1. Gastrointestinal changes
Chronic radiation enteritis (mostly ileum):
Bowel wall thickening related to submucosal oedema
Areas of stenosis and small-bowel obstruction
Fixation of bowel loops (fibrotic changes in the mesentery)
Loss of distensibility with strictures
Mucosal ulceration and complex fistulas

2. Chronic radiation ileitisB A
Fig 8. Chronic radiation enteritis. Axial T2-weighted (A) and fat-saturated T1-weighted contrast-enhanced (B) images show diffusely thickened and oedematous bowel wall with marked enhancement.

3. Chronic radiation ileitis
Fig 8. Chronic radiation enteritis. Coronal fat-saturated T1-weighted contrast-enhanced image shows diffusely thickened and oedematous bowel wall with marked contrast- enhancement

4. Chronic radiation enteritis
Fig 9. Chronic radiation enteritis. Contrast-enhanced CT scan shows a thickened edematous bowel wall and separation of small bowel loops in the pelvis in relation to radiation ileitis.

5. Chronic radiation enteritis
Fig 10. Chronic radiation enteritis. CT scan shows radiation-related thickening of bowel wall with luminal narrowing (arrow), consistent with radiation enteritis

6. Chronic radiation proctitis* * A B
Fig 11. Chronic radiation proctitis. Sagittal T2-weighted (A) and fat-suppressed T2- weighted (B) fast spin-echo images show diffuse thickening of the wall of the rectum with an increased amount of soft tissue (*) in the presacral space, consistent with radiation fibrosis

7. Radiation-induced proctitis
Fig 12. Chronic radiation proctitis. Sagittal T2-weighted image shows thickening of the wall of the rectum of radiation proctitis. Increased amount of soft tissue in the presacral space suggestive of radiation fibrosis

8. Sigmoid colon stenosis
Fig 13. Radiation-induced colon stenosis. CT scan shows a 10 cm-long sigmoid colon stenosis (arrow) with a foreign body impacted at its proximal end, and secondary large bowel obstruction.

9. Enterovaginal fistula* A B
Fig 14. Enterovaginal fistula. Delayed serial CT images following the administration of oral contrast show the presence of contrast material within both small bowel loop and vagina (arrow), in relation to radiation-induced enterovaginal fistula

10. Inter-sphincteric anal fistulaB
Fig 15. Inter-sphincteric anal fistula. Sagittal (A) and axial (B) T2-weighted images show a hyperintense lineal tract between the internal and external anal sphincters sugestive of an inter-sphincteric anal fistula

11. Genitourinary changes
Related to radiation dosage and previous bladder operations
Radiation cystitis
Ureteral stenosis:
Ureterohydronephrosis

12. Radiation cystitis A
Fig 16. Radiation cystitis. Axial and sagittal T2-weighted images show diffuse thickening of the bladder wall. B

13. Radiation cystitis
Fig 13. Radiation cystitis. Contrast-enhanced CT shows a grossly thickened bladder wall with increased perirectal and perivesical fat typical of radiation cystitis.

14. Radiation cystitis A B
Fig 14. Radiation cystitis. Axial T2-weighted (A) and contrast-enhanced CT images show focal thickening (arrows) of posterior bladder wall with thickened wall of rectum.

15. Radiation cystitis
Fig 14. Radiation cystitis. Contrast-enhanced CT scan shows diffusely thickened and enhanced bladder wall consistent with radiation cystitis. There is widening of the presacral space.

16. Bilateral hydronephrosis secondary to ureteral stenosis
Fig 15. Bilateral hydronephrosis secondary to ureteral stenosis. Coronal reformatted contrast-enhanced CT scan shows bilateral hydronephrosis that was secondary to trapping and subsequent stenosis of both ureters within an area of radiation fibrosis at the yuxtavesical junction.

17. Vesicouterine fistula
Fig 16. Vesicouterine fistula. Sagittal reformatted CT image shows fistulous tract (arrow) between body of uterus and posterosuperior part of bladder.

18. Conclusion
Awareness of the varied radiographic manifestations of radiation-induced changes in the pelvic organs and bones allows distinction of these changes from those associated with neoplastic, infectious, or inflammatory disease