1. Computed tomography following surgical resection of colorectal cancer: imaging features of normal postoperative changes, complications, and tumour recurrence A Enríquez Puga, I Herrera Herrera, A Pérez Martínez, J Pinto Varela, C Cereceda Pérez, S Diéguez Tapias

2. Learning Objectives To graphically illustrate the computed tomography (CT) imaging features of: To graphically illustrate the computed tomography (CT) imaging features of: normal postoperative anatomic changes that occur after surgical resection of colorectal cancer normal postoperative anatomic changes that occur after surgical resection of colorectal cancer its complications its complications local and distant tumor recurrence. local and distant tumor recurrence.

3. Background Colorectal cancer is a common malignancy that results in significant morbidity and mortality. Colorectal cancer is a common malignancy that results in significant morbidity and mortality. Surgical resection is the treatment of choice for patients with localised disease. Surgical resection is the treatment of choice for patients with localised disease. Routine postoperative CT is useful in identifying “normal” postoperative anatomic changes, complications, and tumor recurrence in colorectal cancer patients who have undergone surgical resection. Routine postoperative CT is useful in identifying “normal” postoperative anatomic changes, complications, and tumor recurrence in colorectal cancer patients who have undergone surgical resection.

4. Normal postoperative changes AB Fig 1. Normal CT findings six weeks after laparoscopic right hemicolectomy and ileocolic anastomosis. Contrast-enhanced CT shows mild diffuse bowel wall thickening at the level of the anastomosis with thickening of the perianastomotic fascia but no areas of contrast enhancement. Proximal and distal bowel loops of normal appearance.

5. Normal postoperative changes Fig 2. Normal contrast-enhanced CT findings 10 months after total rectocolectomy and terminal ileostomy. Terminal ileostomy (A), suturing material at the level of rectal amputation site and minimal stranding of surrounding fat (B, C). A B C

6. Normal postoperative changes A Fig 3. 70-year old woman four days after laparoscopic right hemicolectomy and ileocolic anastomosis for caecum adenocarcinoma. Contrast-enhanced CT shows significant mesenteric fat stranding and free fluid at the level of the anastomosis, mild thickening of the gallbladder wall, and minimal amount of perihepatic free fluid. B C

7. Early complications Postoperative paralytic ileus Postoperative paralytic ileus Anastomotic dehiscence Anastomotic dehiscence Fistula Fistula Abscess Abscess

8. Postoperative paralytic ileus Fig 4. Paralytic ileus. Dilated small bowel loops with no wall thickening and no transition indicative of paralytic ileus, in an 84-year-old man who had recently undergone high anterior resection of rectosigmoid. AB

9. Anastomotic dehiscence Fig 5. Anastomotic dehiscence in a 78-year-old man five days after subtotal colectomy for descending colon adenocarcinoma. Spiral CT obtained with oral contrast shows leakage of contrast (arrows) from the ileocolic anastomosis towards the left parietocolic gautier, a finding consistent with suture dehiscence. Note the small amount of perihepatic and perianastomotic free fluid A B

10. Anastomotic dehiscence Fig 6. Anastomotic dehiscence in an 80-year old man 21 days after low anterior resection of rectum. Contrast-enhanced CT shows a moderate amount of ectopic air and some free fluid located within the surgical bed and adyacent to the anastomosis site. These findings are sugestive of anastomotic dehiscence. There is contrast within small bowel loops that has not yet reached the loops at the level of the anastomosis. A B C D D

11. Rectovaginal and presacral fistulae Fig 7. Recto-vaginal fistula. Contrast-enhanced spiral CT shows a combined recto-vaginal (yellow arrow) and recto-presacral area (red arrow) fistulae in a 69-year-old woman who had undegone laparoscopic low anterior resection for carcinoma of the rectum 12 days earlier. A B

12. Rectovesical fistula Fig 8. Rectovesical fistula in 63 year-old-man with low anterior resection of recto-sigmoid carcinoma. Combined intravenous contrast-enhanced CT and enema show contrast in rectum (*), bladder (*), and pelvic extraperitoneal spaces (*). These findings are suggestive of a synchronic rectovesical and rectoperitoneal fistulae. A B * * * * * * * *

13. Near-anastomotic site abscess AB Fig 9. Contrast-enhanced CT scan 17 days after subtotal colectomy with ileo- sigmoid anastomosis. Soft-tissue mass with a partially septated fluid collection with enhancing rims suggestive of an abscess near the anastomosis site, between prostate gland and rectum (arrow). The abscess seems to englobe the prostate gland (A). Nine months later the prostate gland remains enlarged whereas the fluid collection has fully resolved.

14. Near-anastomotic site abscess C D Fig 11. Same patient as in fig 10. Sagittal reformatted contrast-enhanced CT scan shows an attenuating soft-tisue mass (arrow) in the space between the prostate gland and rectum with fluid collection within, suggestive of a periprostatic abscess (A). Nine months later the abscess has resolved although the prostate remains enlarged.

15. Late complications Postsurgical fibrosis Postsurgical fibrosis Canalisation disorders: Canalisation disorders: Adhesions Adhesions Paracolostomic hernia Paracolostomic hernia

16. Postsurgical fibrosis A B Fig 12. Postsurgical fibrosis in 66-year-old woman who had undergone abdominoperineal amputation 11 months earlier for rectal carcinoma. Contrast-enhanced CT shows low attenuating widening of soft tissue located in the pre-sacral region with posterior traction of bowel loops (A) and bladder (B), in relation to postsurgical fibrosis (arrows)

17. Small bowel obstruction secondary to adhesions Fig 13. Small bowel obstruction caused by adhesions. CT scan shows dilated, fluid-filled loops with almost totally collapsed bowel loops at the transition zone (arrows). A B

18. Paracolostomic hernia AB Fig 14. Parastomal hernia. CT scan shows parastomal herniated bowel (arrow) lateral to ostomy site.

19. Cancer recurrence Local recurrence of rectal adenocarcinoma Local recurrence of rectal adenocarcinoma Distal recurrence of rectal adenocarcinoma Distal recurrence of rectal adenocarcinoma Metastatic lymphadenopathy Metastatic lymphadenopathy Palliative procedures Palliative procedures

20. Local recurrence of rectal adenocarcinoma A B A Fig 15. Local recurrence of rectal adenocarcinoma. Contrast-enhanced CT shows a large, circumferential soft-tissue mass with small air bubbles within (arrow). The mass extends to involve the posterior bladder wall. The findings are compatible with recurrent, locally invasive, abscessed rectal adenocarcinoma. Note the dilated bowel loop indicative of proximal bowel obstruction.

21. Distal recurrence of rectal adenocarcinoma A B Fig 16. Distal recurrence of rectal adenocarcinoma. Spiral CT obtained with oral contrast material shows luminal narrowing and segmental circumferential thickening of the hepatic flexure (arrow) with secondary dilatation of small bowel loops and caecum. Adenocarcinoma was confirmed at biopsy.

22. Metastatic lymphadenopathy C D Fig 17. Metastatic lymphadenopathy. Contrast-enhanced CT shows an enlarged lymph node (arrow) in the right inguinal region of an 82-year old man with metastatic recurrent rectal cancer. Metastatic recurrent adenocarcinoma was confirmed at biopsy.

23. Palliative sigmoid colon endoprosthesis Fig 19. Local recurrence of sigmoid colon carcinoma. Contrast-enhanced CT in a 79 year-old woman shows an endoprosthesis device placed for the alleviation of bowel obstruction secondary to stenosing recurrent sigma neoplasia. A B

24. Distal ureter obstruction causing ureterohydronephrosis Fig 20. Renal tract obstruction. Contrast-enhanced CT in a 79 year-old woman with local recurrence of sigmoid carcinoma. Large heterogeneous enhancing soft tissue mass with infiltration of the surrounding fat and invasion of the uterus. Left sided ureterohydronephrosis secondary to involvement of the distal ureter. Note the circumferential hyperdensity within the soft tissue mass of palliative endoprothesis. CD

25. Conclusion Surgical resection of colorectal cancer can alter normal anatomy and make image interpretation difficult. Familiarity with the radiological features of normal postoperative anatomic changes, complications, and tumor recurrence is essential for accurate CT evaluation of affected patients. Surgical resection of colorectal cancer can alter normal anatomy and make image interpretation difficult. Familiarity with the radiological features of normal postoperative anatomic changes, complications, and tumor recurrence is essential for accurate CT evaluation of affected patients.