Appearance of Uterine Scar Due to Previous Cesarean Section on Hysterosalpingography: Various Shapes, Locations and Sizes

Hysterosalpingography (HSG) is the radiographic evaluation of the uterus and fallopian tubes that is used predominantly in the assessment of infertility and evaluation of abnormalities of the uterus and fallopian tubes. Some of the abnormalities that can be detected by HSG include congenital anomalies, polyps, leiomyomas, synechiae and adenomyosis. HSG is also used to evaluate any scarring on the uterus and fallopian tubes. Cesarean section is the most commonly performed surgical procedure involving the uterus in fertile women. Cesarean section involves an incision made in the lower uterine segment or isthmus. Various changes in the site of the cesarean incision may be seen due to wall weakness and fibrosis. The scar may have various shapes; unilateral or bilateral, single or multiple, wedge-shaped or linear. Awareness of the appearance and locations of uterine defects due to previous cesarean section is necessary in order to differentiate them from normal variations and other pathologies mimicking it. In this study, we demonstrate the appearance of anatomic defects of the uterine cavity on HSG after cesarian section. We define different shapes such as thin linear defect, focal saccular outpouching, unilateral or bilateral diverticula (dog-ear like) and fistula and different locations such as the uterine body, lower uterine segment, uterine isthmus and the upper endocervical canal.


Introduction
There are different methods and instruments that can be used to perform a hysterosalpingography (HSG) .The procedure must be performed under strict sterile conditions, since the peritoneal cavity can easily become infected, with the infection spreading through the contrast medium. HSG is performed during the proliferative phase, after cessation of menstruation and before ovulation, between days 7 and 11, in order to avoid any early pregnancies (1)(2)(3). Furthermore, the endometrium is thin in this time period, so the image obtained may be better interpreted (4,5).
The patient is placed on a radiographic table in a lithotomy position. After insertion of the speculum, the cervix is grasped with a tenaculum at 12 o'clock and brought forward to straighten the uterus. A Jarco cannula is used to instill the contrast media (Visipaque 320mg/ml) into the

WOMEN'S IMAGING
cervix. All air bubbles should be removed from the cannula before injection. Under fluoroscopic monitoring, at least four images are obtained routinely, each time by instillation of 2-3 ml of contrast media. 1) Visualization of intrauterine lesions such as small polyps or synechiae may be better achieved when the uterus is partially filled with media.
2) The best time to evaluate the shape of the uterus is when the uterus is filled completely.
3) The appropriate time to check whether the fallopian tubes are obstructed or not are when the fallopian tubes are filled and intraperitoneal spillages are depicted. 4) Delayed image taken 30 minutes after removal of the instrument from the cervix is the choice to rule out peritoneal adhesions.
In patients suffering from chronic pelvic infection or an untreated sexually transmitted disease, some physicians prescribe antibiotics prior to or after the procedure. HSG is not routinely used for evaluation of a cesarean section scar; however, if done, HSG should be postponed to three months after the cesarean section (6,7). Evaluation of the cesarean scar is performed to choose the technique of future delivery and prevention of uterine rupture and in cases of abnormal bleeding after delivery (6-8).
Accumulation of blood or secretions in the scar leads to unreliable HSG results (7,9).      In the interpretation of a hysterosalpingogram, awareness of the appearance of the cesarean scar defect is important to avoid misdiagnosis of the scar as underlying pathology or normal variants (8)

Differential diagnoses of cesarean scar defect
4.1. Prominent cervical glands, small tubular structures arising from the cervical wall, which are typically multiple, bilateral and symmetric unlike the cesarean scar ( Figure 15)  A 28-year-old lady without a history of cesarean section with a pouch on the right side of the uterine isthmus due to uterine curettage 4.5. Congenital cervical diverticula. If the patient has no surgical history, it is helpful in the differential diagnosis ( Figure 18). 4.6. Focal adenomyosis: Ingrowing of the endometrial tissue into the myometrium with adjacent smooth muscle hyperplasia. It is seen in HSG as fine channels extended perpendicular to the uterine cavity ending in small diverticulum-like structures; focal adenomyosis are multiple and smaller than the cesarean section scar and accompany uterine enlargement, while cesarean section scars are usually larger and single ( Figure 19).