Water enema computed tomography (WE-CT) in the local staging of low colorectal neoplasms: comparison with transrectal ultrasound

Abstract

Background: To determine the accuracy of computed tomography performed with a water enema application (WE-CT) in the local staging of low colorectal neoplasms and to compare the results with those of transrectal ultrasonography (TRUS). Methods: Forty patients with low colorectal tumors were evaluated prospectively by CT with the simultaneous administration of a lukewarm rectal enema (0.5-1.5 L). Thin slices (5 mm) and intravenous application of iodinated contrast media were routinely used. TRUS was performed in 18 patients. Tumor size, location, and staging according to the TNM classification of the UICC were registered. Tumors were classified as õT3 (T1 or T2) or as T3 or T4. For staging peritumoral lymph node metastases on WE-CT, two criteria of positivity were tested: N/ if at least one peritumoral node ¢5 mm in diameter was seen (reading A); N/ if at least one peritumoral node ¢5 mm or three peritumoral nodes õ5 mm were identified (reading B). Results: For the tumor staging, WE-CT showed a sensitivity of 90%, a specificity of 73%, a positive predictive value (PPV) of 90%, a negative predictive value (NPV) of 73%, and an accuracy of 85%. For TRUS, the results were sensitivity of 73%, specificity of 29%, PPV of 62%, NPV of 40%, and an accuracy of 39%. Concerning nodal staging with WE-CT, results were superior when reading A was used: sensitivity Å 84%, specificity Å 83%, PPV Å 73%, NPV Å 91%, and accuracy Å 84%. TRUS showed a sensitivity of 29%, specificity of 100%, PPV of 100%, NPV of 67%, and an accuracy of 71%.Correspondence to: F. Caseiro-Alves Conclusion: WE-CT is a reliable technique for the local staging of low colorectal tumors that can be superior to TRUS. For diagnosis of peritumoral metastatic lymph nodes on WE-CT, the 5-mm diameter cutoff value is the most appropriate size criterion.

Water enema CT examination of rectum cancer by reduced amount of water

“…We are aware of that, nevertheless feces always contains small bubbles of gas [7], it still can easily be misinterpreted as tumor [5], but we examined patients with diagnosed rectum cancer and the purpose of the examination was not the detection, but the staging of the tumor. Similarly to Caseiro-Alves et al [1] and Gazelle et al [3], we found that certain patients did not tolerate well the administration of water volume exceeding a certain level. To avoid patient discomfort and decrease risk of complication we decided to perform WE-CT examinations with a reduced dose (400 ± 500 ml) of water in those cases when the primary pathologic process was localized to the rectum.…”

“…Most authors proposed to perform a bowel-cleansing regimen prior to the WE-CT examination [2, 3, 5 ± 9], while some others did not apply it regularly [1,12]. The amount of water, introduced into the rectum during the examination was between 1000 and 2000 ml [1 ± 3, 5 ± 9].…”

“…CTcannot show the difference between a tumor confined to the mucosa and one involving the muscular structure of the rectum (T1 vs. T2), because it is not possible to distinguish the single layers composing the wall [2], and CT is not reliable for identifying T4 stage [1]. Hundt et al recently described a two-phase (arterial and venous) helical CT examination technique, owing to which layers of the intestinal wall could be differentiated.…”

“…The accuracy of CT examination may be significantly variable, depending on technical parameters of the examination (rectal distention, endoluminal and intravenous contrast material, smooth muscle relaxant, etc.) [1,4]. In the recent decade many authors described their experience with performing CT of the rectum with aqueous distention to improve visualization of the bowel wall.…”

“…In the recent decade many authors described their experience with performing CT of the rectum with aqueous distention to improve visualization of the bowel wall. The generally used dose of water enema, as described in these publications, is in the range of 1000 ± 2000 ml, however, it must be emphasized that several of these studies described the examination of the entire colon [3, 5 ± 9], while others referred to the optimal visualization of the rectum [1,2,10].…”