Fig. 19  Stage IB. (a) T2w TSE image in sagittal orientation. The cervical cancer (arrow) is depicted as a high- signal-intensity tumor that primarily involves the posterior cervix and is surrounded by low-signal-intensity cervical

stroma. There is no infiltration of the posterior vaginal fornix (open arrow). (b) T1w TSE image with FS in sagittal orientation. Following administration of Gd-DTPA, a partially necrotic tumor is depicted

superficial­ inguinal lymph nodes, which must be taken into account in the diagnostic evaluation. The lower third of the vagina corresponds to the length of the urethra (from the pelvic floor to the level of the urinary bladder).

2.3.4.6  Stage IIIB

Cervical cancer with invasion of the pelvic sidewall corresponds to stage IIIB. Cervical cancer can reach the pelvic sidewall by continuous lateral growth through the parametrial tissue and the sacral bone and through posterior extension along the sacrouterine ligaments (Fig. 28). T2-weighted images depict tumor infiltration as hyperintense lesions in the intermediate signal intensity of the muscle, or low signal intensity of the cortical bone, or as thickening of the vascular wall. T1-weighted imaging allows evaluation of the extent of advanced parametrial infiltration and possible extension to the pelvic sidewall with good delineation of the hypointense tumor mass from the lateral parametrial tissue and the inter- mediate-signal-intensity muscle tissue. The

tumor-related consumption of the lateral fat plane seen on T1-weighted images may already suggest extension to the pelvic sidewall from the surgical perspective even if direct infiltration of the sidewall is not yet apparent (Zand et al. 2007). Visualization of tumor within 3 mm from the obturator internus, levator ani, and piriform muscle or the iliac vessels is considered highly suggestive of stage IIIB disease (Freeman et al. 2013; Zand et al. 2007).

Ureteral infiltration and obstruction with hydronephrosis is also classified as stage IIIB disease (Fig. 29). The ureter courses over the psoas muscle from dorsolaterally before it descends into the pelvis. In the true pelvis, the ureter takes an anteromedial course from the pelvic sidewall in the inferior segment of the parametria toward the base of the bladder. At the level of the uterine isthmus, the ureter courses lateral to the uterine cervix at a distance of 1–2.5 cm and is over-crossed by the uterine artery anteriorly. The ureter is typically infiltrated when there is lateral tumor growth through the parametria. A thickening of the ure-

a

b

Fig. 20  Stage IB. (a) T2w TSE image in sagittal orientation. The cervical cancer (arrow) is depicted as a high- signal-intensity tumor that primarily involves the posterior cervix and is surrounded by low-signal-intensity cervical stroma. There is no infiltration of the posterior vaginal fornix (open arrow). (b) T1w TSE image with FS in sagittal orientation. Following administration of Gd-DTPA, a well vascularized cervical cancer is depicted

teral wall or hydronephrosis is seen. In patients with a tumor mass in the parametria, the kidneys and urinary tract should be included in the imaging volume in order to confirm or exclude ureteral obstruction and hydronephrosis.

2.3.4.7  Stage IVA

Stage IVA cervical cancer is characterized by infiltration of the mucosa of the rectum or urinary bladder. The FIGO classification is based on mucosal infiltration of these organs because

the outer wall layers are not amenable to evaluation by endoscopy and biopsy. MRI, on the other hand, can identify infiltration of the outer muscular layer of the bladder and rectum. Tumor extension to the rectum is either through invasion of the sacrouterine ligament or through direct infiltration of the pouch of Douglas with subsequent extension of the tumor to the anterior rectal wall (Fig. 30). The peritoneal fold of the rectouterine space (pouch of Douglas) acts as a natural barrier that aggravates extension to the anterior rectal wall.

The urinary bladder is infiltrated through continuous anterior growth of the cervical tumor along the peritoneal fold between the cervix and the bladder, also referred to as the vesicouterine ligament (Figs. 31 and 32). Sagittal and transverse T2-weighted MR images depict infiltration as segmental disruption of the hypointense muscular layer of the wall of the bladder or rectum by hyperintense tumor. Contrast-enhanced Tl-weighted images often enable a more reliable identification of segmental disruption because of stronger enhancement of the tumor as compared with the muscular layer. Infiltration of the wall of the bladder and/or the rectum as well as contiguity of cervical cancer with either of these organs have important therapeutic implications. Bladder or rectal invasion can be depicted by means of MR imaging with a sensitivity and specificity of 71–100% and 89–91%, respectively (Rockall et al. 2006). For the exclusion of bladder and rectal invasion MR images achieve negative predictive values of 100%, making invasive endoscopic examinations obsolescent (Rockall et al. 2006).

Tumor infiltration of these hollow organs is quite often associated with the development of fistulas. A collection of air in the urinary bladder may indicate a vesicouterine fistula especially in patients under chemoor radiotherapy (Figs. 46, 47, and 48). A fistula can be best demonstrated with fat-saturated, contrast-enhanced T1-weighted sequences, which will depict the fistula as an enhancing formation with a nonenhancing filiform lumen. Alternatively, a fistula can be demonstrated as a hyperintense filiform structure with a high sensitivity by using a T2-weighted inversion recovery sequence.