Pictorial Essay: The Value of Rectal Water in the Assessment of Rectosigmoid Pathology  Randy Fanous, MD, BHSC, Nasir Jaffer, MD, FRCPC  Canadian Association of Radiologists Journal  Volume 62, Issue 2, Pages 110-121 (May 2011) DOI: 10.1016/j.carj.2010.01.007 Copyright © 2011 Terms and Conditions

Figure 1 Sagittal contrast enhanced computed tomography image with rectal water, demonstrating normal colonic morphology, as evidenced by normal haustral folds (white arrows), normal bowel wall thickness, with a mucosa indistinct from the remainder of the mural layers, normal lumenal calibre, and normal pericolic fat, without inflammatory or infiltrative stranding (white asterisk). Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 2 Axial and coronal contrast enhanced computed tomography images with rectal water, demonstrating a very subtle, tiny, 3-mm sessile polyp at the rectoanal junction (white arrows), which was subsequently resected endoscopically. Pathology revealed a villous adenomatous polyp with high-grade dysplasia. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 3 Axial and sagittal contrast enhanced computed tomography images obtained at a 2-month interval, without (A) and with (B) rectal water contrast administration. Although large, the mass in image (A) is poorly delineated, without the administration of rectal contrast, and may even be mistaken for normal collapsed or peristaltic large bowel. However, in panel (B), rectal water makes the annular constricting appearance of the mass much more conspicuous (white arrows). Metastases were also identified within the liver as multiple nonenhancing low-attenuation lesions (black arrows). The final diagnosis in this patient was metastatic rectal adenocarcinoma to the liver. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 4 Single axial contrast enhanced computed tomography image with rectal water in a patient with an acute flare of ulcerative colitis, demonstrating mucosal hyperenhancement (white arrowhead) in addition to bowel-wall thickening (white arrows). Mucosal hyperenhancement would have otherwise been missed if a positive rectal agent were used instead. A small amount of free fluid is also seen within the rectovesicular space of the pelvis (white asterisk). Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 5 Axial contrast enhanced computed tomography images with rectal barium (A) and rectal water (B) in a patient with known ulcerative colitis. The images were acquired over a 5-year interim and demonstrate the chronic changes of this disease, characterized by temporal loss of the normal colonic haustra, with a resultant featureless lead-pipe appearance. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 6 Single axial contrast enhanced computed tomography image with rectal water, in a patient with left-sided diverticulosis, demonstrating bowel-wall thickening (white arrow) and shortening of the sigmoid colon secondary to contraction of the tineae coli muscles, as well as hyperemia characterized by multiple well-defined punctate mesenteric vessels within the sigmoid mesocolon (white arrowheads). There is no evidence of pericolic fat stranding, mucosal hyperenhancement, or intramural abscess to suggest acute diverticulitis. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 7 Contrast enhanced computed tomography images with rectal water (A) and rectal barium (B) completed at a 2-month interval, demonstrating evidence of sigmoid diverticulitis, with intramural abscess formation, unchanged in the interim. Both rectal water and rectal barium are equally adequate at illustrating circumferential bowel thickening (long white arrows) and intramural abscess formation (white arrowhead). However, mucosal enhancement (short white arrow) is only appreciated with the administration of rectal water and is indicative of mucosal inflammation and hyperemia. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 8 Axial contrast enhanced computed tomography images with rectal barium (A) and rectal water (B) acquired 7 months apart in a patient with a known history of recurrent diverticulitis who presented with multiple episodes of abdominal pain and obstipation. There is no evidence of acute diverticulitis on either of these studies. However, diffuse subtle mucosal hyperenhancement is appreciated within the sigmoid colon with rectal water, consistent with mild persistent mucosal disease in the setting of healing diverticulitis. It is impossible to appreciate this finding with rectal barium. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 9 Axial and coronal contrast enhanced computed tomography images with rectal water, demonstrating mild eccentric thickening of the left lateral rectal wall (white arrows). Stool is noted medially adjacent to the lesion (black arrowheads). There is no evidence of perifocal fat infiltration. This lesion was confirmed to be a flat adenomatous polyp on endoscopic biopsy. This case demonstrates the utility of rectal water in the detection of flat lesions that may otherwise be missed if a positive rectal contrast agent is used instead. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 10 Axial and coronal contrast enhanced computed tomography images with rectal barium in a patient with acute sigmoid diverticulitis, complicated by perforation and abscess formation within the presacral space (white arrowheads). A few diverticuli are visualized within the sigmoid colon with bowel wall thickening (white asterisk), as well as a moderate-to-large amount of free fluid in the pelvis and significant fat stranding. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 11 Images obtained in a young male patient with chronic ulcerative colitis, who underwent subtotal colectomy with an ileoanal pelvic pouch procedure. The anastomotic staple line of the J-pouch is visualized within the pelvis (white arrowheads). Contrast enhanced computed tomography images were obtained with rectal water (A) and rectal iodinated contrast (B) at a 3-year interval for chronic recurrent unremitting perineal symptoms. Initial images with rectal water demonstrate suggestion of a leak from the posterior aspect of the pouch (long white arrows) into the presacral space, with an associated small presacral collection. However, contrast extravasation cannot be appreciated given that a negative rectal contrast agent was used. On the follow-up computed tomography, a positive rectal contrast agent was used instead, given the heightened concern for an anastomotic leak. On these images, note is made of a tiny focus of high density within the presacral collection (short white arrows), which confirms the presence of rectal contrast extravasation and, therefore, an anastomotic leak. The sagittal computed tomography image (C) demonstrates the usefulness of sagittal reformations in the assessment of a suspected anastomotic leak. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 12 Axial and coronal contrast enhanced computed tomography images with rectal water in a patient with known Crohn disease. There is evidence of colonoenteric fistulization at the site of the anastomotic suture line within the transverse colon (short white arrow). The transverse colon and the third part of the duodenum are closely opposed, without a fat plane between them, and no discernible fistulous tract (long white arrow). However, there is indirect evidence of fistulization, characterized by extravasation of high-density oral contrast material from the duodenum into the transverse colon that contains rectal water (white arrowhead). If positive rectal contrast were used, then this would not have been appreciated. Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions

Figure 13 Single contrast enhanced computed tomography image in the same patient as that of Figure 12, performed approximately 1 week earlier. Although no rectal or oral contrast was administered, fluid within the bowel acts as a negative contrast agent analogous to water. A colonoenteric fistula between the transverse colon and the third part of the duodenum is appreciated, with excellent visualization of the fistulous tract (white arrow). Canadian Association of Radiologists Journal 2011 62, 110-121DOI: (10.1016/j.carj.2010.01.007) Copyright © 2011 Terms and Conditions