hemorrhage, produced by fibrin deposition, becomes less echogenic and eventually fluid-like as the fibrin dissolves and the clot lyses (SuRRAtt and SiEgEl 1991). A complex cystic ovarian mass may often be treated conservatively, particularly if there are no features suggesting the presence of torsion. In these cases, US follow-up is necessary until complete resolution.
In adnexal torsion, the ovary twists with the vascular pedicle. Torsion leads initially to compromise of lymphatic and venous drainage, followed later by arterial occlusion and thrombosis and eventual hemorrhagic infarction of the involved organs. It is most common in prepubertal girls, due to increased adnexal mobility prior to menarche. Right-sided torsion is more common as the sigmoid colon prevents excessive movements of the left ovary and fallopian tube. Adnexal torsion is a true surgical emergency which clinically may mimic acute appendicitis, gastroenteritis, or intussusception. The pain may be intermittent and localized to one or other lower quadrant, or it may be severe, acute, and generalized. Associated nausea, vomiting, or constipation may occur. A palpable abdominal mass and a paralytic ileus may also be present. US is the most important imaging modality for the diagnosis of adnexal torsion. The US findings are variable. Typically, the ovary involved appears noticeably enlarged, with multiple enlarged peripheral follicles (GRAif and ItzchAk 1988) (Fig. 1.85), being hard to delineate from the little uterus that is often displaced anteriorly. This appearance is seen in 60%-75% % of cases of torsed normal adnexa. However, the ovary appearance may vary depending on the degree of internal hemorrhage, stromal edema, and infarction which has occurred by the time it is diagnosed. Other grayscale imaging appearances include a purely cystic, a mixed cystic-solid, or a solid adnexal mass lesion. Fluid may be present in the pouch of Douglas.
Doppler studies may demonstrate absent or reduced central venous and arterial flow. However, complete absence of Doppler signal alone is not a specific finding as flow may be difficult to obtain even in normal ovaries. In addition, low velocity peripheral arterial flow (less than 5 cm/s) may per
Fig. 1.84a-d. Several appearances of symptomatic ovarian cysts. a Luteinic cyst. Well-defined hyperechogenic mass in the left ovary (arrows). Regardless of its echo pattern, it typically shows through-transmission due to its underlying cystic nature. Control performed 6 weeks later demonstrated a normal left ovary. b Hemorrhagic ovarian cyst. Complex cystic mass (arrows). c Longitudinal US scan in an adolescent patient with acute abdominal symptoms. A cystic mass (C) is observed behind the uterus (U) in the cul-de-sac. Another complex mass (M) is present above the cyst and uterus. d Axial US scan of the same patient demonstrates no flow within the mass on color Doppler sonography. Surgery demonstrated the cystic mass to be a teratoma and the complex mass to be a hemorrhagic cyst. B, bladder
Fig. 1.84a-d. Several appearances of symptomatic ovarian cysts. a Luteinic cyst. Well-defined hyperechogenic mass in the left ovary (arrows). Regardless of its echo pattern, it typically shows through-transmission due to its underlying cystic nature. Control performed 6 weeks later demonstrated a normal left ovary. b Hemorrhagic ovarian cyst. Complex cystic mass (arrows). c Longitudinal US scan in an adolescent patient with acute abdominal symptoms. A cystic mass (C) is observed behind the uterus (U) in the cul-de-sac. Another complex mass (M) is present above the cyst and uterus. d Axial US scan of the same patient demonstrates no flow within the mass on color Doppler sonography. Surgery demonstrated the cystic mass to be a teratoma and the complex mass to be a hemorrhagic cyst. B, bladder sist due to ovarian dual blood supply. The presence of damped arterial and venous flow or absent arterial and damped venous flow has also been described as being associated with adnexal torsion. If torsion is intermittent or incomplete, then Doppler study may be normal (Hurth et al. 2002).
Pelvic inflammatory disease is increasing in incidence in sexually active adolescents, and is due to either Chlamydia trachomatis or Neisseria gonorrhea infection. Infection ascends from the cervix to involve the endometrium and fallopian tubes. The fallopian tubes become edematous and hyperemic and are filled with pus, which may spill over into the peritoneum causing peritonitis. If the fimbri-ated ends of the fallopian tubes become adherent to the ovaries, the tubes may obstruct and distend with fluid, resulting in a hydrosalpinx, or with pus, resulting in a pyosalpinx. The infection may extend to the ovaries, resulting in a tubo-ovarian abscess. Clinically, patients with pelvic inflammatory disease present with pelvic pain that may worsen during or just after menstruation. Dysfunctional uterine bleeding and dysuria may also appear. Ultrasound is the primary imaging modality, the sonographic
Fig. 1.85a-e. Ovarian torsion. a,b Longitudinal US scan shows an echogenic mass with tiny cyst behind the uterus (U) in the cul-de-sac. The little prepuberal uterus is displaced anteriorly, and it is hard to delineate it from the mass (arrows). c Color Doppler showing the absence the flow in the center of the ovary. d Surgical specimen. e In vitro study of the ovary. Multiple edematous immature follicles may be visualized in the ovary not only in the periphery but in the whole ovary. B, bladder
findings varying according to the extent of the disease. Endometritis may lead to enlargement of the endometrium and fluid may be seen in the endo-metrial cavity. Pyosalpinx manifests as thickened and dilated fallopian tubes containing debris-laden fluid and septations. A tubo-ovarian abscess usually appears as a complex and heterogeneous adnexal mass, commonly accompanied by free fluid in the pouch of Douglas. Transvaginal US gives better anatomical detail of the inflamed adnexal structures and may obviate the need for laparoscopy in adolescents with pelvic inflammatory disease (Bulas et al. 1992). In severe cases, CT and MRI can be useful in demonstrating the extent of the disease throughout the abdomen and pelvis.
Genital tract obstruction may also be a cause of acute abdominal pain. It may present with pain and amenorrhea in adolescence and is usually due to an imperforate hymen, but it may also be due to vaginal or cervical atresia. With an imperforate hymen, the menstrual products during menarche collect in the vagina and uterus, producing an hydrometrocolpos. In vaginal or cervical atresia, the products may collect in the fallopian tubes and broad ligament. The diagnosis is easily made by US when the fluid-filled vagina and dilated uterus are seen behind the bladder (Fig. 1.86). It is not unusual that, after a urine culture is performed for suspected urinary tract infection, the patient undergoes US with an empty bladder. In these situations, special attention must be paid not to mistake a fluid-filled vagina with a full bladder. Identification of the dilated uterus in the cranial aspect of the cystic structure that occupies the pelvis can help make the right diagnosis.
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